JP2008277003A - Nonaqueous electrolyte for secondary battery and nonaqueous electrolyte secondary battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte excellent in cycle. <P>SOLUTION: The nonaqueous electrolyte contains a nonaqueous solvent and an electrolyte and further contains a monofluorophosphate and/or difluorophospate, and a 0.001-10 mass% compound represented by a general formula (1) and/or a compound represented by a formula (2). [R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>, R<SP>4</SP>, R<SP>5</SP>, R<SP>6</SP>, and R<SP>7</SP>are organic groups or halogen atoms, and at least one of them is a base in which an atom directly bonding with X or Y is a hetero atom, the base may be included in R<SP>1</SP>to R<SP>7</SP>, and X and Y are atoms excluding a carbon atom]. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte for a secondary battery and a non-aqueous electrolyte secondary battery using the same, and more specifically, a non-aqueous electrolyte for a lithium secondary battery containing a specific component, and The present invention relates to a lithium secondary battery using the same.

  In recent years, with the miniaturization of electronic devices, the demand for higher capacity for secondary batteries has increased, and lithium secondary batteries with higher energy density than nickel-cadmium batteries and nickel-hydrogen batteries have attracted attention. Yes.

As an electrolyte of the lithium secondary battery, an electrolyte such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiCF ₃ (CF ₂ ) ₃ SO ₃ , Cyclic carbonates such as ethylene carbonate and propylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; cyclic esters such as γ-butyrolactone and γ-valerolactone; chain esters such as methyl acetate and methyl propionate A non-aqueous electrolyte solution dissolved in a non-aqueous solvent such as a liquid is used.

  In order to improve battery characteristics such as load characteristics, cycle characteristics, storage characteristics, and low temperature characteristics of such lithium secondary batteries, various studies have been made on non-aqueous solvents and electrolytes. For example, in Patent Document 1, by using an electrolytic solution containing a vinyl ethylene carbonate compound, it is possible to minimize the decomposition of the electrolytic solution, and to manufacture a battery having excellent storage characteristics and cycle characteristics. In No. 2, the recovery capacity after storage can be increased by using an electrolytic solution containing propane sultone.

However, when such a compound is contained, the effect of improving the storage characteristics and the cycle characteristics can be exhibited to some extent. However, since a high-resistance film is formed on the negative electrode side, the discharge load characteristics are particularly high. There has been a problem of lowering.
JP 2001-006729 A JP-A-10-050342

  This invention is made | formed in view of this background art, and is providing the nonaqueous electrolyte solution for secondary batteries excellent in cycling characteristics.

  As a result of intensive studies in view of the above problems, the present inventor maintains good cycle characteristics when a specific compound and “monofluorophosphate and / or difluorophosphate” are added to a non-aqueous electrolyte. The present invention has been found.

［Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４はそれぞれ独立して有機基若しくはハロゲン原子であり、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４のうち少なくとも１つはＸと直接結合する原子がヘテロ原子である基であり、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４には同じものが含まれていてもよい。Ｘは炭素原子以外の原子である。］

［Ｒ^５、Ｒ^６、Ｒ^７はそれぞれ独立して有機基若しくはハロゲン原子であり、Ｒ^５、Ｒ^６、Ｒ^７のうち少なくとも１つはＹと直接結合する原子がヘテロ原子である基であり、Ｒ^５、Ｒ^６、Ｒ^７には同じものが含まれていてもよい。Ｙは炭素原子以外の原子である。］ That is, the gist of the present invention is a non-aqueous electrolyte used in a non-aqueous electrolyte secondary battery comprising a negative electrode and a positive electrode capable of occluding and releasing ions, and a non-aqueous electrolyte, and the non-aqueous electrolyte is a non-aqueous electrolyte. A compound containing an electrolyte and a non-aqueous solvent, further containing a monofluorophosphate and / or a difluorophosphate, and represented by the general formula (1) and / or the general formula (2) The non-aqueous electrolyte for secondary batteries is characterized by containing 0.001% by mass to 10% by mass with respect to the total amount of the non-aqueous electrolyte.

[R ¹ , R ² , R ³ , and R ⁴ are each independently an organic group or a halogen atom, and at least one of R ¹ , R ² , R ³ , and R ⁴ is heterogeneous with an atom directly bonded to X It is a group which is an atom, and the same thing may be contained in R ¹ , R ² , R ³ and R ⁴ . X is an atom other than a carbon atom. ]

[R ⁵ , R ⁶ and R ⁷ are each independently an organic group or a halogen atom, and at least one of R ⁵ , R ⁶ and R ⁷ is a group in which an atom directly bonded to Y is a hetero atom. , R ⁵ , R ⁶ and R ⁷ may contain the same thing. Y is an atom other than a carbon atom. ]

［Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４はそれぞれ独立して有機基若しくはハロゲン原子であり、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４のうち少なくとも１つはＸと直接結合する原子がヘテロ原子である基であり、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４には同じものが含まれていてもよい。Ｘは炭素原子以外の原子である。］

［Ｒ^５、Ｒ^６、Ｒ^７はそれぞれ独立して有機基若しくはハロゲン原子であり、Ｒ^５、Ｒ^６、Ｒ^７のうち少なくとも１つはＹと直接結合する原子がヘテロ原子である基であり、Ｒ^５、Ｒ^６、Ｒ^７には同じものが含まれていてもよい。Ｙは炭素原子以外の原子である。］ The gist of the present invention is a non-aqueous electrolyte used in a non-aqueous electrolyte secondary battery comprising a negative electrode and a positive electrode capable of occluding and releasing ions, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is a non-aqueous electrolyte. , A non-aqueous electrolyte secondary containing a monofluorophosphate and / or a difluorophosphate and treating the compound represented by the general formula (1) and / or the general formula (2) with a positive electrode or a negative electrode It exists in the nonaqueous electrolyte solution for secondary batteries characterized by using for a battery.

[R ¹ , R ² , R ³ , and R ⁴ are each independently an organic group or a halogen atom, and at least one of R ¹ , R ² , R ³ , and R ⁴ is heterogeneous with an atom directly bonded to X It is a group which is an atom, and the same thing may be contained in R ¹ , R ² , R ³ and R ⁴ . X is an atom other than a carbon atom. ]

[R ⁵ , R ⁶ and R ⁷ are each independently an organic group or a halogen atom, and at least one of R ⁵ , R ⁶ and R ⁷ is a group in which an atom directly bonded to Y is a hetero atom. , R ⁵ , R ⁶ and R ⁷ may contain the same thing. Y is an atom other than a carbon atom. ]

  The gist of the present invention is a non-aqueous electrolyte secondary battery comprising at least a negative electrode and a positive electrode capable of occluding and releasing lithium ions, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is a non-aqueous electrolyte described above. It exists in the non-aqueous electrolyte secondary battery characterized by being an aqueous electrolyte.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte solution for secondary batteries excellent in cycling characteristics and the nonaqueous electrolyte solution secondary battery can be provided.

  Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is limited to these specific contents. However, various modifications can be made within the scope of the gist.

[1. Non-aqueous electrolyte]
The non-aqueous electrolyte solution of the present invention contains an electrolyte and a non-aqueous solvent that dissolves the electrolyte, in the same manner as a normal non-aqueous electrolyte solution.
<1-1. Electrolyte>
There is no restriction | limiting in the electrolyte contained in the non-aqueous electrolyte solution of this invention, The well-known thing used as an electrolyte can be arbitrarily employ | adopted and mixed in the target non-aqueous electrolyte secondary battery. In addition, when using the non-aqueous electrolyte solution of this invention for a lithium ion secondary battery, it is preferable to use lithium salt.

Specific examples of electrolytes include
LiClO ₄ ,
LiAsF ₆ ,
LiPF ₆ ,
Li ₂ CO ₃ ,
Inorganic lithium salts such as LiBF ₄ ;

LiCF ₃ SO ₃ ,
LiN (CF ₃ SO ₂ ) ₂ ,
LiN (C ₂ F ₅ SO ₂ ) ₂ ,
LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ),
LiC (CF ₃ SO ₂ ) ₃ ,
LiPF ₄ (CF ₃ ) ₂ ,
LiPF ₄ (C ₂ F ₅ ) ₂ ,
LiPF ₄ (CF ₃ SO ₂ ) ₂ ,
LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ ,
LiBF ₃ (CF ₃ ),
LiBF ₃ (C ₂ F ₅ ),
LiBF ₂ (CF ₃ ) ₂ ,
LiBF ₂ (C ₂ F ₅ ) ₂ ,
LiBF ₂ (CF ₃ SO ₂ ) ₂ ,
Fluorine-containing organic lithium salt such as LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ ;

Lithium bis (oxalato) borate,
Lithium tris (oxalato) phosphate,
Dicarboxylic acid complex lithium salts such as lithium difluorooxalatoborate;

KPF ₆ ,
NaPF ₆ ,
NaBF ₄ ,
Examples thereof include sodium salts or potassium salts such as CF ₃ SO ₃ Na.

Of these, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , and lithium bis (oxalato) borate are preferred, and in particular, LiPF ₆ or LiBF ₄ is preferred.

  One type of electrolyte may be used alone, or two or more types of electrolytes may be used in any combination and ratio. In particular, when two types of specific inorganic lithium salts are used in combination, or when an inorganic lithium salt and a fluorine-containing organic lithium salt are used in combination, gas generation during continuous charging is suppressed, or deterioration after high-temperature storage is suppressed. Therefore, it is preferable.

In particular, the combination and the LiPF ₆ and LiBF _4, and an inorganic lithium salt such as _{LiPF 6, LiBF 4, LiCF 3} SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) _2, etc. It is preferable to use in combination with a fluorine-containing organic lithium salt.

Furthermore, when LiPF ₆ and LiBF ₄ are used in combination, it is preferable that LiBF ₄ is contained at a ratio of usually 0.01% by mass or more and usually 20% by mass or less with respect to the entire electrolyte. LiBF ₄ has a low degree of dissociation, and if the ratio is too high, the resistance of the non-aqueous electrolyte may be increased.

On the other hand, when inorganic lithium salts such as LiPF ₆ and LiBF ₄ are used in combination with fluorine-containing organic lithium salts such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (C ₂ F ₅ SO ₂ ) ₂ The proportion of the inorganic lithium salt in the entire electrolyte is preferably in the range of usually 70% by mass or more and usually 99% by mass or less. In general, fluorine-containing organic lithium salts have a higher molecular weight than inorganic lithium salts. If the ratio is too high, the ratio of the non-aqueous solvent in the entire non-aqueous electrolyte may decrease and the resistance of the non-aqueous electrolyte may increase. .

  Further, the concentration of the lithium salt in the final composition of the non-aqueous electrolyte of the present invention is arbitrary as long as the effects of the present invention are not significantly impaired, but usually 0.5 mol / L or more, preferably 0.6 mol / L L or more, more preferably 0.8 mol / L or more, and usually 3 mol · / L or less, preferably 2 mol / L or less, more preferably 1.5 mol / L or less.

  If this concentration is too low, the electrical conductivity of the non-aqueous electrolyte may be insufficient. If the concentration is too high, the electrical conductivity will decrease due to an increase in viscosity, and the non-aqueous electrolyte of the present invention will be used. The performance of the existing non-aqueous electrolyte secondary battery may deteriorate.

In particular, when the non-aqueous solvent of the non-aqueous electrolyte is mainly composed of a carbonate compound such as alkylene carbonate or dialkyl carbonate, LiPF ₆ may be used alone, but when used together with LiBF ₄ , capacity deterioration due to continuous charging is suppressed. This is preferable. When these are used in combination, the molar ratio of LiBF _{4 to} LiPF ₆ is usually 0.005 or more, preferably 0.01 or more, particularly preferably 0.05 or more, and usually 0.4 or less, preferably 0.2. It is as follows. If this molar ratio is too large, battery characteristics after high-temperature storage tend to be reduced. Conversely, if it is too small, it is difficult to obtain the effect of suppressing gas generation and capacity deterioration during continuous charging.

When the non-aqueous solvent of the non-aqueous electrolyte solution contains 50% by volume or more of a cyclic carboxylic acid ester compound such as γ-butyrolactone and γ-valerolactone, LiBF ₄ is 50 mol% or more of the entire first lithium salt. Preferably.

［Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４はそれぞれ独立して有機基若しくはハロゲン原子であり、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４のうち少なくとも１つはＸと直接結合する原子がヘテロ原子である基であり、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４には同じものが含まれていてもよい。Ｘは炭素原子以外の原子である。］ <1-2. Compound represented by general formula (1)>
The compound represented by the general formula (1) is the following compound.

[R ¹ , R ² , R ³ , and R ⁴ are each independently an organic group or a halogen atom, and at least one of R ¹ , R ² , R ³ , and R ⁴ is heterogeneous with an atom directly bonded to X It is a group which is an atom, and the same thing may be contained in R ¹ , R ² , R ³ and R ⁴ . X is an atom other than a carbon atom. ]

  In the general formula (1), X is not particularly limited as long as it is an atom other than a carbon atom, but is preferably a silicon atom or a titanium atom in view of stability in a nonaqueous electrolytic solution.

R ¹ , R ² , R ³ and R ⁴ each independently represents an organic group or a halogen atom. The organic group is not particularly limited, and the “organic group” in which the atom bonded to X is a carbon atom includes an optionally substituted alkyl group, alkenyl group, alkynyl group and the like. Is mentioned. As for carbon number of these organic groups, 1-10 are more preferable.

  Specifically, as the alkyl group, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, isopropyl group, isobutyl group, 2-methylpropyl group, 1-methylbutyl group , 2-methylbutyl group, 3-methylbutyl group, 1,2-dimethylpropyl group, neopentyl group and the like, and examples of the alkenyl group include vinyl group, allyl group, isopropenyl group, 1-propenyl group, butenyl group, butadienyl. Group, pentenyl group, and the like. Examples of the alkynyl group include ethynyl group, 1-propionyl group, 1-butynyl group, 1-pentynyl group, 2-propionyl group, 2-butynyl group, and 3-butynyl group. .

  The substituent for these groups is not particularly limited, and examples thereof include a fluorine atom, a chlorine atom, a methacryloxy group, a mercapto group, an alkylamino group, an arylamino group, a glycidoxy group, a benzoyloxy group, and an acetyloxy group.

  Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a chlorine atom or a fluorine atom is particularly preferable.

In addition, at least one of R ¹ , R ² , R ³ , and R ⁴ is a group in which an atom that forms a direct bond with X is a heteroatom. The hetero atom is not particularly limited as long as it is an atom other than a carbon atom, but B, N, O, P, S or a halogen atom is highly reactive, and as a result, it can give an excellent cycle characteristic. Is preferable. Among these, a halogen atom, an oxygen atom, or a nitrogen atom is particularly preferable.

  Among the “groups in which the atom directly bonded to X is a heteroatom”, when the heteroatom is an oxygen atom, specifically, for example, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, Examples thereof include alkoxy groups such as propoxy group, 1-methylpropoxy group, 2-methylpropoxy group and tert-butoxy group; benzoyloxy group and acetyloxy group. Moreover, when a hetero atom is a nitrogen atom, specifically, a dimethylamino group, a diethylamino group, an ethylmethylamino group etc. are mentioned, for example. Of these, alkoxy groups such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group are more preferable for the same reason as described above.

  The “group in which the atom directly bonded to X is a heteroatom” may be a halogen atom. In this case, the halogen atom is preferably a fluorine atom, a chlorine atom, a bromine atom or an iodine atom, and a chlorine atom is more preferred for the same reason as described above.

  The “group in which the atom directly bonded to X is a heteroatom” may have a substituent, but an alkoxy group or a chlorine atom that does not have is particularly preferred for the same reason as above.

In the compound represented by the general formula (1), at least one of R ¹ , R ² , R ³ , and R ⁴ is a group in which an atom directly bonded to X is a heteroatom, but R ¹ , R Preferably, at least two of ² , R ³ and R ⁴ are groups in which the atom directly bonded to X is a heteroatom, and two or three of R ¹ , R ² , R ³ and R ⁴ are , “A group in which the atom directly bonded to X is a heteroatom” is particularly preferable. In this case, it is possible to obtain a non-aqueous electrolyte for a secondary battery having excellent cycle characteristics.

The reason for this is that when the electrode and the “group in which the atom directly bonded to X is a heteroatom” interact, if there are too few “groups in which the atom directly bonded to X is a heteroatom”, these are In particular, when all ^four of R ¹ , R ² , R ³ , and R ⁴ are “groups in which an atom directly bonded to X is a heteroatom”, non-aqueous electrolysis Since there is no group that interacts with the liquid, the electrode may not be sufficiently stabilized.

In General formula (1), the same thing may be contained in R < ¹ >, R < ² >, R < ³ >, R < ⁴ >.

  Specific examples of the compound represented by the general formula (1) include, for example, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxy-ethoxy) silane, and 3-methacryloxypropyltriethoxysilane. 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltrimethoxysilane, 2-methacryloxypropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropyl Trimethoxysilane, N- (2-aminoethyl) -γ aminopropyltrimethoxysilane, N- (2-aminoethyl) -γ aminopropyltriethoxysilane, N- (2-aminoethyl) -γ aminopropylmethyldi Toxisilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, (2-n-butoxycarbonylbenzoyloxy) tributoxy titanium, diisopropoxy titanium diisostearate, titanium stearate and the like. These may be used alone or in combination of two or more.

  When X is titanium, an organic titanium chelate compound in which a chelate compound such as acetylacetone or alkylacetoacetate is coordinated to titanium is also preferable. These may be used alone or in combination of two or more.

［Ｒ^５、Ｒ^６、Ｒ^７はそれぞれ独立して有機基若しくはハロゲン原子であり、Ｒ^５、Ｒ^６、Ｒ^７のうち少なくとも１つはＹと直接結合する原子がヘテロ原子（ハロゲン原子を含む）である基であり、Ｒ^５、Ｒ^６、Ｒ^７には同じものが含まれていてもよい。Ｙは炭素原子以外の原子である。］ <1-3. Compound represented by general formula (2)>
The compound represented by the general formula (2) is the following compound.

[R ⁵ , R ⁶ and R ⁷ are each independently an organic group or a halogen atom, and at least one of R ⁵ , R ⁶ and R ⁷ is a hetero atom (including a halogen atom) directly bonded to Y And R ⁵ , R ⁶ and R ⁷ may contain the same group. Y is an atom other than a carbon atom. ]

In the general formula (2), R ⁵ , R ⁶ , and R ⁷ are each independently an organic group or a halogen atom, but the description in the general formula (1) is not changed for the organic group or the halogen atom. Applied. In addition, at least one of R ⁵ , R ⁶ , and R ⁷ is a group in which an atom directly bonded to Y is a heteroatom. Here, “heteroatom” and “atom directly bonded to Y are heteroatoms. The description in the general formula (1) is also applied to the “group”.

  As for Y in the general formula (2), an aluminum atom is preferable in view of stability in the electrolytic solution and the like.

At least one of R ⁵ , R ⁶ , and R ⁷ is a “group in which the atom directly bonded to Y is a heteroatom”, but just two of R ⁵ , R ⁶ , and R ⁷ are directly connected to Y It is preferred that the atom forming the bond is a heteroatom. In this case, it is possible to obtain a non-aqueous electrolyte for a secondary battery having excellent cycle characteristics.

The reason for this is that among the electrodes R ⁵ , R ⁶ and R ⁷ , when the electrode and the “group in which the atom directly bonded to Y is a heteroatom” interact, “the atom directly bonded to Y is a heteroatom When there are too few “groups”, the interaction between them may be too small, and all ^three of R ¹ , R ² , and R ³ are “the atoms directly bonded to Y are heteroatoms” In the case of “base”, there is no group that interacts with the non-aqueous electrolyte solution, and thus the electrode may not be sufficiently stabilized.

