JP2014022334A - Electrolyte for nonaqueous electricity storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte achieving a lithium ion secondary battery having high cycle life even when a positive electrode containing a positive electrode active material acting at 4.4 V(vsLi/Li) or higher is used.SOLUTION: An electrolyte for a nonaqueous electricity storage device contains: a nonaqueous solvent; a bifunctional acid lithium salt (A) represented by the following formula (1); and a lithium salt (B) that is a lithium salt other than the bifunctional acid lithium salt represented by the following formula (1) and has no boron atom. (In the formula, Rrepresents a 0-10C hydrocarbon group that may be substituted, and Xrepresents a functional group selected from the group consisting of COO, SOand O.)

Description

  The present invention relates to an electrolyte for a non-aqueous energy storage device and a lithium ion secondary battery using the electrolyte.

With the recent development of electronic technology and increasing interest in environmental technology, various electrochemical devices are used. In particular, there are many requests for energy saving, and expectations for what can contribute to it are increasing. Conventionally, lithium ion secondary batteries, which are representative examples of power storage devices, have been mainly used as charging places for portable devices, but in recent years, they are expected to be used as batteries for hybrid vehicles and electric vehicles.
In such a flow, a higher energy density is required for the lithium ion secondary battery, and in order to achieve the higher energy density, higher voltage of the battery is being studied. In order to increase the voltage of the battery, it is necessary to use a positive electrode that operates at a high potential. Specifically, various positive electrode active materials that operate at 4.4 V (vsLi / Li ⁺ ) or higher have been proposed.
In a conventional lithium ion secondary battery that operates at a voltage of about 4 V, a nonaqueous electrolytic solution in which a lithium salt is dissolved in a nonaqueous solvent containing a carbonate solvent as a main component is widely used. The feature of this carbonate electrolyte is that it has a good balance between oxidation resistance and reduction resistance at a voltage of about 4 V, and is excellent in lithium ion conductivity. However, in a high-voltage lithium ion secondary battery using a positive electrode containing a positive electrode active material that operates at 4.4 V (vsLi / Li ⁺ ) or higher, the solvent of the carbonate electrolyte solution is oxidized and decomposed on the positive electrode surface. As a result, the cycle life is reduced.
In response to the above problem, Patent Document 1 proposes to improve stability at high potential by using fluorinated ethylene carbonate (EC) as a non-aqueous solvent for an electrolytic solution.

International Publication No. 2011-034162 Pamphlet

However, the fluorination of the non-aqueous solvent disclosed in Patent Document 1 is expensive, and there are problems that the solubility of the electrolyte is lowered and the conductivity of lithium ions is significantly lowered.
As described above, in the conventional technology, there is no solution for reduction in cycle life in a high-voltage lithium ion secondary battery using a positive electrode containing a positive electrode active material that operates at 4.4 V (vs Li / Li ⁺ ) or higher. It has not been.
In view of such circumstances, the present invention provides an electrolytic solution that realizes a lithium ion secondary battery having a high cycle life even when a positive electrode containing a positive electrode active material that operates at 4.4 V (vsLi / Li ⁺ ) or higher is used. The purpose is to provide.

  As a result of intensive studies to achieve the above object, the present inventors use an electrolytic solution containing a nonaqueous solvent, a lithium salt having a specific structure, and a specific lithium salt different from the lithium salt. Thus, it has been found that a lithium ion secondary battery having a high voltage drive and a high cycle life can be achieved, and the present invention has been completed.

That is, the present invention is as follows.
[1]
A lithium salt other than a non-aqueous solvent, a bifunctional acid lithium salt (A) represented by the following formula (1), and a bifunctional acid lithium salt represented by the following formula (1), having a boron atom An electrolyte solution for a non-aqueous storage device, comprising: a lithium salt (B) that is not used.

(Wherein R ₃ represents an optionally substituted hydrocarbon group having 0 to 10 carbon atoms, and X ⁻ represents a functional group selected from the group consisting of COO ⁻ , SO ₃ ⁻ , and O ⁻ ).
[2]
The content of the lithium bifunctional acid salt (A) is 0.001% by mass or more and 10% by mass or less with respect to the electrolytic solution, and the content of the lithium salt (B) is 1% by mass or more with respect to the electrolytic solution. The electrolyte solution for a non-aqueous electricity storage device according to the above [1], which is 40% by mass or less.
[3]
The electrolyte for a non-aqueous storage device according to the above [1] or [2], wherein the bifunctional acid lithium salt (A) is a dicarboxylic acid lithium salt.
[4]
The bifunctional acid lithium salt (A) is selected from the group consisting of lithium oxalate, lithium malonate, lithium difluoromalonate, lithium succinate, lithium tetrafluorosuccinate, lithium adipate, and lithium glutarate. The electrolyte solution for a non-aqueous storage device according to the above [1] or [2], which is the above lithium salt.
[5]
The non-aqueous solution according to any one of [1] to [4], wherein the electrolytic solution further contains a lithium salt (C) having a boron atom represented by the following formula (2) and / or formula (3). Electrolytic solution for electricity storage devices.

(In the formula, X represents a halogen atom selected from the group consisting of a fluorine atom, a chlorine atom, and a bromine atom, and R ₁ represents an optionally substituted hydrocarbon group having 1 to 10 carbon atoms. An integer of 0 or 1 is shown, and n is an integer of 0 to 2.)

