JP2015072858A - Nonaqueous electrolytic solution, electrolytic solution for lithium ion secondary batteries, and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a nonaqueous electrolytic solution which enables the materialization of a nonaqueous secondary battery having both of the durability and the withstand voltage performance; an electrolytic solution for lithium ion secondary batteries; and a lithium ion secondary battery including the nonaqueous electrolytic solution or the electrolytic solution for lithium ion secondary batteries.SOLUTION: A nonaqueous electrolytic solution comprises: a silicon-containing compound arranged by substituting, with a silicon-containing functional group, at least one hydrogen atom of at least one compound selected from a group consisting of an inorganic acid, an organic acid, an acid amide, and amine; a lithium salt; a nonaqueous solvent; at least one salt selected from a group consisting of (1)a nitrate or nitrite, (2)a salt in which at least one halogen atom or alkyl halide binds to phosphorus, and (3)a carboxylate having 1-5 carbon atoms; and at least one compound selected from a group consisting of hydrofluoric acid and alcohol.

Description

  The present invention relates to a non-aqueous electrolyte, an electrolyte for a lithium ion secondary battery, and a lithium ion secondary battery including the non-aqueous electrolyte or the electrolyte for a lithium ion secondary battery.

  With the recent development of electronic technology and increasing interest in environmental technology, various electrochemical devices have been developed. In particular, there is a strong demand for the development of electrochemical devices for the purpose of energy saving, and expectations for electrochemical devices that can contribute to energy saving are increasing. Examples of such electrochemical devices include solar cells as power generation devices, and secondary batteries, capacitors, capacitors, and the like as power storage devices. Lithium ion secondary batteries, which are representative examples of power storage devices, have been conventionally used mainly as rechargeable batteries for portable devices, but in recent years, they are also expected to be used as batteries for hybrid vehicles and electric vehicles.

A lithium ion secondary battery generally has a configuration in which a positive electrode and a negative electrode mainly composed of an active material capable of inserting and extracting lithium are arranged via a separator. The positive electrode of the lithium ion secondary battery includes LiCoO ₂ , LiNiO ₂ or LiMn ₂ O ₄ as a positive electrode active material, carbon black or graphite as a conductive agent, and polyvinylidene fluoride, latex or rubber as a binder. Are mixed with a positive electrode current collector made of aluminum or the like. The negative electrode is a negative electrode current collector made of copper or the like mixed with a negative electrode mixture in which coke or graphite as a negative electrode active material and polyvinylidene fluoride, latex, rubber, or the like as a binder are mixed. Formed. Further, the separator is made of porous polyolefin or the like, and its thickness is very thin, from several μm to several hundred μm. The positive electrode, the negative electrode, and the separator are immersed in the electrolytic solution in the battery. Examples of the electrolytic solution include an electrolytic solution in which a lithium salt such as LiPF ₆ or LiBF ₄ is dissolved in an aprotic solvent such as propylene carbonate or ethylene carbonate, or a polymer such as polyethylene oxide.

  Currently, lithium ion secondary batteries are mainly used as batteries for portable devices and the like. In recent years, it has also begun to be used as a battery for automobiles such as hybrid cars and electric cars, and the use and market of lithium ion secondary batteries tend to further expand.

  As a component of such a non-aqueous electrolyte for a lithium ion secondary battery, an unsaturated bond carbonate compound typified by vinylene carbonate or a fluorine-containing typified by 4-fluoro-1,3-dioxolan-2-one Carbonate compounds are widely used. These compounds are very useful as materials that contribute to the control of the electrode interface and can contribute to the suppression of redox decomposition of the electrolyte.

  The electrode interface control ability (hereinafter also referred to as “SEI formation ability”) is a performance required for all lithium ion batteries. Generally, on the negative electrode surface of a battery, a decomposition product of a non-aqueous electrolyte called Solid Electrolyte Interface (SEI) plays a role as a protective film, and various additives that can form excellent SEI forming agents have been proposed. . When good SEI is formed, reductive decomposition of the nonaqueous electrolytic solution can be suppressed, and charging / discharging of the battery can be performed stably. It has been reported that non-aqueous electrolytes using vinylene carbonate or 4-fluoro-1,3-dioxolan-2-one can form such SEI (see, for example, Patent Document 1 and Patent Document 2). Also, specific phosphates, nitrates, and carboxylates are attracting attention because good SEI serves as a forming agent and contributes to improving battery characteristics (see, for example, Patent Document 3 and Patent Document 4).

  The specific salt can improve the cycle characteristics, high-temperature storage characteristics, and output characteristics of the battery by forming good SEI on the electrode. Moreover, this phosphate is further useful in that the effect can be obtained even by adding a very small amount of several tens of ppm.

  By the way, in recent years, a battery having a high energy density is required in order to enable long-time use of a smart phone and long-distance driving of an electric vehicle. For this purpose, a battery driven at a high voltage is indispensable. However, when a conventional non-aqueous electrolyte is used under a high voltage, the non-aqueous electrolyte is oxidized and decomposed, resulting in significant battery deterioration. Here, it is known that the voltage resistance of the electrolytic solution is improved by using a fluorine-containing carbonate compound, a nitrile compound, a phosphoric acid compound, a silicon-containing compound, or the like as the electrolytic solution component. (For example, see Patent Document 5, Patent Document 6, Patent Document 7, and Patent Document 8).

JP 2006-196250 A JP 2002-343430 A Japanese Patent Laid-Open No. 11-67270 JP 2007-165294 A JP 2012-123989 A JP 2010-244502 A International Publication 2012/77712 JP 2000-223152 A

  As described above, it has been reported that the withstand voltage of an electrolytic solution is improved by using a specific electrolytic solution forming component. Silicon compounds that have been reported to be usable at higher voltages, and specific phosphates, nitrates, and carboxylates that are effective in smaller amounts are very promising. However, when a certain amount or more of both the silicon-containing compound and the specific salt is used, there is a problem that decomposition gas is generated during charging and discharging to destabilize charging and discharging, and the amount added cannot be increased. Since various types of deterioration occur in a high-voltage battery, it is considered effective to suppress deterioration by using a plurality of additives and a plurality of technologies in combination.

  The present invention has been made in view of the above problems, and provides a non-aqueous electrolyte that realizes a non-aqueous secondary battery having both durability and withstand voltage performance, an electrolyte for a lithium ion secondary battery, and the above-mentioned It aims at providing the lithium ion secondary battery containing the non-aqueous electrolyte or the said electrolyte solution for lithium ion secondary batteries.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by containing a silicon-containing compound and a predetermined salt, and have completed the present invention. . That is, the present invention is as follows.

[1]
A silicon-containing compound in which one or more hydrogen atoms of one or more compounds selected from the group consisting of inorganic acids, organic acids, acid amides, and amines are substituted with silicon-containing functional groups;
Lithium salt,
A non-aqueous solvent;
(1) Nitrate or nitrite, (2) a salt in which one or more halogen atoms or alkyl halide is bonded to phosphorus, and (3) a carboxylate having 1 to 5 carbon atoms. One or more salts,
One or more selected from the group consisting of hydrofluoric acid and alcohol;
A non-aqueous electrolyte.
[2]
The nonaqueous electrolytic solution according to [1], wherein the salt is at least one selected from the group consisting of nitrate, monofluorophosphate, and difluorophosphate.
[3]
The nonaqueous electrolytic solution according to [1], wherein the salt is at least one selected from the group consisting of lithium monofluorophosphate and lithium difluorophosphate.
[4]
The nonaqueous electrolytic solution according to [3] above, wherein the lithium monofluorophosphate and / or the lithium difluorophosphate is produced in the nonaqueous electrolytic solution.
[5]
The silicon-containing compound in which one or more hydrogen atoms of one or more compounds selected from the group consisting of an inorganic acid containing boron or phosphorus, a carboxylic acid, and a phosphoric acid amide are substituted with a silicon-containing functional group The non-aqueous electrolyte solution according to any one of [1] to [4] above.
[6]
The silicon-containing compound is a silicon-containing compound in which one or more hydrogen atoms of one or more compounds selected from the group consisting of an inorganic acid containing phosphorus, a carboxylic acid, and a phosphoric acid amide are substituted with a silicon-containing functional group. The nonaqueous electrolytic solution according to any one of [1] to [4] above.
[7]
The nonaqueous electrolytic solution according to any one of [1] to [6], wherein the nonaqueous solvent includes an aprotic solvent.
[8]
An electrolyte solution for a lithium ion secondary battery, comprising the nonaqueous electrolyte solution according to any one of [1] to [7].
[9]
The non-aqueous electrolyte according to any one of [1] to [7] above, or the electrolyte for a lithium ion secondary battery according to [8] above,
A positive electrode;
A negative electrode,
With
The positive electrode contains one or more positive electrode active materials capable of inserting and extracting lithium ions,
The negative electrode contains one or more negative electrode active materials selected from the group consisting of a material capable of inserting and extracting lithium ions and metallic lithium,
Lithium ion secondary battery.
[10]
The lithium ion secondary battery according to [9], wherein the positive electrode active material includes a lithium-containing compound.
[11]
The lithium ion secondary battery according to [9] or [10], wherein the positive electrode active material includes a lithium-containing compound having a layered structure or a lithium-containing compound having a spinel structure.
[12]
The negative electrode active material includes at least one material selected from the group consisting of metallic lithium, a carbon material, a silicon material, and a material containing an element capable of forming an alloy with lithium, according to the above [9] to [11] The lithium ion secondary battery according to any one of the above.
[13]
The lithium ion secondary battery according to any one of [9] to [12], wherein an upper limit voltage of charging is 4.3 V or more.

