WO2019181704A1 - Thermal runaway suppression agent - Google Patents

Abstract

The present invention addresses the issue of providing a non-aqueous electrolyte secondary battery that has no thermal runaway if an internal short-circuit occurs and no risk of fire or explosion, without increasing size or greatly increasing cost. This agent for suppressing thermal runaway caused by internal short-circuits is for a non-aqueous electrolyte secondary battery having: a positive electrode including a positive electrode active substance comprising a silyl ester compound; a negative electrode including a negative electrode active substance, and a non-aqueous electrolyte. In this suppression method for thermal runaway caused by internal short-circuits in non-aqueous electrolyte secondary batteries, 0.01%–10% by mass of the agent for suppressing thermal runaway caused by internal short-circuits, for use in non-aqueous electrolyte secondary batteries, is mixed with the non-aqueous electrolyte.

Description

Thermal runaway inhibitor

The present invention relates to an inhibitor of thermal runaway due to an internal short circuit of a nonaqueous electrolyte secondary battery, and a method of suppressing thermal runaway due to an internal short circuit using the inhibitor.

Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are small and light, have high energy density, high capacity, and can be repeatedly charged and discharged, so portable PCs, handy video cameras, information terminals, etc. It is widely used as a power source for portable electronic devices. From the viewpoint of environmental problems, electric vehicles using non-aqueous electrolyte secondary batteries and hybrid vehicles using electric power as part of power have been put into practical use.

Non-aqueous electrolyte secondary batteries are composed of members such as electrodes, separators, and electrolytes. A flammable organic solvent is used as the main solvent for the electrolyte, and if a large amount of energy is released due to an internal short circuit, etc., thermal runaway occurs, and there is a risk of ignition or rupture. Countermeasures are being considered. As such countermeasures, a method using a porous film mainly composed of polyolefin as a separator (see, for example, Patent Documents 1 and 2), in addition to the separator, a porous heat-resistant layer is provided between the positive electrode and the negative electrode. A method of providing (for example, refer to Patent Document 3), a method of coating the surface of an electrode active material with a metal oxide (for example, refer to Patent Document 4), a method of using lithium-containing nickel oxide as a positive electrode active material (for example, Patent Document 5), a method using an olivine type lithium phosphate compound as a positive electrode active material (for example, refer to Patent Document 6), a method using a spinel lithium titanate compound as a negative electrode active material (for example, Patent Document 7) ), A method using a nonflammable fluorine-based solvent as the main solvent of the electrolyte (see, for example, Patent Documents 8 and 9), and a solid-state battery that does not use an organic solvent as the electrolyte. How to use the quality (e.g., see Patent Document 10) are known.

In order to prevent internal short circuit with a porous film separator mainly composed of polyolefin, it is necessary to increase the thickness of the separator. In the method of providing a porous heat-resistant layer, the battery becomes larger by the amount of the porous heat-resistant layer, and the electrode activity is increased. In the method of coating the surface of the material with a metal oxide, the content of the electrode active material contained in the electrode mixture layer of the electrode is relatively reduced, and the capacity of the battery is reduced. The advantage of the non-aqueous electrolyte secondary battery is lost. Neither a method using a lithium-containing nickel oxide or an olivine-type lithium phosphate compound as a positive electrode active material nor a method using a spinel lithium titanate compound as a negative electrode active material can provide a high charge / discharge capacity. In the method using a fluorinated solvent, the fluorinated solvent is very expensive and needs to be used in a large amount. In the method using a solid electrolyte, since a solid electrolyte material having no fluidity is used, the internal resistance is increased, and the performance is deteriorated as compared with an electrolyte using an organic solvent.

On the other hand, for example, in a lithium ion secondary battery, a non-aqueous electrolyte in which a lithium salt containing a fluorine atom such as lithium hexafluorophosphate is dissolved in a carbonate organic solvent such as propylene carbonate or diethyl carbonate as an electrolyte is used. Carboxylic acid silyl ester compounds (see, for example, Patent Documents 11 to 13), sulfuric acid silyl ester compounds (for example, see Patent Documents 4 to 5), sulfonic acid silyl ester compounds (For example, see Patent Documents 14 and 16), silyl compounds such as phosphoric acid silyl ester compounds (for example, see Patent Documents 15, 17, and 18), boric acid silyl ester compounds (for example, see Patent Documents 15 and 19), etc. Nonaqueous electrolytes to which an ester compound is further added have been studied. However, it is known that by using a non-aqueous electrolyte to which a silyl ester compound is added, even if an internal short circuit occurs, a thermal runaway is unlikely to occur, and a non-aqueous electrolyte secondary battery with no risk of ignition or rupture is obtained. Not.

US2018097256 US9923181 US7759004 JP 2011-216300 A JP 2002-015736 A US7572548 JP 2008-159280 A US2009253044 US8163422 US2016315324 JP 2002-313416 A US7410731 WO2016 / 013480 US7241536 JP 2006-253086 A US9112236 US6379846 JP 2004-342607 A US2002015585

An object of the present invention is to provide a non-aqueous electrolyte secondary battery that is less likely to cause thermal runaway and has no risk of ignition or rupture even if an internal short circuit occurs without increasing the size or significantly increasing the cost. is there.

As a result of intensive studies on the above problems, the present inventors have obtained a non-aqueous electrolyte secondary battery having a non-aqueous electrolyte using an organic solvent as a solvent, by blending a silyl ester compound into the non-aqueous electrolyte, The inventors have found that thermal runaway is unlikely to occur and that ignition or rupture due to an internal short circuit can be prevented, and the present invention has been completed. That is, the present invention is an inhibitor of thermal runaway due to an internal short circuit for a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a nonaqueous electrolyte secondary battery having a nonaqueous electrolyte, comprising a silyl ester compound. .

FIG. 1 is a longitudinal sectional view schematically showing an example of the structure of a coin-type battery of a nonaqueous electrolyte secondary battery. FIG. 2 is a schematic diagram showing a basic configuration of a cylindrical battery of a nonaqueous electrolyte secondary battery. FIG. 3 is a perspective view showing the internal structure of the cylindrical battery of the nonaqueous electrolyte secondary battery as a cross section.