Wherein X represents a halogen atom selected from the group consisting of a fluorine atom, a chlorine atom and a bromine atom, and R ₂ represents a hydrogen atom, a fluorine atom or an optionally substituted hydrocarbon having 1 to 10 carbon atoms. And m represents an integer of 0 to 4.)
[6]
The electrolyte solution for a non-aqueous electricity storage device according to the above [5], wherein the content of the lithium salt (C) is 0.01% by mass or more and 10% by mass or less with respect to the electrolyte solution.
[7]
The electrolyte solution for a non-aqueous electricity storage device according to any one of the above [1] to [6], wherein the non-aqueous solvent contains a cyclic carbonate and a chain carbonate.
[8]
The cyclic carbonate contains one or more carbonate solvents selected from the group consisting of ethylene carbonate and propylene carbonate, and the chain carbonate is selected from the group consisting of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Electrolyte solution for nonaqueous electrical storage devices in any one of said [1]-[7] containing the carbonate solvent of a seed | species or more.
[9]
The electrolyte solution for a non-aqueous electricity storage device according to any one of [1] to [8], wherein the lithium salt (B) is LiPF ₆ .
[10]
The lithium salt (C) is one or more selected from the group consisting of LiBF ₄ , LiB (C ₂ O ₄ ) ₂ , and LiBF ₂ (C ₂ O ₄ ), according to the above [5] to [9]. The electrolyte solution for nonaqueous electrical storage devices in any one.
[11]
An electrolyte for a nonaqueous electricity storage device according to any one of [1] to [10] above, a positive electrode containing a positive electrode active material that operates at a potential of 4.4 V (vsLi / Li ⁺ ) or higher, and a negative electrode. A lithium ion secondary battery.
[12]
The positive electrode active material operating in the 4.4V (vsLi / Li ⁺⁾ or more _{potential, LiMn 2-x Ma x O} 4 [Ma represents at least one element selected from transition metal, 0.2 ≦ x ≦ 0 .7. Spinel oxide represented by], Li ₂ MCO ₃ and LiMdO ₂ [Mc and Md represents one or more selected from independently a transition metal. And a general formula zLi ₂ McO ₃ — (1-z) LiMdO ₂ [0.1 ≦ z ≦ 0.9. LiMb _{1 -y} Fe _y PO ₄ [Mb represents one or more selected from Mn or Co, and 0 ≦ y ≦ 0.9. And an olivine-type positive electrode active material represented by the formula: Li ₂ MePO ₄ F [Me represents one or more selected from transition metals. ] The lithium ion secondary battery according to the above [11], which is at least one selected from the group consisting of:

  According to the present invention, it is possible to provide an electrolytic solution that realizes a lithium ion secondary battery that operates at a high voltage and has a high cycle life, and a lithium ion secondary battery that uses the electrolytic solution.

It is sectional drawing which shows roughly an example of the lithium ion secondary battery in this embodiment.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with appropriate modifications within the scope of the gist thereof.

In the present embodiment, the electrolyte for the non-aqueous storage device is:
A lithium salt other than a non-aqueous solvent, a bifunctional acid lithium salt (A) represented by the following formula (1), and a bifunctional acid lithium salt represented by the following formula (1), having a boron atom A lithium salt (B).

(Wherein R ₃ represents an optionally substituted hydrocarbon group having 0 to 10 carbon atoms, and X ⁻ represents a functional group selected from the group consisting of COO ⁻ , SO ₃ ⁻ , and O ⁻ ).

  The nonaqueous solvent used in the electrolytic solution in the present embodiment is not particularly limited, and various solvents can be used. For example, an aprotic polar solvent is preferable. Specific examples thereof include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, trifluoromethylethylene carbonate, fluoroethylene. Cyclic carbonates such as carbonate and 4,5-difluoroethylene carbonate; lactones such as γ-ptyrolactone and γ-valerolactone; cyclic sulfones such as sulfolane; cyclic ethers such as tetrahydrofuran and dioxane; ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methylpropyl Carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, Examples include chain carbonates such as tilpropyl carbonate and methyl trifluoroethyl carbonate; nitriles such as acetonitrile; chain ethers such as dimethyl ether; chain carboxylic acid esters such as methyl propionate; chain ether carbonate compounds such as dimethoxyethane. . These can be used individually by 1 type or in combination of 2 or more types.

  As the non-aqueous solvent, it is more preferable to use a carbonate-based solvent such as cyclic carbonate and chain carbonate from the viewpoint of ion conductivity. Further, it is more preferable to use a combination of a cyclic carbonate and a chain carbonate as the carbonate solvent. Although it does not specifically limit as a cyclic carbonate and various things can be used, For example, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate are preferable, and ethylene carbonate and propylene carbonate are more preferable. The chain carbonate is not particularly limited, and various types can be used. For example, ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate are preferable.

  When the carbonate solvent includes a combination of a cyclic carbonate and a chain carbonate, the mixing ratio of the cyclic carbonate and the chain carbonate is 1:10 to 5: 1 in terms of volume ratio from the viewpoint of ion conductivity. Preferably, it is 1: 5 to 3: 1.

  In the case of using a carbonate-based solvent, another nonaqueous solvent such as acetonitrile or sulfolane can be further added as necessary from the viewpoint of improving battery physical properties.

  The electrolyte for a non-aqueous electricity storage device in the present embodiment preferably contains a bifunctional acid lithium salt (A) represented by the following formula (1) in an amount of 0.001% by mass to 10% by mass with respect to the electrolyte. contains. When the content of the bifunctional acid lithium salt (A) is 0.001% by mass or more with respect to the electrolytic solution, good cycle performance tends to be exhibited, and 10% by mass or less with respect to the electrolytic solution. The good ionic conductivity tends to be ensured.

In the formula, R ₃ represents an optionally substituted hydrocarbon group having 0 to 10 carbon atoms, and X ⁻ represents a functional group selected from the group consisting of COO ⁻ , SO ₃ ⁻ , and O ⁻ .

In the difunctional acid lithium salt (A) represented by the formula (1), R ₃ represents an optionally substituted hydrocarbon group having 0 to 10 carbon atoms. From the viewpoint of improving the cycle performance, R ₃ The number of carbon atoms is preferably 0 to 6. When the number of carbon atoms is 0, R ₃ represents a bond. For example, when X ⁻ is COO ⁻ , the bifunctional lithium acid salt (A) is lithium oxalate. R ₃ may contain a different element such as oxygen, nitrogen, boron, fluorine, chlorine, and sulfur in addition to carbon and hydrogen. From the viewpoint of improving R ₃ and cycle performance, a methylene group, a difluoromethylene group, an ethylene group, a tetrafluoroethylene group, a propylene group, a butylene group, —CHCH ₃ —, and —C (CH ₃ ) ₂ — are preferable.

In the difunctional acid lithium salt (A) represented by the formula (1), X ⁻ represents a functional group selected from the group consisting of COO ⁻ , SO ₃ ⁻ , and O ⁻ , and is stable in the electrolytic solution. In view of the above, X ⁻ is preferably COO ⁻ or SO ₃ ⁻ , and more preferably COO ⁻ . That is, the difunctional acid lithium salt (A) is particularly preferably a dicarboxylic acid lithium salt.

