Non-aqueous electrolyte and non-aqueous electrolyte battery using the non-aqueous electrolyte

Abstract

To provide a non-aqueous electrolyte which can be used in a non-aqueous electrolyte battery so as to improve the DCR retention after high-temperature storage and inhibit increase in the amount of gas generated after high-temperature storage.SOLUTION: The invention provides a non-aqueous electrolyte for a non-aqueous electrolyte battery having a cathode containing a specific lithium transition metal based compound (B) as a cathode active material. The non-aqueous electrolyte contains a specific compound (A).SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Energy devices, such as lithium-ion secondary batteries and other non-aqueous electrolyte batteries, are being put into practical use in a wide range of applications, from power supplies for so-called consumer electronics such as mobile phones and laptop computers to on-board power supplies for automobiles. However, in recent years, the demand for higher performance in non-aqueous electrolyte batteries has been increasing, and in particular, there is a demand for improvements in various battery characteristics such as higher capacity, low-temperature operation characteristics, high-temperature storage characteristics, cycle characteristics, and overcharge safety. To date, numerous technologies have been investigated regarding the active materials of the positive and negative electrodes, as well as various battery components, including the non-aqueous electrolyte, as means of improving the high-temperature storage characteristics and cycle characteristics of non-aqueous electrolyte secondary batteries.

[0003] Patent Document 1 discloses a non-aqueous electrolyte for lithium-ion secondary batteries containing a specific vinylene carbonate compound and a specific vinylethylene sulfite, in order to provide a lithium-ion secondary battery that suppresses gas generation during continuous charging and has excellent discharge characteristics after continuous charging. Patent Document 2 discloses a non-aqueous electrolyte secondary battery that suppresses the increase in the internal resistance of the battery after high-temperature storage and also suppresses the increase in the internal resistance of the battery when the battery is used at low temperatures after high-temperature storage. This non-aqueous electrolyte contains 2% by mass or less of a specific cyclic unsaturated sultone compound and 2% by mass or less of a specific cyclic sulfite ester. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2005-166553 [Patent Document 2] Japanese Patent Publication No. 2010-92698 [Overview of the project] [Problems that the invention aims to solve]

[0005] The inventors of the present invention have found that while the batteries described in Patent Documents 1 and 2 are effective in suppressing side reactions at the negative electrode due to the cyclic sulfite ester having a carbon-carbon double bond, they have a poor film formation effect at the positive electrode and an insufficient suppression of side reactions at the positive electrode, resulting in problems such as insufficient suppression of gas generation and increase in internal resistance within the battery.

[0006] The present invention has been made to solve the above problems and relates to a non-aqueous electrolyte that can improve the DC resistance (DCR) retention rate after high-temperature storage and suppress the increase in gas generation after high-temperature storage when used in a non-aqueous electrolyte battery, and a non-aqueous electrolyte battery using the non-aqueous electrolyte. [Means for solving the problem]

[0007] In view of the above circumstances, the inventors of the present invention conducted diligent studies and found that the above problems can be solved by using a non-aqueous electrolyte for a non-aqueous electrolyte battery having a positive electrode in which the positive electrode active material contains a specific lithium transition metal compound, and by using a non-aqueous electrolyte containing a specific cyclic sulfur-containing compound, thereby completing the present invention. In other words, the gist of the present invention is as follows:

[0008] [1] A non-aqueous electrolyte for a non-aqueous electrolyte battery having a positive electrode containing a lithium transition metal compound (B) represented by the following compositional formula (1) as the positive electrode active material, Li 1+y MO2···(1) (In compositional formula (1), y is between -0.1 and 0.5, M is a transition metal element containing at least Ni, and the molar ratio of Ni content to the total element content in M ​​(Ni / M) is between 0.40 and 1.0.) A non-aqueous electrolyte characterized in that the non-aqueous electrolyte contains compound (A) represented by formula (I).

[0009]

Chem.

[0010] [2] The non-aqueous electrolyte according to [1], wherein the compound (A) is a compound represented by the following formula (II).

[0011]

Chem.

[0012] According to the present invention, a non-aqueous electrolyte that can be used in a non-aqueous electrolyte battery to improve the DCR maintenance rate after high-temperature storage and suppress the increase in gas generation after high-temperature storage, and a non-aqueous electrolyte battery using the non-aqueous electrolyte can be provided. [Modes for carrying out the invention]

[0013] [1.Non-aqueous electrolyte] The non-aqueous electrolyte of the present invention contains compound (A) represented by formula (I) (hereinafter also referred to as "compound (A)").

[0014] The inventors speculate that the reason why the non-aqueous electrolyte of the present invention exhibits the excellent effects of improving the DC resistance (DCR) retention rate after high-temperature storage and suppressing the increase in gas generation after high-temperature storage when used in a non-aqueous electrolyte battery is as follows. During the charging and discharging of a non-aqueous electrolyte battery, when compound (A) containing carbon-carbon unsaturated bonds in the non-aqueous electrolyte increases in quantity on the positive electrode, compound (A) acts particularly on the Ni portion of the lithium transition metal compound (B) represented by composition formula (1) (hereinafter also referred to as "compound (B)") contained in the positive electrode active material of the positive electrode, forming a film that suppresses side reactions between the positive electrode and the non-aqueous electrolyte. Therefore, in a non-aqueous electrolyte battery using the non-aqueous electrolyte of the present invention, the DCR maintenance rate after high-temperature storage can be improved and the increase in gas generation after high-temperature storage can be suppressed.

[0015] [1-1. Compound (A)] The compound (A) represented by formula (I) (hereinafter also referred to as "compound (A)") contained in the non-aqueous electrolyte of the present invention will be described in detail below.

[0016] [ka]

[0017] In formula (I), X 1 and X 2 Each is independently an oxygen atom or CH2, and R 1 and R 2 Each of these is independently a hydrogen atom, a halogen atom, or a hydrocarbon group, and n is 1 or 2. However, R 1 and R 2 Either one of them is a hydrocarbon group containing at least one carbon-carbon unsaturated bond, and when n is 2, X 1 and X 2 At least one of them is CH2.

[0018] Among these, X 1 X is an oxygen atom. 2 A sulfite ester structure where is an oxygen atom and n is 1; X 1 X is an oxygen atom. 2 Preferably, the structure is a sulfonic acid ester structure where is CH2 and n is 2; X 1 X is an oxygen atom. 2 A sulfite ester structure in which is an oxygen atom and n is 1 is more preferable.

