JP6303507B2 - Non-aqueous electrolyte and power storage device using the same - Google Patents

Description

  The present invention relates to a nonaqueous electrolytic solution capable of improving electrochemical characteristics in a wide temperature range and an electricity storage device using the same.

In recent years, power storage devices, particularly lithium secondary batteries, have been widely used for small electronic devices such as mobile phones and notebook computers, electric vehicles, and power storage. Since these electronic devices and automobiles may be used in a wide temperature range such as a high temperature in midsummer or a low temperature of extremely cold, it is required to improve electrochemical characteristics in a wide range of temperatures.
In particular, in order to prevent global warming, there is an urgent need to reduce CO ₂ emissions. Among environmentally friendly vehicles equipped with power storage devices consisting of power storage devices such as lithium secondary batteries and capacitors, hybrid electric vehicles ( HEV), plug-in hybrid electric vehicles (PHEV), and battery electric vehicles (BEV) are required to spread quickly. Due to the long travel distance of automobiles, automobiles may be used in areas with a wide temperature range from extremely hot areas in the tropics to extremely cold areas. Therefore, in particular, these in-vehicle power storage devices are required not to deteriorate in electrochemical characteristics even when used in a wide temperature range from high temperature to low temperature.
In the present specification, the term lithium secondary battery is used as a concept including so-called lithium ion secondary batteries.

The lithium secondary battery is mainly composed of a positive electrode and a negative electrode containing a material capable of occluding and releasing lithium, a non-aqueous electrolyte composed of a lithium salt and a non-aqueous solvent, and the non-aqueous solvent includes ethylene carbonate (EC), Carbonates such as propylene carbonate (PC) are used.
In addition, as the negative electrode, metal lithium, metal compounds that can occlude and release lithium (metal simple substance, oxide, alloy with lithium, etc.) and carbon materials are known, and in particular, lithium can be occluded and released. Lithium secondary batteries using carbon materials such as coke, artificial graphite and natural graphite have been widely put into practical use.

For example, a lithium secondary battery using a highly crystallized carbon material such as natural graphite or artificial graphite as a negative electrode material is a decomposition product generated by reductive decomposition of a solvent in a non-aqueous electrolyte on the negative electrode surface during charging. It has been found that the gas interferes with the desired electrochemical reaction of the battery, resulting in poor cycle characteristics. Moreover, if the decomposition product of the nonaqueous solvent accumulates, the insertion and extraction of lithium into the negative electrode cannot be performed smoothly, and the electrochemical characteristics when used in a wide temperature range are liable to deteriorate.
Furthermore, lithium secondary batteries using lithium metal, alloys thereof, simple metals such as tin or silicon, and oxides as negative electrode materials have high initial capacities, but fine powders progress during the cycle. In comparison, it is known that reductive decomposition of a non-aqueous solvent occurs at an accelerated rate, and battery performance such as battery capacity and cycle characteristics is greatly reduced. In addition, if these anode materials are pulverized or decomposition products of nonaqueous solvents accumulate, lithium cannot be smoothly stored and released, and the electrochemical characteristics when used in a wide temperature range are likely to deteriorate. .

On the other hand, a lithium secondary battery using, for example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFePO _4, or the like as the positive electrode includes a positive electrode material, a non-aqueous electrolyte, and a non-aqueous solvent in a non-aqueous electrolyte in a charged state. The degradation products and gas generated by partial oxidative decomposition at the interface of the battery hinder the desired electrochemical reaction of the battery, which also causes degradation of electrochemical characteristics when used in a wide temperature range. I know.

As described above, the battery performance has been deteriorated due to the movement of lithium ions or the expansion of the battery due to the decomposition product or gas when the non-aqueous electrolyte is decomposed on the positive electrode or the negative electrode. In spite of such a situation, electronic devices equipped with lithium secondary batteries are becoming more and more multifunctional and power consumption is increasing. As a result, the capacity of lithium secondary batteries has been increasing, and the volume occupied by non-aqueous electrolyte in the battery has become smaller, such as increasing the electrode density and reducing the useless space volume in the battery. . Therefore, there is a situation in which the electrochemical characteristics when used in a wide temperature range are likely to deteriorate with a slight decomposition of the non-aqueous electrolyte.
Patent Document 1 proposes a nonaqueous electrolytic solution containing a phosphoric ester compound such as triethylphosphonoacetate, and shows that continuous charge characteristics and high-temperature storage characteristics can be improved.
Patent Document 2 proposes a nonaqueous electrolytic solution containing a sulfone compound such as bis (trimethylsilyl) -2,2-difluorosulfonylacetate, and shows that storage characteristics and cycle characteristics can be improved.

International Publication No. 2008/123038 Pamphlet JP 2008-146983 A

  An object of the present invention is to provide a nonaqueous electrolytic solution capable of improving electrochemical characteristics in a wide temperature range and an electricity storage device using the same.

As a result of detailed studies on the performance of the above-described conventional non-aqueous electrolytes, the present inventors have found that the non-aqueous electrolyte secondary batteries of Patent Document 1 and Patent Document 2 have a wide range of low-temperature discharge characteristics after storage at high temperatures. The actual situation is that the effect of improving the electrochemical characteristics in the temperature range can hardly be exhibited.
Therefore, the present inventors have made extensive studies to solve the above problems, and in a non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a non-aqueous solvent, one or more specific carboxylic acid lithium salts are added. It has been found that the inclusion in an amount can improve the electrochemical characteristics of the electricity storage device, particularly the electrochemical characteristics of the lithium battery, over a wide temperature range, thereby completing the present invention. Such an effect is not suggested at all in Patent Document 1 and Patent Document 2.

That is, the present invention provides the following (1), (2) and (3).
(1) A nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, containing one or more carboxylic acid lithium salts represented by the following general formula (I):

(In the formula, L represents a direct bond or a divalent linking group having 1 to 6 carbon atoms in which at least one hydrogen atom may be substituted with a halogen atom, and X represents the following general formula (II) or (III) Or any one of the substituents represented by

(Wherein R ¹ , R ² and R ³ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, or a carbon number) 6-12 aryl group, C1-C6 alkoxy group, C2-C6 alkenyloxy group, C3-C6 alkynyloxy group, C6-C12 aryl group, or C6-C6 12 aryloxy groups are shown.
In the alkyl group, alkenyl group, alkynyl group, aryl group, alkoxy group, alkenyloxy group, alkynyloxy group, and aryloxy group, at least one hydrogen atom of each group may be substituted with a halogen atom. )

(2) An electricity storage device including a non-aqueous electrolyte in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a non-aqueous solvent, wherein the non-aqueous electrolyte is a carboxylic acid represented by the general formula (I) An electricity storage device comprising at least one lithium salt.

(3) A lithium carboxylate represented by the following general formula (IV).

(In the formula, L ¹ represents a direct bond or a divalent linking group having 1 to 6 carbon atoms in which at least one hydrogen atom may be substituted with halogen, and X ¹ represents the following general formula (V) or (VI Or any one of the substituents represented by

(Wherein R ⁴ , R ⁵ and R ⁶ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, or a carbon number) 6-12 aryl group, C1-C6 alkoxy group, C2-C6 alkenyloxy group, C3-C6 alkynyloxy group, C6-C12 aryl group, or C6-C6 12 aryloxy groups are shown.
In the alkyl group, alkenyl group, alkynyl group, aryl group, alkoxy group, alkenyloxy group, alkynyloxy group, and aryloxy group, at least one hydrogen atom of each group may be substituted with a halogen atom. )

  ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous electrolyte which can improve the electrochemical characteristic of the electrical storage device in a wide temperature range, especially the low temperature discharge characteristic after high temperature storage, and electrical storage devices, such as a lithium battery using the same, can be provided. .

  The present invention relates to a non-aqueous electrolyte and an electricity storage device using the same.

[Non-aqueous electrolyte]
The non-aqueous electrolytic solution of the present invention is a non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a non-aqueous solvent, and the non-aqueous electrolytic solution contains at least one lithium carboxylate represented by the general formula (I) in the non-aqueous electrolytic solution. This is a non-aqueous electrolyte solution.

The reason why the nonaqueous electrolytic solution of the present invention can greatly improve the electrochemical characteristics of the electricity storage device in a wide temperature range is not necessarily clear, but is considered as follows.
The carboxylic acid lithium salt used in the present invention is a carboxylic acid lithium salt having a specific substituent X as described in the general formula (I). The site of the substituent X significantly improves the solubility of the lithium carboxylate represented by the general formula (I), and forms a dense and highly heat-resistant coating on the positive electrode and the negative electrode by electrochemical decomposition. Moreover, since the lithium carboxylate represented by the general formula is literally a lithium salt, the coating film is excellent in lithium ion conductivity. Therefore, compared with triethylphosphonoacetate described in Patent Document 1 and bis (trimethylsilyl) -2,2-difluorosulfonylacetate described in Patent Document 2, it is considered that electrochemical characteristics in a wide temperature range are remarkably improved.

