JP7082613B2 - Non-aqueous electrolyte and storage device using it - Google Patents

Description

The present invention relates to a non-aqueous electrolytic solution capable of improving continuous charging characteristics in a high temperature and high voltage environment and a power storage device using the same.

In recent years, lithium ion secondary batteries and lithium ion capacitors have been attracting attention as power sources for automobiles such as electric vehicles and hybrid cars and power sources for idling stop.

As the electrolytic solution of the lithium secondary battery, electrolyte salts such as LiPF ₆ and LiBF ₄ were dissolved in cyclic carbonate such as ethylene carbonate and propylene carbonate and chain carbonate such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. A non-aqueous electrolyte solution is used.
In order to improve battery characteristics such as cycle characteristics and storage characteristics of such lithium secondary batteries, various studies have been made on non-aqueous solvents and electrolyte salts used in these non-aqueous electrolytic solutions.

For example, Patent Document 1 proposes a non-aqueous electrolytic solution containing an alkenyl group-containing chain ester such as allylmethyl carbonate in combination with an ionic liquid, which improves the safety of a power storage device and is used at room temperature. It is said that the battery characteristics can be improved.

By the way, when the lithium secondary battery is held in a continuous charging state for a long period of time in a high temperature and high voltage environment, the battery has a part of the non-aqueous solvent in the non-aqueous electrolyte solution on the surfaces of the positive electrode and the negative electrode. There is a problem that the non-aqueous electrolytic solution is consumed due to the deposition of decomposition products and the generation of gas due to oxidation or reduction decomposition, causing liquid withering. When the non-aqueous electrolytic solution withers, the interface resistance between the positive electrode and the negative electrode increases, and the desirable electrochemical characteristics of the battery decrease.
The electrolytic solution to which allylmethyl carbonate or methylcyclohexylcarbonate is added together with the ionic liquid proposed in Patent Document 1 has no effect on suppressing the decrease in discharge voltage after continuous charging for a long period of time in a high temperature and high voltage environment. The fact is that the above-mentioned inhibitory effect has not been sufficiently obtained without any description or suggestion.

Japanese Unexamined Patent Publication No. 2008-1238998

An object of the present invention is to provide a non-aqueous electrolytic solution capable of improving continuous charging characteristics in a high temperature and high voltage environment and a power storage device using the same.

As a result of examining the performance of the non-aqueous electrolytic solution of the prior art in detail, the present inventors evaluated by actually adding allylmethyl carbonate or methylcyclohexylcarbonate described in Patent Document 1 to the non-aqueous electrolytic solution. However, it was found that the continuous charging characteristics in a high temperature and high voltage environment were insufficient.
Therefore, the present inventors have conducted intensive 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, the following general formula (I) is used in the non-aqueous electrolytic solution. By using a non-aqueous electrolytic solution containing a specific amount of the specific compound represented and at least one selected from the group consisting of a fluorine atom-containing cyclic carbonate and an unsaturated bond-containing cyclic carbonate in a specific amount, the temperature and temperature are high. The present invention has been completed by finding that the continuous charging characteristics under a voltage environment are remarkably improved.

That is, the present invention provides the following (1) to (2).
(1) A non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolytic solution contains 0.1 to 4% by mass of the compound represented by the following general formula (I). A non-aqueous electrolytic solution for a power storage device, which comprises 0.1 to 30% by mass of at least one selected from the group consisting of a fluorine atom-containing cyclic carbonate and an unsaturated bond-containing cyclic carbonate as an additive.

(In the formula, R ¹ represents an alkyl group having 1 to 7 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms, and R ² to R ⁶ independently represent a hydrogen atom and an alkyl group having 1 to 4 carbon atoms. Or -CH ₂ OC (= O) OR ⁷ groups, R ⁷ indicates an alkyl group having 1 to 4 carbon atoms, and n = 0 or 1).
(2) A storage device including a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a non-aqueous solvent, wherein the non-aqueous electrolyte solution is the non-aqueous electrolyte solution according to (1). A power storage device characterized by that.

According to the present invention, it is possible to provide a non-aqueous electrolytic solution capable of improving continuous charging characteristics in a high temperature and high voltage environment, and a storage device such as a lithium battery using the non-aqueous electrolytic solution.

[Non-water electrolyte]
The non-aqueous electrolytic solution for a power storage device of the present invention is a non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a non-aqueous solvent, and a compound represented by the following general formula (I) is contained in the non-aqueous electrolytic solution. It contains 0.1 to 4% by mass, and is characterized by containing 0.1 to 30% by mass of at least one selected from the group consisting of a fluorine atom-containing cyclic carbonate and an unsaturated bond-containing cyclic carbonate as an additive. ..

(In the formula, R ¹ represents an alkyl group having 1 to 7 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms, and R ² to R ⁶ independently represent a hydrogen atom and an alkyl group having 1 to 4 carbon atoms. Or -CH ₂ OC (= O) OR ⁷ groups, R ⁷ indicates an alkyl group having 1 to 4 carbon atoms, and n = 0 or 1).

The reason why the non-aqueous electrolytic solution of the present invention can improve the continuous charging characteristics in a high temperature and high voltage environment is not always clear, but it is considered as follows.
Since the compound represented by the general formula (I) used in the present invention has a cyclohexyl group, the decomposition reaction on the electrode active surface is promoted and a film is formed quickly, but the heat of the film alone is used. The stability was inadequate. Therefore, when a specific amount of the compound represented by the general formula (I) and at least one selected from the group consisting of a fluorine atom-containing cyclic carbonate and an unsaturated bond-containing cyclic carbonate are used as an additive in a specific amount in combination. , "Cyclohexyl group", "-OC (= O) -O- group", "Fluorine atom-containing cyclic carbonate or unsaturated bond-containing cyclic carbonate" contains at least three characteristic groups and has high thermal stability. It is considered to form a mixed film.
Here, when one of the carbonates contains a phenyl group instead of a cyclohexyl group, sufficient strength cannot be obtained probably because the formation rate of the obtained film is slow or the constituent components are different. Further, in the present invention, since the film is composed of a compound in which the other substituent ^R1 of the carbonate represented by the general formula (I) is an alkyl group or a cycloalkyl group, an appropriate degree that does not hinder the permeation of lithium ions. It is considered that a film having a high degree of flexibility is formed and further decomposition of the solvent is suppressed, and as a result, the continuous charging characteristics in a high temperature and high voltage environment are further improved.

The compound contained in the non-aqueous electrolytic solution of the present invention is represented by the following general formula (I).

In the general formula (I), R ¹ represents an alkyl group having 1 to 7 carbon atoms or a cycloalkyl group, and among them, an alkyl group having 1 to 4 carbon atoms or a cycloalkyl group having 4 to 6 carbon atoms is preferable. Alkyl groups of 1 to 2 or cycloalkyl groups having 5 to 6 carbon atoms are preferable.