  From the viewpoint of improving the cycle performance of the battery, the bifunctional acid lithium salt (A) represented by the formula (1) is lithium oxalate, lithium malonate, lithium difluoromalonate, lithium succinate, lithium tetrafluorosuccinate, Lithium adipate and lithium glutarate are preferred, lithium oxalate, lithium difluoromalonate, lithium succinate, lithium tetrafluorosuccinate, lithium adipate, lithium glutarate, and lithium oxalate, Lithium succinate, lithium adipate, and lithium glutarate are more preferable, and lithium succinate is particularly preferable.

  The content of the bifunctional acid lithium salt (A) represented by the formula (1) in the electrolytic solution is preferably 0.001% by mass or more from the viewpoint of improving the cycle performance of the battery, and preferably from the viewpoint of battery output. Is 10% by mass or less. The content of the bifunctional lithium salt (A) is more preferably 0.01% by mass or more and 5% by mass or less, further preferably 0.05% by mass or more and 5% by mass or less, and still more preferably 0.1% by mass. The content is not less than 3% by mass and not more than 3% by mass, particularly preferably not less than 0.2% by mass and not more than 3% by mass. In addition, the bifunctional lithium acid salt (A) may exist in a dispersed state in the electrolytic solution, or may be dissolved in the electrolytic solution.

  By adding the bifunctional acid lithium salt (A) represented by the formula (1) to the electrolytic solution, the cycle performance is greatly improved. Although the detailed mechanism has not been clarified, the bifunctional acid lithium salt (A) traps the acid component generated in the battery, suppresses the performance degradation of the battery, and further, on the positive electrode and / or negative electrode surface after the trap. It is considered that a protective film is formed to suppress a decrease in battery performance. As described above, the bifunctional lithium acid salt (A) is considered to have an effect of trapping the acid component on the surface of the dispersed particles even in a dispersed state insoluble in the electrolytic solution.

  The electrolyte solution for a non-aqueous electricity storage device in the present embodiment is a lithium salt other than the bifunctional lithium salt represented by the following formula (1), and contains a lithium salt (B) having no boron atom. The lithium salt (B) may have a function of suppressing the oxidative decomposition of the electrolytic solution by acting on the positive electrode, the negative electrode, or both, but mainly as an electrolyte responsible for the ionic conductivity of the electrolytic solution. The function is considered large. The content of the lithium salt (B) in the electrolyte solution is preferably 1% by mass or more with respect to the electrolyte solution from the viewpoint of ion conductivity, and preferably from the viewpoint of solubility at low temperatures with respect to the electrolyte solution. Is 40% by mass or less. The content of the lithium salt (B) is more preferably 5% by mass or more and 35% by mass or less, and further preferably 7% by mass or more and 30% by mass or less with respect to the electrolytic solution.

The structure of the lithium salt (B) may be any structure as long as it is a lithium salt structure other than the lithium salt represented by the formula (1) and does not have a boron atom in the molecular structure. However, from the viewpoint of ionic conductivity, LiPF ₆ , LiCIO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C _k F _{2k + 1} [k is an integer of 1 to 8], LiN (SO ₂ C _k F _{2k + 1} ) ₂ [k is an integer of 1 to 8], LiPF _n (C _k F _{2k + 1} ) _6-n [n is an integer of 1 to 5, k is an integer of 1 to 8], LiPF ₄ ( C ₂ O ₂ ), LiPF ₂ (C ₂ O ₂ ) ₂ , more preferably LiPF ₆ , LiOSO ₂ C _k F _{2k + 1} [k is an integer of 1 to 8], LiN (SO ₂ C _k F _{2k +} 1) ₂ [k is an integer of 1 to _{8], LiPF n (C k F 2k} + 1) 6-n [n is an integer of from 1 to 5, k is an integer of 1 to 8], _{iPF 4 (C 2 O 2)} , a _{LiPF 2 (C 2 O 2)} 2, more preferably LiPF _6. These electrolytes can be used singly or in combination of two or more.

  The electrolyte solution for a non-aqueous electricity storage device in the present embodiment contains 0.01% by mass of a lithium salt (C) having a boron atom represented by the following formula (2) and / or formula (3) with respect to the electrolyte solution. It is preferable to further contain 10% by mass or less.

In the formula, X represents a halogen atom selected from the group consisting of a fluorine atom, a chlorine atom, and a bromine atom, and R ₁ represents an optionally substituted hydrocarbon group having 1 to 10 carbon atoms. a represents an integer of 0 or 1, and n represents an integer of 0 to 2.

In the formula, X represents a halogen atom selected from the group consisting of a fluorine atom, a chlorine atom and a bromine atom, and R ₂ represents a hydrogen atom, a fluorine atom or an optionally substituted hydrocarbon group having 1 to 10 carbon atoms. Indicates. m shows the integer of 0-4.

  In the lithium salt (C) having a boron atom represented by the formula (2), X represents a halogen atom selected from the group consisting of a fluorine atom, a chlorine atom, and a bromine atom. From the viewpoint of chemical durability, a fluorine atom is preferred.

R ₁ represents an optionally substituted hydrocarbon group having 1 to 10 carbon atoms. The hydrocarbon group includes not only an aliphatic hydrocarbon group but also an aromatic hydrocarbon group such as a phenyl group. Further, a fluorine-substituted hydrocarbon group such as a difluoromethylene group in which all hydrogen atoms are substituted with fluorine atoms is also included. Further, if necessary, halogen atoms such as fluorine atom, chlorine atom, bromine atom, nitrile group (—CN), ether group (—O—), carbonate group (—OCO ₂ —), ester group (—CO _2- ), carbonyl group (—CO—) sulfide group (—S—), sulfoxide group (—SO—), sulfone group (—SO ₂ —), urethane group (—NHCO ₂ —) are introduced. be able to.

R ₁ has 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, and more preferably 1 to 6 carbon atoms, from the viewpoint of miscibility with a non-aqueous solvent.

