Non-aqueous electrolytes and non-aqueous secondary batteries

Abstract

To provide a nonaqueous electrolyte which can increase an initial charge / discharge efficiency and a capacity-keeping rate after a charge-discharge cycle test as to an acetonitrile electrolyte containing an ethylene sulfite and a silyl ester compound.SOLUTION: A nonaqueous electrolyte contains a nonaqueous solvent and a lithium salt. The lithium salt includes a lithium hexafluorophosphate (LiPF6), and a lithium-containing imide salt. The following holds when the content of LiPF6 in the nonaqueous electrolyte is A mol / L, and the content of the lithium-containing imide salt is B mol / L: 1.5<B / A<18. The nonaqueous solvent includes acetonitrile and ethylene sulfite. The nonaqueous electrolyte further contains a phosphorous silyl ester.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a non-aqueous electrolyte and a non-aqueous secondary battery using the same. [Background technology]

[0002] The applications of lithium-ion batteries, which were previously used as single cells in mobile devices, have changed dramatically amid the global trend of electrification of automobiles. In automotive batteries, the need for both reduced cobalt usage and increased energy density has led to research into technologies for stably utilizing chemically unstable nickel (Ni)-based cathode active materials, and several such technologies have been reported. Furthermore, to enable operation even at low temperatures, electrolytes using low-viscosity acetonitrile are also being researched, which necessitates the formation of a negative electrode coating to prevent such reductive decomposition.

[0003] Patent Document 1 describes how the lifespan of a battery using a high-potential positive electrode is improved by adding a silyl ester compound. Furthermore, in electrolytes containing acetonitrile, additives that can form a protective film on the negative electrode, such as ethylene sulfite, are important to prevent reductive decomposition at the negative electrode. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent Application No. 2016-64187 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, it has been newly discovered that, in acetonitrile electrolytes containing ethylene sulfite, the addition of silyl ester compounds may, under various conditions, not improve or even decrease durability in cycle tests. In this case, under various conditions, it may become difficult to improve the capacity retention rate after charge-discharge cycle tests.

[0006] Furthermore, silyl ester compounds sometimes cause side reactions separate from the formation of the positive electrode film, reducing the charge-discharge efficiency during the battery's initial charging. This has not been reported in prior art such as that described in Patent Document 1. The object of the present invention is to provide a non-aqueous electrolyte containing ethylene sulfite and a silyl ester compound in an acetonitrile electrolyte that can improve the initial charge-discharge efficiency and the capacity retention rate after charge-discharge cycle testing, and a non-aqueous secondary battery using the same. [Means for solving the problem]

[0007] This invention was made in view of the above circumstances, and it was found that the above problems can be solved by adjusting the lithium salt content in an electrolyte containing lithium hexafluoride phosphate (LiPF6), which causes the decomposition of silyl phosphite.

[0008] In other words, one aspect of the present invention is as follows. [1] A non-aqueous electrolyte comprising a non-aqueous solvent and a lithium salt, The aforementioned lithium salt comprises lithium hexafluoride phosphate (LiPF6) and a lithium-containing imide salt. When the content of LiPF6 in the non-aqueous electrolyte is A mol / L and the content of the lithium-containing imide salt is B mol / L, 1.5 The aforementioned non-aqueous solvent comprises acetonitrile and ethylene sulfite. The aforementioned non-aqueous electrolyte further contains silyl phosphite, Non-aqueous electrolyte. [2] The lithium-containing imide salt comprises lithium bis(fluorosulfonyl)imide (LiFSI) as described in [1], a non-aqueous electrolyte. [3] The aforementioned silyl phosphite ester is given by the following general formula (1): P(OSiR 1 R 2 R 3 ​)(OSiR 4 R 5 R 6 )(OSiR 7 R 8 R 9 )···(1) (wherein, R 1 ~R 9 are each an alkyl group having 4 or less carbon atoms, or an aryl group which may be substituted with an alkyl group or a halogen group) The non-aqueous electrolyte described in [1] or [2] represented by [4] The silyl phosphite ester contains at least tris(trimethylsilyl) phosphite, and the content of the tris(trimethylsilyl) phosphite is 0.05% by mass or more and 2% by mass or less based on the total amount of the non-aqueous electrolyte. The non-aqueous electrolyte according to any one of [1] to [3]. [5] The non-aqueous electrolyte according to any one of [1] to [4], wherein the content of the acetonitrile is 5% by volume or more and 60% by volume or less with respect to the non-aqueous electrolyte. [6] The non-aqueous solvent further contains vinylene carbonate, The non-aqueous electrolyte according to any one of [1] to [5], wherein the volume ratio of vinylene carbonate in the non-aqueous electrolyte is smaller than that of ethylene sulfite. [7] In a non-aqueous secondary battery comprising a positive electrode having a positive electrode active material layer on one or both sides of a current collector, a negative electrode having a negative electrode active material layer on one or both sides of a current collector, a separator, and the non-aqueous electrolyte according to any one of [1] to [6], The positive electrode active material layer has the following general formula (2): Li p Ni q Co r Mn s M t O u ···(2) {In the formula, M is at least one metal selected from the group consisting of aluminum (Al), tin (Sn), indium (In), iron (Fe), vanadium (V), copper (Cu), magnesium (Mg), titanium (Ti), zinc (Zn), molybdenum (Mo), zirconium (Zr), strontium (Sr), and barium (Ba), and 0 < p < 1.3, 0 < q < 1.2, 0 < r < 1.2, 0 ≦ s < 0.5, 0 ≦ t < 0.3, 0.7 ≦ q + r + s + t ≦ 1.2, 1.8 < u < 2.2, and p is a value determined by the charge-discharge state of the battery.} A non-aqueous secondary battery containing at least one selected from the group consisting of lithium-containing metal oxides represented by . [8] The non-aqueous secondary battery according to [7], wherein the nickel (Ni) content ratio q of the lithium-containing metal oxide represented by the general formula (2) is 0.5 < q < 1.2. [Advantages of the Invention]

[0009] According to the present invention, there are provided a non-aqueous electrolyte capable of improving the initial charge-discharge efficiency and the capacity retention rate after a charge-discharge cycle test in an acetonitrile electrolyte containing ethylene sulfite and a silyl ester compound, and a non-aqueous secondary battery using the same. [Brief Description of the Drawings]

[0010] [Figure 1] It is a plan view schematically showing an example of the non-aqueous secondary battery of the present embodiment. [Figure 2] It is a cross-sectional view taken along line A-A of FIG. 1. [Modes for Carrying Out the Invention]

[0011] The embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment") will be described in detail below. In this specification, numerical ranges indicated using "~" include the numerical values ​​indicated before and after them. In this specification, an upper or lower limit stated in a numerical range described in steps may be replaced with an upper or lower limit in a numerical range described in another step. In this specification, an upper or lower limit stated in a numerical range may also be replaced with a value described in an example. The scale, shape, and length of parts of the drawings may be exaggerated for further clarity.

[0012] One aspect of this embodiment is A non-aqueous electrolyte comprising a non-aqueous solvent and a lithium salt, Lithium salts include lithium hexafluoride phosphate (LiPF6) and lithium-containing imide salts. When the content of LiPF6 in the non-aqueous electrolyte is A mol / L and the content of the lithium-containing imide salt is B mol / L, then 1.5 Non-aqueous solvents include acetonitrile and ethylene sulfite. The non-aqueous electrolyte is a non-aqueous electrolyte that further contains silyl phosphite. According to this, it is possible to improve the initial charge-discharge efficiency and the capacity retention rate after charge-discharge cycle testing in an acetonitrile electrolyte containing ethylene sulfite and silyl ester compounds. <Non-aqueous secondary battery> ​The non-aqueous secondary battery of this embodiment is a secondary battery comprising a positive electrode and a negative electrode along with a non-aqueous electrolyte, and may be, for example, a lithium-ion battery, and more specifically, a lithium-ion battery whose schematic plan view is shown in Figure 1 and whose schematic cross-sectional view is shown in Figure 2. The lithium-ion battery 100 shown in Figures 1 and 2 comprises a separator 170, a positive electrode 150 and a negative electrode 160 that sandwich the separator 170 from both sides, a positive electrode lead 130 (connected to the positive electrode 150) and a negative electrode lead 140 (connected to the negative electrode 160) that sandwich the laminate of these (separator 170, positive electrode 150 and negative electrode 160), and a battery casing 110 that houses them. The laminate formed by stacking the positive electrode 150, the separator 170 and the negative electrode 160 is impregnated with the non-aqueous electrolyte according to this embodiment.

[0013] <1. Non-aqueous electrolyte> In this embodiment, the "non-aqueous electrolyte" comprises a non-aqueous solvent and a lithium salt, wherein the lithium salt comprises LiPF6 and a lithium-containing imide salt, and when the content of LiPF6 in the electrolyte is A mol / L and the content of the lithium-containing imide salt is B mol / L, then 1.5 The non-aqueous electrolyte according to this embodiment preferably contains as little water as possible, but may contain a very small amount of water as long as it does not hinder the resolution of the problem of the present invention. The amount of water is 1% by mass or less, 300 ppm by mass or less, and preferably 200 ppm by mass or less, as a percentage of the total amount of the non-aqueous electrolyte. As long as the non-aqueous electrolyte has the configuration necessary to solve the problem of the present invention, other components can be appropriately selected and applied from known non-aqueous electrolyte materials used in lithium-ion batteries.

