JP5392261B2 - Nonaqueous electrolyte and lithium battery using the same - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte excellent in battery characteristics such as high-temperature storage characteristics when the battery is used at a high voltage, and a lithium battery using the same.

2. Description of the Related Art In recent years, lithium secondary batteries have been widely used as driving power sources for small electronic devices such as mobile phones and laptop computers, electric vehicles, and power storage sources.
The lithium secondary battery is mainly composed of a positive electrode and a negative electrode containing a material capable of inserting and extracting lithium, and a non-aqueous electrolyte containing a lithium salt. As the non-aqueous electrolyte, carbonates such as ethylene carbonate (EC) and propylene carbonate (PC) are used.
As a negative electrode of a lithium secondary battery, lithium metal, a metal compound capable of inserting and extracting lithium (metal simple substance, oxide, alloy with lithium, etc.) and a carbon material are known. In particular, non-aqueous electrolyte secondary batteries using carbon materials that can occlude and release lithium such as coke and graphite (artificial graphite, natural graphite) are widely put into practical use.
Since the above negative electrode materials store and release lithium and electrons at a low potential equivalent to that of lithium metal, many solvents have the possibility of undergoing reductive decomposition, particularly at high temperatures. Regardless of this, the solvent in the electrolyte solution is partially reduced and decomposed on the negative electrode, and the decomposition product is deposited on the surface of the negative electrode to increase the resistance, or gas is generated due to the decomposition of the solvent and the battery is swollen. As a result, the movement of lithium ions is hindered, and there is a problem that battery characteristics such as high-temperature storage characteristics are deteriorated.

On the other hand, materials capable of occluding and releasing lithium, such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFePO ₄ used as positive electrode materials, store and release lithium and electrons at a high voltage of 3.5 V or more based on lithium. In order to do so, many solvents have the potential to undergo oxidative degradation. In addition, regardless of the type of positive electrode material, the solvent in the electrolyte solution partially oxidizes and decomposes on the positive electrode, and the decomposed product is deposited on the surface of the positive electrode to increase the resistance. When the battery is swollen and generated, the movement of lithium ions is hindered, resulting in a problem that battery characteristics such as high-temperature storage characteristics are deteriorated.

In addition, as a lithium primary battery, for example, a lithium primary battery using manganese dioxide or graphite fluoride as a positive electrode and lithium metal as a negative electrode is known and widely used because of its high energy density, but it is stored for a long time. It is required to suppress an increase in internal resistance and improve long-term storage performance at high temperatures.
Furthermore, in recent years, as a new power source for electric vehicles or hybrid electric vehicles, from the viewpoint of output density, an electric double layer capacitor using activated carbon or the like as an electrode, a lithium ion secondary battery from the viewpoint of coexistence of energy density and output density The development of a storage device called a hybrid capacitor (asymmetrical capacitor that utilizes both the capacity of lithium storage and release and the electrical double layer capacitance), which combines the storage principle of the electric double layer capacitor with high temperature storage characteristics, etc. There is a need for improved battery performance.

  Patent Document 1 discloses a non-aqueous electrolyte using a non-aqueous electrolyte solution to which a cyanoethoxy compound such as methyl 2-cyanoethyl ester (2-cyanoethyl acetate), bis (2-cyanoethyl) carbonate, bis-2-cyanoethyl ether is added. A secondary battery is disclosed, and is disclosed to be excellent in low temperature characteristics and the like.

JP 2000-77096 A

  An object of the present invention is to provide a non-aqueous electrolyte excellent in battery characteristics such as high-temperature storage characteristics when the battery is used at a high voltage, and a lithium battery using the same.

The present inventors have examined in detail the performance of the above-described prior art non-aqueous electrolyte. As a result, it was found that the non-aqueous electrolyte disclosed in Patent Document 1 is not satisfactory with respect to a decrease in discharge voltage due to an increase in internal resistance of the battery after being stored at a high temperature in a charged state.
Accordingly, the inventors have conducted extensive research to solve the above problems, and by adding a specific amount of a specific nitrile compound to a non-aqueous electrolyte, a non-aqueous electrolyte excellent in battery characteristics such as high-temperature storage characteristics can be obtained. The inventors have found that the lithium battery can be obtained, and further have found that a lithium battery using the lithium battery can be obtained, thereby completing the present invention.

That is, the present invention provides the following (1) to (3).
(1) In a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, the nonaqueous electrolytic solution contains 0.01 to 5% by mass of a nitrile compound represented by the following general formula (I). A feature of non-aqueous electrolyte.
N≡C—R ¹ —X—R ² (I)
(In the formula, X represents —S (═O) ₂ — (sulfone structure), —O—S (═O) —O— (sulfite structure), or —O—C (═O) —C (= O) —O— (oxalate structure), R ¹ represents a linear or branched alkylene group having 1 to 4 carbon atoms, and R ² represents a linear or branched group having 2 to 5 carbon atoms in total. A cyanoalkyl group, a linear or branched 2-alkynyl group having 3 to 5 carbon atoms, or a linear or branched alkyl group having 1 to 6 carbon atoms.)
(2) In a lithium battery comprising a non-aqueous electrolyte in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a non-aqueous solvent, the nitrile compound represented by the general formula (I) is added to the non-aqueous electrolyte in an amount of 0.01 Lithium battery characterized by containing -5 mass%.

(3) The following general formula (II)
A nitrile compound represented by
N≡C—R ³ —X—R ⁴ (II)
(In the formula, X represents —O—S (═O) —O— (sulfite structure) or —O—C (═O) —C (═O) —O— (oxalate structure), and R ³ Represents a linear or branched alkylene group having 1 to 4 carbon atoms, and R ⁴ represents a linear or branched cyanoalkyl group having 2 to 5 carbon atoms in total, a linear or branched group having 3 to 5 carbon atoms. A branched 2-alkynyl group or a linear or branched alkyl group having 1 to 6 carbon atoms, provided that when X is —O—C (═O) —C (═O) —O—, R ⁴ represents a linear or branched 2-alkynyl group having 3 to 5 carbon atoms, or a linear or branched alkyl group having 1 to 6 carbon atoms.

  ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous electrolyte and lithium battery excellent in battery characteristics, such as a high temperature storage characteristic, can be provided.

[Non-aqueous electrolyte]
The nonaqueous electrolytic solution of the present invention contains 0.01 to 5% by mass of a specific nitrile compound with respect to the mass of the nonaqueous electrolytic solution in a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent. It is characterized by.

[Nitrile compound]
The nitrile compound contained in the nonaqueous electrolytic solution of the present invention is represented by the following general formula (I).
N≡C—R ¹ —X—R ² (I)
In the general formula (I), X represents —S (═O) ₂ — (sulfone structure), —O—S (═O) —O— (sulfite structure), or —O—C (═O) —. C (= O) -O- (oxalate structure) is shown.