In the general formula (2) ^may include the same ones in ^{R 5, R 6, R 7} .

  Specific examples of the compound represented by the general formula (2) include acetylacetonatodiisopropylaluminum. These may be used alone or in combination of two or more.

  Organic aluminum chelate compounds in which other chelate compounds such as alkyl acetoacetates are coordinated with aluminum in addition to the acetylacetone of the above specific examples. These may be used alone or in combination of two or more.

<1-4. Content of Compound Represented by General Formula (1) and Compound Represented by General Formula (2)>
The compound represented by the general formula (1) and the compound represented by the general formula (2) are included in a total amount of 0.001% by mass to 10% by mass with respect to the whole non-aqueous electrolyte solution. It is particularly preferable that it is contained in a proportion of 0.01% to 5% by mass. If the amount of the non-aqueous electrolyte is too small, the effect cannot be sufficiently exhibited and a non-aqueous electrolyte for a secondary battery having excellent cycle characteristics may not be obtained. In some cases, the capacity of the battery may be impaired by their own reaction.

  The compounds represented by the general formula (1) or the general formula (2) are non-aqueous based on the total amount of the non-aqueous electrolytic solution based on 0.001% by mass to 10% by mass with respect to the entire non-aqueous electrolyte. It is preferable to prepare an electrolytic solution, and it is particularly preferable to prepare by mixing a mass corresponding to 0.01% by mass to 5% by mass.

<1-5. Non-aqueous solvent>
The non-aqueous solvent contained in the non-aqueous electrolyte of the present invention is not particularly limited as long as it is a non-aqueous solvent that does not adversely affect battery characteristics when used as a battery. It is preferable that it is 1 or more types in the non-aqueous solvent used for the non-aqueous electrolyte solution hung up below.

As an example of the non-aqueous solvent used, for example,
Chain or cyclic carbonate,
Chain or cyclic carboxylic acid ester,
Chain and cyclic ethers,
And sulfur-containing organic solvents.

Moreover, although there is no restriction | limiting in the kind of chain carbonate, Dialkyl carbonate is preferable and carbon number of the alkyl group which comprises is each preferable 1-5, Most preferably, it is 1-4. As a specific example, for example,
Dimethyl carbonate,
Ethyl methyl carbonate,
Diethyl carbonate,
Methyl-n-propyl carbonate,
Ethyl-n-propyl carbonate,
Examples include di-n-propyl carbonate.

  Among these, dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate is preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

Although there is no restriction | limiting in the kind of cyclic carbonate, As for carbon number of the alkylene group which comprises a cyclic carbonate, 2-6 are preferable, Most preferably, it is 2-4. Specifically, for example,
Ethylene carbonate,
Propylene carbonate,
Examples include butylene carbonate (2-ethylethylene carbonate, cis and trans 2,3-dimethylethylene carbonate).

  Among these, ethylene carbonate or propylene carbonate is preferable in that various characteristics in the non-aqueous electrolyte secondary battery are good.

Furthermore, the type of the chain carboxylic acid ester is not limited, but as a specific example, for example,
Methyl acetate,
Ethyl acetate,
Acetic acid-n-propyl,
Acetic acid-iso-propyl,
N-butyl acetate,
Acetate-iso-butyl acetate,
Acetate-tert-butyl acetate,
Methyl propionate,
Ethyl propionate,
N-propyl propionate,
Propionic acid-iso-propyl,
Propionate-n-butyl,
Propionate-iso-butyl,
And propionic acid-tert-butyl.

  Among these, ethyl acetate, methyl propionate, or ethyl propionate is preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

In addition, the type of cyclic carboxylic acid ester is not limited, but as an example of what is usually used,
γ-butyrolactone,
γ-valerolactone,
δ-valerolactone and the like can be mentioned.

  Among these, γ-butyrolactone is preferable because of its good industrial availability and various characteristics in non-aqueous electrolyte secondary batteries.

Furthermore, there is no restriction | limiting also in the kind of chain ether, As a specific example, for example,
Dimethoxymethane,
Dimethoxyethane,
Diethoxymethane,
Diethoxyethane,
Ethoxymethoxymethane,
Examples include ethoxymethoxyethane.

  Among these, dimethoxyethane and diethoxyethane are preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

In addition, the type of cyclic ether is not limited, and specific examples include, for example,
Tetrahydrofuran,
2-methyltetrahydrofuran,
Tetrahydropyran etc. are mentioned.

Furthermore, the type of the phosphorus-containing organic solvent is not particularly limited, and specific examples include, for example,
Trimethyl phosphate,
Triethyl phosphate,
Phosphate esters such as triphenyl phosphate;
Trimethyl phosphite,
Triethyl phosphite,
Phosphites such as triphenyl phosphite;
Trimethylphosphine oxide,
Triethylphosphine oxide,
And phosphine oxides such as triphenylphosphine oxide.

In addition, there is no particular limitation on the type of the sulfur-containing organic solvent, and as a specific example, for example,
Ethylene sulfite,
1,3-propane sultone,
1,4-butane sultone,
Methyl methanesulfonate,
Busulfan,
Sulfolane,
Sulfolene,
Dimethyl sulfone,
Diphenylsulfone,
Methylphenylsulfone,
Dibutyl disulfide,
Dicyclohexyl disulfide,
Tetramethylthiuram monosulfide,
N, N-dimethylmethanesulfonamide,
N, N-diethylmethanesulfonamide and the like can be mentioned.

  Among these, a chain or cyclic carbonate or a chain or cyclic carboxylic acid ester is preferable in terms of various characteristics in the non-aqueous electrolyte secondary battery, and among them, ethylene carbonate, propylene carbonate, dimethyl carbonate, More preferred is ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl propionate, ethyl propionate or γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl propionate or γ- Butyrolactone is more preferred

  Among the non-aqueous solvents described above, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl propionate, and ethyl propionate are most preferable.

  These may be used alone or in combination of two or more, but it is preferable to use in combination of two or more. For example, it is particularly preferable to use a high dielectric constant solvent of cyclic carbonates in combination with a low viscosity solvent such as chain carbonates or chain esters.

  One preferred combination of non-aqueous solvents is a combination mainly composed of cyclic carbonates and chain carbonates. Among them, the total of the cyclic carbonates and the chain carbonates in the non-aqueous solvent is 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more, and the cyclic carbonates and the chain carbonates. The volume of cyclic carbonates with respect to the total with carbonates is 5% or more, preferably 10% or more, more preferably 15% or more, and usually 50% or less, preferably 35% or less, more preferably 30% or less. It is. Use of a combination of these non-aqueous solvents is preferable because the balance between cycle characteristics and high-temperature storage characteristics (particularly, remaining capacity and high-load discharge capacity after high-temperature storage) of a battery produced using the non-aqueous solvent is improved.

  Specific examples of preferred combinations of cyclic carbonates and chain carbonates include, for example, ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate and diethyl carbonate, and ethylene carbonate. Examples thereof include dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

  A combination in which propylene carbonate is further added to the combination of these ethylene carbonates and chain carbonates is also a preferable combination. In the case of containing propylene carbonate, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, particularly preferably 95: 5 to 50:50. Furthermore, the amount of propylene carbonate in the whole non-aqueous solvent is 0.1% by volume or more, preferably 1% by volume, more preferably 2% by volume or more, usually 10% by volume or less, preferably 8% by volume or less, more preferably Is preferably 5% by volume or less because the discharge characteristics are further excellent while maintaining the combination characteristics of ethylene carbonate and chain carbonates.

  Among these, those containing asymmetric chain carbonates are more preferable, especially ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl. Those containing ethylene carbonate such as methyl carbonate, symmetric chain carbonates and asymmetric chain carbonates, or further containing propylene carbonate are preferred because of a good balance between cycle characteristics and discharge characteristics. Among these, those in which the asymmetric chain carbonate is ethyl methyl carbonate are preferable, and the number of carbon atoms of the alkyl group constituting the dialkyl carbonate is preferably 1 or 2.

  Another example of a preferable mixed solvent is one containing a chain ester. In particular, those containing a chain ester in the mixed solvent of cyclic carbonates and chain carbonates are preferable from the viewpoint of improving the discharge characteristics of the battery. Examples of the chain esters include methyl acetate, ethyl acetate, and propionic acid. Methyl is particularly preferred. The capacity of the chain ester in the non-aqueous solvent is usually 5% or more, preferably 8% or more, more preferably 15% or more, usually 50% or less, preferably 35% or less, more preferably 30% or less, More preferably, it is 25% or less.

  Examples of other preferable non-aqueous solvents include one organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate and butylene carbonate, γ-butyrolactone and γ-valerolactone, or two or more selected from the group A mixed solvent composed of an organic solvent occupies 60% by volume or more of the whole. Such a mixed solvent preferably has a flash point of 50 ° C. or higher, and particularly preferably 70 ° C. or higher. A non-aqueous electrolyte using this solvent reduces evaporation of the solvent and leakage even when used at high temperatures. Among them, the total of ethylene carbonate and γ-butyrolactone in the whole non-aqueous solvent is 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate and γ-butyrolactone is 5:95 to 45%. : 55, or the total of ethylene carbonate and propylene carbonate is 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate to propylene carbonate is 30:70 to 80:20. In general, the balance between cycle characteristics and discharge load characteristics is improved.

<1-6. Monofluorophosphate, Difluorophosphate>
The nonaqueous electrolytic solution of the present invention contains a monofluorophosphate and / or a difluorophosphate as an essential component. The “monofluorophosphate and / or difluorophosphate” used in the present invention is classified into its kind as long as it is formed from one or more monofluorophosphate ions and / or difluorophosphate ions and cations. Although there is no particular limitation, since the non-aqueous electrolyte to be finally produced needs to be usable as the electrolyte of the non-aqueous electrolyte secondary battery to be used, it needs to be selected in view of this. is there.

  Therefore, the monofluorophosphate and difluorophosphate in the present invention are selected from one or more monofluorophosphate ions, difluorophosphate ions, and groups 1, 2 and 13 of the periodic table. And a salt with one or more metal ions (hereinafter referred to as “specific metal” where appropriate) and / or a salt with a quaternary onium. Monofluorophosphate and / or difluorophosphate may be used alone or in any combination of two or more.

<1-6-1. Monofluorophosphoric acid metal salt, difluorophosphoric acid metal salt>
First, monofluorophosphate and difluorophosphate in the present invention are monofluorophosphate ions, salts of difluorophosphate ions and specific metal ions (hereinafter referred to as “monofluorophosphate metal salts” and “difluoro, respectively”, respectively). The case of “metal phosphate” may be abbreviated).

  Among the specific metals used in the monofluorophosphate metal salt and difluorophosphate metal salt in the present invention, specific examples of the Group 1 metal in the periodic table include lithium, sodium, potassium, cesium, and the like. Among these, lithium and sodium are preferable, and lithium is particularly preferable.

  Specific examples of Group 2 metals in the periodic table include magnesium, calcium, strontium, barium, and the like. Among these, magnesium and calcium are preferable, and magnesium is particularly preferable.

  Specific examples of the Group 13 metal in the periodic table include aluminum, gallium, indium, and thallium. Of these, aluminum and gallium are preferable, and aluminum is particularly preferable.

  The number of atoms of these specific metals that the monofluorophosphoric acid metal salt and difluorophosphoric acid metal salt in the present invention have in one molecule is not limited and may be only one atom or two or more atoms. Also good.

  When the monofluorophosphate metal salt and difluorophosphate metal salt in the present invention contain two or more specific metals in one molecule, the types of these specific metal atoms may be the same or different from each other. Also good. Moreover, you may have 1 or 2 or more metal atoms other than a specific metal other than a specific metal.

Specific examples of the monofluorophosphoric acid metal salt and the difluorophosphoric acid metal salt include Li ₂ PO ₃ F, Na ₂ PO ₃ F, MgPO ₃ F, CaPO ₃ F, Al ₂ (PO ₃ F) ₃ , and Ga ₂ ( PO ₃ F) ₃ , LiPO ₂ F ₂ , NaPO ₂ F ₂ , Mg (PO ₂ F ₂ ) ₂ , Ca (PO ₂ F ₂ ) ₂ , Al (PO ₂ F ₂ ) ₃ , Ga (PO ₂ F ₂ ) ₃ etc. are mentioned. Among them, Li ₂ PO ₃ F, LiPO ₂ F ₂ , NaPO ₂ F ₂ , Mg (PO ₂ F ₂ ) _{2 and the} like are preferable.

<1-6-2. Monofluorophosphoric acid quaternary onium salt, difluorophosphoric acid quaternary onium salt>
Next, the monofluorophosphate and difluorophosphate in the present invention are monofluorophosphate ions, difluorophosphate ions and quaternary onium salts (hereinafter referred to as “monofluorophosphate quaternary onium salts”, The case of “difluorophosphoric acid quaternary onium salt” may be abbreviated).

The quaternary onium used in the monofluorophosphoric acid quaternary onium salt and difluorophosphoric acid quaternary onium salt in the present invention is usually a cation, specifically, a cation represented by the following general formula (3). It is done.

In the general formula (3), R ^{1 to} R ⁴ each independently represents a hydrocarbon group. The kind of hydrocarbon group is not limited. That is, it may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, or may be a hydrocarbon group to which those groups are bonded. In the case of an aliphatic hydrocarbon group, it may be a chain or a ring, and may have a structure in which a chain and a ring are combined. In the case of a chain hydrocarbon group, it may be linear or branched. Moreover, it may be a saturated hydrocarbon group and may have an unsaturated bond.

Specific examples of the hydrocarbon group for R ^{1 to} R ⁴ include an alkyl group, a cycloalkyl group, an aryl group, and an aralkyl group.

Specific examples of the alkyl group include
Methyl group,
Ethyl group,
1-propyl group,
1-methylethyl group,
1-butyl group,
1-methylpropyl group,
2-methylpropyl group,
1,1-dimethylethyl group and the like can be mentioned.

  Of these, a methyl group, an ethyl group, a 1-propyl group, a 1-butyl group and the like are preferable.

Specific examples of the cycloalkyl group include, for example,
A cyclopentyl group,
2-methylcyclopentyl group,
3-methylcyclopentyl group,
2,2-dimethylcyclopentyl group,
2,3-dimethylcyclopentyl group,
2,4-dimethylcyclopentyl group,
2,5-dimethylcyclopentyl group,
3,3-dimethylcyclopentyl group,
3,4-dimethylcyclopentyl group,
2-ethylcyclopentyl group,
3-ethylcyclopentyl group,
A cyclohexyl group,
2-methylcyclohexyl group,
3-methylcyclohexyl group,
4-methylcyclohexyl group,
2,2-dimethylcyclohexyl group,
2,3-dimethylcyclohexyl group,
2,4-dimethylcyclohexyl group,
2,5-dimethylcyclohexyl group,
2,6-dimethylcyclohexyl group,
3,4-dimethylcyclohexyl group,
3,5-dimethylcyclohexyl group,
2-ethylcyclohexyl group,
3-ethylcyclohexyl group,
4-ethylcyclohexyl group,
A bicyclo [3,2,1] oct-1-yl group,
And bicyclo [3,2,1] oct-2-yl group.

  Among these, a cyclopentyl group, a 2-methylcyclopentyl group, a 3-methylcyclopentyl group, a cyclohexyl group, a 2-methylcyclohexyl group, a 3-methylcyclohexyl group, and a 4-methylcyclohexyl group are preferable.

Specific examples of the aryl group include, for example,
Phenyl group,
2-methylphenyl group,
3-methylphenyl group,
4-methylphenyl group,
2,3-dimethylphenyl group and the like can be mentioned.
Of these, a phenyl group is preferred.

Specific examples of aralkyl groups include
Phenylmethyl group,
1-phenylethyl group,
2-phenylethyl group,
Diphenylmethyl group,
And a triphenylmethyl group.
Of these, a phenylmethyl group and a 2-phenylethyl group are preferable.

The hydrocarbon group for R ^{1 to} R ⁴ may be substituted with one or more substituents. The type of the substituent is not limited as long as the effect in the present invention is not significantly impaired, and examples include a halogen atom, a hydroxyl group, an amino group, a nitro group, a cyano group, a carboxyl group, an ether group, and an aldehyde group. It is done. In the case where the hydrocarbon group of R ¹ to R ⁴ have two or more substituents, these substituents may be the same or may be different from one another.

The hydrocarbon groups of R ^{1 to} R ⁴ may be the same as or different from each other when any two or more are compared. When the hydrocarbon groups of R ^{1 to} R ⁴ have a substituent, the substituted hydrocarbon groups including those substituents may be the same as or different from each other. Furthermore, arbitrary two or more of the hydrocarbon groups of R ^{1 to} R ⁴ may be bonded to each other to form a cyclic structure.

The carbon number of the hydrocarbon group of R ^{1 to} R ⁴ is usually 1 or more, and usually 20 or less, preferably 10 or less, more preferably 5 or less. When it is too large, the number of moles per weight decreases, and various effects tend to be reduced. In the case where the hydrocarbon group of R ¹ to R ⁴ has a substituent, the carbon number of the substituted hydrocarbon group, including the substituents thereof are intended to satisfy the above range.

  In the general formula (3), Q represents an atom belonging to Group 15 of the periodic table. Among these, a nitrogen atom or a phosphorus atom is preferable.

  From the above, preferable examples of the quaternary onium represented by the general formula (3) include aliphatic chain quaternary salts, aliphatic cyclic ammoniums, aliphatic cyclic phosphoniums, nitrogen-containing heterocyclic aromatic cations, and the like. Can be mentioned.

  As the aliphatic chain quaternary salt, tetraalkylammonium, tetraalkylphosphonium, and the like are particularly preferable.

Specific examples of tetraalkylammonium include, for example,
Tetramethylammonium,
Ethyltrimethylammonium,
Diethyldimethylammonium,
Triethylmethylammonium,
Tetraethylammonium,
And tetra-n-butylammonium.

Specific examples of tetraalkylphosphonium include, for example,
Tetramethylphosphonium,
Ethyl trimethylphosphonium,
Diethyldimethylphosphonium,
Triethylmethylphosphonium,
Tetraethylphosphonium,
Examples include tetra-n-butylphosphonium.

  As the aliphatic cyclic ammonium, pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperaziniums, piperidiniums and the like are particularly preferable.

Specific examples of pyrrolidiniums include, for example,
N, N-dimethylpyrrolidinium,
N-ethyl-N-methylpyrrolidinium,
N, N-diethylpyrrolidinium and the like can be mentioned.

Specific examples of morpholiniums include, for example,
N, N-dimethylmorpholinium,
N-ethyl-N-methylmorpholinium,
N, N-diethylmorpholinium and the like can be mentioned.

As specific examples of imidazolinium, for example,
N, N′-dimethylimidazolinium,
N-ethyl-N′-methylimidazolinium,
N, N′-diethylimidazolinium,
1,2,3-trimethylimidazolinium and the like.

Specific examples of tetrahydropyrimidiniums include, for example:
N, N′-dimethyltetrahydropyrimidinium,
N-ethyl-N′-methyltetrahydropyrimidinium,
N, N′-diethyltetrahydropyrimidinium,
1,2,3-trimethyltetrahydropyrimidinium and the like.

Specific examples of piperaziniums include, for example,
N, N, N ′, N′-tetramethylpiperazinium,
N-ethyl-N, N ′, N′-trimethylpiperazinium,
N, N-diethyl-N ′, N′-dimethylpiperazinium,
N, N, N′-triethyl-N′-methylpiperazinium,
N, N, N ′, N′-tetraethylpiperazinium and the like can be mentioned.

Specific examples of piperidiniums include, for example,
N, N-dimethylpiperidinium,
N-ethyl-N-methylpiperidinium,
N, N-diethylpiperidinium and the like can be mentioned.

  As the nitrogen-containing heterocyclic aromatic cation, pyridiniums, imidazoliums and the like are particularly preferable.

