JP5897869B2 - New fluorosilane compounds - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more specifically, a non-aqueous electrolyte secondary battery having a non-aqueous electrolyte containing a specific fluorosilane compound, and a novel novel suitable as an additive for the non-aqueous electrolyte The present invention relates to a fluorosilane compound.

  With the spread of portable electronic devices such as portable personal computers, handy video cameras, and information terminals in recent years, non-aqueous electrolyte secondary batteries having high voltage and high energy density have been widely used as power sources. Also, from the viewpoint of environmental problems, battery cars and hybrid cars using electric power as a part of power have been put into practical use.

  In non-aqueous electrolyte secondary batteries, various additives for non-aqueous electrolyte solutions have been proposed in order to improve the stability and electrical characteristics of non-aqueous electrolyte secondary batteries. Examples of such additives include 1,3-propane sultone (for example, see Patent Document 1), vinyl ethylene carbonate (for example, see Patent Document 2), vinylene carbonate (for example, see Patent Document 3), 1, 3-Propane sultone, butane sultone (for example, refer to Patent Document 4), vinylene carbonate (for example, refer to Patent Document 5), vinyl ethylene carbonate (for example, refer to Patent Document 6), and the like have been proposed. Carbonate is widely used because of its great effect. These additives form a stable film called SEI (Solid Electrolyte Interface) on the surface of the negative electrode, and this film covers the surface of the negative electrode, thereby suppressing reductive decomposition of the non-aqueous electrolyte. It is considered a thing.

In recent years, as the prices of rare metals such as cobalt and nickel have soared, the use and development of cathode agents using low-cost metal materials such as manganese and iron have rapidly spread. Among these, the transition metal oxide lithium-containing salt containing manganese is one of the positive electrode agents attracting attention because of its excellent performance in terms of capacity and output of the lithium secondary battery. However, in a lithium secondary battery using a transition metal oxide lithium-containing salt containing manganese as a positive electrode active material, manganese is easily eluted from the positive electrode, side reactions occur due to the eluted manganese, and the battery deteriorates. It has been found that capacity and output decrease.
As a method for suppressing elution of manganese from the positive electrode, various additives for non-aqueous electrolyte solutions have been proposed. As such additives, disulfonic acid esters and the like have been proposed (for example, Patent Document 7), but further improvement has been demanded.

JP 63-102173 A JP-A-4-87156 Japanese Patent Laid-Open No. 5-74486 Japanese Patent Laid-Open No. 10-50342 JP-A-8-045545 JP 2001-6729 A JP 2004-281368 A

  Accordingly, an object of the present invention is to suppress deterioration of a non-aqueous electrolyte secondary battery due to a transition metal eluted from the positive electrode in a non-aqueous electrolyte secondary battery using a positive electrode containing a transition metal and lithium, and store at high temperature. In other words, a small internal resistance and a high electric capacity can be maintained even after charging and discharging at high temperatures.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by using a nonaqueous electrolytic solution containing a fluorosilane compound having a specific structure, and completed the present invention.

That is, the present invention provides a non-aqueous electrolyte secondary battery having a negative electrode from which lithium can be inserted and removed, a positive electrode containing a transition metal and lithium, and a non-aqueous electrolyte in which a lithium salt is dissolved in an organic solvent.
A non-aqueous electrolyte secondary battery comprising a fluorosilane compound in which 3 to 14 hydrogen atoms of a hydrocarbon having 1 to 6 carbon atoms are substituted with an alkyldifluorosilyl group in the non-aqueous electrolyte. Is to provide.

（式中、Ｒ^1'は炭素原子数１〜８のアルキル基を表わし、ｎ’は３又は４の数を表す。） The present invention also provides a novel fluorosilane compound represented by the following general formula (1 ′).

(In the formula, R ^{1 ′} represents an alkyl group having 1 to 8 carbon atoms, and n ′ represents a number of 3 or 4.)

  According to the present invention, in a non-aqueous electrolyte secondary battery using a positive electrode containing a transition metal and lithium, a low internal resistance and a high electric capacity can be maintained even after high-temperature storage or high-temperature charge / discharge.

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

Hereinafter, the present invention will be described in detail based on preferred embodiments.
The present invention relates to a nonaqueous electrolyte secondary battery having a negative electrode from which lithium can be inserted and removed, a positive electrode containing a transition metal and lithium, and a nonaqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent. And a fluorosilane compound in which 3 to 14 hydrogen atoms of a hydrocarbon having 1 to 6 carbon atoms are substituted with an alkyldifluorosilyl group. First, the negative electrode from which lithium can be inserted and removed used in the present invention will be described.

  The negative electrode from which lithium can be inserted and removed used in the present invention is not particularly limited as long as lithium can be inserted and removed, but is preferably as follows. That is, in the present invention, as the negative electrode, a negative electrode active material, a binder or the like slurryed with an organic solvent or water is applied to a current collector and dried to form a sheet. As the negative electrode active material, graphite particles are preferably used. The raw material for the graphite particles may be natural graphite or artificial graphite. Natural graphite is an ore mined from nature such as natural graphite ore, and examples thereof include flaky graphite, scale graphite, and earth graphite. Artificial graphite is graphite obtained by firing a carbon-containing compound such as natural graphite, coal coke, non-graphitizable carbon, acetylene black, carbon fiber, petroleum coke, hydrocarbon solvent, needle coke, phenol resin, furan resin. Usually, these are used after being crushed.