R ¹ represents a linear or branched alkylene group having 1 to 4 carbon atoms. Specific examples thereof include methylene group, ethylene group, trimethylene group, tetramethylene group, ethylidene group (branch), propylidene group (branch), 1-methylethylene group (branch), 2-methylethylene group (branch). Branch) and alkylene groups such as 1-methylethylidene group. Among these, a linear or branched alkylene group having 2 to 4 carbon atoms is preferable, and an ethylene group and a 1-methylethylidene group are particularly preferable.
R ² is a linear or branched cyanoalkyl group having 2 to 5 carbon atoms, a linear or branched 2-alkynyl group having 3 to 5 carbon atoms, or a linear or branched group having 1 to 6 carbon atoms. An alkyl group is shown.
Specific examples of the straight-chain or branched cyanoalkyl group having 2 to 5 carbon atoms are cyanomethyl group, 2-cyanoethyl group, 3-cyanopropyl group, 4-cyanobutyl group, 1-cyanoethyl group, 2-cyano- Examples include 1-methylethyl group, 2-cyano-2-methylethyl group, 1,1-dimethylcyanomethyl group, and the like.
Specific examples of the straight or branched 2-alkynyl group having 3 to 5 carbon atoms include 2-propynyl group, 1-methyl-2-propynyl group, 1,1-dimethyl-2-propynyl group and the like. .
Specific examples of the linear or branched alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, and tert-butyl. Group, n-pentyl group, n-hexyl group and the like.

Among the R ² , from the viewpoint of the effect of improving battery characteristics such as high-temperature storage characteristics, the 2 cyanoalkyl groups such as 2-cyanoethyl group and 1,1-dimethylcyanomethyl group, and the 2 such as 2-propynyl group. -The alkyl group such as alkynyl group, methyl group and ethyl group is preferable, the cyanoalkyl group and the 2-alkynyl group are more preferable, 2-cyanoethyl group, 1,1-dimethylcyanomethyl group, 1,1-dimethyl. A cyanoethyl group and a 2-propynyl group are more preferable.

In the nitrile compound represented by the general formula (I), when (i) X is —S (═O) ₂ — (sulfone structure), (ii) X is —O—S (═O) —O—. Specific examples for the case of (sulfite structure) and (iii) the case where X is —R ¹ —O—C (═O) C (═O) —O—R ² — (oxalate structure) are as follows: It is.

(I) Specific examples when X is —S (═O) ₂ — (sulfone structure) include bis (cyanoalkyl) sulfones, cyanoalkyl-2-propynylsulfones, cyanoalkylsulfones, and the like. .
Examples of bis (cyanoalkyl) sulfones include bis (cyanomethyl) sulfone, bis (2-cyanoethyl) sulfone, bis (3-cyanopropyl) sulfone, bis (4-cyanobutyl) sulfone, bis (1-cyanoethyl) sulfone, bis (2-Cyano-1-methylethyl) sulfone, bis (2-cyano-2-methylethyl) sulfone and the like can be mentioned.
Cyanoalkyl-2-propynyl sulfones include cyanomethyl-2-propynyl sulfone, 2-cyanoethyl-2-propynyl sulfone, 3-cyanopropyl-2-propynyl sulfone, 4-cyanobutyl-2-propynyl sulfone, 1-cyanoethyl- Examples include 2-propynyl sulfone, 2-cyano-1-methylethyl-2-propynyl sulfone, and 2-cyano-2-methylethyl-2-propynyl sulfone.

Cyanoalkyl sulfones include cyanomethyl methyl sulfone, 2-cyanoethyl methyl sulfone, 3-cyanopropyl methyl sulfone, 4-cyanobutyl methyl sulfone, 1-cyanoethyl methyl sulfone, 2-cyano-1-methyl ethyl methyl sulfone, 2 -Cyano-2-methylethyl methyl sulfone, cyanomethyl ethyl sulfone, 2-cyanoethyl ethyl sulfone, 3-cyanopropyl ethyl sulfone, 4-cyanobutyl ethyl sulfone, 1-cyanoethyl ethyl sulfone, 2-cyano-1-methyl ethyl ethyl Examples include sulfone, 2-cyano-2-methylethylethylsulfone, 2-cyanoethyl-n-propylsulfone, and 2-cyanoethyl-n-butylsulfone.
Among these, bis (2-cyanoethyl) sulfone, 2-cyanoethyl-2-propynylsulfone, 2-cyanoethylmethylsulfone, and 2-cyanoethylethylsulfone are preferable, and bis (2-cyanoethyl) sulfone and 2-cyanoethyl-2 are preferred. -Propinyl sulfone is particularly preferred.

(Ii) Specific examples when X is —O—S (═O) —O— (sulfite structure) include bis (cyanoalkyl) sulfites, cyanoalkyl-2-propynylsulfites, and cyanoalkyl. And sulfites.
Bis (cyanoalkyl) sulfites include bis (cyanomethyl) sulfite, bis (2-cyanoethyl) sulfite, bis (3-cyanopropyl) sulfite, bis (4-cyanobutyl) sulfite, bis (1- Cyanoethyl) sulfite, bis (2-cyano-1,1-dimethylethyl) sulfite, bis (1,1-dimethylcyanomethyl) sulfite, and the like.
Examples of cyanoalkyl-2-propynyl sulfites include cyanomethyl-2-propynyl sulfite, 2-cyanoethyl-2-propynyl sulfite, 3-cyanopropyl-2-propynyl sulfite, and 4-cyanobutyl-2-propynyl sulfite. 1-cyanoethyl-2-propynyl sulfite, 2-cyano-1,1-dimethylethyl-2-propynyl sulfite, 1,1-dimethylcyanomethyl-2-propynyl sulfite, 2-cyanoethyl-1-methyl- Examples include 2-propynyl sulfite and 2-cyanoethyl-1,1-dimethyl-2-propynyl sulfite.

Cyanoalkyl sulfites include cyanomethyl methyl sulfite, 2-cyanoethyl methyl sulfite, 3-cyanopropyl methyl sulfite, 4-cyanobutyl methyl sulfite, 1-cyanoethyl methyl sulfite, 2-cyano-1, 1-dimethylethyl methyl sulfite, 1,1-dimethyl cyanomethyl methyl sulfite, cyanomethyl ethyl sulfite, 2-cyanoethyl ethyl sulfite, 3-cyanopropyl ethyl sulfite, 4-cyanobutyl ethyl sulfite, 1- Cyanoethyl ethyl sulfite, 2-cyano-1,1-dimethylethyl ethyl sulfite, 1,1-dimethyl cyanomethyl ethyl sulfite, 2-cyanoethyl-n-propyl sulfite, 2-cyanoethyl-n-butyl Le sulfite, and the like.
Among these, bis (2-cyanoethyl) sulfite, bis (1,1-dimethylcyanomethyl) sulfite, 2-cyanoethyl-2-propynyl sulfite, 1,1-dimethylcyanomethyl-2-propynyl sulfite 2-cyanoethyl methyl sulfite and 2-cyanoethyl ethyl sulfite are preferred, and bis (2-cyanoethyl) sulfite and 2-cyanoethyl 2-propynyl sulfite are particularly preferred.