The thermal runaway inhibitor of the present invention is characterized by comprising a silyl ester compound. Examples of silyl ester compounds include carboxylic acid silyl ester compounds, sulfuric acid silyl ester compounds, sulfonic acid silyl ester compounds, phosphoric acid silyl ester compounds, phosphorous acid silyl ester compounds, boric acid silyl ester compounds, and the like.

Examples of the carboxylic acid silyl ester compound include a carboxylic acid silyl ester compound represented by the following general formula (1).

（式中、Ｒ¹～Ｒ³は、それぞれ独立して炭素数１～６の炭化水素基を表し、Ｘ¹は炭素原子数１～１０のａ価の炭化水素基、又は炭化水素基中のメチレン基が酸素原子若しくは硫黄原子で置換された炭素原子数１～１０のａ価の基を表し、ａは１～４の数を表す。）

(Wherein R ¹ to R ³ each independently represents a hydrocarbon group having 1 to 6 carbon atoms, and X ¹ represents an a-valent hydrocarbon group having 1 to 10 carbon atoms, or a hydrocarbon group An a-valent group having 1 to 10 carbon atoms in which a methylene group is substituted with an oxygen atom or a sulfur atom, and a represents a number of 1 to 4)

In the general formula (1), R ¹ to R ³ each independently represents a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group having 1 to 6 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, and neopentyl. Group, 1-methylbutyl group, isohexyl group, vinyl group, cyclopentyl group, cyclohexyl group, phenyl group and the like. R ¹ to R ³ are preferably a methyl group, an ethyl group, or a phenyl group, and more preferably a methyl group, since the effect of suppressing thermal runaway is increased. R ¹ to R ³ may all be the same group or a combination of 2 to 3 groups, but in the case of a combination of 2 to 3 groups, one type is preferably a methyl group.

X ¹ represents an a-valent hydrocarbon group having 1 to 10 carbon atoms, or an a-valent group having 1 to 10 carbon atoms in which a methylene group in the hydrocarbon group is substituted with an oxygen atom or a sulfur atom, Represents a number from 1 to 4. If the carbon number of X ¹ is too large, the solubility in the non-aqueous electrolyte may decrease, or the effect of suppressing thermal runaway may be reduced. Therefore, the carbon number of X ¹ is preferably 1 to 10, 1 to 6 are more preferable. a is preferably a number of 2 to 3 from the viewpoint of the solubility of the carboxylic acid silyl ester compound in the non-aqueous electrolyte and the stability of the carboxylic acid silyl ester compound.

The carboxylic acid silyl ester compound represented by the general formula (1) can be obtained by silyl esterifying a carboxylic acid represented by the following general formula (1a) or an acid anhydride thereof by a known method.

（式中、Ｘ¹は一般式（１）と同義であり、ｍは１～４の数を表す。）

(Wherein X ¹ has the same meaning as in formula (1), and m represents a number of 1 to 4).

Among the carboxylic acid silyl ester compounds represented by the general formula (1), the compound in which a is 1 includes trimethylsilyl acetate, trimethylsilyl propanoate, trimethylsilyl butanoate, trimethylsilyl pentanoate, trimethylsilyl hexanoate, trimethylsilyl heptanoate, octanoic acid Trimethylsilyl, trimethylsilyl nonanoate, trimethylsilyl decanoate, trimethylsilyl 2-methylpropanoate, trimethylsilyl 2-methylbutanoate, trimethylsilyl 3-methylbutanoate, trimethylsilyl tert-butanoate, trimethylsilyl 2-methylpentanoate, trimethylsilyl 2-ethylbutanoate, isohexanoic acid Trimethylsilyl, trimethylsilyl 2-ethylhexanoate, trimethylsilyl isooctanoate, 3,5,5-trimethyl Trihexylsilyl hexanoate, trimethylsilyl acrylate, trimethylsilyl methacrylate, trimethylsilyl crotonate, trimethylsilyl benzoate, trimethylsilyl toluate, trimethylsilyl 4-tert-butylbenzoate, trimethylsilyl naphthalenecarboxylate, trimethylsilyl phenylacetate, trimethylsilyl naphthyl acetate, 4-methoxybenzoate Examples thereof include trimethylsilyl acid, trimethylsilyl methoxyacetate, trimethylsilyl ethoxyacetate, trimethylsilyl tert-butoxyacetate, and trimethylsilyl phenoxyacetate.

Among the carboxylic acid silyl ester compounds represented by the general formula (1), the compound in which a is 2 includes ethanedioic acid bis (trimethylsilyl), propanedioic acid bis (trimethylsilyl), butanedioic acid bis (trimethylsilyl), pentane. Diacid bis (trimethylsilyl), hexanedioic acid bis (trimethylsilyl), heptanedioic acid bis (trimethylsilyl), octanedioic acid bis (trimethylsilyl), nonanedioic acid bis (trimethylsilyl), decanedioic acid bis (trimethylsilyl), fumarate bis (Trimethylsilyl), bis (trimethylsilyl) maleate, bis (trimethylsilyl) citraconic acid, bis (trimethylsilyl) mesaconic acid, bis (trimethylsilyl) glutaconate, bis (trimethylsilyl) itaconate, bis (trimethylsilyl) muconate ), Acetylenedicarboxylic acid bis (trimethylsilyl), cyclohexanedicarboxylic acid bis (trimethylsilyl), cyclohexene dicarboxylic acid bis (trimethylsilyl), norbornanedicarboxylic acid bis (trimethylsilyl), norbornene dicarboxylic acid bis (trimethylsilyl), adamantanedicarboxylic acid bis (trimethylsilyl), Bicyclo [2.2.1] heptane-2,3-dicarboxylic acid bis (trimethylsilyl), bicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic acid bis (trimethylsilyl), benzenedicarboxylic acid bis (Trimethylsilyl), bis (trimethylsilyl) xylenedicarboxylate, bis (trimethylsilyl) furandcarboxylate, bis (trimethylsilyl) adamantanediacetate, B) Bis (trimethylsilyl) diacetate, (phenylenedioxy) bis (trimethylsilyl) diacetate, bis (trimethylsilyl) thiodiacetate, bis (trimethylsilyl) dithiodiacetate, bis (trimethylsilyl) propionate, bis (thiodipropionate) Trimethylsilyl), bis (trimethylsilyl) dithiodipropionate, bis (trimethylsilyl) ethylenedithiodiacetate, bis (trimethylsilyl) thiophenedicarboxylate, and the like.