Preferred examples of R ₁ include methylene group, ethylene group, 1-methylethylene group, propylene group, butylene group, 1,2-dimethylethylene group, 1,2-di (trifluoromethyl) ethylene group, fluoroethylene group. And an aliphatic hydrocarbon group such as a phenyl group, a nitrile-substituted phenyl group, and a fluorinated phenyl group. Among these, from the viewpoint of ion conductivity, methylene group, ethylene group, 1-methylethylene group, propylene group, 1,2-dimethylethylene group, 1,2-di (trifluoromethyl) ethylene group, fluoroethylene group Is more preferable.

  In formula (2), a represents an integer of 0 or 1, and a is preferably 0 from the viewpoint of stability. When a is 0, the structure on the right side in formula (2) is an oxalic acid structure. Moreover, n shows the integer of 0-2 in Formula (2).

  From the viewpoint of chemical durability in the lithium ion secondary battery, the lithium salt (C) having a boron atom represented by the formula (2) is represented by the following formulas (4) to (10). More preferably, it has a structure.

  In the lithium salt (C) having a boron atom represented by the formula (3), X represents a halogen atom selected from the group consisting of a fluorine atom, a chlorine atom, and a bromine atom. From the viewpoint of chemical durability, a fluorine atom is preferred.

R ₂ represents a hydrogen atom, a fluorine atom, or an optionally substituted hydrocarbon group having 1 to 10 carbon atoms. The hydrocarbon group includes not only an aliphatic hydrocarbon group but also an aromatic hydrocarbon group such as a phenyl group. Further, a fluorine-substituted hydrocarbon group such as a trifluoromethyl group in which all hydrogen atoms in the hydrocarbon group are substituted with fluorine atoms is also included. Further, if necessary, halogen atoms such as fluorine atom, chlorine atom, bromine atom, nitrile group (—CN), ether group (—O—), carbonate group (—OCO ₂ —), ester group (—CO _2- ), carbonyl group (—CO—) sulfide group (—S—), sulfoxide group (—SO—), sulfone group (—SO ₂ —), urethane group (—NHCO ₂ —) are introduced. be able to.

Preferred examples of R ₂ include aliphatic hydrocarbon groups such as methyl group, ethyl group, vinyl group, 1-methylvinyl group, propyl group, butyl group and trifluoromethyl group; benzyl group, phenyl group, nitrile substituted phenyl And aromatic hydrocarbon groups such as a fluorinated phenyl group. Among these, a methyl group, an ethyl group, a vinyl group, a 1-methylvinyl group, and a trifluoromethyl group are more preferable from the viewpoint of ion conductivity.

When R ₂ is a hydrocarbon group, from the viewpoint of miscibility with a non-aqueous solvent, R ₂ has 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, more preferably 1 to 1 carbon atoms. 6. Moreover, in Formula (3), m shows the integer of 0-4.

From the viewpoint of chemical durability in the lithium ion secondary battery, as the lithium salt (C) having a boron atom represented by the formula (3), LiBF ₄ , LiBF ₃ (OCOCH ₃ ), LiBF ₃ (OCOCF ₃ ), LiBF ₂ (OCOCH ₃ ) ₂ , LiBF ₂ (OCOCF ₃ ) ₂ , LiBF (OCOCH ₃ ) ₃ , LiBF (OCOCF ₃ ) ₃ , LiB (OCOCH ₃ ) ₄ , LiB (OCOCF ₃ ) ₄ More preferred.

  The electrolytic solution in this embodiment contains a lithium salt (C) having a boron atom represented by the formula (2) and / or the formula (3) in an amount of 0.01% by mass to 10% by mass with respect to the electrolytic solution. It is preferable to do. From the viewpoint of obtaining a good cycle life in the lithium ion secondary battery, the content of the lithium salt (C) is preferably 0.01% by mass or more, and preferably 10% by mass or less from the viewpoint of battery output. The content of the lithium salt (C) is more preferably 0.05% by mass or more and 5% by mass or less, further preferably 0.1% by mass or more and 5% by mass or less, and still more preferably 0.2% by mass or more and 3% by mass. % Or less, particularly preferably 0.5% by mass or more and 3% by mass or less.

  In the lithium ion secondary battery in the present embodiment, the cycle life of the lithium ion secondary battery can be significantly improved by containing the bifunctional lithium salt (A) in the electrolytic solution. By including lithium salt (C), the cycle life of the lithium ion secondary battery can be further improved. Although it is not clear as this reason, the lithium salt (C) which has a structure of Formula (2) or Formula (3) acts on a positive electrode, a negative electrode, or both, and oxidation of the electrolyte solution in a lithium ion secondary battery This is presumed to suppress decomposition. The lithium salt (C) also has a function as an electrolyte responsible for ionic conductivity, but mainly functions as an additive for the purpose of improving the cycle life, so that the content in the electrolytic solution is also 0.01. There is a tendency to exhibit a sufficient effect in a small amount of mass% or more and 10 mass% or less.

  The electrolytic solution in the present embodiment can contain additives other than the above-described bifunctional lithium salt (A), lithium salt (B), and lithium salt (C) as necessary. From the viewpoint of improving the cycle characteristics of the battery, it is preferable to contain vinylene carbonate, fluoroethylene carbonate, ethylene sulfite or the like as an additive.

  The electrolytic solution in the present embodiment is suitably used as an electrolytic solution for non-aqueous electricity storage devices. Here, the non-aqueous electricity storage device is an electricity storage device that does not use an aqueous solution as an electrolyte solution in the electricity storage device. Specifically, a lithium ion secondary battery, a sodium ion secondary battery, a calcium ion secondary battery, a lithium ion A capacitor etc. are mentioned. Among these, as a non-aqueous electricity storage device, a lithium ion secondary battery and a lithium ion capacitor are preferable from a viewpoint of practicality and durability, More preferably, it is a lithium ion secondary battery.

The lithium ion secondary battery in the present embodiment preferably has a positive electrode containing a positive electrode active material that operates at a potential of 4.4 V (vsLi / Li ⁺ ) or higher. Here, a positive electrode active material that operates at a potential of 4.4 V (vsLi / Li ⁺ ) or higher is charged and discharged as a positive electrode of a lithium ion secondary battery at a potential of 4.4 V (vs Li / Li ⁺ ). The positive electrode active material which can be obtained is shown. Therefore, 4.4 V (vsLi / Li ⁺ ) or more is sufficient at the time of full charge of a lithium ion secondary battery having a positive electrode containing the positive electrode active material, and 4.4 V (vsLi in the initial stage of charging or the end of discharging). / Li ⁺ ) or less. From the viewpoint of increasing the capacity of the lithium ion secondary battery, a positive electrode active material that operates at a potential of 4.5 V (vsLi / Li ⁺ ) or more is more preferable.