(Iii) Specific examples when X is —R ¹ —O—C (═O) C (═O) —O—R ² — (oxalate structure) include bis (cyanoalkyl) oxalates, cyanoalkyl- Examples include 2-propynyl oxalates and cyanoalkyl oxalates.
Examples of the bis (cyanoalkyl) oxalates include bis (cyanomethyl) oxalate, bis (2-cyanoethyl) oxalate, bis (3-cyanopropyl) oxalate, bis (4-cyanobutyl) oxalate, bis (1-cyanoethyl) oxalate, bis (2-Cyano-1,1-dimethylethyl) oxalate, bis (1,1-dimethylcyanomethyl) oxalate and the like.
As cyanoalkyl-2-propynyl oxalates, cyanomethyl-2-propynyl oxalate, 2-cyanoethyl-2-propynyl oxalate, 3-cyanopropyl-2-propynyl oxalate, 4-cyanobutyl-2-propynyl oxalate 1-cyanoethyl-2-propynyl oxalate, 2-cyano-1,1-dimethylethyl-2-propynyl oxalate, 1,1-dimethylcyanomethyl-2-propynyl oxalate, 2-cyanoethyl-1-methyl- Examples include 2-propynyl oxalate and 2-cyanoethyl-1,1-dimethyl-2-propynyl oxalate.

Examples of cyanoalkyl oxalates include cyanomethyl methyl oxalate, 2-cyanoethyl methyl oxalate, 3-cyanopropyl methyl oxalate, 4-cyanobutyl methyl oxalate, 1-cyanoethyl methyl oxalate, 2-cyano-1, 1-dimethylethylmethyl oxalate, 1,1-dimethylcyanomethyl methyl oxalate, cyanomethyl ethyl oxalate, 2-cyanoethyl ethyl oxalate, 3-cyanopropyl ethyl oxalate, 4-cyanobutyl ethyl oxalate, 1- Cyanoethyl ethyl oxalate, 2-cyano-1,1-dimethylethyl ethyl oxalate, 1,1-dimethyl cyanomethyl ethyl oxalate, 2-cyanoethyl-n-propyl oxalate, 2-cyanoethyl-n-butyl Ruokisareto, and the like.
Among these, bis (2-cyanoethyl) oxalate, bis (1,1-dimethylcyanomethyl) oxalate, 2-cyanoethyl-2-propynyl oxalate, 1,1-dimethylcyanomethyl-2-propynyl oxalate, 2 -Cyanoethyl methyl oxalate and 2-cyanoethyl ethyl oxalate are preferable, and bis (2-cyanoethyl) oxalate and 2-cyanoethyl-2-propynyl oxalate are particularly preferable.

Among the nitrile compounds represented by the general formula (I), (i) when X is —S (═O) ₂ — (sulfone structure) from the viewpoint of improving battery characteristics such as high-temperature storage characteristics. And (ii) X is more preferably —O—S (═O) —O— (sulfite structure), and (ii) X is —O—S (═O) —O— (sulfite structure). Is more preferable.
The above nitrile compounds can be used alone or in combination of two or more.
The reason why the nitrile compound is highly effective in improving battery characteristics such as high-temperature storage characteristics is not necessarily clear, but is considered to be due to the following reasons.
The nitrile compound includes at least one highly polar cyanoalkyl group and (i) -S (= O) _2- (sulfone structure), (ii) -O-S (= O) -O- (sulfite structure). ), Or (iii) —O—C (═O) —C (═O) —O— (oxalate structure). These structures are electrochemical compared to —O—C (═O) — (ester structure), —O—C (═O) —O— (carbonate structure), or —O— (ether structure). Furthermore, when R ² contains a cyanoalkyl group or 2-propynyl group in the general formula (I), a particularly excellent dense film can be easily formed on the positive electrode and the negative electrode. It is estimated that. Thereby, it is considered that the decomposition of the nonaqueous electrolytic solution is suppressed and the lithium ions easily move in the coating.

[Content of nitrile compound]
In the nonaqueous electrolytic solution of the present invention, when the content of the nitrile compound represented by the general formula (I) contained in the nonaqueous electrolytic solution exceeds 5% by mass, a film is excessively formed on the electrode. Therefore, battery characteristics such as high-temperature storage characteristics may be deteriorated, and if the amount is less than 0.01% by mass, a film is not sufficiently formed. It may not be obtained. Therefore, the content of the nitrile compound is 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 0.5% by mass or more in the mass of the nonaqueous electrolytic solution. Moreover, the upper limit is 5 mass% or less, 3 mass% or less is preferable and 2 mass% or less is more preferable.
When two or more nitrile compounds are used in combination, the total amount is preferably in the above range.

  In the non-aqueous electrolyte of the present invention, the nitrile compound represented by the general formula (I) contained in the non-aqueous electrolyte improves battery characteristics such as high-temperature storage characteristics even when used alone, By combining a non-aqueous solvent, an electrolyte salt, and other additives described below, a unique effect of synergistically improving battery characteristics such as high-temperature storage characteristics is exhibited. The reason is not necessarily clear, but it is considered that a mixed film having high ion conductivity containing the nitrile compound and the non-aqueous solvent, electrolyte salt, and other additive constituent elements is formed. .

[Nonaqueous solvent]
Examples of the non-aqueous solvent used in the non-aqueous electrolyte of the present invention include cyclic carbonates, chain carbonates, chain esters, ethers, amides, phosphate esters, sulfones, lactones, S = O-containing compounds, cyclic peroxides, aromatic compounds and the like can be mentioned.
Cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), 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 the like. Among these, EC, PC, and a cyclic carbonate containing at least one selected from cyclic carbonates containing a double bond or fluorine are preferred, and EC and / or PC and a cyclic carbonate containing a double bond or fluorine are used. Use of one or more is more preferable because battery characteristics such as high-temperature storage characteristics are further improved, and it is particularly preferable that both EC and / or PC, a cyclic carbonate containing a double bond, and a cyclic carbonate containing fluorine are included. As the cyclic carbonate containing a double bond, VC and VEC are preferable, and as the cyclic carbonate containing fluorine, FEC and DFEC are preferable.