[0014] <1-1. Non-aqueous solvents> ​In this embodiment, "non-aqueous solvent" refers to the elements of a non-aqueous electrolyte excluding lithium salts, silyl phosphite esters, and various additives. If the non-aqueous electrolyte contains electrode protection additives, "non-aqueous solvent" refers to the elements of the non-aqueous electrolyte excluding lithium salts, silyl phosphite esters, and additives other than electrode protection additives. Examples of non-aqueous solvents include alcohols such as methanol and ethanol; and aprotic solvents. Among these, aprotic solvents are preferred as non-aqueous solvents. The non-aqueous solvent may contain solvents other than aprotic solvents, as long as it does not hinder the resolution of the problem of the present invention.

[0015] The non-aqueous solvent in the non-aqueous electrolyte of the present invention contains acetonitrile as an aprotic solvent. The inclusion of acetonitrile in the non-aqueous solvent improves the ionic conductivity of the non-aqueous electrolyte, thereby enhancing the diffusion of lithium ions within the battery. Therefore, when the non-aqueous electrolyte contains acetonitrile, lithium ions can diffuse well even to areas near the current collector, which are difficult for lithium ions to reach during high-load discharge, particularly in positive electrodes where the positive electrode active material layer is thickened and the amount of positive electrode active material is increased. This makes it possible to extract sufficient capacity even during high-load discharge, resulting in a non-aqueous secondary battery with excellent load characteristics.

[0016] Furthermore, the inclusion of acetonitrile in the non-aqueous electrolyte can improve the rapid charging characteristics of non-aqueous secondary batteries. In constant current (CC)-constant voltage (CV) charging of non-aqueous secondary batteries, the capacity per unit time during the CC charging period is greater than the capacity per unit time during the CV charging period. When acetonitrile is used as the non-aqueous solvent in the non-aqueous electrolyte, the area in which CC charging can be performed can be enlarged (the CC charging time can be extended), and the charging current can also be increased, thus significantly shortening the time it takes to bring a non-aqueous secondary battery from the start of charging to a fully charged state.

[0017] Furthermore, acetonitrile is readily reductively decomposed electrochemically. Therefore, when using acetonitrile, it is preferable to use another solvent (for example, an aprotic solvent other than acetonitrile) in combination with acetonitrile as a non-aqueous solvent, and / or to add an electrode protection additive for forming a protective film on the electrode.

[0018] The acetonitrile content in the non-aqueous electrolyte is preferably 5% to 60% by volume relative to the total volume of the non-aqueous electrolyte. The lower limit of the acetonitrile content is more preferably 7% or more by volume, and even more preferably 10% or more by volume, relative to the total volume of the non-aqueous electrolyte. The upper limit of the acetonitrile content is more preferably 45% or less by volume, and even more preferably 35% or less by volume, relative to the total volume of the non-aqueous electrolyte. When the acetonitrile content is 5% or more by volume relative to the total volume of the non-aqueous electrolyte, the ionic conductivity of the non-aqueous electrolyte tends to increase, enabling the non-aqueous secondary battery to exhibit high power output characteristics, and further promoting the dissolution of lithium salts. In addition, by limiting the acetonitrile content to 60% or less by volume, thermal stability can be improved. When the acetonitrile content of the non-aqueous electrolyte is within the above range, the high-temperature cycle characteristics and other battery characteristics of the non-aqueous secondary battery tend to be further improved while maintaining the excellent performance of acetonitrile.

[0019] Examples of aprotic solvents other than acetonitrile include cyclic carbonates, fluoroethylene carbonates, lactones, organic compounds having sulfur atoms, chain-like fluorinated carbonates, cyclic ethers, mononitriles other than acetonitrile, alkoxy-substituted nitriles, dinitriles, cyclic nitriles, short-chain fatty acid esters, chain-like ethers, fluorinated ethers, ketones, and compounds in which some or all of the H atoms of the aprotic solvent are substituted with halogen atoms.

[0020] Since acetonitrile, a component of non-aqueous electrolytes, is readily reductively decomposed electrochemically, the non-aqueous electrolyte according to this embodiment contains ethylene sulfite having a sulfur atom in addition to acetonitrile as the non-aqueous solvent. Furthermore, if the non-aqueous solvent contains vinylene carbonate, a cyclic carbonate, it is preferable that its volume ratio in the non-aqueous electrolyte is smaller than that of ethylene sulfite.

[0021] In this embodiment, the non-aqueous solvent contains acetonitrile, ethylene sulfite as an organic compound having a sulfur atom, and vinylene carbonate as a cyclic carbonate. When the non-aqueous electrolyte is used in a non-aqueous secondary battery, it suppresses the degradation of the positive electrode active material with a high nickel (Ni) ratio and allows the battery to operate at a high current density. Furthermore, from the viewpoint of reducing the electrical resistance of the negative electrode coating derived from vinylene carbonate, as described above, it is preferable that the volume ratio of vinylene carbonate in the non-aqueous electrolyte is smaller than that of ethylene sulfite.

[0022] The negative electrode protective coating derived from vinylene carbonate has high resistance, which tends to lead to performance degradation during rapid charging and in low-temperature environments, as well as battery swelling due to gas generation during decomposition. Ethylene sulfite has a lower lowest unoccupied orbital (LUMO) level compared to other oxygen-containing sulfur compounds, and can be reductively decomposed at a lower potential than vinylene carbonate to form a negative electrode protective coating. This makes it possible to reduce the amount of vinylene carbonate added and solve the problems associated with negative electrode protective coatings derived from vinylene carbonate. Furthermore, the negative electrode protective coating derived from ethylene sulfite has low resistance over a wide temperature range, and promotes the formation of a negative electrode SEI (Solid Electrolyte Interface) that is highly resistant to acetonitrile and its decomposition products. This makes it possible to provide a non-aqueous electrolyte and a non-aqueous secondary battery that can operate stably at high current densities.

[0023] In this embodiment, it is preferable that the total content of ethylene sulfite and vinylene carbonate in the non-aqueous electrolyte is 0.1% by volume or more and less than 10% by volume relative to the total amount of the non-aqueous electrolyte, from the viewpoint of suppressing an increase in internal resistance.

[0024] Examples of cyclic carbonates include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene carbonate, 1,2-pentylene carbonate, trans-2,3-pentylene carbonate, cis-2,3-pentylene carbonate, vinylene carbonate, 4,5-dimethylvinylene carbonate, and vinylethylene carbonate;

[0025] Examples of fluoroethylene carbonates include 4-fluoro-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, cis-4,5-difluoro-1,3-dioxolan-2-one, trans-4,5-difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2-one, 4,4,5,5-tetrafluoro-1,3-dioxolan-2-one, and 4,4,5-trifluoro-5-methyl-1,3-dioxolan-2-one;

[0026] Examples of lactones include γ-butyrolactone, α-methyl-γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, and ε-caprolactone;

[0027] Examples of organic compounds containing a sulfur atom include ethylene sulfite, propylene sulfite, butylene sulfite, pentene sulfite, sulfolane, 3-sulfolene, 3-methylsulfolane, 1,3-propanesultone, 1,4-butanesultone, 1-propene-1,3-sultone, dimethyl sulfoxide, tetramethylene sulfoxide, and ethylene glycol sulfite;

[0028] Examples of linear carbonates include ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, and diisobutyl carbonate;

[0029] Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, and 1,3-dioxane;

[0030] Other mononitriles besides acetonitrile include, for example, propionitrile, butyronitrile, valeronitrile, benzonitrile, and acrylonitrile;

[0031] Examples of alkoxy-substituted nitriles include methoxyacetonitrile and 3-methoxypropionitrile;

[0032] Examples of dinitriles include malononitrile, succinonitrile, glutaronitrile, adiponitrile, 1,4-dicyanoheptane, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 2,6-dicyanoheptane, 1,8-dicyanooctane, 2,7-dicyanooctane, 1,9-dicyanononane, 2,8-dicyanononane, 1,10-dicyanodecane, 1,6-dicyanodecane, and 2,4-dimethylglutaronitrile;

[0033] Examples of cyclic nitriles include benzonitrile;

[0034] Examples of short-chain fatty acid esters include methyl acetate, methyl propionate, methyl isobutyrate, methyl butyrate, methyl isovalerate, methyl valerate, methyl pivalate, methyl hydroangelicaate, methyl caproate, ethyl acetate, ethyl propionate, ethyl isobutyrate, ethyl butyrate, ethyl isovalerate, ethyl valerate, ethyl pivalate, ethyl hydroangelicaate, ethyl caproate, propyl acetate, propyl propionate, propyl isobutyrate, propyl butyrate, propyl isovalerate, propyl valerate, propyl pivalate, propyl hydroangelicaate, propyl caproate, isopropyl acetate, isopropyl propionate, isopropyl isobutyrate, isopropyl butyrate, isopropyl isovalerate, isopropyl valerate, isopropyl pivalate Propyl, isopropyl hydroangelicaate, isopropyl caproate, butyl acetate, butyl propionate, butyl isobutyrate, butyl butyrate, butyl isovalerate, butyl valerate, butyl pivalate, butyl hydroangelicaate, butyl caproate, isobutyl acetate, isobutyl propionate, isobutyrate, isobutyrate, isobutyl isovalerate, isobutyl valerate, isobutyl pivalate, isobutyl hydroangelicaate, isobutyl caproate, tert-butyl acetate, tert-butyl propionate, tert-butyl isobutyrate, tert-butyl butyrate, tert-butyl isovalerate, tert-butyl valerate, tert-butyl pivalate, tert-butyl hydroangelicaate, and tert-butyl caproate;

[0035] Examples of linear ethers include dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme, and tetraglyme;

[0036] Examples of fluorinated ethers include Rf 10 -OR 11 (In the formula, Rf 10 represents an alkyl group containing a fluorine atom, and R 11 This represents a monovalent organic group that may contain a fluorine atom.