  According to the present invention, a non-aqueous electrolyte that realizes a non-aqueous secondary battery having both durability and withstand voltage performance, an electrolyte for a lithium ion secondary battery, and the non-aqueous electrolyte or the lithium ion secondary A lithium ion secondary battery containing a battery electrolyte can be provided.

  Hereinafter, a mode for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. Deformation is possible.

[Non-aqueous electrolyte]
The non-aqueous electrolyte according to this embodiment is
A silicon-containing compound in which one or more hydrogen atoms of one or more compounds selected from the group consisting of inorganic acids, organic acids, acid amides, and amines are substituted with silicon-containing functional groups;
Lithium salt,
A non-aqueous solvent;
(1) Nitrate or nitrite, (2) a salt in which one or more halogen atoms or alkyl halide is bonded to phosphorus, and (3) a carboxylate having 1 to 5 carbon atoms. One or more salts,
One or more selected from the group consisting of hydrofluoric acid and alcohol.

  By combining a silicon-containing compound, a predetermined salt, and one or more selected from the group consisting of hydrofluoric acid and alcohol, durability and withstand voltage performance can be obtained even when used in a high-voltage drive battery. The non-aqueous electrolyte which has both can be provided.

[Silicon-containing compound]
The nonaqueous electrolytic solution according to the present embodiment includes a silicon-containing compound. The silicon-containing compound is a silicon-containing compound in which one or more hydrogen atoms of one or more compounds selected from the group consisting of inorganic acids, organic acids, acid amides, and amines are substituted with silicon-containing functional groups. A compound having such a structure exhibits the effect of protecting the positive electrode by the effect of the silicon-containing functional group and other sites, and the oxidation and side reaction of the electrolyte solvent, salt and other additives on the positive electrode, Elution of substance components into the electrolyte can be suppressed. Thereby, a battery characteristic improves more.

(Inorganic acid)
Although it does not specifically limit as an inorganic acid, For example, the inorganic acid containing nonmetallic elements, such as a boron, a fluorine, chlorine, a bromine, an iodine, sulfur, selenium, tellurium, nitrogen, phosphorus, or arsenic, is mentioned. Among these, an inorganic acid containing boron, sulfur, phosphorus, or nitrogen is preferable, an inorganic acid containing boron or phosphorus is more preferable, and phosphoric acid, phosphorous acid, polyphosphoric acid, or boric acid is more preferable. By using a compound in which one or more hydrogen atoms of an inorganic acid containing boron or phosphorus are substituted with a silicon-containing functional group, the effect of protecting the positive electrode is further improved, and the electrolyte solvent, salt, and other additives Oxidation and side reactions on the positive electrode and elution of the positive electrode active material component into the electrolyte solution tend to be further suppressed. Thereby, the battery characteristics tend to be further improved.

(Organic acid)
Although it does not specifically limit as an organic acid, For example, the compound which has 1 or more types of sulfonic acid or a carboxylic acid site | part is mentioned. Among these, carboxylic acid is preferable. By using a compound in which one or more hydrogen atoms of the carboxylic acid are substituted with a silicon-containing functional group, the effect of protecting the positive electrode is further improved, and the electrolyte solvent, salt and other additives are oxidized on the positive electrode. And side reactions and elution of the positive electrode active material component into the electrolyte solution tend to be further suppressed. Thereby, the battery characteristics tend to be further improved.

  The sulfonic acid is not particularly limited. For example, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, acrylic acid sulfonic acid, vinylsulfonic acid, benzenesulfonic acid, alkylbenzenesulfonic acid, toluenesulfonic acid, fluoro And sulfonic acid.

  The carboxylic acid is not particularly limited. For example, acetic acid, trifluoroacetic acid, propionic acid, butyric acid, valeric acid, acrylic acid, methacrylic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid, phthalic acid, isophthalic acid, Examples include terephthalic acid, salicylic acid, malonic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, and itaconic acid. Of these, dicarboxylic acids such as benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, malonic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, and itaconic acid are preferred, and adipic acid, itaconic acid, succinic acid, etc. Acid, malonic acid, benzoic acid, isophthalic acid, and terephthalic acid are more preferable, and adipic acid, itaconic acid, succinic acid, isophthalic acid, and terephthalic acid are more preferable.

(Acid amide)
The acid amide is not particularly limited, but examples thereof include N-alkyl substituted or unsubstituted acetamide and carboxylic acid amides represented by N-alkyl substituted or unsubstituted formamide; sulfonic acid amide, N-alkyl substituted or unsubstituted Examples thereof include phosphoric acid amides represented by phosphoric acid monoamides, N-alkyl-substituted or unsubstituted phosphoric acid diamides, and N-alkyl-substituted or unsubstituted phosphoric acid triamides. Among these, N alkyl substituted carboxylic acid amide or N alkyl substituted phosphoric acid triamide is preferable. Moreover, phosphoric acid amide is preferable. By using a compound in which one or more hydrogen atoms of phosphoric acid amide are substituted with a silicon-containing functional group, the effect of protecting the positive electrode is further improved, and oxidation of the electrolyte solvent, salt and additives on the positive electrode can be achieved. It tends to be possible to further suppress side reactions and elution of the positive electrode active material component into the electrolyte. It also has a function of removing unnecessary acid content in the battery. Thereby, the battery characteristics tend to be further improved.

(Amine)
Although it does not specifically limit as an amine, For example, a primary amine, a secondary amine, a tertiary amine, and a quaternary ammonium salt are mentioned. Among these, a secondary amine or a tertiary amine is preferable.

  Among inorganic acids, organic acids, acid amides or amines, inorganic acids or organic acids are preferable. By using a compound in which one or more hydrogen atoms of an inorganic acid or an organic acid are substituted with a silicon-containing functional group, oxidation or side reaction of the electrolyte solvent, salt and additive on the positive electrode, There is a tendency that the ability to suppress elution into the electrolyte is more excellent.

  The silicon compound of this embodiment may contain one or two or more inorganic acid, organic acid, acid amide, or amine sites.

(Silicon-containing functional group)
Although it does not specifically limit as a silicon-containing functional group, For example, the functional group which has one or more site | parts represented by -Si (R < ¹ >) (R < ² >) (R < ³ >) is mentioned. Here, one or more of R ¹ to R ³ is a halogen-substituted or unsubstituted, saturated or unsaturated, preferably a hydrocarbon group having 1 to 20 carbon atoms, two of R ¹ to R ³ The above is more preferably a halogen-substituted or unsubstituted, saturated or unsaturated, hydrocarbon group having 1 to 20 carbon atoms.

  The halogen-substituted or unsubstituted saturated or unsaturated hydrocarbon group is not particularly limited, and examples thereof include alkyl groups, alkenyl groups, alkynyl groups, allyl groups, alkoxy groups, alkylthio groups, N-substituted alkyl groups, and F-substituted alkyls. Group, F-substituted alkoxy group, vinyl group, acrylic group and methacryl group.

Two or more Rs out of R ^{1 to} R ³ may be bonded to form a ring. In the case of forming a ring, for example, two of R ^{1 to} R ³ represent a halogen-substituted or unsubstituted, saturated or unsaturated, common alkylene group.

Among R ^{1 to} R ³ , the functional group other than the halogen-substituted or unsubstituted saturated or unsaturated hydrocarbon group is not particularly limited, and examples thereof include a hydrogen atom, a halogen atom, a hydroxyl group, an amino group, a mercapto group, Examples thereof include a sulfide group.

  The silicon-containing compound is not particularly limited. For example, among the hydrogen atoms possessed by inorganic acids, organic acids, acid amides or amines, the remaining hydrogen atoms not substituted with silicon-containing functional groups are silicon-free functional groups. It may be a substituted compound.

(Functional group containing no silicon)
Such a silicon-free functional group is not particularly limited, and examples thereof include halogen-substituted or unsubstituted, saturated or unsaturated, hydrocarbon groups having 1 to 20 carbon atoms. Such hydrocarbon groups are not particularly limited, and examples thereof include alkyl groups, alkenyl groups, alkynyl groups, allyl groups, alkoxy groups, alkylthio groups, N-substituted alkyl groups, F-substituted alkyl groups, F-substituted alkoxy groups, vinyls. Group, acrylic group, and methacryl group.