These solvents may be used alone, but when two or more types are used in combination, the effect of improving battery characteristics such as high-temperature storage characteristics is further improved, and combinations of three or more types are particularly preferred. preferable. Preferred combinations of these cyclic carbonates include EC and PC, EC and VC, EC and VEC, PC and VC, FEC and VC, FEC and EC, FEC and PC, FEC and DFEC, DFEC and EC, DFEC and PC DFEC and VC, DFEC and VEC, EC and PC and VC, EC and FEC and PC, EC and FEC and VC, EC and VC and VEC, FEC and PC and VC, DFEC and EC and VC, DFEC and PC and VC FEC, EC, PC, VC, DFEC, EC, PC, VC, and the like. Of the above combinations, more preferred are EC and VC, FEC and PC, DFEC and PC, EC and FEC and PC, EC and FEC and VC, EC and VC and VEC, and the like.
Although content in particular of cyclic carbonate is not restrict | limited, It is preferable to use in the range of 10-40 volume% of the total capacity | capacitance of a nonaqueous solvent. If the content is less than 10% by volume, the electrical conductivity of the electrolyte solution tends to decrease and the internal resistance of the battery tends to increase. If the content exceeds 40% by volume, battery characteristics such as high-temperature storage characteristics tend to decrease. is there.

Examples of chain carbonates include asymmetric chain carbonates such as methyl ethyl carbonate (MEC), methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, and ethyl propyl carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), and dipropyl. Symmetrical chain carbonates such as carbonate and dibutyl carbonate are exemplified. In particular, when an asymmetric chain carbonate is included, battery characteristics such as high-temperature storage characteristics tend to be improved, and it is more preferable to use an asymmetric chain carbonate and a symmetric chain carbonate in combination. Moreover, it is preferable that the ratio of the asymmetric linear carbonate contained in a linear carbonate is 50 volume% or more. As the asymmetric chain carbonate, those having a methyl group are preferable, and MEC is most preferable.
These chain carbonates may be used alone, but it is preferable to use a combination of two or more types because battery characteristics such as high-temperature storage characteristics and cycle characteristics are improved.
The content of the chain carbonate is not particularly limited, but it is preferably used in the range of 60 to 90% by volume of the total volume of the nonaqueous solvent. When the content is less than 60% by volume, the viscosity of the electrolytic solution increases, and when it exceeds 90% by volume, the electrical conductivity of the electrolytic solution decreases, and battery characteristics such as high-temperature storage characteristics tend to decrease. A range is preferable.
From the viewpoint of improving battery characteristics such as high-temperature storage characteristics, the ratio of cyclic carbonates to chain carbonates is preferably 10:90 to 40:60, and 15: 85-35: 65 is more preferable, and 20: 80-30: 70 is particularly preferable.

Examples of chain esters include methyl propionate, ethyl propionate, methyl acetate, ethyl acetate, methyl pivalate, butyl pivalate, hexyl pivalate, octyl pivalate, dimethyl oxalate, ethyl methyl oxalate, and oxalic acid. Examples include ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, cyclic ethers such as 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,2, and the like. -Chain ethers such as -diethoxyethane and 1,2-dibutoxyethane.
Examples of amides include dimethylformamide, examples of phosphate esters include trimethyl phosphate, tributyl phosphate, and trioctyl phosphate. Examples of sulfones include sulfolane, and examples of lactones. , Γ-butyrolactone, γ-valerolactone, α-angelica lactone and the like.
Examples of the compound containing S═O bond include sultone compounds such as 1,3-propane sultone, 1,3-butane sultone, 1,4-butane sultone, ethylene sulfite, hexahydrobenzo [1,3,2] dioxathiolane-2- Oxides (also called 1,2-cyclohexanediol cyclic sulfite), cyclic sulfite compounds such as 5-vinyl-hexahydro 1,3,2-benzodioxathiol-2-oxide, 1,4-butanediol dimethane Examples include sulfonate, disulfonic acid diester compounds such as 1,3-butanediol dimethanesulfonate, vinylsulfone compounds such as divinylsulfone, 1,2-bis (vinylsulfonyl) ethane, and bis (2-vinylsulfonylethyl) ether. .

Examples of cyclic peroxides include 7,8,15,16-tetraoxadispiro [5.2.5.2] hexadecane, 14,15-dioxa-7-azadispiro [5.1.5.2] pentadecane, and the like. Is mentioned.
Aromatic compounds include cyclohexyl benzene, fluorocyclohexyl benzene compounds (1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-4-cyclohexylbenzene), tert-butylbenzene, tert-amyl. Aromatic compounds having a branched alkyl group such as benzene, 1-fluoro-4-tert-butylbenzene, 1,3-di-tert-butylbenzene, biphenyl, terphenyl (o-, m-, p-form) ), Diphenyl ether, fluorobenzene, difluorobenzene (o-, m-, p-isomer), 2,4-difluoroanisole, partially hydrogenated terphenyl (1,2-dicyclohexylbenzene, 2-phenylbicyclohexyl, 1, 2-diphenylcyclohexa , Aromatic compounds o- cyclohexyl biphenyl), and the like.

  Among the above non-aqueous solvents, at least one selected from cyclic ethers, S═O bond-containing compounds, cyclic peroxides, and aromatic compounds having a branched alkyl group is represented by the general formula (I). In combination with a nitrile compound, it is preferable because battery characteristics such as high-temperature storage characteristics are improved. Particularly preferred is a cyclic radical such as 7,8,15,16-tetraoxadispiro [5.2.5.2] hexadecane, 14,15-dioxa-7-azadispiro [5.1.5.2] pentadecane. It is an oxide or a cyclic sulfite compound. If the amount of these compounds used in combination with the nitrile compound represented by the general formula (I) exceeds 5% by mass, the effect of improving the high-temperature storage characteristics in the charged state may not be obtained. If it is less than 0.05 mass%, the effect of improving battery characteristics such as high-temperature storage characteristics may not be sufficiently obtained. Accordingly, the content is preferably 0.05% by mass or more, and more preferably 0.5% by mass or more in the mass of the nonaqueous electrolytic solution. Moreover, the upper limit is preferably 5% by mass or less, and more preferably 3% by mass or less.

The above non-aqueous solvents are usually used as a mixture in order to achieve appropriate physical properties. As the combination, for example, a combination of a cyclic carbonate and a chain carbonate, a combination of a cyclic carbonate, a chain carbonate and a lactone, a combination of a cyclic carbonate, a chain carbonate and a chain ester, Examples include combinations of cyclic carbonates, chain carbonates, and ethers, combinations of cyclic carbonates, chain carbonates, and S═O bond-containing compounds.
Among these, it is preferable to use a nonaqueous solvent in which at least a cyclic carbonate and a chain carbonate are combined in order to improve the effect of improving battery characteristics such as high-temperature storage characteristics. More specifically, a combination of one or more cyclic carbonates selected from EC, PC, VC, and FEC and one or more chain carbonates selected from DMC, MEC, and DEC can be given.