[0037] Examples of ketones include acetone, methyl ethyl ketone, and methyl isobutyl ketone;

[0038] Examples of compounds in which some or all of the H atoms of the aprotic solvent are substituted with halogen atoms include compounds in which the halogen atom is fluorine; We can list some examples.

[0039] Examples of fluorinated chain carbonates include methyltrifluoroethyl carbonate, trifluorodimethyl carbonate, trifluorodiethyl carbonate, trifluoroethylmethyl carbonate, methyl 2,2-difluoroethyl carbonate, methyl 2,2,2-trifluoroethyl carbonate, and methyl 2,2,3,3-tetrafluoropropyl carbonate. The above fluorinated chain carbonates have the following general formula: R 12 -OC(O)OR 13 {where, R 12 and R 13 These are CH3, CH2CH3, CH2CH2CH3, CH(CH3)2, and CH2Rf 14 At least one selected from the group consisting of Rf 14 is an alkyl group having 1 to 3 carbon atoms in which at least one fluorine atom replaces a hydrogen atom, and R 12 and / or R 13 It contains at least one fluorine atom. It can be expressed as follows.

[0040] Furthermore, examples of fluorinated short-chain fatty acid esters include fluorinated short-chain fatty acid esters such as 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, and 2,2,3,3-tetrafluoropropyl acetate. Fluorinated short-chain fatty acid esters are represented by the following general formula: R 15 -C(O)OR 16 {where, R 15is CH3, CH2CH3, CH2CH2CH3, CH(CH3)2, CF3CF2H, CFH2, CF2Rf 17 CFHRf 18 , and CH2Rf 19 At least one selected from the group consisting of R 16 These are CH3, CH2CH3, CH2CH2CH3, CH(CH3)2, and CH2Rf 20 At least one selected from the group consisting of Rf 19 Rf is a C1-C3 alkyl group in which at least one fluorine atom may substitute for a hydrogen atom. 20 is an alkyl group having 1 to 3 carbon atoms in which at least one fluorine atom replaces a hydrogen atom, and R 15 and / or R 16 It contains at least one fluorine atom, R 15 If R is CF2H, 16 It is not CH3. It can be expressed as follows.

[0041] In this embodiment, the aprotic solvent other than acetonitrile may be used alone or in combination of two or more.

[0042] In this embodiment, the non-aqueous solvent preferably contains one or more cyclic carbonates and linear carbonates together with acetonitrile, from the viewpoint of improving the stability of the non-aqueous electrolyte. From this viewpoint, it is more preferable to use a cyclic carbonate together with acetonitrile in this embodiment, and even more preferable to use both cyclic carbonates and linear carbonates together with acetonitrile.

[0043] When using a cyclic carbonate other than vinylene carbonate with acetonitrile, it is particularly preferable that such cyclic carbonate includes ethylene carbonate and / or fluoroethylene carbonate.

[0044] <1-2. Lithium Salts> The non-aqueous electrolyte of this embodiment includes LiPF6 and a lithium-containing imide salt as lithium salts.

[0045] Lithium-containing imide salts are LiN(SO2C) m F 2m+1 The lithium salt is represented by )² [wherein m is an integer from 0 to 8], and specifically, from the viewpoint of ease of solubility and availability, it is preferable to include lithium bis(fluorosulfonyl)imide (LiN(SO2F)₂, LiFSI), but is not limited to this. It may also include imide salts other than these imide salts.

[0046] When acetonitrile is included in a non-aqueous electrolyte, the saturation concentration of lithium-containing imide salt relative to acetonitrile is higher than the saturation concentration of LiPF6. Therefore, it is preferable to include lithium-containing imide salt at a molar concentration such that LiPF6 ≤ lithium-containing imide salt, as this suppresses the association and precipitation of lithium salt and acetonitrile at low temperatures. Furthermore, from the viewpoint of ion supply, it is preferable that the lithium-containing imide salt content is between 0.5 mol and 3 mol per liter of non-aqueous electrolyte. An acetonitrile-containing non-aqueous electrolyte containing LiN(SO2F)2 can effectively suppress the reduction in ionic conductivity at low temperatures such as -10°C or -30°C, thereby obtaining excellent low-temperature characteristics. In this way, by limiting the content, it is also possible to more effectively suppress the increase in resistance during high-temperature heating.

[0047] Furthermore, the lithium salt may further contain fluorine-containing inorganic lithium salts other than LiPF6, such as LiBF4, LiAsF6, Li2SiF6, LiSbF6, and Li2B 12 F b H 12-bThe formula may include fluorine-containing inorganic lithium salts such as [wherein b is an integer from 0 to 3]. "Inorganic lithium salt" refers to a lithium salt that does not contain carbon atoms as anions and is soluble in acetonitrile. "Fluorine-containing inorganic lithium salt" refers to a lithium salt that does not contain carbon atoms as anions, contains fluorine atoms as anions, and is soluble in acetonitrile. Fluorine-containing inorganic lithium salts are excellent in that they form a passive film on the surface of the metal foil that is the positive electrode current collector, thereby suppressing corrosion of the positive electrode current collector. These fluorine-containing inorganic lithium salts can be used individually or in combination of two or more. As the fluorine-containing inorganic lithium salt, a compound that is a double salt of LiF and a Lewis acid is desirable, and among these, a fluorine-containing inorganic lithium salt having a phosphorus atom is more preferable because it makes it easier to release free fluorine atoms. A typical fluorine-containing inorganic lithium salt is LiPF6, which dissolves and releases the PF6 anion. When a fluorine-containing inorganic lithium salt containing boron atoms is used as the fluorine-containing inorganic lithium salt, it is preferable because it makes it easier to capture excess free acid components that may lead to battery degradation, and from this viewpoint, LiBF4 is particularly preferred.

[0048] In this embodiment, there are no particular restrictions on the content of fluorine-containing inorganic lithium salt in the non-aqueous electrolyte, but it is preferably 0.01 mol or more, more preferably 0.02 mol or more, and even more preferably 0.03 mol or more per liter of the non-aqueous electrolyte. When the content of fluorine-containing inorganic lithium salt is within the above range of 0.01 mol or more, the ionic conductivity tends to increase, and high power characteristics can be exhibited. Furthermore, the content of fluorine-containing inorganic lithium salt is preferably less than 1.5 mol, more preferably less than 0.5 mol, and even more preferably less than 0.1 mol per liter of the non-aqueous electrolyte. When the content of fluorine-containing inorganic lithium salt is within the above range of less than 1.5 mol, the ionic conductivity increases, high power characteristics can be exhibited, and the decrease in ionic conductivity due to viscosity increase at low temperatures tends to be suppressed. This tends to improve the high-temperature cycle characteristics and other battery characteristics of the non-aqueous secondary battery while maintaining the excellent performance of the non-aqueous electrolyte.

[0049] In this embodiment, in addition to the LiPF6 and lithium-containing imide salt described above, the silyl phosphite ester described later is also included. When the content of LiPF6 in the non-aqueous electrolyte is A mol / L and the content of lithium-containing imide salt is B mol / L, from the viewpoint of preventing a shortage of lithium necessary for a good negative electrode coating due to the side reaction of the silyl phosphite ester, B / A is preferably less than 18 (e.g., 18.0), more preferably 15 (e.g., 15.0) or less, and even more preferably 13 (e.g., 13.0) or less. Furthermore, from the viewpoint of suppressing the side reaction rate of LiPF6 and silyl phosphite ester, B / A is preferably greater than 1.5 (e.g., 1.50), more preferably 1.6 (e.g., 1.60) or more, and even more preferably 1.7 (e.g., 1.70) or more, or 1.8 (e.g., 1.80) or more. Within the concentration range described above, the salt concentration will not impair battery performance, and the side reaction of silyl phosphite during the initial charge and discharge will also be reduced.

[0050] The non-aqueous electrolyte of this embodiment may further contain an organolithium salt. An "organolithium salt" refers to a lithium salt that contains a carbon atom as an anion and is soluble in acetonitrile.

[0051] Examples of organolithium salts include organolithium salts having an oxalic acid group. Specific examples of organolithium salts having an oxalic acid group include, for example, organolithium salts represented as LiB(C2O4)2, LiBF2(C2O4), LiPF4(C2O4), and LiPF2(C2O4)2, respectively. Among these, at least one lithium salt selected from the lithium salts represented as LiB(C2O4)2 and LiBF2(C2O4) is preferred. Furthermore, it is more preferable to use one or more of these together with a fluorine-containing inorganic lithium salt. These organolithium salts having an oxalic acid group may be added to a non-aqueous electrolyte or incorporated into the negative electrode (negative electrode active material layer).

