WO2019073831A1 - Method for preventing decomposition of silyl ester compound - Google Patents

Abstract

The present invention is a method for preventing the decomposition of a silyl ester compound selected from the group consisting of a carboxylic acid silyl ester compound, a sulfuric acid silyl ester compound, a sulfonic acid silyl ester compound, a phosphorous acid silyl ester compound, a phosphoric acid silyl ester compound and a boric acid silyl ester compound in a electrolyte solution containing a lithium salt containing a fluorine atom, the silyl ester compound and an organic solvent, wherein a phenylsilane compound represented by general formula (1) is added to the non-aqueous electrolyte solution in an amount of 0.1 to 10% by mass and the water content in the non-aqueous electrolytic solution is adjusted to 1000 ppm by mass or less. (With respect to the definition for each symbol in the formula, see the description.)

Description

Method for suppressing decomposition of silyl ester compound

The present invention relates to a method for suppressing the decomposition of a silyl ester compound in a non-aqueous electrolytic solution in which a lithium salt containing a fluorine atom and a silyl ester compound are dissolved in an organic solvent.

With the widespread use of portable personal computers, handy video cameras, and portable electronic devices for information terminals in recent years, non-aqueous electrolyte secondary batteries having high voltage and high energy density have been widely used as power supplies. In addition, from the viewpoint of environmental problems, commercialization of electric vehicles and hybrid vehicles using electric power as part of their motive power has been performed. Among non-aqueous electrolyte secondary batteries, secondary batteries (so-called lithium ion secondary batteries) that use lithium absorption and release for charge and discharge reactions have higher energy density than lead batteries and nickel cadmium batteries. Are widely used from being

In a lithium ion secondary battery, a non-aqueous electrolytic solution in which a lithium salt containing a fluorine atom such as lithium hexafluorophosphate as an electrolyte is dissolved in a carbonate-based organic solvent such as propylene carbonate or diethyl carbonate is used. Carboxylic acid silyl esters (see, for example, patent documents 1 to 3), sulfuric acid silyl esters (for example, see patent documents 4 to 5), sulfonic acid silyl esters (for example, patent document 4) 6), phosphoric silyl esters (see, for example, Patent Documents 5, 7, and 8), boric acid silyl esters (see, for example, Patent Documents 5 and 9), and the like. An electrolyte is being considered.

It is known that the lithium salt containing a fluorine atom is gradually hydrolyzed by water to generate hydrofluoric acid, and when the silyl ester compound is decomposed by hydrofluoric acid, there is a case where improvement in cycle characteristics can not be observed. Therefore, lactone compounds (see, for example, Patent Document 10), cycloolefin compounds (see, for example, Patent Document 11), silane compounds having SiH groups (see, for example, Patent Document 12) as scavengers of hydrofluoric acid Although organosilicon compounds having Si-N bonds (see, for example, Patent Document 13), alkoxysilane compounds (see, for example, Patent Document 14), and the like have been studied, these scavengers have a rate of hydrofluoric acid capture In the case where the water content in the electrolytic solution is high, the decomposition of the silyl ester compound may not be effectively suppressed.

JP 2002-313416 A US2006172200A1 WO 2016/013480 brochure US2002197537A1 Unexamined-Japanese-Patent No. 2006-253086 US2013022861A1 Japanese Patent Application Laid-Open No. 2001-1919685 Japanese Patent Application Publication No. 2004-342607 JP 2001-283908 A JP 2000-182666 A JP, 2002-280062, A JP, 2001-167792, A Japanese Patent Application Laid-Open No. 11-016602 US2016248121A1

An object of the present invention is to suppress decomposition of a silyl ester compound in a non-aqueous electrolytic solution in which a lithium salt containing a fluorine atom and a silyl ester compound are dissolved in an organic solvent, even when some water is present. It is to improve storage stability.

As a result of intensive studies, the present inventors have found that a silane compound having a specific structure is highly effective in suppressing the decomposition of a silyl ester compound, and completed the present invention.

That is, the present invention relates to a lithium salt containing a fluorine atom, a carboxylic acid silyl ester compound, a sulfuric acid silyl ester compound, a sulfonic acid silyl ester compound, a phosphorous acid silyl ester compound, a phosphoric acid silyl ester compound and a boric acid silyl ester compound A method for suppressing the decomposition of a silyl ester compound in a non-aqueous electrolytic solution containing a silyl ester compound selected from the group consisting of
The phenylsilane compound represented by the following general formula (1) is blended in an amount of 0.1 to 10% by mass in the non-aqueous electrolytic solution, and the water content of the non-aqueous electrolytic solution is 1,000 mass ppm or less And a method for suppressing the decomposition of silyl ester compounds.

（式中、Ｒ¹、Ｒ²、Ｒ³、Ｒ⁴及びＲ⁵はおのおの独立して水素原子、ハロゲン原子、ニトリル基、ニトロ基、炭素数１～１２のアルキル基、炭素数２～１２のアルケニル基、炭素数５～１２のシクロアルキル基、炭素数６～１２のアリール基、炭素数７～１２のアラルキル基、炭素数１～１２のオキシアルキル基、炭素数１～１２のアシル基又は－ＳｉＲ⁸Ｒ⁹Ｒ¹⁰で表される基を表わし、Ｒ⁶、Ｒ⁷、Ｒ⁸、Ｒ⁹及びＲ¹⁰はおのおの独立して炭素数１～１２のアルキル基、炭素数２～１２のアルケニル基、炭素数５～１２のシクロアルキル基、炭素数６～１２のアリール基又は炭素数７～１２のアラルキル基を表わし、Ｘ¹はｍ価の炭化水素基を表わし、ｍは１～３の数を表わす。）

(Wherein R ¹ , R ² , R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom, a halogen atom, a nitrile group, a nitro group, an alkyl group having 1 to 12 carbon atoms, or 2 to 12 carbon atoms) Alkenyl group, cycloalkyl group having 5 to 12 carbon atoms, aryl group having 6 to 12 carbon atoms, aralkyl group having 7 to 12 carbon atoms, oxyalkyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms -SiR ⁸ R ⁹ R ¹⁰ represents a group represented by R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ each independently being an alkyl group having 1 to 12 carbon atoms and alkenyl having 2 to 12 carbon atoms Group, a cycloalkyl group having 5 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms, X ¹ represents an m-valent hydrocarbon group, and m is 1 to 3 Represents a number)

FIG. 1 is a longitudinal sectional view schematically showing an example of the structure of a coin-type battery of a secondary battery as an example of the application of the non-aqueous electrolyte in the method of the present invention. FIG. 2 is a schematic view showing a basic configuration of a cylindrical battery of a secondary battery as an example of application of the non-aqueous electrolyte in the method of the present invention. FIG. 3 is a perspective view showing, as a cross section, the internal structure of a cylindrical battery of a secondary battery as an example of the application of the non-aqueous electrolyte in the method of the present invention.

Hereinafter, preferred embodiments of the present invention will be described.
In the general formula (1), R ¹ , R ² , R ³ , R ⁴ and R ⁵ (hereinafter also referred to as “R ¹ to R ⁵ ”) each independently represent a hydrogen atom, a halogen atom, a nitrile group, a nitro Group, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, This represents an oxyalkyl group of 1 to 12, an acyl group of 1 to 12 carbon atoms, or a group represented by -SiR ⁸ R ⁹ R ¹⁰ . As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom etc. are mentioned.

