Non-aqueous electrolyte secondary battery

Abstract

The present invention is a non-aqueous electrolyte secondary battery including: a negative electrode containing a negative electrode active material having negative electrode active material particles; a positive electrode; and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte salt, the secondary battery being characterized in that the negative electrode active material particles include an amorphous low-valence nanosilicon oxide having a valence of 3 or less, and the non-aqueous electrolyte solution contains a fluorosilane compound and a nitrile compound. Due to said feature, provided is a non-aqueous electrolyte secondary battery in which cycle characteristics are improved and an increase in internal resistance is suppressed.

Description

Nonaqueous electrolyte secondary battery

[0001] This invention relates to a non-aqueous electrolyte secondary battery.

[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 lifespan. In response to these market demands, development is progressing on secondary batteries that are particularly small, lightweight, and capable of achieving high energy density. These secondary batteries are being considered not only for small electronic devices but also for large electronic devices such as automobiles, and for power storage systems such as those found in homes.

[0003] Among these, lithium-ion secondary batteries are particularly promising because they are easy to miniaturize and increase capacity, and they can achieve a higher energy density than lead-acid batteries and nickel-cadmium batteries.

[0004] Lithium-containing metal oxides are commonly used as the positive electrode active material in the positive electrode of the aforementioned lithium-ion secondary battery. For example, composite oxides of metals such as nickel, cobalt, aluminum, and manganese with lithium are used. High-nickel positive electrode active materials containing a high concentration of nickel have the advantage of enabling high-capacity batteries compared to existing lithium-cobalt oxides.

[0005] Furthermore, as the negative electrode active material contained in the negative electrode of the lithium-ion secondary battery, materials capable of intercalating (inserting) and releasing lithium ions are generally used. For example, silicon-based active material particles such as natural graphite, artificial graphite, hard carbon, and soft carbon; silicon particles (Si), silicon compound particles containing oxygen-containing silicon compounds (silicon oxide particles, SiOx), lithium, and silicon compound particles containing oxygen-containing silicon compounds (lithium-silicon oxide particles, Li-SiOx) are used. Among these, silicon compound particles containing oxygen-containing silicon compounds have the advantage of enabling high-capacity batteries compared to carbon-based active material particles.

[0006] On the other hand, high-nickel-based cathode active materials have a drawback in that their cycle characteristics are poor because the surface structure of the cathode is weak, and the resistance increases when charge and discharge are repeated. In addition, for a negative electrode containing SiO₂, the negative electrode potential at the end of discharge becomes higher than that of a negative electrode containing only a carbon-based active material. Therefore, when a negative electrode containing SiO₂ is used, the positive electrode potential at the end of discharge increases, accelerating the degradation of the positive electrode.

[0007] As a technique for improving the cycle characteristics of a lithium-ion secondary battery, a method of adding an additive has been reported. For example, a method of adding a monofluorosilane compound to an electrolyte (Patent Documents 1 and 2) has been reported.

[0008] Japanese Patent Application Laid-Open No. 2018-125287 International Publication WO2022 / 070312

[0009] However, in the method of adding the above monofluorosilane compound, there is still room for further improvement in terms of improving cycle characteristics. Also, from the perspective of suppressing the increase in internal resistance, it has not reached a sufficient level.

[0010] The present invention has been made in view of the above problems, and an object thereof is to provide a non-aqueous electrolyte secondary battery having improved cycle characteristics and suppressed increase in internal resistance.

[0011] Therefore, the present invention relates to a non-aqueous electrolyte secondary battery including a negative electrode containing a negative electrode active material having negative electrode active material particles, a positive electrode, and a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte salt, wherein the negative electrode active material particles contain a trivalent or lower amorphous low-valence nanosilicon oxide, and the non-aqueous electrolyte has the following general formula (1): SiR １ ａ R ２ ｂ R ３ ｃ R ４ ｄ (1) (In the general formula (1), R １ , R ２ and R ３ are each independently an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an alkynyl group having 2 to 20 carbon atoms, and R ４is a fluorine atom. Also, a, b, and c each independently represent integers from 0 to 3, and d represents an integer from 1 to 3, and a, b, c, and d are integers that satisfy a + b + c + d = 4.) A fluorosilane compound represented by the following general formula (2) R ５ -CN (2) (In general formula (2), R ５ (This is an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms.) Or, the following general formula (3) NC-R ６ -CN (3) (In general formula (3), R ６ The present invention provides a non-aqueous electrolyte secondary battery characterized by containing a nitrile compound represented by (where is an alkylene group having 1 to 20 carbon atoms).

[0012] In a non-aqueous electrolyte secondary battery, the fluorosilane compound and the nitrile compound decompose on the electrode surface during charging and discharging to form a high-quality film. In addition, the inclusion of amorphous low-valence nanosilicon oxides with a valency of 3 or less in the negative electrode active material particles improves cycle characteristics and suppresses an increase in internal resistance.

[0013] In this case, it is preferable that d of the fluorosilane compound represented by the general formula (1) is 1.

[0014] By setting d to 1, the battery characteristics can be improved more effectively.

[0015] Furthermore, it is preferable that the non-aqueous electrolyte contains a halogenated cyclic carbonate ester.

[0016] Thus, the presence of halogenated cyclic carbonate esters in the non-aqueous electrolyte allows for the formation of a stable film on the surface of the negative electrode active material during charging and discharging, particularly during charging.

[0017] Furthermore, in this case, when the content of halogenated cyclic carbonate in the non-aqueous electrolyte is A by mass%, the content of the fluorosilane compound represented by general formula (1) is B by mass%, and the content of the nitrile compound represented by general formula (2) or (3) is C by mass%, it is preferable that the ratio of A to B is 0.01 ≤ A / B ≤ 300, and the ratio of A to C is 0.01 ≤ A / C ≤ 300.

[0018] By adopting this ratio, battery characteristics can be improved more effectively.

[0019] Furthermore, it is preferable that the low-valence nanosilicon oxide is dispersed in porous carbon.