[0052] From the viewpoint of ensuring better effects from its use, the amount of organolithium salt having an oxalic acid group added to a non-aqueous electrolyte is preferably 0.005 moles or more, more preferably 0.02 moles or more, and even more preferably 0.05 moles or more, per liter of non-aqueous solvent in the non-aqueous electrolyte. However, if the amount of organolithium salt having an oxalic acid group in the non-aqueous electrolyte is too large, precipitation may occur. Therefore, the amount of organolithium salt having an oxalic acid group added to a non-aqueous electrolyte is preferably less than 1.0 mole, more preferably less than 0.5 moles, and even more preferably less than 0.2 moles, per liter of non-aqueous solvent in the non-aqueous electrolyte.

[0053] Organolithium salts containing oxalic acid groups are known to be poorly soluble in low-polarity organic solvents, particularly in linear carbonates. Organolithium salts containing oxalic acid groups may contain trace amounts of lithium oxalate, and furthermore, when mixed as a non-aqueous electrolyte, they may react with trace amounts of water contained in other raw materials, generating a new white precipitate of lithium oxalate. Therefore, while the lithium oxalate content in the non-aqueous electrolyte of this embodiment is not particularly limited, it is preferably 0 to 500 ppm.

[0054] In this embodiment, in addition to the lithium salts listed above, lithium salts commonly used for non-aqueous secondary batteries may be added as auxiliary salts. Specific examples of other lithium salts include, for example, LiClO4, LiAlO4, LiAlCl4, and LiB 10 Cl 10 Inorganic lithium salts that do not contain a fluorine atom as an anion, such as chloroborane Li; LiCF3SO3, LiCF3CO2, Li2C2F4(SO3)2, LiC(CF3SO2)3, LiC n F (2n+1) SO3 {wherein n≧2}, organolithium salts such as lower aliphatic carboxylic acid Li, tetraphenylborate Li, LiB(C3O4H2)2; LiPF5(CF3) and others. n (C p F 2p+1 ) 6-nOrganolithium salts represented by the formula [wherein n is an integer from 1 to 5 and p is an integer from 1 to 8]; LiBF such as LiBF3(CF3) q (C s F 2s+1 ) 4-q Organolithium salts represented by the formula [wherein q is an integer between 1 and 3, and s is an integer between 1 and 8]; lithium salts bonded to polyvalent anions; The following formula (a): LiC(SO2R A )(SO2R B )(SO2R C ) (a) {where, R A , R B , and R C These may be identical or different from each other, and represent a perfluoroalkyl group having 1 to 8 carbon atoms. The following formula (b): LiN(SO2OR D )(SO2OR E (b) {where, R D , and R E These may be identical or different from each other, and represent a perfluoroalkyl group having 1 to 8 carbon atoms. The following formula (c) LiN(SO2R F )(SO2OR G ) (c) {where, R F , and R G These may be identical or different from each other, and represent a perfluoroalkyl group having 1 to 8 carbon atoms. Examples include organolithium salts represented by each of the above, and one or more of these can be used together with a fluorine-containing inorganic lithium salt.

[0055] <1-3. Silyl phosphite esters> The non-aqueous electrolyte according to this embodiment contains a silyl phosphite ester in addition to the non-aqueous solvent and lithium salt described above. The silyl phosphite ester can form a protective film on the positive electrode surface and, in this embodiment, has the effect of improving the capacity retention rate.

[0056] More specifically, silyl phosphite esters are given by the following general formula (1): P(OSiR 1 R 2 R 3 )(OSiR 4 R 5 R 6 )(OSiR 7 R 8 R 9 )···(1) (However, R 1 ~R 9 It is preferable that each of these is a silyl phosphite ester represented by an alkyl group having 4 or fewer carbon atoms, or an aryl group which may be substituted with an alkyl group or a halogen group, from the viewpoint of reactivity, availability, and ease of achieving the effects of the present invention.

[0057] Specific examples of silyl phosphite esters represented by general formula (1) include tris(trimethylsilyl) phosphite and tris(triethylsilyl) phosphite.

[0058] The silyl phosphite ester may contain one or more esters represented by general formula (1), but from the viewpoint of ease of availability and ease of achieving the effects of the present invention, it is preferable to include tris(trimethylsilyl) phosphite. The content of tris(trimethylsilyl) phosphite is preferably 0.05% by mass or more and 2.0% by mass or less based on the total amount of the non-aqueous electrolyte. From the viewpoint of volume retention, 0.1% by mass or more is more preferable. Furthermore, from the viewpoint of suppressing side reactions, 1.0% by mass or less is more preferable.

[0059] In this embodiment, the content of silyl phosphite ester (for example, the above-mentioned tris(trimethylsilyl) phosphite) is preferably in the range of 0.05% by mass or more and 2.0% by mass or less relative to the total amount of the non-aqueous electrolyte. From the viewpoint of improving the capacity retention rate, the lower limit of the silyl phosphite ester content is more preferably 0.1% by mass or more relative to the total amount of the non-aqueous electrolyte. From the viewpoint of suppressing side reactions, the upper limit of the silyl phosphite ester content is more preferably 1.0% by mass or less relative to the total amount of the non-aqueous electrolyte. By adjusting the silyl phosphite ester content within the above range, it is possible to add even better battery characteristics without impairing the basic functions of the non-aqueous secondary battery.

[0060] <Additive for electrode protection> The electrode protection additive is not particularly limited as long as it does not hinder the resolution of the problem according to the present invention, and may substantially overlap with the substance that plays the role of a solvent for dissolving lithium salts (i.e., the non-aqueous solvent described above) (except acetonitrile, vinylene carbonate, ethylene sulfite, and organosilicon compounds). The electrode protection additive is preferably a substance that contributes to improving the performance of the non-aqueous electrolyte and the non-aqueous secondary battery in this embodiment, but it also includes substances that do not directly participate in the electrochemical reaction.

[0061] Specific examples of electrode protection additives include, for example, 4-fluoro-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, cis-4,5-difluoro-1,3-dioxolan-2-one, trans-4,5-difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2-one, and 4,4,5,5-tetrafluoro-1,3-dioxolan-2-one. Fluoroethylene carbonates represented by n-2-one and 4,4,5-trifluoro-5-methyl-1,3-dioxolan-2-one; unsaturated bond-containing cyclic carbonates represented by 4,5-dimethylvinylene carbonate and vinylethylene carbonate; represented by γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, and ε-caprolactone. Examples include lactones; cyclic ethers represented by 1,4-dioxane; cyclic sulfur compounds represented by propylene sulfite, butylene sulfite, pentene sulfite, sulfolane, 3-sulfolene, 3-methylsulfolane, 1,3-propanesultone, 1,4-butanesultone, 1-propene-1,3-sultone, and tetramethylene sulfoxide; chain acid anhydrides represented by acetic anhydride, propionic anhydride, and benzoic anhydride; cyclic acid anhydrides represented by malonic anhydride, succinic anhydride, glutaric anhydride, maleic anhydride, phthalic anhydride, 1,2-cyclohexanedicarboxylic anhydride, 2,3-naphthalenedicarboxylic anhydride, or naphthalene-1,4,5,8-tetracarboxylic dianhydride; and mixed acid anhydrides with structures formed by the dehydration condensation of two different carboxylic acids, or different types of acids such as a carboxylic acid and a sulfonic acid. These can be used individually or in combination of two or more.

[0062] In this embodiment, there are no particular restrictions on the content of the electrode protection additive in the non-aqueous electrolyte, but it is preferably 0.1 to 30% by volume, more preferably 0.3 to 15% by volume, and even more preferably 0.5 to 4% by volume relative to the total amount of the non-aqueous solvent.

[0063] In this embodiment, the higher the content of the electrode protection additive, the more the degradation of the non-aqueous electrolyte is suppressed. However, the lower the content of the electrode protection additive, the better the high-power characteristics of the non-aqueous secondary battery in low-temperature environments. Therefore, by adjusting the content of the electrode protection additive within the above range, it is possible to maximize the excellent performance based on the high ionic conductivity of the non-aqueous electrolyte without impairing the basic functions of the non-aqueous secondary battery. By preparing a non-aqueous electrolyte with such a composition, it is possible to further improve the cycle performance, high-power performance in low-temperature environments, and other battery characteristics of the non-aqueous secondary battery.

[0064] <Optional Additives> In this embodiment, for the purpose of improving the charge-discharge cycle characteristics of the non-aqueous secondary battery, improving high-temperature storage capacity and safety (e.g., overcharge prevention), the non-aqueous electrolyte may appropriately contain optional additives selected from, for example, sulfonic acid esters, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, tert-butylbenzene, phosphate esters [ethyl diethyl phosphonoacetate (EDPA): (C2H5O)2(P=O)-CH2(C=O)OC2H5, tris(trifluoroethyl) phosphate (TFEP): (CF3CH2O)3P=O, triphenyl phosphate (TPP): (C6H5O)3P=O: (CH2=CHCH2O)3P=O, triallyl phosphate, etc.], nitrogen-containing cyclic compounds without steric hindrance around lone pairs [pyridine, 1-methyl-1H-benzotriazole, 1-methylpyrazole, caffeine, etc.], and derivatives of these compounds. Phosphate esters, in particular, are effective in suppressing side reactions during storage.