  Further, a silicon-free functional group that replaces two or more hydrogen atoms may be bonded to form a ring. In the case of forming a ring, for example, two silicon-free functional groups represent a substituted or unsubstituted, saturated or unsaturated, common alkylene group.

  Although it does not specifically limit as a silicon-containing compound, The compound which substituted one or more of the hydrogen atoms which an inorganic acid or an organic acid has with the siliconization containing functional group is preferable, and it has an inorganic acid containing boron or phosphorus, or a carboxylic acid A compound in which one or more hydrogen atoms are substituted with a silicon-containing substituent is more preferable, and an inorganic acid containing boron or phosphorus, or a compound in which two or more hydrogen atoms of a carboxylic acid are substituted with a silicon-containing substituent is more preferable. .

  Such a silicon-containing compound is not particularly limited. For example, tris (trimethylsilyl) phosphoric acid, tris (trimethylsilyl) phosphorous acid, trimethylsilylpolyphosphoric acid, tris (trimethylsilyl) boric acid, tris (triethylsilyl) phosphoric acid, Trimethylsilylacetic acid, bis (trimethylsilyl) succinic acid, bis (trimethylsilyl) malonic acid, bis (trimethylsilyl) adipic acid, bis (trimethylsilyl) isophthalic acid, bis (trimethylsilyl) terephthalic acid, bis (triethylsilyl) malonic acid, bis (triethylsilyl) ) Adipic acid, bis (triethylsilyl) itaconic acid, bis (triethylsilyl) fumaric acid, bis (trimethylsilyl) succinic acid, bis (trimethylsilyl) oxalic acid, N, O-bis (trimethylsilyl) Acetamide is mentioned.

Although content of a silicon-containing compound is not specifically limited, 0.1-20 mass% is preferable with respect to 100 mass% of non-aqueous electrolyte, 0.1-15 mass% is more preferable, 0.5-10 mass % Is more preferable. When the content is within the above range, it tends to be possible to obtain a battery having superior oxidation resistance and a higher positive electrode potential and battery voltage. The content of these silicon-containing compounds in the electrolytic solution can be confirmed by NMR measurements such as ¹ H-NMR, ¹³ C-NMR, ²⁹ Si-NMR, ³¹ P-NMR. In addition, the content of the silicon-containing compound in the electrolyte solution in the lithium ion secondary battery is also measured by NMR measurement such as ¹ H-NMR, ¹³ C-NMR, ²⁹ Si-NMR, ³¹ P-NMR, as described above. Can be confirmed.

[Lithium salt]
The nonaqueous electrolytic solution according to the present embodiment contains a lithium salt. Although it does not specifically limit as lithium salt, For example, the inorganic lithium salt which does not contain a carbon atom in an anion, and the organic lithium salt which contains a carbon atom in an anion are mentioned. In addition, as lithium salt, inorganic lithium salt or organic lithium salt may be used individually by 1 type, or these may be used together.

Although it does not specifically limit as said inorganic lithium salt, For example, what is used as a normal nonaqueous electrolyte can be used. Such an inorganic lithium salt is not particularly limited. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , Li ₂ B ₁₂ F _b H _{12 -b} (b is an integer of 0 to 3), a lithium salt bonded to a polyvalent anion, and the like. These inorganic lithium salts may be used alone or in combination of two or more. Among these, one or more inorganic lithium salts selected from the group consisting of LiPF ₆ and LiBF ₄ are more preferable, and LiPF ₆ is more preferable. By using an inorganic lithium salt having a fluorine atom, the balance of battery characteristics tends to be more excellent. Further, by using an inorganic lithium salt having a phosphorus atom or a boron atom, ion conductivity and handleability tend to be more excellent.

Although it does not specifically limit as said organic lithium salt, For example, what is used as a normal nonaqueous electrolyte can be used. Such an organic lithium salt is not particularly limited. For example, LiN (SO ₂ C _m F _{2m + 1} ) ₂ (LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) _2, etc. m organolithium salt represented by an integer of 1 to _{8); LiPF n (C p F} 2p + 1) 6-n (n is an integer of from 1 to 5 such as LiPF ₅ (CF _3), p is 1 An organic lithium salt represented by LiBF _q (C _s F _{2s + 1} ) _4-q (q is an integer of 1 to 3, s is an integer of 1 to 8), such as LiBF ₃ (CF ₃ ) Lithium oxalate difluoroborate (LiODFB) represented by LiBF ₂ (C ₂ O ₄ ); Lithium bis (oxalato) borate (LiBOB) represented by LiB (C ₂ O ₄ ) ₂ Halogenated LiBOB typified by: LiB (C ₃ O ₄ H ₂ ) ₂ Malonate) borate (LiBMB); lithium tetrafluorooxalatophosphate represented by LiPF ₄ (C ₂ O ₂ ); organic lithium salts represented by the following formulas (1a), (1b) and (1c) .
LiC (SO ₂ R ⁴ ) (SO ₂ R ⁵ ) (SO ₂ R ⁶ ) (1a)
LiN (SO ₂ OR ⁷ ) (SO ₂ OR ⁸ ) (1b)
LiN (SO ₂ R ⁹ ) (SO ₂ OR ¹⁰ ) (1c)
(In the formula, R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ each independently represents a C 1-8 perfluoroalkyl group.)

  Among these, an organic lithium salt having a boron atom is preferable. Such an organic lithium salt tends to further improve the structural stability.

  Moreover, it is preferable to use an organic lithium salt having an organic ligand. Although it does not specifically limit as an organic lithium salt which has an organic ligand, Specifically, halogenated LiBOB represented by LiBOB and LiODFB, and LiBMB are preferable, and LiBOB and LiODFB are more preferable. By using such an organic lithium salt, organic ligands are involved in the electrochemical reaction and SEI is easily formed on the surface of the electrode, thereby suppressing the increase in internal resistance derived from the positive electrode and other parts. It tends to be possible.

  In addition, the said lithium salt may be used individually by 1 type, or may use 2 or more types together.

The concentration of the lithium salt in the non-aqueous electrolyte is preferably 0.1 to 5 mol / L, more preferably 0.5 to 3 mol / L, and still more preferably 0.8 to 2 mol / L. When the concentration of the lithium salt is within the above range, the non-aqueous electrolyte has a higher conductivity, and the charge / discharge efficiency of the non-aqueous secondary battery using the non-aqueous electrolyte tends to be higher. It is in. The content of these lithium salts in the electrolyte solution can be confirmed by NMR measurement such as ¹¹ B-NMR, ¹³ C-NMR, ¹⁹ F-NMR, ³¹ P-NMR. In addition, the content of the lithium salt in the electrolyte solution in the lithium ion secondary battery is also confirmed by NMR measurement such as ¹¹ B-NMR, ¹³ C-NMR, ¹⁹ F-NMR, ³¹ P-NMR, as described above. can do.

[Nonaqueous solvent]
The nonaqueous electrolytic solution according to this embodiment contains a nonaqueous solvent. Such a non-aqueous solvent is not particularly limited, and examples thereof include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone. Acid esters such as: ketones such as dimethyl ketone, diethyl ketone, methyl ethyl ketone, 3-pentanone, and acetone; hydrocarbons such as pentane, hexane, octane, cyclohexane, benzene, toluene, xylene, fluorobenzene, and hexafluorobenzene Ethers such as dimethyl ether, diethyl ether, 1,2-dimethoxyethane, 1,4-dioxane, crown ethers, glymes, tetrahydrofuran, and fluorine-containing ethers; N, N-dimethylacetamide and N, N-di Amides such as tylformamide; Amines such as ethylenediamine and pyridine; Propylene carbonate, ethylene carbonate, vinylene carbonate, fluoroethylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3- Butylene carbonate, 1,2-pentylene carbonate, trans-2,3-pentylene carbonate, cis-2,3-pentylene carbonate, vinyl ethylene carbonate, trifluoromethyl ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate , Methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl Carbonates such as propyl carbonate and methyl trifluoroethyl carbonate; nitriles such as acetonitrile, propionitrile, adiponitrile, succinonitrile, malononitrile, and methoxyacetonitrile; lactams such as N-methylpyrrolidone (NMP); sulfolane and Sulfones such as 3-methyl sulfolane, dimethyl sulfone and ethyl methyl sulfone; sulfonic acid esters such as propane sultone and butane sultone; sulfoxides such as dimethyl sulfoxide; industrial oils such as silicon oil and petroleum; and edible oils It is done.

  Moreover, an ionic liquid can also be used as a non-aqueous solvent. An “ionic liquid” is a liquid composed of ions obtained by combining an organic cation and an anion.