As specific examples of pyridiniums, for example,
N-methylpyridinium,
N-ethylpyridinium,
1,2-dimethylpyrimidinium,
1,3-dimethylpyrimidinium,
1,4-dimethylpyrimidinium,
Examples include 1-ethyl-2-methylpyrimidinium.

Specific examples of imidazoliums include, for example,
N, N′-dimethylimidazolium,
N-ethyl-N′-methylimidazolium,
N, N′-diethylimidazolium,
1,2,3-trimethylimidazolium and the like can be mentioned.

  That is, preferred examples of the monofluorophosphate quaternary onium salt and the difluorophosphate quaternary onium salt in the present invention are salts of the quaternary oniums exemplified above with monofluorophosphate ions and / or difluorophosphate ions. become.

<1-6-3. Content, detection (origin of content), technical scope, etc.>
In the non-aqueous electrolyte solution of the present invention, only one type of monofluorophosphate or difluorophosphate may be used, and two or more types of monofluorophosphate and / or difluorophosphate may be combined in any combination. However, from the viewpoint of efficiently operating the non-aqueous electrolyte secondary battery, it is preferable to use one type of monofluorophosphate or difluorophosphate.

  Moreover, there is no restriction | limiting in the molecular weight of a monofluorophosphate and a difluorophosphate, Although it is arbitrary unless the effect of this invention is impaired remarkably, Usually, it is 100 or more. Moreover, although there is no restriction | limiting in particular in an upper limit, In view of the reactivity of this reaction, 1000 or less normally, Preferably 500 or less is practical and preferable.

  Monofluorophosphoric acid salt and difluorophosphoric acid salt are usually used in one kind, but when it is preferable to use a mixture of two or more kinds of salts when used as a non-aqueous electrolyte, monofluorophosphoric acid is used. A mixture of two or more of acid salts and difluorophosphoric acid salts may be used. Moreover, there is no restriction | limiting in particular also in the manufacturing method of a monofluorophosphate and a difluorophosphate, It is possible to select and manufacture a well-known method arbitrarily.

  The ratio of these monofluorophosphates and difluorophosphates in the non-aqueous electrolyte solution is essential to be 10 ppm or more (0.001 mass% or more) in total with respect to the total non-aqueous electrolyte solution, preferably It is 0.01 mass% or more, More preferably, it is 0.05 mass% or more, More preferably, it is 0.1 mass% or more. The upper limit is a total, preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. If the concentrations of monofluorophosphate and difluorophosphate are too low, it may be difficult to improve the discharge load characteristics, while if the concentration is too high, the charge / discharge efficiency may be reduced.

  When the monofluorophosphate and difluorophosphate are actually used as a non-aqueous electrolyte for the preparation of a non-aqueous electrolyte secondary battery, even if the battery is disassembled and the non-aqueous electrolyte is taken out again, The content is often significantly reduced. Accordingly, it is considered that the present invention includes those in which at least one monofluorophosphate and / or difluorophosphate can be detected even in a small amount from the non-aqueous electrolyte extracted from the battery. In addition, when monofluorophosphate and difluorophosphate are actually used as a non-aqueous electrolyte for the production of a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte obtained by disassembling the battery and taking it out again is monofluoro electrolyte. Even when the phosphate and / or difluorophosphate is not contained, it is often detected on the positive electrode, the negative electrode or the separator, which are other components of the non-aqueous electrolyte secondary battery. Accordingly, the present invention also includes a case where at least one monofluorophosphate and / or difluorophosphate is detected from at least one component of the positive electrode, the negative electrode, and the separator.

  In addition, the present invention includes a case where monofluorophosphate and / or difluorophosphate is contained in the nonaqueous electrolytic solution and used in at least one constituent member of the positive electrode, the negative electrode, and the separator. Is considered.

  On the other hand, the monofluorophosphate and / or difluorophosphate may be previously contained in the positive electrode of the nonaqueous electrolyte secondary battery to be produced or on the surface of the positive electrode. In this case, a part or all of the monofluorophosphate and difluorophosphate contained in advance is expected to be dissolved in the non-aqueous electrolyte and to exhibit a function, and is considered to be included in the present invention. .

  There are no particular limitations on the means for pre-contained in the positive electrode or on the surface of the positive electrode, but specific examples include dissolving monofluorophosphate and / or difluorophosphate in a slurry to be prepared at the time of preparing the positive electrode, which will be described later. Or, after applying or impregnating a solution prepared by dissolving monofluorophosphate and / or difluorophosphate in an arbitrary non-aqueous solvent in advance to the positive electrode already prepared, the used solvent is dried. The method of making it contain by removing is mentioned.

  Further, when a non-aqueous electrolyte secondary battery is actually produced, the non-aqueous electrolyte containing at least one monofluorophosphate and / or difluorophosphate may be contained in the positive electrode or on the positive electrode surface. . When producing a non-aqueous electrolyte secondary battery, since the non-aqueous electrolyte is impregnated in the positive electrode, monofluorophosphate and difluorophosphate are often contained in the positive electrode or on the surface of the positive electrode. Therefore, what can detect at least monofluorophosphate and / or difluorophosphate from the positive electrode collected when the battery is disassembled is considered to be included in the present invention.

  Moreover, the monofluorophosphate and the difluorophosphate may be previously contained in the negative electrode or the surface of the negative electrode of the produced nonaqueous electrolyte secondary battery. In this case, it is expected that a part or all of the monofluorophosphate and / or difluorophosphate contained in advance is dissolved in the non-aqueous electrolyte and expresses the function, and is included in the present invention. It is regarded. There are no particular restrictions on the means for inclusion in the negative electrode or the surface of the negative electrode in advance, but as a specific example, monofluorophosphate and difluorophosphate are dissolved in a slurry to be prepared at the time of preparing the negative electrode, which will be described later. Or, after applying or impregnating a solution prepared by dissolving monofluorophosphate and difluorophosphate in an arbitrary non-aqueous solvent to the negative electrode already prepared, the used solvent is dried and removed. The method of making it contain etc. is mentioned.

  Further, when a non-aqueous electrolyte secondary battery is actually produced, it may be contained in the negative electrode or on the negative electrode surface from a non-aqueous electrolyte containing at least one monofluorophosphate and difluorophosphate. When producing a secondary battery, since the nonaqueous electrolyte is impregnated in the negative electrode, monofluorophosphate and difluorophosphate are often contained in the negative electrode or on the negative electrode surface. Therefore, what can detect at least monofluorophosphate and difluorophosphate from the negative electrode collected when the battery is disassembled is considered to be included in the present invention.

  Furthermore, the monofluorophosphate and / or difluorophosphate may be preliminarily contained in the separator of the non-aqueous electrolyte secondary battery to be produced or on the surface of the separator. In this case, a part or all of the monofluorophosphate and difluorophosphate contained in advance is expected to be dissolved in the non-aqueous electrolyte and to exhibit a function, and is considered to be included in the present invention. . The means for containing in the separator or on the surface of the separator in advance is not particularly limited. As a specific example, a monofluorophosphate and a difluorophosphate are mixed at the time of producing the separator, or a non-aqueous electrolyte solution is used. After applying or impregnating a solution prepared by pre-dissolving monofluorophosphate and difluorophosphate in any non-aqueous solvent to the separator before making the secondary battery, the used solvent is dried and removed. The method of making it contain by doing is mentioned.

  Further, when a non-aqueous electrolyte secondary battery is actually produced, the non-aqueous electrolyte containing monofluorophosphate and / or difluorophosphate may be contained in the separator or on the separator surface. When producing a non-aqueous electrolyte secondary battery, since the separator is impregnated with the non-aqueous electrolyte, monofluorophosphate and difluorophosphate are often contained in the separator or on the separator surface. Therefore, what can detect at least monofluorophosphate and difluorophosphate from the separator collected when the battery is disassembled is considered to be included in the present invention.

<1-7. Additives>
The nonaqueous electrolytic solution of the present invention may contain various additives as long as the effects of the present invention are not significantly impaired. In the case where the preparation process is performed by adding an additive, a conventionally known one can be arbitrarily used. In addition, an additive may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  Examples of the additive include an overcharge inhibitor and an auxiliary agent for improving capacity maintenance characteristics and cycle characteristics after high-temperature storage. Among these, carbonates having at least one of an unsaturated bond and a halogen atom as an aid for improving capacity retention characteristics and cycle characteristics after high-temperature storage (hereinafter sometimes abbreviated as “specific carbonate”) Is preferably added. Hereinafter, the specific carbonate and other additives will be described separately.

<1-7-1. Specific carbonate>
The specific carbonate is a carbonate having at least one of an unsaturated bond and a halogen atom. However, the specific carbonate may have only an unsaturated bond, may have only a halogen atom, and is unsaturated. It may have both a bond and a halogen atom.

  There is no restriction | limiting in particular in the molecular weight of a specific carbonate, Although it is arbitrary unless the effect of this invention is impaired remarkably, Usually, 50 or more, Preferably it is 80 or more, Usually, 250 or less, Preferably it is 150 or less. If the molecular weight is too large, the solubility of the specific carbonate in the non-aqueous electrolytic solution may be reduced, and the effect may not be sufficiently exhibited.

  Moreover, there is no restriction | limiting in particular also in the manufacturing method of a specific carbonate, It is possible to select and manufacture a well-known method arbitrarily.

  In addition, the specific carbonate may be included alone in the nonaqueous electrolytic solution of the present invention, or two or more may be combined in any combination and ratio.

  Moreover, there is no restriction | limiting in the compounding quantity of the specific carbonate with respect to the non-aqueous electrolyte solution of this invention, Although it is arbitrary unless the effect of this invention is impaired remarkably, Usually 0.01 mass with respect to the non-aqueous electrolyte solution of this invention. %, Preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and usually 70% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less. Is desirable.

  Below the lower limit of this range, when the non-aqueous electrolyte solution of the present invention is used in a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery is less likely to exhibit a sufficient cycle characteristic improving effect. There is. In addition, if the ratio of the specific carbonate is too large, when the non-aqueous electrolyte solution of the present invention is used in a non-aqueous electrolyte secondary battery, the high-temperature storage characteristics and continuous charge characteristics of the non-aqueous electrolyte secondary battery deteriorate. In particular, there are cases where the amount of gas generated increases and the capacity retention rate decreases.

<1-7-1-1. Unsaturated carbonate>
Among the specific carbonates according to the present invention, as a carbonate having an unsaturated bond (hereinafter sometimes abbreviated as “unsaturated carbonate”), a carbon-carbon such as a carbon-carbon double bond or a carbon-carbon triple bond is used. There is no other limitation as long as it is a carbonate having an unsaturated bond, and any unsaturated carbonate can be used. In addition, the carbonate which has an aromatic ring shall also be contained in the carbonate which has an unsaturated bond.

  Examples of unsaturated carbonates include vinylene carbonate derivatives, ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond, phenyl carbonates, vinyl carbonates, allyl carbonates, and the like. .

  Specific examples of vinylene carbonate derivatives include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, catechol carbonate and the like.

  Specific examples of the ethylene carbonate derivatives substituted with an aromatic ring or a substituent having a carbon-carbon unsaturated bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate. Etc.

  Specific examples of phenyl carbonates include diphenyl carbonate, ethyl phenyl carbonate, methyl phenyl carbonate, t-butyl phenyl carbonate, and the like.

  Specific examples of vinyl carbonates include divinyl carbonate and methyl vinyl carbonate.

  Specific examples of allyl carbonates include diallyl carbonate and allyl methyl carbonate.

  Among these unsaturated carbonates, as the specific carbonate, vinylene carbonate derivatives, ethylene derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond are preferable, and in particular, vinylene carbonate, 4,5- Diphenyl vinylene carbonate, 4,5-dimethyl vinylene carbonate or vinyl ethylene carbonate is more preferably used because it forms a stable interface protective film.

<1-7-1-2. Halogenated carbonate>
On the other hand, among the specific carbonates according to the present invention, the carbonate having a halogen atom (hereinafter sometimes abbreviated as “halogenated carbonate”) is not particularly limited as long as it is a carbonate having a halogen atom. Any halogenated carbonate can be used.

  Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a fluorine atom or a chlorine atom is preferable, and a fluorine atom is particularly preferable. The number of halogen atoms contained in the halogenated carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the halogenated carbonate has a plurality of halogen atoms, they may be the same as or different from each other.

  Examples of halogenated carbonates include ethylene carbonate derivatives, dimethyl carbonate derivatives, ethyl methyl carbonate derivatives, diethyl carbonate derivatives and the like.

Specific examples of ethylene carbonate derivatives include, for example,
Fluoroethylene carbonate,
Chloroethylene carbonate,
4,4-difluoroethylene carbonate,
4,5-difluoroethylene carbonate,
4,4-dichloroethylene carbonate,
4,5-dichloroethylene carbonate,
4-fluoro-4-methylethylene carbonate,
4-chloro-4-methylethylene carbonate,
4,5-difluoro-4-methylethylene carbonate,
4,5-dichloro-4-methylethylene carbonate,
4-fluoro-5-methylethylene carbonate,
4-chloro-5-methylethylene carbonate,
4,4-difluoro-5-methylethylene carbonate,
4,4-dichloro-5-methylethylene carbonate,
4- (fluoromethyl) -ethylene carbonate,
4- (chloromethyl) -ethylene carbonate,
4- (difluoromethyl) -ethylene carbonate,
4- (dichloromethyl) -ethylene carbonate,
4- (trifluoromethyl) -ethylene carbonate,
4- (trichloromethyl) -ethylene carbonate,
4- (fluoromethyl) -4-fluoroethylene carbonate,
4- (chloromethyl) -4-chloroethylene carbonate,
4- (fluoromethyl) -5-fluoroethylene carbonate,
4- (chloromethyl) -5-chloroethylene carbonate,
4-fluoro-4,5-dimethylethylene carbonate,
4-chloro-4,5-dimethylethylene carbonate,
4,5-difluoro-4,5-dimethylethylene carbonate,
4,5-dichloro-4,5-dimethylethylene carbonate,
4,4-difluoro-5,5-dimethylethylene carbonate,
Examples include 4,4-dichloro-5,5-dimethylethylene carbonate.

Specific examples of dimethyl carbonate derivatives include, for example,
Fluoromethyl methyl dimethyl carbonate,
Difluoromethyl methyl dimethyl carbonate,
Trifluoromethyl methyl dimethyl carbonate,
Bis (fluoromethyl) dimethyl carbonate,
Bis (difluoro) methyldimethyl carbonate,
Bis (trifluoro) methyl dimethyl carbonate,
Chloromethyl methyl dimethyl carbonate,
Dichloromethyl methyl dimethyl carbonate,
Trichloromethyl methyl dimethyl carbonate,
Bis (chloromethyl) dimethyl carbonate,
Bis (dichloro) methyldimethyl carbonate,
Examples thereof include bis (trichloro) methyldimethyl carbonate.

Specific examples of ethyl methyl carbonate derivatives include, for example,
2-fluoroethyl methyl carbonate,
Ethyl fluoromethyl carbonate,
2,2-difluoroethyl methyl carbonate,
2-fluoroethyl fluoromethyl carbonate,
Ethyl difluoromethyl carbonate,
2,2,2-trifluoroethyl methyl carbonate,
2,2-difluoroethyl fluoromethyl carbonate,
2-fluoroethyl difluoromethyl carbonate,
Ethyl trifluoromethyl carbonate,
2-chloroethyl methyl carbonate,
Ethyl chloromethyl carbonate,
2,2-dichloroethyl methyl carbonate,
2-chloroethyl chloromethyl carbonate,
Ethyl dichloromethyl carbonate,
2,2,2-trichloroethyl methyl carbonate,
2,2-dichloroethyl chloromethyl carbonate,
2-chloroethyl dichloromethyl carbonate,
Examples include ethyl trichloromethyl carbonate.

Specific examples of diethyl carbonate derivatives include, for example,
Ethyl- (2-fluoroethyl) carbonate,
Ethyl- (2,2-difluoroethyl) carbonate,
Bis (2-fluoroethyl) carbonate,
Ethyl- (2,2,2-trifluoroethyl) carbonate,
2,2-difluoroethyl-2′-fluoroethyl carbonate,
Bis (2,2-difluoroethyl) carbonate,
2,2,2-trifluoroethyl-2′-fluoroethyl carbonate,
2,2,2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate,
Bis (2,2,2-trifluoroethyl) carbonate,
Ethyl- (2-chloroethyl) carbonate,
Ethyl- (2,2-dichloroethyl) carbonate,
Bis (2-chloroethyl) carbonate,
Ethyl- (2,2,2-trichloroethyl) carbonate,
2,2-dichloroethyl-2'-chloroethyl carbonate,
Bis (2,2-dichloroethyl) carbonate,
2,2,2-trichloroethyl-2′-chloroethyl carbonate,
2,2,2-trichloroethyl-2 ′, 2′-dichloroethyl carbonate,
Examples thereof include bis (2,2,2-trichloroethyl) carbonate.

  Among these halogenated carbonates, carbonates having fluorine atoms are preferred, carbonate derivatives having fluorine atoms are more preferred, especially fluoroethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate is more preferably used because it forms an interface protective film.

<1-7-1-3. Halogenated unsaturated carbonate>
Furthermore, as the specific carbonate, a carbonate having both an unsaturated bond and a halogen atom (abbreviated as “halogenated unsaturated carbonate”) may be used. There is no restriction | limiting in particular as a halogenated unsaturated carbonate, As long as the effect of this invention is not impaired remarkably, arbitrary halogenated unsaturated carbonates can be used.

  Examples of the halogenated unsaturated carbonate include vinylene carbonate derivatives, ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond, and allyl carbonates.

Specific examples of vinylene carbonate derivatives include, for example,
Fluorovinylene carbonate,
4-fluoro-5-methylvinylene carbonate,
4-fluoro-5-phenyl vinylene carbonate,
4- (trifluoromethyl) vinylene carbonate chlorovinylene carbonate,
4-chloro-5-methylvinylene carbonate,
4-chloro-5-phenyl vinylene carbonate 4- (trichloromethyl) vinylene carbonate, etc. are mentioned.

Specific examples of ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond include, for example,
4-fluoro-4-vinylethylene carbonate,
4-fluoro-5-vinylethylene carbonate,
4,4-difluoro-4-vinylethylene carbonate,
4,5-difluoro-4-vinylethylene carbonate,
4-chloro-5-vinylethylene carbonate,
4,4-dichloro-4-vinylethylene carbonate,
4,5-dichloro-4-vinylethylene carbonate,
4-fluoro-4,5-divinylethylene carbonate,
4,5-difluoro-4,5-divinylethylene carbonate,
4-chloro-4,5-divinylethylene carbonate,
4,5-dichloro-4,5-divinylethylene carbonate,
4-fluoro-4-phenylethylene carbonate,
4-fluoro-5-phenylethylene carbonate,
4,4-difluoro-5-phenylethylene carbonate,
4,5-difluoro-4-phenylethylene carbonate,
4-chloro-4-phenylethylene carbonate,
4-chloro-5-phenylethylene carbonate,
4,4-dichloro-5-phenylethylene carbonate,
4,5-dichloro-4-phenylethylene carbonate,
4,5-difluoro-4,5-diphenylethylene carbonate,
Examples include 4,5-dichloro-4,5-diphenylethylene carbonate.

Specific examples of phenyl carbonates include, for example,
Fluoromethylphenyl carbonate,
2-fluoroethyl phenyl carbonate,
2,2-difluoroethyl phenyl carbonate,
2,2,2-trifluoroethyl phenyl carbonate,
Chloromethylphenyl carbonate,
2-chloroethyl phenyl carbonate,
2,2-dichloroethyl phenyl carbonate,
2,2,2-trichloroethyl phenyl carbonate, etc. are mentioned.