[Electrolyte salt]
Examples of the electrolyte salt used in the present invention include lithium salts such as LiPF ₆ , LiBF ₄ , and LiClO ₄ , 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, and cyclic fluorides such as (CF ₂ ) ₂ (SO ₂ ) ₂ NLi, (CF ₂ ) ₃ (SO ₂ ) ₂ NLi And lithium salts containing an oxyalkylene chain, lithium salts having an oxalate complex such as lithium bis [oxalate-O, O ′] lithium borate and difluoro [oxalate-O, O ′] lithium borate as anions. Among these, particularly preferable electrolyte salts are LiPF ₆ , LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ C ₂ F ₅ ) ₂ , and most preferable electrolyte salts are LiPF ₆ , LiBF _4, and LiN. (SO ₂ CF ₃ ) ₂ . These electrolyte salts can be used singly or in combination of two or more.

A preferable combination of these electrolyte salts includes a combination including LiPF ₆ and further including at least one selected from LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ and LiN (SO ₂ C ₂ F ₅ ) _2. It is done. Preferably, a combination of LiPF ₆ and LiBF _4, a combination of LiPF ₆ and _{LiN (SO 2 CF 3) 2} , combinations and the like of LiPF ₆ and _{LiN (SO 2 C 2 F 5} ) 2.
When the molar ratio of (LiPF ₆ : LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ and electrolyte salt selected from LiN (SO ₂ C ₂ F ₅ ) ₂ ) is lower than 70:30, the ratio of LiPF ₆ is lower When the ratio of LiPF ₆ is higher than 99: 1, the high-temperature storage characteristics may be deteriorated. Accordingly, the molar ratio of (electrolyte salt selected from LiPF ₆ : LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ C ₂ F ₅ ) ₂ ) is in the range of 70:30 to 99: 1. The range of 80:20 to 98: 2 is more preferable. By using in a combination of the above ranges, the effect of improving battery characteristics such as high-temperature storage characteristics can be further improved.

The electrolyte salt can be mixed in any ratio, but other electrolytes except LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ and LiN (SO ₂ C ₂ F ₅ ) ₂ when used in combination with LiPF _6. If the ratio of the salt to the total electrolyte salt (molar fraction) is less than 0.01%, the effect of improving the high-temperature storage characteristics is poor, and if it exceeds 45%, the high-temperature storage characteristics may be deteriorated. Therefore, the ratio (molar fraction) is preferably 0.01 to 45%, more preferably 0.03 to 20%, still more preferably 0.05 to 10%, and most preferably 0.05 to 5%. is there.
The concentration used by dissolving all the electrolyte salts is usually preferably 0.3M or more, more preferably 0.5M or more, and most preferably 0.7M 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, further preferably 1.5M or less, and most preferably 1.2M or less.

  As the electrolyte for the electric double layer capacitor (capacitor), known quaternary ammonium salts such as tetraethylammonium tetrafluoroborate, triethylmethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, and the like can be used.

[Production of non-aqueous electrolyte]
The non-aqueous electrolyte of the present invention is prepared, for example, by mixing the non-aqueous solvent, adding the electrolyte salt thereto, and further adding a nitrile compound represented by the general formula (I) to the non-aqueous electrolyte. 0.01 to 5% by mass can be added and prepared.
At this time, it is preferable to use a nonaqueous solvent and a compound to be added to the electrolytic solution that are purified in advance and have as few impurities as possible within a range that does not significantly reduce productivity.
The battery characteristics can be improved by including, for example, carbon dioxide or air in the nonaqueous electrolytic solution of the present invention. In particular, from the viewpoint of improving charge / discharge characteristics at high temperatures, it is preferable to use a nonaqueous electrolytic solution in which carbon dioxide is dissolved. The dissolved amount of carbon dioxide is preferably 0.001% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.2% by mass or more, and saturates carbon dioxide with respect to the mass of the non-aqueous electrolyte. It is most preferable to dissolve it up to.
The nonaqueous electrolytic solution of the present invention can be suitably used as an electrolytic solution for a lithium primary battery and a lithium secondary battery. Furthermore, the nonaqueous electrolytic solution of the present invention can also be used as an electrolytic solution for electric double layer capacitors and an electrolytic solution for hybrid capacitors. Among these, the nonaqueous electrolytic solution of the present invention is most suitable for use in a lithium secondary battery.

〔Lithium battery〕
The lithium battery of the present invention is a generic term for a lithium primary battery and a lithium secondary battery, and is a lithium battery comprising a nonaqueous electrolyte solution in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a nonaqueous solvent. The nitrile compound represented by the formula (I) is contained in the nonaqueous electrolytic solution in an amount of 0.01 to 5% by mass. The content of the nitrile compound in the non-aqueous electrolyte is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass, and still more preferably 0.5 to 2% by mass.
In the lithium battery of the present invention, constituent members such as a positive electrode and a negative electrode other than the non-aqueous electrolyte can be used without particular limitation.
For example, as the positive electrode active material for a lithium secondary battery, a lithium composite metal oxide containing at least one 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 lithium composite metal oxides 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. Examples thereof include Mn _1/3 O ₂ , LiNi _1/2 Mn _3/2 O ₄ , LiCo _0.98 Mg _0.02 O _{2 and the} like. Further, LiCoO ₂ and LiMn ₂ O ₄ , LiCoO ₂ and LiNiO ₂ , LiMn ₂ O ₄ and LiNiO ₂ may be used in combination.

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, and nickel is replaced with one or more elements selected from Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, Cu, Bi, Mo, La, and the like. Or a part of O may be substituted with S or F, or a compound containing these other elements may 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 represents one or more elements selected from Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, Cu. 0.001 ≦ x ≦ 0.05 And lithium mixed metal oxides usable at 4.4 V or higher, such as LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ and LiNi _1/2 Mn _3/2 O ₄ . When a lithium composite metal oxide having a high charge voltage is used, battery characteristics such as high-temperature storage characteristics are likely to deteriorate due to a reaction with a non-aqueous electrolyte during charging. However, in the lithium secondary battery according to the present invention, these batteries are used. The deterioration of characteristics can be suppressed.

Furthermore, lithium-containing olivine-type phosphate can also be used as the positive electrode active material. In particular, a lithium-containing olivine-type phosphate containing at least one selected from Fe, Co, Ni, and Mn is preferable. Specific examples thereof include LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiMnPO _{4 and the} like.
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 can be substituted with one or more elements selected from these, or can 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.