[0065] The content of other optional additives in this embodiment is calculated as a mass percentage with respect to the total mass of all components constituting the non-aqueous electrolyte. There is no particular limitation on the content of other optional additives, but it is preferably in the range of 0.01% by mass or more and 10% by mass or less, more preferably in the range of 0.02% by mass or more and 5% by mass or less, and even more preferably in the range of 0.05% by mass or more and 3% by mass or less, with respect to the total amount of the non-aqueous electrolyte. By adjusting the content of other optional additives within the above range, it tends to be possible to add even better battery characteristics without impairing the basic functions as a non-aqueous secondary battery.

[0066] <2. Positive Electrode and Positive Current Collector> The positive electrode of this embodiment has a positive electrode active material layer on one or both sides of the current collector. The positive electrode 150 shown in FIGS. 1 and 2 is composed of a positive electrode active material layer made from a positive electrode mixture and a positive current collector. The positive electrode 150 is not particularly limited as long as it functions as the positive electrode of a non-aqueous secondary battery and may be a known one. The positive electrode in the present invention contains a lithium-containing compound containing Fe and preferably also contains nickel (Ni) at a relatively high ratio.

[0067] The positive electrode active material layer preferably contains a positive electrode active material and, if necessary, further contains a conductive assistant and a binder.

[0068] The positive electrode active material layer preferably contains, as a positive electrode active material, a material capable of occluding and releasing lithium ions. When using such a material, it is preferable because it tends to be possible to obtain a high voltage and a high energy density.

[0069] Examples of the positive electrode active material include a positive electrode active material containing at least one transition metal element selected from the group consisting of Ni, Mn, and Co, and the following general formula (2): Li p Ni q Co r Mn s M t O u ···(2) {In the formula, M is at least one metal selected from the group consisting of aluminum (Al), tin (Sn), indium (In), iron (Fe), vanadium (V), copper (Cu), magnesium (Mg), titanium (Ti), zinc (Zn), molybdenum (Mo), zirconium (Zr), strontium (Sr), and barium (Ba), and 0 < p < 1.3, 0 < q < 1.2, 0 < r < 1.2, 0 ≦ s < 0.5, 0 ≦ t < 0.3, 0.7 ≦ q + r + s + t ≦ 1.2, 1.8 < u < 2.2, and p is a value determined by the charge-discharge state of the battery} At least one Li-containing metal oxide selected from the lithium (Li)-containing metal oxides represented by is preferable. From the viewpoint of energy density, it is more preferable that the nickel (Ni) content ratio q of the lithium-containing metal oxide represented by the general formula (2) is 0.5 < q < 1.2.

[0070] Specific examples of the positive electrode active material include, for example, lithium cobalt oxide typified by LiCoO2; lithium manganese oxide typified by LiMnO2, LiMn2O4, and Li2Mn2O4; lithium nickel oxide typified by LiNiO2; LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.8 Co 0.2 O2, and lithium-containing composite metal oxides represented by Li z MO2 (where M contains at least one transition metal element selected from the group consisting of Ni, Mn, and Co, and / or represents two or more metal elements selected from the group consisting of Ni, Mn, Co, Al, and Mg, and z represents a number greater than 0.9 and less than 1.2).

[0071] Particularly, when the Ni content ratio q of the Li-containing metal oxide represented by the general formula (2) is 0.5 < q < 1.2, it is preferable because both reduction of the usage amount of Co, which is a rare metal, and increase in energy density are achieved. Examples of such a positive electrode active material include LiNi 0.6 Co0.2 Mn 0.2 O2, LiLiLi 0.75 Co 0.15 Mn 0.15 O2, LiLiLi 0.8 Co 0.1 Mn 0.1 O2, LiLiLi 0.85 Co 0.075 Mn 0.075 O2, LiLiLi 0.8 Co 0.15 Al 0.05 O2, LiLiLi 0.81 Co 0.1 Al 0.09 O2, LiLiLi 0.85 Co 0.1 Al 0.05 Examples include lithium-containing composite metal oxides such as O2.

[0072] On the other hand, the higher the Ni content in the positive electrode active material layer, the more likely degradation is to occur at low voltages. The positive electrode active material of Li-containing metal oxide represented by general formula (2) inherently contains active sites that oxidize and degrade non-aqueous electrolytes, but these active sites can unintentionally consume compounds added to protect the negative electrode on the positive electrode side. Acid anhydrides, in particular, tend to be susceptible to this effect. Especially when acetonitrile is included as the non-aqueous solvent, the effect of adding acid anhydrides is so great that the consumption of acid anhydrides on the positive electrode side is a critical problem.

[0073] Furthermore, these additive decomposition products incorporated and deposited on the positive electrode side not only increase the internal resistance of non-aqueous secondary batteries but also accelerate the degradation of lithium salts. Moreover, the protection of the negative electrode surface, which was the original purpose, becomes insufficient. In order to deactivate the active sites that essentially cause oxidative degradation of non-aqueous electrolytes, the coexistence of components that control Jahn-Teller strain or act as neutralizers is important. For this reason, it is preferable that the positive electrode active material contains at least one metal selected from the group consisting of Al, Sn, In, Fe, V, Cu, Mg, Ti, Zn, Mo, Zr, Sr, and Ba.

[0074] For similar reasons, it is preferable that the surface of the positive electrode active material is coated with a compound containing at least one metal element selected from the group consisting of Zr, Ti, Al, and Nb. It is even more preferable that the surface of the positive electrode active material is coated with an oxide containing at least one metal element selected from the group consisting of Zr, Ti, Al, and Nb. Furthermore, it is particularly preferable that the surface of the positive electrode active material is coated with at least one oxide selected from the group consisting of ZrO2, TiO2, Al2O3, NbO3, and LiNbO2, as this does not hinder the permeation of lithium ions.

[0075] The positive electrode active material may be a lithium-containing compound other than the Li-containing metal oxide represented by the general formula (2) above, and is not particularly limited as long as it contains lithium. Examples of such lithium-containing compounds include composite oxides containing lithium and a transition metal element, metal chalcogenides containing lithium, metal phosphate compounds containing lithium and a transition metal element, and metal silicate compounds containing lithium and a transition metal element. From the viewpoint of obtaining a higher voltage, metal phosphate compounds containing lithium and at least one transition metal element selected from the group consisting of Co, Ni, Mn, Fe, Cu, Zn, Cr, V, and Ti are particularly preferred as lithium-containing compounds. More specifically, lithium-containing compounds are given by the following formula (Xa): Li v M I D2(Xa) {In the formula, D represents the chalcogen element, M I This represents at least one transition metal element, and the value of v is determined by the charge / discharge state of the battery, representing a number between 0.05 and 1.10. The following equation (Xb): Li w M II PO4(Xb) {In formula, M II}, and The following equation (Xc): Li t MIII u SiO4(Xc) {In formula, M III represents at least one transition metal element, the value of t is determined by the battery's charge / discharge state and ranges from 0.05 to 1.10, and u is a number from 0 to 2. Examples of compounds represented by each of these are listed below.

[0076] The lithium-containing compound represented by formula (Xa) above has a layered structure, and the compounds represented by formulas (Xb) and (Xc) above have an olivine structure. These lithium-containing compounds may be modified in such ways as to stabilize the structure, by substituting some of the transition metal elements with Al, Mg, or other transition metal elements, incorporating these metal elements into the grain boundaries, substituting some of the oxygen atoms with fluorine atoms, or coating at least a portion of the surface of the positive electrode active material with another positive electrode active material.

[0077] In this embodiment, the positive electrode active material may be a lithium-containing compound as described above, or it may be a lithium-containing compound in combination with other positive electrode active materials.

[0078] Other positive electrode active materials include, for example, metal oxides or metal chalcogenides having tunnel and layered structures; sulfur; conductive polymers, etc. Examples of metal oxides or metal chalcogenides having tunnel and layered structures include MnO2, FeO2, FeS2, V2O5, V6O 13 Examples of conductive polymers include oxides, sulfides, and selenides of metals other than lithium, such as TiO2, TiS2, MoS2, and NbSe2. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, and polypyrrole.

[0079] The other positive electrode active materials mentioned above can be used individually or in combination of two or more, and there are no particular restrictions. However, it is preferable that the positive electrode active material layer contains at least one transition metal element selected from Ni, Mn, and Co, in order to enable reversible and stable intercalation and release of lithium ions and to achieve a high energy density.

[0080] When a lithium-containing compound and another positive electrode active material are used in combination as the positive electrode active material, the ratio of the lithium-containing compound to the total positive electrode active material is preferably 80% by mass or more, and more preferably 85% by mass or more.

[0081] Examples of conductive additives include graphite, acetylene black, carbon black such as Ketjenblack, and carbon fibers. The content ratio of the conductive additive is preferably 10 parts by mass or less, and more preferably 1 to 5 parts by mass, per 100 parts by mass of positive electrode active material.

[0082] Examples of binders include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, styrene-butadiene rubber, and fluororubber. The binder content is preferably 6 parts by mass or less, and more preferably 0.5 to 4 parts by mass, per 100 parts by mass of positive electrode active material.

[0083] The positive electrode active material layer is formed by dispersing a slurry containing a positive electrode mixture, which is a mixture of the positive electrode active material and, if necessary, a conductive additive and a binder, in a solvent, onto a positive electrode current collector, drying (solvent removal), and pressing if necessary. There are no particular restrictions on the solvent used, and conventionally known solvents can be used. Examples include N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, and water.