In the alkyl group having 1 to 7 carbon atoms or the cycloalkyl group having 3 to 6 carbon atoms represented by R ¹ , specific examples of the alkyl group include methyl group, ethyl group, n-propyl group, n-butyl and the like. A linear alkyl group of the above, or a branched alkyl group such as an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl, a cyclohexylmethyl group, etc. is preferably mentioned, and specific examples of the cycloalkyl group include a cyclopropyl group. , Cyclobutyl group, cyclopentyl group, cyclic alkyl group such as cyclohexyl group is preferable. Among these, a methyl group, an ethyl group, an n-propyl group or a cyclohexyl group is preferable, and a methyl group, an ethyl group or a cyclohexyl group is more preferable.

In the general formula (I), the R ² to R ⁶ independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an -CH ₂ OC (= O) OR ⁷ group, and represent a hydrogen atom or carbon. An alkyl group having a number of 1 to 4 is preferable, a hydrogen atom or an alkyl group having 1 to 2 carbon atoms is more preferable, and a hydrogen atom is further preferable.

Specific examples of the case where R ² to R ⁶ are alkyl groups having 1 to 4 carbon atoms include linear alkyl groups such as methyl group, ethyl group, n-propyl group and n-butyl group, and isopropyl group. Preferred examples thereof include branched alkyl groups such as an isobutyl group, a sec-butyl group, a hydrogen atom and a tert-butyl group. Among these, a methyl group, an ethyl group, or an n-propyl group is preferable, and a methyl group or an ethyl group is more preferable.

When R ² to R ⁶ are −CH ₂ OC (= O) OR ⁷ groups, R ⁷ represents an alkyl group having 1 to 4 carbon atoms, and an alkyl group having 1 to 2 carbon atoms is preferable.
^R4 is preferable as the substitution position of the −CH ₂ OC (= O) OR ⁷ group.

As a specific example of ^R7 , when it is an alkyl group having 1 to 4 carbon atoms, a linear alkyl group such as a methyl group, an ethyl group, an n-propyl group or an n-butyl group, or isopropyl. Preferred examples thereof include branched alkyl groups such as a group, an isobutyl group, a sec-butyl group and a tert-butyl group. Among these, a methyl group, an ethyl group, or an n-propyl group is preferable, and a methyl group or an ethyl group is more preferable.

In the general formula (I), n represents 0 or 1, and n is preferably 1 from the viewpoint of enhancing the effect of continuous charging characteristics in a high temperature and high voltage environment.
In the general formula (I), the following compounds are mentioned as a preferable example when n is 0 or 1.

[When n = 0]

Among the above compounds, methylcyclohexyl carbonate (Compound A1), methyl (2-methylcyclohexyl) carbonate (Compound A2), methyl (3-methylcyclohexyl) carbonate (Compound A3), methyl (4-methylcyclohexyl) carbonate (Compound A4). ), Methyl (2,3-dimethylcyclohexyl) carbonate (Compound A5), Methyl (2,4-dimethylcyclohexyl) carbonate (Compound A6), Methyl (2,5-dimethylcyclohexyl) carbonate (Compound A7), Methyl (2) , 6-dimethylcyclohexyl) carbonate (Compound A8), ethylcyclohexyl carbonate (Compound A14), ethyl (2-methylcyclohexyl) carbonate (Compound A15), ethyl (3-methylcyclohexyl) carbonate (Compound A16), ethyl (4- One or more selected from the group consisting of methylcyclohexyl carbonate (Compound A17) and dicyclohexylcarbonate (Compound A18) is preferable, and methylcyclohexylcarbonate (Compound A1), methyl (2-methylcyclohexyl) carbonate (Compound A2), and methyl. (3-Methylcyclohexyl) carbonate (Compound A3), methyl (4-methylcyclohexyl) carbonate (Compound A4), ethylcyclohexyl carbonate (Compound 14), ethyl (2-methylcyclohexyl) carbonate (Compound A15), ethyl (3-) One or more selected from the group consisting of methylcyclohexyl carbonate (Compound A16), ethyl (4-methylcyclohexyl) carbonate (Compound A17), and dicyclohexylcarbonate (Compound A18) is more preferable, and Methylcyclohexylcarbonate (Compound A1), More preferably, one or more selected from the group consisting of ethylcyclohexyl carbonate (Compound A14) and dicyclohexyl carbonate (Compound A18).

[When n = 1]

Among the above compounds, cyclohexylmethylmethyl carbonate (compound B1), cyclohexylmethylethylcarbonate (compound B3), bis (cyclohexylmethyl) carbonate (compound B5), cyclohexane-1,4-diylbis (methylene) dimethylbis (carbonate) ( One or more selected from the group consisting of compound B6) and cyclohexane-1,4-diylbis (methylene) diethylbis (carbonate) (compound B7) is preferable, and cyclohexylmethylmethylcarbonate (compound B1) and cyclohexylmethylethylcarbonate (compound B1) are preferable. More preferably, one or more selected from the group consisting of B3) and cyclohexane-1,4-diylbis (methylene) dimethylbis (carbonate) (Compound B6).

In the non-aqueous electrolytic solution of the present invention, the content of the compound represented by the general formula (I) is preferably 0.1 to 4% by mass in the non-aqueous electrolytic solution. If the content is 4% by mass or less, there is little possibility that an excessive film is formed on the electrode and the electrochemical properties are deteriorated, and if it is 0.1% by mass or more, the film is sufficiently formed and the temperature is high. Moreover, the effect of continuous charging characteristics in a high voltage environment is enhanced. The content is more preferably 0.3% by mass or more, and particularly preferably 0.6% by mass or more. Further, the upper limit thereof is more preferably 3% by mass or less, further preferably 2.2% by mass or less, and particularly preferably 1.7% by mass or less.

The non-aqueous electrolytic solution of the present invention contains at least one selected from the group consisting of a fluorine atom-containing cyclic carbonate and an unsaturated bond-containing cyclic carbonate as an additive to be used in combination with the compound represented by the general formula (I). do. Of these, a fluorine atom-containing cyclic carbonate is more preferable.

Fluorine atom-containing cyclic carbonates include 4-fluoro-1,3-dioxolane-2-one (FEC), trans or cis-4,5-difluoro-1,3-dioxolane-2-one (hereinafter, both are collectively referred to). Then, one kind or two or more kinds selected from the group consisting of (referred to as "DFEC") and the like can be mentioned, and 4-fluoro-1,3-dioxolane-2-one is more preferable.

Examples of the unsaturated bond-containing cyclic carbonate include carbon-carbon double bonds such as vinylene carbonate (VC), vinylethylene carbonate (VEC), 4-ethynyl-1,3-dioxolan-2-one (EEC), and carbon-. One or more selected from the group consisting of cyclic carbonates having carbon triple bonds can be mentioned, with vinylene carbonate and 4-ethynyl-1,3-dioxolan-2-one (EEC) being more preferred.

When the compounds selected from the group consisting of the fluorine atom-containing cyclic carbonate and the unsaturated bond-containing cyclic carbonate are used in combination, the effect of improving the continuous charging characteristics in a high temperature and high voltage environment is synergistically improved. preferable. Suitable combinations selected from the group consisting of these fluorine atom-containing cyclic carbonates and unsaturated bond-containing cyclic carbonates include a combination of VC and FEC, a combination of FEC and DFEC, a combination of VC and DFEC, a combination of VEC and DFEC, and VC. A combination of EEC and EEC, a combination of EC and EEC, and the like are preferable. Among the above combinations, a combination of VC and FEC, a combination of VC and DFEC, a combination of VEC and DFEC, and the like are more preferable.