  The specific lithium salt contained in the nonaqueous electrolytic solution of the present invention is represented by the following general formula (I).

(In the formula, L represents a direct bond or a divalent linking group having 1 to 6 carbon atoms in which at least one hydrogen atom may be substituted with a halogen atom, and X represents the following general formula (II) or (III) Or any one of the substituents represented by

(Wherein R ¹ , R ² and R ³ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, or a carbon number) 6-12 aryl group, C1-C6 alkoxy group, C2-C6 alkenyloxy group, C3-C6 alkynyloxy group, C6-C12 aryl group, or C6-C6 12 aryloxy groups are shown.
In the alkyl group, alkenyl group, alkynyl group, aryl group, alkoxy group, alkenyloxy group, alkynyloxy group, and aryloxy group, at least one hydrogen atom of each group may be substituted with a halogen atom. )

  L in the general formula (I) represents a direct bond or a divalent linking group having 1 to 6 carbon atoms in which at least one hydrogen atom may be substituted with a halogen atom, and is a direct bond or at least one hydrogen atom. Is preferably a divalent linking group having 1 to 4 carbon atoms which may be substituted with a halogen atom, a direct bond, or 2 having 1 to 2 carbon atoms in which at least one hydrogen atom may be substituted with a halogen atom. A valent linking group is more preferable, and a direct bond or a divalent linking group having 1 to 2 carbon atoms in which at least one hydrogen atom is substituted with a halogen atom is particularly preferable.

  Specific examples of L include methylene group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,1-diyl group, propane-1,3-diyl group, butane-1, Alkylene group such as 4-diyl group, pentane-1,5-diyl group or hexane-1,6-diyl group, fluoromethylene group, difluoromethylene group, chlorofluoromethylene group, 2,2,2-trifluoroethane -1,1-diyl group, 1-fluoroethane-1,1-diyl group, 1,2,2,2-tetrafluoroethane-1,1-diyl group, 1-chloro-3,3,3-tri Preferable examples include haloalkylene groups such as a fluoroethane-1,1-diyl group, 1,1,2,2-tetrafluoroethane-1,2-diyl group, and 1-fluoropropane-1,1-diyl group. Among them, methylene group, Tan-1,1-diyl group, fluoromethylene group, difluoromethylene group, chlorofluoromethylene group, 2,2,2-trifluoroethane-1,1-diyl group, 1-fluoroethane-1,1-diyl group 1,2,2,2-tetrafluoroethane-1,1-diyl group, 1-chloro-3,3,3-trifluoroethane-1,1-diyl group, 1,1,2,2-tetra Fluoroethane-1,2-diyl group is preferred, difluoromethylene group, chlorofluoromethylene group, 2,2,2-trifluoroethane-1,1-diyl group, 1,2,2,2-tetrafluoroethane-1 , 1-diyl group and 1-chloro-3,3,3-trifluoroethane-1,1-diyl group are more preferable.

R ¹ , R ² and R ³ in the general formula (II) or (III) are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or 3 to 3 carbon atoms. 6 alkynyl groups, C6-C12 aryl groups, C1-C6 alkoxy groups, C2-C6 alkenyloxy groups, C3-C6 alkynyloxy groups, C6-C12 aryls Group or an aryloxy group having 6 to 12 carbon atoms.
In the alkyl group, alkenyl group, alkynyl group, aryl group, alkoxy group, alkenyloxy group, alkynyloxy group, and aryloxy group, at least one hydrogen atom of each group may be substituted with a halogen atom.
Among them, an alkyl group having 1 to 4 carbon atoms in which at least one hydrogen atom may be substituted with a halogen atom, an alkoxy group having 1 to 4 carbon atoms in which at least one hydrogen atom may be substituted with a halogen atom, An alkenyloxy group having 2 to 5 carbon atoms, an alkynyloxy group having 3 to 5 carbon atoms, or a halogen atom is preferred, and an alkyl group having 1 to 2 carbon atoms in which at least one hydrogen atom may be substituted with a halogen atom, A C1-C2 alkoxy group, a C3-C4 alkynyloxy group, or a halogen atom in which at least one hydrogen atom may be substituted with a halogen atom is particularly preferable.

Specific examples of R ¹ , R ² and R ³ include halogen atoms such as fluorine atom, chlorine atom and bromine atom, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n- Linear alkyl group such as hexyl group, branched alkyl group such as iso-propyl group, sec-butyl group, tert-butyl group, tert-amyl group, 2-propenyl group, 2-butenyl group, 3- Alkenyl groups such as butenyl group, 2-methyl-2-propenyl group, 3-methyl-2-butenyl group, 2-propynyl group, 3-butynyl group, 1-methyl-2-propynyl group, 1,1-dimethyl- Linear alkyloxy groups such as alkynyl groups such as 2-propynyl groups, methoxy groups, ethoxy groups, n-propoxy groups, n-butoxy groups, n-pentyloxy groups, n-hexyloxy groups, i branched alkyloxy groups such as so-propoxy group, sec-butoxy group, tert-butoxy group, tert-amyloxy group, 2-propenyloxy group, 2-butenyloxy group, 3-butenyloxy group, 4-pentenyloxy group Alkenyloxy groups such as 5-hexenyloxy group, 2-propynyloxy group, 3-butynyloxy group, 4-pentynyloxy group, 5-hexynyloxy group, 2-methyl-2-propenyloxy group, 3-methyl-2 -Alkynyloxy group such as butenyloxy group, 2-propynyloxy group, 3-butynyloxy group, 4-pentynyloxy group, 5-hexynyloxy group, 1-methyl-2-propynyloxy group, 1,1-dimethyl-2- Alkynyloxy group such as propynyloxy group, fluoromethyl group, trif Alkyl group, 2-fluoroethoxy group, 2-chloroethoxy group in which a part of hydrogen atoms such as olomethyl group, chloromethyl group, 2-chloroethyl group, 2,2,2-trifluoroethyl group are substituted with halogen atoms An alkyloxy group in which a part of hydrogen atoms such as 2,2,2-trifluoroethoxy group is substituted with a halogen atom, phenyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, Aryl groups such as 2-fluorophenyl group, 3-fluorophenyl group, 4-fluorophenyl group, 4-chlorophenyl group, phenyloxy group, 2-methylphenyloxy group, 3-methylphenyloxy group, 4-methyl Phenyloxy group, 2-fluorophenyloxy group, 3-fluorophenyloxy group, 4-fluorophenyloxy group Preferred examples include aryloxy groups such as 4-chlorophenyloxy group, among which methyl group, ethyl group, n-propyl group, n-butyl group, methoxy group, ethoxy group, n-propoxy group, n-butoxy group, A 2-propenyloxy group, a 2-propynyloxy group, a fluorine atom, and a chlorine atom are preferable, and a methyl group, an ethyl group, a methoxy group, an ethoxy group, a 2-propynyloxy group, and a fluorine atom are more preferable.

  Specific examples of the specific carboxylic acid lithium salt represented by the general formula (I) include the following compounds.

Are preferable.