As the positive electrode active material that operates at a potential of 4.4 V (vsLi / Li ⁺ ) or higher, from the viewpoint of the structural stability of the positive electrode active material,
Formula LiMn _2-x Ma x O ₄ [Ma represents at least one element selected from transition metal, 0.2 ≦ x ≦ 0.7. ] A spinel type oxide represented by
Li ₂ McO ₃ and LiMdO ₂ [Mc and Md each independently represent one or more selected from transition metals. And a general formula zLi ₂ McO ₃ — (1-z) LiMdO ₂ [0.1 ≦ z ≦ 0.9. Li-excess layered oxide positive electrode active material represented by
LiMb _1-y Fe _y PO ₄ [Mb represents one or more selected from Mn or Co, and 0 ≦ y ≦ 0.9. And an olivine-type positive electrode active material represented by the formula: Li ₂ MePO ₄ F [Me represents one or more selected from transition metals. ],
One or more positive electrode active materials selected from the group consisting of:

Formula LiMn _2-x Ma x O ₄ [Ma represents at least one element selected from transition metal, 0.2 ≦ x ≦ 0.7. From the viewpoint of stability, it is preferable that the spinel type oxide represented by the formula has a structure represented by LiMn _2−x Ni _x O ₄ [0.2 ≦ x ≦ 0.7]. As a more preferable structure, LiMn _2-x Ni _x O ₄ [0.3 ≦ x ≦ 0.6] can be exemplified. More preferable structures include LiMn _1.5 Ni _0.5 O ₄ and LiMn _1.6 Ni _0.4 O ₄ . Here, the general formula LiMn _2-x Ma x O ₄ [Ma represents at least one element selected from transition metal, 0.2 ≦ x ≦ 0.7. In addition to the above structure, the spinel-type oxide represented by the above formula has a transition metal or transition in the range of 10 mol% or less with respect to the number of moles of Mn atoms from the viewpoint of stability of the positive electrode active material, electronic conductivity, Metal oxides can be included.

LiMb _1-y Fe _y PO ₄ [Mb represents one or more selected from Mn or Co, and 0 ≦ y ≦ 0.9. As the olivine-type positive electrode active material represented by the following formula, LiMn _1-y Fe _y PO ₄ [0.05 ≦ y ≦ 0.8], LiCo _1-y Fe _y PO ₄ from the viewpoint of stability and electron conductivity. It preferably has a structure represented by [0.05 ≦ y ≦ 0.8].

Li ₂ MePO ₄ F [Me represents one or more selected from transition metals. From the viewpoint of stability, the fluorinated olivine-type positive electrode active material represented by the following formula preferably has a structure represented by Li ₂ FePO ₄ F, Li ₂ MnPO ₄ F, or Li ₂ CoPO ₄ F.

Formula _{zLi 2 McO 3 - (1-} z) LiMdO 2 [Mc and Md represents one or more selected from transition metal independently. In terms of stability, the Li-excess layered oxide positive electrode active material represented by the following formula shows that Li ₂ McO ₃ has Mn, and zLi ₂ MnO ₃ — (1-z) LiNi _a Mn _b Co _c O ₂ [0.3 ≦ z ≦ 0.7, a + b + c = 1, 0.2 ≦ a ≦ 0.6, 0.2 ≦ b ≦ 0.6, 0.05 ≦ c ≦ 0.4] It is preferable to have. Above all, it has a structure of 0.4 ≦ z ≦ 0.6, a + b + c = 1, 0.3 ≦ a ≦ 0.4, 0.3 ≦ b ≦ 0.4, 0.2 ≦ c ≦ 0.3. It is more preferable.

The positive electrode active material that operates at a potential of 4.4 V (vsLi / Li ⁺ ) or higher can be used alone or in combination of two or more. It can also be used in combination with a positive electrode active material that operates at a potential of 4.4 V (vsLi / Li ⁺ ) or less. As a typical example of the positive electrode active material that operates at a potential of 4.4 V (vsLi / Li ⁺ ) or less, LiFePO ₄ can be given as an example.

  The positive electrode active material can be synthesized by the same method as a general inorganic oxide synthesis method. That is, a mixture in which a metal salt (for example, sulfate or nitrate) is mixed at a predetermined ratio is fired in an atmosphere containing oxygen, or a carbonate or hydroxide salt is added to a solution in which the metal salt is dissolved. It is made to act by precipitating a hardly soluble metal salt by extraction and mixing it with extraction and separation, and after mixing Li carbonate and Li hydroxide as a Li source, it is baked in an atmospheric environment containing oxygen. A positive electrode active material can be obtained.

  Here, an example of a method for manufacturing the positive electrode is described below. First, a positive electrode mixture-containing paste is prepared by dispersing, in a solvent, a positive electrode mixture prepared by adding a conductive additive, a binder, and 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. The positive electrode current collector is made of, for example, a metal foil such as an aluminum foil or a stainless steel foil.

  The lithium ion secondary battery in the present embodiment preferably has a 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 can be used. It is preferable that a negative electrode contains 1 or more types chosen from the group which consists of a material which can occlude and discharge | release lithium ion as a negative electrode active material. That is, the negative electrode includes a carbon negative electrode active material as a negative electrode active material, a negative electrode active material containing an element capable of forming an alloy with lithium, such as a silicon alloy negative electrode active material and a tin alloy negative electrode active material; a silicon oxide negative electrode active material; It is preferable to contain one or more negative electrode active materials selected from the group consisting of a negative electrode active material; and a lithium-containing compound typified by a lithium titanate negative electrode active material. These negative electrode active materials may be used individually by 1 type, and may be used in combination of 2 or more type.

  The carbon negative electrode active material is not particularly limited. For example, hard carbon, soft carbon, artificial graphite, natural graphite, graphite, pyrolytic carbon, coke, glassy carbon, a fired body of an organic polymer compound, mesocarbon microbeads , Carbon fiber, activated carbon, graphite, carbon colloid, and carbon black. 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, and is, for example, a material obtained by firing and carbonizing a polymer material such as a phenol resin or a furan resin at an appropriate temperature.