Examples of the graphite used for the negative electrode active material include a coated crystalline carbon material whose surface is coated with amorphous carbon. However, as the graphite used in the present invention, the crystal surface is exposed on the surface. An uncoated crystalline carbon material is preferred. As a method for discriminating between the uncoated crystalline carbon material and the coated crystalline carbon material, a method by Raman spectroscopic measurement may be mentioned. When measuring the physical properties of the crystalline carbon material using a Raman spectroscopic measurement by an argon laser, the absorption peak near a wavelength of 1580 cm ^-1 is a peak due to the graphite structure, the absorption peak wavelength of around 1360 cm ^-1 is the graphite structure It is a peak resulting from disturbance. These peak ratios serve as indices indicating the degree of crystallization (graphitization) of the surface portion of the crystalline carbon material. In the present invention, an uncoated crystalline carbon material having a crystal face exposed on the surface means a peak intensity (I _D ) near 1360 cm ⁻¹ and 1580 cm in argon laser Raman spectroscopy measurement at a wavelength of 514.5 nanometers. The peak intensity (I _G ) ratio [I _G / I _D ] near ⁻¹ is 0.10 or less. In general, I _G / _ID of the coated crystalline carbon material used for the negative electrode is approximately 0.13 to 0.23.

Examples of the negative electrode binder (binder) include, but are not limited to, polyvinylidene fluoride, polytetrafluoroethylene, EPDM, SBR, NBR, fluororubber, and polyacrylic acid. The amount of the binder used for the negative electrode is preferably 0.001 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, and most preferably 0.01 to 2 parts by mass with respect to 100 parts by mass of the negative electrode active material. . Examples of the solvent for slurrying the negative electrode include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, polyethylene oxide, tetrahydrofuran and the like. However, it is not limited to these. The amount of the negative electrode solvent used is preferably from 30 to 300 parts by weight, more preferably from 50 to 200 parts by weight, based on 100 parts by weight of the negative electrode active material.
Moreover, copper, nickel, stainless steel, nickel-plated steel, etc. are normally used for the negative electrode current collector.

Next, the positive electrode containing a transition metal and lithium used in the present invention will be described. As a positive electrode used in the present invention, a positive electrode active material, a binder, a conductive material, etc., which are slurried with an organic solvent or water, are applied to a current collector and dried, as in a normal secondary battery. A sheet is used. In the present invention, the positive electrode active material contains a transition metal and lithium, and a material containing one kind of transition metal and lithium is preferable. For example, a lithium transition metal composite oxide, a lithium-containing transition metal phosphate compound These may be used, and these may be used in combination. As the 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 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. Specific examples of the substituted ones include, for example, LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.80 Co _0.17 Al _0.03 O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O ₄ or 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. Specific examples thereof include iron phosphates such as LiFePO ₄ and phosphorus such as LiCoPO _4. Cobalt acids, 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 And those substituted with other metals such as niobium.
As the positive electrode active material used for the positive electrode of the non-aqueous electrolyte secondary battery of the present invention, 3 to 14 hydrogen atoms of a hydrocarbon having 1 to 6 carbon atoms, which will be described later, were substituted with an alkyldifluorosilyl group. A lithium-containing metal oxide containing manganese is preferable because the effect of adding a fluorosilane compound is likely to occur. Among lithium-containing compounds containing manganese, since it has excellent performance as a positive electrode active material, Li _1.1 Mn _1.8 Mg _0.1 O ₄ , Li _1.1 Mn _1.85 Al _0.05 O ₄ , LiNi _1/3 Co _1/3 Mn _{1 / 5} O ₂ and LiNi _0.5 Co _0.2 Mn _0.3 O ₂ are preferred.

The binder for the positive electrode and the solvent for slurrying are the same as those used for the negative electrode. The amount of the binder used for the positive electrode is preferably 0.1 to 12 parts by mass, more preferably 0.5 to 8 parts by mass, and most preferably 1.0 to 6 parts by mass with respect to 100 parts by mass of the positive electrode active material. . 30-300 mass parts is preferable with respect to 100 mass parts of positive electrode active materials, and, as for the usage-amount of the solvent of a positive electrode, 50-200 mass parts is still more preferable.
Examples of the conductive material for the positive electrode include graphite fine particles, carbon black such as acetylene black and ketjen black, amorphous carbon fine particles such as needle coke, and the like, but are not limited thereto. 0.01-20 mass parts is preferable with respect to 100 mass parts of positive electrode active materials, and, as for the usage-amount of the electrically conductive material of a positive electrode, 0.1-10 mass parts is still more preferable.
As the positive electrode current collector, aluminum, stainless steel, nickel-plated steel or the like is usually used.