Among the carboxylic acid silyl ester compounds represented by the general formula (1), the compound in which a is 3 includes propanetricarboxylic acid tris (trimethylsilyl), 3-carboxymuconic acid tris (trimethylsilyl), aconitic acid tris (trimethylsilyl), 3-Butene-1,2,3-tricarboxylic acid tris (trimethylsilyl), pentane-1,3,5-tricarboxylic acid tris (trimethylsilyl), hexane-1,3,6-tricarboxylic acid tris (trimethylsilyl), cyclohexanetricarboxylic acid Examples include tris (trimethylsilyl), trimellitic acid tris (trimethylsilyl), trimesic acid tris (trimethylsilyl), butanetetracarboxylic acid tris (trimethylsilyl), and the like.

Among the carboxylic acid silyl ester compounds represented by the general formula (1), compounds having a of 4 include cyclobutanetetracarboxylic acid tetrakis (trimethylsilyl), cyclopentanetetracarboxylic acid tetrakis (trimethylsilyl), tetrahydrofuran tetracarboxylic acid tetrakis ( Trimethylsilyl), pyromellitic acid tetrakis (trimethylsilyl), naphthalenetetracarboxylic acid tetrakis (trimethylsilyl) and the like.

Examples of the sulfuric acid silyl ester compound and the sulfonic acid silyl ester compound include compounds represented by the following general formula (3).

（式中、Ｒ¹¹～Ｒ¹⁴は、それぞれ独立して炭素数１～６の炭化水素基を表し、ｃは０又は１の数を表す。）

(Wherein R ¹¹ to R ¹⁴ each independently represents a hydrocarbon group having 1 to 6 carbon atoms, and c represents a number of 0 or 1).

In the general formula (3), R ¹¹ to R ¹⁴ each represent a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group having 1 to 6 carbon atoms include groups exemplified as R ¹ to R ³ in the general formula (1). R ¹¹ is preferably a methyl group or a phenyl group, and more preferably a methyl group, because industrial raw materials are easily available. R ¹² to R ¹⁴ are preferably a methyl group, an ethyl group, or a phenyl group, and more preferably a methyl group, since the effect of suppressing thermal runaway is increased.

c represents a number of 0 or 1, and when c is a number of 0, the compound represented by the general formula (3) is a sulfated silyl ester compound, and when c is a number of 1, sulfonic acid It is a silyl ester compound.

When c in formula (3) is a number of 0, that is, when the compound represented by formula (3) is a sulfated silyl ester compound, preferred compounds include bis (trimethylsilyl) sulfate and bis (dimethylphenylsulfate). Silyl), bis (methyldiphenylsilyl) sulfate, bis (triphenylsilyl) sulfate and the like.

When c 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 include trimethylsilyl methanesulfonate and dimethylphenyl methanesulfonate. Examples thereof include silyl, trimethylsilyl benzenesulfonate, and trimethylsilyl toluenesulfonate.

Examples of the phosphoric acid silyl ester compound include alkyl acid phosphoric acid ester silyl ester compounds in which a part of the silyl ester group is substituted with an alkyl ester group. The phosphorous acid silyl ester compound includes a part of the silyl ester group. Silyl ester compounds of alkyl acidic phosphites substituted with an alkyl ester group. As a phosphoric acid silyl ester compound and a phosphorous acid silyl ester compound, the compound represented by following General formula (4) is mentioned, for example.

（式中、Ｒ¹⁵～Ｒ¹⁸は、それぞれ独立して炭素数１～６の炭化水素基を表し、ｄは０又は１～２の数を表し、ｅは０又は１の数を表す。）

(Wherein R ¹⁵ to R ¹⁸ each independently represents a hydrocarbon group having 1 to 6 carbon atoms, d represents 0 or a number of 1 to 2, and e represents a number of 0 or 1).

In the general formula (4), R ¹⁵ to R ¹⁸ each independently represents a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group having 1 to 6 carbon atoms include groups exemplified as R ¹ to R ³ in the general formula (1). R ¹⁵ is preferably a methyl group, an ethyl group, or a butyl group, and more preferably a methyl group, since the effect of suppressing thermal runaway is increased. R ¹⁶ to R ¹⁸ are preferably a methyl group, an ethyl group, or a phenyl group, and more preferably a methyl group, since the effect of suppressing thermal runaway is increased.

D represents 0 or a number from 1 to 2, and e represents a number from 0 or 1. When d is a number from 1 to 2, a mixture of a compound having a number of 1 and a compound having a number of 2 can be used. When e is 1 and d is 0, the compound represented by the general formula (4) is a phosphoric acid silyl ester compound, and when e is 1 and d is 1 or 2 Is a silyl ester compound of an alkyl acidic phosphate. When e is a number of 0 and d is a number of 0, the compound represented by the general formula (4) is a phosphite silyl ester compound, wherein e is a number of 0 and d is a number of 1 to 2. In the case, it is an alkyl acidic phosphite silyl ester compound. The silyl ester compound of an alkyl acidic phosphate ester and the silyl ester compound of an alkyl acidic phosphite ester are easier to manufacture and storage stability than the silyl phosphate compound and the phosphite silyl ester compound, respectively. There is an advantage that it is excellent.

Examples of phosphoric acid silyl ester compounds (including silyl ester compounds of alkyl acidic phosphoric acid esters) include tris (trimethylsilyl) phosphate, methylbis (trimethylsilyl) phosphate, dimethyl (trimethylsilyl) phosphate, ethylbis (trimethylsilyl) phosphate, phosphorus Examples thereof include diethyl acid (trimethylsilyl), butylbisphosphate (trimethylsilyl), and dibutyl phosphate (trimethylsilyl). Phosphite silyl ester compounds (including silyl ester compounds of alkyl acid phosphites) include tris (trimethylsilyl) phosphite, methylbis (trimethylsilyl) phosphite, dimethyl phosphite (trimethylsilyl), phosphorous acid Examples thereof include ethyl bis (trimethylsilyl), diethyl phosphite (trimethylsilyl), butyl bisphosphite (trimethylsilyl), and dibutyl phosphite (trimethylsilyl).