The total content of at least one selected from the group consisting of the fluorine atom-containing cyclic carbonate and the unsaturated bond-containing cyclic carbonate is preferably 0.1 to 30% by mass in the non-aqueous electrolytic solution. If the content is 30% by mass or less, there is little possibility that an excessive film is formed on the electrode and the electrochemical properties are deteriorated, and if it is 0.1% by mass or more, the film is sufficiently formed and the temperature is high. Moreover, the effect of continuous charging characteristics in a high voltage environment is enhanced.
The content is preferably 0.5% by mass or more, more preferably 1% by mass or more in the non-aqueous electrolytic solution. The upper limit thereof is preferably 25% by mass or less, more preferably 15% by mass or less, further preferably 10% by mass or less, further preferably 6% by mass or less, and particularly preferably 4% by mass or less.

The content ratio (mass ratio) of at least one compound selected from the group consisting of the compound represented by the general formula (I) and the fluorine atom-containing cyclic carbonate and the unsaturated bond-containing cyclic carbonate is the general formula (I). When the content of the compound represented by is A mass% and the content of at least one compound selected from the group consisting of the fluorine atom-containing cyclic carbonate and the unsaturated bond-containing cyclic carbonate is B mass%, A / B is preferably in the range of 0.01 to 3. If the content ratio is 3 or less, there is little possibility that an excessive film is formed on the electrode and the electrochemical characteristics are deteriorated, and if it is 0.01 or more, the film is sufficiently formed, and the temperature and voltage are high. The effect of continuous charging characteristics in the environment is enhanced. The content ratio is preferably 0.01 or more, more preferably 0.05 or more, still more preferably 0.2 or more. Further, the upper limit thereof is preferably 3 or less, more preferably 1.8 or less, and more preferably 0.6 or less because the continuous charging characteristics in a high temperature and high voltage environment are further enhanced.

[Non-aqueous solvent]
The non-aqueous solvent used in the non-aqueous electrolytic solution of the present invention includes a cyclic carbonate (however, the non-aqueous solvent excludes a fluorine atom-containing cyclic carbonate and an unsaturated bond-containing cyclic carbonate; the same shall apply hereinafter) and a chain. One or more selected from the group consisting of esters, lactones, ethers, and amides are preferably used. It is most preferred that both cyclic carbonates and chain esters are included in order to synergistically improve continuous charging characteristics in high temperature and high voltage environments.
The term "chain ester" is used as a concept including a chain carbonate and a chain carboxylic acid ester.

(Cyclic carbonate)
Examples of the cyclic carbonate include one or more selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, and 2,3-butylene carbonate. One or two selected from the group consisting of propylene carbonate is more preferable.

(Chain ester)
The chain ester is one or more asymmetric chains selected from the group consisting of methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, and ethyl propyl carbonate. One or more symmetric chain carbonates selected from the group consisting of ester carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, and dibutyl carbonate, methyl pivalate, ethyl pivalate, pivalic acid. From pivalic acid esters such as propyl, methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), and butyl acetate One or more chain carboxylic acid esters selected from the above group are preferably mentioned.

Among the chain esters, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, propyl acetate (PA), butyl acetate, methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), and pivalic acid A chain ester having a molecular weight of 90 or more and 120 or less selected from the group consisting of methyl is preferable.

When chain carbonate is used as the chain ester, it is preferable to use two or more kinds. Further, it is more preferable that both the symmetric chain carbonate and the asymmetric chain carbonate are contained, and it is further preferable that the content of the symmetric chain carbonate is higher than that of the asymmetric chain carbonate.

The volume ratio of the symmetrical chain carbonate to the chain carbonate is preferably 51% by volume or more, more preferably 55% by volume or more. The upper limit is preferably 95% by volume or less, more preferably 85% by volume or less. It is particularly preferable that the symmetric chain carbonate contains dimethyl carbonate. Further, the asymmetric chain carbonate is more preferably having a methyl group, and methyl ethyl carbonate is particularly preferable. In the above case, the continuous charging characteristics in a high temperature and high voltage environment are further improved, which is preferable.

Further, it is more preferable that the chain ester contains at least one selected from the group consisting of propyl acetate, butyl acetate, methyl propionate, ethyl propionate (EP), propyl propionate (PP), and methyl pivalate. When a chain carboxylic acid ester is used, the ratio of the chain ester to the total volume is preferably 1 to 100% by volume. In the above case, the continuous charging characteristics under the highest temperature and high voltage environment are improved, which is preferable. The content is more preferably 7% by volume or more, more preferably 57% by volume or more, and particularly preferably using only the chain carboxylic acid ester with respect to the entire chain ester.

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 non-aqueous solvent. If the content is 60% by volume or more, the viscosity of the non-aqueous electrolytic solution does not become too high, and if it is 90% by volume or less, the electrical conductivity of the non-aqueous electrolytic solution may decrease and the electrochemical characteristics may decrease. Since it is small, it is preferably in the above range.
The ratio of the cyclic carbonate to the chain ester is preferably 10:90 to 45:55, preferably 15:85 to 45:55, from the viewpoint of continuous charging characteristics in a high temperature and high voltage environment. 40:60 is more preferable, and 20:80 to 35:65 is even more preferable.

(Other non-aqueous solvents)
In the non-aqueous electrolytic solution of the present invention, other non-aqueous solvents other than the above can be used.
Other non-aqueous solvents include cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran and 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyetane and the like. One or more selected from the group consisting of chain ethers, amides such as dimethylformamide, sulfolanes and the like, and lactones such as γ-butyrolactone (GBL) or γ-valerolactone and α-angelica lactone are preferable. Listed in.

The other non-aqueous solvents mentioned above are usually mixed and used in order to achieve appropriate physical characteristics. The combination preferably includes, for example, a combination of a cyclic carbonate, a chain ester and a lactone, a combination of a cyclic carbonate, a chain ester and an ether, and the like, and a combination of a cyclic carbonate, a chain ester and a lactone is more preferable. Among the lactones, it is more preferable to use γ-butyrolactone (GBL).
The content of the other non-aqueous solvent is usually 1% or more, preferably 2% or more, and usually 40% or less, preferably 30% or less, more preferably 20%, based on the total volume of the non-aqueous solvent. It is as follows.

(Other additives)
In the present invention, it is preferable to add other additives to the non-aqueous electrolytic solution for the purpose of further improving the continuous charging characteristics in a high temperature and high voltage environment.
Specific examples of other additives preferably include the following compounds (A) to (H).

(A) Succinonitrile, glutaronitrile, adipoynitrile, 1,3,5-hexanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3 A polyvalent nitrile compound having two or more carbon chains between CN groups such as 5-pentanetricarbonitrile, pimeronitrile, suberonitrile, and sebaconitrile.

(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, turphenyl (o-, m-, p-form), diphenyl ether, fluorobenzene, difluorobenzene (o-, m). -, P-form), anisole, 2,4-difluoroanisole, partial hydride of terphenyl (1,2-dicyclohexylbenzene, 2-phenylbicyclohexyl, 1,2-diphenylcyclohexane, o-cyclohexylbiphenyl), etc. Aromatic compound.