Specific examples of vinyls include, for example,
Fluoromethyl vinyl carbonate,
2-fluoroethyl vinyl carbonate,
2,2-difluoroethyl vinyl carbonate,
2,2,2-trifluoroethyl vinyl carbonate,
Chloromethyl vinyl carbonate,
2-chloroethyl vinyl carbonate,
2,2-dichloroethyl vinyl carbonate,
Examples include 2,2,2-trichloroethyl vinyl carbonate.

Specific examples of allyl carbonates include, for example,
Fluoromethylallyl carbonate,
2-fluoroethyl allyl carbonate,
2,2-difluoroethyl allyl carbonate,
2,2,2-trifluoroethyl allyl carbonate,
Chloromethylallyl carbonate,
2-chloroethyl allyl carbonate,
2,2-dichloroethyl allyl carbonate,
Examples include 2,2,2-trichloroethyl allyl carbonate.

  Among the above-mentioned examples of the halogenated unsaturated carbonate, the specific carbonate is highly effective when used alone, “vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate and 4,5-difluoroethylene carbonate and their derivatives. It is particularly preferable to use “one or more compounds selected from the group consisting of”.

<1-7-2. Other additives>
Hereinafter, additives other than the specific carbonate will be described. Examples of additives other than the specific carbonate include overcharge inhibitors, auxiliary agents for improving capacity maintenance characteristics and cycle characteristics after high-temperature storage, and the like.

<1-7-2-1. Overcharge prevention agent>
As a specific example of the overcharge inhibitor, for example,
Toluene derivatives such as toluene, xylene, etc .;
Biphenyl derivatives unsubstituted or substituted with alkyl groups, such as biphenyl, 2-methylbiphenyl, 3-methylbiphenyl 4-methylbiphenyl;
o-terphenyl, m-terphenyl, p-terphenyl and the like terphenyl derivatives unsubstituted or substituted with an alkyl group;
Partial hydrides of terphenyl derivatives that are unsubstituted or substituted with alkyl groups;
Cycloalkylbenzene derivatives such as cyclopentylbenzene and cyclohexylbenzene;
Alkylbenzene derivatives having a tertiary carbon directly bonded to a benzene ring such as cumene, 1,3-diisopropylbenzene, 1,4-diisopropylbenzene;
alkylbenzene derivatives having a quaternary carbon directly bonded to a benzene ring, such as t-butylbenzene, t-amylbenzene, t-hexylbenzene;
Aromatic compounds having an oxygen atom such as diphenyl ether and dibenzofuran;
Aromatic compounds such as

Furthermore, specific examples of other overcharge inhibitors include, for example,
Fluorobenzene,
Fluorotoluene,
Benzotrifluoride,
2-fluorobiphenyl,
o-cyclohexyl fluorobenzene,
a partially fluorinated product of the aromatic compound such as p-cyclohexylfluorobenzene;
2,4-difluoroanisole,
2,5-difluoroanisole,
Fluorine-containing anisole compounds such as 1,6-difluoroaniol;
And so on.

  In addition, these overcharge inhibitors may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations. Moreover, when using together by arbitrary combinations, the compound of the same classification illustrated above may be used together, and you may use together by a compound of a different classification | category.

Specific examples of using different types of compounds together include toluene derivatives and biphenyl derivatives;
Toluene derivatives and terphenyl derivatives;
Partial hydrides of toluene derivatives and terphenyl derivatives;
Toluene derivatives and cycloalkylbenzene derivatives;
An alkylbenzene derivative having a tertiary carbon bonded directly to a toluene derivative and a benzene ring;
An alkylbenzene derivative having a quaternary carbon directly bonded to a toluene derivative and a benzene ring;
An aromatic compound having a toluene derivative and an oxygen atom;
Partially fluorinated products of toluene derivatives and aromatic compounds;
A toluene derivative and a fluorine-containing anisole compound;

Biphenyl derivatives and terphenyl derivatives;
Partial hydrides of biphenyl and terphenyl derivatives;
Biphenyl derivatives and cycloalkylbenzene derivatives;
An alkylbenzene derivative having a tertiary carbon bonded directly to the benzene ring and the biphenyl derivative;
An alkylbenzene derivative having a quaternary carbon bonded directly to the biphenyl derivative and the benzene ring;
An aromatic compound having a biphenyl derivative and an oxygen atom;
Partially fluorinated products of biphenyl derivatives and aromatic compounds;
Biphenyl derivatives and fluorine-containing anisole compounds;

Terphenyl derivatives and partially hydrides of terphenyl derivatives;
Terphenyl derivatives and cycloalkylbenzene derivatives;
An alkylbenzene derivative having a tertiary carbon directly bonded to the terphenyl derivative and the benzene ring;
Alkylbenzene derivatives having a terphenyl derivative and a quaternary carbon bonded directly to the benzene ring;
A terphenyl derivative and an aromatic compound having an oxygen atom;
Partially fluorinated products of terphenyl derivatives and aromatic compounds;
Terphenyl derivatives and fluorine-containing anisole compounds;
Partial hydrides of terphenyl derivatives and cycloalkylbenzene derivatives;
Alkylbenzene derivatives having a tertiary hydride directly bonded to a hydride of a terphenyl derivative and a benzene ring;
An alkylbenzene derivative having a quaternary carbon directly bonded to the hydride of the terphenyl derivative and the benzene ring;
A partial hydride of a terphenyl derivative and an aromatic compound having an oxygen atom;
Partially hydrides of terphenyl derivatives and partially fluorinated aromatic compounds;
Partial hydrides of terphenyl derivatives and fluorine-containing anisole compounds;

An alkylbenzene derivative having a tertiary carbon bonded directly to the benzene ring and a cycloalkylbenzene derivative;
An alkylbenzene derivative having a cycloalkylbenzene and a quaternary carbon directly bonded to the benzene ring;
A cycloalkylbenzene derivative and an aromatic compound having an oxygen atom;
Partially fluorinated products of cycloalkylbenzene derivatives and aromatic compounds;
A cycloalkylbenzene derivative and a fluorine-containing anisole compound;

An alkylbenzene derivative having a tertiary carbon directly bonded to the benzene ring and an alkylbenzene derivative having a quaternary carbon directly bonded to the benzene ring;
An alkylbenzene derivative having a tertiary carbon directly bonded to a benzene ring and an aromatic compound having an oxygen atom;
A partially fluorinated product of an aromatic compound and an alkylbenzene derivative having a tertiary carbon directly bonded to the benzene ring;
An alkylbenzene derivative having a tertiary carbon directly bonded to a benzene ring and a fluorine-containing anisole compound;
An alkylbenzene derivative having a quaternary carbon directly bonded to a benzene ring and an aromatic compound having an oxygen atom;
A partially fluorinated product of an aromatic compound and an alkylbenzene derivative having a quaternary carbon directly bonded to the benzene ring;
An alkylbenzene derivative having a quaternary carbon directly bonded to a benzene ring and a fluorine-containing anisole compound;

An aromatic compound having an oxygen atom and a partially fluorinated product of the aromatic compound;
An aromatic compound having an oxygen atom and a fluorine-containing anisole compound;

Partially fluorinated aromatic compounds and fluorinated anisole compounds;
Etc.

Specific examples of these include a combination of biphenyl and o-terphenyl,
A combination of biphenyl and m-terphenyl,
A combination of biphenyl and a partial hydride of a terphenyl derivative,
A combination of biphenyl and cumene,
A combination of biphenyl and cyclopentylbenzene,
A combination of biphenyl and cyclohexylbenzene,
A combination of biphenyl and t-butylbenzene,
A combination of biphenyl and t-amylbenzene,
A combination of biphenyl and diphenyl ether,
A combination of biphenyl and dibenzofuran,
A combination of biphenyl and fluorobenzene,
A combination of biphenyl and benzotrifluoride,
A combination of biphenyl and 2-fluorobiphenyl,
A combination of biphenyl and o-fluorocyclohexylbenzene,
A combination of biphenyl and p-fluorocyclohexylbenzene;
A combination of biphenyl and 2,4-difluoroanisole,

a combination of o-terphenyl and a partial hydride of a terphenyl derivative;
a combination of o-terphenyl and cumene,
a combination of o-terphenyl and cyclopentylbenzene;
a combination of o-terphenyl and cyclohexylbenzene;
a combination of o-terphenyl and t-butylbenzene;
a combination of o-terphenyl and t-amylbenzene;
a combination of o-terphenyl and diphenyl ether;
a combination of o-terphenyl and dibenzofuran,
a combination of o-terphenyl and fluorobenzene,
a combination of o-terphenyl and benzotrifluoride,
a combination of o-terphenyl and 2-fluorobiphenyl;
a combination of o-terphenyl and o-fluorocyclohexylbenzene;
a combination of o-terphenyl and p-fluorocyclohexylbenzene;
a combination of o-terphenyl and 2,4-difluoroanisole,

a combination of m-terphenyl and a partial hydride of a terphenyl derivative;
a combination of m-terphenyl and cumene,
a combination of m-terphenyl and cyclopentylbenzene;
a combination of m-terphenyl and cyclohexylbenzene;
a combination of m-terphenyl and t-butylbenzene;
a combination of m-terphenyl and t-amylbenzene;
a combination of m-terphenyl and diphenyl ether;
a combination of m-terphenyl and dibenzofuran,
a combination of m-terphenyl and fluorobenzene,
a combination of m-terphenyl and benzotrifluoride,
a combination of m-terphenyl and 2-fluorobiphenyl;
a combination of m-terphenyl and o-fluorocyclohexylbenzene;
a combination of m-terphenyl and p-fluorocyclohexylbenzene;
a combination of m-terphenyl and 2,4-difluoroanisole,

A combination of partial hydrides of terphenyl derivatives and cumene,
A combination of a partial hydride of a terphenyl derivative and cyclopentylbenzene,
A combination of a partial hydride of a terphenyl derivative and cyclohexylbenzene,
A combination of a partial hydride of a terphenyl derivative and t-butylbenzene,
A combination of a partial hydride of a terphenyl derivative and t-amylbenzene,
A combination of a partial hydride of a terphenyl derivative and diphenyl ether,
A combination of a partial hydride of a terphenyl derivative and dibenzofuran,
A combination of a partial hydride of a terphenyl derivative and fluorobenzene,
A combination of a partial hydride of a terphenyl derivative and benzotrifluoride,
A combination of a partial hydride of a terphenyl derivative and 2-fluorobiphenyl,
A combination of a partial hydride of a terphenyl derivative and o-fluorocyclohexylbenzene,
A combination of a partial hydride of a terphenyl derivative and p-fluorocyclohexylbenzene,
A combination of a partial hydride of a terphenyl derivative and 2,4-difluoroanisole,

A combination of cumene and cyclopentylbenzene,
A combination of cumene and cyclohexylbenzene,
A combination of cumene and t-butylbenzene,
A combination of cumene and t-amylbenzene,
A combination of cumene and diphenyl ether,
A combination of cumene and dibenzofuran,
A combination of cumene and fluorobenzene,
A combination of cumene and benzotrifluoride,
A combination of cumene and 2-fluorobiphenyl,
A combination of cumene and o-fluorocyclohexylbenzene;
A combination of cumene and p-fluorocyclohexylbenzene;
A combination of cumene and 2,4-difluoroanisole,

A combination of cyclohexylbenzene and t-butylbenzene,
A combination of cyclohexylbenzene and t-amylbenzene;
A combination of cyclohexylbenzene and diphenyl ether,
A combination of cyclohexylbenzene and dibenzofuran,
A combination of cyclohexylbenzene and fluorobenzene,
A combination of cyclohexylbenzene and benzotrifluoride,
A combination of cyclohexylbenzene and 2-fluorobiphenyl,
A combination of cyclohexylbenzene and o-fluorocyclohexylbenzene,
A combination of cyclohexylbenzene and p-fluorocyclohexylbenzene,
A combination of cyclohexylbenzene and 2,4-difluoroanisole,

a combination of t-butylbenzene and t-amylbenzene;
a combination of t-butylbenzene and diphenyl ether;
a combination of t-butylbenzene and dibenzofuran,
a combination of t-butylbenzene and fluorobenzene,
a combination of t-butylbenzene and benzotrifluoride,
a combination of t-butylbenzene and 2-fluorobiphenyl;
a combination of t-butylbenzene and o-fluorocyclohexylbenzene;
a combination of t-butylbenzene and p-fluorocyclohexylbenzene;
a combination of t-butylbenzene and 2,4-difluoroanisole,

a combination of t-amylbenzene and diphenyl ether;
a combination of t-amylbenzene and dibenzofuran;
a combination of t-amylbenzene and fluorobenzene,
a combination of t-amylbenzene and benzotrifluoride,
a combination of t-amylbenzene and 2-fluorobiphenyl;
a combination of t-amylbenzene and o-fluorocyclohexylbenzene;
a combination of t-amylbenzene and p-fluorocyclohexylbenzene;
a combination of t-amylbenzene and 2,4-difluoroanisole,

A combination of diphenyl ether and dibenzofuran,
A combination of diphenyl ether and fluorobenzene,
A combination of diphenyl ether and benzotrifluoride,
A combination of diphenyl ether and 2-fluorobiphenyl,
A combination of diphenyl ether and o-fluorocyclohexylbenzene;
A combination of diphenyl ether and p-fluorocyclohexylbenzene;
A combination of diphenyl ether and 2,4-difluoroanisole,

A combination of dibenzofuran and fluorobenzene,
A combination of dibenzofuran and benzotrifluoride,
A combination of dibenzofuran and 2-fluorobiphenyl,
A combination of dibenzofuran and o-fluorocyclohexylbenzene;
A combination of dibenzofuran and p-fluorocyclohexylbenzene;
A combination of dibenzofuran and 2,4-difluoroanisole,

A combination of fluorobenzene and benzotrifluoride,
A combination of fluorobenzene and 2-fluorobiphenyl,
A combination of fluorobenzene and o-fluorocyclohexylbenzene,
A combination of fluorobenzene and p-fluorocyclohexylbenzene,
A combination of fluorobenzene and 2,4-difluoroanisole,

A combination of benzotrifluoride and 2-fluorobiphenyl,
A combination of benzotrifluoride and o-fluorocyclohexylbenzene;
A combination of benzotrifluoride and p-fluorocyclohexylbenzene;
A combination of benzotrifluoride and 2,4-difluoroanisole,

A combination of 2-fluorobiphenyl and o-fluorocyclohexylbenzene,
A combination of 2-fluorobiphenyl and p-fluorocyclohexylbenzene;
A combination of 2-fluorobiphenyl and 2,4-difluoroanisole,

a combination of o-fluorocyclohexylbenzene and p-fluorocyclohexylbenzene;
a combination of o-fluorocyclohexylbenzene and 2,4-difluoroanisole,

a combination of p-fluorocyclohexylbenzene and 2,4-difluoroanisole,
Etc.

  When the non-aqueous electrolyte solution of the present invention contains an overcharge inhibitor, the concentration thereof is arbitrary as long as the effect of the present invention is not significantly impaired, but usually 0.1% by mass or more based on the whole non-aqueous electrolyte solution, It is desirable to set it as the range of 5 mass% or less.

  If the non-aqueous electrolyte of the present invention contains an overcharge inhibitor within a range that does not significantly impair the effects of the present invention, the overcharge protection circuit such as an incorrect usage or an abnormality of the charging device should operate normally. Even if the battery is overcharged due to the situation, it is preferable because the safety of the non-aqueous electrolyte secondary battery is improved.

<1-7-2-2. Auxiliary>
Specific examples of the auxiliary agent for improving capacity maintenance characteristics and cycle characteristics after high-temperature storage include, for example,
Dicarboxylic acid anhydrides such as succinic acid, maleic acid and phthalic acid;
Erythritan carbonate,
Carbonate compounds other than those corresponding to specific carbonates such as spirobisdimethylene carbonate;
Ethylene sulfite,
1,3-propane sultone,
1,4-butane sultone,
Methyl methanesulfonate,
Busulfan,
Sulfolane,
Sulfolene,
Dimethyl sulfone,
Diphenylsulfone,
Methylphenylsulfone,
Dibutyl disulfide,
Dicyclohexyl disulfide,
Tetramethylthiuram monosulfide,
N, N-dimethylmethanesulfonamide,
Sulfur-containing compounds such as N, N-diethylmethanesulfonamide;
1-methyl-2-pyrrolidinone,
1-methyl-2-piperidone,
3-methyl-2-oxazolidinone,
1,3-dimethyl-2-imidazolidinone,
Nitrogen-containing compounds such as N-methylsuccinimide;
Heptane,
Octane,
Hydrocarbon compounds such as cycloheptane;
Fluorobenzene,
Difluorobenzene,
And fluorine-containing aromatic compounds such as benzotrifluoride.

[2. Non-aqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention comprises the non-aqueous electrolyte of the present invention and a positive electrode and a negative electrode capable of occluding and releasing ions. Moreover, the non-aqueous electrolyte secondary battery of the present invention may have other configurations.

<2-1. Battery configuration>
The non-aqueous electrolyte secondary battery of the present invention is the same as the conventionally known non-aqueous electrolyte secondary battery except for the negative electrode and the non-aqueous electrolyte. Usually, the non-aqueous electrolyte of the present invention is the same as the non-aqueous electrolyte secondary battery. A positive electrode and a negative electrode are laminated via an impregnated porous film (separator), and these are housed in a case (exterior body). Therefore, the shape of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

<2-2. Non-aqueous electrolyte>
As the non-aqueous electrolyte, the above-described non-aqueous electrolyte of the present invention is used. In addition, in the range which does not deviate from the meaning of this invention, it is also possible to mix and use other nonaqueous electrolyte solution with respect to the nonaqueous electrolyte solution of this invention.

<2-3. Negative electrode>
The negative electrode active material used for the negative electrode is described below. The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples thereof include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, and the like.

<2-3-1. Carbonaceous material>
As a carbonaceous material used as a negative electrode active material,
(1) natural graphite,
(2) a carbonaceous material obtained by heat-treating an artificial carbonaceous material and an artificial graphite material at least once in the range of 400 to 3200 ° C .;
(3) a carbonaceous material in which the negative electrode active material layer is composed of at least two types of carbonaceous materials having different crystallinity and / or has an interface in contact with the different crystalline carbonaceous materials,
(4) a carbonaceous material in which the negative electrode active material layer is composed of carbonaceous materials having at least two or more different orientations and / or has an interface in contact with the carbonaceous materials having different orientations;
Is preferably a good balance between initial irreversible capacity and high current density charge / discharge characteristics. Further, the carbonaceous materials (1) to (4) may be used alone or in combination of two or more in any combination and ratio.

  Specific examples of the artificial carbonaceous material and the artificial graphite material of (2) above include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, or those obtained by oxidizing these pitches, Needle coke, pitch coke and carbon materials partially graphitized thereof, furnace black, acetylene black, organic pyrolysis products such as pitch-based carbon fibers, carbonizable organic materials, and these carbides or carbonizable organic materials Examples thereof include solutions dissolved in low-molecular organic solvents such as benzene, toluene, xylene, quinoline, and n-hexane, and carbides thereof.

  Specific examples of the above carbonizable organic substances include coal tar pitch from soft pitch to hard pitch, or heavy coal-based oil such as dry distillation liquefied oil, normal pressure residual oil, reduced pressure residual DC. Heavy oils such as ethylene tar produced as a by-product during pyrolysis of heavy oils such as heavy oil, crude oil, naphtha, etc., and aromatic hydrocarbons such as acenaphthylene, decacyclene, anthracene, phenanthrene, and nitrogen atom-containing complexes such as phenazine and acridine Cyclic compounds, heterocyclic compounds containing sulfur atoms such as thiophene and bithiophene, polyphenylenes such as biphenyl and terphenyl, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, insolubilized products of these, nitrogen-containing polyacrylonitrile Organic polymers such as polypyrrole, organic polymers such as sulfur-containing polythiophene and polystyrene Natural polymers such as polysaccharides such as saccharose, cellulose, lignin, mannan, polygalacturonic acid, chitosan, saccharose, thermoplastic resins such as polyphenylene sulfide and polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide Examples thereof include thermosetting resins such as resins.