Examples of the boric acid silyl ester compound include compounds represented by the following general formula (5).

（式中、Ｒ¹⁹～Ｒ²¹は、それぞれ独立して炭素数１～６の炭化水素基を表す。）

(In the formula, R ¹⁹ to R ²¹ each independently represents a hydrocarbon group having 1 to 6 carbon atoms.)

In the general formula (5), R ¹⁹ to R ²¹ each independently represents a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group having 1 to 6 carbon atoms include groups exemplified as R ¹ to R ³ in the general formula (1). R ¹⁹ to R ²¹ are preferably a methyl group, an ethyl group, or a phenyl group, and more preferably a methyl group, since the effect of suppressing thermal runaway is increased. Examples of the boric acid silyl ester compound include tris borate (trimethylsilyl).

In the present invention, since the effect of suppressing thermal runaway is high, it is preferable to use a carboxylic acid silyl ester compound represented by the general formula (1). Further, a in the general formula (1) is preferably 2, and X ¹ is a divalent hydrocarbon group having 1 to 10 carbon atoms, or a methylene group in the hydrocarbon group is an oxygen atom or a sulfur atom. It is preferably a substituted divalent group having 1 to 10 carbon atoms. In particular, R ¹ to R ³ in the general formula (1) are methyl groups, a is 2, and X ¹ is a divalent hydrocarbon group having 1 to 6 carbon atoms, or methylene in the hydrocarbon group A compound in which the group is a divalent group having 1 to 6 carbon atoms substituted with a sulfur atom is preferred.

In the present invention, a silyl ester compound is blended in the non-aqueous electrolyte as a thermal runaway inhibitor. The content of the silyl ester compound in the nonaqueous electrolyte is preferably 0.01% by mass to 10% by mass, more preferably 0.05% by mass to 7% by mass, and most preferably 0.1% by mass to 5% by mass. . When the content of the silyl ester compound in the non-aqueous electrolyte is too small, a sufficient effect of suppressing thermal runaway cannot be obtained, and when it is too large, the effect of increasing the amount corresponding to the blending amount cannot be obtained. The mechanism by which the silyl ester compound in the nonaqueous electrolyte suppresses thermal runaway due to an internal short circuit in the nonaqueous electrolyte secondary battery is not well understood, but siloxane compounds adhere to the positive and negative electrode surfaces of the nonaqueous electrolyte secondary battery. Therefore, it is presumed that the silyl ester compound is decomposed by the charge / discharge process to produce a siloxane compound on the electrode surface, which insulates the short-circuit current.

Examples of the nonaqueous electrolyte of the nonaqueous electrolyte secondary battery to which the present invention can be applied include a liquid electrolyte obtained by dissolving an electrolyte in an organic solvent, and a polymer gel electrolyte obtained by dissolving the electrolyte in an organic solvent and gelling with a polymer. In addition, a pure polymer electrolyte in which an organic solvent is not contained and an electrolyte is dispersed in a polymer can be used. Among them, in a nonaqueous electrolyte secondary battery having a liquid electrolyte, thermal runaway is likely to occur due to an internal short circuit, and there is a high risk of ignition or explosion. Therefore, the thermal runaway inhibitor of the present invention is a nonaqueous electrolyte having a liquid electrolyte. It is preferable to apply to a non-aqueous electrolyte of a secondary battery.

As the electrolyte used for the liquid electrolyte and the polymer gel electrolyte, a conventionally known electrolyte is used. Hereinafter, an electrolyte in the case where the nonaqueous electrolyte secondary battery is a lithium secondary battery will be described. In the case of a sodium secondary battery, an electrolyte in which lithium atoms are replaced with sodium atoms is used. Examples of the electrolyte used for the liquid electrolyte and the polymer gel electrolyte include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ). ₂ , LiN (SO ₂ F) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiB (CF ₃ SO ₃ ) ₄ , LiB (C ₂ O ₄ ) ₂ , LiBF ₂ (C ₂ O ₄ ), LiSbF ₆ , LiSiF ₅ , LiSCN, LiClO ₄ , LiCl, LiF, LiBr, LiI, LiAlF ₄ , LiAlCl ₄ , LiPO ₂ F ₂ and derivatives thereof, among these, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (SO ₂ F) ₂ , and LiC (CF ₃ SO ₂ ) _{3 and} Li It is preferable to use one or more selected from the group consisting of derivatives of CF ₃ SO ₃ and derivatives of LiC (CF ₃ SO ₂ ) ₃ . The electrolyte content in the liquid electrolyte and the polymer gel electrolyte is preferably 0.5 mol / L to 7 mol / L, more preferably 0.8 mol / L to 1.8 mol / L.

Examples of the electrolyte used for the pure polymer electrolyte include LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (SO ₂ F) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiB. (CF ₃ SO ₃ ) ₄ and LiB (C ₂ O ₄ ) ₂ may be mentioned.

As the organic solvent used for the preparation of the liquid non-aqueous electrolyte used in the present invention, those usually used for non-aqueous electrolytes can be used alone or in combination of two or more. Specific examples include saturated cyclic carbonate compounds, saturated cyclic ester compounds, sulfoxide compounds, sulfone compounds, amide compounds, saturated chain carbonate compounds, chain ether compounds, cyclic ether compounds, and saturated chain ester compounds. .