(C) Consists of methyl isocyanate, ethyl isocyanate, butyl isocyanate, phenylisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 1,4-phenylenedi isocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate. One or more isocyanate compounds selected from the group.

(D) 2-Propinyl Methyl Carbonate, 2-Propinyl Acetate, 2-Propinyl Formic Acid, 2-Propinyl Methacrylate, 2-Propinyl Methanesulfonic Acid, 2-Propinyl Vinyl Sulfonate, 2- (Methanesulfonyloxy) Propionic Acid 2- Propinyl, Di (2-Propinyl) Ogizalate, Methyl 2-Propinyl Ogizalate, Ethyl 2-Propinyl Ogizalate, Di (2-Propinyl) Glutarate, 2-Butin-1,4-diyl Dimethanesulfonate, 2- One or more triple bond-containing compounds selected from the group consisting of butin-1,4-diyldiformate and 2,4-hexadiyne-1,6-diyldimethanesulfonate.

(E) 1,3-Propane sultone, 1,3-butane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-propensultone, 2,2-dioxide-1,2-oxathiolan-4-yl Sulfones such as acetate and 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, ethylene sulphite, hexahydrobenzo [1,3,2] dioxathiolane-2-oxide (1,2) -Cyclohexanediol (also referred to as cyclic sulphite), and cyclic sulphite such as 5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide, cyclic sultone, butane-2,3-diyldimethane. Sulfone, butane-1,4-diyldimethanesulfonate, or sulfonic acid ester such as methylenemethanedisulfonate, divinylsulfone, 1,2-bis (vinylsulfonyl) ethane, bis (2-vinylsulfonylethyl) ether and the like. A non-lithium compound containing one or more S = O groups selected from the group consisting of vinyl sulfone compounds.

(F) 1,3-dioxolane, 1,3-dioxane, 5,5-dimethyl-1,3-dioxane, 5-ethyl-5-methyl-1,3-dioxane, 1,3,5-trioxane and the like. Cyclic acetal compound.

(G) trimethyl phosphate, tributyl phosphate, trioctyl phosphate, tris phosphate (2,2,2-trifluoroethyl), bis (2,2,2-trifluoroethyl) methyl phosphate, bis phosphate (2,2,2-trifluoroethyl) ethyl, bis phosphate (2,2,2-trifluoroethyl) 2,2-difluoroethyl, bis phosphate (2,2,2-trifluoroethyl) 2, 2,3,3-Tetrafluoropropyl, bis phosphate (2,2-difluoroethyl) 2,2,2-trifluoroethyl, bis phosphate (2,2,3,3-tetrafluoropropyl) 2,2 , 2-Trifluoroethyl and Phosphate (2,2,2-Trifluoroethyl) (2,2,3,3-Tetrafluoropropyl) Methyl, Tris Phosphate (1,1,1,3,3,3) -Hexafluoropropane-2-yl), methyl methylenebisphosphonate, ethyl methylenebisphosphonate, methyl ethylenebisphosphonate, ethyl ethylenebisphosphonate, methyl butylenebisphosphonate, ethyl butylenebisphosphonate, 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-propynyl One or more phosphorus-containing compounds selected from the group consisting of 2- (diethoxyphosphoryl) acetate, methyl pyrophosphate, and ethyl pyrophosphate.

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

(A) Among the polyvalent nitrile compounds, one or more selected from the group consisting of adiponitrile, pimeronitrile, suberonitrile, and sevaconitrile having a carbon chain of 4 or more between the -CN group and the -CN group is more preferable.

(B) Among aromatic compounds, one selected from the group consisting of biphenyl, terphenyl (o-, m-, p-form), fluorobenzene, cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene. Alternatively, two or more are more preferable, and one or two or more selected from the group consisting of biphenyl, o-terphenyl, fluorobenzene, cyclohexylbenzene, and tert-amylbenzene are particularly preferable.

Among the isocyanate compounds (C), one or more selected from the group consisting of hexamethylene diisocyanate, octamethylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate is more preferable.

(D) Examples of the triple bond-containing compound include 2-propynyl-methyl carbonate, -2-propynyl methacrylate, -2-propinyl methanesulfonic acid, -2-propynyl vinylsulfonic acid, and 2- (methanesulfonyloxy) propionic acid-. Selected from the group consisting of 2-propynyl, di (2-propynyl) oxalate, methyl-2-propynyl oxalate, ethyl-2-propynyl oxalate, and 2-butin-1,4-diyl-dimethanesulfonate. One or more are preferred, methanesulphonic acid-2-propynyl, vinylsulfonic acid-2-propynyl, 2- (methanesulfonyloxy) propionic acid-2-propynyl, di (2-propynyl) oxalate, and 2-. One or more selected from the group consisting of butin-1,4-diyldimethanesulfonate is more preferable.

(E) A non-lithium compound containing a cyclic or chain S = O group selected from the group consisting of sultone, cyclic sulphite, cyclic sulphate, sulfonic acid ester, and vinyl sulfone (provided that the triple bond-containing compound and the above general are used. It is preferable to use (does not include a specific compound represented by any of the formulas).

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, and 2,2-dioxide-. 1,2-oxathiolan-4-yl-acetate, 5,5-dimethyl-1,2-oxathiolan-4-one-2,2-dioxide, methylenemethanedisulfonate, ethylenesultone, ethylenesulfate, and 4-( One or more selected from the group consisting of methylsulfonylmethyl) -1,3,2-dioxathiolane-2-oxide is preferably used.

Examples of the chain S = O group-containing compound include butane-2,3-diyl-dimethanesulfonate, butane-1,4-diyl-dimethanesulfonate, dimethylmethanedisulfonate, pentafluorophenylmethanesulfonate, and divinyl. One or more selected from the group consisting of sulfone and bis (2-vinylsulfonylethyl) ether are preferably mentioned.
Among the cyclic or chain S = O group-containing compounds, 1,3-propanesultone, 1,4-butanesultone, 2,4-butanesultone, 2,2-dioxide-1,2-oxathiolane-4-yl- One or more selected from the group consisting of acetate, ethylene sulfate, pentafluorophenylmethane sulfonate, and divinyl sulfone are more preferable.

As the cyclic acetal compound (F), 1,3-dioxolane, 5,5-dimethyl-1,3-dioxane, and 5-ethyl-5-methyl-1,3-dioxane are preferable, and 1,3-dioxane and 5,5-Dimethyl-1,3-dioxane is more preferred.