[0019] R 1 and R 2 Either of these is a hydrocarbon group containing at least one carbon-carbon unsaturated bond. Examples of hydrocarbon groups containing at least one carbon-carbon unsaturated bond include alkenyl groups with 2 to 8 carbon atoms, alkynyl groups with 2 to 8 carbon atoms, aryl groups with 4 to 12 carbon atoms, or aralkyl groups with 7 to 10 carbon atoms. The aryl and aralkyl groups include heteroaryl and heteroaralkyl groups in which any carbon atom constituting the aromatic ring is substituted with a heteroatom. 1 , R 2 When is a hydrocarbon group containing a carbon-carbon unsaturated bond, an alkenyl group having 2 to 8 carbon atoms or an alkynyl group having 2 to 8 carbon atoms is preferred, and an alkenyl group having 2 to 8 carbon atoms is more preferred. R 1 and R 2 However, in the case of saturated hydrocarbon groups, examples of hydrocarbon groups include alkyl groups having 1 to 10 carbon atoms.

[0020] Examples of alkenyl groups include vinyl, allyl, methallyl, 2-butenyl, 3-methyl-2-butenyl, 3-butenyl, 4-pentenyl, 5-hexenyl, 6-heptenyl, and 7-octenyl groups. Among these, alkenyl groups having 2 to 6 carbon atoms are preferred from the viewpoint of solubility in the electrolyte, and vinyl and allyl groups are more preferred.

[0021] Examples of alkynyl groups include ethynyl, 2-propynyl, 2-butynyl, 3-butynyl, 4-pentynyl, 5-hexynyl, 6-heptynyl, and 7-octinyl groups. Among these, alkynyl groups with 2 to 6 carbon atoms are preferred from the viewpoint of solubility in the electrolyte, and ethynyl groups are more preferred.

[0022] Examples of aryl groups include phenyl, 1-naphthyl, 2-naphthyl, 2-thienyl, 3-thienyl, 2-furyl, 3-furyl, 2-pyrrolyl, 3-pyrrolyl, and benzyl groups. Among these, aryl groups with 6 to 12 carbon atoms are preferred from the viewpoint of solubility in electrolytes, and phenyl groups are more preferred.

[0023] Examples of aralkyl groups include benzyl groups, phenethyl groups, phenylpropyl groups, phenylbutyl groups, and phenylisopropyl groups. Among these, benzyl groups and phenethyl groups are preferred from the viewpoint of electrolyte solubility, and benzyl groups are more preferred.

[0024] Examples of alkyl groups include methyl, ethyl, n-propyl, iso-propyl, n-butyl, tert-butyl, n-pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups. Among these, alkyl groups having 1 to 6 carbon atoms are preferred from the viewpoint of solubility in the electrolyte, and methyl, ethyl, and iso-propyl groups are more preferred.

[0025] R in equation (I) 1 and R 2 These may be bonded together to form a cyclic structure. Examples of cyclic structures include unsaturated carbon rings other than aromatic rings, such as cyclohexene rings and cyclopentene rings. Among these, cyclohexene rings are preferred from the viewpoint of stability in electrolytes.

[0026] Also, R 1 or R 2 If the group is a hydrocarbon group, the carbon atoms in the hydrocarbon group may be substituted with oxygen atoms, and the hydrogen atoms may be substituted with halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, or iodine atoms.

[0027] Since compound (A) tends to react and increase in volume on the electrode, in formula (I), R 1 and R 2Preferably, each is independently selected from a hydrogen atom, a halogen atom, a vinyl group, and an allyl group, R 1 and R 2 Either one of them is selected from vinyl groups and allyl groups. Among them, R 1 and R 2 A combination in which one of the elements is a vinyl group and the other is a hydrogen atom is preferred.

[0028] Among the compounds (A) represented by formula (I), X 1 X is an oxygen atom. 2 A compound represented by the following formula (II) is preferred, having a sulfite ester structure in which is an oxygen atom and n is 1.

[0029] [ka]

[0030] In formula (II), R 1 and R 2 R in equation (I) 1 and R 2 It is synonymous with [the above].

[0031] Examples of compounds represented by formula (II) include those represented by the following structural formulas.

[0032] [ka]

[0033] [ka]

[0034] [ka]

[0035] Among the compounds listed above, the compound represented by formula (II) is preferably the one represented by the following structural formula.

[0036] [ka]

[0037] Among the compounds represented by formula (II) above, compounds represented by the following structural formula are more preferably included.

[0038] [ka]

[0039] Among the compounds represented by formula (II) above, compounds represented by the following structural formula are even more preferred.

[0040] [ka]

[0041] Among the compounds represented by the above formula (II), the compounds represented by the following structural formula are particularly preferred.

[0042] [ka]

[0043] Among the compounds represented by the above formula (II), the most preferred is the compound represented by the following structural formula.

[0044] [ka]

[0045] Furthermore, specific examples of compounds represented by formula (I) other than those represented by formula (II) are shown below.

[0046] In formula (I), X 1 CH2, X 2Examples of compounds having a sulfone structure where is CH2 and n is 2 include the compounds represented by the following structural formulas.

[0047] [ka]

[0048] In formula (I), X 1 X is an oxygen atom. 2 Examples of compounds having a sulfonic acid ester structure in which is CH2 and n is 2 include the compounds represented by the following structural formulas.

[0049] [ka]

[0050] In formula (I), X 1 CH2, X 2 Examples of compounds having a sulfonic acid ester structure in which is an oxygen atom and n is 2 include the compounds represented by the following structural formulas.

[0051] [ka]

[0052] (Content of compound (A)) The content of compound (A) in the total amount (100% by mass) of the non-aqueous electrolyte is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, preferably 8% by mass or less, more preferably 6% by mass or less, and even more preferably 4% by mass or less. If the content of compound (A) is within this range, the DCR maintenance rate after high-temperature storage can be improved and the increase in gas generation after high-temperature storage can be suppressed in the non-aqueous electrolyte battery. Compound (A) may be used alone or two or more may be used in any combination and ratio. The identification and measurement of the content of the compound represented by formula (I) are performed by nuclear magnetic resonance (NMR) spectroscopy and / or gas chromatography.

[0053] (Mass ratio of compound (A) to electrolyte) In a non-aqueous electrolyte, the mass ratio of compound (A) content (total amount if there are two or more types) to electrolyte content (compound (A) [g] / electrolyte [g]) is usually 0.001 or higher, preferably 0.01 or higher, more preferably 0.02 or higher, even more preferably 0.025 or higher, and even more preferably 0.03 or higher, and usually 0.5 or lower, preferably 0.3 or lower, more preferably 0.2 or lower, and even more preferably 0.1 or lower. If the mass ratio is within this range, the DCR maintenance rate after high-temperature storage can be improved and the increase in gas generation after high-temperature storage can be suppressed in a non-aqueous electrolyte battery. The principle behind this effect is not clear, but it is thought that by setting the mass ratio of compound (A) content to electrolyte content within this range, side reactions of the electrolyte within the battery system are minimized.