  Among the above preferred examples, compounds having a structural formula of A4 to A12, A18 to A27, A33 to A46, B4 to B12, B24 to B39, B42 to B48 are preferable, and A5, A6, A10 to A11, A19, A20, A23 are preferable. , A27, A34, A35, A37, A41, A44 to A46, B5, B6, B10 to B11, B26 to B29, B33, B37 to B39, and A42 to A48 are more preferred, and lithium 2-fluoro 2- (fluorosulfonyl) acetate (Structural Formula A4), lithium 2,2-difluoro-2- (fluorosulfonyl) acetate (Structural Formula A5), lithium 2-chloro-2-fluoro-2- (fluorosulfonyl) acetate (Structural Formula A6), lithium 3,3,3-trifluoro-2- (fluoros) Phonyl) propanoate (Structural Formula A7), lithium 2,3,3,3-terafluoro-2- (fluorosulfonyl) propanoate (Structural Formula A10), lithium 2,2,3,3-tetrafluoro-3- (fluorosulfonyl) ) Propanoate (Structural Formula A12), lithium 2,2-difluoro-2- (methylsulfonyl) acetate (Structural Formula A19), lithium 2,3,3,3-terafluoro-2- (methylsulfonyl) propanoate (Structural Formula A27) ), Lithium 2,2-difluoro-2- (methoxysulfonyl) acetate (Structural Formula A34), lithium 2,2-difluoro-2- (3,3,3-trifluoroethoxysulfonyl) acetate (Structural Formula A37), Lithium 2,2-difluoro-2-((2-propynyloxy) Sulfonyl) acetate (Structure A39), lithium 2-chloro-2-fluoro-2- (methoxysulfonyl) acetate (Structure A41), lithium 2,3,3,3-terafluoro-2- (methoxysulfonyl) propanoate ( Structural formula A44), lithium 1,1,2,2-tetrafluoro-3- (methoxysulfonyl) propanoate (structural formula A46), lithium 2- (difluorophosphoryl) -2,2-difluoroacetate (structural formula B5), Lithium 2- (dimethoxyphosphoryl) -2-fluoroacetate (Structural Formula B24), Lithium 2- (diethoxyphosphoryl) -2-fluoroacetate (Structural Formula B25), Lithium 2- (dimethoxyphosphoryl) -2,2-difluoro Acetate (Structural Formula B26), Lithium 2 (Diethoxyphosphoryl) -2,2-difluoroacetate (structural formula B27), lithium 2- (bis (2-propynyloxy) phosphoryl) -2,2-difluoroacetate (structural formula B31), lithium 2-chloro-2 -(Diethoxyphosphoryl) -2-fluoroacetate (structural formula B33), lithium 2- (diethoxyphosphoryl) -2,3,3,3-tetrafluoropropanoate (structural formula B37), lithium 2- (dimethoxy Phosphoryl) formate (Structural Formula B42), lithium 2- (diethoxyphosphoryl) formate (Structural Formula B43), lithium 2- (bis (2-propynyloxy) phosphoryl) formate (Structural Formula B47) is more preferred, 2-difluoro-2- (fluorosulfonyl) acetate Formula A5), lithium 2,3,3,3-terafluoro-2- (fluorosulfonyl) propanoate (Structural Formula A10), lithium 2,2-difluoro-2- (methylsulfonyl) acetate (Structural Formula A19), lithium 2,3,3,3-terafluoro-2- (methylsulfonyl) propanoate (Structural Formula A27), lithium 2,2-difluoro-2- (methoxysulfonyl) acetate (Structural Formula A34), lithium 2,2-difluoro- 2-((2-propynyloxy) sulfonyl) acetate (Structural Formula A39), lithium 2,3,3,3-terafluoro-2- (methoxysulfonyl) propanoate (Structural Formula A44), lithium 2- (dimethoxyphosphoryl)- 2,2-difluoro-acetate (Structural Formula B26), Lithium 2- (diethoxyphosphoryl) -2,2-difluoroacetate (structural formula B27), lithium 2- (diethoxyphosphoryl) -2,3,3,3-tetrafluoropropanoate (structural formula B37), lithium 2 Particularly preferred are-(dimethoxyphosphoryl) formate (structural formula B42), lithium 2- (diethoxyphosphoryl) formate (structural formula B43), and lithium 2- (bis (2-propynyloxy) phosphoryl) formate (structural formula B47).

  In the non-aqueous electrolyte of the present invention, the content of the specific lithium salt represented by the general formula (I) contained in the non-aqueous electrolyte is 0.001 to 10% by mass in the non-aqueous electrolyte. Preferably there is. If the content is 10% by mass or less, there is little possibility that a film is excessively formed on the electrode and the low-temperature characteristics are deteriorated, and if it is 0.001% by mass or more, the formation of the film is sufficient and a wide temperature range. The above range is preferable because the improvement effect of electrochemical characteristics in the range is enhanced. The content is more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more in the non-aqueous electrolyte. Moreover, the upper limit is more preferably 8% by mass or less, and further preferably 5% by mass or less.

  In the non-aqueous electrolyte of the present invention, the lithium carboxylate represented by the general formula (I) is combined with a non-aqueous solvent, an electrolyte salt, and other additives described below to perform electrochemical reaction over a wide temperature range. A unique effect of synergistically improving the characteristics is exhibited.

[Nonaqueous solvent]
As the nonaqueous solvent used in the nonaqueous electrolytic solution of the present invention, one or more selected from cyclic carbonates, chain esters, lactones, ethers, and amides are preferably exemplified. In order to improve the electrochemical properties synergistically over a wide temperature range, it is preferable that a chain ester is included, more preferably a chain carbonate is included, and both a cyclic carbonate and a chain carbonate are included. preferable.

  The term “chain ester” is used as a concept including a chain carbonate and a chain carboxylic acid ester.

  Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 4-fluoro-1,3-dioxolan-2-one (FEC), trans or Cis-4,5-difluoro-1,3-dioxolan-2-one (hereinafter collectively referred to as “DFEC”), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and 4-ethynyl-1 , 3-dioxolan-2-one (EEC) or two or more selected from ethylene carbonate, propylene carbonate, 4-fluoro-1,3-dioxolan-2-one, vinylene carbonate and 4-ethynyl- Selected from 1,3-dioxolan-2-one (EEC) One or two or more is more preferable.

  Further, it is preferable to use at least one of unsaturated carbonates such as carbon-carbon double bonds or carbon-carbon triple bonds or cyclic carbonates having a fluorine atom, since the electrochemical properties in a wide temperature range are further improved. -It is more preferable that both a cyclic carbonate containing an unsaturated bond such as a carbon double bond or a carbon-carbon triple bond and a cyclic carbonate having a fluorine atom are included. As the cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or carbon-carbon triple bond, VC, VEC, or EEC is more preferable, and as the cyclic carbonate having a fluorine atom, FEC or DFEC is more preferable.

  The content of the cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond is preferably 0.07% by volume or more, more preferably 0.8%, based on the total volume of the nonaqueous solvent. 2 vol% or more, more preferably 0.7 vol% or more, and the upper limit thereof is preferably 7 vol% or less, more preferably 4 vol% or less, further preferably 2.5 vol% or less. And, it is preferable because electrochemical characteristics in a wider temperature range can be further increased without impairing Li ion permeability.

  The content of the cyclic carbonate having a fluorine atom is preferably 0.07% by volume or more, more preferably 4% by volume or more, still more preferably 7% by volume or more, based on the total volume of the nonaqueous solvent. When the upper limit is preferably 35% by volume or less, more preferably 25% by volume or less, and further 15% by volume or less, electrochemical characteristics in a wider temperature range can be improved without impairing Li ion permeability. It is preferable because it is possible.

  When the non-aqueous solvent contains both a cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond and a cyclic carbonate having a fluorine atom, the carbon to the content of the cyclic carbonate having a fluorine atom The content of the cyclic carbonate having an unsaturated bond such as a carbon double bond or a carbon-carbon triple bond is preferably 0.2% by volume or more, more preferably 3% by volume or more, and further preferably 7% by volume or more. The upper limit is preferably 40% by volume or less, more preferably 30% by volume or less, and further 15% by volume or less, which improves electrochemical characteristics in a wider temperature range without impairing Li ion permeability. This is particularly preferable.

  In addition, when the non-aqueous solvent contains both ethylene carbonate and a cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or carbon-carbon triple bond, the electrochemistry over a wide temperature range of the film formed on the electrode It is preferable because the characteristics can be improved, and the content of ethylene carbonate and a cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond is preferably based on the total volume of the nonaqueous solvent. 3 volume% or more, more preferably 5 volume% or more, more preferably 7 volume% or more, and the upper limit thereof is preferably 45 volume% or less, more preferably 35 volume% or less, still more preferably 25 volume%. % Or less.

  These solvents may be used alone, and when used in combination of two or more, it is preferable because the effect of improving electrochemical characteristics over a wide temperature range is further improved, and used in combination of three or more. It is particularly preferable to do this. Preferred combinations of these cyclic carbonates include EC and PC, EC and VC, PC and VC, VC and FEC, EC and FEC, PC and FEC, FEC and DFEC, EC and DFEC, PC and DFEC, VC and DFEC , VEC and DFEC, VC and EEC, EC and EEC, EC and PC and VC, EC and PC and FEC, EC and VC and FEC, EC and VC and VEC, EC and VC and EEC, EC and EEC and FEC, PC And VC and FEC, EC and VC and DFEC, PC and VC and DFEC, EC and PC and VC and FEC, or EC and PC, VC and DFEC are preferable. Of the above combinations, EC and VC, EC and FEC, PC and FEC, EC and PC and VC, EC and PC and FEC, EC and VC and FEC, EC and VC and EEC, EC and EEC and FEC, PC and A combination of VC and FEC, or EC, PC, VC and FEC is more preferable.

  As the chain ester, one or more asymmetric chain carbonates selected from methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, and ethyl propyl carbonate, One or more symmetrical linear carbonates selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, and dibutyl carbonate, pivalate esters such as methyl pivalate, ethyl pivalate, and propyl pivalate Preferable examples include one or more chain carboxylic acid esters selected from methyl propionate, ethyl propionate, methyl acetate, and ethyl acetate (EA).