<2-3-2. Configuration, physical properties, preparation method of carbonaceous negative electrode>
Regarding the properties of the carbonaceous material, the negative electrode containing the carbonaceous material, the electrode-forming method, the current collector, and the lithium ion secondary battery, any one or more of (1) to (18) shown below It is desirable to satisfy

(1) X-ray parameters The d-value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method of carbonaceous materials is usually 0.335 to 0.340 nm, particularly 0.335. Those having a thickness of ˜0.338 nm, particularly 0.335 to 0.337 nm are preferred. The crystallite size (Lc) determined by X-ray diffraction by the Gakushin method is usually 1.0 nm or more, preferably 1.5 nm or more, and particularly preferably 2 nm or more.

  The graphite surface coated with amorphous carbon is preferably graphite having a d-value of 0.335 to 0.338 nm on the lattice plane (002 plane) in X-ray diffraction as a core material. A carbonaceous material having a larger d-value on the lattice plane (002 plane) in X-ray diffraction than the core material is attached, and the d-value on the lattice plane (002 plane) in X-ray diffraction is greater than that of the core material and the core material. The ratio with respect to the carbonaceous material having a large is 99/1 to 80/20 by weight. When this is used, a negative electrode having a high capacity and hardly reacting with the electrolytic solution can be produced.

(2) Ash content The ash content in the carbonaceous material is preferably 1% by mass or less, more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less, based on the total mass of the carbonaceous material. It is preferably 1 ppm or more.

  When the weight ratio of ash exceeds the above range, deterioration of battery performance due to reaction with the non-aqueous electrolyte during charge / discharge may not be negligible. On the other hand, if it falls below the above range, the production requires a lot of time, energy and equipment for preventing contamination, which may increase the cost.

(3) Volume-based average particle size The volume-based average particle size of the carbonaceous material is usually a volume-based average particle size (median diameter) determined by a laser diffraction / scattering method of 1 μm or more, preferably 3 μm or more, It is more preferably 5 μm or more, particularly preferably 7 μm or more, and usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, and particularly preferably 25 μm or less.

  If the volume-based average particle size is below the above range, the irreversible capacity may increase, leading to loss of initial battery capacity. On the other hand, when the above range is exceeded, when an electrode is produced by coating, an uneven coating surface tends to be formed, which may be undesirable in the battery production process.

  The volume-based average particle size is measured by dispersing carbon powder in a 0.2% by weight aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering particle size distribution. This is carried out using a meter (LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material of the present invention.

(4) Raman R value, Raman half-value width As for the Raman R value of the carbonaceous material, a value measured by using an argon ion laser Raman spectrum method is usually 0.01 or more, preferably 0.03 or more, preferably 1 or more is more preferable, and it is usually 1.5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.

  When the Raman R value is below the above range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge / discharge. That is, charge acceptance may be reduced. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if it exceeds the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency may be lowered and the gas generation may be increased.

Further, the Raman half-width in the vicinity of 1580 cm ^{−1 of the} carbonaceous material is not particularly limited, but is usually 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, and usually 100 cm ⁻¹ or less, and 80 cm ⁻¹ or less. Preferably, 60 cm ⁻¹ or less is more preferable, and 40 cm ⁻¹ or less is particularly preferable.

  If the Raman half width is less than the above range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge and discharge. That is, charge acceptance may be reduced. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if it exceeds the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency may be lowered and the gas generation may be increased.

The measurement of the Raman spectrum, using a Raman spectrometer (manufactured by JASCO Corporation Raman spectrometer), the sample is naturally dropped into the measurement cell and filled, and while irradiating the sample surface in the cell with argon ion laser light, This is done by rotating the cell in a plane perpendicular to the laser beam. The resulting Raman spectrum, the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, and measuring the intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, the intensity ratio _{R (R = I B / I} A) Is calculated. The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material of the present invention. Further, the half width of the peak P _A in the vicinity of 1580 cm ^-1 of the resulting Raman spectrum was measured, which is defined as the Raman half-value width of the carbonaceous material of the present invention.

Moreover, said Raman measurement conditions are as follows.
Argon ion laser wavelength: 514.5nm
・ Laser power on the sample: 15-25mW
・ Resolution: 10-20cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
・ Raman R value, Raman half width analysis: background processing,
-Smoothing processing: Simple average, 5 points of convolution

(5) BET specific surface area As for the BET specific surface area of the carbonaceous material, the value of the specific surface area measured using the BET method is usually 0.1 m ² · g ⁻¹ or more, and 0.7 m ² · g ⁻¹ or more. Is preferably 1.0 m ² · g ⁻¹ or more, more preferably 1.5 m ² · g ⁻¹ or more, and usually 100 m ² · g ⁻¹ or less, and 25 m ² · g ⁻¹ or less. It is preferably 15 m ² · g ⁻¹ or less, more preferably 10 m ² · g ⁻¹ or less.

  When the value of the BET specific surface area is less than this range, the acceptability of lithium is likely to deteriorate during charging when used as a negative electrode material, lithium is likely to precipitate on the electrode surface, and stability may be reduced. On the other hand, if it exceeds this range, when used as a negative electrode material, the reactivity with the non-aqueous electrolyte increases, gas generation tends to increase, and a preferable battery may be difficult to obtain.

  The specific surface area was measured by the BET method using a surface area meter (a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under nitrogen flow, Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure becomes 0.3, the nitrogen adsorption BET one-point method by the gas flow method is used. The specific surface area determined by the measurement is defined as the BET specific surface area of the carbonaceous material of the present invention.

(6) Pore size distribution The pore size distribution of the carbonaceous material is calculated by measuring the mercury intrusion amount. By using mercury porosimetry (mercury intrusion method), fine pores with a diameter of 0.01 μm or more and 1 μm or less with voids in particles of carbonaceous material, irregularities due to steps on the particle surface, and contact surfaces between particles, etc. carbonaceous material to be measured to correspond to the holes, usually 0.01 cm ³ · ^{g -1} or more, preferably 0.05 cm ³ · ^{g -1} or more, more preferably 0.1 cm ³ · ^{g -1} or more, It is usually desirable to have a pore size distribution of 0.6 cm ³ · g ⁻¹ or less, preferably 0.4 cm ³ · g ⁻¹ or less, more preferably 0.3 cm ³ · g ⁻¹ or less.

  If the pore size distribution exceeds the above range, a large amount of binder may be required when forming an electrode plate. On the other hand, if it falls below the above range, the high current density charge / discharge characteristics may be deteriorated, and the effect of relaxing the expansion and contraction of the electrode during charge / discharge may not be obtained.

Further, the total pore volume, which is obtained by mercury porosimetry (mercury intrusion method) and corresponds to pores having a diameter of 0.01 μm or more and 100 μm or less, is usually 0.1 cm ³ · g ⁻¹ or more,
Preferably 0.25 cm ³ · ^{g -1} or more, more preferably 0.4 cm ³ · ^{g -1} or higher, and is generally 10 cm ³ · ^{g -1} or less, preferably ^{5 cm} 3 · ^{g -1} or less, 2 cm ³ * G- ¹ or less is still more preferable.

  If the total pore volume exceeds the above range, a large amount of binder may be required when forming an electrode plate. On the other hand, if the amount is below the above range, the effect of dispersing the thickener or the binder may not be obtained when forming the electrode plate.

  The average pore diameter is usually 0.05 μm or more, preferably 0.1 μm or more, more preferably 0.5 μm or more, and usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less.

  If the average pore diameter exceeds the above range, a large amount of binder may be required. Moreover, when it is less than the above range, the high current density charge / discharge characteristics may deteriorate.

  The mercury intrusion is measured using a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Corporation) as an apparatus for mercury porosimetry. As a pretreatment, about 0.2 g of a sample is sealed in a powder cell and deaerated for 10 minutes at room temperature under vacuum (50 μmHg or less). Subsequently, the pressure is reduced to 4 psia (about 28 kPa), mercury is introduced, the pressure is increased stepwise from 4 psia (about 28 kPa) to 40000 psia (about 280 MPa), and then the pressure is reduced to 25 psia (about 170 kPa). The number of steps at the time of pressure increase is 80 points or more, and the mercury intrusion amount is measured after an equilibration time of 10 seconds in each step.

The pore size distribution is calculated from the mercury intrusion curve thus obtained using the Washburn equation. Note that the surface tension (γ) of mercury is 485 dyne · cm ⁻¹ ( ¹ dyne = 10 μN), and the contact angle (ψ) is 140 °. As the average pore diameter, the pore diameter when the cumulative pore volume is 50% is used.

(7) Circularity When the circularity is measured as a spherical degree of the carbonaceous material, it is preferably within the following range. The circularity is defined as “circularity = (peripheral length of an equivalent circle having the same area as the particle projection shape) / (actual perimeter of the particle projection shape)”, and is theoretical when the circularity is 1. Become a true sphere.

  The circularity of the particles having a particle size of 3 to 40 μm in the range of the carbonaceous material is desirably closer to 1, and is preferably 0.1 or more, more preferably 0.5 or more, and more preferably 0.8 or more, 0.85 or more is more preferable, and 0.9 or more is particularly preferable.

  High current density charge / discharge characteristics improve as the degree of circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the high current density charge / discharge characteristics may be lowered for a short time.

  The circularity is measured using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample was dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. The detection range is specified as 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm. The circularity determined by the measurement is defined as the circularity of the carbonaceous material of the present invention.

  The method for improving the degree of circularity is not particularly limited, but a spheroidized sphere is preferable because the shape of the interparticle void when the electrode body is formed is preferable. Examples of spheroidizing treatment include a method of mechanically approximating a sphere by applying a shearing force and a compressive force, a mechanical / physical processing method of granulating a plurality of fine particles by an adhesive force possessed by a binder or particles, etc. Is mentioned.

True density of (8) True Density carbonaceous material is usually 1.4 g · ^{cm -3} or higher, preferably 1.6 g · ^{cm -3} or more, more preferably 1.8 g · ^{cm -3} or more, 2. 0 g · ^{cm -3} or more are particularly preferred, also, usually less than 2.26 g · ^{cm -3.}

  When the true density is below the above range, the crystallinity of carbon is too low, and the initial irreversible capacity may increase. The upper limit of the above range is the theoretical upper limit of the true density of graphite.

  The true density of the carbonaceous material is measured by a liquid phase substitution method (pycnometer method) using butanol. The value obtained by the measurement is defined as the true density of the carbonaceous material of the present invention.

(9) Tap density The tap density of the carbonaceous material is usually 0.1 g · cm ⁻³ or more, preferably 0.5 g · cm ⁻³ or more, more preferably 0.7 g · cm ⁻³ or more, and 1 g · cm ⁻³ or more is particularly preferable, 2 g · cm ⁻³ or less is preferable, 1.8 g · cm ⁻³ or less is more preferable, and 1.6 g · cm ⁻³ or less is particularly preferable.

  When the tap density is below the above range, the packing density is difficult to increase when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, when the above range is exceeded, there are too few voids between particles in the electrode, it is difficult to ensure conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

The tap density is measured by passing through a sieve having an opening of 300 μm, dropping the sample onto a 20 cm ³ tapping cell and filling the sample to the upper end surface of the cell, and then measuring a powder density measuring device (for example, manufactured by Seishin Enterprise Co., Ltd.). Using a tap denser, tapping with a stroke length of 10 mm is performed 1000 times, and the tap density is calculated from the volume at that time and the weight of the sample. The tap density calculated by the measurement is defined as the tap density of the carbonaceous material of the present invention.

(10) Orientation ratio The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less.

  When the orientation ratio is below the above range, the high-density charge / discharge characteristics may deteriorate. The upper limit of the above range is the theoretical upper limit value of the orientation ratio of the carbonaceous material.

The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. Set the molding obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8 MN · m ^{-2 so} that it is flush with the surface of the sample holder for measurement. X-ray diffraction is measured. From the (110) diffraction and (004) diffraction peak intensities of the obtained carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material of the present invention.

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit:
Divergence slit = 0.5 degree Light receiving slit = 0.15 mm
Scattering slit = 0.5 degree / measurement range and step angle / measurement time:
(110) plane: 75 degrees ≦ 2θ ≦ 80 degrees 1 degree / 60 seconds (004) plane: 52 degrees ≦ 2θ ≦ 57 degrees 1 degree / 60 seconds

(11) Aspect ratio (powder)
The aspect ratio of the carbonaceous material is usually 1 or more and usually 10 or less, preferably 8 or less, and more preferably 5 or less.

  If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and the high current density charge / discharge characteristics may deteriorate. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the carbonaceous material.

  The aspect ratio is measured by magnifying and observing the carbonaceous material particles with a scanning electron microscope. Carbonaceous material when three-dimensional observation is performed by selecting arbitrary 50 graphite particles fixed to the end face of a metal having a thickness of 50 microns or less and rotating and tilting the stage on which the sample is fixed. The longest diameter A of the particles and the shortest diameter B orthogonal to the same are measured, and the average value of A / B is obtained. The aspect ratio (A / B) obtained by the measurement is defined as the aspect ratio of the carbonaceous material of the present invention.

(12) Secondary material mixing The secondary material mixing means that two or more carbonaceous materials having different properties are contained in the negative electrode and / or the negative electrode active material. The property referred to here is one selected from the group of X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, and ash content. Shows more than one characteristic.

  Particularly preferable examples of these secondary material mixtures include that the volume-based particle size distribution is not symmetrical when centered on the median diameter, contains two or more carbonaceous materials having different Raman R values, and The X-ray parameters are different.

  As an example of the effect of the auxiliary material mixing, carbonaceous material such as natural graphite, graphite such as artificial graphite (graphite), carbon black such as acetylene black, and amorphous carbon such as needle coke is contained as a conductive agent. It is possible to reduce electrical resistance.

  When mixing a conductive agent as a secondary material mixture, one type may be mixed alone, or two or more types may be mixed in any combination and ratio. The mixing ratio of the conductive agent to the carbonaceous material is usually 0.1% by mass or more and 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 45% by mass or less. Yes, and 40 mass% is preferable.

  If the mixing ratio is less than the above range, it may be difficult to obtain the effect of improving conductivity. On the other hand, exceeding the above range may increase the initial irreversible capacity.

(13) Electrode production Any known method can be used for producing an electrode as long as the effects of the present invention are not significantly limited. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do.

  The thickness of the negative electrode active material layer per side in the stage immediately before the non-aqueous electrolyte injection process of the battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and usually 150 μm or less. 20 μm or less is preferable, and 100 μm or less is more preferable. This is because if the thickness of the negative electrode active material exceeds this range, the non-aqueous electrolyte solution hardly penetrates to the vicinity of the current collector interface, and thus the high current density charge / discharge characteristics may be deteriorated. Further, if the ratio is below this range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease. Further, the negative electrode active material may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.

(14) Current collector As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Copper is particularly preferable from the viewpoint of ease of processing and cost.

  In addition, the shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, or the like when the current collector is a metal material. Among them, a metal thin film is preferable, and a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both can be used as a current collector.

  In addition, when the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used.

  A current collector made of a copper foil produced by a rolling method is suitable for use in a small cylindrical battery because the copper crystals are arranged in the rolling direction so that the negative electrode is hard to crack even if it is rounded sharply or rounded at an acute angle. be able to.

  Electrolytic copper foil, for example, immerses a metal drum in a non-aqueous electrolyte solution in which copper ions are dissolved, and causes the copper to precipitate on the surface of the drum by flowing current while rotating it. Is obtained. Copper may be deposited on the surface of the rolled copper foil by an electrolytic method. One side or both sides of the copper foil may be subjected to a roughening treatment or a surface treatment (for example, a chromate treatment having a thickness of about several nm to 1 μm, a base treatment such as Ti).

  The following physical properties are desired for the current collector substrate.

(14-1) Average surface roughness (Ra)
The average surface roughness (Ra) of the negative electrode active material thin film forming surface of the current collector substrate defined by the method described in JIS B0601-1994 is not particularly limited, but is usually 0.05 μm or more and 0.1 μm or more. Preferably, it is more preferably 0.15 μm or more, and is usually 1.5 μm or less, preferably 1.3 μm or less, more preferably 1.0 μm or less.

  This is because when the average surface roughness (Ra) of the current collector substrate is within the above range, good charge / discharge cycle characteristics can be expected. Further, the area of the interface with the negative electrode active material thin film is increased, and the adhesion with the negative electrode active material thin film is improved. The upper limit value of the average surface roughness (Ra) is not particularly limited, but those having an average surface roughness (Ra) exceeding 1.5 μm are generally available as foils having a practical thickness as a battery. Since it is difficult, those of 1.5 μm or less are usually used.

(14-2) Tensile strength The tensile strength is obtained by dividing the maximum tensile force required until the test piece breaks by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by the same apparatus and method as described in JISZ2241 (metal material tensile test method).

The tensile strength of the current collector substrate is not particularly limited, is usually 100 N · ^{mm -2} or more, preferably 250 N · ^{mm -2} or more, more preferably 400 N · ^{mm -2} or more, 500 N · ^{mm -2} or more Particularly preferred. The tensile strength is preferably as high as possible, but is usually 1000 N · mm ⁻² or less from the viewpoint of industrial availability. If the current collector substrate has a high tensile strength, cracking of the current collector substrate due to expansion / contraction of the negative electrode active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained.

  If the current collector substrate has a high tensile strength, cracking of the current collector substrate due to expansion / contraction of the negative electrode active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained.

(14-3) 0.2% proof stress 0.2% proof stress is the magnitude of a load required to give a plastic (permanent) strain of 0.2%. It means that 0.2% deformation has occurred even when loaded. The 0.2% yield strength is measured with the same equipment and method as the tensile strength.

0.2% proof stress of the current collector substrate is not particularly limited, normally 30 N · ^{mm -2} or more, preferably 150 N · ^{mm -2} or more, particularly preferably 300N · ^{mm -2} or more. The 0.2% resistance value is preferably as high as possible, but 900 N · mm ⁻² or less is usually desirable from the viewpoint of industrial availability. If the current collector substrate has a high 0.2% proof stress, plastic deformation of the current collector substrate due to expansion / contraction of the negative electrode active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained. Can do.

(14-4) Thickness of current collector Although the thickness of the current collector is arbitrary, it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, 100 μm or less. Is preferable, and 30 μm or less is more preferable.

  When the thickness of the current collector is less than 1 μm, the strength may be reduced, which may make application difficult. Moreover, when it becomes thicker than 100 micrometers, the shape of electrodes, such as winding, may be changed. The current collector may be mesh.

(15) Ratio of thickness of current collector and negative electrode active material layer The ratio of the thickness of current collector and negative electrode active material layer is not particularly limited. The value of “material layer thickness) / (current collector thickness)” is preferably 150 or less, more preferably 20 or less, particularly preferably 10 or less, more preferably 0.1 or more, and 0.4 or more. More preferred is 1 or more.

  When the ratio of the thickness of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charge / discharge. On the other hand, below the above range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease.

(16) Electrode density The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g · cm ⁻³ or more. 2 g · cm ⁻³ or more is more preferable, 1.3 g · cm ⁻³ or more is particularly preferable, 2 g · cm ⁻³ or less is preferable, 1.9 g · cm ⁻³ or less is more preferable, and 1.8 g · cm. ⁻³ or less is more preferable, and 1.7 g · cm ⁻³ or less is particularly preferable. When the density of the negative electrode active material existing on the current collector exceeds the above range, the negative electrode active material particles are destroyed, and the initial irreversible capacity increases or non-aqueous system near the current collector / negative electrode active material interface. There is a case where high current density charge / discharge characteristics are deteriorated due to a decrease in permeability of the electrolytic solution. On the other hand, if the amount is less than the above range, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume may decrease.