Examples of the alkyl group having 1 to 12 carbon atoms include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group and isopropyl group. Examples thereof include isobutyl group, s-butyl group, t-butyl group, isopentyl group, neopentyl group, 1-methylbutyl group, isohexyl group, 2-ethylhexyl group and 2-methylhexyl group.
As a C2-C12 alkenyl group, a vinyl group, an allyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, 1,3-butanedienyl group, 1-methylvinyl group, 2-methylvinyl group 1-methyl allyl group, 1,1-dimethyl allyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group and the like.

Examples of the cycloalkyl group having 5 to 12 carbon atoms include a cyclopentyl group, a cyclohexyl group and a 2-norbornyl group.
Examples of the aryl group having 6 to 12 carbon atoms include phenyl group, biphenyl group, naphthyl group, tolyl group, xylyl group, mesityl group and ethylphenyl group.
Examples of the aralkyl group having 7 to 12 carbon atoms include benzyl group, phenylethyl group, phenylpropyl group, tolylmethyl group, tolylethyl group, tolylpropyl group, xylylmethyl group, xylylethyl group, xylylpropyl group and the like.

Examples of the oxyalkyl group having 1 to 12 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, an octyloxy group and a decyloxy group.
Examples of the acyl group having 1 to 12 carbon atoms include methanoyl group, ethanolyl group, propanoyl group, butanoyl group, butanoyl group, pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group, decanoyl group, decanoyl group, undecanoyl group, dodecanoyl group and the like. .

R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ (hereinafter also referred to as “R ⁶ to R ¹⁰ ”) are each independently an alkyl group having 1 to 12 carbon atoms and an alkenyl group having 2 to 12 carbon atoms And a cycloalkyl group having 5 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms. Examples of the alkyl group having 1 to 12 carbon atoms, the alkenyl group having 2 to 12 carbon atoms, the cycloalkyl group having 5 to 12 carbon atoms, the aryl group having 6 to 12 carbon atoms and the aralkyl group having 7 to 12 carbon atoms include R ¹ alkyl group ~ R ⁵ having 1 to 12 carbon atoms exemplified by an alkenyl group having 2 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, 6 to 12 carbon atoms an aryl group and aralkyl of 7 to 12 carbon atoms Each group is mentioned.

As R ¹ to R ⁵ , a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, or —SiR ⁸ R ⁹ R ¹⁰ is preferable, and a hydrogen atom or a fluorine is preferable because industrial raw materials are easily obtained. Atoms are more preferred. Further, it is also preferable that one or two of R ¹ to R ⁵ be -SiR ⁸ R ⁹ R ¹⁰ . In this case, the remainder of R ¹ to R ⁵ is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and it is particularly preferable that the remainder of R ¹ to R ⁵ is a hydrogen atom.
As R ⁶ and R ⁷ , an alkyl group having 1 to 4 carbon atoms or a phenyl group is preferable, and a methyl group is more preferable because industrial raw materials are easily obtained.
As R ⁸ , R ⁹ and R ¹⁰ , an alkyl group having 1 to 4 carbon atoms or a phenyl group is preferable, and a methyl group is more preferable, because industrial raw materials can be easily obtained.

X ¹ represents an m-valent hydrocarbon group, and m represents a number of 1 to 3. The monovalent hydrocarbon group in the case where m is a number of 1 includes, for example, the alkyl group having 1 to 12 carbon atoms, the alkenyl group having 2 to 12 carbon atoms, and the cycloalkenyl having 5 to 12 carbon atoms exemplified for R ¹ to R ⁵ Examples thereof include an alkyl group, an aryl group having 6 to 12 carbon atoms and an aralkyl group having 7 to 12 carbon atoms.

Examples of the divalent hydrocarbon group when m is a number of 2 include methane-1,1-diyl, ethane-1,2-diyl, ethane-1,1-diyl and propane-1,3- Diyl group, propane-1,2-diyl group, butane-1,4-diyl group, 2-methylpropane-1,3-diyl group, 2,2-dimethylpropane-1,3-diyl group, pentane-1 3,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group And C 1 -C 10 alkanediyl groups; groups represented by the following general formula (6), groups represented by the following general formula (7), and the like. In the alkanediyl group having 3 or more carbon atoms, one or more methylene groups other than at both ends may be replaced by -S- or -O-.

（式中、Ｒ⁴⁵及びＲ⁴⁶はおのおの独立して、炭素数１～１０のアルカンジイル基又は直接結合を表わす。）

(Wherein, R ⁴⁵ and R ⁴⁶ each independently represent an alkanediyl group having 1 to 10 carbon atoms or a direct bond).

（式中、Ｒ⁴⁷及びＲ⁴⁸はおのおの独立して、炭素数１～１０のアルカンジイル基又は直接結合を表わす。）

(Wherein, each of R ⁴⁷ and R ⁴⁸ independently represents an alkanediyl group having 1 to 10 carbon atoms or a direct bond).

Examples of the trivalent hydrocarbon group when m is a number of 3 include methane-1,1,1-triyl group, ethane-1,1,1-triyl group, propane-1,1,1-triyl group, Propane-1,2,3-triyl group, pentane-1,3,5-triyl group, hexane-1,1-triyl group, octane-1,1,1-triyl group, decane-1,1,1- Examples thereof include alkanetriyl groups having 1 to 10 carbon atoms such as a triyl group; groups represented by the following general formula (8), groups represented by the following general formula (9), and the like.

（式中、Ｒ⁴⁹、Ｒ⁵⁰及びＲ⁵¹はおのおの独立して、炭素数１～１０のアルカンジイル基又は直接結合を表わす。）

(Wherein, each of R ⁴⁹ , R ⁵⁰ and R ⁵¹ independently represents an alkanediyl group having 1 to 10 carbon atoms or a direct bond).

（式中、Ｒ⁵²、Ｒ⁵³及びＲ⁵⁴はおのおの独立して、炭素数１～１０のアルカンジイル基又は直接結合を表わす。）

(Wherein, each of R ⁵² , R ⁵³ and R ⁵⁴ independently represents an alkanediyl group having 1 to 10 carbon atoms or a direct bond).

The C 1-10 alkanediyl group represented by R ⁴⁵ , R ⁴⁶ , R ⁴⁷ , R ⁴⁸ , R ⁴⁹ , R ⁵⁰ , R ⁵¹ , R ⁵² , R ⁵³ and R ⁵⁴ is represented by X ¹ And the groups exemplified above for the alkanediyl group having 1 to 10 carbon atoms as an example of the group.

Among the phenylsilane compounds represented by the general formula (1), particularly preferred compounds include trimethylphenylsilane, triethylphenylsilane, dimethyldiphenylsilane, methyltriphenylsilane, trimethyl-4-fluorophenylsilane and trimethyl-2 , 4,6-trifluorophenylsilane, butyldimethylphenylsilane, dimethyloctylphenylsilane, 1,4-bis (trimethylsilyl) benzene, 1,2-bis (trimethylsilyl) benzene, 1,4-bis (dimethylphenylsilyl) Benzene, 1,1,1-tris (dimethylphenylsilyl) ethane and the like can be mentioned.