  Among the chain esters, chain esters having a methyl group selected from dimethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, methyl propionate, methyl acetate, and ethyl acetate are preferable, particularly methyl. A chain carbonate having a group is preferred.

  Moreover, when using chain carbonate, it is preferable to use 2 or more types. Further, it is more preferable that both a symmetric chain carbonate and an asymmetric chain carbonate are contained, and it is further more preferable that the content of the symmetric chain carbonate is more than that of the asymmetric chain carbonate.

  The content of the chain ester is not particularly limited, but it is preferably used in the range of 60 to 90% by volume with respect to the total volume of the nonaqueous solvent. If the content is 60% by volume or more, the viscosity of the non-aqueous electrolyte does not become too high, and if it is 90% by volume or less, the electrical conductivity of the non-aqueous electrolyte is lowered and electrochemical characteristics in a wide temperature range. The above range is preferable because there is little risk of decrease.

  The volume ratio of the symmetric chain carbonate in the chain carbonate is preferably 51% by volume or more, and more preferably 55% by volume or more. The upper limit is more preferably 95% by volume or less, and still more preferably 85% by volume or less. It is particularly preferred that the symmetric chain carbonate contains dimethyl carbonate. The asymmetric chain carbonate preferably has a methyl group, and methyl ethyl carbonate is particularly preferable. The above case is preferable because electrochemical characteristics in a wider temperature range are improved.

  The ratio between the cyclic carbonate and the chain ester is preferably 10:90 to 45:55, and 15:85 to 40:60, from the viewpoint of improving electrochemical properties at high temperatures. Is more preferable, and 20:80 to 35:65 is particularly preferable.

  Other nonaqueous solvents include cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, and 1,4-dioxane, chains such as 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. Preferable examples include one or two or more selected from amides such as cyclic ethers, amides such as dimethylformamide, sulfones such as sulfolane, and lactones such as γ-butyrolactone (GBL), γ-valerolactone and α-angelicalactone.

  The above non-aqueous solvents are usually used as a mixture in order to achieve appropriate physical properties. The combination includes, for example, a combination of a cyclic carbonate and a chain carbonate, a combination of a cyclic carbonate and a chain carboxylic acid ester, a combination of a cyclic carbonate, a chain carbonate and a lactone, and a combination of a cyclic carbonate, a chain carbonate and an ether. A combination or a combination of a cyclic carbonate, a chain carbonate, and a chain carboxylic acid ester is preferable.

For the purpose of improving electrochemical characteristics over a wider temperature range, it is preferable to add other additives to the non-aqueous electrolyte.
Specific examples of other additives include the following compounds (A) to (I).

(A) One or more nitriles selected from acetonitrile, propionitrile, succinonitrile, glutaronitrile, adiponitrile, pimeonitrile, suberonitrile, and sebacononitrile.

(B) cyclohexylbenzene, fluorocyclohexylbenzene compound (1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-4-cyclohexylbenzene), tert-butylbenzene, tert-amylbenzene, 1 Aromatic compounds having a branched alkyl group such as fluoro-4-tert-butylbenzene, biphenyl, terphenyl (o-, m-, p-isomer), diphenyl ether, fluorobenzene, difluorobenzene (o-, m -, P-form), anisole, 2,4-difluoroanisole, terphenyl partially hydride (1,2-dicyclohexylbenzene, 2-phenylbicyclohexyl, 1,2-diphenylcyclohexane, o-cyclohexylbiphenyl), etc. Aroma Compound.

(C) Selected from methyl isocyanate, ethyl isocyanate, butyl isocyanate, phenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 1,4-phenylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate One or more isocyanate compounds.

(D) 2-propynyl methyl carbonate, 2-propynyl acetate, 2-propynyl formate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2- (methanesulfonyloxy) propionate 2- Propynyl, di (2-propynyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, di (2-propynyl) glutarate, 2-butyne-1,4-diyl dimethanesulfonate, 2- One or more triple bond-containing compounds selected from butyne-1,4-diyl diformate and 2,4-hexadiyne-1,6-diyl dimethanesulfonate.

(E) 1,3-propane sultone, 1,3-butane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-propene sultone, 2,2-dioxide-1,2-oxathiolan-4-yl Acetate, or sultone such as 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, ethylene sulfite, hexahydrobenzo [1,3,2] dioxathiolane-2-oxide (1,2 -Cyclohexanediol cyclic sulfite), or cyclic sulfites such as 5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide, butane-2,3-diyl dimethanesulfonate, butane -1,4-diyl dimethanesulfonate, or methylenemethane disulfonate Phosphate esters, divinyl sulfone, 1,2-bis (vinylsulfonyl) ethane, or bis (2-vinylsulfonylethyl) one or two or more of the S = O group containing compound selected from vinyl sulfone compounds such as ethers.

(F) Cyclic acetal compounds such as 1,3-dioxolane, 1,3-dioxane and 1,3,5-trioxane.

(G) trimethyl phosphate, tributyl phosphate, and trioctyl phosphate,
Tris (2,2,2-trifluoroethyl) phosphate, bis (2,2,2-trifluoroethyl) methyl phosphate, bis (2,2,2-trifluoroethyl) ethyl phosphate, bisphosphate (2,2,2-trifluoroethyl) 2,2-difluoroethyl, bis (2,2,2-trifluoroethyl) phosphate 2,2,3,3-tetrafluoropropyl, bis (2, 2-difluoroethyl) 2,2,2-trifluoroethyl, bis (2,2,3,3-tetrafluoropropyl) phosphate, 2,2,2-trifluoroethyl phosphate and phosphoric acid (2,2,2- Trifluoroethyl) (2,2,3,3-tetrafluoropropyl) methyl, tris (1,1,1,3,3,3-hexafluoropropan-2-yl) phosphate, methyl methylenebisphosphonate, methylene bi Ethyl phosphonate, methyl ethylene bisphosphonate, ethyl ethylene bisphosphonate, methyl butylene bisphosphonate, ethyl butylene bisphosphonate, methyl 2- (dimethylphosphoryl) acetate, ethyl 2- (dimethylphosphoryl) acetate, methyl 2- (diethylphosphoryl) acetate Ethyl 2- (diethylphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2- (diethylphosphoryl) acetate, methyl 2- (dimethoxyphosphoryl) acetate, ethyl 2- (dimethoxyphosphoryl) acetate, Methyl 2- (diethoxyphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) acetate, 2-propynyl 2- (dimethoxyphosphoryl) acetate, 2 —Propinyl 2- (diethoxyphosphoryl) acetate, and one or more phosphorus-containing compounds selected from methyl pyrophosphate and ethyl pyrophosphate.

(H) Chain carboxylic anhydrides such as acetic anhydride and propionic anhydride, succinic anhydride, maleic anhydride, 3-allyl succinic anhydride, glutaric anhydride, itaconic anhydride, or 3-sulfo-propionic anhydride Cyclic acid anhydrides such as products.

(I) Cyclic phosphazene compounds such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, or ethoxyheptafluorocyclotetraphosphazene.

  Among these, it is preferable to include at least one selected from (A) nitrile, (B) aromatic compound, and (C) isocyanate compound, since the electrochemical characteristics in a wider temperature range are further improved.

  Among (A) nitriles, one or more selected from succinonitrile, glutaronitrile, adiponitrile, and pimelonitrile are more preferable.

  (B) Among aromatic compounds, one or more selected from biphenyl, terphenyl (o-, m-, p-isomer), fluorobenzene, cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene Are more preferable, and one or more selected from biphenyl, o-terphenyl, fluorobenzene, cyclohexylbenzene, and tert-amylbenzene are particularly preferable.

  Among (C) isocyanate compounds, one or more selected from hexamethylene diisocyanate, octamethylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate are more preferable.

  The content of the compounds (A) to (C) is preferably 0.01 to 7% by mass in the non-aqueous electrolyte. In this range, the film is sufficiently formed without becoming too thick, and the electrochemical characteristics in a wider temperature range are enhanced. The content is more preferably 0.05% by mass or more, more preferably 0.1% by mass or more in the non-aqueous electrolyte, and the upper limit thereof is more preferably 5% by mass or less, further preferably 3% by mass or less. .

  (D) Triple bond-containing compound, (E) Sultone, cyclic sulfite, sulfonic acid ester, cyclic S = O group-containing compound selected from vinyl sulfone, (F) cyclic acetal compound, (G) It is preferable to include a phosphorus-containing compound, (H) a cyclic acid anhydride, and (I) a cyclic phosphazene compound because the electrochemical properties in a wider temperature range are further improved.

  (D) As a triple bond containing compound, 2-propynyl methyl carbonate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2-propynyl 2- (methanesulfonyloxy) propionate, di One or more selected from (2-propynyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, and 2-butyne-1,4-diyl dimethanesulfonate, 2-propynyl methanesulfonate, One or more selected from 2-propynyl vinyl sulfonate, 2-propynyl 2- (methanesulfonyloxy) propionate, di (2-propynyl) oxalate, and 2-butyne-1,4-diyl dimethanesulfonate Preferred.