(17) Binder The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte and the solvent used during electrode production.

  Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, NBR ( Acrylonitrile / butadiene rubber), rubbery polymers such as ethylene / propylene rubber; styrene / butadiene / styrene block copolymers or hydrogenated products thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / Thermoplastic elastomeric polymer such as butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene Soft resinous polymers such as vinyl acetate copolymer and propylene / α-olefin copolymer; Fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymer Polymers: Polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions), and the like. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive agent used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.

  Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. .

  In particular, when an aqueous solvent is used, it is preferable to add a dispersant or the like in addition to the thickener and slurry it using a latex such as SBR. In addition, these solvent may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less, 15% by mass. The following is more preferable, 10 mass% or less is still more preferable, and 8 mass% or less is especially preferable. When the ratio of the binder with respect to a negative electrode active material exceeds the said range, the binder ratio from which the amount of binders does not contribute to battery capacity may increase, and the fall of battery capacity may be caused. On the other hand, below the above range, the strength of the negative electrode may be reduced.

  In particular, when a rubbery polymer typified by SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 0 .6% by mass or more is more preferable, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less.

  Moreover, when the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. Preferably, it is usually 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

  A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  Furthermore, when using a thickener, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Moreover, it is 5 mass% or less normally, 3 mass% or less is preferable, and 2 mass% or less is still more preferable.

  When the ratio of the thickener to the negative electrode active material is less than the above range, applicability may be significantly reduced. Moreover, when it exceeds the said range, the ratio of the negative electrode active material which occupies for a negative electrode active material layer will fall, and the problem that the capacity | capacitance of a battery falls and the resistance between negative electrode active materials may increase.

(18) Electrode orientation ratio The electrode orientation ratio is usually 0.001 or more, preferably 0.005 or more, more preferably 0.01 or more, and usually 0.67 or less. When the electrode plate orientation ratio is below the above range, the high-density charge / discharge characteristics may be deteriorated. The upper limit of the above range is the theoretical upper limit of the electrode plate orientation ratio of the carbonaceous material.

  The electrode plate orientation ratio is measured by measuring the orientation ratio of the negative electrode active material of the electrode by X-ray diffraction for the negative electrode after being pressed to the target density. Although a specific method is not particularly limited, as a standard method, peak separation is performed by fitting peaks of carbon (110) diffraction and (004) diffraction by X-ray diffraction using asymmetric Pearson VII as a profile function. To calculate the integrated intensities of the peaks of (110) diffraction and (004) diffraction, respectively. From the obtained integrated intensity, a ratio represented by (110) diffraction integrated intensity / (004) diffraction integrated intensity is calculated. The electrode negative electrode active material orientation ratio calculated by this measurement is defined as the electrode plate orientation ratio of the carbonaceous material in the present invention.

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
-Target: Cu (Kα ray) graphite monochromator-Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree-Measurement range and step angle / measurement time:
(110) plane: 76.5 degrees ≦ 2θ ≦ 78.5 degrees 0.01 degrees / 3 seconds (004) plane: 53.5 degrees ≦ 2θ ≦ 56.0 degrees 0.01 degrees / 3 seconds Sample preparation: Fix the electrode to the glass plate with double-sided tape with a thickness of 0.1 mm

<2-3-3. Structure, physical properties, and preparation method of negative electrode using metal compound material and metal compound material>
As the metal compound-based material used as the negative electrode active material, if lithium can be occluded / released, a single metal or alloy that forms a lithium alloy, or an oxide, carbide, nitride, silicide, sulfide, Any compound such as phosphide is not particularly limited. Examples of such metal compounds include compounds containing metals such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, and Zn. Among these, a single metal or an alloy that forms a lithium alloy is preferable, and a material containing a group 13 or group 14 metal / metalloid element (that is, excluding carbon) is more preferable. Further, silicon (Si ), Tin (Sn) or lead (Pb) (hereinafter, these three elements may be referred to as “specific metal elements”), simple metals, alloys containing these atoms, or their metals (specific metal elements) It is preferable that it is a compound of these. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Examples of the negative electrode active material having at least one kind of atom selected from the specific metal element include a single metal of any one specific metal element, an alloy composed of two or more specific metal elements, one type, or two or more types Alloys composed of specific metal elements and other one or more metal elements, compounds containing one or more specific metal elements, and oxides, carbides, nitrides, and the like of the compounds Examples include composite compounds such as silicides, sulfides, and phosphides. By using these simple metals, alloys or metal compounds as the negative electrode active material, the capacity of the battery can be increased.

  Moreover, the compound which these complex compounds combined with several elements, such as a metal simple substance, an alloy, or a nonmetallic element, can also be mentioned as an example. More specifically, for example, in silicon and tin, an alloy of these elements and a metal that does not operate as a negative electrode can be used. For example, in the case of tin, a complex compound containing 5 to 6 kinds of elements in combination with a metal that acts as a negative electrode other than tin and silicon, a metal that does not operate as a negative electrode, and a nonmetallic element can also be used. .

  Among these negative electrode active materials, since the capacity per unit weight is large when a battery is formed, any one metal element of a specific metal element, an alloy of two or more specific metal elements, oxidation of a specific metal element Of these, silicon and / or tin metal, alloys, oxides, carbides, nitrides, and the like are particularly preferable from the viewpoint of capacity per unit weight and environmental load.

In addition, the following compounds containing silicon and / or tin are also preferable because the cycle characteristics are excellent, although the capacity per unit mass is inferior to the use of a single metal or an alloy.
The elemental ratio between silicon and / or tin and oxygen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1 .3 or less, more preferably 1.1 or less of silicon and / or tin oxide.
The elemental ratio between silicon and / or tin and nitrogen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1 . 3 or less, more preferably 1.1 or less silicon and / or tin nitride.
The elemental ratio of silicon and / or tin to carbon is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1 .3 or less, more preferably 1.1 or less silicon and / or tin carbide.

  In addition, any one of the above-described negative electrode active materials may be used alone, or two or more thereof may be used in any combination and ratio.

  The negative electrode in the non-aqueous electrolyte secondary battery of the present invention can be manufactured using any known method. Specifically, as a manufacturing method of the negative electrode, for example, a method in which a negative electrode active material added with a binder or a conductive material is roll-formed as it is to form a sheet electrode, or a compression-molded pellet electrode and The above negative electrode is usually applied to a negative electrode current collector (hereinafter also referred to as “negative electrode current collector”) by a method such as a coating method, a vapor deposition method, a sputtering method, or a plating method. A method of forming a thin film layer (negative electrode active material layer) containing an active material is used. In this case, by adding a binder, a thickener, a conductive material, a solvent, etc. to the above-mentioned negative electrode active material to form a slurry, applying this to the negative electrode current collector, drying, and pressing to increase the density A negative electrode active material layer is formed on the negative electrode current collector.

  Examples of the material of the negative electrode current collector include steel, copper alloy, nickel, nickel alloy, and stainless steel. Of these, copper foil is preferred from the viewpoint of easy processing into a thin film and cost.

  The thickness of the negative electrode current collector is usually 1 μm or more, preferably 5 μm or more, and is usually 100 μm or less, preferably 50 μm or less. This is because if the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be too low, and conversely if it is too thin, handling may be difficult.

  In addition, in order to improve the binding effect with the negative electrode active material layer formed on the surface, the surface of these negative electrode current collectors is preferably subjected to a roughening treatment in advance. Surface roughening methods include blasting, rolling with a rough surface roll, polishing cloth with a fixed abrasive particle, grinding wheel, emery buff, machine that polishes the current collector surface with a wire brush equipped with steel wire, etc. Examples thereof include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.

  Further, in order to reduce the weight of the negative electrode current collector and improve the energy density per weight of the battery, a perforated negative electrode current collector such as an expanded metal or a punching metal can be used. In this type of negative electrode current collector, the weight can be changed to white by changing the aperture ratio. Further, when a negative electrode active material layer is formed on both surfaces of this type of negative electrode current collector, the negative electrode active material layer is further less likely to peel due to the rivet effect through the hole. However, when the aperture ratio becomes too high, the contact area between the negative electrode active material layer and the negative electrode current collector becomes small, and thus the adhesive strength may be lowered.

  The slurry for forming the negative electrode active material layer is usually prepared by adding a binder, a thickener and the like to the negative electrode material. In addition, the “negative electrode material” in this specification refers to a material in which a negative electrode active material and a conductive material are combined.

  The content of the negative electrode active material in the negative electrode material is preferably 70% by weight or more, particularly 75% by weight or more, and usually 97% by weight or less, particularly 95% by weight or less. When the content of the negative electrode active material is too small, the capacity of the secondary battery using the obtained negative electrode tends to be insufficient, and when the content is too large, the content of the binder or the like is relatively insufficient. This is because the strength of the negative electrode tends to be insufficient. When two or more negative electrode active materials are used in combination, the total amount of the negative electrode active materials may be set to satisfy the above range.

  Examples of the conductive material used for the negative electrode include metal materials such as copper and nickel; carbon materials such as graphite and carbon black. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. In particular, it is preferable to use a carbon material as the conductive material because the carbon material acts as an active material. It is preferable that the content of the conductive material in the negative electrode material is usually 3% by weight or more, particularly 5% by weight or more, and usually 30% by weight or less, particularly 25% by weight or less. When the content of the conductive material is too small, the conductivity tends to be insufficient. When the content is too large, the content of the negative electrode active material or the like is relatively insufficient, which tends to decrease the battery capacity and strength. . Note that when two or more conductive materials are used in combination, the total amount of the conductive materials may satisfy the above range.

  As the binder used for the negative electrode, any material can be used as long as it is a material safe with respect to the solvent and the electrolytic solution used at the time of producing the electrode. Examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene / butadiene rubber / isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, and ethylene / methacrylic acid copolymer. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. The content of the binder is usually 0.5 parts by weight or more, particularly 1 part by weight or more, and usually 10 parts by weight or less, particularly 8 parts by weight or less, with respect to 100 parts by weight of the negative electrode material. When the content of the binder is too small, the strength of the obtained negative electrode tends to be insufficient. When the content is too large, the content of the negative electrode active material and the like is relatively insufficient, and thus the battery capacity and conductivity tend to be insufficient. It is because it becomes. In addition, when using two or more binders together, what is necessary is just to make it the total amount of a binder satisfy | fill the said range.

  Examples of the thickener used for the negative electrode include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. The thickener may be used as necessary, but when used, the thickener content in the negative electrode active material layer is usually in the range of 0.5 mass% or more and 5 mass% or less. Is preferred.

  The slurry for forming the negative electrode active material layer is prepared by mixing the negative electrode active material with a conductive agent, a binder, or a thickener as necessary, and using an aqueous solvent or an organic solvent as a dispersion medium. . As the aqueous solvent, water is usually used, but a solvent other than water such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone is used in combination at a ratio of about 30% by weight or less with respect to water. You can also. As the organic solvent, usually, cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic carbonization such as anisole, toluene and xylene Examples thereof include alcohols such as hydrogens, butanol and cyclohexanol, among which cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. . Any one of these may be used alone, or two or more may be used in any combination and ratio.

  The viscosity of the slurry is not particularly limited as long as it is a viscosity that can be applied onto the current collector. What is necessary is just to prepare suitably by changing the usage-amount of a solvent etc. at the time of preparation of a slurry so that it may become the viscosity which can be apply | coated.

  The obtained slurry is applied onto the above-described negative electrode current collector, dried, and then pressed to form a negative electrode active material layer. The method of application is not particularly limited, and a method known per se can be used. The drying method is not particularly limited, and a known method such as natural drying, heat drying, or reduced pressure drying can be used.

The electrode structure when the negative electrode active material is made into an electrode by the above method is not particularly limited, but the density of the active material present on the current collector is preferably 1 g · cm ⁻³ or more, and 1.2 g · cm ⁻³ or more is more preferable, 1.3 g · cm ⁻³ or more is particularly preferable, 2 g · cm ⁻³ or less is preferable, 1.9 g · cm ⁻³ or less is more preferable, and 1.8 g · cm ⁻³ or less. Is more preferable, and 1.7 g · cm ⁻³ or less is particularly preferable. When the density of the active material existing on the current collector exceeds the above range, the active material particles are destroyed, the initial irreversible capacity increases, and the non-aqueous electrolyte solution near the current collector / active material interface There is a case where high current density charge / discharge characteristics are deteriorated due to decrease in permeability. On the other hand, below the above range, the conductivity between the active materials may be reduced, the battery resistance may be increased, and the capacity per unit volume may be reduced.

<2-3-4. Lithium-containing metal composite oxide material, and negative electrode configuration, physical properties, and preparation method using lithium-containing metal composite oxide material>
The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, but preferably a lithium-containing composite metal oxide material containing titanium, A composite oxide of titanium (hereinafter abbreviated as “lithium titanium composite oxide”) is preferable. That is, it is particularly preferable to use a lithium-titanium composite oxide having a spinel structure in a negative electrode active material for a lithium ion secondary battery because the output resistance is greatly reduced.

  In addition, lithium or titanium of the lithium titanium composite oxide is at least selected from the group consisting of other metal elements such as Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. Those substituted with one element are also preferred.

  The metal oxide is a lithium titanium composite oxide represented by the general formula (4). In the general formula (4), 0.7 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.3, It is preferable that 0 ≦ z ≦ 1.6 because the structure upon doping and dedoping of lithium ions is stable.

(Chemical Formula 50)
_{Li x Ti y M z O 4} (4)
[In General Formula (7), M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. ]

Among the compositions represented by the general formula (4),
(A) 1.2 ≦ x ≦ 1.4, 1.5 ≦ y ≦ 1.7, z = 0
(B) 0.9 ≦ x ≦ 1.1, 1.9 ≦ y ≦ 2.1, z = 0
(C) 0.7 ≦ x ≦ 0.9, 2.1 ≦ y ≦ 2.3, z = 0
This structure is particularly preferable because of a good balance of battery performance.

Particularly preferred representative compositions of the above compounds are Li _4/3 Ti _5/3 O ₄ in (a), Li ₁ Ti ₂ O ₄ in (b), and Li _4/5 Ti _11/5 O in (c). ₄ . As for the structure of Z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.

  In addition to the above-described requirements, the negative electrode active material in the present invention preferably satisfies at least one of the characteristics such as physical properties and shapes shown in the following (1) to (13). It is particularly preferred to satisfy more than one species at the same time.

(1) BET specific surface area As for the BET specific surface area of the lithium titanium composite oxide used as the negative electrode active material, the specific surface area value measured using the BET method is preferably 0.5 m ² · g ⁻¹ or more. 7 m ² · g ⁻¹ or more is more preferred, 1.0 m ² · g ⁻¹ or more is more preferred, 1.5 m ² · g ⁻¹ or more is particularly preferred, and 200 m ² · g ⁻¹ or less is preferred, 100 m ² · g ⁻¹ or less is more preferred, 50 m ² · g ⁻¹ or less is more preferred, and 25 m ² · g ⁻¹ or less is particularly preferred. When the BET specific surface area is less than the above range, the reaction area in contact with the non-aqueous electrolyte when used as the negative electrode material may decrease, and the output resistance may increase. On the other hand, if it exceeds the above range, the surface of the metal oxide crystal containing titanium and the portion of the end face increase, and due to this, crystal distortion also occurs, irreversible capacity cannot be ignored, which is preferable It may be difficult to obtain a battery.

  The specific surface area was measured by the BET method using a surface area meter (a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under nitrogen flow, Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure becomes 0.3, the nitrogen adsorption BET one-point method by the gas flow method is used. The specific surface area determined by the measurement is defined as the BET specific surface area of the titanium-containing metal oxide of the present invention.

(2) Volume-based average particle diameter The volume-based average particle diameter of lithium-titanium composite oxide (secondary particle diameter when primary particles are aggregated to form secondary particles) is determined by laser diffraction / scattering method. It is defined by the obtained volume-based average particle diameter (median diameter).

  The volume-based average particle size of the lithium titanium composite oxide is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 0.7 μm or more, and usually 50 μm or less, preferably 40 μm or less, 30 μm. The following is more preferable, and 25 μm or less is particularly preferable.

  The volume-based average particle size is measured by dispersing a carbon powder in a 0.2% by mass aqueous solution (10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and a laser diffraction / scattering particle size distribution analyzer. (LA-700 manufactured by Horiba Ltd.) is used. The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material of the present invention.

  When the volume average particle size of the lithium titanium composite oxide is below the above range, a large amount of binder is required at the time of producing the electrode, and as a result, the battery capacity may decrease. On the other hand, if it exceeds the above range, an uneven coating surface tends to be formed when forming an electrode plate, which may be undesirable in the battery manufacturing process.

(3) Average primary particle diameter When primary particles are aggregated to form secondary particles, the average primary particle diameter of the lithium titanium composite oxide is usually 0.01 μm or more, and 0.05 μm or more. Preferably, it is 0.1 μm or more, more preferably 0.2 μm or more, and usually 2 μm or less, preferably 1.6 μm or less, more preferably 1.3 μm or less, and particularly preferably 1 μm or less. When the volume-based average primary particle diameter exceeds the above range, it is difficult to form spherical secondary particles, which adversely affects the powder filling property and the specific surface area greatly decreases. There is a possibility that performance is likely to deteriorate. On the other hand, below the above range, there are cases where the performance of the secondary battery is lowered, for example, reversibility of charge / discharge is inferior because crystals are underdeveloped.

  The primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification at which particles can be confirmed, for example, a magnification of 10,000 to 100,000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is determined for any 50 primary particles. Obtained and obtained by taking an average value.

(4) Shape As the shape of the lithium titanium composite oxide particles, a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, a column shape, etc., which are conventionally used, are used. Thus, it is preferable to form secondary particles, and the shape of the secondary particles is spherical or elliptical.

  In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, the primary particles are aggregated to form secondary particles rather than a single particle active material consisting of only primary particles, so that the expansion and contraction stress is relieved and deterioration is prevented.

  In addition, spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so there is less expansion and contraction of the electrode during charge and discharge, and an electrode is produced. The mixing with the conductive agent is also preferable because it is easy to mix uniformly.

(5) Tap Density Tap density lithium-titanium composite oxide is preferably from 0.05 g · ^{cm -3} or more, 0.1 g · ^{cm -3} or more, and more preferably 0.2 g · ^{cm -3} or more, 0.4 g · cm ⁻³ or more is particularly preferable, 2.8 g · cm ⁻³ or less is preferable, 2.4 g · cm ⁻³ or less is further preferable, and 2 g · cm ⁻³ or less is particularly preferable. When the tap density is less than the above range, the packing density is difficult to increase when used as a negative electrode, and the contact area between particles decreases, so that the resistance between particles increases and the output resistance may increase. On the other hand, if the above range is exceeded, the voids between the particles in the electrode may become too small, and the output resistance may increase due to a decrease in the flow path of the non-aqueous electrolyte solution.

The tap density is measured by passing through a sieve having an opening of 300 μm, dropping the sample onto a 20 cm ³ tapping cell and filling the sample to the upper end surface of the cell, and then measuring a powder density measuring device (for example, manufactured by Seishin Enterprise Co., Ltd.). Using a tap denser, tapping with a stroke length of 10 mm is performed 1000 times, and the density is calculated from the volume at that time and the weight of the sample. The tap density calculated by the measurement is defined as the tap density of the lithium titanium composite oxide of the present invention.

(6) Circularity When the circularity is measured as the spherical degree of the lithium titanium composite oxide, it is preferably within the following range. The circularity is defined as “circularity = (peripheral length of an equivalent circle having the same area as the particle projection shape) / (actual perimeter of the particle projection shape)”. It becomes.