The amount of addition of the phenylsilane compound represented by the general formula (1) to the non-aqueous electrolytic solution is preferably 0.1 to 10% by mass. When the addition amount is 0.1% by mass or more, a sufficient effect is easily exhibited. When the addition amount is 10% by mass or less, an increase effect corresponding to the addition amount is easily obtained, and there is a fear that the battery performance may be reduced by the increase. It can prevent. The amount of the phenylsilane compound represented by the general formula (1) to be added to the non-aqueous electrolyte is more preferably 0.1 to 7% by mass, still more preferably 0.5 to 7% by mass, and 1 to 5% by mass Most preferred.
There is no limitation on the timing of blending the phenylsilane compound represented by the general formula (1) in the non-aqueous electrolyte, and the phenylsilane compound is blended in the non-aqueous electrolyte together with the lithium salt, silyl ester compound and organic solvent It should be possible. For example, after mixing any of lithium salt, silyl ester compound and organic solvent into phenylsilane compound, other materials may be mixed, lithium salt, silyl ester compound, materials other than organic solvent, and phenylsilane After mixing the compounds, the lithium salt, the silyl ester compound, and the organic solvent may be mixed to prepare a non-aqueous electrolyte.

[Lithium salt containing fluorine atom]
The method for suppressing the decomposition of the silyl ester compound of the present invention is a method for suppressing the decomposition of the silyl ester compound in a non-aqueous electrolytic solution in which a lithium salt containing a fluorine atom and a silyl ester compound are dissolved in an organic solvent. The lithium salt containing a fluorine atom is a component to be blended as an electrolyte of the non-aqueous electrolyte. As lithium salt containing a fluorine atom, LiPF ₆ , LiBF ₄ , LiPO ₂ F ₂ , LiAsF ₆ , Li ₂ SiF ₆ , LiSbF ₆ , LiN (SO ₂ F) ₂ , LiOSO ₂ Rf (wherein, Rf is a fluorocarbon group) , LiN (SO ₂ Rf) ₂ (wherein, Rf represents a fluorocarbon group), and LiPF _a (Rf) _6-a (wherein, Rf represents a fluorocarbon group, and a is a number from 0 to 5) }, Etc. are mentioned. As a lithium salt containing a fluorine atom of a non-aqueous electrolytic solution to which the phenylsilane compound of the present invention is applied, decomposition of the silyl ester compound tends to occur while excellent battery performance is obtained, and decomposition by the phenylsilane compound of the present invention Since the suppression effect is increased, LiPF ₆ , LiBF ₄ , Li ₂ SiF ₆ , LiSbF ₆ , LiN (SO ₂ F) ₂ , LiOSO ₂ CF ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂₎ CF ₃ ) ₂ is preferred, LiPF ₆ , LiBF ₄ , LiN (SO ₂ F) ₂ , LiOSO ₂ CF ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ are more preferred, LiPF 6 ₆ , LiBF ₄ and LiN (SO ₂ CF ₃ ) ₂ are most preferred.

The electrolyte in the non-aqueous electrolyte may contain an electrolyte other than a lithium salt containing a fluorine atom, but when the proportion of the lithium salt containing a fluorine atom in the electrolyte is low, decomposition of the silyl ester compound hardly occurs Since it is difficult to obtain the effect of suppressing decomposition by the phenylsilane compound of the present invention, the ratio of the lithium salt containing a fluorine atom to the entire electrolyte is preferably at least 20 mol%. Examples of electrolytes other than lithium salts containing a fluorine atom include LiClO ₄ , LiCl, LiBr and the like. The concentration of the electrolyte in the non-aqueous electrolytic solution is preferably 0.1 mol / L to 7 mol / L, and more preferably 0.5 mol / L to 1.8 mol / L. When the electrolyte concentration is in this range, safety can be improved, and a battery having high reliability and contributing to the reduction of the environmental load can be obtained.

[Silyl ester compound]
Examples of silyl ester compounds include carboxylic acid silyl ester compounds, sulfuric acid silyl ester compounds, sulfonic acid silyl ester compounds, phosphorous acid silyl ester compounds, phosphoric acid silyl ester compounds, and boric acid silyl ester compounds. The content of the silyl ester compound in the non-aqueous electrolytic solution is preferably 0.01 to 7% by mass, more preferably 0.1 to 5% by mass, and most preferably 0.3 to 3% by mass.

As a carboxylic acid silyl ester compound, the compound represented by following General formula (2) is mentioned.

（式中、Ｒ¹¹、Ｒ¹²及びＲ¹³はおのおの独立して炭素数１～１２のアルキル基、炭素数２～１２のアルケニル基、炭素数５～１２のシクロアルキル基、炭素数６～１２のアリール基又は炭素数７～１２のアラルキル基を表わし、Ｘ²は直接結合又はｎ価の基を表わし、ｎは１～４の数を表わす。）

(Wherein R ¹¹ , R ¹² and R ¹³ each independently represent an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or 6 to 12 carbon atoms Or an aralkyl group having 7 to 12 carbon atoms, X ² represents a direct bond or an n-valent group, and n represents a number of 1 to 4).

In the general formula (2), R ¹¹ , R ¹² and R ¹³ (hereinafter also described as “R ¹¹ to R ¹³ ”) are each independently an alkyl group having 1 to 12 carbon atoms and an alkenyl having 2 to 12 carbon atoms And a cycloalkyl group having 5 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms. Examples of such groups include the groups exemplified as R ⁶ to R ¹⁰ in the general formula (1). As R ¹¹ to R ¹³ , a methyl group or a phenyl group is preferable, and a methyl group is more preferable, because industrial raw materials can be easily obtained.

X ² represents an n-valent group, and n represents a number of 1 to 4.
Examples of X ² when n is 1 include the same groups as the groups mentioned above as examples of X ¹ when m is 1 in the general formula (1), and the monovalent carbon number 2 There may be mentioned to 12 heterocyclic groups. The monovalent heterocyclic group having a carbon number of 2 to 12 is preferably one having a carbon number of 3 to 9, and is selected from pyrrole ring, furan ring, thiophene ring, pyrrolidine ring, tetrahydrofuran ring, tetrahydrothiophene ring, piperidine ring, tetrahydropyran Derived from a heterocyclic ring such as a ring, tetrahydrothiopyran ring, imidazole ring, pyrazole ring, oxazole ring, thiazole ring, imidazoline ring, pyrazine ring, morpholine ring, thiazine ring, or a polynuclear heterocyclic ring of these heterocycles and a benzene ring A monovalent group is mentioned.

When n is 1, X ² is an alkyl group having 2 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 6 to 8 carbon atoms, an aryl group having 6 to 10 carbon atoms, or 7 to carbon atoms 9 aralkyl group or heterocyclic group having 2 to 5 carbon atoms is preferable, and particularly alkenyl group having 2 to 10 carbon atoms, aryl group having 6 to 10 carbon atoms or aralkyl group having 7 to 9 carbon atoms Is preferred.

Examples of X ² when n is 2 include the same groups as the groups mentioned above as examples of X ¹ when m is 2 in the general formula (1), and direct bonding with 2 carbon atoms And an alkenediyl group of to 10 and a divalent heterocyclic group having 2 to 12 carbon atoms. Examples of the alkenediyl group having 2 to 10 carbon atoms include ethene-1,1-diyl group, ethene-1,2-diyl group, propene-1,2-diyl group, propene-1,3-diyl group, and propene-2 2,3-diyl group, 1-butene-1,2-diyl group, 1-butene-1,3-diyl group, 1-butene-1,4-diyl group, 2-pentene-1,5-diyl group, Examples thereof include 3-hexene-1,6-diyl group and the like. Examples of the divalent heterocyclic group having 2 to 12 carbon atoms include divalent groups derived from the heterocyclic ring or polynuclear heterocyclic ring mentioned in X ² when n is 1 and having 3 to 9 carbon atoms. Is preferred.