[0054] [1-2. Electrolytes] Examples of electrolytes for non-aqueous electrolytes include lithium salts. There are no particular restrictions on the lithium salts used, and any can be used, but examples include lithium fluoroborate salts, lithium fluorophosphate salts, lithium tungstate salts, lithium carboxylate salts, lithium sulfonate salts, lithium imide salts, lithium methide salts, lithium oxalate salts, and fluorine-containing organic lithium salts.

[0055] Among these, from the viewpoint of improving low-temperature power characteristics, high-rate charge / discharge characteristics, impedance characteristics, high-temperature storage characteristics, and cycle characteristics, lithium fluoroborate salts such as LiBF4; lithium fluorophosphate salts such as LiPF6, Li2PO3F, and LiPO2F2; lithium sulfonate salts such as LiSO3F and LiCH3SO3; and lithium imide salts such as LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethanedisulfonylimide, and lithium cyclic 1,3-perfluoropropanedi Sulfonylimide; LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3 as lithium methide salts; lithium difluorooxalate borate, lithium bis(oxalate) borate, lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, lithium tris(oxalate) phosphate, etc. are preferred as lithium oxalate salts, one or more selected from LiPF6, LiN(FSO2)2, lithium bis(oxalate) borate, and LiSO3F are more preferred, and LiPF6 is particularly preferred.

[0056] The above electrolytes can be used individually or in combination of two or more in any ratio. There are no particular restrictions on the combination of two or more electrolytes, and examples include combinations of LiPF6 and LiN(FSO2)2, LiPF6 and LiBF4, LiPF6 and LiN(CF3SO2)2, LiBF4 and LiN(FSO2)2, and LiBF4, LiPF6 and LiN(FSO2)2. Among these, combinations of LiPF6 and LiN(FSO2)2, LiPF6 and LiBF4, and LiBF4, LiPF6 and LiN(FSO2)2 are preferred.

[0057] While there are no particular restrictions on the total concentration of the electrolyte, from the viewpoint of ensuring proper electrical conductivity for battery operation and sufficient output characteristics, it is usually 8% by mass or more, preferably 8.5% by mass or more, more preferably 9% by mass or more, relative to the total amount of the non-aqueous electrolyte, and also usually 18% by mass or less, preferably 17% by mass or less, more preferably 16% by mass or less. Identification and measurement of the electrolyte content are performed by nuclear magnetic resonance (NMR) spectroscopy and / or ion chromatography.

[0058] [1-3. Non-aqueous solvents] Non-aqueous electrolytes, like general non-aqueous electrolytes, contain a non-aqueous solvent. There are no particular restrictions on the non-aqueous solvent as long as it dissolves the electrolyte mentioned above; known organic solvents can be used. Examples of organic solvents include, but are not limited to, saturated cyclic carbonates, linear carbonates, linear carboxylic acid esters, cyclic carboxylic acid esters, cyclic ether compounds, and sulfone compounds.

[0059] Organic solvents can be used individually or in combination of two or more in any ratio. There are no particular restrictions on the combination of two or more organic solvents, but examples include combinations of saturated cyclic carbonates and linear carbonates, combinations of cyclic carboxylic acid esters and linear carbonates, and combinations of saturated cyclic carbonates, linear carbonates and linear carboxylic acid esters. Among these, combinations of saturated cyclic carbonates and linear carbonates, and combinations of saturated cyclic carbonates, linear carbonates and linear carboxylic acid esters are preferred, combinations of saturated cyclic carbonates and linear carbonates are more preferred, and combinations of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate are even more preferred.

[0060] [1-3-1. Saturated Cyclic Carbonates] Examples of saturated cyclic carbonates include those having alkylene groups with 2 to 4 carbon atoms. From the viewpoint of improving battery characteristics due to an increased degree of dissociation of metal ions, particularly lithium ions, saturated cyclic carbonates having alkylene groups with 2 to 3 carbon atoms are preferred. Specific examples of saturated cyclic carbonates include ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate or propylene carbonate is preferred, and ethylene carbonate, which is less susceptible to oxidation and reduction, is more preferred. Saturated cyclic carbonates can be used individually or in combination of two or more in any ratio.

[0061] The content of saturated cyclic carbonate is not particularly limited and is arbitrary as long as it does not impair the effects of the invention according to this embodiment. The content of saturated cyclic carbonate is usually 3% by volume or more, preferably 5% by volume or more, relative to the total amount of non-aqueous solvent, while it is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. By keeping it within this range, a decrease in electrical conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte is avoided, making it easier to achieve good high-current discharge characteristics, stability to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery, improving the oxidation-reduction resistance of the non-aqueous electrolyte and tending to improve stability during high-temperature storage. In this specification, volume percent refers to volume percent at 25°C and 1 atmosphere.

[0062] [1-3-2. Chain-like carbonates] Examples of chain-like carbonates include those having 3 to 7 carbon atoms, and chain-like carbonates having 3 to 5 carbon atoms are preferred in order to adjust the viscosity of the non-aqueous electrolyte to an appropriate range. Specific examples of chain-like carbonates include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propylisopropyl carbonate, ethyl methyl carbonate, and methyl-n-propyl carbonate, and preferably one or more selected from dimethyl carbonate and ethyl methyl carbonate. Furthermore, chain-like carbonates containing fluorine atoms (hereinafter also referred to as "fluorinated chain-like carbonates") can also be suitably used. The number of fluorine atoms in a fluorinated chain-like carbonate is not particularly limited as long as it is 1 or more, but is preferably 6 or less, and more preferably 4 or less. When a fluorinated chain-like carbonate has multiple fluorine atoms, these multiple fluorine atoms may be bonded to the same carbon or to different carbons. Examples of fluorinated chain carbonates include fluorinated dimethyl carbonate derivatives such as fluoromethylmethyl carbonate; fluorinated ethylmethyl carbonate derivatives such as 2-fluoroethylmethyl carbonate; and fluorinated diethyl carbonate derivatives such as ethyl-(2-fluoroethyl) carbonate. Chain-like carbonates can be used individually or in combination of two or more types in any ratio.

[0063] The content of chain-like carbonates is not particularly limited, but from the viewpoint of setting the viscosity of the non-aqueous electrolyte within an appropriate range, suppressing a decrease in ionic conductivity, and thereby improving the output characteristics of the non-aqueous electrolyte battery, it is usually 15% by volume or more, preferably 20% by volume or more, more preferably 25% by volume or more, and also usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less, relative to the total amount of non-aqueous solvent in the non-aqueous electrolyte.