(G) Phosphorus-containing compounds include tris phosphate (2,2,2-trifluoroethyl), tris phosphate (1,1,1,3,3,3-hexafluoropropane-2-yl), and methyl. -2- (Dimethylphosphoryl) acetate, ethyl-2- (dimethylphosphoryl) acetate, methyl-2- (diethylphosphoryl) acetate, ethyl-2- (diethylphosphoryl) acetate, 2-propynyl-2- (dimethylphosphoryl) acetate , 2-Propinyl-2- (diethylphosphoryl) acetate, methyl-2- (dimethoxyphosphoryl) acetate, ethyl-2- (dimethoxyphosphoryl) acetate, methyl-2- (diethoxyphosphoryl) acetate, ethyl-2- (diethoxyphosphoryl) acetate Ethethoxyphosphoryl) acetate, 2-propynyl-2- (dimethoxyphosphoryl) acetate, and 2-propynyl-2- (diethoxyphosphoryl) acetate are preferred, trisphosphate (2,2,2-trifluoroethyl), phosphoric acid. Tris (1,1,1,3,3,3-hexafluoropropane-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, and 2-propynyl-2- (diethoxyphosphoryl) acetate are more preferred.

As the cyclic acid anhydride, succinic anhydride, maleic anhydride, and 3-allyl succinic anhydride are preferable, and succinic anhydride and 3-allyl succinic anhydride are more preferable.

Among the above, at least one selected from the group consisting of (A) a polyvalent nitrile compound, (D) a triple bond-containing compound, (E) a non-lithium compound containing an S = O group, and (F) a cyclic acetal compound. Is preferable because the continuous charging characteristics in a high temperature and high voltage environment are further improved.

The total content of the compounds (A) to (H) is preferably 0.01 to 7% by mass in the non-aqueous electrolytic solution. In this range, the coating is sufficiently formed without becoming too thick, and the continuous charging characteristics under a higher temperature and high voltage environment are further enhanced. The total content is more preferably 0.05% by mass or more, further preferably 0.1% by mass or more, and the upper limit thereof is more preferably 5% by mass or less, further preferably 3% by mass or less in the non-aqueous electrolytic solution. preferable.

(Electrolyte salt)
Preferred examples of the electrolyte salt used in the present invention include the following lithium salts.
Lithium salts include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , 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 the like, and lithium salts containing a chain-like fluoroalkyl group are preferably mentioned. , At least one lithium salt selected from these is preferably mentioned, and one or two or more of these can be mixed and used.
Among these, LiPF ₆ and LiBF ₄ are preferable, and LiPF ₆ is most preferable. The concentration of the electrolyte salt is usually preferably 0.3 M or more, more preferably 0.7 M or more, still more preferably 1.1 M or more in the non-aqueous electrolytic solution. The upper limit thereof is preferably 2.5 M or less, more preferably 2.0 M or less, and even more preferably 1.6 M or less.

Further, for the purpose of further improving the continuous charging characteristics in a high temperature and high voltage environment, a lithium salt (I) having a oxalic acid structure and a lithium salt (II) having a phosphoric acid structure are further contained in the non-aqueous electrolytic solution. It is preferable to contain one or more lithium salts selected from the group consisting of a lithium salt (III) having an S = O group and a lithiumimide salt (IV) having a fluorine atom.

Lithium salts (I) having an oxalic acid structure include lithium bis (oxalat) borate (LiBOB), lithium difluoro (oxalat) borate (LiDFOB), lithium tetrafluoro (oxalat) phosphate (LiTFOP), and lithium difluorobis (oxalat). ) Phosphate (LiDFOP) is preferably mentioned, and among these, LiBOB, LiDFOB, and LiDFOP are preferable.

Examples of the lithium salt (II) having a phosphoric acid structure include lithium difluorophosphate (LiPO ₂ F ₂ ), lithium fluorophosphate (Li ₂ PO ₃ F), lithium bis (difluorophosphoryl) amide, and lithium (difluorophosphoryl) (. Lithium salts having a phosphoric acid structure such as fluorooxide phosphoryl) amide are preferably mentioned, and among these, LiPO ₂ F ₂ and Li ₂ PO ₃ F are more preferable, and LiPO ₂ F ₂ is further preferable.

Examples of the lithium salt (III) having an S = O group include lithium fluorosulfate (FSO ₃ Li), lithium methyl sulfate (LMS), lithium ethyl sulfate (LES), and lithium 2,2,2-trifluoroethyl sulfate (LFES). ), Lithium trifluoro ((methanesulfonyl) oxy) borate (LiTFMSB), lithium pentafluoro ((methanesulfonyl) oxy) phosphate (LiPFMSP), among these, LMS, LES, FSO ₃ Li, LFES. And LiTFMSB are preferable, and LMS and LES are more preferable.

In the non-aqueous electrolytic solution of the present invention, the content of each of the lithium salts (I), (II) or (III) is preferably 0.001 to 0.2 M in the non-aqueous electrolytic solution. If the content is 0.2 M or less, there is little possibility that an excessive film is formed on the electrode and the electrochemical characteristics are deteriorated, and if it is 0.001 M or more, after continuous charging in a high temperature and high voltage environment. The effect of suppressing the decrease in the average discharge voltage is sufficient, and the effect of improving the battery characteristics after continuous charging is enhanced. The content is preferably 0.01 M or more, more preferably 0.03 M or more, and particularly preferably 0.04 M or more in the non-aqueous electrolytic solution. The upper limit is preferably 0.15 M or less, and more preferably 0.12 M or less.

Lithium imide salts (IV) having a fluorine atom include (CF ₂ ) ₂ (SO ₂ ) ₂ NLi, (CF ₂ ) ₃ (SO ₂ ) ₂ NLi, LiN (SO ₂ F) ₂ (LiFSI), LiN ( One or more selected from the group consisting of SO ₂ CF ₃ ) ₂ (LiTFSI) and LiN (SO ₂ C ₂ F ₅ ) ₂ are preferably mentioned, and among these, one or more selected from LiTFSI and LiFSI. Is more preferable, and LiFSI is further preferable.

In the non-aqueous electrolytic solution of the present invention, the content of the lithium imide salt (IV) is preferably 0.01 to 1 M in the non-aqueous electrolytic solution. If the content is 1 M or less, there is little possibility that an excessive film is formed on the electrode and the electrochemical characteristics are deteriorated, and if it is 0.01 M or more, the average discharge after continuous charging in a high temperature and high voltage environment. The effect of suppressing the decrease in voltage is sufficient, and the effect of improving the battery characteristics after continuous charging is enhanced. The content is preferably 0.03 M or more, more preferably 0.05 M or more, and the upper limit thereof is preferably 0.9 M or less, more preferably 0.7 M or less in the non-aqueous electrolytic solution.

[Manufacturing of non-aqueous electrolyte solution]
The non-aqueous electrolyte solution of the present invention is, for example, mixed with the above-mentioned non-aqueous solvent, and the above-mentioned electrolyte salt, the compound represented by the general formula (I) with respect to the non-aqueous electrolyte solution, and a fluorine atom-containing cyclic carbonate. And can be obtained by adding at least one selected from the group consisting of unsaturated bond-containing cyclic carbonates.
At this time, it is preferable that the compound added to the non-aqueous solvent and the non-aqueous electrolytic solution to be used is purified in advance within a range that does not significantly reduce the productivity, and has as few impurities as possible.

The non-aqueous electrolyte solution of the present invention can be used for the following first to fourth power storage devices, and as the non-aqueous electrolyte, not only a liquid one but also a gelled one can be used. Further, the non-aqueous electrolyte solution of the present invention can also be used for solid polymer electrolytes. Among these, it is preferable to use it for a first power storage device (that is, for a lithium battery) or a fourth power 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. It is more preferable, and it is most suitable to be used for a lithium secondary battery.