When n is 2, X ² is an alkanediyl group having 2 to 6 carbon atoms, an alkene diyl group having 2 to 6 carbon atoms, a group represented by general formula (6) or (7), a divalent carbon number of 2 to 6 A heterocyclic group containing 5 carbon atoms, preferably an alkanediyl group having 2 to 6 carbon atoms, an alkene diyl group having 2 to 6 carbon atoms, or a divalent heterocyclic group having 2 to 5 carbon atoms preferable. As mentioned above, the methylene group in the alkanediyl group may be replaced by -S- or -O-.

Examples of X ² when n is 3 include the same groups as the groups mentioned above as examples of X ¹ when m is 3 in the general formula (1), and further, trivalent carbon number 2 There may be mentioned to 12 heterocyclic groups. Examples of the trivalent group having a carbon number of 2 to 12 include trivalent groups derived from the heterocyclic ring or polynuclear heterocyclic ring mentioned in X ² where n is 1 and having 3 to 9 carbon atoms. Is preferred.
Examples of X ² when n is 4 include tetravalent groups corresponding to X ² when n is 1 to 3 mentioned above.

When n is 3, X ² is an alkanetriyl group having 3 to 6 carbon atoms, a group represented by general formula (8) or (9) or a trivalent heterocyclic group having 2 to 5 carbon atoms In particular, a group represented by the general formula (9) or a trivalent heterocyclic group having 2 to 5 carbon atoms is preferable.
When n is 4, X ² is an alkanetetrayl group having 4 to 6 carbon atoms, a tetravalent aromatic ring-containing group having 6 to 10 carbon atoms, or a tetravalent heterocyclic group having 2 to 5 carbon atoms. Is preferred.

In the present specification, when referring to “heterocyclic group containing 2 to 12 carbon atoms”, “2 to 12 carbon atoms” as used herein refers to the carbon number of only the heterocycle in the heterocyclic group. And the carbon number of the entire heterocycle-containing group is not defined.

The compound represented by the general formula (2) can be rephrased as a silyl ester of a carboxylic acid compound represented by the following general formula (2a), and the carboxyl group of the carboxylic acid compound represented by the general formula (2a) is known The compound represented by General formula (2) can be obtained by carrying out silyl esterification by the method of these.

（式中、Ｘ²及びｎは、一般式（１）と同義である。）

(Wherein, X ² and n are as defined in the general formula (1))

Among the carboxylic acid compounds represented by the general formula (2a), examples of the monocarboxylic acid in which n is 1 include acetic acid, propanoic acid, butanoic acid, pentanoic acid, isopentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, Acrylic acid, methacrylic acid, crotonic acid, benzoic acid, toluic acid, 4-t-butylbenzoic acid, naphthalenecarboxylic acid, phenylacetic acid, naphthylacetic acid, 4-methoxybenzoic acid, 2-thiophenecarboxylic acid, picolinic acid, nicotinic acid Etc.

Examples of dicarboxylic acids in which n is 2 include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, muconic acid, dihydromuconic acid, acetylenic dicarboxylic acid, 4- 4- Cyclohexene-1,2-dicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, 2,2'-thiodiacetic acid, ethylene dithiodiacetic acid, 3, 3'-thiodipropionic acid, 3,3'-dithiodipropionic acid, 2,5-thiophenedicarboxylic acid, 3,4-thiophenedicarboxylic acid, adamantanedicarboxylic acid, 2,5-furandicarboxylic acid, dipicolinic acid, etc. Dicarboxylic acid etc. are mentioned.

Examples of tricarboxylic acids wherein n is 3 include propane-1,2,3-tricarboxylic acid, pentane-1,3,5-tricarboxylic acid, benzene-1,2,3-tricarboxylic acid, benzene-1,2, Examples thereof include 4-tricarboxylic acid, benzene-1,3,5-tricarboxylic acid, thiophene-2,3,5-tricarboxylic acid and 1,3,5-trithiane-2,4,6-tricarboxylic acid.
Examples of tetracarboxylic acids in which n is 4 include dodecane-1,1,12,12-tetracarboxylic acid, cyclopentane-1,2,3,4-tetracarboxylic acid, benzene-1,2,3,4. -Tetracarboxylic acid, benzene-1,2,4,5-tetracarboxylic acid, tetrahydrofuran-2,3,4,5-tetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid and the like .

Examples of the sulfated silyl ester compound and the sulfonated silyl ester compound include compounds represented by the following general formula (3).

（式中、Ｒ¹⁴、Ｒ¹⁵、Ｒ¹⁶及びＲ¹⁷はおのおの独立して炭素数１～１２のアルキル基、炭素数２～１２のアルケニル基、炭素数５～１２のシクロアルキル基、炭素数６～１２のアリール基又は炭素数７～１２のアラルキル基を表わし、ｐは０又は１の数を表わす。）

(Wherein, R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ each independently represent an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or the like) Represents an aryl group of 6 to 12 or an aralkyl group having 7 to 12 carbon atoms, p represents a number of 0 or 1)

In the general formula (3), each of R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ (hereinafter also referred to as “R ¹⁴ to R ¹⁷ ”) independently represents an alkyl group having 1 to 12 carbon atoms, 2 to 6 carbon atoms 12 represents an alkenyl group, a cycloalkyl group having 5 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms. Examples of such groups include the groups exemplified as R ⁶ to R ¹⁰ in the general formula (1). p represents a number of 0 or 1, and when p is a number of 0, the compound represented by the general formula (3) is a sulfated silyl ester compound, and when p is a number of 1, a sulfonate silyl ester compound is there.

As R ¹⁴ , an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms is preferable because it is easy to obtain industrial raw materials. The R ^15, R ¹⁶ and R ^17, preferably an alkyl group or a phenyl group having 1 to 4 carbon atoms since the availability of industrial raw materials is easy, more preferably a methyl group or a phenyl group, especially a methyl group preferable.

When p in the general formula (3) is a number of 0, that is, when the compound represented by the general formula (3) is a silyl sulfate compound, preferred compounds include bis (trimethylsilyl) sulfate and bis (dimethylphenyl sulfate) And silyl), bis (methyldiphenylsilyl) sulfate, bis (triphenylsilyl) sulfate and the like.

When p in the general formula (3) is a number of 1, that is, when the compound represented by the general formula (3) is a sulfonic acid silyl ester compound, preferred compounds are trimethylsilyl methanesulfonate, dimethylphenyl methanesulfonate Examples include silyl, trimethylsilyl benzenesulfonate, trimethylsilyl toluenesulfonate and the like.

Examples of phosphorous acid silyl ester compounds and phosphoric acid silyl ester compounds include compounds represented by the following general formula (4).

（式中、Ｒ¹⁸、Ｒ¹⁹、Ｒ²⁰、Ｒ²¹、Ｒ²²、Ｒ²³、Ｒ²⁴、Ｒ²⁵及びＲ²⁶はおのおの独立して炭素数１～１２のアルキル基、炭素数２～１２のアルケニル基、炭素数５～１２のシクロアルキル基、炭素数６～１２のアリール基又は炭素数７～１２のアラルキル基を表わし、ｑは０又は１の数を表わす。）

(Wherein, R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ and R ²⁶ each independently represent an alkyl group having 1 to 12 carbon atoms and 2 to 12 carbon atoms And A represents an alkenyl group, a cycloalkyl group having 5 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms, and q represents a number of 0 or 1.)