Among the organic solvents, saturated cyclic carbonate compounds, saturated cyclic ester compounds, sulfoxide compounds, sulfone compounds, and amide compounds are preferable because they have a high relative dielectric constant, and therefore play a role in increasing the dielectric constant of nonaqueous electrolytes. A carbonate compound is preferred. Examples of the saturated cyclic carbonate compound include ethylene carbonate, 1,2-propylene carbonate, 1,3-propylene carbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, 1,1-dimethylethylene carbonate, and the like. It is done. Examples of the saturated cyclic ester compound include γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-hexanolactone, and δ-octanolactone. Examples of the sulfoxide compound include dimethyl sulfoxide, diethyl sulfoxide, dipropyl sulfoxide, diphenyl sulfoxide, thiophene, and the like. Examples of the sulfone compound include dimethyl sulfone, diethyl sulfone, dipropyl sulfone, diphenyl sulfone, sulfolane (also referred to as tetramethylene sulfone), 3-methyl sulfolane, 3,4-dimethyl sulfolane, 3,4-diphenmethyl sulfolane. , Sulfolane, 3-methylsulfolene, 3-ethylsulfolene, 3-bromomethylsulfolene and the like, and sulfolane and tetramethylsulfolane are preferable. Examples of the amide compound include N-methylpyrrolidone, dimethylformamide, dimethylacetamide and the like.

Among the organic solvents, saturated chain carbonate compounds, chain ether compounds, cyclic ether compounds and saturated chain ester compounds can reduce the viscosity of the nonaqueous electrolyte and increase the mobility of electrolyte ions. Battery characteristics such as output density can be made excellent. Moreover, since it is low-viscosity, the performance of the nonaqueous electrolyte at low temperature can be enhanced, and therefore saturated chain carbonate compounds are particularly preferable. Examples of the saturated chain carbonate compound include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl butyl carbonate, methyl-t-butyl carbonate, diisopropyl carbonate, t-butyl propyl carbonate, and the like. Examples of the chain ether compound or the cyclic ether compound include dimethoxyethane, ethoxymethoxyethane, diethoxyethane, tetrahydrofuran, dioxolane, dioxane, 1,2-bis (methoxycarbonyloxy) ethane, 1,2-bis ( Ethoxycarbonyloxy) ethane, 1,2-bis (ethoxycarbonyloxy) propane, ethylene glycol bis (trifluoroethyl) ether, propylene glycol bis (trifluoroethyl) ether, ethylene glycol bis (trifluoromethyl) ether, diethylene glycol bis (Trifluoroethyl) ether and the like can be mentioned, and among these, dioxolane is preferable.

As the saturated chain ester compound, monoester compounds and diester compounds having a total number of carbon atoms in the molecule of 2 to 8 are preferable, and specific compounds include, for example, methyl formate, ethyl formate, methyl acetate, acetic acid Ethyl, propyl acetate, isobutyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethyl acetate, ethyl trimethyl acetate, methyl malonate, ethyl malonate, methyl succinate, ethyl succinate, Examples include methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethylene glycol diacetyl, propylene glycol diacetyl, and the like. Methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate, methyl propionate And ethyl propionate are preferred.

In addition, as the organic solvent used for preparing the non-aqueous electrolyte, for example, acetonitrile, propionitrile, nitromethane, derivatives thereof, and various ionic liquids can be used.

Examples of the polymer used in the polymer gel electrolyte include polyethylene oxide, polypropylene oxide, polyvinyl chloride, polyacrylonitrile, polymethyl methacrylate, polyethylene, polyvinylidene fluoride, and polyhexafluoropropylene. Examples of the polymer used in the pure polymer electrolyte include polyethylene oxide, polypropylene oxide, and polystyrene sulfonic acid. There is no restriction | limiting in particular about the compounding ratio in a gel electrolyte, and the compounding method, A compounding ratio well-known in this technical field and a well-known compounding method are employable.

The non-aqueous electrolyte preferably further contains a phenylsilane compound represented by the general formula (2) because the stability of the silyl ester compound is improved.

（式中、Ｒ⁴～Ｒ⁵は、それぞれ独立して炭素数１～６の炭化水素基を表し、Ｒ⁶～Ｒ¹⁰は、それぞれ独立して、水素原子、ハロゲン原子又は炭素数１～４のアルキル基を表し、Ｘ²はｂ価の炭化水素基を表し、ｂは１～３の数を表す。）

(Wherein R ⁴ to R ⁵ each independently represents a hydrocarbon group having 1 to 6 carbon atoms, and R ⁶ to R ¹⁰ each independently represents a hydrogen atom, a halogen atom, or a carbon number of 1 to 4). X ² represents a b-valent hydrocarbon group, and b represents a number of 1 to 3.)

In the general formula (2), R ⁴ to R ⁵ each independently represents a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group having 1 to 6 carbon atoms include groups exemplified as R ¹ to R ³ in the general formula (1). R ⁴ to R ⁵ are preferably a methyl group, an ethyl group, or a phenyl group, and more preferably a methyl group, since the effect of suppressing thermal runaway is increased.

R ⁶ to R ¹⁰ each independently represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and iodine. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a sec-butyl group, A tert-butyl group may be mentioned. R ⁶ to R ¹⁰ are preferably hydrogen atoms because the raw materials are easily industrially available.

X ² represents a b-valent hydrocarbon group, and b represents a number of 1 to 3. When the number of carbon atoms in X ² is too large, the solubility in the non-aqueous electrolyte is lowered, so that the number of carbon atoms in X ² is preferably 10 or less.

Among the phenylsilane compounds represented by the general formula (2), preferred compounds include trimethylphenylsilane, dimethyldiphenylsilane, methyltriphenylsilane, butyldimethylphenylsilane, dimethyloctylphenylsilane, 1,4-bis ( And trimethylsilyl) benzene, 1,2-bis (trimethylsilyl) benzene, 1,4-bis (dimethylphenylsilyl) benzene, 1,1,1-tris (dimethylphenylsilyl) ethane, and the like.

Some electrolytes used in non-aqueous electrolytes decompose to generate acidic substances. Such acidic substances can reduce the performance of non-aqueous electrolyte secondary batteries or decompose silyl ester compounds. May end up. The phenylsilane compound represented by the general formula (2) captures such an acidic substance, and suppresses the deterioration of the performance of the nonaqueous electrolyte secondary battery and the decomposition of the silyl ester compound. The amount of the phenylsilane compound represented by the general formula (2) added to the non-aqueous electrolyte is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 7% by mass, and more preferably 1% by mass to 5% by mass is most preferred. When the content in the non-aqueous electrolyte is too small, a sufficient effect cannot be exhibited. When the content is too large, the effect of increasing the amount corresponding to the amount added is not seen, and the battery performance may be deteriorated.