[0064] Furthermore, by combining specific chain-like carbonates with ethylene carbonate in specific quantities, battery performance can be significantly improved. For example, when dimethyl carbonate and ethyl methyl carbonate are selected as the specific chain carbonates, the ethylene carbonate content is typically 15% by volume or more, preferably 20% by volume or more, and typically 45% by volume or less, preferably 40% by volume or less, relative to the total amount of solvent in the non-aqueous electrolyte, from the viewpoint of improving high-temperature stability and suppressing gas generation. The dimethyl carbonate content is typically 20% by volume or more, preferably 25% by volume or more, and typically 40% by volume or less, preferably 35% by volume or less, relative to the total amount of non-aqueous solvent in the non-aqueous electrolyte. The ethyl methyl carbonate content is typically 20% by volume or more, preferably 25% by volume or more, and typically 40% by volume or less, preferably 35% by volume or less, relative to the total amount of non-aqueous solvent in the non-aqueous electrolyte.

[0065] [1-3-3. Chain-like carboxylic acid esters] Examples of linear carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, methyl valerate, methyl isobutyrate, ethyl isobutyrate, and methyl pivalate. Among these, methyl acetate, ethyl acetate, propyl acetate, and butyl acetate are preferred from the viewpoint of improving battery characteristics. Linear carboxylic acid esters in which some of the hydrogen atoms of the above compounds are substituted with fluorine atoms (for example, methyl trifluoroacetate, ethyl trifluoroacetate, etc.) can also be suitably used. When a chain-like carboxylic acid ester is included, the amount it is added is usually 1% by volume or more, preferably 5% by volume or more, and more preferably 15% by volume or more, relative to the total amount of the non-aqueous solvent, from the viewpoint of improving the electrical conductivity of the non-aqueous electrolyte and improving the high-current discharge characteristics of the non-aqueous electrolyte battery. Furthermore, the upper limit of the amount added is usually 70% by volume or less, preferably 50% by volume or less, and more preferably 40% by volume or less, from the viewpoint of keeping the viscosity of the non-aqueous electrolyte within an appropriate range, avoiding a decrease in electrical conductivity, suppressing an increase in negative electrode resistance, and keeping the high-current discharge characteristics of the non-aqueous electrolyte battery within a good range.

[0066] [1-3-4. Cyclic carboxylic acid esters] Examples of cyclic carboxylic acid esters include γ-butyrolactone and γ-valerolactone. Of these, γ-butyrolactone is more preferred. Cyclic carboxylic acid esters obtained by substituting some of the hydrogen atoms of the above compounds with fluorine atoms can also be suitably used. When the non-aqueous electrolyte contains a cyclic carboxylic acid ester, its content is usually 1% by volume or more, preferably 5% by volume or more, and more preferably 15% by volume or more, relative to the total amount of the non-aqueous solvent, from the viewpoint of improving the electrical conductivity of the non-aqueous electrolyte and improving the high-current discharge characteristics of the non-aqueous electrolyte battery. Furthermore, the upper limit of its blending amount is usually 70% by volume or less, preferably 50% by volume or less, and more preferably 40% by volume or less, from the viewpoint of keeping the viscosity of the non-aqueous electrolyte within an appropriate range, avoiding a decrease in electrical conductivity, suppressing an increase in negative electrode resistance, and keeping the high-current discharge characteristics of the non-aqueous electrolyte battery within a good range.

[0067] [1-3-5. Cyclic ether compounds] Examples of cyclic ether compounds include cyclic ethers having 3 to 6 carbon atoms, such as tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, and 1,4-dioxane. Some of the hydrogen atoms in these cyclic ether compounds may be substituted with fluorine atoms. Among these, tetrahydrofuran, 1,3-dioxane, and 1,4-dioxane are preferred from the viewpoint of providing high ionic conductivity.

[0068] When the non-aqueous electrolyte contains a cyclic ether compound, its content is arbitrary as long as it does not impair the effects of the present invention, but is usually 1% by volume or more, preferably 2% by volume or more, more preferably 3% by volume or more, and usually 30% by volume or less, preferably 25% by volume or less, and more preferably 20% by volume or less, relative to the total amount of non-aqueous solvent in the non-aqueous electrolyte. If the content of the cyclic ether compound is within the above range, it is easy to ensure the effect of improving the degree of dissociation of metal ions, especially lithium ions, by the cyclic ether compound and improving ionic conductivity due to the reduction in viscosity of the non-aqueous electrolyte. Furthermore, when the negative electrode active material is a carbon-based material, the phenomenon of co-insertion of chain-like ethers together with metal ions, especially lithium ions, can be suppressed, so that the input / output characteristics and charge / discharge rate characteristics can be set within an appropriate range.

[0069] [1-3-6. Sulfone compounds] The sulfone compound is not particularly limited and may be a cyclic sulfone or a linear sulfone. In the case of a cyclic sulfone, the number of carbon atoms is usually 3 to 6, preferably 3 to 5, and in the case of a linear sulfone, the number of carbon atoms is usually 2 to 6, preferably 2 to 5. Furthermore, the number of sulfonyl groups in one molecule of the sulfone compound is not particularly limited, but is usually 1 or 2. Examples of cyclic sulfones include monosulfone compounds such as trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones; and disulfone compounds such as trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones. Among these, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferred from the viewpoint of dielectric constant and viscosity, and tetramethylene sulfones (sulfolanes) are even more preferred. Sulfolanes and sulfolane derivatives are preferred as sulforanes. Sulfolane derivatives are preferred in which one or more hydrogen atoms bonded to the carbon atoms constituting the sulfolane ring are substituted with fluorine atoms, alkyl groups, or fluorine-substituted alkyl groups. Among these, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,3-difluorosulfolane, 2-trifluoromethylsulfolane, and 3-trifluoromethylsulfolane are preferred because they have high ionic conductivity and high input / output properties.

[0070] Furthermore, examples of chain-like sulfones include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, and pentafluoroethyl methyl sulfone. Among these, dimethyl sulfone, ethyl methyl sulfone, and monofluoromethyl methyl sulfone are preferred because they improve the high-temperature storage stability of non-aqueous electrolytes. If the non-aqueous electrolyte contains a sulfone compound, the amount is arbitrary as long as it does not impair the effects of the present invention. However, from the viewpoint of improving high-temperature storage stability, the amount is usually 0.3% by volume or more, preferably 0.5% by volume or more, more preferably 1% by volume or more, relative to the total amount of the non-aqueous solvent in the non-aqueous electrolyte, and is usually 40% by volume or less, preferably 35% by volume or less, more preferably 30% by volume or less.

