Nonaqueous electrolyte solution for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery including the same

Abstract

To provide a nonaqueous electrolyte capable of achieving improved battery cycle characteristics, and a nonaqueous electrolyte secondary battery including the nonaqueous electrolyte.SOLUTION: A nonaqueous electrolyte contains a nonaqueous solvent, an electrolyte salt dissolved in the nonaqueous solvent, and a silane compound represented by the following general formula (1) (where R1 represents a C2 to 20 alkenyl group; R2 represents a C8 to 20 substituted or unsubstituted arylethynyl group; R3 represents a C1 to 20 alkyl group; R4 represents a C2 to 20 alkynyl group; each of l and m independently represents an integer of 1 to 3; n represents an integer of 0 to 2; and l, m, and n are integers satisfying 2≤l+m+n≤4).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a non-aqueous electrolyte solution and a non-aqueous electrolyte secondary battery including the same. [Background technology]

[0002] In recent years, small electronic devices such as mobile terminals have become widespread, and there is a strong demand for further miniaturization, weight reduction, and longer life. In response to such market demands, development of secondary batteries that are particularly small and lightweight and capable of achieving high energy density has been progressing. The application of these secondary batteries is being considered not only for small electronic devices but also for large electronic devices such as automobiles and power storage systems such as those for homes.

[0003] Among these, lithium-ion secondary batteries are attracting great attention because they can be easily made small and have a high capacity, and can provide a higher energy density than lead-acid batteries and nickel-cadmium batteries.

[0004] The lithium ion secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte solution, and the negative electrode contains a negative electrode active material involved in charge and discharge reactions.

[0005] While carbon-based active materials are widely used as negative electrode active materials, recent market demands have called for further improvements in battery capacity. To improve battery capacity, the use of silicon as a negative electrode active material is being considered. This is because the theoretical capacity of silicon (4199 mAh / g) is more than 10 times greater than that of graphite (372 mAh / g), and a significant improvement in battery capacity can be expected. The development of silicon materials as negative electrode active materials is being considered not only for silicon itself, but also for alloys and compounds such as oxides. Furthermore, the shape of the negative electrode active material is being considered, ranging from the standard coated type used for carbon-based active materials to an integrated type deposited directly on the current collector.

[0006] However, when silicon is used as the primary raw material for the negative electrode active material, the negative electrode active material expands and contracts during charging and discharging, making it prone to cracking, primarily near the surface. Furthermore, ionic substances are generated within the negative electrode active material, making it prone to cracking. When the surface layer of the negative electrode active material cracks, a new surface is created, increasing the reactive area of the negative electrode active material. At this time, the electrolyte decomposes on the new surface, and a coating of the electrolyte decomposition product is formed on the new surface, consuming the electrolyte and potentially reducing cycle performance.

[0007] To date, various studies have been conducted on negative electrode materials and electrode configurations for lithium-ion secondary batteries that use silicon materials as the main material in order to improve the initial battery efficiency and cycle characteristics.

[0008] Specifically, to achieve good cycle characteristics and high safety, silicon and amorphous silicon dioxide are simultaneously deposited using a vapor phase method (see, for example, Patent Document 1). Furthermore, to achieve high battery capacity and safety, a carbon material (electron-conductive material) is provided on the surface layer of silicon oxide particles (see, for example, Patent Document 2). Furthermore, to improve cycle characteristics and achieve high input / output characteristics, an active material containing silicon and oxygen is prepared, and an active material layer with a high oxygen ratio near the current collector is formed (see, for example, Patent Document 3). Furthermore, to improve cycle characteristics, oxygen is incorporated into the silicon active material, and the silicon active material is formed so that the average oxygen content is 40 at% or less and the oxygen content is higher near the current collector (see, for example, Patent Document 4).

[0009] There are also reports of using fluoroethylene carbonate (FEC) as an electrolyte additive to suppress the decomposition reaction of the electrolyte accompanying the charge and discharge of silicon active materials (see, for example, Patent Document 5). Fluorine-based electrolytes form a stable solid electrolyte interphase (SEI) film on the silicon surface, making it possible to suppress the deterioration of silicon materials. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-185127 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-042806 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-164954 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-114454 [Patent Document 5] Japanese Patent Application Laid-Open No. 2006-134719 Summary of the Invention [Problem to be solved by the invention]

[0011] As mentioned above, compact electronic devices, such as mobile terminals, have become increasingly sophisticated and multifunctional in recent years, necessitating increased battery capacity for their primary power source: lithium-ion secondary batteries. One solution to this problem is the development of lithium-ion secondary batteries with anodes primarily made of silicon materials. Furthermore, lithium-ion secondary batteries using silicon materials are expected to have cycle characteristics comparable to those of lithium-ion secondary batteries using carbon-based active materials. To address this issue, fluorine-based additives have been developed, which have tended to improve battery performance. However, repeated charge-discharge cycles consume the fluorine-based solvent, increasing the amount of electrolyte decomposition products that accumulate on the silicon material surface. This deactivates the reversibly mobile lithium by trapping it in the decomposition products, resulting in poor battery cycle performance and cell swelling. These problems remain unresolved compared to batteries using carbon-based active materials.

[0012] The present invention has been made in view of the above problems, and has an object to provide a nonaqueous electrolyte solution that can achieve improved battery cycle characteristics, and a nonaqueous electrolyte secondary battery that includes this nonaqueous electrolyte solution. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention provides a method for producing a liquid crystal display comprising: an electrolyte salt dissolved in the non-aqueous solvent; The following general formula (1) [ka] (In general formula (1), R 1 is an alkenyl group having 2 to 20 carbon atoms, and R 2 is a substituted or unsubstituted arylethynyl group having 8 to 20 carbon atoms, and R 3 is an alkyl group having 1 to 20 carbon atoms, and R 4 is an alkynyl group having 2 to 20 carbon atoms. Furthermore, l and m each independently represent an integer of 1 to 3, n represents an integer of 0 to 2, and l, m, and n are integers that satisfy the relationship 2≦l+m+n≦4. and a silane compound represented by the formula: The present invention provides a non-aqueous electrolyte solution comprising:

[0014] Silane compounds containing at least one alkenyl group and at least one arylethynyl group can decompose on the negative electrode surface during charging to form a high-quality coating. In particular, this stabilizes the reaction of the Li silicate moiety that constitutes the silicon-based negative electrode active material, resulting in the formation of a high-quality coating. Furthermore, this not only suppresses the reaction with Li2SiO3 that constitutes the silicon-based negative electrode material, but also enables the stable formation of a coating with Li4SiO4, which is formed by the conversion of Li2SiO3 during repeated charge and discharge. As a result, the battery's cycle characteristics are improved and battery swelling is suppressed.

[0015] The silane compound represented by the general formula (1) is a compound represented by the general formula (1) R 2 However, it is preferably an unsubstituted arylethynyl group, or an arylethynyl group having 8 to 20 carbon atoms in which some or all of the hydrogen atoms of the aryl group have been substituted with a hydrocarbon group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0016] If such a silane compound is contained, the cycle characteristics of the battery can be improved and battery swelling can be suppressed.

[0017] The silane compound represented by the general formula (1) is preferably one in which l and m in the general formula (1) each independently represent an integer of 1 to 3, n represents an integer of 0 to 1, and l, m, and n are integers that satisfy l+m+n=4.