Next, a nonaqueous electrolytic solution in which the lithium salt used in the present invention is dissolved in an organic solvent (hereinafter also referred to as the nonaqueous electrolytic solution of the present invention) will be described. The nonaqueous electrolytic solution of the present invention contains a fluorosilane compound in which 3 to 14 hydrogen atoms of a hydrocarbon having 1 to 6 carbon atoms are substituted with an alkyldifluorosilyl group. Hereinafter, this fluorosilane compound will be described.
Examples of the hydrocarbon having 1 to 6 carbon atoms include aliphatic hydrocarbons or aromatic hydrocarbons composed of only carbon atoms having 1 to 6 carbon atoms and hydrogen atoms. The number of alkyldifluorosilyl groups substituting the hydrocarbon is 3 to 14, preferably 3 to 10, and more preferably 3 to 6. In addition, as the alkyldifluorosilyl group, difluoro ( methyl ) silyl group, difluoro ( ethyl ) silyl group, difluoro ( propyl ) silyl group, difluoro ( butyl ) silyl group, difluoro ( pentyl ) silyl group, difluoro ( hexyl ) silyl group , Difluoro ( heptyl ) silyl group, difluoro ( octyl ) silyl group and the like. 3 to 14 alkyldifluorosilyl groups may be the same or different from each other, but are preferably the same from the viewpoint of easy production.

Specific examples of the fluorosilane compound having three or more alkyldifluorosilyl groups include 1,1,2,2-tetrakis [ difluoro ( methyl ) silyl ] ethane, 1,1,1,2-tetrakis [ difluoro ( Methyl ) silyl ] ethane, 1,3,6-tris [ difluoro ( methyl ) silyl ] hexane, 1,3,5-tris [ difluoro ( methyl ) silyl ] benzene, 1,2,3-tris [ difluoro ( methyl ) Silyl ] benzene, 1,2,4-tris [ difluoro ( methyl ) silyl ] benzene, 1,2,4,5-tetrakis [ difluoro ( methyl ) silyl ] benzene, 1,2,3,4-tetrakis [ difluoro ( Methyl ) silyl ] benzene or a fluorosilane compound represented by the following general formula (1).

  Among the fluorosilane compounds having three or more alkyldifluorosilyl groups, the fluorosilane compound represented by the following general formula (1) is preferable because the raw materials are easily available.

（式中、Ｒ¹は炭素原子数１〜８のアルキル基を表わし、ｎは３又は４の数を表す。）

(In the formula, R ¹ represents an alkyl group having 1 to 8 carbon atoms, and n represents a number of 3 or 4.)

In the general formula (1), R ¹ represents an alkyl group having 1 to 8 carbon atoms, such as methyl, ethyl, propyl, 2-propynyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, isopentyl, Examples include cyclopentyl, hexyl, cyclohexyl, heptyl, octyl and the like. Of these, methyl and ethyl are preferable, and methyl is most preferable because it has little adverse effect on the movement of lithium ions and good charge characteristics.

Specific examples of the fluorosilane compound represented by the general formula (1) include, for example, tris [ difluoro ( methyl ) silyl ] methane, tris [ difluoro ( ethyl ) silyl ] methane, and tris [ difluoro ( propyl ) silyl ] methane. , Tris [ difluoro ( butyl ) silyl ] methane, tris [ difluoro ( pentyl ) silyl ] methane, tris [ difluoro ( hexyl ) silyl ] methane, tris [ difluoro ( heptyl ) silyl ] methane, tris [ difluoro ( octyl ) silyl ] methane , tetrakis [difluoro (methyl) silyl] methane, tetrakis [difluoro (ethyl) silyl] methane, tetrakis [difluoro (propyl) silyl] methane, tetrakis [difluoro (butyl) silyl] methane, tetrakis [difluoro (pentyl) Siri ] Methane, tetrakis [difluoro (hexyl) silyl] methane, tetrakis [difluoro (heptyl) silyl] methane, tetrakis [difluoro (octyl) silyl] methane, and the like.

In the nonaqueous electrolytic solution of the present invention, only one kind of fluorosilane compound in which 3 to 14 hydrogen atoms of the hydrocarbon having 1 to 6 carbon atoms are substituted with an alkyldifluorosilyl group may be used. Two or more kinds may be used in combination.
In the non-aqueous electrolyte of the present invention, when the content of the fluorosilane compound in which 3 to 14 hydrogen atoms of a hydrocarbon having 1 to 6 carbon atoms is substituted with an alkyldifluorosilyl group is too small, a sufficient effect is obtained. If the amount of the fluorosilane compound is too large, not only the increase effect corresponding to the blending amount is not obtained, but the properties of the nonaqueous electrolyte may be adversely affected. In the water electrolyte, 0.001 to 5 mass% is preferable, 0.01 to 3 mass% is more preferable, and 0.03 to 1.5 mass% is most preferable.