In the general formula (4), R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ and R ²⁶ (hereinafter also referred to as “R ¹⁸ to R ²⁶ ”) are each independently And an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms. Examples of such groups include the groups exemplified as R ⁶ to R ¹⁰ in the general formula (1). As R ¹⁸ to R ²⁶ , an alkyl group having 1 to 4 carbon atoms or a phenyl group is preferable, a methyl group or a phenyl group is more preferable, and a methyl group is particularly preferable, because industrial raw materials can be easily obtained. q represents a number of 0 or 1, and when q is a number of 0, the compound represented by the general formula (4) is a phosphite silyl ester compound, and when q is a number of 1, a phosphate silyl ester It is a compound.

When q in the general formula (4) is a number of 0, that is, when the compound represented by the general formula (4) is a phosphite silyl ester compound, preferred compounds include tris (trimethylsilyl) phosphite, Examples thereof include tris (dimethylphenylsilyl) phosphate, tris (methyldiphenylsilyl) phosphite, and tris (triphenylsilyl) phosphite.

When q in the general formula (4) is a number of 1, that is, when the compound represented by the general formula (4) is a phosphoric acid silyl ester compound, preferable compounds include tris (trimethylsilyl) phosphate, tris phosphate (Dimethylphenylsilyl), tris (methyldiphenylsilyl) phosphate, tris (triphenylsilyl) phosphate and the like.

As a boric acid silyl ester compound, the compound represented by following General formula (5) is mentioned.

（式中、Ｒ²⁷、Ｒ²⁸、Ｒ²⁹、Ｒ³⁰、Ｒ³¹、Ｒ³²、Ｒ³³、Ｒ³⁴及びＲ³⁵はおのおの独立して炭素数１～１２のアルキル基、炭素数２～１２のアルケニル基、炭素数５～１２のシクロアルキル基、炭素数６～１２のアリール基又は炭素数７～１２のアラルキル基を表わす。）

Wherein R ²⁷ , R ²⁸ , R ²⁹ , R ³⁰ , R ³¹ , R ³² , R ³³ , R ³⁴ and R ³⁵ are each independently an alkyl group having 1 to 12 carbon atoms and 2 to 12 carbon atoms And alkenyl group, cycloalkyl group having 5 to 12 carbon atoms, aryl group having 6 to 12 carbon atoms or aralkyl group having 7 to 12 carbon atoms.

In the general formula (5), R ²⁷ , R ²⁸ , R ²⁹ , R ³⁰ , R ³¹ , R ³² , R ³³ , R ³⁴ and R ³⁵ (hereinafter also referred to as “R ²⁷ to R ³⁵ ”) are each independently And an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms. Examples of such groups include the groups exemplified as R ⁶ to R ¹⁰ in the general formula (1). As R ²⁷ to R ³⁵ , an alkyl group having 1 to 4 carbon atoms or a phenyl group is preferable because an industrial raw material can be easily obtained, a methyl group or a phenyl group is more preferable, and a methyl group is particularly preferable.

Among the compounds represented by the general formula (5), preferred compounds are tris (trimethylsilyl) borate, tris (dimethylphenylsilyl) borate, tris (methyldiphenylsilyl) borate, tris (triphenylsilyl) borate Etc.).

〔Organic solvent〕
As the organic solvent used for the non-aqueous electrolytic solution in the method for suppressing the decomposition of the silyl ester compound of the present invention, one or two or more in combination of those commonly used in non-aqueous electrolytic solutions can be used. Specifically, carbonate solvents, ester solvents, ether solvents, sulfoxide solvents and the like can be mentioned.

As carbonate solvents, saturated linear carbonate compounds such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl butyl carbonate, methyl-t-butyl carbonate, diisopropyl carbonate, t-butyl propyl carbonate, etc .; ethylene carbonate, 1-fluoroethylene Carbonate, 1,2-propylene carbonate, 1,3-propylene carbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, 1,1-dimethyl ethylene carbonate, 1,2-bis (methoxycarbonyloxy) ethane, And saturated cyclic carbonate compounds such as 1,2-bis (ethoxycarbonyloxy) ethane and 1,2-bis (ethoxycarbonyloxy) propane.

As ester solvents, saturated cyclic ester compounds such as γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-hexanolactone, δ-octanolactone; methyl formate, ethyl formate, methyl acetate, ethyl acetate, acetic acid Propyl, isobutyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, ethyl trimethylacetate, methyl malonate, methyl malonate, ethyl malonate, methyl succinate, ethyl succinate, 3-methoxy Examples thereof include saturated chain ester compounds such as methyl propionate, ethyl 3-methoxypropionate, ethylene glycol diacetyl, propylene glycol diacetyl and the like.

Examples of ether solvents include dimethoxyethane, ethoxymethoxyethane, diethoxyethane, ethylene glycol bis (trifluoroethyl) ether, propylene glycol bis (trifluoroethyl) ether, ethylene glycol bis (trifluoromethyl) ether, diethylene glycol bis ( Examples thereof include chain ether compounds such as trifluoroethyl) ether; cyclic ether compounds such as tetrahydrofuran, dioxolane and dioxane.

Examples of sulfoxide solvents include dimethyl sulfoxide, diethyl sulfoxide, dipropyl sulfoxide, diphenyl sulfoxide, thiophene and the like. As a sulfone type solvent, dimethyl sulfone, diethyl sulfone, dipropyl sulfone, diphenyl sulfone, sulfolane (also referred to as tetramethylene sulfone), 3-methylsulfolane, 3,4-dimethylsulfolane, 3,4-diphenymethylsulfolane, sulfolene And 3-methyl sulfolene, 3-ethyl sulfolene, 3-bromomethyl sulfolene and the like. Examples of amide solvents include N-methylpyrrolidone, dimethylformamide, dimethylacetamide and the like. In addition, acetonitrile, propionitrile, nitromethane and derivatives thereof can also be used as the organic solvent.

In the method for suppressing the decomposition of a silyl ester compound of the present invention, when the water content in the non-aqueous electrolytic solution is 1,000 ppm by mass or less, the decomposition of the silyl ester compound can be efficiently suppressed. When the water content is more than 1000 mass ppm, it becomes difficult to suppress the decomposition of the silyl ester compound. 500 mass ppm or less is preferable, and, as for the water content in a non-aqueous electrolyte, 300 mass ppm or less is still more preferable. The water content of the non-aqueous electrolyte can be measured by Karl Fischer titration or the like. In the measurement of the water content of the non-aqueous electrolytic solution, the non-aqueous electrolytic solution contains a lithium salt containing a fluorine atom, a silyl ester compound, an organic solvent, and a phenylsilane compound represented by the general formula (1) It may be at any time if it is.

Water in the non-aqueous electrolyte causes decomposition of the silyl ester compound, but water is mixed not only from the raw material of the non-aqueous electrolyte, but also at the time of production of the non-aqueous electrolyte or at the assembly of a battery . For this reason, in the case of producing a non-aqueous electrolytic solution, it is not sufficient to use only a raw material having a low water content, and it is produced under an inert gas atmosphere or under a low humidity atmosphere, etc. Is required. In addition, also at the time of assembling the battery, it is necessary to assemble in a low humidity atmosphere (for example, in a dry room), which requires a great deal of expense to obtain a low humidity atmosphere. According to the method for suppressing the decomposition of a silyl ester compound of the present invention, the cost required for dehydration treatment of a non-aqueous electrolyte and the cost required for a low humidity atmosphere can be reduced.
In order to set the water content in the non-aqueous electrolyte to 1000 ppm or less, the dried inert gas may be blown into the non-aqueous electrolyte as described in the examples to be described later. Nitrogen gas is mentioned as an inert gas.