[0020] The electrolyte used in the non-aqueous electrolyte secondary battery of the present invention is particularly suitable when negative electrode active material particles having a structure in which low-valence nanosilicon oxide is dispersed in porous carbon are used.

[0021] Furthermore, the positive electrode contains a positive electrode active material, and the positive electrode active material has lithium and a transition metal element as shown in the following general formula (4) Li ｘ Ni ｌ M1 ｍ M2 ｎ O ２ (4) Preferably, the composite oxide is represented by the following formula: (In general formula (4), M1 and M2 are metallic elements. x represents 0.05 ≤ x ≤ 1.10. l represents 0.80 ≤ l ≤ 0.95, and l, m, and n satisfy l + m + n = 1.)

[0022] The electrolyte used in the non-aqueous electrolyte secondary battery of the present invention is particularly suitable when such a positive electrode is used.

[0023] The non-aqueous electrolyte secondary battery of the present invention can achieve good cycle characteristics and low internal resistance.

[0024] This is a schematic exploded view showing an example of a non-aqueous electrolyte secondary battery of the present invention. This is a schematic cross-sectional view showing an example of a negative electrode that the non-aqueous electrolyte secondary battery of the present invention may have.

[0025] As a result of diligent research to achieve the above objective, the inventors of the present invention discovered that the above objective can be achieved by using a negative electrode active material containing amorphous low-valence nanosilicon oxide with a valency of 3 or less, and a non-aqueous electrolyte containing a fluorosilane compound and a nitrile compound, and thus completed the present invention.

[0026] The present invention will be described in detail below, but is not limited thereto. The non-aqueous electrolyte secondary battery of the present invention comprises a negative electrode containing a negative electrode active material having negative electrode active material particles, a positive electrode, and a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte salt, wherein the negative electrode active material particles contain amorphous low-valence nanosilicon oxide with a valency of 3 or less, and the non-aqueous electrolyte contains the following general formula (1) SiR １ ａ R ２ ｂ R ３ ｃ R ４ ｄ (1) (In general formula (1), R １ , R ２ and R ３ Each of these is independently an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an alkynyl group having 2 to 20 carbon atoms, and R ４ is a fluorine atom. Also, a, b, and c each independently represent integers from 0 to 3, and d represents an integer from 1 to 3, and a, b, c, and d are integers that satisfy a + b + c + d = 4.) A fluorosilane compound represented by the following general formula (2) R ５ -CN (2) (In general formula (2), R ５ (This is an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms.) Or, the following general formula (3) NC-R ６ -CN (3) (In general formula (3), R ６ This is a non-aqueous electrolyte secondary battery characterized by containing a nitrile compound represented by (where is an alkylene group having 1 to 20 carbon atoms).

[0027] [Non-aqueous electrolyte secondary battery] The non-aqueous electrolyte secondary battery of the present invention comprises a positive electrode and a negative electrode in addition to a non-aqueous electrolyte.

[0028] The following describes the non-aqueous electrolytes that can be provided in the non-aqueous electrolyte secondary battery of the present invention.

[0029] [Non-aqueous electrolyte] The non-aqueous electrolyte of the present invention contains a fluorosilane compound represented by the following general formula (1) (hereinafter referred to as "compound (1)"). SiR１ ａ R ２ ｂ R ３ ｃ R ４ ｄ (1) (In general formula (1), R １ , R ２ and R ３ Each of these is independently an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an alkynyl group having 2 to 20 carbon atoms, and R ４ (where a is a fluorine atom. Also, a, b, and c each independently represent integers between 0 and 3, d represents an integer between 1 and 3, and a, b, c, and d are integers satisfying a + b + c + d = 4.)

[0030] Compound (1) will be described in more detail below.

[0031] In general formula (1), R １ , R ２ and R ３ Each of these is independently an alkyl group having 1 to 20 carbon atoms, preferably 1 to 15, more preferably 1 to 10 carbon atoms, or an alkenyl group having 2 to 20 carbon atoms, preferably 2 to 15, more preferably 2 to 10 carbon atoms, or an alkynyl group having 2 to 20 carbon atoms, preferably 2 to 15, more preferably 2 to 10 carbon atoms.

[0032] R １ , R ２ and R ３ Specific examples of alkyl groups include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, and decyl groups; branched alkyl groups such as isopropyl, isobutyl, sec-butyl, tert-butyl, texyl, and 2-ethylhexyl groups; and cyclic alkyl groups such as cyclopentyl and cyclohexyl groups.

[0033] Among these, R １ , R ２ and R ３From the viewpoint of sufficiently improving battery characteristics, the alkyl group is preferably a methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, or n-octyl group, with the methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, or n-hexyl group being even more preferred.

[0034] R １ , R ２ and R ３ Specific examples of alkenyl groups include linear alkenyl groups such as vinyl group, n-propenyl group, n-butenyl group, n-pentenyl group, n-hexenyl group, n-heptenyl group, n-octenyl group, n-nonenyl group, n-decenyl group, n-undecenyl group, and n-dodecenyl group; and branched alkenyl groups such as isopropenyl group, isobutenyl group, isopentenyl group, isohexenyl group, isoheptenyl group, isooctenyl group, isononyl group, isodecenyl group, and isoundecyl group.

[0035] Among these, R １ , R ２ and R ３ From the viewpoint of sufficiently improving battery characteristics, vinyl groups, n-propenyl groups, n-butenyl groups, n-pentenyl groups, n-hexenyl groups, n-heptenyl groups, and n-octenyl groups are preferred as the alkenyl groups, and vinyl groups, n-propenyl groups, n-butenyl groups, n-pentenyl groups, and n-hexenyl groups are even more preferred.