  Further, examples of the material capable of inserting and extracting lithium ions include a negative electrode active material containing an element capable of forming an alloy with lithium. The negative electrode active material may be a single metal or metalloid, an alloy or a compound, and may have at least a part of one or more of these phases. . 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 contain a nonmetallic element as long as it has metal properties as a whole.

  The metal element and the metalloid element 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 particularly preferable.

  The alloy of tin is not particularly limited. For example, as the second constituent element other than tin, silicon, magnesium (Mg), nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium (Ti) , One having at least one element selected from the group consisting of germanium, bismuth, antimony and chromium (Cr).

  The alloy of silicon 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 at least one element selected from the group consisting of chromium.

  The titanium compound, tin compound and 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 constituent element described above You may have.

  In addition, examples of a material capable of inserting and extracting lithium ions include lithium-containing compounds represented by a lithium titanate negative electrode active material.

  A negative electrode active material can be 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 can be measured by a wet particle size measuring device (for example, a laser diffraction / scattering particle size distribution meter, a dynamic light scattering particle size distribution meter). Alternatively, 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 can also be obtained by calculating an average. In this case, if 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 negative electrode is obtained as follows, for example. 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, thereby producing a negative electrode. The negative electrode current collector is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.

  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 such as graphite, acetylene black and ketjen black, and carbon fiber. The number average particle size (primary particle size) of the conductive assistant is preferably 0.1 μm to 100 μm, more preferably 1 μm to 10 μm, and is measured in the same manner as the number average particle size of the negative 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.

  The lithium ion secondary battery in this embodiment preferably includes a separator between the positive electrode and the negative electrode from the viewpoint of providing safety such as prevention of short circuit between the positive and negative electrodes and shutdown. As the separator, those similar to those provided in known lithium ion secondary batteries can be used, and among them, an insulating thin film having high ion permeability and excellent mechanical strength is preferable. Examples of the separator include a woven fabric, a nonwoven fabric, and a synthetic resin microporous membrane. Among these, a synthetic resin microporous membrane is preferable. As the synthetic resin microporous membrane, for example, a polyolefin microporous membrane such as a microporous membrane containing polyethylene or polypropylene as a main component or a microporous membrane containing both of these polyolefins is suitably used. The nonwoven fabric is not particularly limited, and for example, a porous film made of a heat resistant resin such as ceramic, polyolefin, polyester, polyamide, liquid crystal polyester, or aramid is used. The separator may be a single microporous membrane or a laminate of a plurality of microporous membranes, or may be a laminate of two or more microporous membranes.

  The lithium ion secondary battery according to the present embodiment includes, for example, a separator, a positive electrode and a negative electrode that sandwich the separator from both sides, a positive electrode current collector (disposed outside the positive electrode) that sandwiches the laminate, and a negative electrode current collector. A body (arranged outside the negative electrode) and a battery exterior housing them. A laminate in which a positive electrode, a separator, and a negative electrode are laminated is impregnated with an electrolytic solution.

  FIG. 1 is a schematic cross-sectional view of an example of a lithium ion secondary battery in the present embodiment. A lithium ion secondary battery 100 shown in FIG. 1 includes a separator 110, a positive electrode 120 and a negative electrode 130 that sandwich the separator 110 from both sides, and a positive electrode current collector 140 that sandwiches a laminate thereof (arranged outside the positive electrode). And a negative electrode current collector 150 (arranged outside the negative electrode) and a battery outer case 160 for housing them. A laminate in which the positive electrode 120, the separator 110, and the negative electrode 130 are laminated is impregnated with an electrolytic solution.

  The lithium ion secondary battery in the present embodiment can be produced by a known method using the above-described electrolytic solution, positive electrode, negative electrode, and, if necessary, a separator. For example, a plurality of positive electrodes in which a positive electrode and a negative electrode are wound in a laminated state with a separator interposed therebetween to be formed into a laminate having a wound structure, or they are alternately laminated by bending or laminating a plurality of layers. Then, the laminate is formed in a battery case (exterior), an electrolyte solution is injected into the case, and the laminate is made into an electrolyte solution. A lithium ion secondary battery can be manufactured by dipping and sealing. The shape of the lithium ion secondary battery in the present embodiment is not particularly limited, and for example, a cylindrical shape, an elliptical shape, a rectangular tube shape, a button shape, a coin shape, a flat shape, and a laminate shape are suitably employed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

[Example 1]
<Synthesis of positive electrode active material>
A solution A was obtained by dissolving 5.8 g of nickel sulfate hexahydrate, 3.5 g of cobalt sulfate heptahydrate, and 15.8 g of manganese sulfate pentahydrate in 50 mL of water. Sodium carbonate (10.6 g) and 28% by mass of ammonia water (3.4 mL) were mixed with water to obtain 50 mL of solution B.
Solution A and Solution B were added dropwise with stirring at a rate of 4 mL / min to obtain a precipitate. The obtained precipitate was separated by suction filtration, washed 5 times with pure water, and dried at 80 ° C. for 12 hours to obtain nickel / manganese / cobalt carbonate.
After adding lithium carbonate 2.2g to the said carbonate 4.7g and stirring well, it baked in air | atmosphere at 500 degreeC for 5 hours. Thereafter, the fired product was further stirred, and then fired at 900 ° C. for 5 hours to synthesize a positive electrode active material. As a result of structural analysis by X-ray diffraction, it was confirmed that it was a layered oxide and a Li-excess structure. As a result of elemental analysis, the composition was 0.5Li ₂ MnO ₃ —0.5LiNi _0.37 Mn _0.37 Co _0.26 O ₂ .

<Preparation of positive electrode>
The positive electrode active material, graphite (manufactured by TIMCAL, KS-6) and acetylene black powder (manufactured by Denki Kagaku Kogyo Co., HS-100) as a conductive additive, and a polyvinylidene fluoride solution (manufactured by Kureha, L # 7208) were mixed 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 30% 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.