[0084] The positive electrode current collector is made of a metal foil such as aluminum foil, nickel foil, or stainless steel foil. The positive electrode current collector may have a carbon coating on its surface or may be processed into a mesh shape. The thickness of the positive electrode current collector is preferably 5 to 40 μm, more preferably 7 to 35 μm, and even more preferably 9 to 30 μm.

[0085] <3. Negative electrode and negative electrode current collector> The negative electrode in this embodiment has a negative electrode active material layer on one or both sides of the current collector. The negative electrode 160 shown in Figures 1 and 2 is composed of a negative electrode active material layer made from a negative electrode mixture and a negative electrode current collector. The negative electrode 160 can function as the negative electrode of a non-aqueous secondary battery.

[0086] The negative electrode active material layer preferably contains a negative electrode active material and, if necessary, a conductive additive and a binder.

[0087] Examples of negative electrode active materials include amorphous carbon (hard carbon), graphite (e.g., artificial graphite, natural graphite), pyrolytic carbon, coke, glassy carbon, calcined organic polymer compounds, mesocarbon microbeads, carbon fibers, activated carbon, carbon colloids, and carbon black, as well as metallic lithium, metal oxides, metal nitrides, lithium alloys, tin alloys, silicon alloys, intermetallic compounds, organic compounds, inorganic compounds, metal complexes, and organic polymer compounds. The negative electrode active material can be used alone or in combination of two or more types.

[0088] From the perspective of increasing the battery voltage, lithium ions are used as the negative electrode active material in the negative electrode active material, resulting in a 0.4V vs. Li / Li + It is preferable to include a material that can absorb at a lower potential.

[0089] Examples of conductive additives include graphite, acetylene black, carbon black such as Ketjenblack, and carbon fibers. The content ratio of the conductive additive is preferably 20 parts by mass or less, and more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the negative electrode active material.

[0090] Examples of binders include carboxymethylcellulose, PVDF, PTFE, polyacrylic acid, and fluororubber. Diene rubbers, such as styrene-butadiene rubber, are also acceptable. The binder content is preferably 10 parts by mass or less, and more preferably 0.5 to 6 parts by mass, per 100 parts by mass of the negative electrode active material.

[0091] The negative electrode active material layer is formed by dispersing a negative electrode mixture, which is a mixture of the negative electrode active material and, if necessary, a conductive additive and a binder, in a solvent, onto a negative electrode current collector, drying (solvent removal), and pressing as necessary. There are no particular restrictions on the solvent used, and conventionally known solvents can be used. Examples include N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, and water.

[0092] The negative electrode current collector is made of a metal foil such as copper foil, nickel foil, or stainless steel foil. The negative electrode current collector may also have a carbon coating on its surface or be processed into a mesh shape. The thickness of the negative electrode current collector is preferably 5 to 40 μm, more preferably 6 to 35 μm, and even more preferably 7 to 30 μm.

[0093] <4. Separator> As shown in Figure 2, in this embodiment, the non-aqueous secondary battery 100 preferably includes a separator 170 between the positive electrode 150 and the negative electrode 160 from the viewpoint of providing safety such as preventing short circuits and shutdown of the positive electrode 150 and the negative electrode 160. The separator 170 is not limited, but may be the same as that provided in known non-aqueous secondary batteries, and a thin insulating film with high ion permeability and excellent mechanical strength is preferred. Examples of separators 170 include woven fabrics, nonwoven fabrics, and microporous films made of synthetic resin, and among these, microporous films made of synthetic resin are preferred.

[0094] Suitable examples of synthetic resin microporous membranes include polyolefin-based microporous membranes, such as those containing polyethylene or polypropylene as the main component, or those containing both of these polyolefins. Examples of nonwoven fabrics include heat-resistant resin porous membranes made of glass, ceramic, polyolefin, polyester, polyamide, liquid crystal polyester, aramid, etc.

[0095] The separator 170 may have a configuration in which one type of microporous membrane is laminated in a single layer or in multiple layers, or it may have two or more types of microporous membranes laminated together. The separator 170 may also have a configuration in which a mixed resin material obtained by melt-kneading two or more types of resin materials is laminated in a single layer or in multiple layers.

[0096] For the purpose of imparting functionality, inorganic particles may be present on the surface or inside the separator, and other organic layers may be further coated or laminated. Furthermore, a cross-linked structure may be included. These methods may be combined as needed to enhance the safety performance of non-aqueous secondary batteries.

[0097] By using such a separator 170, it is possible to achieve the good input / output characteristics and low self-discharge characteristics that are particularly required for lithium-ion batteries used in the high-power applications mentioned above.

[0098] While there are no particular limitations on the film thickness of the microporous membrane that can be used as a separator, it is preferably 1 μm or more from the viewpoint of film strength and preferably 500 μm or less from the viewpoint of permeability. From the viewpoint of use in high-power applications where the heat generation is relatively high and self-discharge characteristics higher than conventional are required, such as in safety tests, and from the viewpoint of windability in large battery winding machines, the film thickness of the microporous membrane is preferably 5 μm to 30 μm, and more preferably 10 μm to 25 μm. Furthermore, when prioritizing both short-circuit resistance and output performance, the film thickness of the microporous membrane is more preferably 15 μm to 25 μm, but when prioritizing both high energy density and output performance, it is more preferably 10 μm to less than 15 μm.

[0099] The porosity of a microporous membrane usable as a separator is preferably 30% to 90%, more preferably 35% to 80%, and even more preferably 40% to 70%, from the viewpoint of following the rapid movement of lithium ions at high power output. Furthermore, if the priority is on improving power output performance while ensuring safety, a porosity of 50% to 70% is particularly preferred for the microporous membrane, and if the importance is on balancing short-circuit resistance and power output performance, a porosity of 40% to less than 50% is particularly preferred.

[0100] For microporous membranes usable as separators, the air permeability should be 1 second / 100 cm, considering the balance between film thickness and porosity. 3 More than 400 seconds / 100cm 3 The following is preferable: 100 seconds / 100 cm 3 More than 350 seconds / 100cm 3 The following is preferable. Furthermore, if prioritizing both short-circuit resistance and output performance, the air permeability of the microporous membrane should be 150 seconds / 100 cm. 3 More than 350 seconds / 100cm 3 The following is particularly preferable, and when prioritizing improved output performance while ensuring safety, 100 seconds / 100 cm 3 More than 150 seconds / 100cm 3A value less than 10 mS / cm is particularly preferred. On the other hand, when a non-aqueous electrolyte with low ionic conductivity is combined with a separator within the above range, the rate of lithium ion migration is limited not by the separator structure, but by the ionic conductivity of the non-aqueous electrolyte, and the expected input / output characteristics tend not to be obtained. For this reason, the ionic conductivity of the non-aqueous electrolyte is preferably 10 mS / cm or higher, more preferably 15 mS / cm, and even more preferably 20 mS / cm. However, the film thickness, air permeability, and porosity of the separator, as well as the ionic conductivity of the non-aqueous electrolyte, are not limited to the above examples.

[0101] <5. Battery casing> The configuration of the battery casing 110 of the non-aqueous secondary battery 100 shown in Figures 1 and 2 is not particularly limited, but for example, either a battery can or a laminate film casing can be used. As the battery can, for example, a metal can made of steel, stainless steel, aluminum, or clad material, such as a rectangular, rectangular tube, cylindrical, elliptical, flat, coin-shaped, or button-shaped can be used. As the laminate film casing, for example, a laminate film consisting of a three-layer structure of heat-melt resin / metal film / resin can be used.

[0102] The laminate film casing can be used by stacking two sheets with the heat-melt resin side facing inward, or by folding the film so that the heat-melt resin side faces inward, and sealing the ends with heat seal. When using the laminate film casing, the positive electrode lead body 130 (or positive electrode terminal and lead tab connected to the positive electrode terminal) may be connected to the positive electrode current collector, and the negative electrode lead body 140 (or negative electrode terminal and lead tab connected to the negative electrode terminal) may be connected to the negative electrode current collector. In this case, the laminate film casing may be sealed with the ends of the positive electrode lead body 130 and the negative electrode lead body 140 (or lead tabs connected to the positive electrode terminal and the negative electrode terminal, respectively) extended to the outside of the casing.

[0103] <6. How to make a battery> The non-aqueous secondary battery 100 in this embodiment is manufactured by a known method using the above-mentioned non-aqueous electrolyte, a positive electrode 150 having a positive electrode active material layer on one or both sides of the current collector, a negative electrode 160 having a negative electrode active material layer on one or both sides of the current collector, a battery casing 110, and a separator 170 if necessary.

[0104] First, a laminate is formed consisting of a positive electrode 150, a negative electrode 160, and, if necessary, a separator 170. For example: An embodiment in which a winding structure is formed by winding a long positive electrode 150 and a negative electrode 160 in a laminated state with the long separator interposed between the positive electrode 150 and the negative electrode 160; An embodiment in which a laminated structure is formed by alternately stacking positive electrode sheets and negative electrode sheets, obtained by cutting a positive electrode 150 and a negative electrode 160 into multiple sheets having a certain area and shape, with a separator sheet in between; An embodiment in which a long separator is folded in a zigzag pattern, and a laminated structure is formed by alternately inserting positive electrode sheets and negative electrode sheets between the zigzag-folded separators; These are possible.