  The conductive agent for the positive electrode is not particularly limited as long as it is an electron conductive material that does not cause chemical changes. Examples thereof include graphite such as natural graphite (flaky graphite and the like) and artificial graphite, and carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black. Further, graphites and carbon blacks 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, to further enhance the capacity of the battery, is preferably 2 g / cm ³ or more, more preferably 3 g / cm ³ or more More preferably, it is 3.6 g / cm ³ or more. The upper limit thereof, since there is a case where substantially produced exceeds 4.0 g / cm ³ is difficult, 4.0 g / cm ³ or less.

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 the like, oxides or chalcogen compounds of one or more metal elements, SO ₂ , SOCl _2, etc. Examples thereof include a sulfur compound and fluorocarbon (fluorinated graphite) represented by the general formula (CF _x ) _n . Among these, MnO ₂ , V ₂ O ₅ , graphite fluoride and the like are preferable.

Examples of negative electrode active materials for lithium secondary batteries include lithium metals and lithium alloys, carbon materials capable of occluding and releasing lithium (graphites such as artificial graphite and natural graphite), and metals capable of occluding and releasing lithium. A compound etc. can be used individually by 1 type or in combination of 2 or more types.
Among these, it is 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 ) spacing (d ₀₀₂ ) is 0.340 nm. It is particularly preferable to use a carbon material having a graphite type crystal structure of (nanometer) or less, particularly 0.335 to 0.337 nm. When a highly crystalline carbon material is used, it tends to react with the non-aqueous electrolyte during charging, and battery characteristics such as high-temperature storage characteristics and cycle characteristics tend to deteriorate. However, the lithium secondary battery according to the present invention has non-reactivity. Reaction with the water electrolyte can be suppressed. In addition, it is preferable that the highly crystalline carbon material is coated with the low crystalline carbon material because decomposition of the nonaqueous electrolytic solution is further suppressed.

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 particularly 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.
When graphite is used as the negative electrode active material, the density of the portion excluding the current collector of the negative electrode is usually 1.4 g / cm ³ or more, and preferably 1.6 g / cm ^{3 in} order to further increase the battery capacity. ³ or more, particularly preferably 1.7 g / cm ³ or more. Its upper limit, there is a case where substantially produced exceeds 2.0 g / cm ³ is difficult, 2.0 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 secondary battery is not particularly limited, and a coin battery, a cylindrical battery, a square battery, a laminate battery, or the like having a single-layer or multi-layer separator can be applied.
The battery separator is not particularly limited, and a single layer or laminated porous film of polyolefin such as polypropylene and polyethylene, a woven fabric, a nonwoven fabric, and the like can be used.
The lithium secondary battery of the present invention is excellent in battery characteristics such as high temperature storage characteristics even when the end-of-charge voltage is 4.2 V or higher, particularly 4.3 V or higher. It is good. 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 is used by 0.1-3C constant current discharge. Moreover, the lithium secondary battery in this invention can be charged / discharged at -40-100 degreeC, Preferably it is 0-80 degreeC.

  In the present invention, as a countermeasure against an increase in internal pressure of the lithium secondary battery, a method of providing a safety valve on the battery lid or incising 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.

[Nitrile compound]
The nitrile compound of the present invention is represented by the following general formula (II).
N≡C—R ³ —X—R ⁴ (II)
In the general formula (II), X represents —O—S (═O) —O— (sulfite structure) or —O—C (═O) —C (═O) —O— (oxalate structure). , R ³ represents a linear or branched alkylene group having 1 to 4 carbon atoms, R ⁴ represents a linear or branched cyanoalkyl group having 2 to 5 carbon atoms, or a straight chain having 3 to 5 carbon atoms. A chain or branched 2-alkynyl group, or a linear or branched alkyl group having 1 to 6 carbon atoms is shown.
That is, R ³ in the general formula (II) is the same as R ¹ in the general formula (I), and R ⁴ in the general formula (II) is the same as R ² in the general formula (I). However, when X is —O—C (═O) —C (═O) —O—, R ⁴ is a linear or branched 2-alkynyl group having 3 to 5 carbon atoms, or 1 to 1 carbon atoms. 6 linear or branched alkyl groups are shown.
Specific examples of the nitrile compound represented by the general formula (II) are omitted in order to avoid duplication, but among the compounds exemplified by the compound represented by the general formula (I), the general formula (II) All applicable compounds are mentioned.
There is no restriction | limiting in particular in the manufacturing method of the nitrile compound represented by general formula (II). For example, in the presence or absence of a solvent, in the presence of a base, after reacting a cyano alcohol having 1 to 5 carbon atoms with thionyl halide to obtain the nitrile compound, it is usually used for distillation, crystallization, column chromatography, etc. The purification method can be applied.

Hereinafter, although the synthesis example of a novel nitrile compound and the Example using the nonaqueous electrolyte of this invention are shown, this invention is not limited to these synthesis examples and Examples.
Synthesis Example 1 [Synthesis of bis (2-cyanoethyl) sulfite]
After dissolving 25.00 g (0.352 mol) of 2-cyanoethanol and 27.81 g (0.352 mol) of pyridine in 300 mL of toluene, 21.35 g (0.17 mol) of thionyl chloride was added dropwise at 5 ° C. over 20 minutes. The reaction was carried out with stirring at 25 ° C. for 2 hours. After the pyridine hydrochloride precipitated in the reaction solution was filtered off, the filtrate was concentrated and purified to obtain 25.5 g (80% yield) of transparent liquid bis (2-cyanoethyl) sulfite.
About the obtained bis (2-cyanoethyl) sulfite, ¹ H-NMR, ¹³ C-NMR (manufactured by JEOL Ltd., “AL300” used), IR (manufactured by Varian USA, “FTS7000E” used) and mass spectrometry (Mitsubishi Corporation make, "M80B" use) was measured and the structure was confirmed. The results are shown below.
(1) ¹ H-NMR (300 MHz, CDCl ₃ ): δ = 4.33-4.21 (m, 4H), 2.82-2.77 (m, 4H).
(2) ¹³ C-NMR (75 MHz, CDCl ₃ ): δ = 116.60, 57.21, 19.19.
(3) IR (liquid film method): 2972, 2945, 2256, 1414, 1206, 1022, 976, 868, 711 cm ^-1
(4) Mass spectrometry: MS (CI) M + 1 = 189.