The nonaqueous electrolyte may contain an electrode film forming agent. Examples of the electrode film forming agent include cyclic carbonate compounds having an unsaturated group such as vinylene carbonate and vinyl ethylene carbonate; chain carbonate compounds having a propynyl group such as dipropargyl carbonate and propargylmethyl carbonate; dimethyl maleate, dibutyl maleate, Unsaturated diester compounds such as dimethyl fumarate, dibutyl fumarate, dimethyl acetylenedicarboxylate; halogenated cyclic carbonate compounds such as chloroethylene carbonate, dichloroethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate; cyclic sulfites such as ethylene sulfite; Examples thereof include cyclic sulfates such as propane sultone and butane sultone.

The electrode film forming agent forms a protective film called SEI (Solid Electrolyte Interface) on the electrode surface, and improves the charge / discharge efficiency, cycle characteristics, and safety of the battery. If the content of the electrode film forming agent is too small, it will not be able to exert a sufficient effect, and if it is too large, it will not be possible to obtain an increase effect commensurate with the content, but may have an adverse effect. Therefore, the content of the electrode film forming agent is preferably 0.005% by mass to 10% by mass, more preferably 0.02% by mass to 5% by mass in the non-aqueous electrolyte, and 0.05% by mass to 3% by mass. % Is most preferred.

The non-aqueous electrolyte may further contain other known additives such as an antioxidant, a flame retardant, and an overcharge inhibitor, for example, in order to improve battery life and safety.

A positive electrode including a positive electrode active material of a nonaqueous electrolyte secondary battery to which the present invention is applied is an electrode in which an electrode mixture layer including a positive electrode active material is formed on a current collector. A slurry obtained by slurrying a binder and a conductive additive with an organic solvent or water is applied to a current collector and dried to form a sheet.

As the positive electrode active material of the positive electrode, a known positive electrode active material can be used. Hereinafter, the electrolyte in the case where the nonaqueous electrolyte secondary battery is a lithium secondary battery will be described. In the case of a sodium secondary battery, a positive electrode active material in which lithium atoms are replaced with sodium atoms is used.

Known positive electrode active materials for lithium secondary batteries include, for example, lithium transition metal composite oxides, lithium-containing transition metal phosphate compounds, lithium-containing silicate compounds, lithium-containing transition metal sulfate compounds, sulfur, and sulfur-containing materials. Compounds and the like. The transition metal of the lithium transition metal composite oxide is preferably vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper or the like. Specific examples of the lithium transition metal composite oxide include lithium cobalt composite oxide such as LiCoO ₂ , lithium nickel composite oxide such as LiNiO ₂ , and lithium manganese composite oxide such as LiMnO ₂ , LiMn ₂ O ₄ , and Li ₂ MnO _3. Some of the transition metal atoms that are the main components of these lithium transition metal composite oxides are aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, lithium, nickel, copper, zinc, magnesium, gallium, zirconium, etc. The thing substituted with the other metal etc. are mentioned. Examples of lithium transition metal composite oxides in which some of the main transition metal atoms are substituted with other metals include 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 , Li (Ni _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 O 4, LiNi 0.5 Mn 1.5 O 4, Li 2 MnO 3 -LiMO 2 (M = Co, Ni, Mn) , and the like. As the transition metal of the lithium-containing transition metal phosphate compound, vanadium, titanium, manganese, iron, cobalt, nickel and the like are preferable, and specific examples include LiFePO ₄ , LiMn _x Fe _1-x PO ₄ (0 < Iron phosphate compounds such as x <1), cobalt phosphate compounds such as LiCoPO ₄ , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are aluminum, titanium, vanadium, chromium, manganese , Iron, cobalt, lithium, nickel, copper, zinc, magnesium, gallium, zirconium, niobium and other metal-substituted compounds, and Li ₃ V ₂ (PO ₄ ) ₃ vanadium phosphate compounds, etc. . Examples of the lithium-containing silicate compound include Li ₂ FeSiO ₄ . Examples of the lithium-containing transition metal sulfate compound include LiFeSO ₄ and LiFeSO ₄ F. These can use only 1 type and can also be used in combination of 2 or more type.

The thermal runaway inhibitor of the present invention can be suitably used for a nonaqueous electrolyte secondary battery having a large charge / discharge capacity. Examples of the positive electrode active material having a large charge / discharge capacity include LiCoO ₂ , LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O ₄ , Li (Ni _0.8 Co _0.15 Al _0.05 ) O ₂ , LiNi _X Co _Y Mn _Z O ₂ (X + Y + Z = 1, 0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ Z ≦ 1), LiNiO ₂ , Li ₂ MnO ₃ —LiMO ₂ (M = Co, Ni, Mn). The inhibitor can be suitably used for nonaqueous electrolyte secondary batteries having these positive electrode active materials.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), and styrene- Isoprene copolymer, polymethyl methacrylate, polyacrylate, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMCNa), methyl cellulose (MC), starch, polyvinyl pyrrolidone, polyethylene (PE), polypropylene (PP) , Polyethylene oxide (PEO), polyimide (PI), polyamideimide (PAI), polyacrylonitrile (PAN), polyvinyl chloride (PVC) Polyacrylic acid, and polyurethane. The amount of the binder used is usually about 1% by mass to 20% by mass, preferably 2% by mass to 10% by mass with respect to the positive electrode active material.

Examples of the conductive aid include carbon black, ketjen black, acetylene black, channel black, furnace black, lamp black, thermal black, carbon nanotube, vapor grown carbon fiber (VGCF), graphene, fullerene 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 and TiS _{2 and the} like. The average particle size of the conductive auxiliary agent is preferably 0.0001 μm to 100 μm, and more preferably 0.01 μm to 50 μm.

As the solvent to be slurried, an organic solvent or water that dissolves the binder is used. Examples of the organic solvent include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like. The amount of the solvent used is usually about 10% by mass to 400% by mass, preferably 20% by mass to 200% by mass with respect to the positive electrode active material.