[0105] Next, the laminate described above is housed in the battery casing 110 (battery case), the non-aqueous electrolyte according to this embodiment is poured into the battery case, and the laminate is immersed in the non-aqueous electrolyte and sealed to produce the non-aqueous secondary battery according to this embodiment.

[0106] Alternatively, a non-aqueous secondary battery 100 can be manufactured by first creating a gel-like electrolyte membrane by impregnating a substrate made of polymer material with a non-aqueous electrolyte, forming a laminated structure using a sheet-like positive electrode 150, a negative electrode 160, and the electrolyte membrane, and optionally a separator 170, and then housing it in a battery casing 110.

[0107] Furthermore, if the electrode arrangement is designed such that there is an overlap between the outer edge of the negative electrode active material layer and the outer edge of the positive electrode active material layer, or if there is a section of the non-opposing part of the negative electrode active material layer that is too narrow, then misalignment of the electrodes may occur during battery assembly, potentially degrading the charge-discharge cycle characteristics of the non-aqueous secondary battery. Therefore, it is preferable to fix the position of the electrodes in the electrode body used in the non-aqueous secondary battery in advance using tapes such as polyimide tape, polyphenylene sulfide tape, or polypropylene (PP) tape, or adhesives.

[0108] In this embodiment, since a non-aqueous electrolyte containing acetonitrile is used, due to its high ionic conductivity, lithium ions released from the positive electrode during the initial charge of a non-aqueous secondary battery may diffuse throughout the negative electrode. In non-aqueous secondary batteries, it is common to have a larger negative electrode active material layer than the positive electrode active material layer. However, if lithium ions diffuse and are intercalated in the negative electrode active material layer, even in areas not facing the positive electrode active material layer, these lithium ions will remain in the negative electrode without being released during the initial discharge. As a result, the contribution of these unreleased lithium ions becomes irreversible capacity. For these reasons, non-aqueous secondary batteries using a non-aqueous electrolyte containing acetonitrile may have low initial charge-discharge efficiency.

[0109] On the other hand, if the area of ​​the positive electrode active material layer is larger than that of the negative electrode active material layer, or if the areas are the same, current concentration is more likely to occur at the edges of the negative electrode active material layer during charging, making it easier for lithium dendrites to form.

[0110] For the reasons stated above, there are no particular restrictions on the ratio of the total area of ​​the negative electrode active material layer to the area of ​​the portion where the positive electrode active material layer and the negative electrode active material layer face each other, but it is preferably greater than 1.0 and less than 1.1, more preferably greater than 1.002 and less than 1.09, even more preferably greater than 1.005 and less than 1.08, and particularly preferably greater than 1.01 and less than 1.08. In a non-aqueous secondary battery using a non-aqueous electrolyte containing acetonitrile, the initial charge-discharge efficiency can be improved by reducing the ratio of the total area of ​​the negative electrode active material layer to the area of ​​the portion where the positive electrode active material layer and the negative electrode active material layer face each other.

[0111] Reducing the ratio of the total area of ​​the negative electrode active material layer to the area of ​​the portion where the positive electrode active material layer and the negative electrode active material layer face each other means limiting the proportion of the negative electrode active material layer that does not face the positive electrode active material layer. This makes it possible to minimize the amount of lithium ions absorbed by the portion of the negative electrode active material layer that does not face the positive electrode active material layer (i.e., the amount of lithium ions that are not released from the negative electrode during the first discharge and become irreversible capacity) from the lithium ions released from the positive electrode during the first charge. Therefore, by designing the ratio of the total area of ​​the negative electrode active material layer to the area of ​​the portion where the positive electrode active material layer and the negative electrode active material layer face each other within the above range, it is possible to improve the load characteristics of the battery by using acetonitrile, increase the initial charge-discharge efficiency of the battery, and further suppress the formation of lithium dendrites.

[0112] The non-aqueous secondary battery 100 in this embodiment can function as a battery after the initial charge, but it is stabilized by the decomposition of a portion of the non-aqueous electrolyte during the initial charge. There are no particular restrictions on the method of initial charging, but it is preferable to perform the initial charge at 0.001 to 0.3C, more preferably at 0.002 to 0.25C, and even more preferably at 0.003 to 0.2C. It is also preferable that the initial charge be performed via constant voltage charging in between. A constant current of 1C is required to discharge the design capacity in one hour. By setting a long voltage range in which the lithium salt is involved in the electrochemical reaction, a stable and robust SEI is formed on the electrode (negative electrode 160) surface, which has the effect of suppressing the increase in internal resistance. In addition, the reaction products are not firmly fixed only on the negative electrode 160, but also have a good effect on other components such as the positive electrode 150 and separator 170 in some way. For this reason, it is very effective to perform the initial charge considering the electrochemical reaction of the lithium salt dissolved in the non-aqueous electrolyte.

[0113] In this embodiment, the non-aqueous secondary battery 100 can also be used as a battery pack in which multiple non-aqueous secondary batteries 100 are connected in series or in parallel. From the viewpoint of managing the charge and discharge state of the battery pack, the operating voltage range per battery is preferably 2 to 5V, more preferably 2.5 to 5V, and particularly preferably 2.75V to 5V.

[0114] Although embodiments for carrying out the present invention have been described above, the present invention is not limited to the above embodiments. The present invention can be modified in various ways without departing from its spirit. [Examples]

[0115] The present invention will be described in more detail below with reference to examples. The present invention is not limited to these examples. Unless otherwise specified, the examples were carried out at room temperature.

[0116] [Examples 1-4 and Comparative Examples 1-2] (1) Preparation of non-aqueous electrolyte Under an inert atmosphere, acetonitrile, ethylene sulfite, ethylene carbonate, ethyl methyl carbonate, and vinylene carbonate were mixed to prepare non-aqueous solvents E1 and E2, respectively. However, ethylene sulfite was not contained in E2. The volume ratios of each solvent in non-aqueous solvents E1 and E2 are as follows. (Non-aqueous solvent E1) Acetonitrile:Ethylene sulfite:Ethylene carbonate:Ethyl methyl carbonate:Vinylen carbonate = 20:4:20:54:2 (Non-aqueous solvent E2) Acetonitrile:Ethylene carbonate:Ethyl methyl carbonate:Vinylen carbonate = 20:20:58:2 Furthermore, lithium salts and silyl ester compounds were added to non-aqueous solvents E1 and E2 to the predetermined concentrations shown in Table 1 to prepare non-aqueous electrolytes (S01) to (S14). The B / A ratio in Table 1 is the ratio of the LiPF6 content A mol / L to the lithium-containing imide salt content B mol / L. The abbreviations for the silyl ester compounds are as follows. (Siyl ester compounds) • TMSPi: Tris(trimethylsilyl) phosphite • TMSPa: Tris(trimethylsilyl) phosphate

[0117] [Table 1]

[0118] (2) Fabrication of non-aqueous secondary batteries (2-1) Preparation of the positive electrode (A) A composite oxide of lithium, nickel, manganese, and cobalt as the positive electrode active material (LiNi 0.8 Mn 0.1 Co 0.1 A positive electrode mixture was obtained by mixing (O2), (B) acetylene black powder as a conductive additive, and (C) polyvinylidene fluoride (PVDF) as a binder in a mass ratio of 94:3:3.

[0119] N-methyl-2-pyrrolidone was added as a solvent to the obtained positive electrode mixture to a solid content of 68% by mass, and the mixture was further mixed to prepare a positive electrode mixture-containing slurry. The slurry was applied to one side of a 15 μm thick, 280 mm wide aluminum foil, which would serve as the positive electrode current collector, using a three-roll transfer coater to create a coating pattern with a coating width of 240-250 mm, a coated length of 125 mm, and an uncoated length of 20 mm, while adjusting the basis weight of the slurry. The solvent was then dried and removed in a hot air drying oven. The resulting electrode rolls were trimmed on both sides and subjected to reduced-pressure drying at 130°C for 8 hours. After that, the density of the positive electrode active material layer was reduced to 2.7 g / cm³ using a roll press. 3 By rolling the material in this manner, a positive electrode consisting of a positive electrode active material layer and a positive electrode current collector was obtained. The basis weight excluding the positive electrode current collector was 8.4 mg / cm³. 2 That was the case.

[0120] (2-2) Fabrication of the negative electrode (a) Graphite powder as the negative electrode active material, (b) carbon black powder (Super-P) as a conductive additive, and (c) polyvinylidene fluoride (PVDF) as a binder were mixed in a solid content mass ratio of 90:3:7 to obtain a negative electrode mixture.

[0121] Water was added as a solvent to the obtained negative electrode mixture to a solid content of 45% by mass, and the mixture was further mixed to prepare a negative electrode mixture-containing slurry. The slurry was applied to one side of a copper foil 8 μm thick and 280 mm wide, which would serve as the negative electrode current collector, using a three-roll transfer coater, adjusting the basis weight of the slurry to create a coating pattern with a coating width of 240-250 mm, a coated length of 125 mm, and an uncoated length of 20 mm. The solvent was then dried and removed in a hot air drying oven. The resulting electrode rolls were trimmed on both sides and subjected to reduced-pressure drying at 80°C for 12 hours. After that, the density of the negative electrode active material layer was reduced to 1.3 g / cm³ using a roll press. 3 The material was rolled to obtain a negative electrode consisting of a negative electrode active material layer and a negative electrode current collector. The basis weight excluding the negative electrode current collector was 5.4 mg / cm³. 2 That was the case.