  The organic cation is not particularly limited, and examples thereof include imidazolium ions such as dialkylimidazolium cation and trialkylimidazolium cation; tetraalkylammonium ion; alkylpyridinium ion; dialkylpyrrolidinium ion; and dialkylpiperidinium ion. .

The anion serving as a counter for these organic cations is not particularly limited. For example, PF ₆ anion, PF ₃ (C ₂ F ₅ ) ₃ anion, PF ₃ (CF ₃ ) ₃ anion, BF ₄ anion, BF ₂ ( CF ₃ ) ₂ anion, BF ₃ (CF ₃ ) anion, bisoxalatoborate anion, Tf (trifluoromethanesulfonyl) anion, Nf (nonafluorobutanesulfonyl) anion, bis (fluorosulfonyl) imide anion, bis (trifluoromethanesulfonyl) ) Anion anion, bis (pentafluoroethanesulfonyl) imide anion, dicyanoamine anion, halide anion.

  The non-aqueous solvent may be used alone or in combination of two or more, but it is preferable to use a mixture of two or more.

(Aprotic solvent)
The non-aqueous solvent preferably contains an aprotic solvent. Battery characteristics tend to be further improved by using an aprotic solvent. Such an aprotic solvent is not particularly limited, and examples thereof include a cyclic carbonate compound, a chain carbonate compound, a nitrile compound, an ether compound, and an ester compound.

  Although it does not specifically limit as said cyclic carbonate compound, For example, ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, vinylene carbonate is mentioned.

  The chain carbonate compound is not particularly limited. For example, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, methyl fluoro Examples include methyl carbonate, difluoromethyl carbonate and methyl trifluoroethyl carbonate.

  The nitrile compound is not particularly limited, and examples thereof include acetonitrile, propionitrile, adiponitrile, succinonitrile, malononitrile, acrylonitrile, and methoxyacetonitrile.

〔salt〕
The nonaqueous electrolytic solution according to this embodiment includes (1) nitrate or nitrite, (2) a salt in which one or more halogen atoms or alkyl halides are bonded to phosphorus, and (3) a carbon number of 1 to 1. One or more salts selected from the group consisting of 5 carboxylates.

  Although it does not specifically limit as nitrate or nitrite, For example, the salt etc. which consist of nitric acid or nitrous acid, and the following counter cation are mentioned.

  The halogen atom used in the salt in which one or more halogen atoms or alkyl halide is bonded to phosphorus is not particularly limited, and examples thereof include any one or more of chlorine, fluorine, and iodine. Fluorine is preferred. The salt in which one or more halogen atoms or alkyl halide is bonded to phosphorus is not particularly limited, and examples thereof include monofluorophosphate, difluorophosphate, trifluorophosphate, and alkylfluorophosphate. Etc.

  Although it does not specifically limit as a C1-C5 carboxylate, For example, acetate, propionate, etc. are mentioned.

  Among these, one or more selected from the group consisting of nitrate, monofluorophosphate, and difluorophosphate is preferable, one or more selected from the group consisting of monofluorophosphate and difluorophosphate is more preferable, One or more selected from the group consisting of lithium monofluorophosphate and lithium difluorophosphate is more preferable. By using such a salt, the cycle characteristics and / or storage characteristics of the battery tend to be more excellent.

  The counter cation of these salts is not particularly limited, but lithium, sodium, magnesium, potassium, calcium, and ammonium are preferable, lithium and sodium are more preferable, and lithium is more preferable. The salt used in the present embodiment may be used as it is in a non-aqueous electrolyte or in a non-aqueous solvent used in the electrolyte, or a salt synthesized and isolated separately from a non-aqueous solvent. It may be added in the middle or non-aqueous electrolyte. Among these, the salt produced | generated in the nonaqueous solvent used in a nonaqueous electrolyte or electrolyte solution is preferable, and the lithium monofluorophosphate or lithium difluorophosphate produced | generated in the nonaqueous electrolyte is preferable. By using such a salt, a high-purity non-aqueous electrolyte tends to be prepared by a simple process.

  The method for producing the salt in the non-aqueous electrolyte is not particularly limited. For example, the salt is produced by hydrolyzing the lithium salt using a small amount of alcohol or hydrofluoric acid in the non-aqueous electrolyte or non-aqueous solvent. A method is mentioned. Lithium difluorophosphate and lithium monofluorophosphate can also be produced in a non-aqueous electrolyte by the same method.

  The salt used in this embodiment may be used alone or in combination of two or more at any ratio.

  The content of the salt used in the present embodiment is preferably 5 ppm or more and 1% by mass or less, more preferably 10 ppm or more and 0.5% by mass or less, and more preferably 10 ppm or more and 0% by mass with respect to 100% by mass of the nonaqueous electrolytic solution. More preferably, it is 3% by mass or less. When the salt content is within the above range, the cycle characteristics and / or storage characteristics of the battery tend to be more excellent.

[Hydrofluoric acid and alcohol]
In addition, the nonaqueous electrolytic solution according to this embodiment includes one or more selected from the group consisting of hydrofluoric acid and alcohol. By using hydrofluoric acid or alcohol, the continuous repair and formation of the SEI film becomes easier, and the cycle characteristics and output of the battery are improved.

(Hydrofluoric acid)
The content of hydrofluoric acid is preferably 0.5 to 50 ppm, more preferably 1 to 30 ppm, and still more preferably 2 to 20 ppm with respect to 100% by mass of the nonaqueous electrolytic solution. When the content of hydrofluoric acid is within the above range, the continuous repair and formation of the SEI film tend to be easier. Thereby, an improvement in the output of the battery is recognized. The content of hydrofluoric acid in the electrolytic solution can be confirmed by ¹⁹ F-NMR measurement or the like. Further, the content of hydrofluoric acid in the electrolytic solution in the lithium ion secondary battery can also be confirmed by ¹⁹ F-NMR measurement or the like as described above.

(alcohol)
Although it does not specifically limit as alcohol used by this embodiment, For example, monoalcohol or diol is mentioned.

  Although it does not specifically limit as monoalcohol, For example, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol 2-hexanol, 3-hexanol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, 1-octanol, 2-octanol, 3-octanol, 4-octanol, 1-nonanol, 2-nonanol, 3 -Nonanol, 4-nonanol, 5-nonanol etc. are mentioned.

  Examples of the diol include, but are not limited to, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octane. Linear alcohols such as diol, 1,9-nonanediol, 1,10-decanediol; 2-methyl-1,3-propylene glycol, 2,2-dimethyl-1,3-propylene glycol, 2-ethyl -Branched alcohols such as 1,3-hexanediol and 2-methyl-1,4-butylene glycol; cyclic alcohols such as 1,4-cyclohexanediol, 1,3-cyclopentanediol and 1,4-cyclohexanedimethanol Alcohol; 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3 Propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butylene glycol, 2-methyl-1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1, Examples include polyalkylene oxides or polyalkylene carbonates using one or more of 7-heptanediol, 1,8-octanediol, and 1,9-nonanediol as raw materials.

  These alcohols may be used alone or in combination of two or more.

The content of the alcohol is preferably 0.5 ppm to 1% by mass, more preferably 1 ppm to 0.5% by mass, and still more preferably 2 ppm to 0.2% by mass with respect to 100% by mass of the nonaqueous electrolytic solution. When the alcohol content is within the above range, the SEI tends to be formed smoothly. The content of these alcohols in the electrolyte solution can be confirmed by NMR measurements such as ¹ H-NMR and ¹³ C-NMR. In addition, the content of alcohol in the electrolyte solution in the lithium ion secondary battery can be confirmed by NMR measurement such as ¹ H-NMR and ¹³ C-NMR as described above.

  In this embodiment, only one of hydrofluoric acid and alcohol may be used, or both may be used in combination.

(water)
The nonaqueous electrolytic solution according to the present embodiment preferably does not contain moisture, but may contain a very small amount of moisture as long as the solution of the problem of the present embodiment is not hindered. Such water content is preferably 0 to 100 ppm, more preferably 1 to 50 ppm, and still more preferably 1 to 30 ppm with respect to the total amount of the nonaqueous electrolytic solution.

(Additive)
The non-aqueous electrolyte according to the present embodiment may further contain an additive as necessary. Although it does not specifically limit as an additive used by this embodiment, For example, the substance which plays the role as a solvent which melt | dissolves lithium salt is mentioned. Such materials may substantially overlap with the non-aqueous solvent described above. Further, the additive is preferably a substance that contributes to improving the performance of the non-aqueous electrolyte and the non-aqueous secondary battery according to this embodiment, and a substance that does not directly participate in the electrochemical reaction can also be used. . In addition, an additive may be used individually by 1 type, or may use 2 or more types together.