[0036] R １ , R ２ and R ３Specific examples of alkynyl groups include linear alkynyl groups such as ethynyl group, 1-propynyl group, 1-butynyl group, 1-pentynyl group, 1-hexynyl group, 1-heptynyl group, 1-octinyl group, 1-noninyl group, 1-decynyl group, 1-undecynyl group, 1-dodecynyl group, phenylethynyl group, 3-methylphenylethynyl group, 3-methylphenylethynyl group, and 4-methylphenylethynyl group, as well as branched alkynyl groups such as 3-methyl-1-butynyl group, 3,3-dimethyl-1-butynyl group, 3-methyl-1-pentynyl group, 4-methyl-1-pentynyl group, 3,3-dimethyl-1-pentynyl group, 3,4-methyl-1-pentynyl group, and 4,4-dimethyl-1-pentynyl group.

[0037] Among these, R １ , R ２ and R ３ From the viewpoint of sufficiently improving battery characteristics, the alkynyl group is preferably ethynyl, 1-propynyl, 1-butynyl, 1-pentynyl, 1-hexynyl, 1-heptynyl, 1-octinyl, or phenylethynyl, and more preferably ethynyl, 1-propynyl, 1-butynyl, 1-pentynyl, 1-hexynyl, or phenylethynyl.

[0038] In general formula (1), R ４ This is a fluorine atom.

[0039] Furthermore, in general formula (1), a, b, and c each independently represent integers from 0 to 3, d represents an integer from 1 to 3, and a, b, c, and d are integers that satisfy a + b + c + d = 4.

[0040] From the viewpoint of sufficiently improving battery characteristics, d is preferably 1 or 2, and more preferably 1.

[0041] Specific examples of compound (1) include trimethylfluorosilane, dimethylethylfluorosilane, dimethylpropylfluorosilane, dimethylbutylfluorosilane, dimethylpentylfluorosilane, dimethylhexylfluorosilane, dimethylheptylfluorosilane, dimethyloctylfluorosilane, dimethyldifluorosilane, methylethyldifluorosilane, methylpropyldifluorosilane, methylbutyldifluorosilane, methylpentyldifluorosilane, methylhexyldifluorosilane, methylheptyldifluorosilane, Methyloctyldifluorosilane, methyltrifluorosilane, ethyltrifluorosilane, propyltrifluorosilane, butyltrifluorosilane, pentyltrifluorosilane, hexyltrifluorosilane, heptyltrifluorosilane, octyltrifluorosilane, dimethylvinylfluorosilane, dimethyl-n-propenylfluorosilane, dimethyl-n-butenylfluorosilane, dimethyl-n-pentenylfluorosilane, dimethyl-n-hexenylfluorosilane, dimethyl-n-heptenylfluorosilane, dimethyl-n- Octenyl fluorosilane, methyl vinyl difluorosilane, methyl-n-propenyl difluorosilane, methyl-n-butenyl difluorosilane, methyl-n-pentenyl difluorosilane, methyl-n-hexenyl difluorosilane, methyl-n-heptenyl difluorosilane, methyl-n-octenyl difluorosilane, vinyl trifluorosilane, n-propenyl trifluorosilane, n-butenyl trifluorosilane, n-pentenyl trifluorosilane, n-hexenyl trifluorosilane, n-heptenyl trifluorosilane, n - Octenyltrifluorosilane, dimethylethynylfluorosilane, dimethyl-1-propynylfluorosilane, dimethyl-1-butynylfluorosilane, dimethyl-1-pentynylfluorosilane, dimethyl-1-hexynylfluorosilane, dimethyl-1-heptynylfluorosilane, dimethyl-1-octinylfluorosilane, methylethynyldifluorosilane, methyl-1-propynyldifluorosilane, methyl-1-butynyldifluorosilane, methyl-1-pentynyldifluorosilane, methyl-1-hexynyldifluorosilane,Examples include fluorosilane compounds such as methyl-1-heptinyldifluorosilane and methyl-1-octinyldifluorosilane.

[0042] From the viewpoint of sufficiently improving battery characteristics, the content of compound (1) in the non-aqueous electrolyte is preferably 0.01% to 10.00% by mass, more preferably 0.01% to 5.00% by mass, and even more preferably 0.01% to 2.00% by mass.

[0043] The non-aqueous electrolyte of the present invention contains a nitrile compound represented by the following general formula (2) (hereinafter referred to as "compound (2)") or the following general formula (3) (hereinafter referred to as "compound (3)"). ５ -CN (2) (In general formula (2), R ５ (This is an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms.) NC-R ６ -CN (3) (In general formula (3), R ６ (This refers to an alkylene group having 1 to 20 carbon atoms.)

[0044] Compounds (2) and (3) will be described in more detail below.

[0045] In general formula (2), R ５ This is an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10, more preferably 1 to 5 carbon atoms, or an alkenyl group having 2 to 20 carbon atoms, preferably 2 to 10, more preferably 2 to 5 carbon atoms.

[0046] R ５ Specific examples of alkyl groups include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, and decyl groups; branched alkyl groups such as isopropyl, isobutyl, sec-butyl, tert-butyl, texyl, and 2-ethylhexyl groups; and cyclic alkyl groups such as cyclopentyl and cyclohexyl groups.

[0047] Among these, R ５From the viewpoint of sufficiently improving battery characteristics, methyl, ethyl, n-propyl, n-butyl, and n-pentyl groups are preferred as alkyl groups, with methyl, ethyl, and n-propyl groups being even more preferred.

[0048] R ５ Specific examples of alkenyl groups include linear alkenyl groups such as vinyl group, n-propenyl group, n-butenyl group, n-pentenyl group, n-hexenyl group, n-heptenyl group, n-octenyl group, n-nonenyl group, n-decenyl group, n-undecenyl group, and n-dodecenyl group; and branched alkenyl groups such as isopropenyl group, isobutenyl group, isopentenyl group, isohexenyl group, isoheptenyl group, isooctenyl group, isononyl group, isodecenyl group, and isoundecyl group.

[0049] Among these, R ５ From the viewpoint of sufficiently improving battery characteristics, vinyl groups, n-propenyl groups, n-butenyl groups, and n-pentenyl groups are preferred as the alkenyl groups, with vinyl groups and n-propenyl groups being even more preferred.