In the method for suppressing the decomposition of a silyl ester compound of the present invention, decomposition of the silyl ester compound is likely to occur when the water content in the non-aqueous electrolytic solution is higher than a certain level. It becomes easy to do. Therefore, in the method for suppressing the decomposition of the silyl ester compound of the present invention, the water content of the non-aqueous electrolytic solution is preferably 5 mass ppm or more, more preferably 10 mass ppm or more, and still more preferably 20 mass ppm or more. In addition, in secondary batteries, such as a lithium ion secondary battery, in order to prevent the penetration | invasion of the water | moisture content from an exterior part to non-aqueous electrolyte, the lamination of a heat-fusion film and aluminum foil is used as an exterior member. However, the water can not be completely shut off, and the water may gradually intrude into the non-aqueous electrolyte from the exterior part. For this reason, even if the water content of the non-aqueous electrolyte of the assembled secondary battery is not immediately included to cause the decomposition of the silyl ester compound, the water content of the non-aqueous electrolyte is not It is preferable to blend 0.1 to 10% by mass of the phenylsilane compound represented by the general formula (1) into the water electrolyte.

The non-aqueous electrolyte according to the method for suppressing the decomposition of a silyl ester compound of the present invention can be suitably used for a conventionally known non-aqueous electrolyte secondary battery, particularly a lithium ion secondary battery.

The electrode material constituting the non-aqueous electrolyte secondary battery includes a positive electrode and a negative electrode, and as the positive electrode, a current collector obtained by slurrying a positive electrode active material, a binder and a conductive material with an organic solvent or water And dried to form a sheet.

As the positive electrode active material, in the case of a lithium ion secondary battery, for example, a known positive electrode active material capable of inserting and extracting lithium which is an electrode reactant can be used. Examples of known positive electrode active materials include lithium transition metal complex oxides, lithium-containing transition metal phosphate compounds, metal oxides, metal sulfides, metal halides, metal intercalation compounds, sulfur, and these are mixed. You may use it. As a transition metal of the lithium transition metal composite oxide, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper and the like are preferable. Specific examples of the lithium transition metal complex oxide include lithium cobalt complex oxide such as LiCoO ₂ , lithium nickel complex oxide such as LiNiO ₂ , lithium manganese complex oxide such as LiMnO ₂ , LiMn ₂ O ₄ and Li ₂ MnO ₃ And some of the transition metal atoms that are the main constituents of these lithium transition metal complex oxides, such as aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, lithium, nickel, copper, zinc, magnesium, gallium, zirconium, etc. What was substituted by the other metal etc. are mentioned. Specific examples of those substituted, for _{example, Li 1.1 Mn 1.8 Mg 0.1 O} 4, Li 1.1 Mn 1.85 Al 0.05 O 4, LiNi 0.5 Co 0.2 Mn 0.3 O 2, LiNi 0.8 Co 0.1 Mn 0.1 O 2, LiNi 0.5 Mn _0.5 O ₂ , LiNi _0.80 Co _0.17 Al _0.03 O ₂ , LiNi _0.80 Co _0.15 Al _0.05 O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiMn _1.8 Al _0.2 Examples include O ₄ , LiMn _1.5 Ni _0.5 O ₄ , Li ₂ MnO ₃ -LiMO ₂ (M = Co, Ni, Mn) and the like. As a transition metal of the lithium-containing transition metal phosphate compound, vanadium, titanium, manganese, iron, cobalt, nickel and the like are preferable, and specific examples thereof include iron phosphates such as LiFePO ₄ and phosphorus such as LiCoPO ₄ Acid cobalts and a part of transition metal atoms which are main components of these lithium transition metal phosphate compounds are aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, lithium, nickel, copper, zinc, magnesium, gallium, zirconium And those substituted with another metal such as niobium. The surface of the positive electrode active material may be coated with a conductive material described later, if necessary.

As a binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), Styrene-isoprene copolymer, polymethyl methacrylate, polyacrylate, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), methyl cellulose (MC), starch, polyvinyl pyrrolidone, polyethylene (PE), polypropylene (PP), polyethylene oxide (PEO And polyimide (PI), polyamide imide (PAI), polyacrylonitrile (PAN), polyvinyl chloride (PVC), polyacrylic acid, polyurethane and the like. The amount of the binder used is usually about 1 to 50% by mass, preferably 2 to 20% by mass, with respect to the positive electrode active material.

Examples of the conductive material include fine particles of graphite, natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon nanotubes, vapor grown carbon fibers, graphene, Carbon materials such as needle coke; metal powders such as aluminum powder, nickel powder and titanium powder; conductive metal oxides such as zinc oxide and titanium oxide; La ₂ S ₃ , Sm ₂ S ₃ , Ce ₂ S ₃ , TiS ₂ And sulfur-containing conductive materials, etc. The amount of the conductive material used is usually about 0.5 to 30% by mass, preferably 1 to 15% by mass, with respect to the positive electrode active material.

As a solvent for forming a slurry, an organic solvent or water that dissolves the binder is used. Examples of the organic solvent include N-methyl pyrrolidone, dimethylformamide, dimethyl acetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyl triamine, N-N-dimethylaminopropyl amine, ethylene oxide, tetrahydrofuran and the like. The amount of the solvent used is usually about 20 to 400% by mass, preferably 30 to 200% by mass, with respect to the positive electrode active material.

Usually, aluminum, stainless steel, nickel-plated steel or the like is used for the current collector of the positive electrode.

As the negative electrode, generally, a slurry obtained by slurrying a negative electrode active material, a binder and a conductive material with an organic solvent or water is coated on a current collector and dried to form a sheet.

As the negative electrode active material, carbonaceous materials, lithium, lithium alloy, silicon, silicon alloy, silicon oxide, tin, tin alloy, tin oxide, phosphorus, germanium, indium, copper oxide, copper sulfide, antimony sulfide, titanium oxide, iron oxide, oxide Other than manganese, cobalt oxide, nickel oxide, lead oxide, ruthenium oxide, tungsten oxide and zinc oxide, complex oxides such as LiVO ₂ , Li ₂ VO ₄ and Li ₄ Ti ₅ O ₁₂ , conductive polymers and the like can be mentioned. Such a carbonaceous material is not particularly limited, but natural graphite, artificial graphite, fullerene, graphene, graphite fiber chops, carbon nanotubes, graphite whiskers, crystalline carbon such as highly oriented pyrolytic graphite, kish graphite, and the like, non-graphite Carbon, graphitizable carbon, petroleum-based coke, coal-based coke, carbide of petroleum-based pitch, carbide of coal-based pitch, carbide of resin such as phenol resin / crystalline cellulose, etc., and carbon materials obtained by partially carbonizing these, There may be mentioned furnace black, acetylene black, pitch carbon fibers, PAN carbon fibers and the like.

Examples of the binder, the conductive material, and the solvent for forming a slurry include the same as those of the positive electrode. The amount of the binder used is usually about 0.1 to 30% by mass, preferably about 0.5 to 15% by mass, with respect to the negative electrode active material. The amount of the solvent used is usually about 25 to 400% by mass, preferably 30 to 200% by mass, based on the negative electrode active material.

Copper, nickel, stainless steel, nickel plated steel, etc. are usually used for the current collector of the negative electrode.