  (E) A cyclic or chain-containing S═O group-containing compound selected from sultone, cyclic sulfite, sulfonic acid ester, and vinyl sulfone (provided that the triple bond-containing compound and any of the above general formulas are specified) It is preferable to use a lithium salt.

  Examples of the cyclic S═O group-containing compound include 1,3-propane sultone, 1,3-butane sultone, 1,4-butane sultone, 2,4-butane sultone, 1,3-propene sultone, 2,2-dioxide- 1,2-oxathiolan-4-yl acetate, 5,5-dimethyl-1,2-oxathiolan-4-one 2,2-dioxide, methylene methane disulfonate, ethylene sulfite, and 4- (methylsulfonylmethyl)- One, two or more selected from 1,3,2-dioxathiolane 2-oxide are preferred.

  Examples of the chain-like S═O group-containing compound include butane-2,3-diyl dimethanesulfonate, butane-1,4-diyl dimethanesulfonate, dimethylmethane disulfonate, pentafluorophenyl methanesulfonate, divinylsulfone, And one or more selected from bis (2-vinylsulfonylethyl) ether are preferred.

  Among the cyclic or chain-containing S═O group-containing compounds, 1,3-propane sultone, 1,4-butane sultone, 2,4-butane sultone, 2,2-dioxide-1,2-oxathiolan-4-yl acetate , And 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, butane-2,3-diyl dimethanesulfonate, pentafluorophenyl methanesulfonate, divinylsulfone, or two or more thereof Is more preferable.

  (F) As the cyclic acetal compound, 1,3-dioxolane or 1,3-dioxane is preferable, and 1,3-dioxane is more preferable.

  (G) Phosphorus-containing compounds include tris phosphate (2,2,2-trifluoroethyl), tris phosphate (1,1,1,3,3,3-hexafluoropropan-2-yl), methyl 2- (dimethylphosphoryl) acetate, ethyl 2- (dimethylphosphoryl) acetate, methyl 2- (diethylphosphoryl) acetate, ethyl 2- (diethylphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2 -(Diethylphosphoryl) acetate, methyl 2- (dimethoxyphosphoryl) acetate, ethyl 2- (dimethoxyphosphoryl) acetate, methyl 2- (diethoxyphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) acetate, 2-propynyl 2- (Dimethoxyphospho Ryl) acetate or 2-propynyl 2- (diethoxyphosphoryl) acetate is preferred, and tris phosphate (2,2,2-trifluoroethyl), tris phosphate (1,1,1,3,3,3- Hexafluoropropan-2-yl), ethyl 2- (diethylphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2- (diethylphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) acetate, 2-propynyl 2- (dimethoxyphosphoryl) acetate or 2-propynyl 2- (diethoxyphosphoryl) acetate is more preferred.

  (H) As the cyclic acid anhydride, succinic anhydride, maleic anhydride, or 3-allyl succinic anhydride is preferable, and succinic anhydride or 3-allyl succinic anhydride is more preferable.

  (I) As the cyclic phosphazene compound, a cyclic phosphazene compound such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, or phenoxypentafluorocyclotriphosphazene is preferable, and methoxypentafluorocyclotriphosphazene or ethoxypentafluorocyclo More preferred is triphosphazene.

  The content of the compounds (D) to (I) is preferably 0.001 to 5% by mass in the non-aqueous electrolyte. In this range, the film is sufficiently formed without becoming too thick, and the electrochemical characteristics in a wider temperature range are enhanced. The content is more preferably 0.01% by mass or more, more preferably 0.1% by mass or more in the non-aqueous electrolyte, and the upper limit thereof is more preferably 3% by mass or less, and further preferably 2% by mass or less. .

In addition, for the purpose of improving electrochemical characteristics in a wider temperature range, a lithium salt having an oxalic acid skeleton, a lithium salt having a phosphoric acid skeleton, and a lithium salt having an S═O group are further included in the non-aqueous electrolyte. It is preferable to include one or more lithium salts selected from the inside.
Specific examples of lithium salts include lithium bis (oxalato) borate (LiBOB), lithium difluoro (oxalato) borate (LiDFOB), lithium tetrafluoro (oxalato) phosphate (LiTFOP), and lithium difluorobis (oxalato) phosphate (LiDFOP). Lithium salt having at least one oxalic acid skeleton selected from Lithium salt having phosphoric acid skeleton such as LiPO ₂ F ₂ and Li ₂ PO ₃ F, lithium trifluoro ((methanesulfonyl) oxy) borate (LiTFMSB), lithium Pentafluoro ((methanesulfonyl) oxy) phosphate (LiPFMSP), lithium methyl sulfate (LMS), lithium ethyl sulfate (LES), lithium 2,2,2-tri Le Oro ethylsulfate (LFES), and lithium salt preferably include having one or more S = O group selected from _{FSO 3 Li, LiBOB, LiDFOB,} LiTFOP, LiDFOP, LiPO 2 F 2, LiTFMSB, LMS, LES More preferably, it contains a lithium salt selected from LFES, LFES, and FSO ₃ Li.

The total content of one or more lithium salts selected from lithium salts having an oxalic acid skeleton, lithium salts having a phosphoric acid skeleton, and lithium salts having an S═O group is 0.001 in the non-aqueous electrolyte. -10 mass% is preferable. If the content is 10% by mass or less, a film is excessively formed on the electrode and is less likely to deteriorate the storage characteristics. If the content is 0.001% by mass or more, formation of the film is sufficient, The effect of improving the characteristics when used at a high voltage is increased. The content is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, and the upper limit is preferably 5% by mass or less in the non-aqueous electrolyte. 3 mass% or less is more preferable, and 2 mass% or less is still more preferable.
(Electrolyte salt)
Preferred examples of the electrolyte salt used in the present invention include the following lithium salts.
Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , and LiClO ₄ , LiN (SO ₂ F) ₂ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiCF ₃ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (iso-C ₃ F ₇ ) ₃ , LiPF ₅ (iso-C ₃ F ₇ ) and other lithium salts containing a chain-like fluorinated alkyl group, (CF ₂ ) ₂ (SO ₂ ) ₂ NLi, (CF ₂ ) ₃ (SO ₂ ) ₂ NLi, etc. Preferred examples include lithium salts having a cyclic fluorinated alkylene chain, and preferred examples include at least one lithium salt selected from these, and one or more of these may be used in combination. Can be used.
Among these, LiPF ₆ , LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , and one or more selected from LiN (SO ₂ F) ₂ are preferable, and LiPF Most preferably, ₆ is used. The concentration of the electrolyte salt is usually preferably 0.3 M or more, more preferably 0.7 M or more, and further preferably 1.1 M or more with respect to the non-aqueous solvent. Moreover, the upper limit is preferably 2.5M or less, more preferably 2.0M or less, and still more preferably 1.6M or less.
Moreover, as a preferable combination of these electrolyte salts, LiPF ₆ is included, and at least one lithium salt selected from LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ F) ₂ is non-preferable. The case where it is contained in the aqueous electrolyte is preferable, and when the proportion of the lithium salt other than LiPF _{6 in the} non-aqueous solvent is 0.001 M or more, the effect of improving electrochemical characteristics in a wide temperature range is exhibited. Since it is easy to be performed and it is 0.005M or less, there is little fear that the improvement effect of the electrochemical characteristic in a wide temperature range will fall, and it is preferable. Preferably it is 0.01M or more, Especially preferably, it is 0.03M or more, Most preferably, it is 0.04M or more. The upper limit is preferably 0.4M or less, particularly preferably 0.2M or less.

[Production of non-aqueous electrolyte]
The non-aqueous electrolyte of the present invention is, for example, mixed with the non-aqueous solvent, and added thereto the lithium salt of the carboxylic acid represented by the general formula (I) with respect to the electrolyte salt and the non-aqueous electrolyte. Can be obtained.
At this time, it is preferable that the compound added to the non-aqueous solvent and the non-aqueous electrolyte to be used is one that is purified in advance and has as few impurities as possible within a range that does not significantly reduce the productivity.

  The nonaqueous electrolytic solution of the present invention can be used in the following first to fourth power storage devices, and not only a liquid but also a gelled one can be used as the nonaqueous electrolyte. Furthermore, the non-aqueous electrolyte of the present invention can be used for a solid polymer electrolyte. In particular, it is preferably used for the first electricity storage device (that is, for a lithium battery) or the fourth electricity storage device (that is, for a lithium ion capacitor) that uses a lithium salt as an electrolyte salt, and is used for a lithium battery. More preferably, it is more preferably used for a lithium secondary battery.