[0050] Specific examples of compound (2) include nitrile compounds such as acetonitrile, propionitrile, butyronitrile, valeronitrile, isobutyronitrile, isovaleronitrile, 2-methylbutyronitrile, pivalonitrile, isocapronitrile, acrylonitrile, methacrylonitrile, crotononitrile, and 2-methyl-2-butenenitrile.

[0051] In general formula (3), R ６ This is an alkylene group having 1 to 20 carbon atoms, preferably 1 to 10, and more preferably 1 to 5 carbon atoms.

[0052] R ６Specific examples of alkylene groups include linear alkylene groups such as methylene, dimethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, and decamethylene; and branched alkylene groups such as 1-methyl(dimethylene), 1-methyl(trimethylene), 2-methyl(trimethylene), 1-methyl(tetramethylene), and 2-methyl(tetramethylene).

[0053] Among these, R ６ From the viewpoint of sufficiently improving battery characteristics, methylene groups, dimethylene groups, trimethylene groups, tetramethylene groups, pentamethylene groups, and hexamethylene groups are preferred as alkylene groups, and methylene groups, dimethylene groups, trimethylene groups, and tetramethylene groups are even more preferred.

[0054] Specific examples of compound (3) include dinitrile compounds such as malononitrile, succinonitrile, glutanonitrile, 2-methylglutanonitrile, adiponitrile, tert-butylmalononitrile, pimeronitrile, tetramethylsuccinonitrile, suberonitrile, sebaconitrile, and undecadinitrile.

[0055] From the viewpoint of sufficiently improving battery characteristics, the content of compound (2) and compound (3) in the non-aqueous electrolyte is preferably 0.01% to 10.00% by mass, more preferably 0.01% to 5.00% by mass, and even more preferably 0.01% to 2.00% by mass.

[0056] The non-aqueous electrolyte of the present invention further comprises compound (1) and compound (2) or compound (3) above, a non-aqueous solvent, and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte of the present invention may also contain other materials as additives.

[0057] Specific 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, or tetrahydrofuran. Among these, it is desirable to use at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate from the viewpoint of obtaining better properties. Furthermore, 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 properties and ion mobility of the electrolyte salt are improved, and more advantageous properties can be obtained.

[0058] When using an alloy-based anode containing silicon-based anode material, it is particularly desirable to include at least one of the following as a non-aqueous solvent: a halogenated linear carbonate ester or a halogenated cyclic carbonate ester. This allows for the formation of a stable film on the surface of the anode active material during charging and discharging, especially during charging. Here, a halogenated linear carbonate ester is a linear carbonate ester having halogen as a constituent element (at least one hydrogen atom is substituted by halogen). A halogenated cyclic carbonate ester is a cyclic carbonate ester having halogen as a constituent element (i.e., at least one hydrogen atom is substituted by halogen).

[0059] While the type of halogen is not particularly limited, fluorine is preferred from the viewpoint of forming a higher quality coating than other halogens. Furthermore, a higher number of halogens is desirable because it results in a more stable coating and reduces the decomposition reaction of the electrolyte.

[0060] Specific examples of halogenated chain carbonate esters include fluoromethylmethyl carbonate and difluoromethylmethyl carbonate. Specific examples of halogenated cyclic carbonate esters include 4-fluoro-1,3-dioxolan-2-one and 4,5-difluoro-1,3-dioxolan-2-one.

[0061] When the content of halogenated cyclic carbonate ester in the non-aqueous electrolyte is A by mass%, the content of the fluorosilane compound represented by general formula (1) is B by mass%, and the content of the nitrile compound represented by general formula (2) or (3) is C by mass%, from the viewpoint of sufficiently improving battery characteristics, it is preferable that the ratio of A to B is 0.01 ≤ A / B ≤ 300 and the ratio of A to C is 0.01 ≤ A / C ≤ 300, and it is even more preferable that the ratio of A to B is 0.01 ≤ A / B ≤ 200 and the ratio of A to C is 0.01 ≤ A / C ≤ 200.

[0062] The electrolyte salt may contain one or more types of light metal salts, such as lithium salts. A specific example of a lithium salt is lithium hexafluoride phosphate (LiPF). ６ ), lithium tetrafluoroborate (LiBF ４ ), lithium perchlorate (LiClO ４ Examples include lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0063] From the viewpoint of obtaining high ionic conductivity, the electrolyte salt content is preferably 0.5 mol / kg to 2.5 mol / kg, more preferably 0.8 mol / kg to 2.0 mol / kg, and even more preferably 0.8 mol / kg to 1.5 mol / kg, relative to the non-aqueous solvent.

[0064] The non-aqueous electrolyte of the present invention may contain, for example, cyclic carbonate esters having unsaturated carbon bonds, sultones (cyclic sulfonic acid esters), and sulfonic anhydrides as additives other than compound (1), compound (2), and compound (3).

[0065] Cyclic carbonate esters having unsaturated carbon bonds can be included in the non-aqueous electrolyte of the present invention from the viewpoint of stable film formation on the negative electrode surface during charging and discharging. Specific examples of cyclic carbonate esters having unsaturated carbon bonds include vinylene carbonate, 4-vinyl-1,3-dioxolan-2-one, 4-methyl-1,3-dioxol-2-one, and 4,5-dimethyl-1,3-dioxol-2-one.

[0066] Furthermore, sultones can be included from the viewpoint of improving the chemical stability of the battery. Specific examples of sultones include 1,3-propanesultone, 1,4-butanesultone, and 1-propene-1,3-sultone.

[0067] Furthermore, sulfonic anhydrides can be included from the viewpoint of improving the chemical stability of the electrolyte. Specific examples of sulfonic anhydrides include methanesulfonic anhydride, trifluoromethanesulfonic anhydride, benzenesulfonic anhydride, and 1,3-propanedisulfonic anhydride.