<Production of negative electrode>
Graphite powder (OMAC1.2H / SS, manufactured by Osaka Gas Chemical Co., Ltd.) and graphite powder (manufactured by TIMCAL, SFG6) are used as the negative electrode active material, and styrene butadiene rubber (SBR) and an aqueous carboxymethylcellulose solution are used as the binder. The mixture was mixed at a solid content mass ratio of 10: 1.5: 1.8, and a slurry-like solution having a solid content concentration of 45 mass% was prepared using water as a dispersion medium. This slurry-like solution was applied to one side of a copper foil having a thickness of 18 μm, and the solvent was removed by drying, 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 negative electrode.

<Synthesis of lithium succinate>
After dissolving 7.1 g of lithium hydroxide monohydrate (Wako Pure Chemical Industries, 128-01215) in 30 mL of water, 10.0 g of succinic acid (Wako Pure Chemical Industries, 190-04332) was added. Then, after stirring at room temperature for 2 hours, water was removed under reduced pressure and vacuum dried at 80 ° C. for 12 hours to obtain 10.4 g of lithium succinate.

<Preparation of electrolyte>
Succinic acid synthesized by the above method was added to 9.9 g of solution A (LBG00069, manufactured by Kishida Chemical Co., Ltd.) containing 1 mol / L of LiPF ₆ salt in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 2. Electrolyte solution B was obtained by mixing and dispersing 0.1 g of lithium acid. Lithium succinate was not dissolved in the solution A, and the electrolytic solution B became a dispersion solution.
The content of lithium succinate in the electrolytic solution B was 1% by mass, and the content of LiPF ₆ was 13% by mass.

<Production of battery>
A SUS disk-shaped battery case in which a laminate in which a positive electrode and a negative electrode manufactured as described above are laminated on both sides of a polypropylene separator (film thickness: 25 μm, porosity: 50%, pore diameter: 0.1 μm to 1 μm) Inserted into. Next, 0.5 mL of electrolytic solution B in which lithium succinate was dispersed was injected into the battery case, and the laminate was immersed in electrolytic solution B, and then the battery case was sealed to produce a lithium ion secondary battery.

<Battery evaluation>
The obtained lithium ion secondary battery was put into a constant temperature bath (Futaba Scientific Co., Ltd., constant temperature bath PLM-73S) set at 25 ° C., and a charge / discharge device (Aska Electronics Co., Ltd. charge / discharge device ACD-01). Connected, and charged at a constant current of 0.1 C, and after reaching 4.7 V, charging was performed at a constant voltage of 4.7 V until the current value reached 50 μA, and 2.0 V at a constant current of 0.1 C. Discharge was performed. Subsequently, after charging with a constant current of 0.33 C and reaching 4.5 V, charging is performed with a constant voltage of 4.5 V until the current value reaches 50 μA, and then with a constant current of 0.33 C up to 2.0 V Discharge was performed. The discharge capacity at this time is defined as the initial discharge capacity. After that, the battery is charged with a constant current of 0.33 C. After reaching 4.5 V, the battery is charged with a constant voltage of 4.5 V until the current value reaches 50 μA, and discharged to 2.0 V with a constant current of 0.33 C. 50 cycles charge / discharge test was conducted with 1 cycle charge / discharge conditions. As a result, the initial discharge capacity was 248 mAh / g, and the discharge capacity at the first cycle was 204 mAh / g. The discharge capacity after 50 cycles was 181 mAh / g, and the discharge capacity retention rate obtained by dividing the discharge capacity at the 50th cycle by the discharge capacity at the 1st cycle was as high as 89%.

[Example 2]
<Preparation of electrolyte>
A solution A (LBG00069, manufactured by Kishida Chemical Co., Ltd.) containing 1 mol / L of LiPF ₆ salt in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 2 was added to 9.9 g of lithium oxalate (Japanese sum). 0.1 g (122-01252) manufactured by Kojun Pharmaceutical Co., Ltd. was mixed and dispersed to obtain an electrolytic solution C. Lithium oxalate was not dissolved in the solution A, and the electrolytic solution C became a dispersion solution.

The content of lithium oxalate in the electrolytic solution C was 1% by mass, and the content of LiPF ₆ was 13% by mass.
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the electrolytic solution C was used instead of the electrolytic solution B, and a 50-cycle charge / discharge test was performed. As a result, the initial discharge capacity was 247 mAh / g, and the discharge capacity at the first cycle was 203 mAh / g. The discharge capacity after 50 cycles was 176 mAh / g, and the discharge capacity retention rate obtained by dividing the discharge capacity at the 50th cycle by the discharge capacity at the 1st cycle was as high as 87%.

[Example 3]
<Synthesis of lithium glutarate>
After dissolving 6.4 g of lithium hydroxide monohydrate (manufactured by Wako Pure Chemical Industries, Ltd., 078-00542) in a mixed solvent of 10 mL of water and 15 mL of acetonitrile, glutaric acid (manufactured by Wako Pure Chemical Industries, Ltd., 190-04-332) 10 0.0 g was added. Then, after stirring at room temperature for 2 hours, water was removed under reduced pressure, and vacuum drying was performed at 80 ° C. for 12 hours to obtain 10.8 g of lithium glutarate.

<Preparation of electrolyte>
A solution A (LBG00069, manufactured by Kishida Chemical Co., Ltd.) containing 1 mol / L of LiPF ₆ salt in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 2 was synthesized into 9.9 g by the above method. 0.1 g of lithium glutarate was mixed and dispersed to obtain an electrolytic solution D. Lithium glutarate was not dissolved in the solution A, and the electrolytic solution D became a dispersion solution.

The content of lithium glutarate in the electrolytic solution D was 1% by mass, and the content of LiPF ₆ was 13% by mass.
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the electrolytic solution D was used instead of the electrolytic solution B, and a 50-cycle charge / discharge test was performed. As a result, the initial discharge capacity was 253 mAh / g, and the discharge capacity at the first cycle was 193 mAh / g. The discharge capacity after 50 cycles was 171 mAh / g, and the discharge capacity retention rate obtained by dividing the discharge capacity at the 50th cycle by the discharge capacity at the 1st cycle was as high as 89%.

[Example 4]
A solution A (LBG00069, manufactured by Kishida Chemical Co., Ltd.) containing 1 mol / L of LiPF ₆ salt in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 2 was added to 9.7 g by the formula (4). 0.2 g of lithium bisoxaborate represented by Lida 44382 (hereinafter, referred to as “LiBOB”, manufactured by Kishida Chemical Co., Ltd.) is mixed, and 0.1 g of lithium succinate synthesized in Example 1 is mixed and dispersed. Liquid E was obtained. Lithium succinate did not dissolve in solution A, and electrolyte solution E became a dispersion solution.