[0018] If such a silane compound is contained, the battery characteristics can be more sufficiently improved.

[0019] The content of the silane compound in the non-aqueous electrolyte solution is preferably 0.1% by mass to 5.0% by mass.

[0020] If the silane compound is contained in such a concentration, the battery characteristics can be more sufficiently improved.

[0021] The present invention also provides a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte solution, The present invention provides a non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte is the non-aqueous electrolyte of the present invention.

[0022] Such a non-aqueous electrolyte secondary battery contains the non-aqueous electrolyte solution of the present invention, and therefore can exhibit improved cycle characteristics and can suppress battery swelling.

[0023] The negative electrode contains negative electrode active material particles, and the negative electrode active material particles contain silicon oxide particles that contain Li2SiO3 and are coated with a carbon layer, and the Li2SiO3 preferably contains crystalline Li2SiO3.

[0024] Such a non-aqueous electrolyte secondary battery can exhibit higher capacity and improved cycle characteristics, and can also sufficiently suppress battery swelling.

[0025] In this case, the negative electrode active material particles have a peak attributable to a Si(111) crystal plane obtained by X-ray diffraction using Cu-Kα radiation before charging and discharging the negative electrode active material particles, the crystallite size corresponding to the crystal plane is 5.0 nm or less, and the ratio A / B of the intensity A of the peak attributable to the Si(111) crystal plane to the intensity B of the peak attributable to the Li2SiO3(111) crystal plane satisfies the following formula (2): 0.4≦A / B≦1.0 (2) It is preferable that the above condition is satisfied.

[0026] Such negative electrode active material particles can exhibit high slurry stability without impairing the ease of conversion from Li2SiO3 to Li4SiO4, and therefore, a nonaqueous electrolyte secondary battery containing such negative electrode active material particles can exhibit superior battery characteristics. [Effects of the Invention]

[0027] As described above, the nonaqueous electrolyte of the present invention can realize improved battery cycle characteristics and can also suppress battery swelling.

[0028] In particular, the nonaqueous electrolyte solution of the present invention can achieve sufficient battery cycle characteristics even in nonaqueous electrolyte secondary batteries using silicon-based negative electrode materials.

[0029] Furthermore, the nonaqueous electrolyte secondary battery of the present invention can achieve improved battery cycle characteristics and can also suppress battery swelling. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a schematic exploded view showing an example of a nonaqueous electrolyte secondary battery of the present invention. [Figure 2] 1 is a schematic cross-sectional view of an example of a negative electrode that can be provided in a nonaqueous electrolyte secondary battery of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] As described above, there has been a need for the development of a non-aqueous electrolyte solution that can achieve improved battery cycle characteristics, and a non-aqueous electrolyte secondary battery that includes this non-aqueous electrolyte solution.

[0032] As a result of extensive research into achieving the above object, the present inventors have found that the above object can be achieved by using a non-aqueous electrolyte solution containing a silane compound having at least one alkenyl group and at least one arylethynyl group, and have thus completed the present invention.

[0033] That is, the present invention provides a method for producing a liquid crystal display comprising: a non-aqueous solvent; an electrolyte salt dissolved in the non-aqueous solvent; The following general formula (1) [ka] (In general formula (1), R 1 is an alkenyl group having 2 to 20 carbon atoms, and R 2 is a substituted or unsubstituted arylethynyl group having 8 to 20 carbon atoms, and R 3 is an alkyl group having 1 to 20 carbon atoms, and R 4 is an alkynyl group having 2 to 20 carbon atoms. Furthermore, l and m each independently represent an integer of 1 to 3, n represents an integer of 0 to 2, and l, m, and n are integers that satisfy the relationship 2≦l+m+n≦4. and a silane compound represented by the formula: The non-aqueous electrolyte solution is characterized by comprising:

[0034] The present invention also provides a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte solution, The nonaqueous electrolyte secondary battery is characterized in that the nonaqueous electrolyte is the nonaqueous electrolyte of the present invention.

[0035] The present invention will be described in detail below, but the present invention is not limited thereto.

[0036] [Nonaqueous electrolyte] The non-aqueous electrolyte of the present invention contains a silane compound represented by the following general formula (1), which has at least one alkenyl group and at least one arylethynyl group (hereinafter referred to as "compound (1)").

[0037] [ka]

[0038] Compound (1) will be described in more detail below.

[0039] In general formula (1), R 1 is an alkenyl group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, and more preferably 2 to 5 carbon atoms.

[0040] R 1 Specific examples of the alkenyl group include linear alkenyl groups such as vinyl, n-propenyl, n-butenyl, n-pentenyl, n-hexenyl, n-heptenyl, n-octenyl, n-nonenyl, n-decenyl, n-undecenyl, and n-dodecenyl; and branched alkenyl groups such as isopropenyl, isobutenyl, isopentenyl, isohexenyl, isoheptenyl, isooctenyl, isononyl, isodecenyl, and isoundecyl.

[0041] Among these, vinyl group and n-propenyl group are preferred from the viewpoint of sufficiently improving battery characteristics.

[0042] The alkenyl groups are decomposed on the negative electrode surface during charging to form a high-quality coating, which prevents direct contact between the nonaqueous electrolyte and the electrode active material, preventing decomposition of the nonaqueous solvent and solute, and suppressing deterioration of battery performance.

[0043] In general formula (1), R 2 is a substituted or unsubstituted arylethynyl group having 8 to 20 carbon atoms, preferably 8 to 16 carbon atoms, and more preferably 8 to 12 carbon atoms.

[0044] R 2 Specific examples of the unsubstituted arylethynyl group include unsubstituted arylethynyl groups such as a phenylethynyl group, a 1-naphthylethynyl group, a 2-naphthylethynyl group, a 1-anthracenylethynyl group, a 2-anthracenylethynyl group, and a 9-anthracenylethynyl group.

[0045] Also, R 2 In the arylethynyl group, some or all of the hydrogen atoms of the aryl group may be substituted with a hydrocarbon group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. Specific examples of the hydrocarbon group include alkyl groups having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, such as methyl and ethyl; alkenyl groups having 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, such as vinyl and n-propenyl; and alkynyl groups having 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, such as ethynyl and 1-propynyl. Specific examples of the alkoxy group include alkoxy groups having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, such as methoxy, ethoxy, n-propoxy, and isopropoxy, with methoxy and ethoxy being preferred. Specific examples of the halogen atom include fluorine, chlorine, bromine, and iodine atoms, with fluorine being preferred.

[0046] R 2Specific examples of the arylethynyl group substituted with a hydrocarbon group include arylethynyl groups in which a hydrogen atom of the aryl group is substituted with an alkyl group, such as a 2-methylphenylethynyl group, a 3-methylphenylethynyl group, a 4-methylphenylethynyl group, a 2-ethylphenylethynyl group, a 3-ethylphenylethynyl group, a 4-ethylphenylethynyl group, a 3-acenaphthenylethynyl group, a 4-acenaphthenylethynyl group, and a 5-acenaphthenylethynyl group; arylethynyl groups in which a hydrogen atom of the aryl group is substituted with an alkenyl group, such as a 2-vinylphenylethynyl group, a 3-vinylphenylethynyl group, and a 4-vinylphenylethynyl group; and arylethynyl groups in which a hydrogen atom of the aryl group is substituted with an alkynyl group, such as a 2-ethynylphenylethynyl group, a 3-ethynylphenylethynyl group, and a 4-ethynylphenylethynyl group.