[0071] [1-4. Auxiliary Agents] Examples of additives that may be included in non-aqueous electrolytes include cyclic carbonates having carbon-carbon unsaturated bonds, fluorine-containing cyclic carbonates, compounds having isocyanate groups, organic compounds having an isocyanuric acid skeleton, sulfur-containing organic compounds, phosphorus-containing organic compounds, organic compounds having cyano groups, silicon-containing compounds, aromatic compounds, fluorine-free carboxylic acid esters, cyclic compounds having ether bonds, carboxylic acid anhydrides, compounds containing borate anions, compounds containing phosphate anions having PF and P=O bonds, compounds containing anions having S=O bonds, and compounds containing oxalate complex anions. For example, compounds described in International Publication No. 2015 / 111676 can be cited.

[0072] The content of the auxiliary agent is not particularly limited and is arbitrary as long as it does not significantly impair the effects of the present invention, but is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably less than 1% by mass, relative to the total amount of the non-aqueous electrolyte.

[0073] Cyclic compounds containing ether bonds can be used as additives in non-aqueous electrolytes, and some can also be used as non-aqueous solvents, as shown in [1-3. Non-aqueous Solvents]. When using cyclic compounds having ether bonds as additives, it is preferable to use them in an amount of less than 4% by mass. Compounds containing borate anions, compounds containing oxalate complex anions, compounds containing monofluorophosphate anions, and compounds containing difluorophosphate anions can also be used as additives in non-aqueous electrolytes, and some can be used as electrolytes as shown in [1-2. Electrolytes]. When using these compounds as additives, it is preferable to use them in an amount of less than 3% by mass.

[0074] [1-4-1. Compounds containing phosphate anions having PF bonds and P=O bonds, compounds containing anions having S=O bonds, and compounds containing oxalate complex anions] Among the auxiliary agents described above, at least one anion-containing compound selected from phosphate anion-containing compounds having PF bonds and P=O bonds, anion-containing compounds having S=O bonds, and oxalate complex anion-containing compounds (hereinafter also referred to as "specific anion-containing compounds") is preferred because it easily forms a stable film on the electrode, further suppresses deterioration of the DCR maintenance rate after high-temperature storage in non-aqueous electrolyte batteries, and further suppresses the increase in gas generation after high-temperature storage. The following describes specific anion-containing compounds.

[0075] At least one anion-containing compound selected from phosphate-containing compounds having PF bonds and P=O bonds, anion-containing compounds having S=O bonds, and oxalate complex anion-containing compounds may be used individually or in any combination and ratio of two or more. Among these, compounds containing phosphate anions having PF bonds and P=O bonds are preferred from the viewpoint of suppressing the increase in gas generation after high-temperature storage.

[0076] (Content of specific anion-containing compounds) When a non-aqueous electrolyte contains a specific anion-containing compound, the content of the specific anion-containing compound (total amount if there are two or more types) in the total amount of the non-aqueous electrolyte (100% by mass) is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass or less. If the content of the specific anion-containing compound is within this range, the deterioration of battery characteristics, especially the DCR maintenance rate after high-temperature storage, can be significantly suppressed, and the increase in gas generation after high-temperature storage can be significantly suppressed. The principle behind this effect is not clear, but it is thought that if the content of the specific anion-containing compound is within this range, side reactions of the components of the non-aqueous electrolyte on the electrode can be minimized. The identification and measurement of the content of specific anion-containing compounds are performed by nuclear magnetic resonance (NMR) spectroscopy and / or ion chromatography.

[0077] (Mass ratio of a specific anion-containing compound to compound (A)) The mass ratio of the content of a specific anion-containing compound (total amount if there are two or more) to the content of compound (A) (specific anion-containing compound [g] / compound (A) [g]) is usually 0.01 or higher, preferably 0.05 or higher, more preferably 0.3 or higher, and usually 100 or lower, preferably 10 or lower, more preferably 5 or lower, and even more preferably 4 or lower. If this mass ratio is within this range, the deterioration of battery characteristics, especially the DCR maintenance rate after high-temperature storage, can be significantly suppressed, and the increase in gas generation after high-temperature storage can be significantly suppressed. The principle behind this is not clear, but it is thought that by including compound (A) and the specific anion-containing compound within this mass ratio range, side reactions of the non-aqueous electrolyte components on the electrode can be minimized.

[0078] (Mass ratio of a specific anion-containing compound to an electrolyte) When a non-aqueous electrolyte contains a specific anion-containing compound, the mass ratio of the content of the specific anion-containing compound (total amount if there are two or more) to the electrolyte content (specific anion-containing compound [g] / electrolyte [g]) is usually 0.00005 or higher, preferably 0.001 or higher, more preferably 0.01 or higher, even more preferably 0.02 or higher, particularly preferably 0.025 or higher, usually 0.5 or lower, preferably 0.45 or lower, more preferably 0.4 or lower, and even more preferably 0.35 or lower. If the mass ratio is within this range, the deterioration of battery characteristics, especially the DCR maintenance rate after high-temperature storage, can be significantly suppressed, and the increase in gas generation after high-temperature storage can be significantly suppressed. The principle behind this effect is not clear, but it is thought that by containing the specific anion and electrolyte within this mass ratio range, side reactions of the electrolyte within the battery system are minimized.

[0079] [1-4-1-1. Compounds containing phosphate anions with PF bonds and P=O bonds] The phosphate anion-containing compound having a PF bond and a P=O bond is not particularly limited as long as it is an anion-containing compound derived from phosphoric acid that has a PF bond and a P=O bond in its molecule. Examples of phosphoric acid having a PF bond and a P=O bond include monofluorophosphate represented by the molecular formula H2PO3F and difluorophosphate represented by the molecular formula HPO2F2. Examples of countercations of phosphate anions having PF bonds and P=O bonds include alkali metal cations such as lithium, sodium, and potassium, with lithium cations being particularly preferred. Examples of salts of phosphate anions having PF and P=O bonds include salts of monofluorophosphate anions such as Li2PO3F; and salts of difluorophosphate anions such as LiPO2F2, NaPO2F2, and KPO2F2. In particular, from the viewpoint of balancing the output characteristics of the battery and electrode interface protection, salts of difluorophosphate anions are preferred, and lithium difluorophosphate is more preferred.