[0068] The positive and negative electrodes that the non-aqueous electrolyte secondary battery of the present invention may have will be described below.

[0069] [Positive electrode] The positive electrode is configured such that, for example, a positive electrode active material layer is present on both sides or one side of the positive electrode current collector.

[0070] [Positive electrode current collector] The positive electrode current collector is formed from a conductive material such as aluminum.

[0071] [Positive Electrode Active Material Layer] The positive electrode active material layer contains one or more positive electrode active materials capable of intercalating and deintercalating lithium ions, and may also contain other materials such as binders, conductive additives, and dispersants depending on the design. In this case, the binder and conductive additive can be the same as those used for the negative electrode binder and negative electrode conductive additive described later.

[0072] Examples of lithium-containing compounds that provide both high battery capacity and excellent cycle characteristics include composite oxides having lithium and a transition metal element, or phosphate compounds having lithium and a transition metal element.

[0073] Nickel, iron, manganese, and cobalt are preferred transition metal elements, and the lithium-containing compound is a compound having at least one of these transition metal elements.

[0074] Examples of the chemical formulas of lithium-containing compounds include Li ａ１ M3O ２ Or Li ｂ１ M4PO４ It is represented by the formula. In the formula, M3 and M4 represent at least one or more metal elements. The values of a1 and b1 represent different values depending on the battery charge and discharge state, but generally satisfy 0.05 ≤ a1 ≤ 1.10 and 0.05 ≤ b1 ≤ 1.10.

[0075] Specific examples of the composite oxide having lithium and a transition metal element include, for example, lithium cobalt composite oxide (Li ｘ CoO ２ ), lithium nickel composite oxide (Li ｘ NiO ２ ), lithium nickel cobalt aluminum composite oxide (NCA), lithium nickel cobalt manganese composite oxide (NCM), and the like.

[0076] As the positive electrode active material, the following general formula (4) having lithium, nickel and a metal element: Li ｘ Ni ｌ M1 ｍ M2 ｎ O ２ (4) (In the general formula (4), M1 and M2 are metal elements. x represents 0.05 ≤ x ≤ 1.10. l represents 0.80 ≤ l ≤ 0.95, and l, m and n satisfy l + m + n = 1.) The composite oxide represented by is preferable. By using these positive electrode materials, a high battery capacity can be obtained.

[0077] In the general formula (4), M1 and M2 are metal elements. Specific examples of the metal element include cobalt, manganese, aluminum and the like. x represents 0.05 ≤ x ≤ 1.10. l represents 0.80 ≤ l ≤ 0.95, and l, m and n are numbers that satisfy l + m + n = 1.

[0078] Specific examples of the phosphate compound having lithium and a transition metal element include, for example, lithium iron phosphate compound (LiFePO ４ ), lithium iron manganese phosphate compound (LiFe １－ｕ Mn ｕ [[ID=QQ]] ４ (where 0 < u < 1), etc. By using these positive electrode materials, excellent cycle characteristics can be obtained.

[0079] ​[Negative electrode] The negative electrode has a configuration such as having a negative electrode active material layer on top of a negative electrode current collector. This negative electrode active material layer may be provided on both sides or only on one side of the negative electrode current collector.

[0080] [Negative Electrode Current Collector] The negative electrode current collector is made of a material that is both highly conductive and has excellent mechanical strength. Examples of conductive materials that can be used for the negative electrode current collector include copper (Cu) and nickel (Ni). It is preferable that this conductive material does not form intermetallic compounds with lithium (Li).

[0081] 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 copper (Cu) and nickel (Ni). In particular, when there is an active material layer that expands during charging, the inclusion of the above elements in the current collector has the effect of suppressing electrode deformation including the current collector. The content of the above elements is not particularly limited, but from the viewpoint of obtaining a higher deformation suppression effect, it is preferable that each be 100 ppm by mass or less. Such deformation suppression effect can further improve cycle characteristics.

[0082] Furthermore, the surface of the negative electrode current collector may or may not be roughened. Examples of roughened negative electrode current collectors include metal foil that has been electrolytically treated, embossed, or chemically etched. Examples of unroughened negative electrode current collectors include rolled metal foil.

[0083] [Negative Electrode Active Material Layer] The negative electrode active material layer contains a negative electrode active material capable of intercalating (inserting) and releasing lithium ions, and the negative electrode active material contains negative electrode active material particles. Generally, negative electrode active material particles include, for example, carbon-based active material particles such as natural graphite, artificial graphite, hard carbon, and soft carbon; silicon particles, silicon compound particles containing silicon compounds containing oxygen (silicon oxide particles), lithium, and silicon compound particles containing silicon compounds containing oxygen (lithium-silicon oxide particles). Among these, the negative electrode active material particles used in the non-aqueous electrolyte secondary battery of the present invention contain amorphous low-valence nanosilicon oxides of trivalent or less.

[0084] In materials containing amorphous low-valent nanosilicon oxides with a valency of three or less, it is particularly preferable that the low-valent nanosilicon oxides are dispersed in porous carbon. That is, it is preferable to use amorphous low-valent nanosilicon oxides with a valency of three or less deposited in porous carbon as a silicon-based anode material.

[0085] The negative electrode active material particles of the present invention contain amorphous low-valent nanosilicon oxide (silicon-based negative electrode active material) with a valency of 3 or less, which is a silicon oxide material containing an oxygen-containing silicon compound. ｘ The composition ratio of silicon to oxygen that constitutes the silicon oxide, x, is preferably a number that satisfies 0.8 ≤ x ≤ 1.2 from the viewpoint of cycle characteristics and the resistance of silicon oxide. ｘ A composition where x is close to 1 is preferable because it yields better cycle characteristics.