[First power storage device (lithium battery)]
The lithium battery, which is the first power storage device according to the present invention, is a general term for a lithium primary battery and a lithium secondary battery, and 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 positive electrode, the negative electrode, and the non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a non-aqueous solvent. Components other than the non-aqueous electrolyte solution, such as positive electrodes and negative electrodes, can be used without particular limitation.

(Positive electrode active material)
For example, as the positive electrode active material for a lithium secondary battery, a composite metal oxide containing one or more selected from the group consisting of cobalt, manganese, and nickel is used. These positive electrode active materials can be used alone or in combination of two or more.
Examples of such a lithium composite metal oxide include LiCoO ₂ , LiCo _1-x M _x O ₂ (where M is Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, and One or more elements selected from the group consisting of Cu, 0.001 ≤ x ≤ 0.05), LiMn ₂ O ₄ , LiNiO ₂ , LiCo _1-x Ni _x O ₂ (0.01 <x < 1), LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , LiNi _0.8 Mn _0.1 Co _0.1 O ₂ , LiNi _{0 .8} Co _0.15 Al _0.05 O ₂ , Li ₂ MnO ₃ and LiMO ₂ (M is a transition metal such as Co, Ni, Mn, Fe), and LiNi _1/2 Mn _3/2 O. One or more selected from the group consisting of ₄ is more preferable. Further, LiCoO ₂ and LiMn ₂ O ₄ , LiCoO ₂ and LiNiO ₂ , and LiMn ₂ O ₄ and LiNiO ₂ may be used in combination.

When a lithium composite metal oxide that operates at a high charging voltage is used, the continuous charging characteristics in a high temperature and high voltage environment generally tend to deteriorate due to the reaction with the electrolytic solution during charging. However, the lithium according to the present invention. In the secondary battery, these deteriorations in electrochemical characteristics can be suppressed.
In particular, when a positive electrode active material containing Ni is used, in general, the catalytic action of Ni causes decomposition of the non-aqueous solvent on the surface of the positive electrode, and the resistance of the battery tends to increase. In particular, the continuous charging characteristics tend to deteriorate in a high temperature and high voltage environment, but the lithium secondary battery according to the present invention is preferable because it can suppress the deterioration of these electrochemical characteristics. In particular, when a positive electrode active material in which the ratio of the atomic concentration of Ni to the atomic concentration of all transition metal elements in the positive electrode active material exceeds 10 atomic%, the above effect becomes remarkable, and 20 atomic% or more is more preferable. , 30% or more is particularly preferable. Specifically, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , LiNi _0.8 Mn _0.1 Co _0.1 O ₂ , One or more selected from the group consisting of LiNi _0.8 Co _0.15 Al _0.05 O ₂ and the like are preferably mentioned.

Further, a 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 iron, cobalt, nickel and manganese is preferable. Specific examples thereof include LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiMnPO ₄ , and LiFe _1-x Mn _x PO ₄ (0.1 <x <0.9).
Some of these lithium-containing olivine-type phosphates may be replaced with other elements, and some of iron, cobalt, nickel and manganese may be replaced with Co, Mn, Ni, Mg, Al, B, Ti, V and Nb. , Cu, Zn, Mo, Ca, Sr, W, Zr and the like, can be replaced with one or more elements selected from the group, or can be coated with a compound or carbon material containing these other elements. Among these, LiFePO ₄ and LiMnPO ₄ are preferable.
Further, the lithium-containing olivine-type phosphate can also be used, for example, by mixing with the above-mentioned positive electrode active material.
The lithium-containing olivine-type phosphate forms a stable phosphoric acid (PO ₄ ) structure and is excellent in thermal stability during charging, so that continuous charging characteristics in a high temperature and high voltage environment can be improved.

The positive electrodes for lithium primary batteries include 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, etc., oxides or chalcogen compounds of one or more metal elements, SO ₂ , SOCl ₂ , etc. Examples thereof include sulfur compounds and fluorocarbon (fluorinated graphite) represented by the general formula (CF _x ) _n . Among these, MnO ₂ , V ₂ O ₅ , and graphite fluoride are 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. Examples thereof include natural graphite (scaly graphite and the like), graphite such as artificial graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, and carbon black such as thermal black. Further, graphite and carbon black may be appropriately mixed and used. The amount of the conductive agent added to the positive electrode mixture is preferably 1 to 10% by mass, and particularly preferably 2 to 5% by mass.

For the positive electrode, the positive electrode active material is made of a conductive agent such as acetylene black or carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), a styrene / butadiene copolymer (SBR), or acrylonitrile and butadiene. Mix with a binder such as copolymer (NBR), carboxymethyl cellulose (CMC), or ethylene propylene dienter polymer, add a high boiling point solvent such as 1-methyl-2-pyrrolidone, and knead to make a positive mixture. After that, this positive electrode mixture is applied to an aluminum foil of a current collector, a lath plate made of stainless steel, etc., dried and pressure-molded, and then at a temperature of about 50 ° C to 250 ° C under vacuum for about 2 hours. It can be produced by heat treatment.
The density of the portion of the positive electrode excluding the current collector is usually 1.5 g / cm ³ or more, preferably 2 g / cm ³ or more, and more preferably 3 g / cm ³ in order to further increase the capacity of the battery. The above is more preferably 3.6 g / cm ³ or more. The upper limit is preferably 4 g / cm ³ or less.

(Negative electrode active material)
As the negative electrode active material for the lithium secondary battery, a titanium metal, a lithium alloy, and a carbon material capable of storing and releasing titanium [easy-plated carbon and difficulty in having a (002) plane spacing of 0.37 nm or more). Graphitized carbon, graphite with (002) surface spacing of 0.34 nm or less], tin (single unit), tin compound, silicon (single unit), silicon compound (SiOx: x <2), silicon alloy (Si-) M alloy: M contains at least one selected from the group consisting of Al, Ni, Cu, Fe, Ti and Mn), and from the group consisting of lithium titanate compounds such as Li ₄ Ti ₅ O ₁₂ and the like. One or more selected species are preferred.
Among these, it is more preferable to use a highly crystalline carbon material such as artificial graphite or natural graphite in terms of the occlusion and release capacity of lithium ions, and the interplanar spacing (d ₀₀₂ ) of the lattice plane (002) is 0. It is particularly 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.

A plurality of flat graphite fine particles are repeatedly subjected to mechanical actions such as compressive force, frictional force, and shearing force on artificial graphite particles having a massive structure in which they are assembled or bonded in a non-parallel manner, for example, scaly natural graphite particles. It is obtained from the X-ray diffraction measurement of the negative electrode sheet when the density of the portion of the negative electrode excluding the current collector is pressure-molded to a density of 1.5 g / cm ³ or more by using the sphericalized graphite particles. When the ratio I (110) / I (004) of the peak intensity I (110) on the (110) plane and the peak intensity I (004) on the (004) plane of the graphite crystal is 0.01 or more, it is further from the positive electrode active material. It is preferable because it improves the metal elution amount and the charge storage characteristics, more preferably 0.05 or more, and further preferably 0.1 or more. Further, the upper limit is preferably 0.5 or less, more preferably 0.3 or less, because the crystallinity may be lowered and the discharge capacity of the battery may be lowered due to excessive treatment.