[0047] R 2 Specific examples of the arylethynyl group substituted with an alkoxy group include a 2-methoxyphenylethynyl group, a 3-methoxyphenylethynyl group, a 4-methoxyphenylethynyl group, a 2-ethoxyphenylethynyl group, a 3-ethoxyphenylethynyl group, a 4-ethoxyphenylethynyl group, a 2,3-dimethoxyphenylethynyl group, a 2,4-dimethoxyphenylethynyl group, a 2,5-dimethoxyphenylethynyl group, a 2,6-dimethoxyphenylethynyl group, a 3,4-dimethoxyphenylethynyl group, and a 3,5-dimethoxyphenylethynyl group.

[0048] R 2Specific examples of the arylethynyl group substituted with a halogen atom include a 2-fluorophenylethynyl group, a 3-fluorophenylethynyl group, a 4-fluorophenylethynyl group, a 2-chlorophenylethynyl group, a 3-chlorophenylethynyl group, a 4-chlorophenylethynyl group, a 2-bromophenylethynyl group, a 3-bromophenylethynyl group, a 4-bromophenylethynyl group, a 2-iodophenylethynyl group, a 3-iodophenylethynyl group, a 4-iodophenylethynyl group, a 2,3-difluorophenylethynyl group, a 2,4-difluorophenylethynyl group, a 2,5-difluorophenylethynyl group, a 2,6-difluorophenylethynyl group, a 3,4-difluorophenylethynyl group, and a 3,5-difluorophenylethynyl group.

[0049] Among these, from the viewpoint of sufficiently improving battery characteristics, preferred are unsubstituted arylethynyl groups such as a phenylethynyl group, arylethynyl groups substituted with an alkyl group such as a 4-methylphenylethynyl group or a 4-ethylphenylethynyl group, arylethynyl groups substituted with an alkoxy group such as a 4-methoxyphenylethynyl group or a 4-ethoxyphenylethynyl group, and arylethynyl groups substituted with a halogen atom such as a 4-fluorophenylethynyl group, a 4-bromophenylethynyl group, a 4-chlorophenylethynyl group, or a 4-iodophenylethynyl group.

[0050] The arylethynyl group decomposes on the negative electrode surface during charging, forming a high-quality coating. This coating prevents direct contact between the nonaqueous electrolyte and the electrode active material, preventing decomposition of the nonaqueous solvent and solute, and suppressing deterioration of battery performance. In addition, the aryl group in the arylethynyl group has a significant effect of lowering the lowest unoccupied molecular orbital (LUMO) level of the compound. Therefore, compounds containing arylethynyl groups are relatively easily decomposed on the negative electrode surface during charging, and are likely to form a high-quality coating.

[0051] In general formula (1), R 3 is an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 4 carbon atoms.

[0052] R 3 Specific examples of the alkyl group include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, and n-dodecyl groups; and branched alkyl groups such as isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, isohexyl, isoheptyl, isooctyl, tert-octyl, isononyl, isodecyl, and isoundecyl groups.

[0053] Among these, a methyl group, an ethyl group, and an n-propyl group are preferred from the viewpoint of sufficiently improving battery characteristics.

[0054] In general formula (1), R 4 represents an alkynyl group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, and more preferably 2 to 5 carbon atoms.

[0055] R 4 Specific examples of the alkynyl group include linear alkynyl groups such as ethynyl, 1-propynyl, 1-butynyl, 1-pentynyl, 1-hexynyl, 1-heptynyl, 1-octynyl, 1-nonynyl, 1-decynyl, 1-undecynyl, and 1-dodecynyl; and branched alkynyl groups such as 3-methyl-1-butynyl, 3,3-dimethyl-1-butynyl, 3-methyl-1-pentynyl, 4-methyl-1-pentynyl, 3,3-dimethyl-1-pentynyl, 3,4-methyl-1-pentynyl, and 4,4-dimethyl-1-pentynyl.

[0056] Among these, from the viewpoint of sufficiently improving battery characteristics, an ethynyl group, a 1-propynyl group, and a 1-butynyl group are preferred.

[0057] In general formula (1), l and m each independently represent an integer of 1 to 3, n represents an integer of 0 to 2, and l, m, and n are integers that satisfy 2≦l+m+n≦4. From the viewpoint of sufficiently improving battery characteristics, it is preferable that in general formula (1), l and m each independently represent an integer of 1 to 3, n represents 0 to 1, and l, m, and n are integers that satisfy l+m+n=4.

[0058] Compound (1), which has at least one alkenyl group and at least one arylethynyl group, decomposes on the negative electrode surface during charging to form a high-quality coating. This stabilizes the reaction of the Li silicate moiety that constitutes the silicon-based negative electrode active material, resulting in the formation of a high-quality coating. This not only suppresses the reaction with Li2SiO3 that constitutes the silicon-based negative electrode material, but also enables the stable formation of a coating with Li4SiO4, which is formed by the conversion of Li2SiO3 during repeated charge and discharge. This improves the battery's cycle performance and suppresses battery swelling.

[0059] Specific examples of compound (1) include phenylethynyltrivinylsilane, bis(phenylethynyl)divinylsilane, tris(phenylethynyl)vinylsilane, 4-methylphenylethynyltrivinylsilane, bis(4-methylphenylethynyl)divinylsilane, tris(4-methylphenylethynyl)vinylsilane, 4-methoxyphenylethynyltrivinylsilane, bis(4-methoxyphenylethynyl)divinylsilane, tris(4-methoxyphenylethynyl)vinylsilane, 4-fluorophenylethynyltrivinylsilane, bis(4-fluorophenylethynyl)divinylsilane, tris(4-fluorophenylethynyl)vinylsilane, phenylethynylmethyldivinylsilane, bis(phenylethynyl)methylvinylsilane, 4-methylphenylethynylmethyl phenylethynyldimethylvinylsilane, bis(4-methylphenylethynyl)methylvinylsilane, 4-methoxyphenylethynylmethyldivinylsilane, bis(4-methoxyphenylethynyl)methylvinylsilane, 4-fluorophenylethynylmethyldivinylsilane, bis(4-fluorophenylethynyl)methylvinylsilane, phenylethynyldimethylvinylsilane, 4-methylphenylethynyldimethylvinylsilane, 4-methoxyphenylethynyldimethylvinylsilane, 4-fluorophenylethynyldimethylvinylsilane, ethynylphenylethynylmethylvinylsilane, ethynyl-4-methylphenylethynylmethylvinylsilane, ethynyl-4-methoxyphenylethynylmethylvinylsilane, ethynyl-4-fluorophenylethynylmethylvinylsilane, and the like.

[0060] The silane compound represented by the general formula (1) can be obtained, for example, by reacting a vinylhalosilane with an arylethynyl magnesium halide or an arylethynyl lithium.

[0061] The content of the compound (1) in the non-aqueous electrolyte is preferably 0.1% by mass to 5.0% by mass, more preferably 0.1% by mass to 4.0% by mass, and even more preferably 0.1% by mass to 2.0% by mass, from the viewpoint of sufficiently improving battery performance.