[0086] As described above, the negative electrode active material is preferably amorphous low-valence nanosilicon oxide deposited in porous carbon. The amorphous nanosilicon oxide includes states where SiOy:y < 1.0. The general SiOx mentioned above is Si ４＋ Although the irreversible component is present, amorphous low-valence nanosilicon oxides contain states where SiOy:y < 1.0, thus maintaining a lower irreversible capacity than typical SiOx. Furthermore, the Si-O bond can suppress the decomposition of the electrolyte, making it possible to reduce the accumulation of SEI (Solid Electrolyte Interphase) on the surface.

[0087] The amorphous low-valent nanosilicon oxide must include those that are substantially trivalent or less, from the viewpoint of reducing irreversible capacity.

[0088] Furthermore, the amorphous low-valence nanosilicon oxide may be dispersed inside a porous carbon structure. In such a case, the presence of the porous carbon structure can mitigate the adverse effects of expansion of the low-valence nanosilicon oxide inside.

[0089] It should be noted that the composition of the silicon compound in this invention does not necessarily mean 100% purity, and may contain trace amounts of impurity elements.

[0090] The silicon compound preferably contains as little crystalline Si as possible. By minimizing the amount of crystalline Si, it is possible to prevent excessive reactivity with the electrolyte, and as a result, prevent deterioration of battery characteristics. A substantially amorphous form is preferred.

[0091] By including such negative electrode active material particles in the negative electrode, higher capacity and improved cycle characteristics can be achieved, while battery swelling can be sufficiently suppressed.

[0092] The negative electrode active material layer may contain a mixed negative electrode active material material comprising the silicon-based negative electrode active material and the carbon-based negative electrode active material. This reduces the electrical resistance of the negative electrode active material layer and alleviates the expansion stress associated with charging.

[0093] The negative electrode active material layer contains a negative electrode active material capable of intercalating and releasing lithium ions, and from a battery design perspective, it may also contain other materials such as a negative electrode binder and a conductive additive.

[0094] As the negative electrode binder, one or more of the following can be used: polymer materials, synthetic rubber, etc. Examples of polymer materials include polyvinylidene fluoride, polyimide, polyamide-imide, aramid, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, carboxymethylcellulose, etc. Examples of synthetic rubbers include styrene-butadiene rubber, fluorine-based rubber, ethylene propylenediene, etc.

[0095] Examples of negative electrode conductive additives include carbon nanoparticles, carbon black, acetylene black, graphite, Kechen black, carbon nanotubes, carbon nanofibers, etc., and one or more of these can be used.

[0096] The negative electrode active material layer is formed, for example, by a coating method. The coating method involves mixing silicon-based negative electrode active material and a binder, along with negative electrode conductive additives and carbon-based active material as needed, and then dispersing and coating the mixture with an organic solvent or water.

[0097] [Separator] The non-aqueous electrolyte secondary battery of the present invention may further include a separator.

[0098] A separator separates lithium metal or the positive and negative electrodes, preventing current short circuits caused by contact between the two electrodes while allowing lithium ions to pass through. This separator is formed from a porous membrane made of, for example, synthetic resin or ceramic, and may have a laminated structure in which two or more porous membranes are stacked. Examples of synthetic resins include polytetrafluoroethylene, polypropylene, and polyethylene.

[0099] In the non-aqueous electrolyte secondary battery of the present invention, the non-aqueous electrolyte can be impregnated, for example, into 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.

[0100] [Example of Non-Aqueous Electrolyte Secondary Battery Configuration] Next, as a specific example of the non-aqueous 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. However, the non-aqueous electrolyte secondary battery of the present invention is not limited to the following specific example.

[0101] The laminate film type lithium-ion secondary battery 10 shown in Figure 1 mainly consists of an electrode body 1 housed inside a sheet-like outer casing member 5. This electrode body 1 has a positive electrode, a negative electrode, and a separator between them, and is wound. In addition, there are cases where a laminate containing a positive electrode, a negative electrode, and a separator between them is housed without winding. In both electrode bodies, 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 part of the electrode body is protected by protective tape.

[0102] The negative electrode can have a structure, for example, as shown in the cross-section in Figure 2. The negative electrode 30 shown in Figure 2 has a negative electrode active material layer 32 on top of a negative electrode current collector 31.

[0103] Although not shown in the diagram, the positive electrode, like the negative electrode 30, has a configuration such as having a positive electrode active material layer on top of a positive electrode current collector.

[0104] 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 outer casing 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.

[0105] The exterior component 5 is, for example, a laminate film in which a fusion layer, a metal layer, and a surface protective layer are laminated in this order. In this laminate film, the outer edges of the fusion layers of two laminate films are fused together or bonded together with an adhesive 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 protective layer is, for example, nylon.

[0106] An adhesive film 4 is inserted between the outer casing member 5 and each of the positive lead 2 and negative lead 3 to prevent outside air from entering. This material is, for example, polyethylene, polypropylene, or polyolefin resin.

[0107] The outer casing member 5 further contains the non-aqueous electrolyte of the present invention. The non-aqueous electrolyte is impregnated into at least a portion of the positive electrode active material layer, at least a portion of the negative electrode active material layer 32, and at least a portion of the separator contained in the electrode body 1.

[0108] The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0109] (Example 1) [Preparation of positive electrode] A positive electrode slurry was prepared by adding a positive electrode active material (NCA), a conductive additive (Ketjenbrak), and a binder (polyvinylidene fluoride) to N-methylpyrrolidone (NMP) in a dry weight ratio of 93:3:4 and mixing.

[0110] Furthermore, a 20 μm thick aluminum foil was used as the positive electrode current collector. The positive electrode mixture slurry was applied to the positive electrode current collector and dried in a vacuum atmosphere at 120°C for 3 hours. After drying, the amount of positive electrode active material deposited per unit area (also called area density) on one side of the negative electrode was 12.3 mg / cm². ２ That was the case.

[0111] [Fabrication of the negative electrode] The negative electrode active material (amorphous low-valence nanosilicon oxide deposited in porous carbon, CVD-SiOx), graphite, conductive additive 1 (carbon nanotubes, CNT), conductive additive 2 (carbon nanoparticles with a median diameter of approximately 50 nm), sodium polyacrylate, and carboxymethylcellulose (CMC) were mixed in a dry mass ratio of 9.3:83.7:1:1:4:1, and then diluted with pure water to obtain a negative electrode mixture slurry. Here, the amorphous low-valence nanosilicon oxide deposited in porous carbon contains silicon with valencies of 0 to 4.