Synthesis Example 2 [Synthesis of 2-cyanoethyl-2-propynyl sulfite]
11.69 g (0.166 mol) of 2-cyanoethanol, 9.22 g (0.166 mol) of propargyl alcohol and 33.29 g (0.329 mol) of triethylamine were dissolved in 400 mL of toluene, and 19.00 g (0.160 mol) of thionyl chloride was dissolved. Was added dropwise at 10 ° C. over 20 minutes, followed by reaction at 25 ° C. with stirring for 2 hours. After triethylamine hydrochloride precipitated in the reaction solution was filtered off, the filtrate was concentrated and purified to obtain 4.0 g (14% yield) of transparent liquid 2-cyanoethyl-2-propynyl sulfite.
About the obtained 2-cyanoethyl-2-propynyl sulfite, the measurement of < ¹ > H-NMR, < ¹³ > C-NMR and mass spectrometry was performed, and the structure was confirmed. The results are shown below.
(1) ¹ H-NMR (300 MHz, CDCl ₃ ): δ = 4.74 (dd, J = 15.9x2.4 Hz, 1 H), 4.61 (dd, J = 15.9x2.4 Hz, 1 H), 4.33 (td, J = 6.4x4.4 Hz, 1 H), 4.22 (td, J = 6.4x4.4 Hz, 1 H), 2.78 (t, J = 6.4Hz, 2 H), 2.62 (t, J = 2.4Hz, 1 H).
(2) ¹³ C-NMR (75 MHz, CDCl ₃ ): δ = 116.35, 76.99, 76.53, 56.50, 50.51, 19.10.
(3) Mass spectrometry: MS (CI) M + 1 = 174.

Synthesis Example 3 [Synthesis of 2-cyanoethyl-2-propynyl oxalate]
11.69 g (0.166 mol) of 2-cyanoethanol, 9.22 g (0.166 mol) of propargyl alcohol and 33.29 g (0.329 mol) of triethylamine were dissolved in 400 mL of toluene, and 20.27 g (0.160 mol) of oxalyl chloride. Was added dropwise at 10 ° C. over 20 minutes, followed by reaction at 25 ° C. with stirring for 2 hours. After triethylamine hydrochloride precipitated in the reaction solution was filtered off, the filtrate was concentrated and purified, and 3.8 g (13% yield) of white powdery 2-cyanoethyl-2-propynyl oxalate having a melting point of 51 ° C. Obtained.
About the obtained 2-cyanoethyl-2-propynyl oxalate, < ¹ > H-NMR, < ¹³ > C-NMR, and mass spectrometry were measured and the structure was confirmed. The results are shown below.
(1) ¹ H-NMR (300 MHz, CDCl ₃ ): δ = 4.90 (d, J = 2.4 Hz, 2 H), 4.52 (t, J = 6.4 Hz, 2 H), 2.86 (t, J = 6.4 Hz, 2 H), 2.61 (t, J = 2.4 Hz, 1 H).
(2) ¹³ C-NMR (75 MHz, CDCl ₃ ): δ = 156.34, 155.97, 115.98, 76.84, 75.64, 61.16, 54.49, 17.71.
(3) Mass spectrometry: MS (CI) M + 1 = 182.

Examples 1-12 and Comparative Examples 1-4
[Production of lithium ion secondary battery]
LiCoO ₂ (positive electrode active material); 93% by mass, acetylene black (conductive agent); 3% by mass are mixed, and polyvinylidene fluoride (binder); 4% by mass is dissolved in 1-methyl-2-pyrrolidone in advance. A positive electrode mixture paste was prepared by adding to and mixing with the previously prepared solution. This positive electrode mixture paste was applied to both surfaces of an aluminum foil (current collector), dried and pressurized, and cut into a predetermined size to produce a belt-like positive electrode sheet. The density of the portion excluding the current collector of the positive electrode was 3.6 g / cm ³ . Further, 95% by mass of artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material) coated with low crystalline carbon and 5% by mass of polyvinylidene fluoride (binder) are dissolved in 1-methyl-2-pyrrolidone in advance. The negative electrode mixture paste was prepared by adding to and mixing with the previously-prepared solution. This negative electrode mixture paste was applied to both surfaces of a copper foil (current collector), dried and pressurized, and cut into a predetermined size to produce a strip-shaped negative electrode sheet. The density of the portion excluding the current collector of the negative electrode was 1.7 g / cm ³ . And it laminated | stacked in order of the positive electrode sheet, the separator made from a microporous polyethylene film, the negative electrode sheet, and the separator, and wound this in the shape of a spiral. The wound body was housed in an iron cylindrical battery can plated with nickel which also serves as a negative electrode terminal. Further, a nonaqueous electrolyte prepared by adding a predetermined amount of the compounds shown in Table 1 was injected, and the battery lid having the positive electrode terminal was crimped through a gasket to produce a 18650 type cylindrical battery. The positive electrode terminal was previously connected inside the battery using a positive electrode sheet and an aluminum lead tab, and the negative electrode can was previously connected using a negative electrode sheet and a nickel lead tab.

The obtained battery was evaluated for high-temperature storage characteristics by the following method.
[Evaluation of high-temperature storage characteristics]
Using another cylindrical battery using a non-aqueous electrolyte having the same composition as described above, charging was performed for 3 hours at a constant current and a constant voltage of 1C in a thermostatic bath at 25 ° C to a final voltage of 4.3V, and then a constant constant of 1C. Under current, the battery was discharged to a final voltage of 3.0V. The average discharge voltage at the time of discharge was defined as “average discharge voltage before storage”.
Again, the battery was charged with a constant current and a constant voltage of 1 C to a final voltage of 4.3 V for 3 hours, placed in a constant temperature bath at 60 ° C. and stored at 4.3 V for 3 days. After that, put it in a constant temperature bath at 25 ° C., discharge it to a final voltage of 3.0 V under a constant current of 1 C, charge again to a final voltage of 4.3 V with a constant current of 1 C and a constant voltage for 3 hours, and then The battery was discharged to a final voltage of 3.0 V under a constant current. The average discharge voltage at the time of discharge was defined as “average discharge voltage after storage”.
Then, except that the nitrile compound represented by the general formula (I) was not added to the non-aqueous electrolyte, a cylindrical battery was prepared in the same manner as in the example and the battery characteristics were evaluated. Thus, the “average discharge voltage drop rate (%)” after high temperature storage was determined.
Average discharge voltage drop rate (relative value) (%) = (average discharge voltage before storage−average discharge voltage after storage) / (average discharge voltage before storage in Comparative Example 1−average discharge after storage in Comparative Example 1) Voltage) x 100
The production conditions and battery characteristics of the cylindrical battery are shown in Table 1.

The details of the electrolyte components in Table 1 are as follows.
(Cyclic carbonate)
EC: ethylene carbonate VC: vinylene carbonate FEC: 4-fluoro-1,3-dioxolan-2-one (chain carbonate)
MEC: Methyl ethyl carbonate DMC: Dimethyl carbonate

Example 13 and Comparative Example 5
The positive electrode active material LiCoO ₂ used in Example 2 and Comparative Example 1 was changed to LiFePO ₄ to produce a positive electrode sheet. LiFePO ₄ ; 90% by mass, acetylene black (conductive agent); 5% by mass were mixed, and a solution in which 5% by mass of polyvinylidene fluoride (binder) was previously dissolved in 1-methyl-2-pyrrolidone was mixed. In addition, the mixture was mixed to prepare a positive electrode mixture paste. This positive electrode mixture paste was applied onto an aluminum foil (current collector), dried, pressurized and cut into a predetermined size to produce a belt-like positive electrode sheet, a charge termination voltage of 3.6 V, Cylindrical batteries were produced in the same manner as in Example 2 and Comparative Example 1 except that the discharge end voltage was set to 2.0 V, and battery evaluation was performed. The results are shown in Table 2.