As the positive electrode current collector, aluminum, stainless steel, nickel-plated steel or the like is usually used. Examples of the shape of the current collector include a foil shape, a plate shape, and a mesh shape, and a foil shape is preferable. In the case of a foil shape, the thickness of the foil is usually 1 μm to 100 μm.

The negative electrode including the negative electrode active material of the nonaqueous electrolyte secondary battery to which the present invention is applied is an electrode in which an electrode mixture layer including a negative electrode active material is formed on a current collector. A slurry obtained by slurrying a binder and a conductive additive with an organic solvent or water is applied to a current collector and dried to form a sheet.

As the negative electrode active material of the negative electrode, a known negative electrode active material can be used. Hereinafter, the electrolyte in the case where the nonaqueous electrolyte secondary battery is a lithium secondary battery will be described. In the case of a sodium secondary battery, the lithium atom of the negative electrode active material having a lithium atom among the negative electrode active materials is replaced by a sodium atom. The replaced negative electrode active material is used.

Known negative electrode active materials include carbonaceous materials, lithium, lithium alloys, silicon, silicon alloys, silicon oxide, tin, tin alloys, tin oxide, phosphorus, germanium, indium, copper oxide, antimony sulfide, titanium oxide, iron oxide , Manganese oxide, Cobalt oxide, Nickel oxide, Lead oxide, Ruthenium oxide, Tungsten oxide, Zinc oxide, LiVO ₂ , Li ₂ VO ₄ , Li ₄ Ti ₅ O _{12 and} other complex oxides, conductive polymer, sulfur modified Examples include polyacrylonitrile. The carbonaceous material is not particularly limited, however, natural graphite, artificial graphite, fullerene, graphene, graphite fiber chop, carbon nanotube, graphite whisker, highly oriented pyrolytic graphite, quiche graphite and other non-graphitizable carbon , Graphitizable carbon, petroleum coke, coal coke, petroleum pitch carbide, coal pitch carbide, phenolic resin, crystalline cellulose resin carbide, etc., and partially carbonized carbon materials, furnace black Acetylene black, pitch-based carbon fiber, polyacrylonitrile-based carbon fiber, and the like. When the positive electrode active material is sulfur-modified polyacrylonitrile, a negative electrode active material other than sulfur-modified polyacrylonitrile is used as the negative electrode active material.

Examples of the binder, the conductive additive, and the solvent to be slurried are the same as those for the positive electrode. The amount of the binder used is usually about 1% by mass to 30% by mass, preferably about 2% by mass to 15% by mass with respect to the negative electrode active material. The amount of the solvent used is usually about 10% by mass to 400% by mass, preferably 20% by mass to 200% by mass with respect to the negative electrode active material.

銅 Copper, nickel, stainless steel, nickel-plated steel, aluminum, etc. are usually used for the negative electrode current collector. Examples of the shape of the current collector include a foil shape, a plate shape, and a mesh shape, and a foil shape is preferable. In the case of a foil shape, the thickness of the foil is usually 1 μm to 100 μm.

In the non-aqueous electrolyte secondary battery to which the present invention is applied, a separator is used between the positive electrode and the negative electrode, and a commonly used polymer microporous film can be used without particular limitation. Examples of the film include polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyethersulfone, polycarbonate, polyamide, polyimide, polyethylene oxide, polypropylene oxide, and the like. , Various celluloses such as carboxymethyl cellulose and hydroxypropyl cellulose, polymer compounds mainly composed of poly (meth) acrylic acid and various esters thereof, derivatives thereof, films made of copolymers or mixtures thereof, etc. These films may be coated with ceramic materials such as alumina and silica, magnesium oxide, aramid resin, and polyvinylidene fluoride. That. When the nonaqueous solvent electrolyte is a pure polymer electrolyte, the separator may not be included.

The nonaqueous electrolyte secondary battery to which the present invention is applied is a single battery, a stacked battery in which a positive electrode and a negative electrode are laminated in multiple layers via a separator, a long sheet separator, a positive electrode and a negative electrode. Although any form such as a rechargeable battery may be used, the charge / discharge capacity of the battery is high, and thermal runaway due to an internal short circuit is likely to occur, so the present invention provides a stacked nonaqueous electrolyte secondary battery or a wound rechargeable battery. It is preferable to apply to a non-aqueous electrolyte secondary battery.

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 based on mass unless otherwise specified.

[Preparation of non-aqueous electrolyte A]
LiPF ₆ was dissolved in a mixed solvent composed of 50% by volume of ethylene carbonate and 50% by volume of diethyl carbonate to a concentration of 1.0 mol / L to obtain a nonaqueous electrolyte A.

[Preparation of non-aqueous electrolytes B to E]
The non-aqueous electrolytes A to G were obtained by dissolving the additives shown in Table 1 in the non-aqueous electrolyte A so as to have the indicated concentrations.

[Manufacture of positive electrode 1]
90.0 parts by mass of Li (Ni _1/3 Co _1/3 Mn _1/3 ) O ₂ (manufactured by Nippon Chemical Industry Co., Ltd., trade name: NCM111) as a positive electrode active material, 5.0 parts by mass of acetylene as a conductive auxiliary Black (manufactured by Denki Kagaku Kogyo), 5.0 parts by weight of polyvinylidene fluoride (manufactured by Kureha) as a binder were mixed with 90 parts by weight of N-methylpyrrolidone, and dispersed using a rotating / revolving mixer to prepare a slurry. . This slurry composition was continuously applied on both surfaces of a roll-shaped aluminum foil (thickness 20 μm) current collector by a comma coater method, and dried at 90 ° C. for 3 hours. This roll is cut into 50 mm length and 90 mm width, the electrode mixture layer on one side of the horizontal side (short side) is removed 10 mm from the end, the current collector is exposed, and then vacuum dried at 150 ° C. for 2 hours The positive electrode 1 was produced.