[0080] [1-4-1-2. Anion-containing compounds with an S=O bond] There are no particular restrictions on the anion-containing compound having an S=O bond, as long as it has an S=O bond in its molecule, and any compound can be used as long as it does not significantly impair the effects of the present invention. Examples of anion-containing compounds having an S=O bond include fluorosulfonic acid represented by the molecular formula HSO3F, fluorosulfonylimide represented by the molecular formula HN(FSO2), fluorosulfonylmethide represented by the molecular formula HC(FSO2)3, and alkylsulfuric acid such as CH3SO4H. In addition to alkali metal cations such as lithium, sodium, and potassium, (CH3)4N can be used as countercations for anions with an S=O bond. + (C2H5)4N + (n-C4H9)4N + Examples of quaternary ammonium cations include the above, with lithium cations being preferred. Examples of salts of anions having an S=O bond include salts of fluorosulfonic acid anions such as LiSO3F, NaSO3F, KSO3F, (CH3)4NSO3F, (C2H5)4NSO3F, and (n-C4H9)4NSO3F; salts of fluorosulfonylimide anions such as LiN(FSO2)2 and LiN(FSO2)(CF3SO2); salts of fluorosulfonylmethide anions such as LiC(FSO2)3; and salts of alkyl sulfate anions such as LiCH3SO4 and LiC2H5SO4. In particular, from the viewpoint of balancing the output characteristics of the battery and the protection of the electrode interface, a salt of fluorosulfonate anion or a salt of fluorosulfonylimide anion is preferred, a salt of fluorosulfonate anion is more preferred, and lithium fluorosulfonate is even more preferred.

[0081] [1-4-1-3. Compounds containing oxalate complex anions] The oxalate complex anion-containing compound used in the present invention is not particularly limited as long as it is an anion-containing compound having an oxalate complex in its molecule. An oxalate complex anion is an acid anion in which oxalic acid is coordinated to or bonded to a central atom to form a complex. Examples include boron oxalate complex anions in which oxalic acid is coordinated to or bonded to a boron atom, such as bis(oxalate)borate and difluorooxalateborate, and phosphorus oxalate complex anions in which oxalic acid is coordinated to or bonded to a phosphorus atom, such as tris(oxalate)phosphate, difluorobis(oxalate)phosphate and tetrafluorooxalatephosphate. Examples of countercations for the oxalate complex anion include alkali metal cations such as lithium, sodium, and potassium, with lithium cations being particularly preferred. Examples of salts of oxalate complex anions include salts of boron oxalate complex anions such as lithium bis(oxalate)borate and lithium difluorooxalateborate; and salts of phosphorus oxalate complex anions such as lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate)phosphate and lithium tris(oxalate)phosphate. In particular, from the viewpoint of forming a stable co-coating on the electrode surface, a salt of a boron oxalate complex anion is preferred, and lithium bis(oxalate)borate is more preferred.

[0082] [2.Nonaqueous electrolyte battery] The non-aqueous electrolyte battery of the present invention is a non-aqueous electrolyte battery comprising a positive electrode having a positive electrode active material capable of intercalating and releasing metal ions, and a negative electrode having a negative electrode active material capable of intercalating and releasing metal ions, characterized in that it comprises the above-mentioned non-aqueous electrolyte. Furthermore, without departing from the spirit of the present invention, it is also possible to use a mixture of other non-aqueous electrolytes with the non-aqueous electrolyte of the present invention. Examples of non-aqueous electrolyte batteries of the present invention include polyvalent cation batteries, metal-air secondary batteries, and secondary batteries using s-block metals other than those mentioned above, with non-aqueous electrolyte secondary batteries being preferred and lithium-ion secondary batteries being more preferred.

[0083] [2-1. Positive electrode] The positive electrode has a positive electrode active material capable of intercalating and releasing lithium ions on at least a portion of the current collector surface. The positive electrode active material contains a lithium transition metal compound (B).

[0084] [2-1-1. Positive electrode active material] The positive electrode active material (lithium transition metal compound (B)) used in the positive electrode is described below.

[0085] [2-1-1-1. Lithium transition metal compounds (B)] Compound (B) is a compound having a layered structure capable of desorbing and inserting lithium ions, and is represented by the following compositional formula (1). Li 1+y MO₂(1) In the compositional formula (1), y satisfies -0.1 ≤ y ≤ 0.5, M is a transition metal containing at least Ni, and the molar ratio (Ni / M) of the content of Ni to the total content of all elements contained in M is 0.40 or more, preferably 0.50 or more, more preferably 0.55 or more, and 1.0 or less, preferably 0.90 or less, more preferably 0.80 or less. If the molar ratio is within this range, the compound (A) is likely to form a film on the positive electrode, suppressing the side reaction between the positive electrode and the non-aqueous electrolyte, thereby improving the DCR retention rate after high-temperature storage of the non-aqueous electrolyte battery and suppressing the increase in the amount of gas generated after high-temperature storage.

[0086] Specific examples of the oxide represented by the compositional formula (1) include LiNiO₂, LiNi 0.85 Co 0.10 Al 0.05 O₂, LiNi 0.80 Co 0.15 Al 0.05 O₂, LiNi 0.5 Co 0.2 Mn 0.3 O₂, Li 1.05 Ni 0.5 Co 0.2 Mn 0.3 O₂, LiNi 0.6 Co 0.2 Mn 0.2 O₂, LiNi 0.8 Co 0.1 Mn 0.1 O₂, LiNi 0.91 Co 0.06 Mn 0.03 O₂, LiNi 0.91 Co 0.06 Al 0.03 O₂, LiNi 0.90 Co 0.03 Al 0.07 O₂, Li 1.00 Ni 0.61 Co 0.20 Mn 0.19 and the like.

[0087] ​​Among these, from the viewpoint of improving the battery capacity, a lithium transition metal composite oxide having a layered structure is preferable, and a lithium transition metal composite oxide represented by the following compositional formula (2) is more preferable. Li a1 Ni b1 M c1 O2(2) In the compositional formula (2), a1, b1, and c1 are respectively 0.90 ≦ a1 ≦ 1.10, 0.40 ≦ b1 ≦ 0.98, 0.02 ≦ c1 ≦ 0.60, and b1 + c1 = 1. M represents at least one element selected from the group consisting of Co, Mn, Al, Mg, Zr, Fe, Ti, and Er. In the compositional formula (2), b1 is preferably 0.50 or more, and more preferably 0.60 or more.

[0088] In particular, from the viewpoint of the structural stability of the lithium transition metal composite oxide, it is preferable that the lithium transition metal composite oxide is represented by the following compositional formula (3). Li a2 Ni b2 Co c2 M d2 O2(3) In the compositional formula (3), a2, b2, c2, and d2 are respectively 0.90 ≦ a2 ≦ 1.10, 0.40 ≦ b2 ≦ 0.98, 0.01 ≦ c2 ≦ 0.60, and 0.01 ≦ d2 ≦ 0.60, and b2 + c2 + d2 = 1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er. In the above compositional formula (3), b2 is preferably 0.50 or more, and more preferably 0.60 or more. Also, d2 is preferably 0.01 or more, and more preferably 0.10 or more. Preferable examples of the lithium transition metal composite oxide represented by the above compositional formula (3) include LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.80 Co 0.15 Al 0.05 O2, LiNi 0.8 Co<​​​​​​​0.03 O2, LiLiLi 0.91 Co 0.06 Al 0.03 O2, LiLiLi 0.90 Co 0.03 Al 0.07 O2, Li 1.00 Ni 0.61 Co 0.20 Mn 0.19 Examples include O2. In the above compositional formula (1) or (2), it is preferable that M contains Mn or Al, from the viewpoint of enhancing the structural stability of the lithium transition metal composite oxide and suppressing structural degradation during repeated charging and discharging. In the above compositional formula (3), from the viewpoint of enhancing the structural stability of the lithium transition metal composite oxide and suppressing structural degradation during repeated charging and discharging, M preferably contains Mn or Al, and more preferably Mn.