[0112] Furthermore, an electrolytic copper foil with a thickness of 15 μm was used as the negative electrode current collector. This electrolytic copper foil contained carbon and sulfur at a concentration of 70 ppm by mass each. Finally, 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 amount of negative electrode active material deposited per unit area on one side of the negative electrode (also called area density) was 7.0 mg / cm². ２ That was the case.

[0113] [Preparation of electrolyte] 1.0 [mol / kg] LiPF ６ An electrolyte was prepared by adding 5% by mass of 4-fluoro-1,3-dioxolan-2-one, 1% by mass of vinylene carbonate, 1% by mass of dimethylhexylfluorosilane (HADMFS), and 1% by mass of acetonitrile (AN) to an ethylene carbonate / dimethyl carbonate = 3 / 7 [vol% / vol%] (reference electrolyte).

[0114] [Assembly of Laminated Battery] The positive electrode and the negative electrode were wound together with a separator in between, and the wound assembly and the electrolyte were placed in an aluminum laminate to create a laminated battery.

[0115] [Measurement of Initial Efficiency] The initial efficiency was measured under the following conditions. First, the fabricated laminated battery was subjected to CCCV charging (initial charge) with a charge rate equivalent to 0.2C. The CV was 4.3V and the termination current was 50mA. Next, the discharge rate was similarly set to 0.2C and the discharge termination voltage was set to 2.5V, and CC discharge (initial discharge) was performed.

[0116] When investigating the initial charge-discharge characteristics, the initial efficiency was calculated. The initial efficiency was calculated using the formula: Initial Efficiency (%) = (Initial Discharge Capacity / Initial Charge Capacity) × 100.

[0117] [Measurement of Capacity Retention Rate] To investigate the cycle characteristics, the capacity retention rate was calculated. First, one charge-discharge cycle was performed in a 45°C atmosphere with CCCV charging at 0.2C and CC discharge at 0.2C. The charging voltage was 4.3V, the discharge termination voltage was 2.5V, and the charge termination current was 50mA. From the second cycle onward, 500 charge-discharge cycles were performed in a 45°C atmosphere with CCCV charging at 0.7C and CC discharge at 0.5C. The charging voltage was 4.3V, the discharge termination voltage was 2.5V, and the charge termination current was 50mA. The capacity retention rate was calculated using the formula: Capacity Retention Rate (%) = (Discharge Capacity at Cycle 501 / Discharge Capacity at Cycle 2) × 100.

[0118] [Measurement of DC Resistance] To investigate the internal resistance of the battery, a 3560 AC milliohm HiTESTER (manufactured by HIOKI E.E. CORPORATION) was used to measure the DC resistance of a laminated battery after 500 cycles of charging and discharging at CCCV charging 0.7C and CC discharging 0.5C (charging voltage 4.3V, discharge termination voltage 2.5V, charging termination current value 50mA).

[0119] (Example 2) An electrolyte was prepared in the same manner as in Example 1, except that the nitrile compound was changed from AN to propionitrile (PN). A laminate battery was then fabricated in the same manner as in Example 1, except that this electrolyte was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0120] (Example 3) An electrolyte was prepared in the same manner as in Example 1, except that the nitrile compound was changed from AN to adiponitrile (ADN). A laminate battery was then fabricated in the same manner as in Example 1, except that this electrolyte was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0121] (Example 4) An electrolyte was prepared in the same manner as in Example 1, except that the fluorosilane compound was changed from HADMFS to dimethyloctylfluorosilane (OADMFS). A laminate battery was then fabricated in the same manner as in Example 1, except that this electrolyte was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0122] (Example 5) An electrolyte was prepared in the same manner as in Example 1, except that the fluorosilane compound was changed from HADMFS to dimethyl-n-hexenylfluorosilane (HEDMFS). A laminate battery was then fabricated in the same manner as in Example 1, except that this electrolyte was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0123] (Examples 6-11) Electrolytes were prepared in the same manner as in Example 1, except that the amounts of HADMFS and AN added were changed as shown in Table 1 below. Laminated batteries were also fabricated in the same manner as in Example 1, except that each electrolyte was used. The battery characteristics of the obtained batteries were evaluated in the same manner as in Example 1.

[0124] (Example 12) An electrolyte was prepared in the same manner as in Example 1, except that the fluorosilane compound was changed from HADMFS to methylhexyldifluorosilane (HAMDFS). A laminate battery was then fabricated in the same manner as in Example 1, except that this electrolyte was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0125] (Example 13) An electrolyte was prepared in the same manner as in Example 1, except that the fluorosilane compound was changed from HADMFS to hexyltrifluorosilane (HATFS). A laminate battery was then fabricated in the same manner as in Example 1, except that this electrolyte was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0126] (Comparative Example 1) An electrolyte was prepared in the same manner as in Example 1, except that AN was not added. A laminated battery was then fabricated in the same manner as in Example 1, except that this electrolyte was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0127] (Comparative Example 2) An electrolyte was prepared in the same manner as in Example 1, except that HADMFS was not added. A laminate battery was also fabricated in the same manner as in Example 1, except that this electrolyte was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0128] (Comparative Example 3) An electrolyte was prepared in the same manner as in Example 1, except that HADMFS and AN were not added. A laminate battery was also fabricated in the same manner as in Example 1, except that this electrolyte was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0129] (Comparative Example 4) A negative electrode was fabricated in the same manner as in Example 1, except that the negative electrode active material was changed from CVD-SiOx to nanosilicon. A laminate battery was also fabricated in the same manner as in Example 1, except that this negative electrode was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0130] (Comparative Example 5) A negative electrode was fabricated in the same manner as in Example 1, except that the negative electrode active material was changed from CVD-SiOx to SiOx. In this SiOx, only zero-valent and tetravalent silicon existed. A laminated battery was fabricated in the same manner as in Example 1, except that this negative electrode was used. The battery characteristics of the obtained battery were evaluated in the same manner as in Example 1.