[0062] The non-aqueous electrolyte of the present invention further contains, in addition to the compound (1), a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte of the present invention may contain other materials as additives.

[0063] Examples of non-aqueous solvents include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, 1,2-dimethoxyethane, and tetrahydrofuran. Among these, from the viewpoint of obtaining better properties, it is desirable to use at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. In this case, by combining a high-viscosity solvent such as ethylene carbonate or propylene carbonate with a low-viscosity solvent such as dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate, the dissociation property and ion mobility of the electrolyte salt are improved, resulting in more advantageous properties.

[0064] When using an alloy-based negative electrode containing a silicon-based negative electrode material, it is particularly desirable to use a non-aqueous solvent containing at least one of a halogenated chain carbonate or a halogenated cyclic carbonate. This allows a stable coating to be formed on the surface of the negative electrode active material during charge and discharge, particularly during charging. Here, the halogenated chain carbonate is a chain carbonate having a halogen as a constituent element (i.e., at least one hydrogen atom is substituted with a halogen). Furthermore, the halogenated cyclic carbonate is a cyclic carbonate having a halogen as a constituent element (i.e., at least one hydrogen atom is substituted with a halogen).

[0065] Although the type of halogen is not particularly limited, fluorine is preferred from the viewpoint of forming a coating film of better quality than other halogens. In addition, the number of halogens is preferably as large as possible, since the resulting coating film is more stable and the decomposition reaction of the electrolyte is reduced.

[0066] Examples of halogenated chain carbonates include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, etc. Examples of halogenated cyclic carbonates include 4-fluoro-1,3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one, etc.

[0067] The electrolyte salt may include, for example, one or more light metal salts such as lithium salts, for example, lithium hexafluorophosphate (LiPF6) and lithium tetrafluoroborate (LiBF4).

[0068] From the viewpoint of obtaining high ionic conductivity, the content of the electrolyte salt is preferably 0.5 mol / kg or more and 2.5 mol / kg or less, more preferably 0.8 mol / kg or more and 2.0 mol / kg or less, and even more preferably 0.8 mol / kg or more and 1.5 mol / kg or less, relative to the non-aqueous solvent.

[0069] The non-aqueous electrolyte of the present invention may contain, as additives other than compound (1), for example, unsaturated carbon-bond cyclic carbonate, sultone (cyclic sulfonate), and acid anhydride.

[0070] The unsaturated carbon-bond cyclic carbonate may be contained from the viewpoint of forming a stable coating on the negative electrode surface during charge and discharge and from the viewpoint of suppressing the decomposition reaction of the non-aqueous electrolyte solution, and examples thereof include vinylene carbonate and vinylethylene carbonate.

[0071] Furthermore, a sultone may be contained from the viewpoint of improving the chemical stability of the battery, and examples thereof include propane sultone and propene sultone.

[0072] Furthermore, an acid anhydride may be contained from the viewpoint of improving the chemical stability of the electrolyte solution, and examples thereof include propanedisulfonic acid anhydride.

[0073] The qualitative and quantitative analysis of the compound (1) in the non-aqueous electrolyte solution can be carried out by, for example, gas chromatography-mass spectrometry (GC / MS).

[0074] [Nonaqueous electrolyte secondary battery] The nonaqueous electrolyte secondary battery of the present invention includes a positive electrode and a negative electrode in addition to the nonaqueous electrolyte solution. That is, the nonaqueous electrolyte solution of the present invention described above can be used as a nonaqueous electrolyte solution for a nonaqueous electrolyte secondary battery.

[0075] The positive electrode and negative electrode that can be provided in the nonaqueous electrolyte secondary battery of the present invention will be described below.

[0076] [Positive electrode] The positive electrode has a structure in which a positive electrode active material layer is provided on one or both sides of a positive electrode current collector, for example.

[0077] Here, the positive electrode current collector is formed of a conductive material such as aluminum.

[0078] On the other hand, the positive electrode active material layer contains one or more positive electrode materials capable of absorbing and releasing lithium ions, and may contain other materials such as a binder, a conductive additive, a dispersant, etc. In this case, the binder and conductive additive may be, for example, the same as the negative electrode binder and negative electrode conductive additive described below.

[0079] As the positive electrode material, from the viewpoint of obtaining a high battery capacity and excellent cycle characteristics, for example, a lithium-containing compound such as a composite oxide having lithium and a transition metal element or a phosphate compound having lithium and a transition metal element can be used.

[0080] The transition metal element is preferably nickel, iron, manganese, or cobalt, and the lithium-containing compound is a compound containing at least one of these transition metal elements.

[0081] The chemical formula of the lithium-containing compound is, for example, Li a M1O2 or Lib It is represented by M2PO4. In the formula, M1 and M2 represent at least one transition metal element. The values of a and b are different depending on the charge and discharge state of the battery, but generally are numbers satisfying 0.05 ≦ a ≦ 1.10 and 0.05 ≦ b ≦ 1.10.

[0082] Specific examples of the composite oxide having lithium and a transition metal element include, for example, lithium cobalt composite oxide (Li x CoO2), lithium nickel composite oxide (Li x NiO2), lithium nickel cobalt composite oxide, lithium nickel cobalt composite oxide (lithium nickel cobalt aluminum composite oxide; NCA, lithium nickel cobalt manganese composite oxide + NCM), and the like.

[0083] Specific examples of the phosphate compound having lithium and a transition metal element include, for example, lithium iron phosphate compound (LiFePO4), lithium iron manganese phosphate compound (LiFe 1-u Mn u PO4, provided that 0 < u < 1), and the like. By using these positive electrode materials, a high battery capacity can be obtained and excellent cycle characteristics can also be obtained.

[0084] [Negative electrode] The negative electrode has, for example, a structure having a negative electrode active material layer on a negative electrode current collector. This negative electrode active material layer may be provided on both sides or only one side of the negative electrode current collector.

[0085] [Negative electrode current collector] The negative electrode current collector is an excellent conductive material and is composed of a material having high mechanical strength. Examples of the conductive material that can be used for the negative electrode current collector include copper (Cu) and nickel (Ni). This conductive material is preferably a material that does not form an intermetallic compound with lithium (Li).

[0086] From the viewpoint of improving the physical strength of the negative electrode current collector, it is preferable that the negative electrode current collector contains carbon (C) and sulfur (S) in addition to the copper (Cu) and nickel (Ni). In particular, when an active material layer that expands during charging is included, the current collector contains the above elements, which has the effect of suppressing deformation of the electrode including the current collector. The contents of the above contained elements are not particularly limited, but from the viewpoint of obtaining a higher deformation suppression effect, it is preferable that each be 100 mass ppm or less. Such a deformation suppression effect can further improve cycle characteristics.

[0087] The surface of the negative electrode current collector may be roughened or not. Examples of roughened negative electrode current collectors include metal foils that have been subjected to electrolytic treatment, embossing treatment, or chemical etching treatment. Examples of non-roughened negative electrode current collectors include rolled metal foils.

[0088] [Negative electrode active material layer] The negative electrode active material layer may include a negative electrode active material capable of absorbing (inserting) and releasing lithium ions, and the negative electrode active material may include negative electrode active material particles. The negative electrode active material particles include, for example, silicon compound particles (silicon oxide particles) containing a silicon compound containing oxygen.