In the non-aqueous electrolyte secondary battery of the present invention, a separator is used between the positive electrode and the negative electrode. As the separator, a microporous film of a commonly used polymer can be used without particular limitation. Examples of the film include polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyethersulfone, polyether sulfone, polycarbonate, polyamide, polyimide, polyethylene oxide and polypropylene oxide, and the like. Polymers mainly composed of ethers, various celluloses such as carboxymethyl cellulose and hydroxypropyl cellulose, poly (meth) acrylic acid and its various esters and derivatives thereof, films comprising these copolymers and mixtures thereof Etc. These films may be used alone, or these films may be laminated and used as a multilayer film. Furthermore, various additives may be used in these films, and the type and content thereof are not particularly limited. Among these films, a film made of polyethylene, polypropylene, polyvinylidene fluoride or polysulfone is preferably used in the non-aqueous electrolyte secondary battery of the present invention. These films are micro-porous so that the electrolyte can penetrate and the ions can easily permeate. Moreover, you may coat with ceramics, such as an alumina and a silica, for safety improvement.

In the non-aqueous electrolyte secondary battery of the present invention, the electrode material, the non-aqueous electrolyte, and the separator have a phenol-based antioxidant, a phosphorus-based antioxidant, and a thioether-based antioxidant for the purpose of further improving safety. And hindered amine compounds may be added.

The shape of the non-aqueous electrolyte secondary battery of the present invention having the above-mentioned configuration is not particularly limited, and can be in various shapes such as coin, cylinder, square, laminate and the like. FIG. 1 shows an example of the coin-type battery of the non-aqueous electrolyte secondary battery of the present invention, and FIGS. 2 and 3 show an example of the cylindrical battery.

In the coin-type non-aqueous electrolyte secondary battery 10 shown in FIG. 1, 1 is a positive electrode capable of releasing lithium ions, 1a is a positive electrode current collector, and 2 is a carbonaceous material capable of absorbing and releasing lithium ions released from the positive electrode. A negative electrode 2a is a negative electrode current collector, 3 is a non-aqueous electrolyte of the present invention, 4 is a stainless steel positive electrode case, 5 is a stainless steel negative electrode case, 6 is a polypropylene gasket, and 7 is a polyethylene separator It is.

In the cylindrical non-aqueous electrolyte secondary battery 10 ′ shown in FIGS. 2 and 3, 11 is a negative electrode, 12 is a negative electrode current collector, 13 is a positive electrode, 14 is a positive electrode current collector, and 15 is the present invention. Nonaqueous electrolyte, 16 separator, 17 positive electrode terminal, 18 negative electrode terminal, 19 negative electrode, 20 negative electrode lead, 21 positive electrode, 22 positive electrode lead, 23 case, 24 insulating plate, 25 gasket Reference numeral 26 is a safety valve, and 27 is a PTC element.

Hereinafter, the present invention will be specifically described by way of examples and comparative examples, but these do not limit the scope of the present invention. In the examples, "parts" and "%" are by mass unless otherwise specified.
All operations according to the examples were performed in a dry room, and measurement of moisture was performed using a Karl Fischer moisture meter.

Electrolyte A: 0.8 mol / L of LiPF ₆ and 0 of LiN (SO ₂ CF ₃ ) ₂ in a mixed solvent consisting of 30% by volume of ethylene carbonate, 40% by volume of ethyl methyl carbonate, and 30% by volume of dimethyl carbonate Dissolved at a concentration of 2 mol / L. After this, in order to reduce the water content of the electrolyte, dry nitrogen gas is blown at 3 L / min for 24 hours through the glass capillary into the electrolyte at 20 ° C. according to the method described in WO 99/34471, and The electrolyte was heated to 70 ° C. and dry nitrogen gas was bubbled in at 3 L / min. The water content of the electrolyte solution A thus obtained was 1.3 mass ppm.

Electrolyte B: LiBF ₄ was dissolved in a mixed solvent consisting of 50% by volume of ethylene carbonate and 50% by volume of diethyl carbonate at a concentration of 1.0 mol / L to prepare an electrolyte solution. Thereafter, the same operation as in the electrolytic solution A was performed to obtain an electrolytic solution B. The water content of the electrolyte solution B was 1.8 mass ppm.

The following silicon compounds and silyl ester compounds are added to the electrolytic solution A or the electrolytic solution B according to the composition shown in Table 1, and the water content is adjusted to prepare the electrolytic solutions of Examples 1 to 25 and Comparative Examples 1 to 18. did. The adjustment of the water content was performed by combining the electrolyte solution in which the water content was reduced and the electrolyte solution before the water content was reduced.

<Silicon compound>
A1: trimethylphenylsilane A2: 1,4-bis (trimethylsilyl) benzene A3: dimethyldiphenylsilane A′1: triethylsilane A ′ 2: 1,1,3,3,3-hexamethyldisilazane A′3: dimethoxy Dimethylsilane <silyl ester compound>
B1: trimethylsilyl methacrylate B2: bis (trimethylsilyl) succinate
B3: Bis (trimethylsilyl) fumarate
B4: 2,2'-thiodiacetic acid bis (trimethylsilyl)
B5: bis (trimethylsilyl) 2,5-thiophenedicarboxylate
B6: Benzene-1,2,4-tricarboxylic acid tris (trimethylsilyl)
B7: Bis (trimethylsilyl) sulfate
B8: trimethylsilyl benzenesulfonate B9: tris (trimethylsilyl) phosphate
B10: Tris (trimethylsilyl) phosphite
B11: tris borate (trimethylsilyl)

Storage stability test
The storage stability of the electrolytic solution was evaluated by measuring the residual ratio of the silyl ester compound by the following method. The higher the residual rate, the higher the storage stability.
[Storage stability test method]
The above electrolyte was put in a container made of stainless steel under an argon atmosphere, sealed, and stored in a thermostat at 45 ° C. to obtain an electrolyte after storage for 3 weeks.
The electrolytic solution containing the phosphoric acid silyl ester compound or the phosphorous acid silyl ester compound is ³¹ P-NMR, and the electrolytic solution containing the carboxylic acid silyl ester compound, the sulfuric acid silyl ester compound and the sulfonic acid silyl ester compound is ¹ H-NMR The residual rate was calculated by measuring.
[Method by ³¹ P-NMR]
The ³¹ P-NMR is measured under the following conditions for an electrolytic solution to which triphenylphosphine is added as a reference substance, and the area of the peak derived from the phosphoric acid silyl ester compound or the phosphorous acid silyl ester compound relative to the area of the peak of the reference substance Find the ratio of The ratio (%) of the area of the peak after the storage test to the ratio of the area of the peak before the storage test was taken as the remaining rate.
Measurement device: Nuclear magnetic resonance device, model ECA-600, manufactured by JEOL Ltd.
Solvent: Heavy chloroform Reference substance: Triphenylphosphine (-6.0 ppm)
[Method by ¹ H-NMR]
The electrolytic solution is subjected to ¹ H-NMR measurement under the following conditions to determine the ratio of the area of the peak derived from the trimethylsilyl group of the silyl ester compound to the area of the ethylene carbonate peak of the solvent. The ratio (%) of the area of the peak after the storage test to the ratio of the area of the peak before the storage test was taken as the remaining rate.
Measurement system: Nuclear magnetic resonance system, model ECA-600, manufactured by Nippon Denshi Co., Ltd.
Solvent: Heavy chloroform Reference substance: Ethylene carbonate (4.58 ppm)
<Addition of test method>