  Although it does not specifically limit as an additive, For example, vinylene carbonate, unsaturated bond containing cyclic carbonate represented by vinyl ethylene carbonate; 4-fluoro- 1, 3- dioxolan-2-one, trans-4, 5- difluoro Fluorine-containing representatives such as -1,3-dioxolan-2-one, cis-4,5-difluoro-1,3-dioxolan-2-one, and 4,4-difluoro-1,3-dioxolan-2-one Carbonate; lactone represented by γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, ε-caprolactone; cyclic ether represented by 1,2-dioxane; methyl formate, methyl Acetate, methyl propionate, methyl butyrate, ethyl formate, ethanol Acetate, ethyl propionate, ethyl butyrate, n-propyl formate, n-propyl acetate, n-propyl propionate, n-propyl butyrate, isopropyl formate, isopropyl acetate, isopropyl propionate, isopropyl butyrate Rate, n-butylformate, n-butylacetate, n-butylpropionate, n-butylbutyrate, isobutylformate, isobutylacetate, isobutylpropionate, isobutylbutyrate, sec-butylformate, sec- Butyl acetate, sec-butyl propionate, sec-butyl butyrate, tert-butyl formate, tert-butyl acetate, tert-butyl propionate, tert-butyl butyrate, Rupivalate, n-butyl pivalate, n-hexyl pivalate, n-octyl pivalate, dimethyl oxalate, ethyl methyl oxalate, diethyl oxalate, diphenyl oxalate, malonic acid ester, fumaric acid ester, maleic acid ester Carboxylic acid ester; amides represented by N-methylformamide, N, N-dimethylformamide, N, N-dimethylacetamide; ethylene sulfite, propylene sulfite, butylene sulfite, pentene sulfite, sulfolane, 3-methylsulfolane 3-sulfolene, 1,3-propane sultone, 1,4-butane sultone, 1,3-propanediol sulfate, 1,3-propene sultone, tetramethylene sulfoxide, thiophene 1-oxy Cyclic sulfur compounds represented by Cid; aromatic compounds represented by monofluorobenzene, biphenyl and fluorinated biphenyl; nitro compounds represented by nitromethane; Schiff bases; Schiff base complexes; oxalato complexes, substituted or unsubstituted benzenes , Biphenyl, naphthalene, terphenyl and other aromatic compounds; trimethyl phosphate, triethyl phosphate, trimethyl phosphite, triethyl phosphite, phosphoric acid ester represented by fluorine-substituted phosphoric acid or phosphite Or phosphite; 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, and diols typified by polyethylene glycol may be mentioned. These may be used individually by 1 type, or may use 2 or more types together.

  The non-aqueous electrolyte according to the present embodiment is not particularly limited, but can be used for, for example, electrochemical devices such as an electrolyte for a lithium ion secondary battery, an electrolyte for a lithium ion capacitor, and an electrolyte for a lithium air battery. . Among these, the nonaqueous electrolytic solution according to the present embodiment is particularly preferably used as an electrolytic solution for a lithium ion secondary battery. By using it as an electrolyte for a lithium ion secondary battery, a lithium ion secondary battery having both durability and withstand voltage performance can be realized.

[Lithium ion secondary battery]
A lithium ion secondary battery according to the present embodiment includes the non-aqueous electrolyte or the electrolyte for a lithium ion secondary battery, a positive electrode, and a negative electrode, and the positive electrode can occlude and release lithium ions. One or more positive electrode active materials are contained, and the negative electrode contains one or more negative electrode active materials selected from the group consisting of materials capable of inserting and extracting lithium ions and metallic lithium. Moreover, the lithium ion secondary battery which concerns on this embodiment may be provided with the separator as needed. A positive electrode, a negative electrode, and a separator are demonstrated below.

[Positive electrode]
A positive electrode will not be specifically limited if it acts as a positive electrode of a lithium ion secondary battery, A well-known thing may be used. The positive electrode contains one or more materials that can occlude and release lithium ions as a positive electrode active material. Such a positive electrode active material is not particularly limited. For example, lithium-containing compounds; metal chalcogenides and metal oxides having tunnel structures and layer structures; olivine-type phosphate compounds; oxides of metals other than lithium; Examples include polymers. Of these, lithium-containing compounds are preferred. By using a lithium-containing compound as the positive electrode active material, a lithium ion secondary battery having a higher voltage and higher energy density tends to be obtained.

  Although it does not specifically limit as said lithium containing compound, For example, the composite oxide containing lithium and a transition metal element, the phosphoric acid compound containing lithium and a transition metal element, and the metal silicate containing lithium and a transition metal element Compounds and the like.

Although it does not specifically limit as a complex oxide containing the said lithium and transition metal element, For example, the compound represented by following formula (2a) and (2b) is mentioned. More specifically, lithium cobalt oxide typified by LiCoO ₂ ; lithium manganese oxide typified by LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ Mn ₂ O ₄ ; lithium nickel oxide typified by LiNiO ₂ Li _z MO ₂ (M represents two or more elements selected from the group consisting of Ni, Mn, Co, Al, and Mg, and z represents a number greater than 0.9 and less than 1.2) Examples thereof include lithium-containing composite metal oxides. Among these, lithium, cobalt (Co), nickel (Ni), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), chromium (Cr), vanadium (V) and titanium (Ti A composite oxide and a phosphate compound containing at least one transition metal element selected from the group consisting of: By using such a lithium-containing compound, a higher voltage tends to be obtained.

The compound represented by the following formula (2a) generally has a layered structure. As the compound, for the purpose of stabilizing the structure, a part of the transition metal element is substituted with Al, Mg, other transition metal elements or included in the crystal grain boundary, a part of the oxygen atom And those substituted with a fluorine atom or the like. Furthermore, what coat | covered the other positive electrode active material to at least one part of the positive electrode active material surface is mentioned.
Li _x MO ₂ (2a)
(In formula (2a), M represents one or more metals selected from transition metals, x represents a number from 0 to 1, and y represents a number from 0 to 2.)

The compound represented by the following formula (2b) generally has a spinel structure. Examples of the compound include lithium metal oxides containing manganese and lithium metal oxides containing manganese and other transition metals.
Li _y M ₂ O ₄ (2b)
(In formula (2b), M represents one or more metals selected from transition metals, x represents a number from 0 to 1, and y represents a number from 0 to 2.)

The phosphate compound containing lithium and a transition metal element is not particularly limited, for example, iron phosphate olivine represented by LiFePO _4; include compounds represented by the formula (3). The compound represented by the following formula (3) generally has an olivine structure. In the compound, for the purpose of stabilizing the structure, a part of the transition metal element is substituted with Al, Mg, Co, Ti or other transition metal elements, or these other transition metal elements are included in the crystal grain boundaries. And those obtained by substituting a part of oxygen atoms with fluorine atoms or the like. Furthermore, what coat | covered the other positive electrode active material to at least one part of the positive electrode active material surface is mentioned.
Li _w M ^II PO ₄ (3)
(In formula (3), M ^II represents one or more transition metal elements, and the value of w varies depending on the charge / discharge state of the battery, but usually w represents a number of 0.05 to 1.10.)

The silicic acid metal compound containing the lithium and a transition metal element is not particularly limited, for example, a compound represented by Li _t M _u SiO ₄ and the like. Here, M is one or more metals selected from transition metals, t is a number from 0 to 1, and u is a number from 0 to 2.

  The olivine-type phosphate compound is not particularly limited, and examples thereof include manganese olivine phosphate and cobalt olivine phosphate.

The metal chalcogenide and metal oxide having the tunnel structure and the layer structure, and the oxide of the metal other than lithium are not particularly limited. For example, S, MnO ₂ , FeO ₂ , FeS ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , TiS ₂ , MoS ₂ and NbSe ₂ .

  The conductive polymer is not particularly limited, and examples thereof include polyaniline, polythiophene, polyacetylene, and polypyrrole.

  A positive electrode active material is used individually by 1 type or in combination of 2 or more types.

  The positive electrode active material preferably contains at least one of a layered compound represented by (2a), a spinel compound represented by (2b), and a compound having a spinel structure site. By using such a positive electrode active material, battery characteristics and safety tend to be further improved when driven at a high voltage.

  The number average particle diameter (primary particle diameter) of the positive electrode active material is preferably 0.05 μm to 100 μm, more preferably 1 μm to 10 μm. 100 particles observed with a transmission electron microscope are randomly extracted and analyzed with image analysis software (for example, image analysis software manufactured by Asahi Kasei Engineering Co., Ltd., trade name “A Image-kun”). It is obtained by calculating. In this case, when the number average particle diameter differs between measurement methods for the same sample, a calibration curve created for the standard sample may be used.

  A metal-containing compound or an organic or inorganic compound may be applied or coated on a part or the whole of the surface of the positive electrode active material. By performing various coatings and coatings on the surface of the positive electrode, it is possible to improve the battery characteristics or to change the properties by suppressing the deterioration of the battery derived from the positive electrode material.