  The circularity of the lithium-titanium composite oxide is preferably as close to 1, and is usually 0.10 or more, preferably 0.80 or more, more preferably 0.85 or more, and particularly preferably 0.90 or more. High current density charge / discharge characteristics improve as the circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the high current density charge / discharge characteristics may be lowered for a short time.

  The circularity is measured using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample was dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. The detection range is specified as 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm. The circularity determined by the measurement is defined as the circularity of the lithium titanium composite oxide of the present invention.

(7) Aspect ratio The aspect ratio of the lithium titanium composite oxide is usually 1 or more and usually 5 or less, preferably 4 or less, more preferably 3 or less, and particularly preferably 2 or less. If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and high current density charge / discharge characteristics may be deteriorated for a short time. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the lithium titanium composite oxide.

  The aspect ratio is measured by magnifying and observing lithium titanium composite oxide particles with a scanning electron microscope. Arbitrary 50 particles fixed on the end face of a metal having a thickness of 50 μm or less are selected, and the stage on which the sample is fixed is rotated and tilted for each, and the maximum particle size is obtained when three-dimensionally observed. The diameter A and the shortest diameter B perpendicular to it are measured, and the average value of A / B is obtained. The aspect ratio (A / B) obtained by the measurement is defined as the aspect ratio of the lithium titanium composite oxide of the present invention.

(8) Method for producing negative electrode active material The method for producing lithium-titanium composite oxide is not particularly limited as long as it does not exceed the gist of the present invention. The method is used.

For example, a method of obtaining an active material by uniformly mixing a titanium source material such as titanium oxide and a source material of another element and a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ as necessary, and firing at a high temperature. Is mentioned.

In particular, various methods are conceivable for producing a spherical or elliptical active material. As an example, a titanium precursor material such as titanium oxide and, if necessary, a raw material material of another element are dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to create a spherical precursor. There is a method in which the active material is obtained by recovering and drying it as necessary, and then adding a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ and baking at a high temperature.

As another example, a titanium raw material such as titanium oxide and, if necessary, a raw material of another element are dissolved or pulverized and dispersed in a solvent such as water. A method of obtaining an active material by adding a Li source such as LiOH, Li ₂ CO ₃ , LiNO _{3 and the} like to an elliptical spherical precursor and baking at a high temperature can be mentioned.

As yet another method, a titanium raw material such as titanium oxide, a Li source such as LiOH, Li ₂ CO ₃ and LiNO ₃ and a raw material of another element as necessary are dissolved or pulverized in a solvent such as water. There is a method in which it is dispersed and dried by a spray dryer or the like to obtain a spherical or elliptical precursor, which is then fired at a high temperature to obtain an active material.

  Also, during these steps, elements other than Ti, such as Al, Mn, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, C, Si, Sn , Ag may be present in the metal oxide structure containing titanium and / or in contact with the oxide containing titanium. By containing these elements, the operating voltage and capacity of the battery can be controlled.

(9) Electrode preparation Any known method can be used to manufacture the electrode. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do.

  The thickness of the negative electrode active material layer per side in the stage immediately before the non-aqueous electrolyte injection process of the battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and the upper limit is 150 μm or less, preferably 120 μm. Below, more preferably 100 μm or less. If it exceeds this range, the non-aqueous electrolyte solution hardly penetrates to the vicinity of the current collector interface, and thus the high current density charge / discharge characteristics may deteriorate. On the other hand, below this range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease. Further, the negative electrode active material may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.

(10) Current collector As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Of these, copper is particularly preferable from the viewpoint of ease of processing and cost.

  The shape of the current collector includes, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, and a foam metal when the current collector is a metal material. Among them, a metal foil film containing copper (Cu) and / or aluminum (Al) is preferable, copper foil and aluminum foil are more preferable, rolled copper foil by a rolling method, and electrolytic copper by an electrolytic method are more preferable. There are foils, both of which can be used as current collectors.

  In addition, when the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used. Moreover, since the specific gravity of aluminum foil is light, when it is used as a current collector, the weight of the battery can be reduced and can be preferably used.

  A current collector made of a copper foil produced by a rolling method is suitable for use in a small cylindrical battery because the copper crystals are arranged in the rolling direction so that the negative electrode is hard to crack even if it is rounded sharply or rounded at an acute angle. be able to.

  Electrolytic copper foil, for example, immerses a metal drum in a non-aqueous electrolyte solution in which copper ions are dissolved, and causes the copper to precipitate on the surface of the drum by flowing current while rotating it. Is obtained. Copper may be deposited on the surface of the rolled copper foil by an electrolytic method. One side or both sides of the copper foil may be subjected to a roughening treatment or a surface treatment (for example, a chromate treatment having a thickness of about several nm to 1 μm, a base treatment such as Ti).

Further, the following physical properties are desired for the current collector substrate.
(10-1) Average surface roughness (Ra)
The average surface roughness (Ra) of the active material thin film forming surface of the current collector substrate defined by the method described in JIS B0601-1994 is not particularly limited, but is usually 0.01 μm or more, preferably 0.03 μm or more. Further, it is usually 1.5 μm or less, preferably 1.3 μm or less, and more preferably 1.0 μm or less.

  This is because when the average surface roughness (Ra) of the current collector substrate is within the above range, good charge / discharge cycle characteristics can be expected. In addition, the area of the interface with the active material thin film is increased, and the adhesion with the negative electrode active material thin film is improved. The upper limit value of the average surface roughness (Ra) is not particularly limited, but those having an average surface roughness (Ra) exceeding 1.5 μm are generally available as foils having a practical thickness as a battery. Since it is difficult, those of 1.5 μm or less are usually used.

(10-2) Tensile strength Tensile strength is obtained by dividing the maximum tensile force required until the test piece breaks by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by the same apparatus and method as described in JISZ2241 (metal material tensile test method).

The tensile strength of the current collector substrate is not particularly limited, is generally 50 N · ^{mm -2} or more, preferably 100 N · ^{mm -2} or more, more preferably 150 N · ^{mm -2} or more. The tensile strength is preferably as high as possible, but usually 1000 N · mm ⁻² or less is desirable from the viewpoint of industrial availability. If the current collector substrate has a high tensile strength, cracking of the current collector substrate due to expansion / contraction of the active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained.

(10-3) 0.2% proof stress 0.2% proof stress is the size of a load necessary to give a plastic (permanent) strain of 0.2%. It means that 0.2% deformation has occurred even when loaded. The 0.2% yield strength is measured by the same apparatus and method as the tensile strength.

0.2% proof stress of the current collector substrate is not particularly limited, normally 30 N · ^{mm -2} or more, preferably 100 N · ^{mm -2} or more, particularly preferably 150 N · ^{mm -2} or more. The 0.2% proof stress is preferably as high as possible, but usually 900 N · mm ⁻² or less is desirable from the viewpoint of industrial availability. If the current collector substrate has a high 0.2% proof stress, plastic deformation of the current collector substrate due to expansion / contraction of the active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained. This is because it can.

(10-4) Thickness of current collector Although the thickness of the current collector is arbitrary, it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, 100 μm or less. Is preferably 30 μm or less. When the thickness of the current collector is thinner than 1 μm, the strength may be reduced, which may make application difficult. Moreover, when it becomes thicker than 100 micrometers, the shape of electrodes, such as winding, may be changed. The current collector may be mesh.

(11) Thickness ratio between current collector and active material layer The thickness ratio between the current collector and active material layer is not particularly limited, but “(the active material layer on one side immediately before non-aqueous electrolyte injection) The value of “thickness) / (current collector thickness)” is usually 150 or less, preferably 20 or less, more preferably 10 or less, and usually 0.1 or more, preferably 0.4 or more. One or more is more preferable.

  When the ratio of the thickness of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charge / discharge. On the other hand, below the above range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease.

(12) Electrode density The electrode structure when the negative electrode active material is converted into an electrode is not particularly limited, but the density of the active material present on the current collector is preferably 1 g · cm ⁻³ or more, and 1.2 g More preferably, cm ⁻³ or more, 1.3 g · cm ⁻³ or more is further preferable, 1.5 g · cm ⁻³ or more is particularly preferable, 3 g · cm ⁻³ or less is preferable, and 2.5 g · cm ^{−. 3} or less is more preferable, 2.2 g · cm ⁻³ or less is more preferable, and 2 g · cm ⁻³ or less is particularly preferable. When the density of the active material present on the current collector exceeds the above range, the binding between the current collector and the negative electrode active material becomes weak, and the electrode and the active material may be separated. On the other hand, below the above range, the conductivity between the negative electrode active materials may decrease, and the battery resistance may increase.

(13) Binder The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte and the solvent used during electrode production.

  Specific examples include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, Rubber polymers such as NBR (acrylonitrile / butadiene rubber) and ethylene / propylene rubber; styrene / butadiene / styrene block copolymer and hydrogenated products thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers and hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate , Soft resinous polymers such as ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, etc. And a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions). These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  The solvent for forming the slurry is not particularly limited as long as it is a solvent that can dissolve or disperse the negative electrode active material, binder, thickener and conductive agent used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.

  Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexameryl phosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like. In particular, when an aqueous solvent is used, a dispersant or the like is added in addition to the above-described thickener, and a slurry is formed using a latex such as SBR. In addition, these may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  The ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 20% by mass or less, 15% by mass. % Or less is preferable, 10 mass% or less is more preferable, and 8 mass% or less is particularly preferable. When the ratio of the binder with respect to a negative electrode active material exceeds the said range, the binder ratio in which the amount of binders does not contribute to battery capacity may increase, and battery capacity may fall. On the other hand, if it is below the above range, the strength of the negative electrode is lowered, which may be undesirable in the battery production process.

  In particular, when a rubbery polymer represented by SBR is contained as a main component, the ratio of the binder to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 6 mass% or more is still more preferable, and it is 5 mass% or less normally, 3 mass% or less is preferable, and 2 mass% or less is still more preferable.

  Further, when the main component contains a fluorine polymer represented by polyvinylidene fluoride, the ratio to the active material is 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, Usually, it is 15 mass% or less, 10 mass% or less is preferable, and 8 mass% or less is still more preferable.

  A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  Furthermore, when using a thickener, the ratio of the thickener to the negative electrode active material is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Usually, it is 5 mass% or less, 3 mass% or less is preferable, and 2 mass% or less is still more preferable. When the ratio of the thickener to the negative electrode active material is less than the above range, applicability may be significantly reduced. Moreover, when it exceeds the said range, the ratio of the active material which occupies for a negative electrode active material layer will fall, the problem that the capacity | capacitance of a battery falls, and the resistance between negative electrode active materials may increase.

<2-4. Positive electrode>
The positive electrode used for the non-aqueous electrolyte secondary battery of the present invention will be described below.

<2-4-1. Cathode active material>
The positive electrode active material used for the positive electrode will be described below.

(1) Composition The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. For example, a material containing lithium and at least one transition metal is preferable. Specific examples include lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.

The transition metal of the lithium transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like. Specific examples include lithium / cobalt composite oxide such as LiCoO ₂ and lithium such as LiNiO _2. Nickel composite oxide, LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _{4 and} other lithium-manganese composite oxides, and some of the transition metal atoms that are the main components of these lithium transition metal composite oxides are Al, Ti, Examples thereof include those substituted with other metals such as V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and Si.

As specific examples of the substituted ones, for example, LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O _{4 and the} like.

As the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples include, for example, LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ). ₃ , iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other metals.

(2) Surface coating A material having a composition different from that of the main constituent of the positive electrode active material (hereinafter referred to as “surface adhering substance” as appropriate) may be used on the surface of the positive electrode active material. . Examples of surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, Examples thereof include sulfates such as calcium sulfate and aluminum sulfate, and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

  These surface adhering substances are, for example, a method in which they are dissolved or suspended in a solvent and impregnated and added to the positive electrode active material and then dried, or a surface adhering substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material. Then, it can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously.

  The mass of the surface adhering material adhering to the surface of the positive electrode active material is usually 0.1 ppm or more, preferably 1 ppm or more, more preferably 10 ppm or more, and usually 20% with respect to the mass of the positive electrode active material. Or less, preferably 10% or less, more preferably 5% or less.

  The surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte on the surface of the positive electrode active material, and can improve the battery life. However, when the adhesion amount is less than the above range, the effect is not sufficiently exhibited. When the adhesion amount is more than the above range, the resistance may increase in order to inhibit the entry / exit of lithium ions, so the above range is preferable.

(3) Shape As the shape of the positive electrode active material particles, a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, a column shape, etc., which are conventionally used, are used. It is preferable to form secondary particles, and the shape of the secondary particles is spherical or elliptical.

  In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, the primary particles are aggregated to form secondary particles rather than a single particle active material having only primary particles, so that the stress of expansion and contraction is relieved and deterioration is prevented.

  In addition, spherical or oval spherical particles are less oriented at the time of forming the electrode than the plate-like equiaxially oriented particles, so there is less expansion and contraction of the electrode during charge and discharge, and when creating the electrode The mixing with the conductive agent is also preferable because it can be easily mixed uniformly.

(4) Tap density The tap density of the positive electrode active material is usually 1.3 g · cm ⁻³ or more, preferably 1.5 g · cm ⁻³ or more, more preferably 1.6 g · cm ⁻³ or more. 7 g · cm ⁻³ or more is particularly preferable, usually 2.5 g · cm ⁻³ or less, and preferably 2.4 g · cm ⁻³ or less.

  By using a metal composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. Therefore, when the tap density of the positive electrode active material is lower than the above range, the amount of the dispersion medium necessary for forming the positive electrode active material layer increases, and the necessary amount of the conductive material and the binder increases. The filling rate of the positive electrode active material is limited, and the battery capacity may be limited. In general, the tap density is preferably as large as possible, but there is no particular upper limit. However, if the tap density is below the above range, diffusion of lithium ions in the positive electrode active material layer as a medium becomes rate-determining and load characteristics are likely to deteriorate. There is a case.

The tap density is measured by passing a sieve having an opening of 300 μm, dropping the sample onto a 20 cm ³ tapping cell to fill the cell volume, and then using a powder density measuring instrument (for example, a tap denser manufactured by Seishin Enterprise Co., Ltd.). The tapping with a stroke length of 10 mm is performed 1000 times, and the density is calculated from the volume at that time and the weight of the sample. The tap density calculated by the measurement is defined as the tap density of the positive electrode active material of the present invention.

(5) Median diameter d50
The median diameter d50 (secondary particle diameter when primary particles are aggregated to form secondary particles) of the positive electrode active material particles should also be measured using a laser diffraction / scattering particle size distribution analyzer. Can do.

  The median diameter d50 is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, particularly preferably 3 μm or more, and usually 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less. 15 μm or less is particularly preferable. If the median diameter d50 is below the above range, a high bulk density product may not be obtained. If the median diameter d50 is above the above range, it takes time to diffuse lithium in the particles. In other words, the active material, conductive material, binder, etc. are slurried with a solvent.

  In addition, the filling property at the time of positive electrode preparation can be further improved by mixing two or more types of positive electrode active materials having different median diameters d50 at an arbitrary ratio.

  The median diameter d50 is measured by using a 0.1% by mass sodium hexametaphosphate aqueous solution as a dispersion medium, and using LA-920 manufactured by HORIBA, Ltd. as a particle size distribution meter, the refractive index is adjusted to 1.24 after ultrasonic dispersion for 5 minutes. Set and measure.

(6) Average primary particle diameter When primary particles aggregate to form secondary particles, the average primary particle diameter of the positive electrode active material is usually 0.01 μm or more, preferably 0.05 μm or more, and It is more preferably at least 08 μm, particularly preferably at least 0.1 μm, usually not more than 3 μm, preferably not more than 2 μm, more preferably not more than 1 μm, particularly preferably not more than 0.6 μm. If the above range is exceeded, it may be difficult to form spherical secondary particles, which may adversely affect the powder filling property, or the specific surface area will be greatly reduced, which may increase the possibility that the battery performance such as output characteristics will deteriorate. Because there is. Further, if the value is below the above range, the performance of the secondary battery may be deteriorated, for example, the reversibility of charge / discharge is inferior because the crystal is not developed.

  The average primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.

(7) BET specific surface area As for the BET specific surface area of the positive electrode active material, the value of the specific surface area measured using the BET method is usually 0.2 m ² · g ⁻¹ or more, and 0.3 m ² · g ⁻¹ or more. 0.4 m ² · g ⁻¹ or more is more preferable, usually 4.0 m ² · g ⁻¹ or less, preferably 2.5 m ² · g ⁻¹ or less, and 1.5 m ² · g ^{−. 1} or less is more preferable. When the value of the BET specific surface area is below the above range, the battery performance tends to be lowered. Moreover, when it exceeds the said range, a tap density becomes difficult to raise and the applicability | paintability at the time of positive electrode active material formation may fall.

The BET specific surface area is measured using a surface area meter (a fully automatic surface area measuring device manufactured by Okura Riken). The sample was preliminarily dried at 150 ° C. for 30 minutes under a nitrogen flow, and then a nitrogen helium mixed gas that was accurately adjusted so that the relative pressure of nitrogen with respect to atmospheric pressure was 0.3 was used. It is measured by the nitrogen adsorption BET one-point method by the flow method. The specific surface area determined by the measurement is defined as the BET specific surface area of the anode active material in the present invention.

(8) Method for Producing Positive Electrode Active Material The method for producing the positive electrode active material is not particularly limited as long as it does not exceed the gist of the present invention, but there are several methods, which are common as methods for producing inorganic compounds. The method is used.

In particular, various methods are conceivable for producing a spherical or elliptical active material. For example, transition metal source materials such as transition metal nitrates and sulfates, and other element source materials as required. Is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to produce and recover a spherical precursor, which is dried as necessary, and then LiOH, Li ₂ CO ₃ , LiNO There is a method in which an active material is obtained by adding a Li source such as ₃ and baking at a high temperature.

In addition, as an example of another method, transition metal raw materials such as transition metal nitrates, sulfates, hydroxides, oxides and the like, and if necessary, raw materials of other elements are dissolved or pulverized and dispersed in a solvent such as water. Then, it is dry-molded with a spray dryer or the like to obtain a spherical or oval spherical precursor, and a Li source such as LiOH, Li ₂ CO ₃ , LiNO ₃ is added to the precursor and calcined at a high temperature to obtain an active material Is mentioned.

Examples of other methods include transition metal source materials such as transition metal nitrates, sulfates, hydroxides, oxides, Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ , and other elements as necessary. The raw material is dissolved or pulverized and dispersed in a solvent such as water, and is then dried by a spray dryer or the like to form a spherical or elliptical precursor, which is fired at a high temperature to obtain an active material. Can be mentioned.

<2-4-2. Electrode structure and fabrication method>
Below, the structure of the positive electrode used for this invention and its preparation method are demonstrated.

(1) Method for Producing Positive Electrode The positive electrode is produced by forming a positive electrode active material layer containing positive electrode active material particles and a binder on a current collector. The production of the positive electrode using the positive electrode active material can be produced by any known method. That is, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form are pressure-bonded to a positive electrode current collector, or these materials are liquid media A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry.

  The content of the positive electrode active material in the positive electrode active material layer is usually 10% by mass or more, preferably 30% by mass or more, particularly preferably 50% by mass or more, and usually 99.9% by mass or less, preferably 99% by mass. It is as follows. This is because if the content of the positive electrode active material in the positive electrode active material layer is less than the above range, the electric capacity may be insufficient. Moreover, it is because the intensity | strength of a positive electrode may be insufficient when it exceeds the said range. In addition, the positive electrode active material powder in this invention may be used individually by 1 type, and may use together 2 or more types of a different composition or different powder physical properties by arbitrary combinations and ratios.