[0089] [2-1-1-2. Introduction of different elements] Furthermore, lithium transition metal composite oxides may contain elements other than those included in any of the above compositional formulas (1) to (3) (other elements).

[0090] [2-1-1-3. Surface coating] As the positive electrode, a positive electrode active material may be used in which a substance with a different composition from the positive electrode active material (surface-adhered substance) is attached to its surface. Examples of surface-adhering substances include oxides such as aluminum oxide, sulfates such as lithium sulfate, and carbonates such as lithium carbonate. These surface-adhering substances can be attached to the surface of the positive electrode active material by, for example, dissolving or suspending them in a solvent, impregnating them into the positive electrode active material, and then drying them. The amount of surface-adhering material is preferably 1 μmol / g or more, more preferably 10 μmol / g or more, and usually 1 mmol / g or less, relative to the positive electrode active material. In this specification, a positive electrode active material with the above-mentioned surface-adhered substance attached to its surface is also referred to as a "positive electrode active material."

[0091] [2-1-1-4. Blend] The positive electrode active material can be used alone or in combination of two or more materials in any ratio.

[0092] [2-1-2. Cathode Configuration and Manufacturing Method] The positive electrode using positive electrode active material can be manufactured by conventional methods. Specifically, the positive electrode can be obtained by a coating method in which the positive electrode active material, binder, and optionally conductive material and thickener are dry-mixed to form a sheet, which is then pressed onto the positive electrode current collector, or by dissolving or dispersing these materials in a liquid medium such as an aqueous solvent or an organic solvent to form a slurry, which is then applied to the positive electrode current collector and dried to form a positive electrode active material layer on the current collector. Alternatively, for example, the above positive electrode active material may be roll-molded to form a sheet electrode, or it may be compressed to form a pellet electrode. The following describes the process of sequentially applying and drying the slurry onto the positive electrode current collector.

[0093] [2-1-2-1. Content of positive electrode active material] The content of the positive electrode active material in the positive electrode active material layer is typically between 80% by mass and 99.5% by mass.

[0094] [2-1-2-2. Electrode density] The positive electrode active material layer obtained by coating and drying is preferably compacted by hand pressing, roller pressing, or the like to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer present on the current collector is typically 1.5 g / cm³. 3 More than 4.5g / cm 3 The following applies:

[0095] [2-1-2-3. Conductive Materials] Any known conductive material can be used as the conductive material. Specific examples include metallic materials such as copper and nickel; graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbon-based materials such as amorphous carbon such as needle coke. The conductive material can be used alone or in combination of two or more materials in any ratio. The conductive material is usually contained in the positive electrode active material layer in an amount of 0.01% by mass or more and 50% by mass or less.

[0096] [2-1-2-4. Binding agent] When forming the positive electrode active material layer by a coating method, the type of binder used is not particularly limited as long as it is a material that can be dissolved or dispersed in the liquid medium for the slurry. For example, fluororesins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene are preferred due to their weather resistance, chemical resistance, heat resistance, and flame retardancy; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide are preferred. Furthermore, mixtures of the above polymers, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, etc., can also be used. The binder can be used alone or in combination of two or more types in any ratio. Furthermore, when a resin is used as a binder, the weight-average molecular weight of the resin can be arbitrary as long as it does not impair the effects of the present invention, and is usually between 10,000 and 3,000,000. When the molecular weight is within this range, the strength of the electrode is improved, and the electrode can be formed suitably. The binder content in the positive electrode active material layer is typically between 0.1% by mass and 80% by mass.

[0097] [2-1-2-5. Current Collector] The material of the positive electrode current collector is not particularly limited, and any known material can be used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, with aluminum being preferred. Examples of current collector shapes include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punched metal, and foamed metal. Among these, metal foil or metal thin film is preferred. The metal thin film may be formed in a mesh shape as appropriate. When the shape of the positive electrode current collector is plate-shaped or film-shaped, the thickness of the current collector can be arbitrary, but is usually between 1 μm and 1 mm.

[0098] [2-1-2-6. Thickness of the positive electrode plate] The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the positive electrode active material layer, obtained by subtracting the thickness of the current collector from the thickness of the positive electrode plate, is usually between 10 μm and 500 μm on one side of the current collector.

[0099] [2-1-2-7. Surface coating of the positive electrode plate] The positive electrode plate may be one on which a substance with a different composition from the positive electrode plate is attached to its surface, and the same substance as the surface-attached substance that may be attached to the surface of the positive electrode active material is used.

[0100] [2-2. Negative electrode] The negative electrode has negative electrode active material on at least a portion of the current collector surface. [2-2-1. Negative electrode active material] There are no particular restrictions on the negative electrode active material used in the negative electrode, as long as it is electrochemically capable of intercalating and releasing metal ions. Specific examples include (i) carbon-based materials, (ii) particles containing metal elements and / or metalloid elements that can alloy with Li, (iii) lithium-containing metal composite oxide materials, and (iv) mixtures thereof. Among these, it is preferable to use (i) carbon-based materials, (ii) particles containing metal elements and / or metalloid elements that can alloy with Li, and (v) mixtures of particles containing metal elements and / or metalloid elements that can alloy with Li and graphite particles, as these offer good cycle characteristics, safety, and excellent continuous charging characteristics. These can be used individually or in combination of two or more in any ratio.

[0101] [2-2-1-1. Carbon-based materials] (i) Examples of carbon-based materials include natural graphite, artificial graphite, amorphous carbon, carbon-coated graphite, graphite-coated graphite, and resin-coated graphite. Among these, natural graphite is preferred. Carbon-based materials can be used individually or in combination of two or more in any ratio. Examples of natural graphite include scaly graphite, flake graphite, and / or graphite particles obtained by treating these graphites, such as spheroidization or densification. Among these, spherical or ellipsoidal graphite particles obtained by spheroidization treatment are preferred from the viewpoint of particle packing properties or charge / discharge rate characteristics. The volume-average particle size (d50) of graphite particles is typically between 1 μm and 100 μm.