(Production method of positive electrode)
The positive electrode is obtained, for example, as follows. That is, first, a positive electrode mixture-containing paste is prepared by dispersing, in a solvent, a positive electrode mixture obtained by adding a conductive additive, a binder, or the like to the positive electrode active material as necessary. Next, this positive electrode mixture-containing paste is applied to a positive electrode current collector and dried to form a positive electrode mixture layer, which is pressurized as necessary to adjust the thickness, thereby producing a positive electrode.

  Here, the solid content concentration in the positive electrode mixture-containing paste is preferably 30 to 80% by mass, and more preferably 40 to 70% by mass.

  Although it does not specifically limit as a positive electrode electrical power collector, For example, metal foil, such as aluminum foil or stainless steel foil, is mentioned.

[Negative electrode]
A negative electrode will not be specifically limited if it acts as a negative electrode of a lithium ion secondary battery, A well-known thing may be used. The negative electrode contains one or more materials selected from the group consisting of a material capable of inserting and extracting lithium ions as a negative electrode active material and metallic lithium. Such a negative electrode preferably contains, as a negative electrode active material, one or more selected from the group consisting of metallic lithium, a carbon material, a silicon material, a material containing an element capable of forming an alloy with lithium, and a lithium-containing compound. Among these, it is more preferable to contain one or more materials selected from the group consisting of metallic lithium, carbon materials, silicon materials, and materials containing elements capable of forming an alloy with lithium. By using such a negative electrode active material, the battery capacity tends to be further improved.

  The carbon material is not particularly limited, for example, hard carbon, soft carbon, artificial graphite, natural graphite, graphite, pyrolytic carbon, coke, glassy carbon, organic polymer compound fired body, mesocarbon microbeads, Examples thereof include carbon fiber, activated carbon, graphite, carbon colloid, and carbon black. Among these, the coke is not particularly limited, and examples thereof include pitch coke, needle coke, and petroleum coke. Further, the fired body of the organic polymer compound is not particularly limited. For example, a polymer material such as a phenol resin or a furan resin is fired at a suitable temperature and carbonized. In the present embodiment, a battery employing metallic lithium as the negative electrode active material is also included in the lithium ion secondary battery.

  Although it does not specifically limit as said silicon material, For example, a crystalline silicon compound, an amorphous silicon compound, an organosilicon compound, an alloy of silicon and a metal, an alloy, etc. are mentioned. In addition, various forms of silicon materials such as nano silicon materials and fibrous silicon materials can be used.

  Furthermore, the material containing an element capable of forming an alloy with lithium is not particularly limited. For example, the material may be a metal or a semimetal alone, an alloy, or a compound. Alternatively, it may have at least a part of two or more phases.

  In the present specification, the “alloy” includes an alloy having one or more metal elements and one or more metalloid elements in addition to an alloy composed of two or more metal elements. Further, the alloy may have a nonmetallic element as long as it has metal properties as a whole. In the structure of the alloy, a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of these coexist.

  Such metal elements and metalloid elements are not particularly limited. For example, titanium (Ti), tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn) , Antimony (Sb), bismuth (Bi), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), hafnium (Hf), zirconium (Zr) and yttrium (Y). Among these, metal elements and metalloid elements of Group 4 or Group 14 in the long-period periodic table are preferable, and titanium, silicon, and tin are more preferable.

  The silicon alloy is not particularly limited. For example, as the second constituent element other than silicon, tin, magnesium, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony And one having one or more elements selected from the group consisting of chromium.

  Although it does not specifically limit as an alloy of tin, For example, as a 2nd element other than tin, silicon, magnesium (Mg), nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium (Ti) And one having at least one element selected from the group consisting of germanium, bismuth, antimony and chromium (Cr).

  The titanium compound, the tin compound, and the silicon compound are not particularly limited, and examples thereof include those having oxygen (O) or carbon (C). In addition to titanium, tin, or silicon, the second compound described above is used. It may have a constituent element.

  Although it does not specifically limit as a lithium containing compound, For example, the same thing as what was illustrated as a positive electrode material can be used.

  A negative electrode active material is used individually by 1 type or in combination of 2 or more types.

  The number average particle diameter (primary particle diameter) of the negative electrode active material is preferably 0.1 μm to 100 μm, more preferably 1 μm to 10 μm. The number average particle size of the negative electrode active material is measured in the same manner as the number average particle size of the positive electrode active material.

(Method for producing negative electrode)
A negative electrode is obtained as follows, for example. That is, first, a negative electrode mixture-containing paste is prepared by dispersing, in a solvent, a negative electrode mixture prepared by adding a conductive additive or a binder to the negative electrode active material, if necessary. Next, the negative electrode mixture-containing paste is applied to a negative electrode current collector and dried to form a negative electrode mixture layer, which is pressurized as necessary to adjust the thickness, whereby a negative electrode can be produced. .

  Here, the solid content concentration in the negative electrode mixture-containing paste is preferably 30 to 80% by mass, and more preferably 40 to 70% by mass.

  Although a negative electrode collector is not specifically limited, For example, metal foil, such as copper foil, nickel foil, or stainless steel foil, is mentioned.

  In the production of the positive electrode and the negative electrode, the conductive aid used as necessary is not particularly limited, and examples thereof include carbon black typified by graphite, acetylene black and ketjen black, and carbon fibers. The number average particle diameter (primary particle diameter) of the conductive assistant is preferably 0.1 μm to 100 μm, more preferably 1 μm to 10 μm. The number average particle size of the conductive additive is measured in the same manner as the number average particle size of the positive electrode active material. The binder is not particularly limited, and examples thereof include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, styrene butadiene rubber, and fluorine rubber.

[Separator]
The lithium ion battery of this embodiment includes a separator between the positive electrode and the negative electrode in order to provide safety such as prevention of short circuit between the positive and negative electrodes. As the separator, an insulating thin film having high ion permeability and excellent mechanical strength is preferable.

  Although the material of the separator in this embodiment is not specifically limited, For example, a ceramic, glass, resin, and a cellulose are mentioned. The resin may be a synthetic resin or a natural resin (natural polymer), and may be an organic resin or an inorganic resin. From the viewpoint of excellent performance as a separator, An organic resin is preferred.

  Although it does not specifically limit as organic resin, For example, heat resistant resins, such as polyolefin, polyester, polyamide, liquid crystal polyester, and aramid, are mentioned.

  Moreover, it does not specifically limit as inorganic resin, For example, a silicone resin etc. are mentioned.

  The material of the separator is preferably ceramic and glass from the viewpoint of heat resistance, and polyester, polyamide, liquid crystal polyester, aramid, and cellulose are preferable from the viewpoint of handling properties and heat resistance. Further, from the viewpoint of cost and processability, polyolefin is preferable. Among these materials, when a resin is employed, it may be a homopolymer or a copolymer, and a mixture of a plurality of types of resins and an alloy may be used.

  Further, the separator may be a laminated body in which films made of a plurality of materials are laminated. When the separator is a laminate, the material of each layer may be the same or different.

(Manufacturing method of separator)
In the case of manufacturing a separator of a laminated body, it may be manufactured by sequentially stacking a certain layer on another layer, that is, by sequentially multilayering, and a plurality of separate films may be bonded together. Thus, a laminate may be produced.

  As the form of the separator in the present embodiment, for example, a synthetic resin microporous film produced by forming a synthetic resin film, a fiber spun from a synthetic resin or a natural polymer, a woven fabric processed from glass fiber or ceramic fiber, Nonwoven fabrics, knitted fabrics, papermaking, and films prepared by arranging synthetic resin, ceramic particles, and glass fine particles are listed.

  In the present embodiment, the separator is a component other than the above, for example, an organic filler, an inorganic filler, an organic particle, or an inorganic particle on the surface of the separator and / or from the viewpoint of film reinforcement, charge / discharge assistance, heat resistance improvement, and the like. It may be included inside.

[Method for producing lithium ion secondary battery]
As a manufacturing method of the lithium ion secondary battery in the present embodiment, a general method may be used and is not particularly limited. For example, the following method can be selected.

  First, a battery structure is produced by housing a laminate produced using a positive electrode, a negative electrode, and a separator in a battery case (exterior). And a battery can be produced by injecting the electrolytic solution of the present embodiment into it.

  The method for producing the laminated body is not particularly limited. For example, first, the positive electrode and the negative electrode are wound in a laminated state with a separator interposed therebetween to form a laminated structure having a wound structure, or bend them. And a method of forming a laminate in which separators are interposed between a plurality of alternately stacked positive and negative electrodes by, for example, stacking a plurality of layers.

  In the manufacturing method of a lithium ion secondary battery, the process which pressurizes the inside of a battery or depressurizes can also be included. The method of pressurization or decompression is not particularly limited, and the heating and the decompression or pressurization may be performed simultaneously or separately. By passing through these steps, the impregnation property of the electrolyte into the electrode and separator of the battery structure may be improved.