[First power storage device (lithium battery)]
In this specification, the lithium battery is a general term for a lithium primary battery and a lithium secondary battery. In this specification, the term lithium secondary battery is used as a concept including a so-called lithium ion secondary battery. The lithium battery of the present invention comprises the nonaqueous electrolyte solution in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a nonaqueous solvent. Components other than the non-aqueous electrolyte, such as a positive electrode and a negative electrode, can be used without particular limitation.
For example, as the positive electrode active material for a lithium secondary battery, a composite metal oxide with lithium containing one or more selected from cobalt, manganese and nickel is used. These positive electrode active materials can be used individually by 1 type or in combination of 2 or more types.
Examples of such a lithium composite metal oxide include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiCo _1-x Ni _x O ₂ (0.01 <x <1), LiCo _1/3 Ni _1/3. One type or two or more types selected from Mn _1/3 O ₂ , LiNi _1/2 Mn _3/2 O ₄ , and LiCo _0.98 Mg _0.02 O ₂ may be mentioned. Moreover, LiCoO ₂ and LiMn ₂ O _4, LiCoO ₂ and LiNiO _2, may be used in combination as LiMn ₂ O ₄ and LiNiO _2.

In addition, in order to improve safety and cycle characteristics during overcharge, or to enable use at a charging potential of 4.3 V or higher, a part of the lithium composite metal oxide may be substituted with another element. . For example, a part of cobalt, manganese, nickel is replaced with at least one element such as Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, Cu, Bi, Mo, La, A part of O can be substituted with S or F, or a compound containing these other elements can be coated.
Among these, lithium composite metal oxides such as LiCoO ₂ , LiMn ₂ O ₄ , and LiNiO ₂ that can be used at a charged potential of the positive electrode in a fully charged state of 4.3 V or more on the basis of Li are preferable, and LiCo _1-x M _x O ₂ (where M is one or more elements selected from Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, and Cu, 0.001 ≦ x ≦ 0. 05), LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _1/2 Mn _3/2 O ₄ , Li ₂ MnO ₃ and LiMO ₂ (M is a transition of Co, Ni, Mn, Fe, etc.) A lithium composite metal oxide that can be used at 4.4 V or higher, such as a solid solution with (metal), is more preferable. When a lithium composite metal oxide that operates at a high charging voltage is used, the electrochemical characteristics when used in a wide temperature range are liable to deteriorate due to a reaction with the electrolyte during charging, but the lithium secondary battery according to the present invention Then, the deterioration of these electrochemical characteristics can be suppressed.
In particular, in the case of a positive electrode containing Mn, the resistance of the battery tends to increase with the elution of Mn ions from the positive electrode, so that the electrochemical characteristics when used in a wide temperature range tend to be lowered. The lithium secondary battery according to the invention is preferable because it can suppress a decrease in these electrochemical characteristics.

Furthermore, lithium-containing olivine-type phosphate can also be used as the positive electrode active material. In particular, lithium-containing olivine-type phosphate containing one or more selected from iron, cobalt, nickel and manganese is preferable. Specific examples thereof include one or more selected from LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , and LiMnPO ₄ .
Some of these lithium-containing olivine-type phosphates may be substituted with other elements, and some of iron, cobalt, nickel, and manganese are replaced with Co, Mn, Ni, Mg, Al, B, Ti, V, and Nb. , Cu, Zn, Mo, Ca, Sr, W, and Zr may be substituted with one or more elements selected from these, or may be coated with a compound or carbon material containing these other elements. Among these, LiFePO ₄ or LiMnPO ₄ is preferable.
Moreover, lithium containing olivine type | mold phosphate can also be mixed with the said positive electrode active material, for example, and can be used.

As the positive electrode for lithium primary _{battery, CuO, Cu 2 O, Ag} 2 O, Ag 2 CrO 4, CuS, CuSO 4, TiO 2, TiS 2, SiO 2, SnO, V 2 O 5, V 6 O 12 , VO _x , Nb ₂ O ₅ , Bi ₂ O ₃ , Bi ₂ Pb ₂ O ₅ , Sb ₂ O ₃ , CrO ₃ , Cr ₂ O ₃ , MoO ₃ , WO ₃ , SeO ₂ , MnO ₂ , Mn ₂ O ₃ , Fe ₂ O ₃ , FeO, Fe ₃ O ₄ , Ni ₂ O ₃ , NiO, CoO ₃ , CoO and other oxides or chalcogen compounds of one or more metal elements, sulfur such as SO ₂ and SOCl ₂ Examples thereof include a compound and fluorocarbon (fluorinated graphite) represented by the general formula (CF _x ) _n . Among _{these, MnO 2, V 2 O 5} , fluorinated graphite and the like are preferable.

When the pH of the supernatant liquid when 10.0 g of the positive electrode active material is dispersed in 100 ml of distilled water is 10.0 to 12.5, the effect of improving the electrochemical characteristics in a wider temperature range can be easily obtained. The case of 10.5 to 12.0 is more preferable.
Further, when Ni is contained as an element in the positive electrode, since impurities such as LiOH in the positive electrode active material tend to increase, an effect of improving electrochemical characteristics in a wider temperature range is easily obtained, which is preferable. The case where the atomic concentration of Ni in the substance is 5 to 25 atomic% is more preferable, and the case where it is 8 to 21 atomic% is particularly preferable.

  The conductive agent for the positive electrode is not particularly limited as long as it is an electron conductive material that does not cause a chemical change. For example, graphite such as natural graphite (scaly graphite, etc.), graphite such as artificial graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, and one or more carbon blacks selected from thermal black It is done. Further, graphite and carbon black may be appropriately mixed and used. 1-10 mass% is preferable and, as for the addition amount to the positive mix of a electrically conductive agent, 2-5 mass% is especially preferable.

The positive electrode is composed of a conductive agent such as acetylene black and carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), a copolymer of styrene and butadiene (SBR), acrylonitrile and butadiene. Mixing with a binder such as copolymer (NBR), carboxymethyl cellulose (CMC), ethylene propylene diene terpolymer, etc., and adding a high boiling point solvent such as 1-methyl-2-pyrrolidone to knead and mix Then, this positive electrode mixture was applied to a current collector aluminum foil, a stainless steel lath plate, etc., dried and pressure-molded, and then subjected to vacuum at a temperature of about 50 ° C. to 250 ° C. for about 2 hours. It can be manufactured by heat treatment.
The density of the part except the collector of the positive electrode is usually at 1.5 g / cm ³ or more, for further increasing the capacity of the battery, it is preferably 2 g / cm ³ or more, more preferably, 3 g / cm ³ It is above, More preferably, it is 3.6 g / cm ³ or more. The upper limit is preferably 4 g / cm ³ or less.

Examples of the negative electrode active material for a lithium secondary battery include lithium metal, lithium alloy, and a carbon material capable of occluding and releasing lithium (easily graphitized carbon and a (002) plane spacing of 0.37 nm or more). Non-graphitizable carbon, graphite with (002) plane spacing of 0.34 nm or less, etc.], tin (single), tin compound, silicon (single), silicon compound, lithium titanate such as Li ₄ Ti ₅ O ₁₂ A compound etc. can be used individually by 1 type or in combination of 2 or more types.
Among these, it is more preferable to use a highly crystalline carbon material such as artificial graphite or natural graphite in terms of the ability to occlude and release lithium ions, and the lattice spacing ( ₀₀₂ ) has an interplanar spacing (d ₀₀₂ ) of 0.1. It is more preferable to use a carbon material having a graphite type crystal structure of 340 nm (nanometer) or less, particularly 0.335 to 0.337 nm.
In particular, artificial graphite particles having a massive structure in which a plurality of flat graphite fine particles are assembled or bonded non-parallel to each other, and mechanical actions such as compressive force, frictional force, shearing force, etc. are repeatedly applied, and scaly natural graphite is spherical. It is preferable to use particles that have been treated.
The peak intensity I (110) of the (110) plane of the graphite crystal obtained from the X-ray diffraction measurement of the negative electrode sheet when the density of the portion excluding the current collector of the negative electrode is pressed to a density of 1.5 g / cm ³ or more. ) And the (004) plane peak intensity I (004) ratio I (110) / I (004) is preferably 0.01 or more because the electrochemical characteristics in a wider temperature range are further improved. More preferably, it is more preferably 0.1 or more. In addition, since the crystallinity may be lowered due to excessive treatment and the discharge capacity of the battery may be lowered, the upper limit of the peak intensity ratio I (110) / I (004) is preferably 0.5 or less. 3 or less is more preferable.
In addition, it is preferable that the highly crystalline carbon material (core material) is coated with a carbon material having lower crystallinity than the core material because electrochemical characteristics in a wide temperature range are further improved. The crystallinity of the coating carbon material can be confirmed by TEM.
When a highly crystalline carbon material is used, it reacts with the non-aqueous electrolyte during charging and tends to lower the electrochemical characteristics at low or high temperatures due to an increase in interface resistance. However, in the lithium secondary battery according to the present invention, Excellent electrochemical characteristics over a wide temperature range.