[Charge and discharge cycle test]
In Examples and Comparative Examples, non-aqueous electrolyte secondary batteries (lithium ion secondary batteries) were manufactured according to the following preparation procedure.
[Production of positive electrode]
90 parts by mass of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM ₁₁₁ : manufactured by Nippon Chemical Industrial Co., Ltd.) as an active material, 5 parts by mass of acetylene black (AB: manufactured by Denka) as a conduction aid, and As an adhesive, 5 parts by mass of polyvinylidene fluoride (PVDF: manufactured by Kureha) was dispersed in 120 parts by mass of N-methyl-2-pyrrolidone (NMP) to form a slurry. The slurry was applied to a current collector made of aluminum, dried and press-molded. Thereafter, this electrode was cut into a predetermined size to prepare a disk-shaped positive electrode. The electrode capacity of this positive electrode was 2.5 mAh / cm ² .
[Fabrication of negative electrode]
96 parts by weight of artificial graphite (MAG: made by Hitachi Chemical) as an active material, 1 part by weight of acetylene black (AB: made by Denka) as a conductive additive, 40% by weight of water containing 1.5 parts by weight of SBR as a binder A dispersion (manufactured by Zeon Corporation) and 1.5 parts by mass of sodium carboxymethylcellulose (CMC: manufactured by Daicel Finechem) as a thickener were dispersed in 120 parts by mass of water to form a slurry. The slurry was applied to a copper current collector, dried and press-molded. Thereafter, this electrode was cut into a predetermined size to prepare a disk-shaped negative electrode. The electrode capacity of this negative electrode was 2.8 mAh / cm ² .
[Assembly of battery]
Using the obtained disk-shaped positive electrode and disk-shaped negative electrode, a 25 μm-thick polyethylene microporous film serving as a separator was sandwiched and held in a case. Thereafter, each non-aqueous electrolyte prepared above is poured into the case, the case is sealed and sealed, and the non-aqueous electrolyte secondary battery (φ 20 mm, thickness 3.2 mm coin) of the example and the comparative example Made a mold).
[Test method of charge and discharge cycle]
The non-aqueous electrolyte secondary battery is placed in a thermostatic chamber at 25 ° C., constant current charge is performed to 4.2 V with a charge current of 0.5 mA / cm ² (a current value corresponding to 0.2 C), and a discharge current of 0.5 mA An operation of performing constant current discharge to 3.0 V at a rate of 0.5 cm ² / cm ² (current value corresponding to 0.2 C) was performed five times. Then transferred to a thermostatic bath at 45 ° C., charging current 2.5 mA / cm ² constant current charging with (1C current value corresponding) to 4.2 V, the discharge current 2.5 mA / cm ² (1C equivalent current value The cycle operation of performing constant current discharge to 3.0 V was performed 100 times). As shown in the following formula, the discharge capacity retention rate (%) was determined as the ratio of the discharge capacity after the 100 cycle test when the initial discharge capacity at 1 C was 100.
Discharge capacity retention rate (%) = [(discharge capacity at 1st cycle (1C)) / (discharge capacity at 1st cycle (1C))] × 100

From the results of the storage stability test, in the electrolytic solution containing the phenylsilane compound represented by the general formula (1) of the present invention, the residual rate of the silyl ester compound is high, but the water content exceeds 1000 ppm in Comparative Examples 11 and 16 Then the survival rate is falling.
Comparing the storage stability test and the charge-discharge cycle test, in the battery using the electrolytic solution with a high residual ratio of silyl ester compound in the storage stability test, the discharge capacity retention ratio is high, and the silyl ester compound remains It can be seen that the discharge capacity is maintained as it is.

According to the present invention, in the non-aqueous electrolytic solution in which a lithium salt containing a fluorine atom and a silyl ester compound are dissolved in an organic solvent, the decomposition of the silyl ester compound is suppressed even when some water is present. It is possible to improve storage stability.

Claims (7)

It is selected from the group consisting of a lithium salt containing a fluorine atom, a carboxylic acid silyl ester compound, a sulfuric acid silyl ester compound, a sulfonic acid silyl ester compound, a phosphorous acid silyl ester compound, a phosphoric acid silyl ester compound and a boric acid silyl ester compound A method of suppressing the decomposition of a silyl ester compound in a non-aqueous electrolyte containing a silyl ester compound and an organic solvent,
The phenylsilane compound represented by the following general formula (1) is blended in an amount of 0.1 to 10% by mass in the non-aqueous electrolytic solution, and the water content of the non-aqueous electrolytic solution is 1,000 mass ppm or less And methods for suppressing the decomposition of silyl ester compounds.

(Wherein R ¹ , R ² , R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom, a halogen atom, a nitrile group, a nitro group, an alkyl group having 1 to 12 carbon atoms, or 2 to 12 carbon atoms) Alkenyl group, cycloalkyl group having 5 to 12 carbon atoms, aryl group having 6 to 12 carbon atoms, aralkyl group having 7 to 12 carbon atoms, oxyalkyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms -SiR ⁸ R ⁹ R ¹⁰ represents a group represented by R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ each independently being an alkyl group having 1 to 12 carbon atoms and alkenyl having 2 to 12 carbon atoms Group, a cycloalkyl group having 5 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms, X ¹ represents an m-valent hydrocarbon group, and m is 1 to 3 Represents a number) The lithium salt containing a fluorine atom is LiPF ₆ , LiBF ₄ , Li ₂ SiF ₆ , LiSbF ₆ , LiN (SO ₂ F) ₂ , LiOSO ₂ CF ₃ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ CF) _The method for suppressing the degradation of a silyl ester compound according to claim 1, wherein the method is one or more selected from the group consisting of ₂ CF ₃ ) ₂ . The method for suppressing decomposition of a silyl ester compound according to claim 1 or 2, wherein the carboxylic acid silyl ester compound is a compound represented by the following general formula (2).

(Wherein R ¹¹ , R ¹² and R ¹³ each independently represent an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or 6 to 12 carbon atoms Or an aralkyl group having 7 to 12 carbon atoms, X ² represents a direct bond or an n-valent group, and n represents a number of 1 to 4). The method for suppressing the decomposition of a silyl ester compound according to claim 1 or 2, wherein the silyl sulfate compound and the silyl ester compound of sulfonic acid are compounds represented by the following general formula (3).

(Wherein, R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ each independently represent an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or the like) Represents an aryl group of 6 to 12 or an aralkyl group having 7 to 12 carbon atoms, p represents a number of 0 or 1) The method for suppressing the decomposition of a silyl ester compound according to claim 1 or 2, wherein the phosphite silyl ester compound and the phosphate silyl ester compound are compounds represented by the following general formula (4).

(Wherein, R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ and R ²⁶ each independently represent an alkyl group having 1 to 12 carbon atoms and 2 to 12 carbon atoms And A represents an alkenyl group, a cycloalkyl group having 5 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms, and q represents a number of 0 or 1.) The method for suppressing the decomposition of a silyl ester compound according to claim 1 or 2, wherein the borate silyl ester compound is a compound represented by the following general formula (5).

Wherein R ²⁷ , R ²⁸ , R ²⁹ , R ³⁰ , R ³¹ , R ³² , R ³³ , R ³⁴ and R ³⁵ are each independently an alkyl group having 1 to 12 carbon atoms and 2 to 12 carbon atoms And alkenyl group, cycloalkyl group having 5 to 12 carbon atoms, aryl group having 6 to 12 carbon atoms or aralkyl group having 7 to 12 carbon atoms. The method for suppressing the decomposition of a silyl ester compound according to any one of claims 1 to 6, wherein the amount of water in the non-aqueous electrolytic solution is 5 mass ppm or more.

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