[0089] The negative electrode active material contains silicon compound particles (silicon-based negative electrode active material), and the silicon compound particles are preferably silicon oxide materials containing silicon compounds containing oxygen. x From the viewpoint of cycle characteristics and resistance of silicon oxide, it is preferable that x, which is the composition ratio of silicon to oxygen constituting SiO , is a number that satisfies 0.8≦x≦1.2. x In the composition, x is preferably closer to 1 because it provides high cycle characteristics.

[0090] The composition of the silicon compound in the present invention does not necessarily mean 100% purity, and may contain trace amounts of impurity elements.

[0091] The silicon compound preferably contains as little crystalline Si as possible. By containing as little crystalline Si as possible, it is possible to prevent the reactivity with the electrolyte from becoming too high, and as a result, it is possible to prevent the deterioration of battery characteristics. It is preferable that the silicon compound is substantially amorphous.

[0092] The silicon compound contains Li, and it is preferable that a portion of it is in the form of silicate Li2SiO3. This Li2SiO3 includes crystalline material, but is active during charge and discharge. In the slurry state, it remains Li2SiO3, but changes to Li4SiO4 after repeated charge and discharge.

[0093] The negative electrode contains negative electrode active material particles, and the negative electrode active material particles contain silicon oxide particles that contain Li2SiO3 and are coated with a carbon layer, and it is particularly preferable that the Li2SiO3 contains crystalline Li2SiO3.

[0094] When the negative electrode contains such negative electrode active material particles, it is possible to realize a higher capacity and improved cycle characteristics, and also to sufficiently suppress battery swelling.

[0095] Furthermore, the higher the crystallinity of Li2SiO3, the more difficult it is to convert to Li4SiO4. On the other hand, when the crystallinity is low, it becomes more likely to dissolve in the slurry, so there is an optimum range.

[0096] Specifically, the negative electrode active material particles have a peak attributable to the Si(111) crystal plane obtained by X-ray diffraction using Cu-Kα radiation before charging and discharging the negative electrode active material particles, the crystallite size corresponding to the crystal plane is 5.0 nm or less, and the ratio A / B of the intensity A of the peak attributable to the Si(111) crystal plane to the intensity B of the peak attributable to the Li2SiO3(111) crystal plane satisfies the following formula (2): 0.4≦A / B≦1.0 (2) It is preferable that the following is satisfied.

[0097] The degree of Li silicate enlargement and the degree of Si crystallization (for example, the crystallite size corresponding to the Si(111) crystal plane) can be confirmed by X-ray diffraction (hereinafter also referred to as "XRD").

[0098] The X-ray diffraction device used can be a Bruker D8 ADVANCE. The X-ray source is Cu Kα radiation and a Ni filter, and measurements are taken from 10 to 40° with an output of 40 kV / 40 mA, a slit width of 0.3°, a step width of 0.008°, and a counting time of 0.15 seconds per step.

[0099] The peak due to the Si(111) crystal plane appears near 2θ=28.4° in the X-ray diffraction chart.

[0100] The crystallite size corresponding to the Si(111) crystal plane is preferably 5.0 nm or less, more preferably 4.0 nm or less, and more preferably 2.5 nm or less.

[0101] The ratio A / B of the intensity A of the peak due to the Si(111) crystal plane to the intensity B of the peak due to the Li2SiO3(111) crystal plane is preferably 0.40≦A / B≦1.00, more preferably 0.45≦A / B≦0.75, and even more preferably 0.50≦A / B≦0.70.

[0102] Here, the peak due to the Li2SiO3 (111) crystal plane appears in the range of 2θ=17° to 21° in the X-ray diffraction chart.

[0103] The median diameter of the negative electrode active material, as measured by a laser diffraction method, is preferably 5.0 μm or more and 15.0 μm or less, more preferably 5.5 μm or more and 10.0 μm or less, and even more preferably 6.0 μm or more and 8.0 μm or less, from the viewpoint of controlling the reaction with the electrolyte or suppressing expansion of the negative electrode active material during charge and discharge.

[0104] The negative electrode active material layer may contain a mixed negative electrode active material containing the silicon-based negative electrode active material and a carbon-based active material. This reduces the electrical resistance of the negative electrode active material layer and alleviates expansion stress caused by charging. Examples of carbon-based active materials include natural graphite, artificial graphite, hard carbon, and soft carbon.

[0105] The negative electrode active material layer contains a negative electrode active material capable of absorbing and releasing lithium ions, and may further contain other materials such as a negative electrode binder and a conductive additive from the viewpoint of battery design.

[0106] The negative electrode binder may be, for example, one or more of polymer materials, synthetic rubber, etc. Examples of polymer materials include polyvinylidene fluoride, polyimide, polyamideimide, aramid, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, carboxymethyl cellulose, etc. Examples of synthetic rubbers include styrene-butadiene rubber, fluorine-based rubber, ethylene propylene diene, etc.

[0107] Examples of the negative electrode conductive assistant include fine carbon particles, carbon black, acetylene black, graphite, Ketjen black, carbon nanotubes, and carbon nanofibers, and one or more of these can be used.

[0108] The negative electrode active material layer is formed, for example, by a coating method in which a silicon-based negative electrode active material, a binder, and the like are mixed with a negative electrode conductive additive and a carbon-based active material as needed, and then the mixture is dispersed in an organic solvent, water, or the like and coated.

[0109] [Separator] The nonaqueous electrolyte secondary battery of the present invention may further include a separator.

[0110] The separator separates the lithium metal or positive electrode from the negative electrode, preventing current short-circuiting due to contact between the two electrodes while allowing lithium ions to pass through. This separator is formed, for example, from a porous film made of synthetic resin or ceramic, and may have a laminate structure in which two or more types of porous film are laminated. Examples of synthetic resins include polytetrafluoroethylene, polypropylene, and polyethylene.

[0111] In the nonaqueous electrolyte secondary battery of the present invention, the nonaqueous electrolyte may be impregnated into, for example, at least a portion of the positive electrode active material layer, at least a portion of the negative electrode active material layer, and at least a portion of the separator.

[0112] [Configuration example of non-aqueous electrolyte secondary battery] Next, as a specific example of the nonaqueous electrolyte secondary battery of the present invention, an example of a laminate film type lithium ion secondary battery will be described with reference to the drawings, although the nonaqueous electrolyte secondary battery of the present invention is not limited to the following specific example.

[0113] The laminate film type lithium ion secondary battery 10 shown in FIG. 1 mainly comprises an electrode body 1 housed inside a sheet-like exterior member 5. This electrode body 1 has a positive electrode, a negative electrode, and a separator therebetween, and is wound up. Alternatively, there are cases where the electrode body is not wound, but instead houses a laminate having a positive electrode, a negative electrode, and a separator therebetween. In either type of electrode body, a positive electrode lead 2 is attached to the positive electrode, and a negative electrode lead 3 is attached to the negative electrode. The outermost periphery of the electrode body is protected by protective tape.

[0114] The negative electrode can have, for example, a structure whose cross section is shown in Fig. 2. The negative electrode 30 shown in Fig. 2 has a configuration in which a negative electrode active material layer 32 is provided on a negative electrode current collector 31.

[0115] Although not shown, the positive electrode, like the negative electrode 30, has a configuration including, for example, a positive electrode active material layer on a positive electrode current collector.