Further, it is preferable that the highly crystalline carbon material (core material) is coated with a carbon material having a lower crystallinity than the core material because the continuous charging characteristics in a high temperature and high voltage environment are further improved. The crystallinity of the coated carbon material can be confirmed by a transmission electron microscope (TEM).
Highly crystalline carbon materials generally react with non-aqueous electrolytes during charging and tend to reduce continuous charging characteristics in high temperature and high voltage environments due to increased interfacial resistance. The lithium secondary battery according to the present invention has good continuous charging characteristics in a high temperature and high voltage environment.

Examples of the metal compound capable of storing and releasing lithium ions as the negative electrode active material include Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co and Ni. Examples thereof include compounds containing at least one metal element such as Cu, Zn, Ag, Mg, Sr, or Ba. These metal compounds may be used in any form such as elemental substances, alloys, oxides, nitrides, sulfides, borohydrides, alloys with lithium, etc., but any simple substance, alloys, oxides, alloys with lithium, etc. It 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 with a conductive agent, a binder, and a high boiling point solvent similar to those for producing the positive electrode to obtain a negative electrode mixture, and then this negative electrode mixture is applied to a copper foil or the like of a current collector. It can be produced by drying, pressure molding, and then heat-treating at a temperature of about 50 ° C. to 250 ° C. under vacuum for about 2 hours.
The density of the portion of the negative electrode excluding the current collector is usually 1.1 g / cm ³ or more, preferably 1.5 g / cm ³ or more, and particularly preferably 1.7 g in order to further increase the capacity of the battery. / Cm ³ or more. The upper limit is preferably 2 g / cm ³ or less.

Moreover, as a negative electrode active material for a lithium primary battery, a lithium metal or a lithium alloy can be mentioned.

The structure of the lithium battery is not particularly limited, and a coin-type battery having a single-layer or multi-layer separator, a cylindrical battery, a square battery, a laminated battery, or the like can be applied.
The separator for a battery is not particularly limited, but a single-layer or laminated microporous film of polyolefin such as polypropylene or polyethylene, a woven fabric, a non-woven fabric or the like can be used.

The lithium secondary battery in the present invention is excellent in continuous charging characteristics in a high temperature and high voltage environment even when the charge termination voltage is 4.2 V or more, particularly 4.3 V or more, and further, the characteristics even at 4.4 V or more. Is good. The discharge termination voltage is usually 2.8 V or more, further 2.5 V or more, but the lithium secondary battery in the present invention can be 2.0 V or more. The current value is not particularly limited, but is usually used in the range of 0.1 to 30C. Further, the lithium battery in the present invention can be charged and discharged at −40 to 100 ° C., preferably −10 to 80 ° C.

In the present invention, as a measure against an increase in the internal pressure of the lithium battery, a method of providing a safety valve on the battery lid or making a notch in a member such as a battery can or a gasket can be adopted. Further, as a safety measure for preventing overcharging, a current cutoff mechanism that senses the internal pressure of the battery and cuts off the current can be provided on the battery lid.

[Second power storage device (electric double layer capacitor)]
The second energy storage device according to the present invention is a storage device containing the non-aqueous electrolytic solution of the present invention and storing energy by utilizing the electric double layer capacity at the interface between the electrolytic solution and the electrode. An example of the present invention is an electric double layer capacitor. The most typical electrode active material used in this power storage device is activated carbon. The double layer capacity increases roughly in proportion to the surface area.

[Third power storage device]
The third storage device according to the present invention is a storage device containing the non-aqueous electrolytic solution of the present invention and storing energy by utilizing the doping / dedoping reaction of the electrodes. 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 the doping / dedoping reaction of the electrodes.

[Fourth power storage device (lithium ion capacitor)]
The fourth power storage device according to the present invention is a power storage device containing the non-aqueous electrolytic solution of the present invention and storing energy by utilizing the intercalation of lithium ions with a carbon material such as graphite which is 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, those using a dope / dedoping reaction of a π-conjugated polymer electrode, and the like. The electrolytic solution contains at least a lithium salt such as LiPF ₆ .

Hereinafter, examples of the electrolytic solution using the compound of the present invention will be shown, but the present invention is not limited to these examples.

Examples 1 to 45, Comparative Examples 1 to 4
[Manufacturing of lithium-ion secondary battery]
LiNi _0.8 Co _0.1 Mn _0.1 O ₂ 92% by mass and 5% by mass of acetylene black (conductive agent) are mixed, and 3% by mass of polyvinylidene fluoride (binding agent) is preliminarily added to 1-methyl-2-. It was added to the solution dissolved in pyrrolidone and mixed to prepare a positive mixture paste. This positive electrode mixture paste was applied to one side of an aluminum foil (current collector), dried and pressure-treated, and cut to a predetermined size to prepare a positive electrode sheet. The density of the portion of the positive electrode excluding the current collector was 3.6 g / cm ³ .
Further, 5% by mass of silicon (elemental substance), 90% by mass of artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material), and 5% by mass of polyvinylidene fluoride (binding agent) were previously converted to 1-methyl-2-pyrrolidone. It was added to the dissolved solution and mixed 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 pressure-treated, and cut to a predetermined size to prepare a negative electrode sheet. The density of the portion of the negative electrode excluding the current collector was 1.5 g / cm ³ . Further, as a result of X-ray diffraction measurement using this electrode sheet, the ratio of the peak intensity I (110) on the (110) plane and the peak intensity I (004) on the (004) plane of the graphite crystal [I (110) / I). (004)] was 0.1.
Then, the positive electrode sheet, the separator made of a microporous polyethylene film, and the negative electrode sheet were laminated in this order, and the non-aqueous electrolytic solution having the composition shown in Tables 1 to 5 was added to prepare a laminated battery.
The ionic liquid used in Comparative Example 4 was produced according to Synthesis Example 2 of JP-A-2008-123988, and its structure is as follows.

[Evaluation of high temperature continuous charging characteristics]
<Initial discharge capacity>
Using the laminated battery produced by the above method, the battery is charged in a constant temperature bath at 25 ° C. with a constant current and constant voltage of 0.2 C to a final voltage of 4.3 V for 7 hours, and then shuts off under a constant current of 0.2 C. The initial discharge capacity was obtained by discharging to a voltage of 2.5 V. Then, it was charged with a constant current and a constant voltage of 1C to a final voltage of 4.3V for 3 hours, and discharged to a final voltage of 2.5V under a constant current of 1C. The average discharge voltage when discharging with this constant current of 1C was taken as the initial average discharge voltage.