(2) Conductive material As the conductive material, a known conductive material can be arbitrarily used. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke. . In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and usually 50% by mass or less, preferably 30% by mass or less in the positive electrode active material layer. More preferably, it is used so as to contain 15% by mass or less. If the content is lower than the above range, the conductivity may be insufficient. Moreover, when it exceeds the said range, battery capacity may fall.

(3) Binder The binder used in the production of the positive electrode active material layer is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used during electrode production.

  In the case of the coating method, any material can be used as long as it is dissolved or dispersed in the liquid medium used during electrode production. Specific examples include, for example, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, and cellulose. Resin polymers such as nitrocellulose; rubbery polymers such as SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluoro rubber, isoprene rubber, butadiene rubber, ethylene propylene rubber; styrene butadiene Styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof Etc. heat Plastic elastomeric polymers: Syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymers, propylene / α-olefin copolymers, etc .; polyvinylidene fluoride (PVdF) , Fluorine-based polymers such as polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymers; polymer compositions having ion conductivity of alkali metal ions (particularly lithium ions), and the like. . These substances may be used alone or in combination of two or more in any combination and ratio.

  The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and usually 80% by mass or less, and 60% by mass. % Or less is preferable, 40% by mass or less is more preferable, and 10% by mass or less is particularly preferable. When the ratio of the binder is below the above range, the positive electrode active material cannot be sufficiently retained, the positive electrode has insufficient mechanical strength, and battery performance such as cycle characteristics may be deteriorated. Moreover, when it exceeds the said range, it may lead to a battery capacity or electroconductivity fall.

(4) Liquid medium The liquid medium for forming the slurry may be a solvent capable of dissolving or dispersing the positive electrode active material, the conductive agent, the binder, and the thickener used as necessary. For example, the type is not particularly limited, and either an aqueous solvent or an organic solvent may be used.

  Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. Examples of organic media include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) and dimethylformamide And amides such as dimethylacetamide; aprotic polar solvents such as hexamethylphosphalamide and dimethyl sulfoxide. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

(5) Thickener When using an aqueous medium as a liquid medium for forming a slurry, it is preferable to make a slurry using a thickener and a latex such as styrene butadiene rubber (SBR). A thickener is usually used to adjust the viscosity of the slurry.

  The thickener is not limited as long as the effect of the present invention is not significantly limited. Specifically, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof Etc. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  Further, when using a thickener, the ratio of the thickener to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Usually, it is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. If it falls below the above range, applicability may be remarkably reduced, and if it exceeds the above range, the ratio of the active material in the positive electrode active material layer is lowered, the battery capacity is reduced, and the resistance between the positive electrode active materials. May increase.

(6) Consolidation The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer is preferably 1 g · cm ⁻³ or more, more preferably 1.5 g · cm ⁻³ or more, and particularly preferably 2 g · cm ⁻³ or more. The upper limit is preferably 4g · ^{cm -3} or less, more preferably 3.5 g · ^{cm -3} or less, 3 g · ^{cm -3} or less are particularly preferred. When the density of the positive electrode active material layer exceeds the above range, the permeability of the non-aqueous electrolyte solution to the vicinity of the current collector / active material interface may decrease, and the charge / discharge characteristics at a high current density may decrease. . Moreover, when less than the said range, the electroconductivity between active materials may fall and battery resistance may increase.

(7) Current collector The material of the positive electrode current collector is not particularly limited, and any known material can be used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbonaceous materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

  Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foam metal, etc. A carbon thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape.

  Although the thickness of the metal thin film is arbitrary, it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the thin film is thinner than the above range, the strength required for the current collector may be insufficient. Moreover, when a thin film is thicker than the said range, a handleability may be impaired.

(8) Treatment of electrode The non-aqueous electrolyte solution of the present invention is a non-aqueous electrolyte secondary battery comprising a positive electrode or a negative electrode treated with a compound represented by the general formula (1) and / or the general formula (2). It is preferable to use it because it can give an excellent cycle characteristic and can suppress the reaction on the electrode surface.

  The method of treating the positive electrode or the negative electrode with at least one selected from the group consisting of the compound represented by the general formula (1) and the compound represented by the general formula (2) is not particularly limited, A method of uniformly distributing the compound represented by the general formula (1) and / or the compound represented by the general formula (2) on the electrode surface is preferable. Specifically, the method is represented by the general formula (1). Particularly preferred is a method of immersing or coating the electrode in a solution obtained by dissolving or dispersing the compound represented by formula (2) and / or the compound represented by formula (2) in a solvent or dispersion medium.

  Moreover, it is also possible to process a positive electrode active material or a negative electrode active material, and that case is also included in the concept of “treatment of positive electrode or negative electrode” of the present invention. In this case, the positive electrode active material or the negative electrode active material is mixed with a solution obtained by dissolving or dispersing the compound represented by the general formula (1) or the compound represented by the general formula (2) in a solvent or a dispersion medium. The positive electrode or the negative electrode may be formed using the active material after the treatment. In addition, in order to further strengthen the interaction between the compound represented by the general formula (1) and / or the compound represented by the general formula (2) and the electrode or the electrode active material, the electrode after the treatment is overheated. It is preferable to do. The superheating temperature is preferably 45 ° C. or higher and 300 ° C. or lower, more preferably 60 ° C. or higher and 200 ° C. or lower.

<2-5. Separator>
Usually, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the nonaqueous electrolytic solution of the present invention is usually used by impregnating the separator.

  There is no restriction | limiting in particular about the material and shape of a separator, A well-known thing can be arbitrarily employ | adopted unless the effect of this invention is impaired remarkably. Among them, a resin, glass fiber, inorganic material, etc. formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. Is preferred.

  As materials for the resin and the glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker than the above range, not only the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole non-aqueous electrolyte secondary battery may be lowered.

  Furthermore, when a porous material such as a porous sheet or nonwoven fabric is used as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Moreover, it is 90% or less normally, 85% or less is preferable and 75% or less is still more preferable. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

  Moreover, although the average pore diameter of a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable, and it is 0.05 micrometer or more normally. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.

  On the other hand, as the inorganic material, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Things are used.

  As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, a porous layer may be formed by using alumina particles having a 90% particle size of less than 1 μm on both surfaces of the positive electrode and using a fluororesin as a binder.

<2-6. Battery design>
[Electrode group]
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed via the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape via the separator. Either may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .

  When the electrode group occupancy is below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, a gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

[Current collection structure]
The current collecting structure is not particularly limited, but in order to more effectively realize the low-temperature discharge characteristics by the non-aqueous electrolyte of the present invention, a structure that reduces the resistance of the wiring part and the joint part should be adopted. Is preferred. Thus, when internal resistance is reduced, the effect of using the non-aqueous electrolyte solution of this invention is exhibited especially favorable.

  In the case where the electrode group has the laminated structure described above, a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals is preferably used. When the area of one electrode increases, the internal resistance increases. Therefore, it is also preferable to reduce the resistance by providing a plurality of terminals in the electrode. When the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode, respectively, and bundling the terminals.

[Exterior case]
The material of the outer case is not particularly limited as long as it is a substance that is stable with respect to the nonaqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

  In the exterior case using the above metals, a laser-sealed, resistance-welded, ultrasonic welding is used to weld the metals together to form a sealed sealed structure, or a caulking structure using the above-mentioned metals via a resin gasket To do. Examples of the outer case using the laminate film include those having a sealed and sealed structure by heat-sealing resin layers. In order to improve the sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used.

[Protective element]
As the above-mentioned protective element, PTC (Positive Temperature Coefficient), which increases resistance when abnormal heat generation or excessive current flows, thermal fuse, thermistor, current that flows in the circuit due to sudden increase in battery internal pressure or internal temperature during abnormal heat generation For example, a valve (current cutoff valve) that shuts off the current can be used. It is preferable to select a protective element that does not operate under normal use at a high current. From the viewpoint of high output, it is more preferable to design the protective element so as not to cause abnormal heat generation or thermal runaway even without the protective element.

[Exterior body]
The non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body. There is no restriction | limiting in this exterior body, As long as the effect of this invention is not impaired remarkably, a well-known thing can be employ | adopted arbitrarily.

  Specifically, the material of the exterior body is arbitrary, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.

  The shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.

Example 1
<Production of secondary battery>
[Production of positive electrode]
94% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 3% by mass of acetylene black as a conductive material, and 3% by mass of polyvinylidene fluoride (PVdF) as a binder, an N-methylpyrrolidone solvent Mixed in to a slurry. The obtained slurry was applied to both sides of an aluminum foil having a thickness of 14 μm, dried, and rolled to a thickness of 85 μm with a press machine, and punched into a circular shape having a diameter of 12.5 mm to obtain a positive electrode.

[Production of negative electrode]
An electrolytic copper foil having a thickness of 18 μm is used as a current collector substrate, Si is used as a target material, and a direct current sputtering apparatus (“HSM-52” manufactured by Shimadzu Corporation) is used with a power density of 4.7 W / cm ² and a deposition rate (film formation). Speed) About 1.8 nm / sec, a Si thin film was formed to obtain a Si thin film negative electrode.

[Non-aqueous electrolyte]
In a dry argon atmosphere, 1 mol / L of fully dried LiPF ₆ and 1% by mass of difluorophosphate were dissolved in a mixture of ethylene carbonate and diethyl carbonate (volume ratio 3: 7), respectively, and desired non-aqueous electrolysis. Liquid.

[Electrode treatment]
The negative electrode obtained above was processed as follows. 3-Methacrylopropyltriethoxysilane was dissolved so that it might become 1 mass% with respect to diethyl carbonate (DEC), and the negative electrode process liquid was prepared. After impregnating the electrode with this negative electrode treatment liquid, heat treatment was performed at 110 ° C. for 1 hour. Then, it dried under reduced pressure at 60 degreeC for 11 hours, and was used. The positive electrode was used after being dried under reduced pressure at 80 ° C. for 11 hours without being subjected to the above treatment.

[Preparation of non-aqueous electrolyte secondary battery]
The positive electrode was housed in a stainless steel can that also serves as a positive electrode conductor, and a negative electrode was placed on the separator through a polyethylene separator impregnated with an electrolytic solution. The can body and a sealing plate serving also as a negative electrode conductor were caulked and sealed via an insulating gasket to produce a coin-type cell.

<Battery evaluation>
The battery was charged and discharged at a constant current corresponding to 0.2 C at 25 ° C. with a charge end voltage of 4.2 V and a discharge end voltage of 2.5 V for 5 cycles to stabilize the battery operation, and the 6 th cycle was 0.2 C. The battery is charged to a charge end voltage of 4.2 V with a current corresponding to A, and charged until the charge current value reaches a current value corresponding to 0.02 C. 4.2 V—constant current constant voltage charge (CCCV charge) (0.02 C After cutting, a 2.5V discharge is performed at a constant current value corresponding to 0.5C, and a 4.2V-constant current constant voltage charge (CCCV charge) (0.02C) at a current corresponding to 0.2C in the seventh cycle. After cutting), 2.5V discharge was performed at a constant current value corresponding to 1.0C. After that, 4.2V-constant current constant voltage charge (CCCV charge) (0.05C cut) at a current corresponding to 0.5C, and then a condition for performing 2.5V discharge at a constant current value corresponding to 0.5C is 92. 100th cycle, 4.2V-constant current constant voltage charge (CCCV charge) (0.02C cut) at a current corresponding to 0.2C, and 2.5V discharge at a constant current value corresponding to 0.2C Went. Here, 1C represents a current value that can be fully charged in one hour.

Example 2 to Example 4
In the same manner as in Example 1, a positive electrode, a negative electrode, and a nonaqueous electrolytic solution were prepared and prepared. Next, each electrode was processed. That is, as described in Table 1, diethyl carbonate (DEC) or pure water was used, respectively, and 3-methacrylopropyltriethoxysilane or 3-aminopropyltriethoxysilane was dissolved so as to be 1% by mass with respect thereto. Alternatively, a negative electrode treatment liquid was prepared by dispersing, and the negative electrode was treated in the same manner as in Example 1. The positive electrode was also treated in the same manner as in Example 1. After producing a non-aqueous electrolyte secondary battery in the same manner as in Example 1, the battery was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that lithium difluorophosphate was not used. Further, a positive electrode and a negative electrode were produced in the same manner as in Example 1. Next, the negative electrode was only dried under reduced pressure at 60 ° C. for 11 hours. The positive electrode was treated in the same manner as in Example 1. After producing a non-aqueous electrolyte secondary battery in the same manner as in Example 1, the battery was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Examples 2 to 5
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that lithium difluorophosphate was not used. Further, a positive electrode and a negative electrode were produced in the same manner as in Example 1. Next, the electrode was processed. That is, as described in Table 1, diethyl carbonate (DEC) or pure water was used, respectively, and 3-methacrylopropyltriethoxysilane or 3-aminopropyltriethoxysilane was dissolved so as to be 1% by mass with respect thereto. Alternatively, a negative electrode treatment liquid was prepared by dispersing, and the negative electrode was treated in the same manner as in Example 1. The positive electrode was also treated in the same manner as in Example 1. After producing a non-aqueous electrolyte secondary battery in the same manner as in Example 1, the battery was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 6
In the same manner as in Example 1, a positive electrode, a negative electrode, and a nonaqueous electrolytic solution were prepared and prepared. Next, the negative electrode was only dried under reduced pressure at 60 ° C. for 11 hours. The positive electrode was treated in the same manner as in Example 1. After producing a non-aqueous electrolyte secondary battery in the same manner as in Example 1, the battery was evaluated in the same manner as in Example 1. The results are shown in Table 1.

  In Example 1, Example 2, Comparative Example 2 and Comparative Example 3 in the non-aqueous electrolyte solution after the production of the non-aqueous electrolyte secondary battery, 3-methacrylopropyltriethoxysilane is the total amount of the non-aqueous electrolyte solution. It was confirmed by gas chromatography that the content was 0.06% by mass. In addition, in the non-aqueous electrolyte solution after the production of the non-aqueous electrolyte secondary battery of Example 3, Example 4, Comparative Example 4 and Comparative Example 5, 3-aminopropyltriethoxysilane was added to the non-aqueous electrolyte solution. It was confirmed by gas chromatography that the content was 0.13% by mass relative to the total amount.

The results are shown in Table 1 as the ratio of the discharge capacity in each 50 cycles to the discharge capacity in 50 cycles of Comparative Example 1 (no negative electrode treatment, no difluorophosphate) as “50 cycle discharge capacity ratio”. That is, "50 cycle discharge capacity ratio"
(50 cycle discharge capacity ratio)
= (Discharge capacity at 50 cycles) / (Discharge capacity of Comparative Example 1 at 50 cycles)
It is represented by

  As is clear from Table 1, the negative electrode was treated with the compound represented by the general formula (1) or the general formula (2) (condition 1), and “monofluorophosphate and / or“ The non-aqueous electrolyte secondary battery produced using the non-aqueous electrolyte solution of the present invention containing (or condition 2) lithium difluorophosphate that is “or difluorophosphate” is either Condition 1 or Condition 2. Compared to non-aqueous electrolyte secondary batteries that do not satisfy either or both conditions, the discharge capacity after 50 cycles shows a large value, suppresses deterioration due to charging / discharging of the battery, and extends battery life Successful.

  Specifically, in Examples 1 to 4 that satisfy both Condition 1 and Condition 2, deterioration of battery characteristics due to charge / discharge was suppressed. On the other hand, it was found that Comparative Example 1, which does not satisfy both conditions, has a low discharge capacity retention rate and severe battery deterioration. Further, Comparative Examples 2 to 6 satisfying only one of Condition 1 or Condition 2 showed a large discharge capacity compared to Comparative Example 1 and confirmed the effect of suppressing battery deterioration. The effect was small with respect to the nonaqueous electrolyte secondary battery (Examples 1 to 4) of the invention. Here, conditions 1 and 2 are described, but this is not limited to the contents of the present embodiment as long as the contents are described in the claims.

  According to the non-aqueous electrolyte solution of the present invention, it is possible to provide a non-aqueous electrolyte solution and a non-aqueous electrolyte secondary battery excellent in cycle characteristics. Therefore, it can be suitably used in various fields such as an electronic device in which a non-aqueous electrolyte secondary battery is used.

  The use of the non-aqueous electrolyte for secondary batteries and the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and can be used for various known applications. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. Electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorbikes, bicycles, lighting equipment, toys, game equipment, watches, electric tools, strobes, cameras, etc. Can do.

Claims (8)

A non-aqueous electrolyte solution used in a non-aqueous electrolyte secondary battery comprising a negative electrode and a positive electrode capable of occluding and releasing ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution comprises an electrolyte and a non-aqueous solvent. And a monofluorophosphate and / or difluorophosphate and a compound represented by the general formula (1) and / or the general formula (2) with respect to the total amount of the non-aqueous electrolyte solution. , 0.001% by mass to 10% by mass, and a non-aqueous electrolyte for secondary batteries.

[R ¹ , R ² , R ³ , and R ⁴ are each independently an organic group or a halogen atom, and at least one of R ¹ , R ² , R ³ , and R ⁴ is heterogeneous with an atom directly bonded to X It is a group which is an atom, and the same thing may be contained in R ¹ , R ² , R ³ and R ⁴ . X is an atom other than a carbon atom. ]

[R ⁵ , R ⁶ and R ⁷ are each independently an organic group or a halogen atom, and at least one of R ⁵ , R ⁶ and R ⁷ is a group in which an atom directly bonded to Y is a hetero atom. , R ⁵ , R ⁶ and R ⁷ may contain the same thing. Y is an atom other than a carbon atom. ] A non-aqueous electrolyte solution used in a non-aqueous electrolyte secondary battery comprising a negative electrode and a positive electrode capable of occluding and releasing ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution comprises a monofluorophosphate and / or Alternatively, it is used for a non-aqueous electrolyte secondary battery containing a difluorophosphate and treating the compound represented by the general formula (1) and / or the general formula (2) into a positive electrode or a negative electrode. A non-aqueous electrolyte for a secondary battery.

[R ¹ , R ² , R ³ , and R ⁴ are each independently an organic group or a halogen atom, and at least one of R ¹ , R ² , R ³ , and R ⁴ is heterogeneous with an atom directly bonded to X It is a group which is an atom, and the same thing may be contained in R ¹ , R ² , R ³ and R ⁴ . X is an atom other than a carbon atom. ]

[R ⁵ , R ⁶ and R ⁷ are each independently an organic group or a halogen atom, and at least one of R ⁵ , R ⁶ and R ⁷ is a group in which an atom directly bonded to Y is a hetero atom. , R ⁵ , R ⁶ and R ⁷ may contain the same thing. Y is an atom other than a carbon atom. ]   The non-aqueous electrolyte solution for a secondary battery according to claim 1 or 2, wherein X of the compound represented by the general formula (1) is Si or Ti.   The non-aqueous electrolyte for secondary batteries according to claim 1 or 2, wherein Y of the compound represented by the general formula (2) is Al.   The heteroatom directly bonded to X or Y in the compound represented by the general formula (1) or (2) is B, N, O, P, S or a halogen atom. The nonaqueous electrolyte solution for secondary batteries in any one.   The monofluorophosphate and / or difluorophosphate is contained in a total amount of 0.001% by mass to 5% by mass with respect to the entire non-aqueous electrolyte solution. The non-aqueous electrolyte for secondary batteries according to claim 1.   A nonaqueous electrolyte secondary battery comprising at least a negative electrode and a positive electrode capable of inserting and extracting lithium ions, and a nonaqueous electrolyte solution, wherein the nonaqueous electrolyte solution is any one of claims 1 to 6. A non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte solution is described.   8. The negative electrode active material used for the negative electrode contains at least one selected from the group consisting of Si metal, Sn metal, Pb metal and a compound containing at least one of these metal elements. The non-aqueous electrolyte secondary battery described.