  The nonaqueous electrolytic solution of the present invention further includes an additive such as a cyclic carbonate compound having an unsaturated group, a chain carbonate compound, an unsaturated diester compound, a cyclic sulfate, a cyclic sulfite, a sultone, or a halogenated cyclic carbonate compound. It is preferable to contain.

  Examples of the cyclic carbonate compound having an unsaturated group include vinylene carbonate, vinyl ethylene carbonate, propylidene carbonate, ethylene ethylidene carbonate, ethylene isopropylidene carbonate, vinylene carbonate and vinyl ethylene carbonate are preferred, and the above chain carbonate Examples of the compound include dipropargyl carbonate, propargyl methyl carbonate, ethyl propargyl carbonate, bis (1-methylpropargyl) carbonate, bis (1-dimethylpropargyl) carbonate, and the like. Examples of the unsaturated diester compounds include dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dipentyl maleate, dihexyl maleate, diheptyl maleate, dioctyl maleate, dimethyl fumarate, diethyl fumarate, and fumaric acid. Dipropyl, dibutyl fumarate, dipentyl fumarate, dihexyl fumarate, diheptyl fumarate, dioctyl fumarate, dimethyl acetylenedicarboxylate, diethyl acetylenedicarboxylate, dipropyl acetylenedicarboxylate, dibutyl acetylenedicarboxylate, dipentyl acetylenedicarboxylate, acetylenedicarboxylic acid Examples include dihexyl, diheptyl acetylenedicarboxylate, dioctyl acetylenedicarboxylate, and the above cyclic sulfates. 1,3,2-dioxathiolane-2,2-dioxide, 1,3-propanediol cyclic sulfate, propane-1,2-cyclic sulfate and the like. Examples of the cyclic sulfite ester include ethylene sulfite. And propylene sulfite. Examples of the sultone include propane sultone, butane sultone, 1,5,2,4-dioxadithiolane-2,2,4,4-tetraoxide, and the like. Examples of the halogenated cyclic carbonate compound include chloroethylene carbonate, dichloroethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and the like. Among these additives, vinylene carbonate, vinyl ethylene carbonate, dipropargyl carbonate, dimethyl acetylenedicarboxylate, diethyl acetylenedicarboxylate, propane sultone, butane sultone, chloroethylene carbonate, dichloroethylene carbonate, and fluoroethylene carbonate are preferable, vinylene carbonate, diethylene carbonate, Propargyl carbonate, dimethyl acetylenedicarboxylate, propane sultone, and fluoroethylene carbonate are more preferable, and vinylene carbonate, dipropargyl carbonate, propane sultone, and fluoroethylene carbonate are most preferable.

  These additives may be used alone or in combination of two or more. In the non-aqueous electrolyte of the present invention, when the content of these additives is too small, a sufficient effect cannot be exhibited, and when the content is too large, an increase effect corresponding to the blending amount cannot be obtained. However, since the properties of the non-aqueous electrolyte may be adversely affected, the total content of these additives is preferably 0.005 to 10% by mass in the non-aqueous electrolyte, and 0.02 to 5%. % By mass is more preferable, and 0.05 to 3% by mass is most preferable.

  As an organic solvent used with the non-aqueous electrolyte of this invention, what is normally used for the non-aqueous electrolyte can be used 1 type or in combination of 2 or more types. Specific examples include saturated cyclic carbonate compounds, saturated cyclic ester compounds, sulfoxide compounds, sulfone compounds, amide compounds, saturated chain carbonate compounds, saturated chain ether compounds, cyclic ether compounds, and saturated chain ester compounds.

Among the above organic solvents, saturated cyclic carbonate compounds, saturated cyclic ester compounds, sulfoxide compounds, sulfone compounds and amide compounds have a high relative dielectric constant, and thus serve to increase the dielectric constant of the electrolyte. Is preferred. Examples of such saturated cyclic carbonate compounds include ethylene carbonate, 1,2-propylene carbonate, 1,3-propylene carbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, 1,1, -dimethylethylene carbonate. Etc. 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 compounds 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-diphenimethyl sulfolane, sulfolene. , 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 above organic solvents, saturated chain carbonate compounds, chain ether compounds, cyclic ether compounds and saturated chain ester compounds can lower the viscosity of the non-aqueous 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 solution for batteries at low temperatures can be enhanced, and among these, saturated chain carbonate compounds are preferred. Examples of such saturated chain carbonate compounds include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethyl butyl carbonate, methyl-t-butyl carbonate, diisopropyl carbonate, and t-butyl propyl carbonate. Etc. Examples of the chain ether or cyclic ether compound include dimethoxyethane (DME), 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, Examples include diethylene glycol bis (trifluoroethyl) ether, and among these, dioxolane is preferable.
As the saturated chain ester compound, monoester compounds and diester compounds having a total of 2 to 8 carbon atoms in the molecule are preferable, and specific compounds include methyl formate, ethyl formate, methyl acetate, and ethyl acetate. , 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, 3 -Methyl 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, as well as Propionic acid ethyl are preferred.

  In addition, acetonitrile, propionitrile, nitromethane, and derivatives thereof can also be used as the organic solvent.

As the lithium salt used in the non-aqueous electrolyte of the present invention, a conventionally known lithium salt is used. For example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiN (CF _{3 SO 2) 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, LiAlF 4, Examples include LiSCN, LiClO ₄ , LiCl, LiF, LiBr, LiI, LiAlF ₄ , LiAlCl ₄ , and derivatives thereof. Among these, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , and derivatives of LiC (CF ₃ SO _{2) 3} and LiCF ₃ SO _3, and LiC the (CF ₃ SO ₂₎ 1 or more selected from the group consisting of ₃ derivatives Are the are preferred because of excellent electrical characteristics.

  The lithium salt can be dissolved in the organic solvent so that the concentration in the non-aqueous electrolyte of the present invention is 0.1 to 3.0 mol / L, particularly 0.5 to 2.0 mol / L. preferable. If the concentration of the lithium salt is less than 0.1 mol / L, a sufficient current density may not be obtained, and if it is more than 3.0 mol / L, the stability of the nonaqueous electrolyte may be impaired.

  In addition, halogen-based, phosphorus-based, and other flame retardants can be appropriately added to the nonaqueous electrolytic solution of the present invention in order to impart flame retardancy. If the amount of flame retardant added is too small, sufficient flame retarding effect cannot be achieved, and if it is too large, an increase effect corresponding to the blending amount cannot be obtained. Since the properties may be adversely affected, the content is preferably 5 to 100% by mass, and more preferably 10 to 50% by mass with respect to the organic solvent constituting the nonaqueous electrolytic solution of the present invention.

  In the non-aqueous electrolyte secondary battery of the present invention, it is preferable to use a separator between the positive electrode and the negative electrode. As the separator, a commonly used polymer microporous film can be used without any particular limitation. Examples of the film include polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyethersulfone, polycarbonate, polyamide, polyimide, polyethylene oxide and polypropylene oxide. Films composed of ethers, various celluloses such as carboxymethylcellulose and hydroxypropylcellulose, polymer compounds mainly composed of poly (meth) acrylic acid and various esters thereof, derivatives thereof, copolymers and mixtures thereof. Etc. These films may be used alone, or may be used as a multilayer film by superimposing these films. Furthermore, various additives may be used for 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 for the nonaqueous electrolyte secondary battery of the present invention.

  These films are microporous so that the electrolyte can penetrate and ions can easily pass therethrough. The microporosity method includes a phase separation method in which a polymer compound and a solvent solution are formed into a film while microphase separation is performed, and the solvent is extracted and removed to make it porous. The film is extruded and then heat-treated, the crystals are aligned in one direction, and a gap is formed between the crystals by stretching to make it porous, and so on.

  In the non-aqueous electrolyte secondary battery of the present invention, the electrode material, the non-aqueous electrolyte, and the separator include a phenol-based antioxidant, a phosphorus-based antioxidant, and a thioether-based antioxidant for the purpose of improving safety. A hindered amine compound or the like may be added.

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

  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 inserting and extracting lithium ions released from the positive electrode. The negative electrode current collector, 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.

  Further, in the cylindrical nonaqueous 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 is a separator, 17 is a positive electrode terminal, 18 is a negative electrode terminal, 19 is a negative electrode plate, 20 is a negative electrode lead, 21 is a positive electrode plate, 22 is a positive electrode lead, 23 is a case, 24 is an insulating plate, 25 is A gasket, 26 is a safety valve, and 27 is a PTC element.

Next, the novel compound of the present invention will be described. In addition, about the point which is not demonstrated especially, the description in the fluorosilane compound represented by the said General formula (1) is applied suitably.
The novel compound of the present invention is represented by the above general formula (1 ′).
Examples of the group represented by 'R ¹ in the general formula ^(1)' include the same groups as R ¹ in the general formula (1).

  The production method of the novel compound of the present invention is not particularly limited. For example, the coupling reaction of halogenated hydrocarbon and chlorosilane with magnesium described in Journal of American Chemical Society, 85, 2243 (1963). It can be produced by fluorinating the produced chlorosilane compound.

  As described above, the novel compound of the present invention is used as an additive for non-aqueous electrolytes used in non-aqueous electrolyte secondary batteries, as well as protective group raw materials for organic and inorganic compounds, CVD (chemical vapor deposition). It is also used as a raw material gas.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited by the following examples. In the examples, “parts” and “%” are based on mass unless otherwise specified.

  The following Production Examples 1 and 2 are synthesis examples of the fluorosilane compound represented by the general formula (1 ′) of the present invention, and the following Production Example 3 is a synthesis example of VEMALi used as a thickener in the negative electrode. The following Examples 1 to 10 and Comparative Examples 1 to 8 are examples of the nonaqueous electrolyte secondary battery of the present invention and comparative examples thereof.

[Production Example 1] Synthesis of tris [ difluoro ( methyl ) silyl ] methane (Compound A1) Into a 200 ml three-necked flask equipped with a reflux condenser, 9.0 g of magnesium was charged and stirred while flowing nitrogen to activate the magnesium. Turned into. After adding 50.0 g of methyldichlorosilane and 100 ml of tetrahydrofuran, 25 g of bromoform was added dropwise over 30 minutes under water cooling. After completion of the dropping, heating was continued for 3 hours in an oil bath at 50 ° C. after the exotherm subsided. After returning to room temperature and adding 50 ml of hexane, the generated magnesium salt was removed by filtration, and the filtrate was distilled to obtain 16.5 g of tris [ chloro ( methyl ) silyl ] methane.
12.0 g of tris [ chloro ( methyl ) silyl ] methane and 18.0 g of cyclopentane were charged into a 100 ml PFA Erlenmeyer flask, and 27.1 g of 23% aqueous hydrogen fluoride was added dropwise over 20 minutes under ice cooling. Stirring was further continued for 10 hours under ice cooling, and the generated crystals were separated by filtration. The obtained crystal was dissolved in heated hexane, and the hexane solution was decanted to remove water adhering to the crystal. Crystals are precipitated by cooling the hexane solution, and the generated crystals are separated by filtration and dried to obtain 5.2 g of needle-like crystals of tris [ difluoro ( methyl ) silyl ] methane (compound A1) as the target product. Obtained. Hereinafter, the spectrum data ( ¹ H-NMR and GC-MS) of Compound A1 are shown.
¹ H-NMR: 0.48-0.58 ppm (Multiplicity: m, number of protons: 10H, measurement solvent: CDCl ₃ )
GC-MS (m / z): 256, 241, 137, 91, 47

[Production Example 2] Synthesis of tetrakis [ difluoro ( methyl ) silyl ] methane (Compound A2) 8.5 g of magnesium was charged into a 200 ml three-necked flask equipped with a refluxer and stirred while flowing nitrogen to activate the magnesium. Turned into. After adding 50.0 g of methyldichlorosilane and 50 ml of tetrahydrofuran, a solution of 25 g of tetrabromomethane and 50 ml of tetrahydrofuran was added dropwise over 30 minutes under water cooling. After completion of the dropping, heating was continued for 4 hours in an oil bath at 50 ° C. after the exotherm settled. After returning to room temperature and adding 50 ml of hexane, the generated magnesium salt was removed by filtration, and the filtrate was distilled to obtain 12.4 g of tetrakis [ chloro ( methyl ) silyl ] methane.
12.0 g of tetrakis [ chloro ( methyl ) silyl ] methane and 18.0 g of cyclopentane were charged into a 100 ml PFA Erlenmeyer flask, and 32.4 g of 23% aqueous hydrogen fluoride was added dropwise over 20 minutes under ice cooling. Stirring was further continued for 10 hours under ice cooling, and the generated crystals were separated by filtration. The obtained crystal was dissolved in heated hexane, and the hexane solution was decanted to remove water adhering to the crystal. Crystals are precipitated by cooling the hexane solution, and the generated crystals are separated by filtration and dried to obtain 4.8 g of needle-like crystals of tetrakis [ difluoro ( methyl ) silyl ] methane (compound A2) as the target product. Obtained. Hereinafter, the spectrum data ( ¹ H-NMR and GC-MS) of Compound A2 are shown.
¹ H-NMR: 0.55 ppm (proton number: 12H, measurement solvent: CDCl ₃ )
GC-MS (m / z): 336, 321, 217, 91, 47

[Production Example 3] Synthesis of VEMALi (thickening agent) 80.0 g of a methyl vinyl ether / maleic anhydride copolymer (VEMA) having a weight average molecular weight of 2.4 million, 38.7 g of lithium hydroxide monohydrate, and ions 562 g of exchanged water was stirred in a beaker using a magnetic stirrer. When a uniform aqueous solution was obtained, the solution was filtered through a glass filter to obtain an aqueous solution of a water-soluble polymer neutralized salt (VEMALi) of a copolymer of methyl vinyl ether and maleic anhydride.

[Examples 1 to 10 and Comparative Examples 1 to 8] Production and Evaluation of Nonaqueous Electrolyte Secondary Batteries In Examples and Comparative Examples, nonaqueous electrolyte secondary batteries (lithium secondary batteries) are prepared as follows. It was made according to.

<Production procedure>
[Preparation of positive electrode A]
After mixing 90 parts by mass of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as a positive electrode active material, 5 parts by mass of acetylene black as a conductive material, and 5 parts by mass of polyvinylidene fluoride (PVDF) as a binder, N— A slurry was prepared by dispersing in 140 parts by mass of methyl-2-pyrrolidone (NMP). This slurry was applied to an aluminum current collector, dried and press-molded. Then, this positive electrode was cut into a predetermined size to produce a disc-shaped positive electrode A.

[Preparation of positive electrode B]
72 parts by mass of LiMn ₂ O ₄ and 18 parts by mass of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as a positive electrode active material, 5 parts by mass of acetylene black as a conductive material, and polyvinylidene fluoride (PVDF) 5 as a binder After mixing parts by mass, it was dispersed in 140 parts by mass of N-methyl-2-pyrrolidone (NMP) to form a slurry. This slurry was applied to an aluminum current collector, dried and press-molded. Thereafter, the positive electrode was cut into a predetermined size to produce a disc-shaped positive electrode B.

(Production of negative electrode)
96.0 parts by weight of artificial graphite not subjected to surface treatment as a negative electrode active material having a crystal interlayer distance of 0.3364 nanometers, a specific surface area of 3.5 m ² / g, I _C / _ID of 0.06, and acetylene black 1.0 part by weight, 1.5 parts by weight of styrene butadiene rubber as a binder, and 1.5 parts by weight of VEMALi as a thickener were mixed and dispersed in 120 parts by weight of water to form a slurry. This slurry was applied to a copper negative electrode current collector, dried and press-molded. Then, this negative electrode was cut into a predetermined size to produce a disc-shaped negative electrode.

[Preparation of electrolyte solution A]
LiPF ₆ was dissolved at a concentration of 1 mol / L in a mixed solvent composed of 30% by volume of ethylene carbonate, 40% by volume of ethyl methyl carbonate, 25% by volume of dimethyl carbonate and 5% by volume of propyl acetate to prepare an electrolyte solution A.

[Preparation of electrolyte solution B]
LiPF ₆ was dissolved at a concentration of 1 mol / L in a mixed solvent composed of 30% by volume of ethylene carbonate, 40% by volume of ethyl methyl carbonate, and 30% by volume of dimethyl carbonate to prepare an electrolyte solution B.

(Preparation of non-aqueous electrolyte)
As an electrolytic solution additive, the compounds A1 to A2 of the present invention obtained in Production Example 1 or 2, the compound A3 of the present invention shown below, the compounds B1 to B2 shown below, and the comparative compounds A′1 to A′3 Were dissolved in the electrolyte solution A or B at the ratio shown in [Table 1] or [Table 2] to prepare the nonaqueous electrolytic solution of the present invention and the comparative nonaqueous electrolytic solution. The numbers in parentheses in [Table 1] and [Table 2] represent the concentration (mass%) in the non-aqueous electrolyte.

[Compound A3]
Tris [ difluoro ( ethyl ) silyl ] methane [Compound B1]
Vinylene carbonate [Compound B2]
Propane sultone [Compound A1 ']
Difluorodihexylsilane [Compound A2 ′]
Difluorodiphenylsilane [Compound A3 ′]
1,2-bis (fluorodimethylsilyl) ethane

[Assembling the battery]
The obtained disc-shaped positive electrode A or positive electrode B and disc-shaped negative electrode were held in a case with a microporous film made of polyethylene having a thickness of 25 μm interposed therebetween. Thereafter, each non-aqueous electrolyte solution is injected into the case so that the combination of the non-aqueous electrolyte solution of the present invention or the comparative non-aqueous electrolyte solution and the positive electrode becomes [Table 1] or [Table 2]. Were sealed and sealed, and lithium secondary batteries (a coin type having a diameter of 20 mm and a thickness of 3.2 mm) of Examples 1 to 10 and Comparative Examples 1 to 8 were manufactured.

  Using the lithium secondary batteries of Examples 1 to 10 and Comparative Examples 1 to 8, an initial characteristic test and a cycle characteristic test were performed by the following test methods. In the initial characteristic test, the discharge capacity ratio and the internal resistance ratio were obtained. In the cycle characteristic test, the discharge capacity maintenance rate and the internal resistance increase rate were obtained. The test results are shown in [Table 2] below. In addition, it is a non-aqueous electrolyte secondary battery which is excellent in initial characteristics, so that the discharge capacity ratio is high and the numerical value of internal resistance ratio is low. Moreover, it is a non-aqueous electrolyte secondary battery which is excellent in cycle characteristics, so that a discharge capacity maintenance factor is high and an internal increase rate is low.

<Initial characteristic test method for positive electrode A>
a. Method for measuring discharge capacity ratio A lithium secondary battery is placed in a constant temperature bath at 20 ° C., and charged at a constant current and a constant voltage up to 4.3 V with a charging current of 0.3 mA / cm ² (current value corresponding to 0.2 C). The operation of performing a constant current discharge to 3.0 V at a discharge current of 0.3 mA / cm ² (current value corresponding to 0.2 C) was performed five times. Thereafter, 4.3 V until a constant current and constant voltage charging at a charging current 0.3 mA / cm ^2, and a constant current discharge to 3.0V at a discharge current 0.3 mA / cm ^2. The discharge capacity measured at the sixth time was defined as the initial discharge capacity of the battery, and the ratio of the initial discharge capacity when the discharge capacity ratio (%) was 100 as the initial discharge capacity of Example 1 as shown in the following formula. As sought.
Discharge capacity ratio (%) = [(initial discharge capacity) / (initial discharge capacity in Example 1)] × 100

b. Measuring method of internal resistance ratio About the lithium secondary battery after measuring the discharge capacity at the sixth time, first, constant current charging was performed so that the SOC was 60% at a charging current of 1.5 mA / cm ² (current value equivalent to 1 C). Using an AC impedance measuring device (product name: mobile potentiostat CompactStat, manufactured by IVIUM TECHNOLOGIES), scanning is performed from a frequency of 100 kHz to 0.02 Hz, and the ordinate indicates the imaginary part and the abscissa indicates the real part. It was created. Subsequently, in this Cole-Cole plot, the arc part is fitted with a circle, and the larger value of the two points intersecting the real part of the circle is taken as the initial internal resistance of the battery, as shown in the following formula: The internal resistance ratio (%) was determined as the ratio of the initial internal resistance when the initial internal resistance of Example 1 was 100.
Internal resistance ratio (%) = [(initial internal resistance) / (initial internal resistance in Example 1)] × 100