  Examples of the metal compound capable of inserting and extracting lithium as the negative electrode active material include Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, and Cu. , Zn, Ag, Mg, Sr, Ba, and other compounds containing at least one metal element. These metal compounds may be used in any form such as a simple substance, an alloy, an oxide, a nitride, a sulfide, a boride, and an alloy with lithium, but any of a simple substance, an alloy, an oxide, and an alloy with lithium. Is preferable because the capacity can be increased. Among these, those containing at least one element selected from Si, Ge and Sn are preferable, and those containing at least one element selected from Si and Sn are more preferable because the capacity of the battery can be increased.

The negative electrode is kneaded using the same conductive agent, binder, and high-boiling solvent as in the production of the positive electrode, and then the negative electrode mixture is applied to the copper foil of the current collector. After being dried and pressure-molded, it can be produced by heat treatment under vacuum at a temperature of about 50 ° C. to 250 ° C. for about 2 hours.
The density of the portion excluding the current collector of the negative electrode is usually 1.1 g / cm ³ or more, and is preferably 1.5 g / cm ³ or more, more preferably 1.7 g in order to further increase the battery capacity. / Cm ³ or more. The upper limit is preferably 2 g / cm ³ or less.

  Moreover, lithium metal or a lithium alloy is mentioned as a negative electrode active material for lithium primary batteries.

The structure of the lithium battery is not particularly limited, and a coin-type battery, a cylindrical battery, a square battery, a laminated battery, or the like having a single-layer or multi-layer separator can be applied.
Although there is no restriction | limiting in particular as a separator for batteries, The single layer or laminated microporous film of polyolefin, such as a polypropylene and polyethylene, a woven fabric, a nonwoven fabric, etc. can be used.

  The lithium secondary battery according to the present invention has excellent electrochemical characteristics in a wide temperature range even when the end-of-charge voltage is 4.2 V or more, particularly 4.3 V or more, and the characteristics are also good at 4.4 V or more. is there. The end-of-discharge voltage is usually 2.8 V or more, and further 2.5 V or more, but the lithium secondary battery in the present invention can be 2.0 V or more. Although it does not specifically limit about an electric current value, Usually, it uses in the range of 0.1-30C. Moreover, the lithium battery in this invention can be charged / discharged at -40-100 degreeC, Preferably it is -10-80 degreeC.

  In the present invention, as a countermeasure against an increase in the internal pressure of the lithium battery, a method of providing a safety valve on the battery lid or cutting a member such as a battery can or a gasket can be employed. Further, as a safety measure for preventing overcharge, the battery lid can be provided with a current interruption mechanism that senses the internal pressure of the battery and interrupts the current.

[Second power storage device (electric double layer capacitor)]
It is an electricity storage device that stores energy by using the electric double layer capacity at the interface between the electrolyte and the electrode. An example of the present invention is an electric double layer capacitor. The most typical electrode active material used for this electricity storage device is activated carbon. Double layer capacity increases roughly in proportion to surface area.

[Third power storage device]
It is an electrical storage device which stores energy using dope / dedope reaction of an electrode. Examples of the electrode active material used in this power storage device include metal oxides such as ruthenium oxide, iridium oxide, tungsten oxide, molybdenum oxide, and copper oxide, and π-conjugated polymers such as polyacene and polythiophene derivatives. Capacitors using these electrode active materials can store energy associated with electrode doping / dedoping reactions.

[Fourth storage device (lithium ion capacitor)]
It is an electricity storage device that stores energy by utilizing lithium ion intercalation with a carbon material such as graphite as a negative electrode. It is called a lithium ion capacitor (LIC). Examples of the positive electrode include those using an electric double layer between an activated carbon electrode and an electrolytic solution, and those using a π-conjugated polymer electrode doping / dedoping reaction. The electrolytic solution contains at least a lithium salt such as LiPF ₆ .

  In the above-described configuration example of the electricity storage device, an example in which the carboxylic acid lithium salt represented by the general formula (I) is contained in the electrolyte solution has been described. You may contain in.

  In the second to fourth aspects described below, examples of the electricity storage device in which the carboxylic acid lithium salt represented by the general formula (I) is added in advance to other components other than the electrolytic solution will be described.

[Second Embodiment: Example of Adding Lithium Carboxylic Acid Salt Represented by General Formula (I) to the Positive Electrode]
The lithium carboxylate represented by the general formula (I) is mixed with the positive electrode active material, the conductive agent, and the binder described above, and a high boiling point solvent such as 1-methyl-2-pyrrolidone is added thereto and kneaded. After forming the positive electrode mixture, the positive electrode mixture is applied to an aluminum foil of a current collector or a stainless lath plate, dried, and pressure-molded, and then heated at a temperature of about 50 ° C. to 250 ° C. It can be produced by heat treatment under vacuum for about an hour.

  The addition amount of the lithium carboxylate represented by the general formula (I) is preferably 0.001 to 10% by mass with respect to the positive electrode active material. The addition amount is more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more with respect to the positive electrode active material. Moreover, the upper limit is more preferably 8% by mass or less, and further preferably 5% by mass or less.

[Third embodiment: Example of adding lithium salt represented by general formula (I) to negative electrode]
The lithium carboxylate represented by the general formula (I) is kneaded using the same conductive agent, binder, and high-boiling solvent as in the production of the positive electrode to obtain a negative electrode mixture. It can be produced by applying to a copper foil or the like of a current collector, drying and press-molding, and then heat-treating under vacuum at a temperature of about 50 ° C. to 250 ° C. for about 2 hours.

  The addition amount of the carboxylic acid lithium salt represented by the general formula (I) is preferably 0.001 to 10% by mass with respect to the negative electrode active material. The addition amount is more preferably 0.05% by mass or more, and still more preferably 0.1% by mass or more with respect to the negative electrode active material. Moreover, the upper limit is more preferably 8% by mass or less, and further preferably 5% by mass or less.

[Fourth Embodiment: Example of Adding Lithium Carboxylic Acid Salt Represented by General Formula (I) to the Separator]
The lithium carboxylate represented by the general formula (I) is obtained by immersing the separator in a solution obtained by dissolving the lithium carboxylate represented by the general formula (I) in an organic solvent or water and then impregnating the separator, followed by drying. Can be produced. Moreover, it can produce by preparing the coating liquid which disperse | distributed the carboxylic acid lithium salt represented by general formula (I) to the organic solvent and water, and apply | coating a coating liquid to the whole surface of a separator.

  The carboxylic acid lithium salt which is a novel compound of the present invention is represented by the following general formula (IV).

(In the formula, L ¹ represents a direct bond or a divalent linking group having 1 to 6 carbon atoms in which at least one hydrogen atom may be substituted with halogen, and X ¹ represents the following general formula (V) or (VI Or any one of the substituents represented by

(Wherein R ⁴ , R ⁵ and R ⁶ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, or a carbon number) 6-12 aryl group, C1-C6 alkoxy group, C2-C6 alkenyloxy group, C3-C6 alkynyloxy group, C6-C12 aryl group, or C6-C6 12 aryloxy groups are shown.
In the alkyl group, alkenyl group, alkynyl group, aryl group, alkoxy group, alkenyloxy group, alkynyloxy group, and aryloxy group, at least one hydrogen atom of each group may be substituted with a halogen atom. )

In the general formula (II), the substituents L ¹ , R ⁴ , R ⁵ and R ⁶ have the same meanings as L, R ¹ , R ² and R ³ in the general formula (I).

  Specific compounds represented by the general formula (IV) are the same as the description and preferred descriptions of the specific compounds of the general formula (I).

  The carboxylic acid lithium salt represented by the general formula (IV) of the present invention is obtained by a known method for converting a carboxylic acid compound into a lithium salt, but is not limited to this production method.

  Examples of the electrolytic solution using the carboxylic acid lithium salt of the present invention will be shown below, but the present invention is not limited to these examples.