<Continuous charging test>
Next, this laminated battery was charged to 4.3 V with a constant current of 0.2 C in a constant temperature bath at 60 ° C., then switched to a constant voltage and continuously charged for 7 days. Then, it was placed in a constant temperature bath at 25 ° C. and discharged to a final voltage of 2.5 V under a constant current of 1 C.
Subsequently, in a constant temperature bath at 25 ° C., the battery is continuously charged with a constant current and constant voltage of 0.2 C for 7 hours to a final voltage of 4.3 V, and then discharged to a final voltage of 2.5 V under a constant current of 0.2 C. The recovery discharge capacity after charging was calculated. The discharge capacity recovery rate after continuous charging was calculated by the following formula.
Discharge capacity recovery rate (%) = (recovery discharge capacity / initial discharge capacity) x 100

<Average discharge voltage drop rate after continuous charging>
Subsequently, the battery was charged with a constant current and constant voltage of 1C to a final voltage of 4.3V for 3 hours, and discharged to a final voltage of 2.5V under a constant current of 1C. The average discharge voltage change rate was calculated by the following formula, with the average discharge voltage when discharged at a constant current of 1C as the average discharge voltage after continuous charging.
Average discharge voltage change rate (relative value) (%) = (initial average discharge voltage-average discharge voltage after continuous charging) / (initial average discharge voltage of Comparative Example 1-average discharge after continuous charging of Comparative Example 1) Voltage) x 100

All of the lithium secondary batteries of Examples 1 to 45 are stored at a higher temperature than Comparative Example 1 containing no additive of the present invention and Comparative Example 2 containing only a compound represented by the general formula (I). The capacity recovery rate and the average discharge voltage reduction rate of the above are remarkably improved.
Further, as shown in Comparative Example 3, in the non-aqueous electrolytic solution to which the methylcyclohexyl carbonate and allylmethylcarbonate described in JP-A-2008-123988 (Patent Document 1) are added, the capacity recovery rate and the average discharge voltage decrease after high temperature storage. The improvement in rate was inadequate.
In addition, even in the electrolytic solution containing cyclohexylmethyl carbonate and the ionic liquid described in Patent Document 1, the improvement in the capacity recovery rate and the average discharge voltage decrease rate after high-temperature storage was insufficient. From the above, the effect of the present invention is that in a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, a specific amount of the compound represented by the general formula (I), a fluorine atom-containing cyclic carbonate and a non-aqueous electrolyte solution of the present invention are obtained. It was found that the effect is peculiar when at least one selected from the group consisting of a cyclic carbonate containing a saturated bond is contained in combination.

Further, the non-aqueous electrolyte solution of the present invention also has an effect of improving the capacity recovery rate and the average discharge voltage decrease rate after high temperature storage of lithium ion capacitors, lithium air batteries and the like.

By using the non-aqueous electrolytic solution of the present invention, it is possible to obtain a power storage device having excellent continuous charging characteristics in a high temperature and high voltage environment. In particular, when used as a non-aqueous electrolyte solution for power storage devices installed in hybrid electric vehicles, plug-in hybrid electric vehicles, battery electric vehicles, etc., storage devices that can improve continuous charging characteristics in high temperature and high voltage environments are available. Obtainable.

Claims (13)

A non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolytic solution contains 0.1 to 4% by mass of the compound represented by the following general formula (I) as an additive. A non-aqueous electrolytic solution for a power storage device, which comprises 0.1 to 30% by mass of at least one selected from the group consisting of a cyclic carbonate containing a fluorine atom and a cyclic carbonate containing an unsaturated bond.

(In the formula, R ¹ represents an alkyl group having 1 to 7 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms, and R ² to R ⁶ independently represent a hydrogen atom and an alkyl group having 1 to 4 carbon atoms. Or -CH ₂ OC (= O) OR ⁷ groups, R ⁷ indicates an alkyl group having 1 to 4 carbon atoms, and n = 0 or 1. The compound represented by the general formula (I) is methylcyclohexyl carbonate, methyl (2-methylcyclohexyl) carbonate, methyl (3-methylcyclohexyl) carbonate, methyl (4-methylcyclohexyl) carbonate, ethylcyclohexylcarbonate, ethyl ( 2-Methylcyclohexyl carbonate, ethyl (3-methylcyclohexyl) carbonate, ethyl (4-methylcyclohexyl) carbonate, dicyclohexyl carbonate, cyclohexylmethylmethylcarbonate, cyclohexylmethylethylcarbonate, bis (cyclohexylmethyl) carbonate, cyclohexane-1,4 The non-aqueous electrolyte solution according to claim 1, which is at least one selected from the group consisting of diylbis (methyl) dimethylbis (carbonate) and cyclohexane-1,4-diylbis (methylene) diethylbis (carbonate). One or more of the fluorine atom-containing cyclic carbonates selected from the group consisting of 4-fluoro-1,3-dioxolane-2-one and trans or cis-4,5-difluoro-1,3-dioxolan-2-one. The non-aqueous electrolyte solution according to claim 1 or 2. The invention according to claim 1 or 2, wherein the unsaturated bond-containing cyclic carbonate is at least one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, and 4-ethynyl-1,3-dioxolane-2-one. Non-aqueous electrolyte. When the content of the compound represented by the general formula (I) is A mass%, and the content of at least one selected from the group consisting of the fluorine atom-containing cyclic carbonate and the unsaturated bond-containing cyclic carbonate is B mass%. The non-aqueous electrolyte solution according to any one of claims 1 to 4, wherein the A / B is in the range of 0.01 to 3. The non-aqueous electrolytic solution is one or more selected from the group consisting of a lithium salt having a oxalic acid structure, a lithium salt having a phosphoric acid structure, a lithium salt having an S = O group, and a lithiumimide salt having a fluorine atom. The non-aqueous electrolytic solution according to any one of claims 1 to 5, which contains a lithium salt. The lithium salt having an oxalic acid structure is one or 2 selected from the group consisting of lithium bis (oxalat) borate, lithium difluoro (oxalat) borate, lithium tetrafluoro (oxalat) phosphate, and lithium difluorobis (oxalat) phosphate. The non-aqueous electrolyte solution according to claim 6, which is more than a seed. The lithium salt having a phosphoric acid structure is one or 2 selected from the group consisting of LiPO ₂ F ₂ , Li ₂ PO ₃ F, lithium bis (difluorophosphoryl) amide, and lithium (difluorophosphoryl) (fluorooxide phosphoryl) amide. The non-aqueous electrolyte solution according to claim 6, which is more than a seed. The lithium salt having an S = O group is lithium trifluoro ((methanesulfonyl) oxy) borate, lithium pentafluoro ((methanesulfonyl) oxy) phosphate, lithium methyl sulfate, lithium ethyl sulfate, lithium 2,2,2-. The non-aqueous electrolytic solution according to claim 6, which is one or more selected from the group consisting of trifluoroethyl sulfate and FSO ₃ Li. The non-aqueous electrolytic solution according to claim 6, wherein the lithium imide salt having a fluorine atom is one or two selected from LiN (SO ₂ F) ₂ and LiN (SO ₂ CF ₃ ) ₂ . The non-aqueous electrolytic solution according to any one of claims 1 to 10, wherein the non-aqueous electrolytic solution contains one or more chain esters in a non-aqueous solvent. Claimed that the chain ester is one or two selected from dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and methyl pivalate. Item 11. The non-aqueous electrolytic solution according to Item 11. The non-aqueous electrolytic solution according to any one of claims 1 to 12, wherein the storage device comprises a non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a non-aqueous solvent. A power storage device characterized by being a liquid.