<Initial characteristic test method for positive electrode B>
The lithium secondary battery was placed in a constant temperature bath at 20 ° C., charged at a constant current and a constant voltage up to 4.2 V with a charging current of 0.3 mA / cm ² (current value corresponding to 0.2 C), and a discharge current of 0.3 mA / The operation of discharging a constant current to 3.0 V at cm ² (current value corresponding to 0.2 C) was performed 5 times. Thereafter, the battery was charged at a constant current and a constant voltage up to 4.2 V at a charging current of 0.3 mA / cm ² and discharged at a constant current of 3.0 mA at a discharge current of 0.3 mA / cm ² . The discharge capacity measured at the sixth time was defined as the initial discharge capacity of the battery, and the discharge capacity ratio (%) was determined in the same manner as the initial characteristic test method in the case of the positive electrode A. For the lithium secondary battery after measuring the discharge capacity at the sixth time, the internal resistance ratio (%) was determined in the same manner as the initial characteristic test method in the case of the positive electrode A.

<Cycle characteristic test method for positive electrode A>
a. Method for measuring discharge capacity retention rate The lithium secondary battery after the initial characteristic test was placed in a constant temperature bath at 60 ° C., and a charging current of 1.5 mA / cm ² (current value equivalent to 1 C, 1 C represents the battery capacity in 1 hour. The cycle of carrying out constant current charging to 4.3 V at a discharging current value) and constant current discharging to 3.0 V at a discharging current of 1.5 mA / cm ² was repeated 200 times. The 200th discharge capacity is defined as the discharge capacity after the cycle test, and the discharge capacity retention rate (%) is obtained as the ratio of the discharge capacity after the cycle test when the initial discharge capacity is 100 as shown in the following formula. It was.
Discharge capacity retention rate (%) = [(discharge capacity after cycle test) / (initial discharge capacity)] × 100

b. Method for measuring rate of increase in internal resistance After the cycle test, the ambient temperature is returned to 20 ° C., and the internal resistance at 20 ° C. is measured in the same manner as the method for measuring the internal resistance ratio. The internal resistance increase rate (%) was determined as the rate of increase in internal resistance after the cycle test when the initial internal resistance of each battery was 100, as shown in the following formula.
Internal resistance increase rate (%) = [(internal resistance after cycle test−initial internal resistance) / (initial internal resistance)] × 100

<Cycle characteristic test method for positive electrode B>
The lithium secondary battery after the initial characteristic test is placed in a constant temperature bath at 60 ° C., and the charging current is 1.5 mA / cm ² (current value equivalent to 1C, 1C is the current value at which the battery capacity is discharged in 1 hour). The cycle of charging at a constant current to ² V and discharging at a constant current of 1.5 mA / cm ² to 3.0 V was repeated 200 times. The discharge capacity at the 200th time was defined as the discharge capacity after the cycle test, and the discharge capacity retention rate (%) was determined in the same manner as the cycle characteristic test method in the case of the positive electrode A. For the lithium secondary battery after the cycle test, the rate of increase in internal resistance (%) was determined in the same manner as the cycle characteristic test method for positive electrode A.

  As is apparent from the results of [Table 3] and [Table 4], the non-aqueous electrolyte contains a fluorosilane compound having three or more alkyldifluorosilyl groups bonded in the molecule. The water electrolyte secondary battery is excellent in terms of internal resistance and discharge capacity and can maintain excellent battery characteristics even when a small amount of the fluorosilane compound is added after a cycle test at 60 ° C. Was confirmed.

  The non-aqueous electrolyte secondary battery of the present invention is useful because it can maintain a small internal resistance and a high discharge capacity even when used for a long period of time and a large temperature change.

DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Positive electrode collector 2 Negative electrode 2a Negative electrode collector 3 Electrolyte 4 Positive electrode case 5 Negative electrode case 6 Gasket 7 Separator 10 Coin type nonaqueous electrolyte secondary battery 10 'Cylindrical type 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 22 Positive electrode lead 23 Case 24 Insulating plate 25 Gasket 26 Safety valve 27 PTC element

Claims (1)

A fluorosilane compound represented by the following general formula (1 ′).

(In the formula, R ^{1 ′} represents an alkyl group having 1 to 8 carbon atoms, and n ′ represents a number of 3 or 4.)

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