[0116] The positive electrode lead 2 and the negative electrode lead 3 are led out in one direction, for example, from the inside to the outside of the exterior member 5. The positive electrode lead 2 is made of a conductive material such as aluminum, and the negative electrode lead 3 is made of a conductive material such as nickel or copper.

[0117] The exterior member 5 is, for example, a laminate film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order, and the outer peripheral edges of the fusion layers of two laminate films are fused together or attached with an adhesive or the like so that the fusion layer faces the electrode body 1. The fusion part is, for example, a film such as polyethylene or polypropylene, and the metal part is, for example, aluminum foil. The protection layer is, for example, nylon or the like.

[0118] To prevent outside air from entering, adhesive films 4 are inserted between the exterior member 5 and each of the positive electrode lead 2 and the negative electrode lead 3. The material for this is, for example, polyethylene, polypropylene, or polyolefin resin.

[0119] The exterior member 5 further contains a nonaqueous electrolyte solution of the present invention. The nonaqueous electrolyte solution is impregnated into at least a part of the positive electrode active material layer, at least a part of the negative electrode active material layer 32, and at least a part of the separator, all of which are included in the electrode body 1. [Example]

[0120] The present invention will be explained in more detail below by showing synthesis examples, examples and comparative examples of the present invention, but the present invention is not limited to these examples.

[0121] [Silane compounds] (Synthesis Example 1) A flask equipped with a stirrer, dropping funnel, condenser, and thermometer was charged with 500 mL (700 mmol) of 1.4 mol / L vinylmagnesium chloride tetrahydrofuran solution and stirred at room temperature. 45.3 g (443 mmol) of ethynylbenzene was added dropwise and stirred at room temperature for 1 hour. Next, 37.7 g (233 mmol) of trichlorovinylsilane was added dropwise and stirred at room temperature for 2 hours. 123 g of 10% hydrochloric acid was added, and the aqueous phase was removed by separation. The resulting organic phase was subjected to simple distillation, yielding 32.7 g of bis(phenylethynyl)divinylsilane (PEDVS) as a fraction with a boiling point of 180-181°C / 0.4 kPa.

[0122] (Synthesis Example 2) A flask equipped with a stirrer, dropping funnel, condenser, and thermometer was charged with 154.8 g (400 mmol) of a 387 g / mol methylmagnesium chloride tetrahydrofuran solution and 120 mL of tetrahydrofuran, and the mixture was stirred at room temperature. 40.8 g (400 mmol) of ethynylbenzene was added dropwise and the mixture was stirred at room temperature for 1 hour. 28.2 g (200 mmol) of dichloromethylvinylsilane was then added dropwise and the mixture was stirred at room temperature for 2 hours. 70.4 g of 10% hydrochloric acid and 12.0 g of purified water were added, and the aqueous phase was removed by separation. The resulting organic phase was subjected to simple distillation, yielding 46.1 g of bis(phenylethynyl)methylvinylsilane (PEMVS) as a fraction with a boiling point of 179 °C / 0.3 kPa.

[0123] (Synthesis Example 3) A flask equipped with a stirrer, dropping funnel, condenser, and thermometer was charged with 24.4 g (63 mmol) of a 387 g / mol methylmagnesium chloride tetrahydrofuran solution and 19 mL of tetrahydrofuran and stirred at 50°C. 10.0 g (32 mmol) of 4-ethynylanisole was added dropwise and stirred at 50°C for 1 hour. 4.5 g (32 mmol) of dichloromethylvinylsilane was then added dropwise and stirred at 50°C for 2 hours. 15.0 g of purified water was added, and the aqueous phase was removed by separation. The organic phase was concentrated using an evaporator to obtain a solid crude product. The crude product was dissolved in 5.0 g of heated acetone and recrystallized to obtain 6.8 g of bis(4-methoxyphenylethynyl)methylvinylsilane (M-PEMVS).

[0124] (Synthesis Example 4) A flask equipped with a stirrer, dropping funnel, condenser, and thermometer was charged with 101.5 g (263 mmol) of a 387 g / mol methylmagnesium chloride tetrahydrofuran solution and stirred at 40 °C. 31.5 g (263 mmol) of 4-fluorophenylacetylene was added dropwise and stirred at 40 °C for 1 hour. 18.5 g (131 mmol) of dichloromethylvinylsilane was then added dropwise and stirred at 40 °C for 2 hours. 54.0 g of purified water was added, and the aqueous phase was removed by separation. The resulting organic phase was subjected to simple distillation, yielding 30.0 g of bis(4-fluorophenylethynyl)methylvinylsilane (F-PEMVS) as a fraction with a boiling point of 181 °C / 0.1 kPa.

[0125] Example 1 [Preparation of negative electrode] The negative electrode current collector was an electrolytic copper foil having a thickness of 15 μm, which contained 70 ppm by mass of carbon and 70 ppm by mass of sulfur.

[0126] KSC-7130 (silicon oxide particles containing Li2SiO3 and coated with a carbon layer; median diameter 6.5 μm, manufactured by Shin-Etsu Chemical Co., Ltd.) was prepared as silicon-based negative electrode active material particles. These silicon-based negative electrode active material particles were analyzed by XRD. Table 1 below shows the ratio A / B of the intensity A of the peak due to the Si(111) crystal plane (appearing near 2θ=28.4°) to the intensity B of the peak due to the Li2SiO3(111) crystal plane (appearing in the range of 2θ=17° to 21°). The XRD analysis showed that in the silicon-based negative electrode active material particles prepared in Example 1, Si had low crystallinity and was substantially amorphous.

[0127] The prepared silicon-based negative electrode active material particles, artificial graphite (median diameter 15 μm) as the carbon-based negative electrode active material, carbon nanotubes and carbon fine particles with a median diameter of approximately 50 nm as the negative electrode conductive additive, and sodium polyacrylate and carboxymethyl cellulose as the negative electrode binder were mixed in a dry mass ratio of 9.3:83.7:1:1:4:1, respectively, and then diluted with pure water to form a negative electrode mixture slurry.

[0128] The negative electrode mixture slurry was applied to the negative electrode current collector and dried in a vacuum atmosphere at 100° C. for 1 hour. After drying, the deposition amount (area density) of the negative electrode active material layer per unit area on one surface of the negative electrode was 7.0 mg / cm 2 It was.

[0129] [Preparation of non-aqueous electrolyte] Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed as a non-aqueous solvent, and lithium hexafluorophosphate (LiPF6) was dissolved as an electrolyte salt to prepare an electrolyte solution. In this case, the solvent composition was EC:DMC = 30:70 in volume ratio, and the content of the electrolyte salt was 1 mol / kg relative to the solvent.

[0130] The nonaqueous electrolyte solution of Example 1 was prepared by adding 1.0 mass %, 2.0 mass %, and 0.1 mass % of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and bis(phenylethynyl)divinylsilane (a silane compound represented by the above general formula (1); hereinafter, referred to as "PEDVS") as additives.

[0131] [Preparation of test coin batteries] Test coin cells were then assembled as follows. First, a 1 mm thick Li foil was punched out to a diameter of 16 mm and attached to an aluminum clad. The negative electrode obtained by the above method was punched out to a diameter of 15 mm, and placed opposite a Li foil with a separator interposed between them. The nonaqueous electrolyte obtained by the above method was then poured into a 2032 coin battery (diameter 20.0 mm, thickness 3.2 mm) which was a nonaqueous electrolyte secondary battery for the initial efficiency test.