Example 14 and Comparative Example 6
The artificial graphite coated with the low crystalline carbon that is the negative electrode active material used in Example 2 and Comparative Example 1 was changed to Si to prepare a negative electrode sheet. Si: 80% by mass, acetylene black (conductive agent); 15% by mass are mixed and added to a solution in which 5% by mass is previously dissolved in 1-methyl-2-pyrrolidone. And mixed to prepare a negative electrode mixture paste. Except that this negative electrode mixture paste was applied onto a copper foil (current collector), dried and pressurized, cut into a predetermined size, and a strip-shaped negative electrode sheet was produced, Example 2 and A cylindrical battery was produced in the same manner as in Comparative Example 1, and the battery was evaluated. The results are shown in Table 3.

From Table 1, all the lithium secondary batteries of Examples 1 to 12 are of Comparative Example 1 (without adding a nitrile compound) and Comparative Examples 2 to 4 (with addition of a nitrile compound other than the nitrile compound of the present invention). It can be seen that the high-temperature storage characteristics are remarkably improved as compared with the lithium secondary battery.
From the comparison between Example 13 and Comparative Example 5 shown in Table 2, it can be seen that the same effect can be seen when lithium-containing olivine-type iron phosphate is used for the positive electrode.
Further, it can be seen from the comparison between Example 14 and Comparative Example 6 shown in Table 3 that the same effect can be seen when Si is used for the negative electrode.
Therefore, it is clear that the effect of the present invention is not an effect dependent on a specific positive electrode or negative electrode.
Furthermore, the non-aqueous electrolyte of the present invention also has an effect of improving the high temperature storage characteristics of the lithium primary battery.

  The lithium battery using the non-aqueous electrolyte of the present invention is extremely useful because it is excellent in battery characteristics such as high-temperature storage characteristics.

Claims (13)

A nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent is characterized by containing 0.01 to 5% by mass of a nitrile compound represented by the following general formula (I) in the nonaqueous electrolytic solution. Non-aqueous electrolyte.
N≡C—R ¹ —X—R ² (I)
(In the formula, X represents —S (═O) ₂ — (sulfone structure), —O—S (═O) —O— (sulfite structure), or —O—C (═O) —C (= O) —O— (oxalate structure), R ¹ represents a linear or branched alkylene group having 1 to 4 carbon atoms, and R ² represents a linear or branched group having 2 to 5 carbon atoms in total. A cyanoalkyl group, a linear or branched 2-alkynyl group having 3 to 5 carbon atoms, or a linear or branched alkyl group having 1 to 6 carbon atoms.) The nonaqueous electrolytic solution according to claim 1, wherein R ² in the general formula (I) is a 2-cyanoethyl group, a 1,1-dimethylcyanomethyl group, a 1,1-dimethylcyanoethyl group, or a 2-propynyl group.   The nitrile compound represented by the general formula (I) is bis (2-cyanoethyl) sulfone, 2-cyanoethyl-2-propynylsulfone, 2-cyanoethylmethylsulfone, or 2-cyanoethylethylsulfone. The non-aqueous electrolyte described.   The nitrile compound represented by the general formula (I) is bis (2-cyanoethyl) sulfite, bis (1,1-dimethylcyanomethyl) sulfite, 2-cyanoethyl-2-propynylsulfite, 1,1-dimethyl. The nonaqueous electrolytic solution according to claim 1 or 2, which is cyanomethyl-2-propynyl sulfite, 2-cyanoethyl methyl sulfite, or 2-cyanoethyl ethyl sulfite.   The nitrile compound represented by the general formula (I) is bis (2-cyanoethyl) oxalate, bis (1,1-dimethylcyanomethyl) oxalate, 2-cyanoethyl-2-propynyl oxalate, 1,1-dimethylcyanomethyl. The nonaqueous electrolytic solution according to claim 1 or 2, which is 2-propynyl oxalate, 2-cyanoethyl methyl oxalate, or 2-cyanoethyl ethyl oxalate. The nonaqueous electrolytic solution according to claim 1, wherein the electrolyte salt is at least one selected from LiPF ₆ , LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ C ₂ F ₅ ) ₂ . The electrolyte salt contains LiPF ₆ and the molar ratio of (LiPF ₆ : LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ and electrolyte salt selected from LiN (SO ₂ C ₂ F ₅ ) ₂ ) is 70:30. The nonaqueous electrolytic solution according to claim 6, which is in a range of ˜99: 1.   The nonaqueous electrolytic solution according to claim 1, wherein the nonaqueous solvent contains a cyclic carbonate and a chain carbonate.   The nonaqueous electrolytic solution according to claim 1, wherein the volume ratio of cyclic carbonates: chain carbonates is 10:90 to 40:60. In a lithium battery comprising a non-aqueous electrolyte in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a non-aqueous solvent, 0.01 to 5 mass of a nitrile compound represented by the following general formula (I) is contained in the non-aqueous electrolyte. % Lithium battery characterized by containing.
N≡C—R ¹ —X—R ² (I)
(In the formula, R ¹ , R ² and X are the same as above.)   The lithium battery according to claim 10, wherein the positive electrode includes a positive electrode active material containing one or more compounds selected from a lithium composite metal oxide and a lithium-containing olivine-type phosphate.   The negative electrode includes a negative electrode active material containing at least one compound selected from lithium metal, a lithium alloy, a carbon material capable of inserting and extracting lithium, and a metal compound capable of inserting and extracting lithium. 10. The lithium battery according to 10. Nitrile compounds represented by the following general formula (II).
N≡C—R ³ —X—R ⁴ (II)
(In the formula, X represents —O—S (═O) —O— (sulfite structure) or —O—C (═O) —C (═O) —O— (oxalate structure), and R ³ Represents a linear or branched alkylene group having 1 to 4 carbon atoms, and R ⁴ represents a linear or branched cyanoalkyl group having 2 to 5 carbon atoms in total, a linear or branched group having 3 to 5 carbon atoms. A branched 2-alkynyl group or a linear or branched alkyl group having 1 to 6 carbon atoms, provided that when X is —O—C (═O) —C (═O) —O—, R ⁴ represents a linear or branched 2-alkynyl group having 3 to 5 carbon atoms, or a linear or branched alkyl group having 1 to 6 carbon atoms.