[0131] [Results] The evaluation results of the laminated batteries obtained in Examples 1 to 13 and Comparative Examples 1 to 5 are summarized in Table 1 below.

[0132]

[0133] As shown in Table 1, Examples 1 to 13, which used a combination of fluorosilane and nitrile compounds, exhibited superior cycle characteristics and suppressed an increase in internal resistance compared to Comparative Examples 1 to 3, which did not use a combination of fluorosilane and nitrile compounds.

[0134] Furthermore, since Example 1 uses a negative electrode active material containing amorphous low-valence nanosilicon oxide with a valency of 3 or less, it exhibits superior cycle characteristics and suppresses an increase in internal resistance compared to Comparative Examples 4 and 5, which use nanosilicon negative electrode active materials consisting of 0-valence and 4-valence nanosilicon oxides.

[0135] This specification encompasses the following embodiments: [1]: A non-aqueous electrolyte secondary battery comprising a negative electrode containing a negative electrode active material having negative electrode active material particles, a positive electrode, and a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte salt, wherein the negative electrode active material particles contain amorphous low-valence nanosilicon oxide with a valency of 3 or less, and the non-aqueous electrolyte is the following general formula (1) SiR １ ａ R ２ ｂ R ３ ｃ R ４ ｄ (1) (In general formula (1), R １ , R ２ and R ３ Each of these is independently an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an alkynyl group having 2 to 20 carbon atoms, and R ４ is a fluorine atom. Also, a, b, and c each independently represent integers from 0 to 3, and d represents an integer from 1 to 3, and a, b, c, and d are integers that satisfy a + b + c + d = 4.) A fluorosilane compound represented by the following general formula (2) R ５ -CN (2) (In general formula (2), R ５(This is an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms.) Or, the following general formula (3) NC-R ６ -CN (3) (In general formula (3), R ６ A non-aqueous electrolyte secondary battery characterized by containing a nitrile compound represented by ) which is an alkylene group having 1 to 20 carbon atoms. [2]: The non-aqueous electrolyte secondary battery of [1], wherein d of the fluorosilane compound represented by general formula (1) is 1. [3]: The non-aqueous electrolyte secondary battery of [1] or [2], wherein the non-aqueous electrolyte contains a halogenated cyclic carbonate ester. [4]: ​​The non-aqueous electrolyte secondary battery of [3], wherein when the content of the halogenated cyclic carbonate ester in the non-aqueous electrolyte is A by mass%, the content of the fluorosilane compound represented by general formula (1) is B by mass%, and the content of the nitrile compound represented by general formula (2) or (3) is C by mass%, the ratio of A to B is 0.01 ≤ A / B ≤ 300 and the ratio of A to C is 0.01 ≤ A / C ≤ 300. [5]: The non-aqueous electrolyte secondary battery of any of [1] to [4], wherein the low-valence nanosilicon oxide is dispersed in porous carbon. [6] The positive electrode contains a positive electrode active material having lithium and a transition metal element, the following general formula (4) Li ｘ Ni ｌ M1 ｍ M2 ｎ O ２ (4) A non-aqueous electrolyte secondary battery of any of the above [1] to [5], which is a composite oxide represented by (4) (in general formula (4), M1 and M2 are metallic elements, x represents 0.05 ≤ x ≤ 1.10, l represents 0.80 ≤ l ≤ 0.95, and l, m, and n satisfy l + m + n = 1).

[0136] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. In a non-aqueous electrolyte secondary battery including a negative electrode containing a negative electrode active material having negative electrode active material particles, a positive electrode, and a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte salt, the negative electrode active material particles contain a trivalent or lower amorphous low-valence silicon oxide, and the non-aqueous electrolyte is represented by the following general formula (1): SiR ａ R ２ ｂ R ３ ｃ R ４ ｄ (1) (In the general formula (1), R １ , R ２ and R ３ are each independently an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an alkynyl group having 2 to 20 carbon atoms, and R ４ is a fluorine atom. Also, a, b, and c each independently represent an integer of 0 to 3, d represents an integer of 1 to 3, and a, b, c, and d are integers satisfying a + b + c + d = 4.) and a fluorosilane compound represented by the following general formula (2): R ５ -CN (2) (In the general formula (2), R ５ is an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms.) or a nitrile compound represented by the following general formula (3): NC-R ６ -CN (3) (In the general formula (3), R ６ is an alkylene group having 1 to 20 carbon atoms.) and characterized in that it contains the above.​ 2. The non-aqueous electrolyte secondary battery according to claim 1, characterized in that d of the fluorosilane compound represented by the general formula (1) is 1.

3. The non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that the non-aqueous electrolyte contains a halogenated cyclic carbonate ester.

4. The non-aqueous electrolyte secondary battery according to claim 3, characterized in that when the content of halogenated cyclic carbonate ester in the non-aqueous electrolyte is A by mass%, the content of the fluorosilane compound represented by general formula (1) is B by mass%, and the content of the nitrile compound represented by general formula (2) or (3) is C by mass%, the ratio of A to B is 0.01 ≤ A / B ≤ 300, and the ratio of A to C is 0.01 ≤ A / C ≤ 300.

5. The non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that the low-valence nanosilicon oxide is dispersed in porous carbon.

6. The positive electrode contains a positive electrode active material having lithium and a transition metal element, the following general formula (4) Li ｘ Ni ｌ M1 ｍ M2 ｎ O ２ (4) A non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that it is a composite oxide represented by (4) (wherein M1 and M2 are metallic elements, x represents 0.05 ≤ x ≤ 1.10, l represents 0.80 ≤ l ≤ 0.95, and l, m, and n satisfy l + m + n = 1).

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