[Manufacture of positive electrode 2]
The procedure was the same as that for the production of the positive electrode 1 except that Li (Ni _0.8 Co _0.15 Al _0.05 ) O ₂ was used as the positive electrode active material instead of Li (Ni _1/3 Co _1/3 Mn _1/3 ) O _2. A positive electrode 2 using Li (Ni _0.8 Co _0.15 Al _0.05 ) O ₂ as a positive electrode active material was produced.

[Manufacture of negative electrode 1]
92.0 parts by mass of massive artificial graphite as an electrode active material, 3.5 parts by mass of acetylene black (manufactured by Denki Kagaku Kogyo) and 1.5 parts by mass of carbon nanotubes (VGCF: manufactured by Showa Denko) as a conductive auxiliary agent, As a binder, 1.5 parts by mass of styrene-butadiene rubber (aqueous dispersion, manufactured by Nippon Zeon Co., Ltd.) and 1.5 parts by mass of sodium carboxymethyl cellulose (manufactured by Daicel Finechem) are mixed with 100 parts by mass of water. A slurry was prepared by dispersing using a revolutionary mixer. This slurry composition was continuously applied on both sides of a roll-shaped copper foil (thickness 10 μm) current collector by a comma coater method, and dried at 90 ° C. for 3 hours. This roll is cut to 55 mm length and 95 mm width, the electrode mixture layer on one side of the horizontal side (short side) is removed 10 mm from the end, the current collector is exposed, and then vacuum dried at 150 ° C. for 2 hours The negative electrode 1 was produced.

[Manufacture of negative electrode 2]
As the electrode active material, in place of 92.0 parts by mass of massive artificial graphite, negative electrode 1 except that 87.0 parts by mass of massive artificial graphite and 5.0 parts by mass of silicon oxide (average particle diameter: 5 μm) were used. A negative electrode 2 was produced by the same procedure.

[Production of laminated laminate battery]
A positive electrode and a negative electrode are laminated via a separator (manufactured by Celgard, trade name: Cellguard 2325) so that the battery capacity shown in Table 2 is obtained, and a positive electrode terminal and a negative electrode terminal are provided on the positive electrode and the negative electrode, respectively, to obtain a laminate. It was. The obtained laminate and nonaqueous electrolytes A to G were accommodated in a flexible film, and laminated laminate batteries of Examples 1 to 8 and Comparative Examples 1 to 6 were obtained.

[Charging method]
In a thermostatic bath at 30 ° C., the charge end voltage was 4.2 V, the discharge end voltage was 2.75 V, and charge / discharge was performed once at a charge rate of 0.1 C and a discharge rate of 0.1 C, and degassing was performed. Furthermore, the charging / discharging cycle on the same conditions was performed 5 times, and it charged to 4.2V with the charging rate of 0.1 C, and used for the test.

[Negative stab test method]
The battery is fixed on a phenolic resin plate having a hole with a diameter of 10 mm, and an iron nail with a diameter of 3 mm and a length of 65 mm is pierced perpendicularly to the battery surface at a speed of 1 mm / s in the center of the hole. After passing through 10 mm and holding for 10 minutes, the nail was pulled out. Table 3 shows the surface temperature (° C.) of the battery 30 seconds after and 5 minutes after the nail is inserted just before the nail is inserted into the battery. In addition, the surface temperature of the battery measured the temperature of the battery surface 10 mm away from the nail penetration part using the thermocouple.

According to the present invention, a non-aqueous electrolyte that is small and lightweight, has a high capacity, is resistant to thermal runaway even when an internal short circuit occurs, and has no risk of ignition or rupture, without increasing the size or significantly increasing the cost. A secondary battery can be provided.

DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Positive electrode collector 2 Negative electrode 2a Negative electrode collector 3 Nonaqueous electrolyte 4 Positive electrode case 5 Negative electrode case 6 Gasket 7 Separator 10 Coin type nonaqueous electrolyte secondary battery 10 ′ Cylindrical nonaqueous electrolyte secondary battery 11 Negative electrode 12 Negative electrode current collector 13 Positive electrode 14 Positive electrode current collector 15 Nonaqueous electrolyte 16 Separator 17 Positive electrode terminal 18 Negative electrode terminal 19 Negative electrode plate 20 Negative electrode lead 21 Positive electrode plate 22 Positive electrode lead 23 Case 24 Insulating plate 25 Gasket 26 Safety valve 27 PTC element

Claims (6)

An inhibitor of thermal runaway due to an internal short circuit for a non-aqueous electrolyte secondary battery comprising a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte, comprising a silyl ester compound. The thermal runaway inhibitor according to claim 1, wherein the silyl ester compound is a carboxylic acid silyl ester compound represented by the following general formula (1).

(Wherein R ¹ to R ³ each independently represents a hydrocarbon group having 1 to 6 carbon atoms, and X ¹ represents an a-valent hydrocarbon group having 1 to 10 carbon atoms, or a hydrocarbon group An a-valent group having 1 to 10 carbon atoms in which a methylene group is substituted with an oxygen atom or a sulfur atom, and a represents a number of 1 to 4) A method for suppressing thermal runaway due to an internal short circuit of a nonaqueous electrolyte secondary battery, wherein the thermal runaway inhibitor according to claim 1 or 2 is blended in a nonaqueous electrolyte in an amount of 0.01 to 10 mass%. The method for suppressing thermal runaway due to an internal short circuit according to claim 3, wherein the non-aqueous electrolyte is a non-aqueous electrolyte using an organic solvent as a solvent. The method for suppressing thermal runaway due to an internal short circuit according to claim 3 or 4, wherein the non-aqueous electrolyte further contains a phenylsilane compound represented by the following general formula (2).

(Wherein R ⁴ to R ⁵ each independently represents a hydrocarbon group having 1 to 6 carbon atoms, and R ⁶ to R ¹⁰ each independently represents a hydrogen atom, a halogen atom, or a carbon number of 1 to 4). X ² represents a b-valent hydrocarbon group, and b represents a number of 1 to 3.) 6. The positive electrode active material according to claim 3, wherein the positive electrode active material is at least one selected from the group consisting of a lithium transition metal composite oxide, a lithium-containing transition metal phosphate compound, and a lithium-containing silicate compound. The method for suppressing thermal runaway due to the internal short circuit described.

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