[0122] (2-3) Assembly of non-aqueous secondary batteries A polypropylene gasket was set in a CR2032 type battery case (SUS304 / Al clad), and the positive electrode obtained as described above, punched out in a disc shape with a diameter of 15.958 mm, was set in the center with the positive electrode active material layer facing upwards. A glass fiber filter paper (Advantec, GA-100) punched out in a disc shape with a diameter of 16.156 mm was set on top of that, and 150 μL of non-aqueous electrolyte was injected. Then, the negative electrode obtained as described above, punched out in a disc shape with a diameter of 16.156 mm, was set with the negative electrode active material layer facing downwards. After setting the spacer and spring, the battery cap was fitted and crimped with a crimping machine. Any electrolyte that spilled out of the case was wiped off with a cloth. It was held at 25°C for 12 hours to allow the non-aqueous electrolyte to sufficiently permeate the laminate, thus obtaining a coin-type non-aqueous secondary battery.

[0123] (3) Evaluation of non-aqueous secondary batteries First, the coin-type non-aqueous secondary batteries obtained as described above underwent initial charging and initial charge / discharge capacity measurement according to the procedure in (3-1) below. Next, each coin-type non-aqueous secondary battery was evaluated according to the procedure in (3-2). Charging and discharging were performed using the ACD-M01A charge / discharge device (product name) manufactured by Asuka Electronics Co., Ltd. and the IN804 programmable constant temperature bath (product name) manufactured by Yamato Scientific Co., Ltd.

[0124] Here, 1C refers to the current value at which a fully charged battery is expected to complete discharge in one hour when discharged at a constant current.

[0125] (3-1) Charging and discharging processes and initial charge-discharge efficiency of non-aqueous secondary batteries The ambient temperature of the non-aqueous secondary battery was set to 25°C. It was charged with a constant current of 0.075mA (equivalent to 0.025C) until it reached 3.1V, then charged with a constant current of 0.15mA (equivalent to 0.05C) until it reached 4.2V. Subsequently, charging was continued at a constant voltage of 4.2V until the current decreased to 0.025C. Finally, the battery was discharged to 3.0V with a constant current of 0.45mA (equivalent to 0.15C). The initial charge-discharge efficiency was defined as the ratio of discharge capacity to charge capacity during this charge-discharge cycle.

[0126] Next, the battery was charged with a constant current of 0.6mA, equivalent to 0.2C, until it reached 4.2V. Then, charging continued at a constant voltage of 4.2V until the current decreased to 0.025C. After that, the battery was discharged to 3V with a current of 0.6mA, equivalent to 0.2C. After that, one cycle of charging and discharging was performed as described above.

[0127] (3-2) 50°C Cycle Test For non-aqueous secondary batteries that underwent the initial charge-discharge treatment using the method described in (3-1) above, the ambient temperature was set to 50°C, and the batteries were charged with a constant current of 6mA (equivalent to 2C) until they reached 4.2V. Then, they were charged at a constant voltage of 4.2V until the current decreased to 0.025C. After that, the batteries were discharged to 3V with a current of 6mA (equivalent to 2C). Subsequently, the same charge-discharge procedure was performed 100 times. However, with the intention of evaluating the capacity by varying the charge-discharge speed, for the 1st, 51st, and 101st charge and discharge cycles, the batteries were charged with a constant current of 3mA (equivalent to 1C) until they reached 4.2V, then charged at a constant voltage of 4.2V until the current decreased to 0.025C, and then discharged to 3V with a current of 0.9mA (equivalent to 0.3C).

[0128] The discharge capacity retention rate was calculated by taking the discharge capacity at the 100th cycle of the cycle test, with the discharge capacity at the 2nd cycle of the cycle test set to 100%.

[0129] (3-3) Non-aqueous secondary battery Using the electrolytes shown in Table 2, non-aqueous secondary batteries were assembled as described above, and initial charge-discharge treatments and cycle tests were performed. The interpretation of the test results is described below.

[0130] Table 2 compares the initial charging time and initial charge / discharge efficiency of electrolytes with 0.5% by mass of TMSPi added, and an initial charge / discharge efficiency of 83% or higher is preferred. Here, the initial charging time in the table is the time required for the voltage to rise to 3.1V during the initial charge.

[0131] [Table 2]

[0132] Examples 1-4 show a shorter charging time to 3.1V compared to Comparative Examples 1-2. Below 3.1V, the voltage does not rise even with charging while the electrochemical reaction that forms the film is occurring, but it starts to rise again once the electrochemical reaction is complete. By adjusting the balance between LiPF6 and imide salt in Examples 1-4, charging is completed relatively quickly, and consequently, the initial charge-discharge efficiency is also high. On the other hand, in Comparative Examples 1-2, the time required for the initial charge is long, suggesting that film formation by the electrochemical reaction is delayed. Consequently, the initial charge-discharge efficiency is also lower.

[0133] From the above, it was confirmed that the initial charge / discharge efficiency can be improved by adjusting the B / A ratio to an appropriate range in the embodiment.

[0134] [Examples 5-10 and Comparative Examples 3-10] The discharge capacity retention rate is the ratio of the discharge capacity per cycle to the discharge capacity at the beginning of the cycle. Here, in order to evaluate the capacity retention rate based on the discharge capacity at a discharge rate of 2C, the discharge capacity at 100 cycles was evaluated based on the discharge capacity at 2 cycles in the cycle test as shown in (3-2). A discharge capacity retention rate of 91% or higher is preferable. Table 3 shows the discharge capacity retention rates for electrolytes with different B / A ratios. However, the weight ratio shown for "Siyl ester compound" in Table 3 is the weight ratio to the total amount of non-aqueous electrolyte excluding that silyl ester compound.

[0135] [Table 3]

[0136] In Examples 5-10, the discharge capacity retention rate was higher than 91.0%, and tended to show better capacity retention than electrolytes without silyl phosphite. On the other hand, Comparative Examples 3-6 had no effect from silyl phosphite, and therefore the discharge capacity retention rate was lower than 90.0%. Comparative Examples 7 and 9 had silyl ester compounds added, but the result was 1.5

[0137] Based on the above, it was confirmed in the examples that by adjusting the B / A ratio to an appropriate range and adding ethylene sulfite and silyl phosphite, good film formation during the initial charge was achieved. This is thought to result in high durability. [Industrial applicability]

[0138] The non-aqueous secondary battery of the present invention is expected to be used not only as a battery for automobiles such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles, but also as a battery for industrial use such as power tools, drones, and electric motorcycles, and even as a residential energy storage system. [Explanation of Symbols]

[0139] 100 Nonaqueous secondary battery 110 Battery casing 120 Battery enclosure space 130 Positive electrode lead body 140 Negative electrode lead body 150 positive electrode 160 negative electrode 170 Separator​

Claims

1. A non-aqueous electrolyte comprising a non-aqueous solvent and a lithium salt, The lithium salt is lithium hexafluoride phosphate (LiPF). ６ ) and a lithium-containing imide salt containing lithium bis(fluorosulfonyl)imide (LiFSI), LiPF in the aforementioned non-aqueous electrolyte ６ When the content of is A mol / L and the content of lithium-containing imide salt is B mol / L, then 1.5 < B / A < 18. The aforementioned non-aqueous solvent comprises acetonitrile and ethylene sulfite. The aforementioned non-aqueous electrolyte further contains tris(trimethylsilyl) phosphite, The content of tris(trimethylsilyl) phosphite is 0.05% by mass or more and 2% by mass or less relative to the total amount of the non-aqueous electrolyte. Non-aqueous electrolyte.

2. The non-aqueous electrolyte according to claim 1, wherein the acetonitrile content is 5% by volume or more and 60% by volume or less relative to the non-aqueous electrolyte.

3. The non-aqueous solvent further comprises vinylene carbonate, The volume ratio of vinylene carbonate in the non-aqueous electrolyte is smaller than that of ethylene sulfite. The non-aqueous electrolyte according to claim 1 or 2.

4. A non-aqueous secondary battery comprising a positive electrode having a positive electrode active material layer on one or both sides of a current collector, a negative electrode having a negative electrode active material layer on one or both sides of a current collector, a separator, and a non-aqueous electrolyte according to any one of claims 1 to 3, The positive electrode active material layer is defined by the following general formula (2): Li ｐ Ni ｑ Co ｒ Mn ｓ M ｔ O ｕ ・・・(2) {In the formula, M is at least one metal selected from the group consisting of aluminum (Al), tin (Sn), indium (In), iron (Fe), vanadium (V), copper (Cu), magnesium (Mg), titanium (Ti), zinc (Zn), molybdenum (Mo), zirconium (Zr), strontium (Sr), and barium (Ba), and is in the range of 0 < p < 1.3, 0 < q < 1.2, 0 < r < 1.2, 0 ≤ s < 0.5, 0 ≤ t < 0.3, 0.7 ≤ q + r + s + t ≤ 1.2, 1.8 < u < 2.2, and p is a value determined by the charge / discharge state of the battery.} A non-aqueous secondary battery containing at least one selected from the group consisting of lithium-containing metal oxides represented by [formula].

5. The non-aqueous secondary battery according to claim 4, wherein the nickel (Ni) content ratio q of the lithium-containing metal oxide represented by the general formula (2) is 0.5 < q < 1.2.

Images