  After passing through the above steps, if necessary, the remaining members are incorporated into the battery structure, and if the battery case (exterior) is not completely sealed (sealed), the battery is sealed. Can be obtained. In addition, after passing through each process mentioned above as needed, you may prepare shapes, such as removing the excess part of a battery, or may retighten or reseal a battery.

  The shape of the battery in this embodiment is not particularly limited, and a cylindrical shape, an elliptical shape, a rectangular tube shape, a button shape, a coin shape, a flat shape, and a laminate shape are preferable. Among these, a coin type, a cylindrical type, a rectangular tube type, a flat type and a laminate type are more preferable, and a coin type and a laminate type are more preferable. The battery having such a shape can further enhance the affinity between the electrolytic solution and the battery structure, expresses various performances of the electrolytic solution in the present embodiment to a higher level, and is relatively easy to manufacture the battery. Easy. Also, the size of the battery is not particularly limited, and a structure in which a plurality of batteries are stacked or arranged can be used in combination with many kinds of batteries. Also, among laminated batteries, the battery case (exterior) is constructed by laminating an aluminum film and a resin like an aluminum laminate material from the viewpoint of lightness, durability, handleability, cost, etc. More preferably.

  Although the lithium ion secondary battery of this embodiment can function as a battery by the first charge, it is stabilized when a part of the electrolytic solution containing the fluorinated carbonate is decomposed during the first charge. Although there is no restriction | limiting in particular about the method of the initial charge in this embodiment, It is preferable that initial charge is performed at 0.001-0.3C, It is more preferable to be performed at 0.002-0.25C, 0.003 More preferably, it is carried out at ~ 0.2C. In addition, it is also preferable that the initial charging is performed via the constant voltage charging in the middle. In addition, the constant current which discharges rated capacity in 1 hour is 1C. By setting the voltage range in which the lithium salt is involved in the electrochemical reaction to be long, SEI is formed on the electrode surface, which has an effect of suppressing an increase in internal resistance including the positive electrode. In addition, since the reaction product is not firmly fixed only on the negative electrode, and in some form it has a good effect on other members such as the positive electrode and the separator, the electrochemical property of the lithium salt dissolved in the electrolyte It is very effective to perform the first charge in consideration of the reaction.

  The non-aqueous secondary battery of this embodiment can also be used in series or in parallel. In addition, from a viewpoint of managing the charge / discharge state of the battery pack, the working voltage range is preferably 2 to 5.5V, and more preferably 2.5 to 5.0V. The upper limit voltage of the nonaqueous secondary battery of the present embodiment is preferably 4.3 V or more from the viewpoints of handling and increasing the capacity. The upper limit of the upper limit voltage is not particularly limited, but is preferably 5.5 V or less. In addition, when used at 4.3 V or higher, problems such as decomposition of the electrolyte, generation of acid, and increase of metal elution from the positive electrode material occur. As a result, the amount of lithium contributing to gas generation and charge / discharge is reduced, and the battery characteristics are deteriorated. In the conventional product (using 4.2 V or less), the above problems are few and there is no problem in practical use. However, the condition becomes severer as the working voltage is increased, and the battery characteristics tend to decrease significantly. In this regard, the above problem can be solved or suppressed with a non-aqueous secondary battery using the non-aqueous electrolyte according to the present embodiment.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. Various characteristics of the nonaqueous secondary battery were measured and evaluated as follows.

[Examples 1 to 12, Comparative Examples 1 to 6]
(1) Preparation of Nonaqueous Electrolytic Solution A predetermined amount of components constituting the nonaqueous electrolytic solution were prepared and stirred in an argon atmosphere to obtain the electrolytic solutions of Examples 1 to 12 and Comparative Examples 1 to 6. The composition is shown in Table 1.
The difluoro salt and / or monofluoro salt was produced in an electrolytic solution using a hydrolysis reaction of hexafluorophosphate.

(2) Production of lithium ion secondary battery (production of positive electrode α)
As a positive electrode active material, a mixed oxide containing lithium, nickel, manganese and cobalt having a number average particle diameter of 11 μm (LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ ), the following conductive auxiliary agent, and polyvinylidene fluoride ( PVdF) (manufactured by Kureha) was mixed in a mass ratio of mixed oxide: graphite carbon powder: acetylene black powder: PVdF = 100: 4.2: 1.8: 4.6. To the obtained mixture, N-methyl-2-pyrrolidone was added so as to have a solid content of 68% by mass and further mixed to prepare a slurry-like solution. This slurry-like solution was applied to one side of an aluminum foil having a thickness of 20 μm, and the solvent was dried and removed, followed by rolling with a roll press. The rolled product was punched into a disk shape having a diameter of 16 mm to obtain a positive electrode (α).
Conductive aid:
Graphite carbon powder with a number average particle size of 6.5 μm (manufactured by TIMCAL, trade name “KS-6”)
Acetylene black powder having a number average particle diameter of 48 nm (trade name “HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.)

(Preparation of positive electrode β)
Lithium cobalt acid (LiCoO ₂ ) having a number average particle diameter of 15 μm as a positive electrode active material, graphite carbon powder (manufactured by TIMCAL, trade name “KS-6”) having a number average particle diameter of 3 μm as a conductive additive, and a binder Polyvinylidene fluoride (PVdF) (trade name “L # 7208” manufactured by Kureha Co., Ltd.) was mixed at a mass ratio of 85: 10: 5. N-methyl-2-pyrrolidone was added to the obtained mixture so as to have a solid content of 60% by mass and further mixed to prepare a slurry solution. This slurry-like solution was applied to one side of an aluminum foil having a thickness of 20 μm, and the solvent was dried and removed, followed by rolling with a roll press. The rolled product was punched into a disk shape having a diameter of 16 mm to obtain a positive electrode (β).

(Preparation of positive electrode γ)
<Synthesis of positive electrode active material>
(Synthesis example of LiNi _0.5 Mn _1.5 O ₄ )
Nickel sulfate and manganese sulfate in an amount of 1: 3 as the molar ratio of the transition metal element were dissolved in water to prepare a nickel-manganese mixed aqueous solution so that the total metal ion concentration was 2 mol / L. Subsequently, this nickel-manganese mixed aqueous solution was dropped into 3000 mL of a 2 mol / L sodium carbonate aqueous solution heated to 70 ° C. at an addition rate of 12.5 mL / min for 120 minutes. During dropping, air with a flow rate of 200 mL / min was bubbled into the aqueous solution while stirring. Thereby, a precipitated substance was generated, and the obtained precipitated substance was sufficiently washed with distilled water and dried to obtain a nickel manganese compound. The obtained nickel-manganese compound and lithium carbonate having a particle size of 2 μm were weighed so that the molar ratio of lithium: nickel: manganese was 1: 0.5: 1.5, and obtained after dry-mixing for 1 hour. The obtained mixture was fired at 1000 ° C. for 5 hours in an oxygen atmosphere to obtain a positive electrode active material represented by LiNi _0.5 Mn _1.5 O ₄ .

The positive electrode active material obtained as described above and graphite powder (TIM as a conductive auxiliary agent)
CAL, trade name “KS-6”) and acetylene black powder (trade name “HS-100”, manufactured by Denki Kagaku Kogyo Co., Ltd.) and a polyvinylidene fluoride solution (trade name “L #”, manufactured by Kureha Co., Ltd.) as a binder. 7208 ") at a mass ratio of 80: 5: 5: 10 in terms of solid content. To the obtained mixture, N-methyl-2-pyrrolidone as a dispersion solvent was added so as to have a solid content of 35% by mass and further mixed to prepare a slurry solution. This slurry-like solution was applied to one side of an aluminum foil having a thickness of 20 μm, and the solvent was dried and removed, followed by rolling with a roll press. The rolled product was punched into a 3 cm × 4 cm rectangular shape to obtain a positive electrode (γ).