The content of LiBOB in the electrolytic solution E was 2% by mass, the content of lithium succinate was 1% by mass, and the content of LiPF ₆ was 13% by mass.
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the electrolytic solution E was used instead of the electrolytic solution B, and a 50-cycle charge / discharge test was performed. As a result, the initial discharge capacity was 255 mAh / g, and the discharge capacity at the first cycle was 207 mAh / g. The discharge capacity after 50 cycles was 187 mAh / g, and the discharge capacity retention rate obtained by dividing the discharge capacity at the 50th cycle by the discharge capacity at the 1st cycle was as high as 90%.

[Comparative Example 1]
A solution A (LBG00069, manufactured by Kishida Chemical Co., Ltd.) in which 1 mol / L of LiPF ₆ salt was contained in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 2 was used as an electrolytic solution F.
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the electrolytic solution F was used instead of the electrolytic solution B, and a 50-cycle charge / discharge test was performed. As a result, the initial discharge capacity was 252 mAh / g, and the discharge capacity at the first cycle was 197 mAh / g. The discharge capacity after 50 cycles was 140 mAh / g, and the discharge capacity retention ratio obtained by dividing the discharge capacity at the 30th cycle by the discharge capacity at the first cycle was as low as 71%.

  The results obtained in Examples 1 to 4 and Comparative Example 1 are shown in Table 1. From Table 1, it can be seen that the discharge capacity retention rate in the cycle test is significantly improved by adding a bifunctional acid lithium salt having a specific structure to the electrolytic solution.

  The lithium ion secondary battery using the electrolyte for non-aqueous electricity storage devices of the present invention has industrial applicability to various consumer equipment power supplies and automotive power supplies.

Claims (12)

A lithium salt other than a non-aqueous solvent, a bifunctional acid lithium salt (A) represented by the following formula (1), and a bifunctional acid lithium salt represented by the following formula (1), having a boron atom An electrolyte solution for a non-aqueous storage device, comprising: a lithium salt (B) that is not used.
(Wherein R ₃ represents an optionally substituted hydrocarbon group having 0 to 10 carbon atoms, and X ⁻ represents a functional group selected from the group consisting of COO ⁻ , SO ₃ ⁻ , and O ⁻ ).   The content of the lithium bifunctional acid salt (A) is 0.001% by mass or more and 10% by mass or less with respect to the electrolytic solution, and the content of the lithium salt (B) is 1% by mass or more with respect to the electrolytic solution. The electrolyte solution for non-aqueous electricity storage devices according to claim 1, wherein the electrolyte solution is 40% by mass or less.   The electrolyte solution for a nonaqueous electricity storage device according to claim 1 or 2, wherein the bifunctional lithium acid salt (A) is a dicarboxylic acid lithium salt.   The bifunctional acid lithium salt (A) is selected from the group consisting of lithium oxalate, lithium malonate, lithium difluoromalonate, lithium succinate, lithium tetrafluorosuccinate, lithium adipate, and lithium glutarate. The electrolyte solution for a non-aqueous electricity storage device according to claim 1 or 2, which is the above lithium salt. The nonaqueous electricity storage according to any one of claims 1 to 4, wherein the electrolytic solution further contains a lithium salt (C) having a boron atom represented by the following formula (2) and / or formula (3). Electrolyte for devices.
(In the formula, X represents a halogen atom selected from the group consisting of a fluorine atom, a chlorine atom, and a bromine atom, and R ₁ represents an optionally substituted hydrocarbon group having 1 to 10 carbon atoms. An integer of 0 or 1 is shown, and n is an integer of 0 to 2.)
Wherein X represents a halogen atom selected from the group consisting of a fluorine atom, a chlorine atom and a bromine atom, and R ₂ represents a hydrogen atom, a fluorine atom or an optionally substituted hydrocarbon having 1 to 10 carbon atoms. And m represents an integer of 0 to 4.)   The electrolyte solution for a non-aqueous storage device according to claim 5, wherein the content of the lithium salt (C) is 0.01% by mass or more and 10% by mass or less with respect to the electrolyte solution.   The electrolyte solution for a non-aqueous electricity storage device according to claim 1, wherein the non-aqueous solvent contains a cyclic carbonate and a chain carbonate.   The cyclic carbonate contains at least one carbonate solvent selected from the group consisting of ethylene carbonate and propylene carbonate, and the chain carbonate is selected from the group consisting of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The electrolyte solution for nonaqueous power storage devices according to any one of claims 1 to 7, comprising at least one carbonate solvent. The lithium salt (B) is a LiPF _6, a nonaqueous electricity storage device for the electrolytic solution of any one of claims 1-8. The lithium salt (C) is at least one selected from the group consisting of LiBF ₄ , LiB (C ₂ O ₄ ) ₂ , and LiBF ₂ (C ₂ O ₄ ). The electrolyte solution for nonaqueous electrical storage devices of claim | item. An electrolyte for a non-aqueous electricity storage device according to any one of claims 1 to 10, a positive electrode containing a positive electrode active material that operates at a potential of 4.4 V (vsLi / Li ⁺ ) or higher, and a negative electrode. Lithium ion secondary battery. The positive electrode active material operating in the 4.4V (vsLi / Li ⁺⁾ or more _{potential, LiMn 2-x Ma x O} 4 [Ma represents at least one element selected from transition metal, 0.2 ≦ x ≦ 0 .7. Spinel oxide represented by], Li ₂ MCO ₃ and LiMdO ₂ [Mc and Md represents one or more selected from independently a transition metal. And a general formula zLi ₂ McO ₃ — (1-z) LiMdO ₂ [0.1 ≦ z ≦ 0.9. LiMb _{1 -y} Fe _y PO ₄ [Mb represents one or more selected from Mn or Co, and 0 ≦ y ≦ 0.9. And an olivine-type positive electrode active material represented by the formula: Li ₂ MePO ₄ F [Me represents one or more selected from transition metals. The lithium ion secondary battery according to claim 11, which is at least one selected from the group consisting of: