JP2008258013A - Nonaqueous electrolyte and nonaqueous electrolyte secondary battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery that maintain high capacity and having high continuous charging characteristics. <P>SOLUTION: The nonaqueous electrolyte contains a lithium salt and a nonaqueous organic solvent for dissolving the lithium salt, and the nonaqueous organic solvent contains a cyclic polyamine compound and/or a cyclic polyamide compound and furthermore, contains at least one compound selected from among a group that comprises an unsaturated carbonate, a fluorine-containing carbonate, monofluorophosphate, and difluorophosphate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery using the same.

  Non-aqueous electrolyte secondary batteries have the advantages of high energy density and less self-discharge. Therefore, in recent years, it has been widely used as a power source for consumer mobile devices such as mobile phones, notebook computers, and PDAs. The electrolyte for a non-aqueous electrolyte secondary battery is composed of a lithium salt as a supporting electrolyte and a non-aqueous organic solvent. The non-aqueous organic solvent is required to have a high dielectric constant in order to dissociate the lithium salt, to exhibit high ionic conductivity in a wide temperature range, and to be stable in the battery. Since it is difficult to achieve these requirements with a single solvent, usually a combination of a high boiling point solvent typified by propylene carbonate and ethylene carbonate and a low boiling point solvent such as dimethyl carbonate and diethyl carbonate is used. ing.

  In addition, various additives are often added to the electrolyte in order to improve the initial capacity, rate characteristics, cycle characteristics, high temperature storage characteristics, low temperature characteristics, continuous charge characteristics, self-discharge characteristics, overcharge prevention characteristics, etc. Have been reported. For example, it has been reported that 1,4,8,11-tetraazacyclotetradecane is added as a method for improving cycle characteristics (see Patent Document 1).

However, the demand for higher performance for non-aqueous electrolyte secondary batteries is increasing, and it is necessary to achieve various characteristics such as high capacity, high-temperature storage characteristics, continuous charging characteristics, and cycle characteristics at a high level. It is desired. For example, only the conventional technique of Patent Document 1 that is effective in improving cycle characteristics causes a problem that a large amount of gas is generated during continuous charging and the recovery capacity after the test is greatly reduced, as shown in a reference example later. There was a point.
Japanese Patent Laid-Open No. 9-245832

  This invention is made | formed in view of the said background art, The subject is maintaining the high capacity | capacitance and providing the non-aqueous electrolyte solution and non-aqueous electrolyte secondary battery which give a favorable continuous charge characteristic. .

  As a result of intensive studies to solve the above-mentioned problems, the present inventor contains a non-aqueous electrolyte solution containing a cyclic polyamine compound and / or a cyclic polyamide compound, and if necessary, specifies an unsaturated carbonate or the like. By adding this compound, it was found that the continuous charge characteristics at a high temperature were significantly improved while maintaining a high capacity, and the present invention was completed.

  That is, the present invention is a non-aqueous electrolyte solution containing a lithium salt and a non-aqueous organic solvent for dissolving the lithium salt, wherein the non-aqueous organic solvent contains a cyclic polyamine compound and / or a cyclic polyamide compound, And at least one compound selected from the group consisting of unsaturated carbonates, fluorine-containing carbonates, monofluorophosphates and difluorophosphates. Hereinafter, this invention is abbreviated as “Aspect 1”.

  The present invention also relates to a non-aqueous electrolyte solution comprising a lithium salt and a non-aqueous organic solvent for dissolving the lithium salt, wherein the non-aqueous organic solvent contains a cyclic polyamine compound, and the cyclic carbonate is converted into a non-aqueous system. The non-aqueous electrolyte contains 5% by mass to 40% by mass with respect to the whole organic solvent. Hereinafter, the present invention is abbreviated as “Aspect 2”.

  The present invention also provides a non-aqueous electrolytic solution comprising a lithium salt and a non-aqueous organic solvent for dissolving the lithium salt, wherein the non-aqueous organic solvent contains a cyclic polyamide compound. Be in liquid. Hereinafter, this invention is abbreviated as “Aspect 3”.

  The present invention also relates to a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte.

  According to the present invention, it is possible to obtain a non-aqueous electrolyte secondary battery that maintains a high capacity and is excellent in continuous charge characteristics and the like.

  Hereinafter, the present invention will be described, but the present invention is not limited to the following specific embodiments and can be arbitrarily modified.

  The non-aqueous electrolyte secondary battery of the present invention includes a non-aqueous electrolyte, a positive electrode and a negative electrode capable of inserting and extracting lithium. Moreover, the non-aqueous electrolyte secondary battery of the present invention may have other configurations.

<I. Non-aqueous electrolyte>
(Aspect 1)
The non-aqueous electrolyte of the present invention is a non-aqueous electrolyte containing a lithium salt and a non-aqueous organic solvent that dissolves the lithium salt, and the non-aqueous organic solvent contains a cyclic polyamine compound and / or a cyclic polyamide compound. Furthermore, it is characterized by containing at least one compound selected from the group consisting of unsaturated carbonates, fluorine-containing carbonates, monofluorophosphates and difluorophosphates.

[1. Cyclic polyamine compound]
[1-1. type]
The cyclic polyamine compound contained in the nonaqueous electrolytic solution in the present invention (hereinafter referred to as “the cyclic polyamine compound of the present invention” as appropriate) is a cyclic compound having a structure in which amines are condensed and derivatives thereof. That is, a cyclic compound in which a plurality of nitrogen atoms are bonded with an alkylene group and a derivative in which hydrogen atoms bonded to the nitrogen atoms are substituted with a hydrocarbon group.

  The number of nitrogen atoms constituting the ring is preferably 3 or more, particularly preferably 4 or more, and preferably 6 or less, particularly preferably 4 or less. Moreover, although there is no restriction | limiting in particular as an alkylene group, C2-C4 alkylene groups, such as ethylene group, a methylethylene group, a propylene group, a butylene group, are preferable, and an ethylene group or a propylene group is especially preferable. Also, two or more types of alkylene groups may be included.

  In addition, examples of the hydrocarbon group that replaces the hydrogen bonded to the nitrogen atom include an alkyl group, an aryl group, and an aralkyl group. Of these, an alkyl group is preferred. Illustrative examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group. Examples of the aryl group include a phenyl group, a p-tolyl group, an ethylphenyl group, and a dimethylphenyl group. And an aryl group having 6 to 8 carbon atoms. Examples of the aralkyl group include a benzyl group and a phenethyl group.

  Furthermore, the molecular weight of the cyclic polyamine compound of the present invention is preferably 120 or more, more preferably 170 or more, and preferably 800 or less, more preferably 400 or less, and particularly preferably 300 or less. When the upper limit of this range is exceeded, the compatibility or solubility of the polyamine compound with respect to the non-aqueous electrolyte solution is lowered, and the capacity at a low temperature may be lowered.

  Hereinafter, although the specific example of the cyclic polyamine compound of this invention is given, the cyclic polyamine compound of this invention is not limited to the following illustrations.

Specific examples of the cyclic polyamine compound of the present invention include:
1,4,7-triazacyclononane,
1,4,7-triazacyclodecane,
1,4,8-triazacycloundecane,
1,5,9-triazacyclododecane,
1,6,11-triazacyclopentadecane,
Triazacycloalkanes such as

1,4,7,10-tetraazacyclododecane (also known as cyclen),
1,4,7,10-tetraazacyclotridecane,
1,4,7,11-tetraazacyclotetradecane,
1,4,8,11-tetraazacyclotetradecane (also known as cyclam),
1,4,8,12-tetraazacyclopentadecane,
1,5,9,13-tetraazacyclohexadecane,
Tetraazacycloalkanes such as

1,4,7,10,13-pentaazacyclopentadecane,
1,4,7,10,13-pentaazacyclohexadecane,
Pentaazacycloalkanes such as

1,4,7,10,13,16-hexaazacyclooctadecane (also known as hexacyclene),
1,4,7,10,13,16-hexaazacyclononadecane,
Hexaazacycloalkanes such as

1,4,7-tetramethyl-1,4,7-triazacyclononane,
2,5,8-tetramethyl-1,4,7-triazacyclononane,
1,4,7-tetraethyl-1,4,7-triazacyclononane,
1,4,7-tetraphenyl-1,4,7-triazacyclononane,
1,4,7-tetrabenzyl-1,4,7-triazacyclononane,
1,5,9-tetramethyl-1,5,9-triazacyclododecane,
1,5,9-tetraethyl-1,5,9-triazacyclododecane,
1,5,9-tetraphenyl-1,5,9-triazacyclododecane,
1,5,9-tetrabenzyl-1,5,9-triazacyclododecane,
Hydrocarbon group-substituted triazacycloalkanes such as

1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane,
2,5,8,11-tetramethyl-1,4,7,10-tetraazacyclododecane,
1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane,
1,4,7,10-tetraethyl-1,4,7,10-tetraazacyclododecane,
1,4,7,10-tetraphenyl-1,4,7,10-tetraazacyclododecane,
1,4,7,10-tetrabenzyl-1,4,7,10-tetraazacyclododecane,
1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane,
1,4,8,11-tetraethyl-1,4,8,11-tetraazacyclotetradecane,
1,4,8,11-tetraphenyl-1,4,8,11-tetraazacyclotetradecane,
1,4,8,11-tetrabenzyl-1,4,8,11-tetraazacyclotetradecane,
1,4,8,12-tetramethyl-1,4,8,12-tetraazacyclopentadecane,
1,4,8,12-tetraethyl-1,4,8,12-tetraazacyclopentadecane,
1,4,8,12-tetraphenyl-1,4,8,12-tetraazacyclopentadecane,
1,4,8,12-tetrabenzyl-1,4,8,12-tetraazacyclopentadecane,
Hydrocarbon-substituted tetraazacycloalkanes such as

1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane,
1,4,7,10,13,16-hexaethyl-1,4,7,10,13,16-hexaazacyclooctadecane,
1,4,7,10,13,16-hexaphenyl-1,4,7,10,13,16-hexaazacyclooctadecane,
1,4,7,10,13,16-hexabenzyl-1,4,7,10,13,16-hexaazacyclooctadecane,
And hydrocarbon group-substituted hexaazacycloalkanes.

Among these, preferably,
1,4,7-triazacyclononane,
1,5,9-triazacyclododecane,
Triazacycloalkanes such as
1,4,7,10-tetraazacyclododecane (also known as cyclen),
1,4,8,11-tetraazacyclotetradecane (also known as cyclam),
1,4,8,12-tetraazacyclopentadecane,
Tetraazacycloalkanes such as
1,4,7,10,13,16-hexaazacyclooctadecane (also known as hexacyclene),
1,4,7-tetramethyl-1,4,7-triazacyclononane,
1,5,9-tetramethyl-1,5,9-triazacyclododecane,
1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane,
1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane,
1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane,
1,4,8,12-tetramethyl-1,4,8,12-tetraazacyclopentadecane,
And methyl group-substituted azacycloalkanes.

Among these, particularly preferably,
1,4,7-triazacyclononane,
1,5,9-triazacyclododecane,
Triazacycloalkanes such as
1,4,7,10-tetraazacyclododecane (also known as cyclen),
1,4,8,11-tetraazacyclotetradecane (also known as cyclam),
1,4,8,12-tetraazacyclopentadecane,
Tetraazacycloalkanes such as
1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane,
And methyl group-substituted tetraazacycloalkanes.

  The cyclic polyamine compound of this invention may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  These cyclic polyamine compounds are not too large in molecular weight, are easily dissolved in non-aqueous organic solvents, and some of them are oxidized at the positive electrode. In this case, since a stable film is formed on the positive electrode, the non-aqueous electrolyte secondary battery using the non-aqueous electrolyte containing these cyclic polyamine compounds has improved continuous charge characteristics.

[1-2. composition]
The content of the cyclic polyamine compound of the present invention is not particularly limited as long as it is dissolved in the non-aqueous solvent described later, but is usually 0.001% by mass or more, preferably 0.01% by mass with respect to the entire non-aqueous electrolyte. In addition, the content is usually 5% by mass or less, preferably 1% by mass or less, and particularly preferably 0.2% by mass or less. If the lower limit of this range is not reached, the effect of the present invention may be hardly expressed. If the upper limit is exceeded, a decomposition reaction of a non-aqueous organic solvent such as carbonate using a cyclic polyamine compound as a catalyst occurs. Thus, battery characteristics such as rate characteristics may deteriorate. In addition, when using together 2 or more types of cyclic polyamine compounds of this invention, it is made for the sum total of the density | concentration of the cyclic polyamine compound of this invention to use be in the said range.

[2. Cyclic polyamide compound]
[2-1. type]
The cyclic polyamide compound contained in the nonaqueous electrolytic solution in the present invention (hereinafter referred to as “cyclic polyamide compound of the present invention” as appropriate) is a compound having a plurality of amide bonds (—NHCO—) in the ring skeleton. The number of amide bonds constituting the ring is preferably 2 or more, preferably 6 or less, particularly preferably 4 or less. Those having two amide bonds can be synthesized, for example, by a reaction between a chain polyamine compound and a malonic acid derivative, and those having three or more amide bonds can be synthesized, for example, by a cyclopolymerization reaction of various amino acids. .

  Furthermore, the cyclic polyamide compound of the present invention has a molecular weight of preferably 160 or more, more preferably 200 or more, and preferably 800 or less, more preferably 600 or less, and particularly preferably 500 or less. If the upper limit of this range is exceeded, the compatibility or solubility of the cyclic polyamide compound of the present invention with respect to the non-aqueous organic solvent may be lowered, which may cause a decrease in capacity particularly at low temperatures.

  Hereinafter, although the specific example of the cyclic polyamide compound of this invention is given, the cyclic polyamide compound of this invention is not limited to the following illustrations.

As a specific example of the cyclic polyamide compound of the present invention, assuming that it has two amide bonds,
1,4,7-triazacyclodecane-8,10-dione,
9-methyl-1,4,7-triazacyclodecane-8,10-dione,
9,9′-dimethyl-1,4,7-triazacyclodecane-8,10-dione,
9-ethyl-1,4,7-triazacyclodecane-8,10-dione,
9-phenyl-1,4,7-triazacyclodecane-8,10-dione,
9-benzyl-1,4,7-triazacyclodecane-8,10-dione,
1,5,9-triazacyclododecane-6,8-dione,
7-methyl-1,5,9-triazacyclododecane-6,8-dione,
7,7′-methyl-1,5,9-triazacyclododecane-6,8-dione,
7-ethyl-1,5,9-triazacyclododecane-6,8-dione,
7-phenyl-1,5,9-triazacyclododecane-6,8-dione,
7-benzyl-1,5,9-triazacyclododecane-6,8-dione,
(Substituted) triazacycloalkanediones, such as

1,4,7,10-tetraazacyclotridecane-11,13-dione,
12-methyl-1,4,7,10-tetraazacyclotridecan-11,13-dione,
12,12′-dimethyl-1,4,7,10-tetraazacyclotridecan-11,13-dione,
12-ethyl-1,4,7,10-tetraazacyclotridecan-11,13-dione,
12-phenyl-1,4,7,10-tetraazacyclotridecan-11,13-dione,
12-benzyl-1,4,7,10-tetraazacyclotridecan-11,13-dione,
1,4,8,11-tetraazacyclotetradecane-5,7-dione,
6-methyl-1,4,8,11-tetraazacyclotetradecane-5,7-dione,
6,6′-dimethyl-1,4,8,11-tetraazacyclotetradecane-5,7-dione,
6-ethyl-1,4,8,11-tetraazacyclotetradecane-5,7-dione,
6-phenyl-1,4,8,11-tetraazacyclotetradecane-5,7-dione,
6-benzyl-1,4,8,11-tetraazacyclotetradecane-5,7-dione,
1,4,8,12-tetraazacyclopentadecane-9,11-dione,
10-methyl-1,4,8,12-tetraazacyclopentadecane-9,11-dione,
10,10′-dimethyl-1,4,8,12-tetraazacyclopentadecane-9,11-dione,
10-ethyl-1,4,8,12-tetraazacyclopentadecane-9,11-dione,
10-phenyl-1,4,8,12-tetraazacyclopentadecane-9,11-dione,
10-benzyl-1,4,8,12-tetraazacyclopentadecane-9,11-dione,
(Substituted) tetraazacycloalkanediones, such as

1,4,7,10,13,16-hexaazacyclononadecane-17,19-dione,
18-methyl-1,4,7,10,13,16-hexaazacyclononadecane-17,19-dione,
18,18′-ethyl-1,4,7,10,13,16-hexaazacyclononadecane-17,19-dione,
18-ethyl-1,4,7,10,13,16-hexaazacyclononadecane-17,19-dione,
18-phenyl-1,4,7,10,13,16-hexaazacyclononadecane-17,19-dione,
18-benzyl-1,4,7,10,13,16-hexaazacyclononadecane-17,19-dione,
And the like (substituted) tetraazacycloalkanediones.

In addition, as having three or more amide bonds,
Cyclo (-glycyl) 3,
Cyclo (β-alanyl) 3,
Cyclo (-prolyl) 3,
Cyclic triamides such as

Cyclo (-glycyl) 4,
Cyclo (β-alanyl) 4,
Cyclo (β-alanylglycyl-β-alanylglycyl),
Cyclo (β-alanylprolyl-β-alanylprolyl),
Cyclo (-glycyl) 4,
Cyclo (β-alanyl) 4,
Cyclic tetraamides such as

Cyclo (-glycyl) 6,
Cyclo (-prolyl-glycyl) 3,
And the like, and the like.

Among these, preferably,
1,4,7-triazacyclodecane-8,10-dione,
1,5,9-triazacyclododecane-6,8-dione,
Triazacycloalkanediones such as
1,4,7,10-tetraazacyclotridecane-11,13-dione,
1,4,8,11-tetraazacyclotetradecane-5,7-dione,
1,4,8,12-tetraazacyclopentadecane-9,11-dione,
Tetraazacycloalkanediones such as
Cyclo (β-alanylglycyl-β-alanylglycyl),
Cyclo (-prolyl-glycyl) 3,
Such as hexaamides.

Among these, 1,4,7,10-tetraazacyclotridecan-11,13-dione is particularly preferable.
1,4,8,11-tetraazacyclotetradecane-5,7-dione,
1,4,8,12-tetraazacyclopentadecane-9,11-dione,
Cyclo (β-alanylglycyl-β-alanylglycyl)
It is.

  Moreover, the polyamide compound of this invention mentioned above may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  These cyclic polyamide compounds of the present invention do not have a too high molecular weight and are easily dissolved in a non-aqueous organic solvent, and a part thereof is oxidized at the positive electrode. At this time, in order to form a stable coating film on the positive electrode, when the non-aqueous electrolyte solution containing the cyclic polyamide compound of the present invention is used, the continuous charge characteristics of the non-aqueous electrolyte secondary battery are improved.

[2-2. composition]
The content of the cyclic polyamide compound of the present invention is not particularly limited as long as it is dissolved in the non-aqueous organic solvent described later, but is usually 0.001% by mass or more, preferably 0.01% by mass with respect to the entire non-aqueous electrolyte. % Or more, usually 5% by mass or less, preferably 1% by mass or less, particularly preferably 0.2% by mass or less. If the lower limit of this range is not reached, the effect of the present invention may be hardly exhibited. On the other hand, when the upper limit is exceeded, the film formed on the positive electrode becomes thick and has high resistance, so that the movement of lithium (Li) ions is hindered, and battery characteristics such as rate characteristics may be deteriorated. In addition, when using 2 or more types of cyclic polyamide compounds of this invention together, it is made for the sum total of the density | concentration of the cyclic polyamide compound of this invention to be used in the said range.

[3. At least one compound selected from the group consisting of unsaturated carbonate, fluorine-containing carbonate, monofluorophosphate and difluorophosphate]
The nonaqueous electrolytic solution of the present invention further contains at least one compound selected from the group consisting of unsaturated carbonates, fluorine-containing carbonates, monofluorophosphates and difluorophosphates. These compounds are contained for the purpose of forming a film on the negative electrode and improving battery characteristics.

[3-1. type]
The unsaturated carbonate is not particularly limited as long as it is a carbonate having a carbon-carbon unsaturated bond, and any unsaturated carbonate can be used. For example, a carbonate having an aromatic ring, a carbonate having a carbon-carbon unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond, and the like can be given.

  Specific examples of unsaturated carbonates include vinylene carbonate derivatives such as vinylene carbonate, methyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, phenyl vinylene carbonate, 1,2-diphenyl vinylene carbonate; vinyl ethylene carbonate, 1,2- Ethylene carbonate derivatives substituted with a substituent having a carbon-carbon unsaturated bond such as divinylethylene carbonate, phenylethylene carbonate, 1,2-diphenylethylene carbonate; diphenyl carbonate, methylphenyl carbonate, t-butylphenyl carbonate, etc. Phenyl carbonates; vinyl carbonates such as divinyl carbonate and methyl vinyl carbonate; diallyl carbonate, allyl methyl carbonate Allyl carbonate, and the like of and the like. An unsaturated carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Among these, vinylene carbonate derivatives or ethylene carbonate derivatives substituted with a substituent having a carbon-carbon unsaturated bond are preferable. Specifically, vinylene carbonate, 1,2-diphenyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, vinyl ethylene carbonate, and the like are particularly preferable. By using these unsaturated carbonates, a stable interface protective film is formed on the negative electrode, so that the cycle characteristics of the non-aqueous electrolyte secondary battery are improved.

  The fluorine-containing carbonate is not particularly limited as long as it is a carbonate having a fluorine atom, and an arbitrary one can be used.

To illustrate these,
Fluoroethylene carbonate, 1,1-difluoroethylene carbonate,
cis-difluoroethylene carbonate,
trans-difluoroethylene carbonate,
Fluoropropylene carbonate,
Fluorine-containing cyclic carbonates such as trifluoromethylethylene carbonate,

Trifluoromethyl methyl carbonate,
Trifluoromethyl ethyl carbonate,
2-fluoroethyl methyl carbonate,
2-fluoroethyl ethyl carbonate,
2,2,2-trifluoroethyl methyl carbonate,
2,2,2-trifluoroethyl ethyl carbonate,
Bis (trifluoromethyl) carbonate,
Bis (2-fluoroethyl) carbonate bis (2,2,2-trifluoroethyl) carbonate,
Fluorine-containing chain carbonates such as

Among these,
Fluoroethylene carbonate,
cis-difluoroethylene carbonate,
A fluorine-containing cyclic carbonate such as trans-difluoroethylene carbonate is preferred because it forms a stable interface protective film on the negative electrode.

  In addition, a fluorine-containing carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Any monofluorophosphate and difluorophosphate can be used. Examples thereof include lithium monofluorophosphate, sodium monofluorophosphate, potassium monofluorophosphate, lithium difluorophosphate, sodium difluorophosphate, potassium difluorophosphate and the like. Among these, lithium monofluorophosphate and lithium difluorophosphate are preferable. In addition, monofluorophosphate or difluorophosphate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

[3-2. composition]
The concentration of at least one compound selected from the group consisting of unsaturated carbonates, fluorine-containing carbonates, monofluorophosphates and difluorophosphates in the non-aqueous electrolyte is usually 0 with respect to the whole non-aqueous electrolyte. 0.01 mass% or more, preferably 0.1 mass% or more, more preferably 0.3 mass% or more, and usually 10 mass% or less, preferably 7 mass% or less, more preferably 5 mass% or less. If these concentrations are too large, the coating formed on the negative electrode becomes thick and has high resistance, so the battery capacity decreases. In addition, the amount of gas generated increases under high temperature conditions, which may further increase resistance and decrease the capacity. On the other hand, if the concentration is too small, the effects of the present invention may not be sufficiently exhibited.

[Action]
Here, the reason why the nonaqueous electrolytic solution in the present invention preferably contains at least one compound selected from the group consisting of unsaturated carbonates, fluorine-containing carbonates, monofluorophosphates and difluorophosphates will be described. However, the present invention is not limited for that reason. That is, the polyamine compound and / or polyamide compound of the present invention is oxidized at a lower potential than the solvent at the positive electrode and works as a positive electrode protective film, suppresses the subsequent oxidation reaction of the solvent, and particularly improves the performance deterioration of the high voltage battery. it can. However, these compounds may be reduced in the negative electrode to form a high-resistance film and adversely affect battery characteristics such as high load characteristics. Therefore, when at least one compound selected from the group consisting of unsaturated carbonates, fluorine-containing carbonates, monofluorophosphates and difluorophosphates coexists in the electrolyte, these are polyamine compounds and / or in the negative electrode. A protective film is formed by reduction at a higher potential than the polyamide compound, and the reaction of the polyamine compound and / or the polyamide compound at the negative electrode is suppressed. As a result, a stable film is formed on the positive electrode without forming a high-resistance film on the negative electrode, and the reaction between the electrolyte and the positive electrode is suppressed, so the continuous charge characteristics of the non-aqueous electrolyte secondary battery are dramatically improved. Can be increased.

[4. Non-aqueous organic solvent]
There is no restriction | limiting in particular about a non-aqueous organic solvent, A well-known thing can be used arbitrarily as long as the below-mentioned electrolyte can be melt | dissolved. Examples thereof include chain carbonates, cyclic carbonates, chain esters, cyclic esters (lactone compounds), chain ethers, cyclic ethers, sulfur-containing organic solvents, and the like. Especially, as a solvent which expresses high ionic conductivity, chain carbonates, cyclic carbonates, chain esters, cyclic esters, chain ethers or cyclic ethers are usually preferable.

Specific examples of the chain carbonates include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and the like.
Specific examples of cyclic carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, fluoropropylene carbonate, trifluoromethylethylene carbonate, and the like.
Specific examples of the chain ethers include 1,2-dimethoxyethane, 1,2-diethoxyethane, diethyl ether and the like.
Specific examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, and the like.
Specific examples of the chain esters include, for example, methyl formate, methyl acetate, and methyl propionate.
Specific examples of cyclic esters include γ-butyrolactone and γ-valerolactone.

  Furthermore, a non-aqueous organic solvent may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. However, it is preferable to use a mixture of two or more kinds of non-aqueous organic solvents so as to exhibit desired characteristics, that is, continuous charging characteristics. In particular, it is preferably mainly composed of cyclic carbonates and (chain carbonates or cyclic esters). Here, “being mainly” specifically means that the non-aqueous organic solvent is a total of 70% by mass or more of cyclic carbonates and (chain carbonates or cyclic esters) with respect to the entire non-aqueous electrolyte. Refers to containing.

  When two or more kinds of non-aqueous organic solvents are used in combination, examples of preferable combinations include binary solvents such as ethylene carbonate and methyl ethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and γ-butyrolactone; ethylene carbonate and dimethyl Examples thereof include ternary solvents such as carbonate and ethyl methyl carbonate, ethylene carbonate, methyl ethyl methyl carbonate and diethyl carbonate. Nonaqueous organic solvents mainly containing these are preferably used because they satisfy various properties in a well-balanced manner.

  Moreover, when using an organic solvent as a non-aqueous organic solvent, the carbon number of the organic solvent is usually 3 or more, and usually 13 or less, preferably 7 or less. When the number of carbon atoms is too large, the permeability to the separator and the negative electrode is deteriorated, and a sufficient capacity may not be achieved. On the other hand, if the carbon number is too small, the volatility increases, which may cause an increase in the internal pressure of the battery.

  The molecular weight of the non-aqueous organic solvent is usually 50 or more, preferably 80 or more, and usually 250 or less, preferably 150 or less. If the molecular weight is too large, the permeability to the separator and the negative electrode is deteriorated, and a sufficient capacity may not be achieved. On the other hand, if the molecular weight is too small, the volatility increases, which may increase the battery internal pressure.

    Further, when two or more kinds of non-aqueous organic solvents are used in combination, the ratio of the cyclic carbonate in the non-aqueous organic solvent is usually 5% by mass or more, preferably 10% by mass or more, based on the whole non-aqueous organic solvent. More preferably, it is 15% by mass or more, particularly preferably 20% by mass or more, and is usually 60% by mass or less, preferably 50% by mass or less, particularly preferably 40% by mass or less. If the lower limit of the above range is not reached, the dissociation of the Li salt is less likely to occur, and the electrical conductivity decreases, so the high load capacity tends to decrease. On the other hand, if the upper limit is exceeded, the viscosity becomes too high and Li ions are difficult to move. Therefore, the high load capacity may be reduced.

[5. Lithium salt]
As the lithium salt used for the electrolyte, either an inorganic lithium salt or an organic lithium salt may be used. Examples of inorganic lithium salts include inorganic fluoride salts such as LiPF ₆ , LiAsF ₆ , LiBF ₄ , and LiSbF ₆ ; inorganic chloride salts such as LiAlCl ₄ ; perhalogenates such as LiClO ₄ , LiBrO ₄ , and LiIO _4. Etc. Examples of organic lithium salts include perfluoroalkane sulfonates such as CF ₃ SO ₃ Li and C ₄ F ₉ SO ₃ Li; perfluoroalkane carboxylates such as CF ₃ COOLi; (CF ₃ CO) Perfluoroalkanecarbonimide salts such as ₂ NLi; fluorine-containing organic lithium salts such as perfluoroalkanesulfonimide salts such as (CF ₃ SO ₂ ) ₂ NLi and (C ₂ F ₅ SO ₂ ) ₂ NLi.

Among these, LiPF ₆ , LiBF ₄ , CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, and the like are preferable because they are easily soluble in a solvent and exhibit a high degree of dissociation. In addition, an electrolyte may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. In particular, the combined use of LiPF ₆ and LiBF ₄ or the combined use of LiPF ₆ and (CF ₃ SO ₂ ) ₂ NLi is preferable because it has an effect of improving the continuous charge characteristics.

  The concentration of the electrolyte in the non-aqueous electrolyte is usually 0.5 mol / L or more, preferably 0.75 mol / L or more, and usually 2 mol / L or less, preferably 1. 75 mol / L or less. If the concentration is too low, the electrical conductivity of the non-aqueous electrolyte may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity is lowered due to an increase in viscosity, and precipitation at a low temperature is likely to occur, and the performance of the non-aqueous electrolyte secondary battery tends to be lowered.

[6. Other auxiliaries]
The non-aqueous electrolyte solution in the present invention may contain “other auxiliary agent” for the purpose of improving the wettability, overcharge characteristics, etc. of the non-aqueous electrolyte solution as long as the effects of the present invention are not impaired. Examples of such “other auxiliaries” include acid anhydrides such as maleic anhydride, succinic anhydride, and glutaric anhydride; carboxylates such as vinyl acetate, divinyl adipate, and allyl acetate; diphenyl disulfide, 1,3 -Sulfur such as propane sultone, 1,4-butane sultone, dimethyl sulfone, divinyl sulfone, dimethyl sulfite, ethylene sulfite, 1,4-butanediol dimethane sulfonate, methyl methanesulfonate, -2-propynyl methanesulfonate Containing compounds: aromatics such as t-butylbenzene, biphenyl, o-terphenyl, 4-fluorobiphenyl, fluorobenzene, 2,4-difluorobenzene, cyclohexylbenzene, diphenyl ether, 2,4-difluoroanisole, trifluoromethylbenzene Compound And the like obtained by substituting the like of the aromatic compound with fluorine atoms. Moreover, "other auxiliary agents" may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  The concentration of “other auxiliary agent” in the non-aqueous electrolyte is usually 0.01% by mass or more, preferably 0.05% by mass or more, and usually 10% by mass with respect to the whole non-aqueous electrolyte. Hereinafter, it is preferably 5% by mass or less. When two or more “other auxiliary agents” are used in combination, the total of these concentrations is set within the above range.

[7. Non-aqueous electrolyte state]
The non-aqueous electrolytic solution usually exists in a liquid state, but it may be gelled with a polymer to form a semi-solid electrolyte. The polymer used for the gelation is arbitrary, and examples thereof include polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyethylene oxide, polyacrylate, and polymethacrylate. In addition, the polymer | macromolecule used for gelatinization may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  When a nonaqueous electrolyte is used as a semisolid electrolyte, the ratio of the nonaqueous electrolyte in the semisolid electrolyte is usually 30% by mass or more, preferably 50% by mass with respect to the total amount of the semisolid electrolyte. As described above, it is particularly preferably 75% by mass or more, and usually 99.95% by mass or less, preferably 99% by mass or less, and particularly preferably 98% by mass or less. If the ratio of the non-aqueous electrolyte is too large, it is difficult to hold the electrolyte and liquid leakage tends to occur. Conversely, if it is too small, the charge / discharge efficiency and capacity may be insufficient.

[8. Method for producing non-aqueous electrolyte]
The non-aqueous electrolyte in the present invention comprises a non-aqueous organic solvent, a lithium salt, a cyclic polyamine compound and / or a cyclic polyamide compound in the present invention, “unsaturated carbonate, fluorine-containing carbonate, monofluorophosphate and difluorophosphate”. It can be prepared by dissolving “at least one compound selected from the group consisting of” and “other auxiliary agent” as necessary.

  In preparing the non-aqueous electrolyte, each raw material of the non-aqueous electrolyte, that is, the lithium salt, the cyclic polyamine compound and / or the cyclic polyamide compound in the present invention, the non-aqueous organic solvent, and the “other auxiliary agent” It is preferable to dehydrate in advance. The degree of dehydration is usually 50 ppm or less, preferably 30 ppm or less. In the present specification, ppm means a ratio based on weight.

  If water is present in the non-aqueous electrolyte, electrolysis of water, reaction between water and lithium metal, hydrolysis of lithium salt, and the like may occur. The dehydration means is not particularly limited. For example, when the object to be dehydrated is a liquid such as a non-aqueous organic solvent, a molecular sieve or the like may be used. When the object to be dehydrated is a solid such as a lithium salt, it may be dried at a temperature lower than the temperature at which decomposition occurs.

(Aspect 2)
Another gist of the present invention is a non-aqueous electrolyte solution containing a lithium salt and a non-aqueous organic solvent for dissolving the lithium salt, wherein the non-aqueous organic solvent contains a cyclic polyamine compound, and is further cyclic. The nonaqueous electrolyte solution is characterized by containing 5 to 40% by mass of carbonate with respect to the entire nonaqueous electrolyte solution.

[1. Cyclic polyamine compound]
[1-1. type]
As described above.
[1-2. composition]
As described above.

[2. Cyclic carbonate]
The cyclic carbonate in the present invention is not particularly limited as long as it is a cyclic carbonate, and part or all of the hydrogen atoms may be substituted with a halogen such as fluorine or chlorine. Examples of these include ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, fluoropropylene carbonate, trifluoromethylethylene carbonate, and the like. A cyclic carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  In particular, a combination of ethylene carbonate and propylene carbonate, a combination of ethylene carbonate and fluoroethylene carbonate, and a combination of ethylene carbonate, propylene carbonate and fluoroethylene carbonate are preferably used.

  In this invention, a non-aqueous organic solvent contains 5-40 mass% of cyclic carbonate with respect to the whole non-aqueous organic solvent. As a minimum, 8 mass% or more is preferred, 10 mass% or more is especially preferred, and 12 mass% or more is still more preferred. As an upper limit, 35 mass% or less is preferable, 30 mass% or less is especially preferable, and 25 mass% or less is still more preferable. Even when two or more kinds of cyclic carbonates are used in combination, the total amount of these may be within the above range.

  If the cyclic carbonate is below the lower limit of this range, the Li salt is less likely to dissociate and the electrical conductivity is reduced, so the high load capacity is likely to decrease.If the cyclic carbonate exceeds the upper limit, the cyclic carbonate using a polyamine compound as a catalyst, etc. A decomposition reaction of the non-aqueous organic solvent occurs. For this reason, a large amount of gas such as carbon dioxide is generated during continuous charging at a high temperature, the resistance increases, and the recovery capacity may decrease.

  The carbon number of the cyclic carbonate is usually 3 or more, and usually 13 or less, preferably 5 or less. When the number of carbon atoms is too large, the permeability to the separator and the negative electrode is deteriorated, and a sufficient capacity may not be achieved. On the other hand, if the carbon number is too small, the volatility increases, which may cause an increase in the internal pressure of the battery.

[3. Non-aqueous organic solvent]
As described above.
[4. Lithium salt]
As described above.

[5. At least one compound selected from the group consisting of unsaturated carbonate, fluorine-containing carbonate, monofluorophosphate and difluorophosphate]
In aspect 2, it is preferable to contain at least one compound selected from the group consisting of unsaturated carbonates, fluorine-containing carbonates, monofluorophosphates and difluorophosphates. These compounds are as described above.

[6. Other auxiliaries]
As described above.
[7. Non-aqueous electrolyte state]
As described above.
[8. Method for producing non-aqueous electrolyte]
As described above.

(Aspect 3)
Another gist of the present invention is a non-aqueous electrolyte solution containing a lithium salt and a non-aqueous organic solvent that dissolves the lithium salt, wherein the non-aqueous electrolyte solution contains a cyclic polyamide compound. Exist.

[1. Cyclic polyamide compound]
[1-1. type]
As described above.
[1-2. composition]
As described above.
[2. Non-aqueous organic solvent]
The non-aqueous solvent that can be used is as described above.

Here, the reason why the cyclic polyamide compound alone exerts the effect of the present invention is that the cyclic polyamide compound is delocalized by the influence of the adjacent carbonyl group on the unshared electron pair on nitrogen, and the cyclic polyamine compound and It is far less basic. For this reason, even when a large amount of a solvent such as cyclic carbonate is used, the reaction hardly occurs on the negative electrode. For this reason, the solvent species to be used and their composition are not particularly limited.
[3. Lithium salt]
As described above.

[4. Cyclic carbonate]]
Also in aspect 3, it is preferable to contain a cyclic carbonate. The cyclic carbonate is as described above.

[5. At least one compound selected from the group consisting of unsaturated carbonate, fluorine-containing carbonate, monofluorophosphate and difluorophosphate]
Also in the aspect 3, it is preferable to contain at least one compound selected from the group consisting of unsaturated carbonates, fluorine-containing carbonates, monofluorophosphates and difluorophosphates. These compounds are as described above.

[6. Other auxiliaries]
As described above.
[7. Non-aqueous electrolyte state]
As described above.
[8. Method for producing non-aqueous electrolyte]
As described above.

[II. Non-aqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention comprises a negative electrode and a positive electrode capable of occluding and releasing ions, and the non-aqueous electrolyte of the present invention.

<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.

  Alloy materials include metal oxides such as tin oxide and silicon oxide, metal composite oxides, lithium alloys such as lithium alone and lithium aluminum alloys, metals that can form alloys with lithium such as Sn and Si, and compounds thereof. That is. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The lithium-containing metal composite oxide material is not particularly limited as long as it can occlude and release lithium, but it preferably contains titanium and lithium as constituent components from the viewpoint of high current density charge / discharge characteristics.

<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. Moreover, 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 electrodeification method, the current collector, and the nonaqueous electrolyte secondary battery, any one of (1) to (21) below or It is desirable to satisfy multiple terms simultaneously.

(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 preferably 0.335 nm or more. It is 360 nm or less, preferably 0.350 nm or less, and more preferably 0.345 nm or less. Further, the crystallite size (Lc) of the carbonaceous material obtained by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, and more preferably 1.5 nm or more.

(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 caused by 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 ² · ^{g -1} or more, preferably 0.05 cm ² · ^{g -1} or more, more preferably 0.1 cm ² · ^{g -1} or more, Usually, it is desirable to have a pore size distribution of 0.6 cm ² · g ⁻¹ or less, preferably 0.4 cm ² · g ⁻¹ or less, more preferably 0.3 cm ² · 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 ² · g ⁻¹ or more, and 25 cm ² · ^{g -1} or more, more preferably 0.4 cm ² · ^{g -1} or higher, and is generally 10 cm ² · ^{g -1} or less, preferably ^{5 cm} 2 · ^{g -1} or less, ^{2 cm} 2 · g ^-1 or less is 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.

  As a particularly preferred example of mixing these secondary materials, the volume-based particle size distribution is not symmetrical when centered on the median diameter, containing two or more carbonaceous materials having different Raman R values, And 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 preferably 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 45% by mass or less. 40 mass% or less 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.

(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 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 metal thin film)
The thickness of the metal thin film is arbitrary, but 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 30 μm or less. If the thickness of the metal film is less than 1 μm, the strength may be reduced, making application difficult. Moreover, when it becomes thicker than 100 micrometers, the shape of electrodes, such as winding, may be changed. The metal thin film 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 ratios.

  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 solvents 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 ratios.

  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. The 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. The integrated intensities of the peaks of (110) diffraction and (004) diffraction are calculated. 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 the measurement is defined as the electrode plate 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 = 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

(19) Impedance The resistance of the negative electrode when charged from the discharged state to 60% of the nominal capacity is preferably 100Ω or less, more preferably 50Ω or less, particularly preferably 20Ω or less, and / or the double layer capacity is 1 × 10 ^{−. 6} F or more is preferable, 1 × 10 ⁻⁵ F or more is more preferable, and 1 × 10 ⁻⁴ F is particularly preferable. This is because the use of a negative electrode in the above range provides good output characteristics.

  The resistance and the double layer capacity of the negative electrode are measured by charging the lithium ion secondary battery to be measured at a current value at which the nominal capacity can be charged in 5 hours, and then maintaining the state without charging / discharging for 20 minutes. A capacitor whose capacity is 80% or more of the nominal capacity when discharged at a current value that can be discharged in one hour is used.

  About the lithium ion secondary battery of the above-mentioned discharge state, it charges to 60% of a nominal capacity with the electric current value which can charge a nominal capacity in 5 hours, and immediately transfers a lithium ion secondary battery in the glove box under argon gas atmosphere. . Here, the lithium ion secondary battery is quickly disassembled and taken out in a state where the negative electrode does not discharge or short-circuit, and if it is a double-sided coated electrode, the negative electrode active material on one side is peeled off without damaging the negative electrode active material on the other side. Two electrodes are punched out into a diameter of 12.5 mm, and are opposed to each other so that the surface of the negative electrode active material does not shift through a separator. 60μL of non-aqueous electrolyte used in the battery was dropped between the separator and both negative electrodes, and kept in close contact with the outside air, and the current collector of both negative electrodes was made conductive and the AC impedance method was carried out. To do.

The measurement is performed at a temperature of 25 ° C., and a complex impedance measurement is performed in a frequency band of 10 ⁻² to 10 ⁵ Hz. The surface resistance (R) is obtained by approximating the arc of the negative resistance component of the obtained Nyquist plot with a semicircle. The double layer capacity (Cdl) is determined.

(20) Area of negative electrode plate The area of the negative electrode plate is not particularly limited, but it may be designed to be slightly larger than the opposing positive electrode plate so that the positive electrode plate does not protrude from the negative electrode plate. preferable. From the viewpoint of suppressing the cycle life of repeated charge and discharge and deterioration due to high temperature storage, it is preferable to make it as close as possible to the area equal to the positive electrode because the characteristics are improved by increasing the proportion of the electrodes that work more uniformly and effectively. In particular, when the electrode is used at a large current, the design of the electrode area is important.

(21) Thickness of negative electrode plate The thickness of the negative electrode plate is designed according to the positive electrode plate to be used, and is not particularly limited, but is a composite layer obtained by subtracting the thickness of the metal foil of the core material. The thickness is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and usually 150 μm or less, preferably 120 μm or less, more preferably 100 μm or less.

<2-3-3. Alloy Material, and Structure, Physical Properties, and Preparation Method of Negative Electrode Using Alloy Material>
As an alloy material used as the negative electrode active material, as long as lithium can be occluded / released, simple metals and alloys that form lithium alloys, or oxides / carbides / nitrides / silicides / sulfides / phosphorous thereof. Any compound such as a compound is not particularly limited, but preferably a single metal or alloy that forms a lithium alloy includes a group 13 and group 14 metal / metalloid element (ie, excluding carbon). The material is preferably a single metal of aluminum, silicon, and tin (hereinafter sometimes referred to as “specific metal element”), and an alloy / compound containing these atoms.

  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, for 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, although the capacity per unit weight is inferior to that of a single metal or an alloy, the following compounds containing silicon and / or tin are also preferred because of excellent cycle characteristics.
The element ratio of silicon and / or tin to 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. Silicon and / or tin oxide of 3 or less, more preferably 1.1 or less.
-Element ratio of 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. Silicon and / or tin nitride of 3 or less, more preferably 1.1 or less.
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. Silicon and / or tin carbide of 3 or less, more preferably 1.1 or less.

  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 usually 70% by mass or more, particularly 75% by mass or more, and usually 97% by mass or less, and particularly preferably 95% by mass 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 mass or more, particularly 5% by mass or more, and usually 30% by mass or less, particularly 25% by mass 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 mass 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 a 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 (1). In the general formula (1), 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.

Li _x Ti _y MzO ₄ (1)
[In General Formula (1), 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 (1),
(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 of the present invention preferably further satisfies at least one of the characteristics such as physical properties and shapes shown in the following (1) to (15). It is particularly preferred to satisfy more than one species at the same time.

(1) BET specific surface area The BET specific surface area of a titanium-containing metal oxide (hereinafter referred to as “titanium-containing metal oxide” as appropriate) used as the negative electrode active material of the lithium ion secondary battery of the present invention is determined by the BET method. the value of the measured specific surface area using the, preferably 0.5 m ² · ^{g -1} or more, more preferably 0.7 m ² · ^{g -1} or more, more preferably 1.0 m ² · ^{g -1} or more, 1. 5 m ² · g ⁻¹ or more is particularly preferable, 200 m ² · g ⁻¹ or less is preferable, 100 m ² · g ⁻¹ or less is more preferable, 50 m ² · g ⁻¹ or less is further preferable, and 25 m ² · g ^{− 1} or less is particularly preferable.

  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 Volume-based average particle diameter of titanium-containing metal 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 titanium-containing metal 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, preferably 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.

  If the volume average particle size of the titanium-containing metal 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 be reduced. 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 In the case where primary particles are aggregated to form secondary particles, the average primary particle diameter of the titanium-containing metal oxide is usually 0.01 μm or more, and 0.05 μm or more. It is preferably 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.

  If the volume-based average primary particle diameter exceeds the above range, it is difficult to form spherical secondary particles, which adversely affects the powder packing 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 titanium-containing metal 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 titanium-containing metal 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 titanium-containing metal oxide of the present invention.

(6) Circularity When the circularity is measured as the spherical degree of the titanium-containing metal 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 titanium-containing metal oxide is preferably as close to 1 as possible, 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 titanium-containing metal oxide of the present invention.

(7) Aspect ratio The aspect ratio of the titanium-containing metal 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 titanium-containing metal oxide.

  The aspect ratio is measured by magnifying and observing titanium-containing metal 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 titanium-containing metal oxide of the present invention.

(8) Method for producing negative electrode active material The method for producing a titanium-containing metal 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 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 metal thin film)
The thickness of the metal thin film is arbitrary, but 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 30 μm or less. If the thickness of the metal film is less than 1 μm, the strength may be reduced, making application difficult. Moreover, when it becomes thicker than 100 micrometers, the shape of electrodes, such as winding, may be changed. The metal thin film 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・ Cm ⁻³ is more preferable, 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. The following is more preferable, 2.2 g · cm ⁻³ or less is further 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 ratios.

  Further, when a thickener is used, 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.

(14) Impedance The resistance of the negative electrode when charged from the discharged state to 60% of the nominal capacity is preferably 500Ω or less, more preferably 100Ω or less, particularly preferably 50Ω or less, and / or the double layer capacity is 1 × 10 ^{−. 6} F or more is preferable, 1 × 10 ⁻⁵ F or more is more preferable, and 3 × 10 ⁻⁵ F or more is particularly preferable. This is because the use of a negative electrode in the above range provides good output characteristics.

  The resistance and double layer capacity of the negative electrode are determined by maintaining the state where the lithium ion secondary battery to be measured is not charged / discharged for 20 minutes after being charged at a current value at which the nominal capacity can be charged in 5 hours. A capacitor whose capacity when discharged at a current value that can be discharged in one hour is 80% or more of the nominal capacity is used.

  About the lithium ion secondary battery of the above-mentioned discharge state, it charges to 60% of a nominal capacity with the electric current value which can charge a nominal capacity in 5 hours, and immediately transfers a lithium ion secondary battery in the glove box under argon gas atmosphere. . Here, the lithium ion secondary battery is quickly disassembled and taken out in a state where the negative electrode does not discharge or short-circuit, and if it is a double-sided coated electrode, the electrode active material on one side is peeled off without damaging the electrode active material on the other side, Two electrodes are punched out to a diameter of 12.5 mm and faced so as not to shift the active material surface through a separator. 60μL of non-aqueous electrolyte used in the battery was dropped between the separator and both negative electrodes, and kept in close contact with the outside air, and the current collector of both negative electrodes was made conductive and the AC impedance method was carried out. To do.

The measurement is performed at a temperature of 25 ° C. and a complex impedance measurement is performed in a frequency band of 10 ⁻² to 10 ⁵ Hz, and the arc of the negative resistance component of the obtained Nyquist plot is approximated by a semicircle to obtain a surface resistance (impedance Rct). The double layer capacitance (impedance Cdl) is obtained.

(15) Area of negative electrode plate The area of the negative electrode plate is not particularly limited, but it may be designed to be slightly larger than the opposing positive electrode plate so that the positive electrode plate does not protrude from the negative electrode plate. preferable. From the viewpoint of suppressing the cycle life of repeated charge and discharge and deterioration due to high temperature storage, it is preferable to make it as close as possible to the area equal to the positive electrode because the characteristics are improved by increasing the proportion of the electrodes that work more uniformly and effectively. In particular, when the electrode is used at a large current, the design of the electrode area is important.

(16) Thickness of negative electrode plate The thickness of the negative electrode plate is designed in accordance with the positive electrode plate used, and is not particularly limited, but is a composite layer obtained by subtracting the thickness of the metal foil of the core material. The thickness is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and usually 150 μm or less, preferably 120 μm or less, more preferably 100 μm or less.

<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 positive electrode 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.

V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable as the transition metal of the lithium transition metal composite oxide. Specific examples include lithium-cobalt composite oxides such as LiCoO ₂ and LiNiO ₂ . Lithium / nickel composite oxides, LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _{4 and} other lithium / manganese composite oxides, Al, Ti , V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and those substituted with other metals such as 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 less than the above range, diffusion of lithium ions in the positive electrode active material layer using the non-aqueous electrolyte solution 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. That is, when an active material, a conductive agent, a binder, or the like is slurried with a solvent and applied in a thin film shape, streaks may occur.

  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, and measuring the refractive index 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 of 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 of 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 polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitro Resin polymers such as cellulose; rubbery polymers such as SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene propylene rubber; styrene butadiene styrene block Copolymer or its hydrogenated product, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer or its hydrogenated product, etc. Thermoplastic Stoma-like polymers; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride (PVdF), Examples include 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). In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  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 Amides such as dimethylacetamide; aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide. 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 ratios.

  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, particularly preferably 2 g · cm ⁻³ or more, and preferably 4 g · cm ⁻³ or less. 3.5 g · cm ⁻³ or less is more preferable, and 3 g · cm ⁻³ or less is particularly preferable.

  If 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.

  The ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, but (the thickness of the active material layer on one side immediately before the nonaqueous electrolyte solution injection) / (thickness of the current collector) is usually 150 or less. It is preferably 20 or less, particularly preferably 10 or less, usually 0.1 or more, preferably 0.4 or more, and particularly preferably 1 or more. When the ratio of the thickness of the current collector to the positive 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 positive electrode active material may increase, and the battery capacity may decrease.

(8) Electrode area From the viewpoint of increasing the stability at high output and high temperature, the area of the positive electrode active material layer is preferably larger than the outer surface area of the battery outer case. Specifically, the total electrode area of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 20 times or more, and more preferably 40 times or more. The outer surface area of the outer case is the total area obtained by calculation from the vertical, horizontal, and thickness dimensions of the case part filled with the power generation element excluding the protruding part of the terminal in the case of a bottomed square shape. . In the case of a bottomed cylindrical shape, the geometric surface area approximates the case portion filled with the power generation element excluding the protruding portion of the terminal as a cylinder. The total electrode area of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and in the structure in which the positive electrode mixture layer is formed on both sides via the current collector foil. , The sum of the areas where each surface is calculated separately.

(9) Discharge capacity When the non-aqueous electrolyte for secondary battery of the present invention is used, the electric capacity of the battery element housed in one battery exterior of the secondary battery (the battery is discharged from a fully charged state to a discharged state) When the electric capacity is 3 ampere hours (Ah) or more, the effect of improving the low-temperature discharge characteristics is increased, which is preferable. Therefore, the positive electrode plate is designed so that the discharge capacity is fully charged and is usually 3 Ah (ampere hour), preferably 4 Ah or more, and usually 20 Ah or less, preferably 10 Ah or less.

  If it falls below the above range, the voltage drop due to the electrode reaction resistance becomes large when taking out a large current, and the power efficiency may deteriorate. If the above range is exceeded, the electrode reaction resistance is reduced and the power efficiency is improved, but the temperature distribution due to the internal heat generation of the battery during pulse charge / discharge is large, the durability of repeated charge / discharge is inferior, and overcharge and internal In some cases, the heat radiation efficiency is also deteriorated with respect to sudden heat generation at the time of abnormality such as a short circuit.

(10) Thickness of positive electrode plate The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity, high output, and high rate characteristics, the thickness of the composite layer obtained by subtracting the metal foil thickness of the core material The thickness is preferably 10 μm or more, more preferably 20 μm or more, more preferably 200 μm or less, and even more preferably 100 μm or less with respect to one side of the current collector.

<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 laminated structure described above, a structure in which the metal core portions of the electrode layers are bundled and welded to the terminals is preferably used. When the area of one electrode increases, the internal resistance increases. Therefore, it is also preferable to provide a plurality of terminals in the electrode to reduce the resistance. When the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures on the positive electrode and the negative electrode, respectively, and bundling the terminals.

  By optimizing the above structure, the internal resistance can be made as small as possible. In a battery used at a large current, the impedance measured by the 10 kHz AC method (hereinafter abbreviated as “DC resistance component”) is preferably 10 milliohms (mΩ) or less, and the DC resistance component is 5 milliohms (mΩ). It is more preferable to make it below.

  When the direct current resistance component is 0.1 milliohm (mΩ) or less, the high output characteristics are improved, but the ratio of the current collecting structure used increases and the battery capacity may decrease.

  The non-aqueous electrolyte of the present invention is effective in reducing reaction resistance related to lithium insertion / extraction with respect to the electrode active material, which is a factor that can realize good low-temperature discharge characteristics. However, in a battery having a normal DC resistance greater than 10 milliohms (mΩ), the effect of reducing reaction resistance may not be reflected 100% on the low-temperature discharge characteristics due to inhibition by the DC resistance. Therefore, this can be improved by using a battery having a small DC resistance component, and the effect of the non-aqueous electrolyte solution of the present invention can be sufficiently exhibited.

  Further, from the viewpoint of drawing out the effect of the non-aqueous electrolyte and producing a battery having high low-temperature discharge characteristics, this requirement and the electric capacity of the battery element housed in one battery exterior of the secondary battery described above. It is particularly preferable to satisfy the requirement that (the electric capacity when the battery is discharged from the fully charged state to the discharged state) is 3 ampere hours (Ah) or more at the same time.

[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, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples and comparative examples unless it exceeds the gist.

[Production of positive electrode]
92 parts by weight of lithium / transition metal composite oxide (LiNi _0.33 Mn _0.33 Co _0.33 O ₂ ) containing nickel, manganese and cobalt and 4 parts by weight of polyvinylidene fluoride (hereinafter referred to as “PVdF” as appropriate) A mixture obtained by mixing 4 parts by weight of acetylene black and adding N-methylpyrrolidone to form a slurry was applied to both surfaces of a current collector made of aluminum and dried to obtain a positive electrode.

[Manufacture of negative electrode]
A mixture of 92 parts by weight of graphite powder and 8 parts by weight of PVdF, and a slurry obtained by adding N-methylpyrrolidone was applied to one side of a current collector made of copper and dried to obtain a negative electrode.

[Manufacture of non-aqueous electrolyte secondary batteries]
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, the positive electrode, the separator, and the negative electrode. The battery element thus obtained was wrapped in a cylindrical aluminum laminate film, injected with an electrolyte described later, and then vacuum sealed to produce a sheet-like non-aqueous electrolyte secondary battery. Furthermore, in order to improve the adhesion between the electrodes, the sheet-like battery was sandwiched between glass plates and pressurized.

[Capacity evaluation]
In a constant temperature bath at 25 ° C., the sheet-like non-aqueous electrolyte secondary battery was charged at a constant current-constant voltage (hereinafter referred to as “CCCV charge” as appropriate) to 0.2 V at 0.2 C, and then 2 at 0.2 C. Discharged to .75V. This was repeated three times, and after conditioning, the CCCV charge was again performed at 0.2 C to 4.4 V, and the discharge was again performed at 1 C to 2.75 V to obtain the initial discharge capacity. The cut-off current during charging was set to 0.05C in all cases. In addition, 1C is a current value when discharging the entire capacity of the battery in one hour.

[4.4V continuous charge characteristics evaluation]
The battery for which the capacity evaluation test was completed was placed in a constant temperature bath at 60 ° C., charged at a constant current of 0.2 C, and switched to constant voltage charging when it reached 4.4V. After charging for 14 days, the battery was cooled to 25 ° C. Next, the battery was immersed in an ethanol bath and the buoyancy was measured (Archimedes principle), and the amount of gas generated was determined from the buoyancy. In addition, in order to evaluate the degree of capacity deterioration after continuous charging, first discharge to 3V at 0.2C, then CCCV charge to 4.4V at 0.2C, and further discharge to 2.75V at 1C. The discharge capacity (recovery capacity) was measured, and the capacity retention rate after continuous charging was determined according to the following formula. A larger value indicates less battery deterioration.

Capacity maintenance rate after 7 days of continuous charging (%)
= (Recovery capacity after 7 days of continuous charge / initial discharge capacity) x 100

Example 1
LiPF _{6 as} an electrolyte is mixed with a mixed solvent of ethylene carbonate (EC) as a cyclic carbonate and ethyl methyl carbonate (EMC) as a chain carbonate (mixing volume ratio 2: 8, weight ratio 24.7: 75.3). Was dissolved at a rate of 1 mol / L as a base electrolyte (I), and 1,4,8,11-tetraazacyclotetradecane and vinylene carbonate (VC) were added to the base electrolyte (I) in a non-aqueous system. Using the non-aqueous electrolyte solution added so that the concentration with respect to the electrolyte solution is 0.1% by mass and 1% by mass, respectively, a non-aqueous electrolyte secondary battery is manufactured according to the above-described method, and capacity evaluation and 4.4V are performed. Continuous charging characteristics were evaluated. The results are shown in Table 1.

Example 2
1,4,8,11-tetraazacyclotetradecane and fluoroethylene carbonate (FEC) are added to the base electrolyte (I) so that the concentration with respect to the non-aqueous electrolyte is 0.1% by mass and 1% by mass, respectively. Using the added non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced according to the method described above, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 3
In the base electrolyte (I), 1,4,8,11-tetraazacyclotetradecane and lithium difluorophosphate (LiPO ₂ F ₂ ) were added at a concentration of 0.1% by mass and 0.5% with respect to the non-aqueous electrolyte, respectively. A non-aqueous electrolyte secondary battery was prepared according to the above-described method using the non-aqueous electrolyte added so as to be in mass%, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 4
1,4,8,11-tetraazacyclotetradecane was added to the base electrolyte (I) so that the concentration with respect to the non-aqueous electrolyte was 0.02% by mass to obtain a non-aqueous electrolyte. Using the obtained non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced according to the above-described method, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 5
As described above, a non-aqueous electrolyte solution in which 1,4,8,11-tetraazacyclotetradecane was added to the base electrolyte solution (I) so that the concentration with respect to the non-aqueous electrolyte solution was 0.05% by mass was used. A non-aqueous electrolyte secondary battery was prepared according to the method, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 6
As described above, a non-aqueous electrolyte solution in which 1,4,8,11-tetraazacyclotetradecane was added to the base electrolyte solution (I) so that the concentration with respect to the non-aqueous electrolyte solution was 0.1% by mass was used. A non-aqueous electrolyte secondary battery was prepared according to the method, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 7
As described above, a non-aqueous electrolyte solution in which 1,4,7,10-tetraazacyclododecane was added to the base electrolyte solution (I) so as to have a concentration of 0.1% by mass with respect to the non-aqueous electrolyte solution was used. A non-aqueous electrolyte secondary battery was prepared according to the method, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 8
1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane is added to the base electrolyte (I) so that the concentration with respect to the non-aqueous electrolyte is 0.1% by mass Using the non-aqueous electrolyte solution, a non-aqueous electrolyte secondary battery was produced according to the method described above, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 9
A nonaqueous electrolytic solution obtained by adding 1,4,8,11-tetraazacyclotetradecane-5,7-dione to the base electrolytic solution (I) so that the concentration with respect to the nonaqueous electrolytic solution is 0.1% by mass. A non-aqueous electrolyte secondary battery was prepared according to the method described above, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 10
According to the above-described method, a non-aqueous electrolyte solution in which cyclo (β-alanylglycyl-β-alanylglycyl) was added to the base electrolyte solution (I) so that the concentration with respect to the non-aqueous electrolyte solution was 0.02% by mass was used. A non-aqueous electrolyte secondary battery was prepared, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 11
LiPF _{6 as} an electrolyte was mixed with a mixed solvent of ethylene carbonate (EC) as a cyclic carbonate and ethyl methyl carbonate (EMC) as a chain carbonate (mixing volume ratio 1: 9, weight ratio 12.7: 87.3). Was dissolved at a rate of 1 mol / L as the base electrolyte (II), and 1,4,8,11-tetraazacyclotetradecane was added to the base electrolyte (II) at a concentration of 0 with respect to the non-aqueous electrolyte. In addition, a non-aqueous electrolyte was added so as to be 1% by mass. Using the obtained non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced according to the above-described method, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 12
LiPF, which is an electrolyte, in a mixed solvent of fluoroethylene carbonate (FEC), which is a cyclic carbonate, and ethyl methyl carbonate (EMC), which is a chain carbonate (mixing volume ratio 1: 9, weight ratio 14.2: 85.8). ₆ was dissolved at a rate of 1 mol / L as a base electrolyte (III), and 1,4,8,11-tetraazacyclotetradecane was added to this base electrolyte (III) at a concentration of non-aqueous electrolyte. A non-aqueous electrolyte was added to the content of 0.1% by mass. Using the obtained non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced according to the above-described method, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 13
LiPF _{6 as} an electrolyte was mixed with a mixed solvent of ethylene carbonate (EC) as a cyclic carbonate and ethyl methyl carbonate (EMC) as a chain carbonate (mixing volume ratio 3: 7, weight ratio 36.0: 64.0). Was dissolved at a rate of 1 mol / L as a base electrolyte (IV), and 1,4,8,11-tetraazacyclotetradecane was added to this base electrolyte (IV) at a concentration of 0 with respect to the non-aqueous electrolyte. In addition, a non-aqueous electrolyte was added so as to be 1% by mass. Using the obtained non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced according to the above-described method, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 14
LiPF _{6 as} an electrolyte is mixed with a mixed solvent of ethylene carbonate (EC) as a cyclic carbonate and ethyl methyl carbonate (EMC) as a chain carbonate (mixing volume ratio 4: 6, weight ratio 46.7: 53.4). Was dissolved at a rate of 1 mol / L as a base electrolyte (V), and 1,4,8,11-tetraazacyclotetradecane-5,7-dione was added to this base electrolyte (V) in a non-aqueous system. A non-aqueous electrolyte was added in such a way that the concentration with respect to the electrolyte was 0.1% by mass. Using the obtained non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced according to the above-described method, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Example 15
A ratio of 1 mol / L of LiPF ₆ as an electrolyte to a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) as a cyclic carbonate (mixing volume ratio 5: 5, weight ratio 52.4: 47.6). The base electrolyte (VI) was dissolved in this solution, and 1,4,8,11-tetraazacyclotetradecane-5,7-dione was added to the base electrolyte (VI) at a concentration of 0 with respect to the non-aqueous electrolyte. In addition, a non-aqueous electrolyte was added so as to be 1% by mass. Using the obtained non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced according to the above-described method, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1. When a cyclic polyamide compound is added, it turns out that there is no restriction | limiting in the weight ratio of the cyclic carbonate which can be used as a solvent.

Comparative Example 1
Using the base electrolyte (I) itself, a non-aqueous electrolyte secondary battery was prepared according to the method described above, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Comparative Example 2
LiPF _{6 as} an electrolyte is mixed with a mixed solvent of ethylene carbonate (EC) as a cyclic carbonate and ethyl methyl carbonate (EMC) as a chain carbonate (mixing volume ratio 35:65, weight ratio 41.4: 58.6). Was dissolved at a rate of 1 mol / L as the base electrolyte (VII), and 1,4,8,11-tetraazacyclotetradecane was added to the base electrolyte (VII) at a concentration of 0 with respect to the non-aqueous electrolyte. In addition, a non-aqueous electrolyte was added so as to be 1% by mass. Using the obtained non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced according to the above-described method, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

Comparative Example 3
LiPF _{6 as} an electrolyte is mixed with a mixed solvent of ethylene carbonate (EC) as a cyclic carbonate and ethyl methyl carbonate (EMC) as a chain carbonate (mixing volume ratio 4: 6, weight ratio 46.7: 53.4). Was dissolved at a rate of 1 mol / L as the base electrolyte (V), and 1,4,8,11-tetraazacyclotetradecane was added to the base electrolyte (V) at a concentration of 0 with respect to the non-aqueous electrolyte. In addition, a non-aqueous electrolyte was added so as to be 1% by mass. Using the obtained non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced according to the above-described method, and capacity evaluation and 4.4 V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

The symbols of the cyclic polyamine compound or cyclic polyamide compound in Table 1 are as follows.
cyclam:
1,4,8,11-tetraazacyclotetradecane cyclen:
1,4,7,10-Tetraazacyclododecane TM-cyclam:
1,4,8,11-Tetramethyl-1,4,8,11-tetraazacyclotetradecane DO-cyclam:
1,4,8,11-tetraazacyclotetradecane-5,7-dione TetO-cyclam:
Cyclo (β-alanylglycyl-β-alanylglycyl)

In Table 1, “at least one compound selected from the group consisting of unsaturated carbonates, fluorine-containing carbonates, monofluorophosphates and difluorophosphates” is referred to as “specific compound”, and the symbol of “specific compound” is as follows: Street.
VC : Vinylene carbonate FEC : Fluoroethylene carbonate LiPO ₂ F ₂ : Lithium difluorophosphate

  As apparent from Table 1 above, the continuous charge characteristics were improved by using the non-aqueous electrolyte solution according to the present invention (Examples 1 to 15). On the other hand, the non-aqueous electrolyte solution according to the present invention (non-aqueous electrolyte solution that does not correspond to any of Embodiment 1, Embodiment 2, and Embodiment 3) had poor continuous charge characteristics (Comparative Examples 1 to 3). In addition, as in Comparative Example 2 and Comparative Example 3, when the non-aqueous organic solvent contained a cyclic polyamine compound and further contained a cyclic carbonate exceeding 40% by mass, the continuous charge characteristics were inferior.

  Since the non-aqueous electrolyte secondary battery using the non-aqueous electrolyte of the present invention maintains a high capacity and is excellent in continuous charge characteristics and the like, it can be used for various known applications. Specific examples include, for example, 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. , Walkie Talkie, Electronic Notebook, Calculator, Memory Card, Portable Tape Recorder, Radio, Backup Power Supply, Motor, Car, Motorcycle, Motorbike, Bicycle, Lighting Equipment, Toy, Game Equipment, Clock, Electric Tool, Strobe, Camera, etc. Can be mentioned.

Claims (8)

  A nonaqueous electrolytic solution comprising a lithium salt and a nonaqueous organic solvent for dissolving the lithium salt, wherein the nonaqueous organic solvent contains a cyclic polyamine compound and / or a cyclic polyamide compound, and further contains an unsaturated carbonate, fluorine A non-aqueous electrolyte containing at least one compound selected from the group consisting of carbonates, monofluorophosphates and difluorophosphates.   A non-aqueous electrolyte solution comprising a lithium salt and a non-aqueous organic solvent for dissolving the lithium salt, wherein the non-aqueous organic solvent contains a cyclic polyamine compound, and the cyclic carbonate is added to the whole non-aqueous organic solvent. A non-aqueous electrolyte containing 5% by mass to 40% by mass.   A non-aqueous electrolyte solution comprising a lithium salt and a non-aqueous organic solvent for dissolving the lithium salt, wherein the non-aqueous organic solvent contains a cyclic polyamide compound.   The nonaqueous electrolytic solution according to any one of claims 1 to 3, comprising at least one cyclic carbonate selected from the group consisting of ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, propylene carbonate, and butylene carbonate. .   The cyclic polyamine compound is 1,4,7-triazacyclononane, 1,5,9-triazacyclododecane, 1,4,7,10-tetraazacyclododecane, 1,4,8,11-tetra. The at least one compound selected from the group consisting of azacyclotetradecane and 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane. The non-aqueous electrolyte solution according to claim 4.   Cyclic polyamide compounds are 1,4,7,10-tetraazacyclotridecane-11,13-dione, 1,4,8,11-tetraazacyclotetradecane-5,7-dione, 1,4,8, 5. The compound according to claim 1, which is at least one compound selected from the group consisting of 12-tetraazacyclopentadecane-9,11-dione and cyclo (β-alanylglycyl-β-alanylglycyl). The non-aqueous electrolyte solution according to claim 1.   The nonaqueous electrolytic solution according to any one of claims 1 to 6, wherein the cyclic polyamine compound and / or the cyclic polyamide compound is contained in an amount of 0.001% by mass to 5% by mass with respect to the entire nonaqueous electrolytic solution.   A non-aqueous electrolyte secondary battery using the non-aqueous electrolyte solution according to any one of claims 1 to 7.