[0132] [Measurement of initial efficiency] First, the coin battery for the initial efficiency test was charged (initial charge) in CCCV mode at a charge rate equivalent to 0.03 C. The CV was set to 0 V and the cut-off current was 0.04 mA. Next, CC discharge (initial discharge) was performed at a discharge rate of 0.03 C and a discharge cut-off voltage of 1.2 V.

[0133] When examining the initial charge-discharge characteristics, the initial efficiency was calculated using the formula: initial efficiency (%) = (initial discharge capacity / initial charge capacity) x 100.

[0134] [Manufacturing of non-aqueous electrolyte secondary batteries] Based on the initial data obtained, the positive electrode was designed so that the negative electrode utilization rate would be 95%. The utilization rate was calculated using the following formula from the positive and negative electrode capacities obtained with the Li counter electrode. Utilization rate = (positive electrode capacity - negative electrode loss) / (negative electrode capacity - negative electrode loss) x 100 Based on this design, a nonaqueous electrolyte secondary battery of Example 1 was manufactured.

[0135] [Discharge capacity retention rate after 500 cycles] As the cycle characteristics, the discharge capacity retention rate after 500 cycles was evaluated. First, to stabilize the battery, the nonaqueous electrolyte secondary battery of Example 1 was subjected to two charge-discharge cycles at 0.2 C in an atmosphere of 25°C, and the discharge capacity at the second cycle was measured. The cycle characteristics were calculated from the discharge capacity at the third cycle. Up to the 500th cycle, the battery was charged at 0.7 C and discharged at 0.5 C. The discharge capacity at the 500th cycle relative to the discharge capacity at the second cycle was calculated as the discharge capacity retention rate after 500 cycles. The charge voltage was 4.3 V, the discharge cut-off voltage was 2.5 V, and the charge cut-off rate was 0.07 C.

[0136] [Battery thickness increase rate (swelling evaluation)] When measuring the discharge capacity at the second cycle in the evaluation of cycle characteristics, the thickness of the expanded part of the battery was also measured. After that, charge and discharge were performed under the above conditions from the third cycle to the 500th cycle, and the thickness of the battery after 500 cycles was measured. Then, the increase rate of the battery thickness due to the increase in volume after 500 cycles was calculated based on the thickness of the battery after the second cycle.

[0137] The rate of increase in battery thickness was evaluated using a 543436 size battery (thickness 5.4 mm, width 34 mm, length 36 mm). The thickness was measured at the center of the widest area.

[0138] (Examples 2 to 6) Non-aqueous electrolyte solutions of Examples 2 to 6 were prepared in the same manner as in Example 1, except that the amount of PEDVS added as an additive was changed as shown in the following Table 1. In addition, non-aqueous electrolyte secondary batteries of Examples 2 to 6 were fabricated in the same manner as in Example 1, except that each non-aqueous electrolyte solution was used. The battery characteristics of the obtained batteries were evaluated in the same manner as in Example 1.

[0139] Example 7 A non-aqueous electrolyte solution of Example 7 was prepared in the same manner as in Example 1, except that the additive PEDVS was changed to bis(phenylethynyl)methylvinylsilane (a silane compound represented by the above general formula (1); hereinafter referred to as "PEMVS"). In addition, a non-aqueous electrolyte secondary battery of Example 7 was fabricated in the same manner as in Example 1, except that this non-aqueous electrolyte solution was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0140] (Examples 8 to 12) Non-aqueous electrolyte solutions of Examples 8 to 12 were prepared in the same manner as in Example 7, except that the amount of PEMVS added as an additive was changed as shown in the following Table 1. In addition, non-aqueous electrolyte secondary batteries of Examples 8 to 12 were fabricated in the same manner as in Example 1, except that each non-aqueous electrolyte solution was used. The battery characteristics of the obtained batteries were evaluated in the same manner as in Example 1.

[0141] (Examples 13 to 18) The silicon material (silicon-based negative electrode active material) was subjected to additional heat treatment to control the crystallinity of Si and Li2SiO3 and evaluate the battery characteristics. The temperature was adjusted in the range of 600 to 700°C.

[0142] The silicon-based negative electrode active material particles used in Examples 13 to 18 were analyzed by XRD in the same manner as the silicon-based negative electrode active material particles used in Example 1. Table 1 below shows the ratio A / B of the intensity A of the peak due to the Si(111) crystal plane (appearing near 2θ=28.4°) to the intensity B of the peak due to the Li2SiO3(111) crystal plane (appearing in the range of 2θ=17° to 21°) for each silicon-based negative electrode active material particle.

[0143] The crystallite size corresponding to the Si(111) crystal plane was calculated from the peak due to the Si(111) crystal plane using the Scherrer formula. The results are shown in Table 1 below.

[0144] From the results shown in Table 1, it was confirmed that increasing the heat treatment temperature promotes the crystallization of Si, which tends to deteriorate the battery characteristics.

[0145] In Examples 13 to 18, nonaqueous electrolyte secondary batteries were fabricated in the same manner as in Example 3, except that the silicon-based negative electrode active material that had been subjected to the additional heat treatment as described above was used. The battery characteristics of the resulting batteries were evaluated in the same manner as in Example 1.

[0146] Example 19 A non-aqueous electrolyte solution of Example 19 was prepared in the same manner as in Example 1, except that the additive PEDVS was changed to bis(4-methoxyphenylethynyl)methylvinylsilane (a silane compound represented by the above general formula (1); hereinafter referred to as "M-PEMVS"). In addition, a non-aqueous electrolyte secondary battery of Example 19 was fabricated in the same manner as in Example 1, except that this non-aqueous electrolyte solution was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0147] (Examples 20 to 24) Non-aqueous electrolyte solutions of Examples 20 to 24 were prepared in the same manner as in Example 19, except that the amount of additive M-PEMVS added was changed as shown in Table 1 below. In addition, non-aqueous electrolyte secondary batteries of Examples 20 to 24 were fabricated in the same manner as in Example 1, except that each non-aqueous electrolyte solution was used. The battery characteristics of the obtained batteries were evaluated in the same manner as in Example 1.

[0148] Example 25 A non-aqueous electrolyte solution of Example 25 was prepared in the same manner as in Example 1, except that the additive PEDVS was changed to bis(4-fluorophenylethynyl)methylvinylsilane (a silane compound represented by the above general formula (1); hereinafter referred to as "F-PEMVS"). In addition, a non-aqueous electrolyte secondary battery of Example 25 was fabricated in the same manner as in Example 1, except that this non-aqueous electrolyte solution was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0149] (Examples 26 to 30) Non-aqueous electrolyte solutions of Examples 26 to 30 were prepared in the same manner as in Example 25, except that the amount of the additive F-PEMVS added was changed as shown in Table 1 below. In addition, non-aqueous electrolyte secondary batteries of Examples 26 to 30 were fabricated in the same manner as in Example 1, except that each non-aqueous electrolyte solution was used. The battery characteristics of the obtained batteries were evaluated in the same manner as in Example 1.