Examples 1 to 23, Comparative Examples 1 to 3
[Production of lithium ion secondary battery]
LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ; 94% by mass, acetylene black (conductive agent); 3% by mass are mixed, and polyvinylidene fluoride (binder); In addition to the solution dissolved in -2-pyrrolidone, the mixture was mixed to prepare a positive electrode mixture paste. This positive electrode mixture paste was applied to one side of an aluminum foil (current collector), dried and pressurized, punched out to a predetermined size, and a positive electrode sheet was produced. The density of the portion excluding the current collector of the positive electrode was 3.6 g / cm ³ . Further, silicon (simple substance): 10% by mass, artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material); 80% by mass, acetylene black (conductive agent); Adhesive); 5% by mass was added to and mixed with the solution in which 1-methyl-2-pyrrolidone was dissolved to prepare a negative electrode mixture paste. This negative electrode mixture paste was applied to one side of a copper foil (current collector), dried and pressurized, punched out to a predetermined size, and a negative electrode sheet was produced. The density of the portion excluding the current collector of the negative electrode was 1.5 g / cm ³ . As a result of X-ray diffraction measurement using this electrode sheet, the ratio of the peak intensity I (110) of the (110) plane of the graphite crystal to the peak intensity I (004) of the (004) plane [I (110) / I (004)] was 0.1. And it laminated | stacked in order of the positive electrode sheet, the separator made from a microporous polyethylene film, and the negative electrode sheet, and added the non-aqueous electrolyte of the composition of Tables 1-3, and produced the 2032 type coin battery.

[Evaluation of low temperature characteristics after high temperature charge storage]
<Initial discharge capacity>
Using the coin battery produced by the above method, in a constant temperature bath at 25 ° C., charge at a constant current of 1 C and a constant voltage to a final voltage of 4.35 V for 3 hours, lower the temperature of the constant temperature bath to −10 ° C., The battery was discharged to a final voltage of 2.75 V under a constant current of 1 C, and an initial discharge capacity of −10 ° C. was obtained.
<High-temperature charge storage test>
Next, this coin battery was charged in a constant temperature bath at 65 ° C. with a constant current and a constant voltage of 1 C for 3 hours to a final voltage of 4.35 V, and stored for 7 days while being maintained at 4.35 V. Then, it put into the thermostat of 25 degreeC, and discharged once to the final voltage 2.75V under the constant current of 1C.
<Discharge capacity after storage at high temperature>
Thereafter, in the same manner as the measurement of the initial discharge capacity, the discharge capacity at −10 ° C. after storage at high temperature was obtained.
<Low temperature characteristics after high temperature charge storage>
The low temperature characteristic after high temperature charge storage was calculated | required from the following -10 degreeC discharge capacity maintenance factor.
0 ° C. discharge capacity retention rate after storage at high temperature (%) = (− 10 ° C. discharge capacity after high temperature storage / initial discharge capacity at −10 ° C.) × 100
The battery characteristics are shown in Tables 1-3.

Examples 24 to 25, Comparative Example 4
A positive electrode sheet was produced using LiNi _1/2 Mn _3/2 O ₄ (positive electrode active material) instead of the positive electrode active material used in Example 1. LiNi _1/2 Mn _3/2 O ₄ coated with amorphous carbon; 94% by mass, acetylene black (conductive agent); 3% by mass are mixed in advance and polyvinylidene fluoride (binder); 3% by mass Was added to a solution dissolved in 1-methyl-2-pyrrolidone and mixed to prepare a positive electrode mixture paste. This positive electrode mixture paste was applied to one side of an aluminum foil (current collector), dried, pressurized and cut into a predetermined size to produce a positive electrode sheet, and the end-of-charge voltage during battery evaluation Was made 4.9V, the end-of-discharge voltage was 2.7V, and the composition of the non-aqueous electrolyte was changed to a predetermined one, and a coin battery was prepared and evaluated as in Example 1. It was. The results are shown in Table 3.

Examples 26 to 27 and Comparative Example 5
In place of the negative electrode active material used in Example 1, a negative electrode sheet was prepared using lithium titanate Li ₄ Ti ₅ O ₁₂ (negative electrode active material). Lithium titanate Li ₄ Ti ₅ O ₁₂ ; 80% by mass, acetylene black (conductive agent); 15% by mass are mixed in advance, and polyvinylidene fluoride (binder); 5% by mass in 1-methyl-2-pyrrolidone A negative electrode mixture paste was prepared by adding to the dissolved solution and mixing. This negative electrode mixture paste was applied onto a copper foil (current collector), dried and pressurized, punched out to a predetermined size, and a negative electrode sheet was produced. A coin battery was fabricated and evaluated in the same manner as in Example 1 except that the discharge end voltage was 8 V, the discharge end voltage was 1.2 V, and the composition of the nonaqueous electrolyte was changed to a predetermined one. The results are shown in Table 5.

Examples 28-29
A lithium secondary battery was prepared in the same manner as in Comparative Example 1 except that a positive electrode prepared by adding a predetermined amount of the lithium carboxylate represented by the general formula (I) to 100% of the positive electrode active material was used. did.

Examples 30-31
A lithium secondary battery was produced in the same manner as in Comparative Example 1 except that the carboxylic acid lithium salt represented by the general formula (I) was not added to the positive electrode but was added to the negative electrode.

In any of the lithium secondary batteries of Examples 1 to 23, Comparative Example 1 in which the lithium carboxylate of the general formula (I) was not added in the nonaqueous electrolytic solution of the present invention, triethylphosphonoacetate was added. In comparison with the lithium secondary battery in Comparative Example 2 and Comparative Example 3 in which bis (trimethylsilyl) -2,2-difluorosulfonyl acetate is added, the electrochemical characteristics in a wide temperature range are remarkably improved. . From the above, it has been found that the effect of the present invention is a unique effect when the specific lithium salt of the present invention is contained in a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent.
In addition, from the comparison between Examples 24 to 25 and Comparative Example 4 and from the comparison between Examples 26 to 27 and Comparative Example 5, when nickel manganate lithium salt (LiNi _1/2 Mn _3/2 O ₄ ) was used for the positive electrode, Since the same effect is observed when lithium titanate is used for the negative electrode, it is clear that the effect is not dependent on the specific positive electrode or negative electrode.

  Moreover, it became clear from the comparison of Examples 28-31 and Comparative Example 1 that even when the carboxylic acid lithium salt represented by the general formula (I) is contained in a site other than the electrolytic solution, the effect is obtained.

  Furthermore, the non-aqueous electrolyte of the present invention also has an effect of improving the discharge characteristics in a wide temperature range of the lithium primary battery.

  If the non-aqueous electrolyte of the present invention is used, an electricity storage device having excellent electrochemical characteristics in a wide temperature range can be obtained. Especially when used as a non-aqueous electrolyte for electricity storage devices such as lithium secondary batteries mounted on hybrid electric vehicles, plug-in hybrid electric vehicles, battery electric vehicles, etc., the electricity storage devices are unlikely to deteriorate in electrochemical characteristics over a wide temperature range. Can be obtained.

Claims (3)

A non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, containing one or more carboxylic acid lithium salts represented by the following general formula (I):
(In the formula, L is a direct bond, methylene group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,1-diyl group, propane-1,3-diyl group, butane. -1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group , fluoromethylene group, difluoromethylene group, chlorofluoromethylene group, 2,2,2-trifluoroethane-1 , 1-diyl group, 1,1,2,2-tetrafluoroethane-1,2-diyl group, or 1-fluoropropane-1,1-diyl group , and X represents the following general formula (II) or ( III) any one of the substituents represented.
(Wherein R ¹ , R ² and R ³ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, or a carbon number) A 6-12 aryl group, a C1-C6 alkoxy group, a C2-C6 alkenyloxy group, a C3-C6 alkynyloxy group, or a C6-C12 aryloxy group is shown.
In the alkyl group, alkenyl group, alkynyl group, aryl group, alkoxy group, alkenyloxy group, alkynyloxy group, and aryloxy group, at least one hydrogen atom of each group may be substituted with a halogen atom. ) It is an electrical storage device provided with the nonaqueous electrolyte solution in which electrolyte salt was melt | dissolved in the positive electrode, the negative electrode, and the nonaqueous solvent, Comprising: The said nonaqueous electrolyte solution is the nonaqueous electrolyte solution of Claim 1. An electricity storage device. Carboxylic acid lithium salt represented by the following general formula (IV).
(In the formula, L ¹ represents a direct bond, a methylene group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,1-diyl group, a propane-1,3-diyl group, Butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, fluoromethylene group, difluoromethylene group, chlorofluoromethylene group, 2,2,2-trifluoroethane- 1,1-diyl group, 1,1,2,2-tetrafluoroethane-1,2-diyl group, or 1-fluoropropane-1,1-diyl group , and X ¹ represents the following general formula (V) Or any one of the substituents represented by (VI).)
(Wherein R ⁴ , R ⁵ and R ⁶ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, or a carbon number) A 6-12 aryl group, a C1-C6 alkoxy group, a C2-C6 alkenyloxy group, a C3-C6 alkynyloxy group, or a C6-C12 aryloxy group is shown.
In the alkyl group, alkenyl group, alkynyl group, aryl group, alkoxy group, alkenyloxy group, alkynyloxy group, and aryloxy group, at least one hydrogen atom of each group may be substituted with a halogen atom. )