(Preparation of negative electrode)
The following negative electrode active material and the following binder are mixed at a solid mass ratio of graphite carbon powder (I): graphite carbon powder (II): carboxymethyl cellulose solution: diene rubber = 90: 10: 1.44: 1.76. A slurry-like solution was prepared by mixing so that the total solid concentration was 45% by mass. The slurry solution was applied to one side of a 10 μm thick copper foil, and the solvent was removed by drying, followed by rolling with a roll press. After rolling, it was punched into a disk shape having a diameter of 16 mm to obtain a negative electrode (negative electrode 1) and a 3 cm × 4 cm rectangular shape (negative electrode 2).
(Anode raw material)
Negative electrode active material:
Graphite carbon powder (I) with a number average particle diameter of 12.7 μm (Osaka Gas Chemical Co., Ltd.)
Graphite carbon powder (II) having a number average particle size of 6.5 μm (Showa Denko)
binder:
Carboxymethylcellulose solution (solids concentration 1.83% by mass)
Diene rubber (glass transition temperature: −5 ° C., number average particle size upon drying: 120 nm, dispersion medium: water, solid content concentration 40% by mass)

(Production example 1 of lithium ion secondary battery)
A laminate in which the positive electrode α or the positive electrode β and the negative electrode 1 manufactured as described above are laminated on both sides of a polyethylene separator (film thickness: 25 μm, porosity: 50%, pore diameter: 0.1 μm to 1 μm) It was inserted into a disk type battery case. Next, 0.4 mL of the electrolytic solution was injected into the battery case, and the laminate was immersed in the electrolytic solution. Then, the battery case was sealed to produce a lithium ion secondary battery (small battery). This was kept for 24 hours in a thermostatic bath set at 25 ° C., and the non-aqueous electrolyte was sufficiently adapted to the laminate, and produced so that 1 C = 6.0 mA. The produced battery was connected to a charge / discharge device (trade name “ACD-01” manufactured by Asuka Electronics Co., Ltd.), charged for 8 hours at a constant current of 0.2 C-constant voltage, and 3 at a constant current of 0.3 C. It was completed by initial conditioning by discharging to 0.0V.
The charging voltage was up to 4.35 V when the positive electrode α was used, and up to 4.55 V when the positive electrode β was used.

(Production example 2 of a lithium ion secondary battery)
An electrode tab is welded to the positive electrode γ and the negative electrode 2 produced as described above, and a microporous membrane made of polyethylene (film thickness 25 μm, porosity 50%, pore diameter 0.1 μm to 1 μm) is used as the separator. A laminate of electrodes and separators was prepared. Next, the laminate was sandwiched between exterior bodies composed of a laminate of aluminum and resin, and the three pieces were heat-sealed to obtain a laminate type battery. Next, 0.5 mL of the electrolyte solution was injected into the battery case and the laminate was immersed in the electrolyte solution, and then the battery case was sealed to produce a lithium ion secondary battery (small battery). This was kept for 24 hours in a thermostatic bath set at 25 ° C., and the non-aqueous electrolyte solution was sufficiently adapted to the laminate, and produced so that 1C = 20.0 mA. The produced battery was connected to a charging / discharging device (trade name “ACD-01” manufactured by Asuka Electronics Co., Ltd.), charged to 4.8 V for 8 hours at a constant current-constant voltage of 0.1 C, and charged with 0.3 C. It was completed by performing initial conditioning by discharging to 3.0 V at a constant current.

(3) Evaluation The following battery evaluation was performed using the electrolytic solution obtained as described above. These evaluations were performed using a charge / discharge device ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and a thermostat PLM-63S (trade name) manufactured by Futaba Kagaku Co., Ltd.

(Discharge capacity measurement)
After charging with a constant current of 6.0 mA and reaching 4.35 V, charging was performed with a constant voltage of 4.35 V, and charging was performed for a total of 8 hours. Then, the discharge capacity when discharging to 3.0 V with a constant current was determined. The discharge current was performed under conditions of 6 mA, 18 mA, and 30 mA. This measurement was performed in an environment of 25 ° C. Table 2 shows the results. In this test, the positive electrode α was used, and a predetermined test was performed after initial conditioning when the positive electrode α was used.

[High temperature cycle test 1]
After charging with a constant current of 6.0 mA and reaching 4.35 V, charging was performed with a constant voltage of 4.35 V, and charging was performed for a total of 8 hours. Then, it discharged to 3.0V with the constant current of 6.0mA, and let it be 1 cycle charging / discharging cycle. This charge / discharge cycle was performed 90 cycles at 50 ° C., and the value of the discharge capacity at the 90th cycle relative to the second cycle was calculated as the discharge capacity retention rate (A). This measurement was performed in an environment of 50 ° C. Table 2 shows the results. In this test, the positive electrode α was used, and a predetermined test was performed after initial conditioning when the positive electrode α was used.

[High temperature cycle test 2]
After charging with a constant current of 6.0 mA and reaching 4.5 V, charging was performed with a constant voltage of 4.5 V, and charging was performed for a total of 8 hours. Then, it discharged to 3.0V with the constant current of 6.0mA, and let it be 1 cycle charging / discharging cycle. This charge / discharge cycle was performed at 50 ° C. for 70 cycles, and the value of the discharge capacity at the 70th cycle relative to the second cycle was calculated as the discharge capacity retention rate (B). This measurement was performed in an environment of 50 ° C. Table 2 shows the results. In this test, the positive electrode β was used, and a predetermined test was performed after initial conditioning when the positive electrode β was used.

[High temperature storage test]
The battery was charged with a constant current of 2.0 mA and reached 4.7 V, and then charged with a constant voltage of 4.7 V, and charged for a total of 8 hours. Thereafter, discharging was performed up to 3.0 V with a constant current of 3.0 mA. Subsequently, the battery is charged at a constant current of 6.0 mA, reaches a constant voltage of 4.7 V, is charged at a constant voltage of 4.7 V, and is charged for a total of 8 hours. It was stored (float) at 50 ° C. for 10 days while maintaining a fully charged state. About the lithium ion secondary battery before and behind holding | maintenance, the gas amount in a battery was measured using the Archimedes method, and the amount of generated gas at the time of a full charge holding | maintenance was calculated | required. This measurement was performed in an environment of 50 ° C. Table 2 shows the results. In this test, a positive electrode γ was used, and a predetermined test was performed after initial conditioning when the positive electrode γ was used.

  As described above, the nonaqueous electrolyte of the present invention can suppress a chemical reaction unrelated to the battery reaction as an electrolyte for a nonaqueous secondary battery and has both durability and withstand voltage performance. It was shown that a secondary battery can be realized. It was also shown that a lithium ion secondary battery driven at a high voltage exceeding 4.2 V, which is excellent in durability, and a lithium ion secondary battery including the nonaqueous electrolyte can be realized.

  The nonaqueous electrolytic solution of the present invention has industrial applicability as an electrolytic solution for electrochemical devices, particularly as an electrolytic solution for lithium ion secondary batteries.

Claims (13)

A silicon-containing compound in which one or more hydrogen atoms of one or more compounds selected from the group consisting of inorganic acids, organic acids, acid amides, and amines are substituted with silicon-containing functional groups;
Lithium salt,
A non-aqueous solvent;
(1) Nitrate or nitrite, (2) a salt in which one or more halogen atoms or alkyl halide is bonded to phosphorus, and (3) a carboxylate having 1 to 5 carbon atoms. One or more salts,
One or more selected from the group consisting of hydrofluoric acid and alcohol;
A non-aqueous electrolyte.   The nonaqueous electrolytic solution according to claim 1, wherein the salt is at least one selected from the group consisting of nitrate, monofluorophosphate, and difluorophosphate.   The nonaqueous electrolytic solution according to claim 1, wherein the salt is at least one selected from the group consisting of lithium monofluorophosphate and lithium difluorophosphate.   The nonaqueous electrolytic solution according to claim 3, wherein the lithium monofluorophosphate and / or the lithium difluorophosphate is produced in the nonaqueous electrolytic solution.   The silicon-containing compound in which one or more hydrogen atoms of one or more compounds selected from the group consisting of an inorganic acid containing boron or phosphorus, a carboxylic acid, and a phosphoric acid amide are substituted with a silicon-containing functional group The nonaqueous electrolytic solution according to any one of claims 1 to 4, wherein   The silicon-containing compound is a silicon-containing compound in which one or more hydrogen atoms of one or more compounds selected from the group consisting of an inorganic acid containing phosphorus, a carboxylic acid, and a phosphoric acid amide are substituted with a silicon-containing functional group. The non-aqueous electrolyte of any one of Claims 1-4.   The nonaqueous electrolytic solution according to any one of claims 1 to 6, wherein the nonaqueous solvent contains an aprotic solvent.   The electrolyte solution for lithium ion secondary batteries containing the nonaqueous electrolyte solution of any one of Claims 1-7. The nonaqueous electrolytic solution according to any one of claims 1 to 7, or the electrolytic solution for a lithium ion secondary battery according to claim 8,
A positive electrode;
A negative electrode,
With
The positive electrode contains one or more positive electrode active materials capable of inserting and extracting lithium ions,
The negative electrode contains one or more negative electrode active materials selected from the group consisting of a material capable of inserting and extracting lithium ions and metallic lithium,
Lithium ion secondary battery.   The lithium ion secondary battery according to claim 9, wherein the positive electrode active material includes a lithium-containing compound.   The lithium ion secondary battery according to claim 9 or 10, wherein the positive electrode active material includes a lithium-containing compound having a layered structure or a lithium-containing compound having a spinel structure.   The negative electrode active material includes at least one material selected from the group consisting of metallic lithium, a carbon material, a silicon material, and a material containing an element capable of forming an alloy with lithium. The lithium ion secondary battery according to item.   The lithium ion secondary battery of any one of Claims 9-12 whose upper limit voltage of charge is 4.3V or more.