[0150] (Comparative Example 1) A nonaqueous electrolyte solution of Comparative Example 1 was prepared in the same manner as in Example 1, except that PEDVS was not added as an additive. A nonaqueous electrolyte secondary battery of Comparative Example 1 was fabricated in the same manner as in Example 1, except that this nonaqueous electrolyte solution was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0151] [result] The evaluation results of the nonaqueous electrolyte secondary batteries obtained in Examples 1 to 30 and Comparative Example 1 are summarized in Table 1 below.

[0152] [Table 1]

[0153] The results shown in Table 1 show that the nonaqueous electrolyte secondary batteries of Examples 1 to 30, which were fabricated using a nonaqueous electrolyte solution containing the silane compound represented by formula (1), had higher discharge capacity retention rates after 500 cycles, i.e., superior cycle characteristics, than the nonaqueous electrolyte secondary battery of Comparative Example 1, which was fabricated using a nonaqueous electrolyte solution not containing the silane compound. It is also clear that the nonaqueous electrolyte secondary batteries of Examples 1 to 30 were able to suppress the increase in battery thickness, i.e., were able to suppress battery swelling, compared to the nonaqueous electrolyte secondary battery of Comparative Example 1.

[0154] Furthermore, a comparison of the results of Example 3 with those of Examples 13 to 18 reveals that the XRD peak intensity ratio A / B of silicon-based negative electrode active material particles is preferably 0.4 or more and 1.0 or less, the Si(111) crystallite size is preferably 5.0 nm or less, and it is particularly preferable that the Si be amorphous.

[0155] The present specification includes the following aspects. [1] a non-aqueous solvent; an electrolyte salt dissolved in the non-aqueous solvent; The following general formula (1) [ka] (In general formula (1), R 1 is an alkenyl group having 2 to 20 carbon atoms, and R 2 is a substituted or unsubstituted arylethynyl group having 8 to 20 carbon atoms, and R 3 is an alkyl group having 1 to 20 carbon atoms, and R 4 is an alkynyl group having 2 to 20 carbon atoms. Furthermore, l and m each independently represent an integer of 1 to 3, n represents an integer of 0 to 2, and l, m, and n are integers that satisfy the relationship 2≦l+m+n≦4. and a silane compound represented by the formula: A non-aqueous electrolyte comprising: [2] The silane compound represented by the general formula (1) is a compound represented by the general formula (1) R 2 The non-aqueous electrolyte solution according to [1], wherein the substituted arylethynyl group is an arylethynyl group having 8 to 20 carbon atoms in which some or all of the hydrogen atoms of the aryl group have been substituted with a hydrocarbon group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. [3] The nonaqueous electrolyte solution according to [1] or [2], wherein the silane compound represented by the general formula (1) is such that l and m in the general formula (1) each independently represent an integer of 1 to 3, n represents an integer of 0 to 1, and l, m, and n are integers that satisfy l+m+n=4. [4] The non-aqueous electrolyte solution according to any one of [1] to [3], wherein the content of the silane compound in the non-aqueous electrolyte solution is 0.1% by mass to 5.0% by mass. [5] A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte solution, A non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte solution is the non-aqueous electrolyte solution according to any one of [1] to [4]. [6] The nonaqueous electrolyte secondary battery according to [5], wherein the negative electrode contains negative electrode active material particles, the negative electrode active material particles contain Li2SiO3 and silicon oxide particles coated with a carbon layer, and the Li2SiO3 includes crystalline Li2SiO3. [7] The negative electrode active material particles have a peak attributable to a Si(111) crystal plane obtained by X-ray diffraction using Cu-Kα radiation before charging and discharging the negative electrode active material particles, the crystallite size corresponding to the crystal plane is 5.0 nm or less, and the ratio A / B of the intensity A of the peak attributable to the Si(111) crystal plane to the intensity B of the peak attributable to the Li2SiO3(111) crystal plane satisfies the following formula (2): 0.4≦A / B≦1.0 (2) The non-aqueous electrolyte secondary battery according to [6], which satisfies the above.

[0156] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0157] 1...electrode body, 2...positive electrode lead, 3...negative electrode lead, 4...adhesive film, 5...exterior member, 10...lithium ion secondary battery, 30...negative electrode, 31...negative electrode current collector, 32...negative electrode active material layer.

Claims

1. a non-aqueous solvent; an electrolyte salt dissolved in the non-aqueous solvent; The following general formula (1) 【Chemical 1】 (In general formula (1), R １ is an alkenyl group having 2 to 20 carbon atoms, and R ２ is a substituted or unsubstituted arylethynyl group having 8 to 20 carbon atoms, and R ３ is an alkyl group having 1 to 20 carbon atoms, and R ４ is an alkynyl group having 2 to 20 carbon atoms. In addition, l represents an integer of 1 or 2, m represents an integer of 2 or 3, n represents an integer of 0 or 1, and l, m, and n are integers that satisfy the relationship 3≦l+m+n≦4. and a silane compound represented by the formula: A non-aqueous electrolyte solution for a non-aqueous electrolyte secondary battery, comprising:

2. The silane compound represented by the general formula (1) is represented by R ２ The nonaqueous electrolyte solution for a nonaqueous electrolyte secondary battery according to claim 1, wherein the substituted arylethynyl group is an arylethynyl group having 8 to 20 carbon atoms in which some or all of the hydrogen atoms of the aryl group have been substituted with a hydrocarbon group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

3. 2. The nonaqueous electrolyte solution for a nonaqueous electrolyte secondary battery according to claim 1, wherein the silane compound represented by the general formula (1) is such that in the general formula (1), l represents an integer of 1 or 2, m represents an integer of 2 or 3, n represents an integer of 0 or 1, and l, m, and n are integers that satisfy l + m + n = 4.

4. The silane compound represented by the general formula (1) is a non-aqueous electrolyte solution for a non-aqueous electrolyte secondary battery according to claim 3, characterized in that in the general formula (1), l represents an integer of 1 or 2, m is 2, n represents an integer of 0 or 1, and l, m, and n are integers that satisfy l + m + n = 4.

5. 2. The non-aqueous electrolyte solution for a non-aqueous electrolyte secondary battery according to claim 1, wherein the content of the silane compound in the non-aqueous electrolyte solution is 0.1% by mass to 5.0% by mass.

6. A non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte solution, A non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte solution is the non-aqueous electrolyte solution for non-aqueous electrolyte secondary batteries according to any one of claims 1 to 5.

7. The negative electrode includes negative electrode active material particles, and the negative electrode active material particles include Li ２ SiO ３ and containing silicon oxide particles coated with a carbon layer, ２ SiO ３ 7. The non-aqueous electrolyte secondary battery according to claim 6, wherein the electrolyte is crystalline.

8. The negative electrode active material particles have a peak attributable to a Si (111) crystal plane obtained by X-ray diffraction using Cu-Kα radiation before charging and discharging the negative electrode active material particles, and the crystallite size corresponding to the crystal plane is 5.0 nm or less, and Li ２ SiO ３ The ratio A / B of the intensity A of the peak due to the Si (111) crystal plane to the intensity B of the peak due to the (111) crystal plane is expressed by the following formula (2): 0.4≦A / B≦1.0 (2) 8. The nonaqueous electrolyte secondary battery according to claim 7, wherein the above-mentioned condition is satisfied.

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