[0102] [2-2-1-2. Physical Properties of Carbon-Based Materials] The carbon-based material used as the negative electrode active material preferably satisfies at least one of the following physical properties and characteristics such as shape, as shown in (1) to (4), and more preferably satisfies multiple items simultaneously. (1) X-ray diffraction parameters The d-value (interlayer distance) of the lattice plane (002 plane) of carbon-based materials, as determined by X-ray diffraction using the JSPS method, is typically between 0.335 nm and 0.360 nm. Furthermore, the crystallite size (Lc) of carbon-based materials, as determined by X-ray diffraction using the JSPS method, is 1.0 nm or greater. (2) Volume-based average particle size The volume-based average particle size of carbon-based materials is the volume-based average particle size (median diameter) determined by laser diffraction and scattering, and is typically between 1 μm and 100 μm. (3) Raman R value, Raman half-width The Raman R value of carbon-based materials is measured using argon ion laser Raman spectroscopy and is typically between 0.01 and 1.5. Also, 1580 cm² of carbon-based materials -1 The Raman width at half maximum in the vicinity is not particularly restricted, but is usually 10 cm. -1 More than 100cm -1 The following applies: (4) BET specific surface area The BET specific surface area of ​​carbon-based materials is the value of the specific surface area measured using the BET method, and is typically 0.1 m². 2 ·g -1 Over 100m 2 ·g -1 The following applies: The negative electrode active material may contain two or more carbon-based materials with different properties. The properties referred to here are one or more characteristics selected from the group consisting of X-ray diffraction parameters, volume-based average particle size, Raman R value, Raman full width at half maximum, and BET specific surface area. Examples of materials containing two or more carbon-based materials with different properties include those in which the volume-based particle size distribution is not symmetrical when centered on the median diameter, those containing two or more carbon-based materials with different Raman R values, and those with different X-ray parameters.

[0103] [2-2-1-3. Materials containing metallic and / or metalloid elements that can be alloyed with Li] (ii) Any material containing a metal element and / or metalloid element that can be alloyed with Li can be used, but from the viewpoint of capacity and cycle life, it is preferable that the material be a metal or metalloid selected from the group consisting of, for example, Sb, Si, Sn, Al, As, and Zn. Furthermore, if the material containing a metal element and / or metalloid element that can be alloyed with Li contains two or more metals, the material may be an alloy material made of an alloy of these metals. Furthermore, examples of compounds containing metal elements and / or metalloid elements that can alloy with Li include oxides, nitrides, and carbides of metals and / or metalloids. These compounds may contain two or more metal elements and / or metalloid elements that can alloy with Li. Among these, metallic Si (hereinafter also referred to as "Si") or Si-containing inorganic compounds are preferred in terms of increasing capacity. In this specification, Si or Si-containing inorganic compounds are collectively referred to as Si compounds. Furthermore, compounds containing metallic and / or metalloid elements that can be alloyed with Li may already be alloyed with Li during the production of the negative electrode, as described later, and Si compounds are preferred as such in terms of increasing capacity. As for Si compounds, SiO x Examples include (0≦x≦2), etc. Li is a metal alloying compound. z1 Si(0 <z1≦4.4)、Li 2z2 SiO 2+z2(0 < z2 ≤ 2) and the like can be mentioned. As the Si compound, Si oxide (SiO x1 , 0 < x1 ≤ 2) is preferable in that its theoretical capacity is larger than that of graphite, and amorphous Si or nano-sized Si crystals are preferable in that alkali ions such as lithium ions can easily enter and exit, making it possible to obtain a high capacity. When the material containing a metal element and / or a metalloid element capable of alloying with Li is in a particulate state, the volume average particle diameter (d 50 ) is usually 0.01 μm or more and 10 μm or less from the viewpoint of cycle life.

[0104] [2-2-1-4. Mixture of a material containing a metal element and / or a metalloid element capable of alloying with Li and natural graphite] (v) The mixture of the material containing a metal element and / or a metalloid element capable of alloying with Li and graphite particles may be a mixture in which the material containing a metal element and / or a metalloid element capable of alloying with Li and the graphite particles are mixed in a state of independent particles, or a composite in which the particles containing a metal element and / or a metalloid element capable of alloying with Li are present on the surface or inside of the graphite particles. The content ratio of the particles containing a metal element and / or a metalloid element capable of alloying with Li to the total of the particles containing a metal element and / or a metalloid element capable of alloying with Li and graphite particles is usually 1 mass% or more and 99 mass% or less.

[0105] [2-2-1-5. Lithium-containing metal composite oxide material] (iii) The lithium-containing metal composite oxide material is not particularly limited as long as it can occlude and release lithium ions. Specifically, from the viewpoint of high current density charge-discharge characteristics, a lithium-containing metal composite oxide material containing titanium is preferable, a composite oxide of lithium and titanium (hereinafter also referred to as "lithium titanium composite oxide") is more preferable, and a lithium titanium composite oxide having a spinel structure is even more preferable because it greatly reduces the output resistance. Furthermore, the lithium and / or titanium in the lithium-titanium composite oxide may be substituted with other metallic elements, such as at least one element selected from the group consisting of Al, Ga, Cu, and Zn. As a lithium titanium composite oxide, Li 4 / 3 Ti 5 / 3 O4, Li1Ti2O4 and Li 4 / 5 Ti 11 / 5 O4 is preferred. Also, lithium titanium composite oxides in which part of lithium and / or titanium is substituted with other elements are preferred, for example, Li 4 / 3 Ti 4 / 3 Al 1 / 3 O4 is also preferable.

[0106] [2-2-2. Negative electrode configuration and manufacturing method] The negative electrode may be manufactured using any known method, as long as it does not impair the effects of the present invention. For example, it can be manufactured by adding a binder, a liquid medium such as an aqueous solvent or an organic solvent, and optionally a thickener, a conductive material, a filler, etc., to the negative electrode active material to form a slurry, applying this slurry to a current collector, drying it, and then pressing it to form a negative electrode active material layer.

[0107] [2-2-2-1. Content of negative electrode active material] The content of the negative electrode active material in the negative electrode active material layer is typically between 80% by mass and 99.5% by mass.

[0108] [2-2-2-2. Electrode density] The negative electrode active material layer obtained by coating and drying is preferably compacted using a hand press, roller press, or the like to increase the packing density of the negative electrode active material. The electrode structure when the negative electrode active material is used as an electrode is not particularly limited, but the density of the negative electrode active material layer present on the current collector is usually 1 g / cm³. 3 More than 2.2g / cm 3 The following applies:

[0109] [2-2-2-3. Thickening agents] Thickening agents are typically used to adjust the viscosity of slurries. While not particularly limited, examples of thickening agents include carboxymethylcellulose and its salts, methylcellulose, hydroxymethylcellulose, ethylcellulose, and polyvinyl alcohol. These can be used individually or in combination of two or more in any ratio. When a thickening agent is used, the amount of the thickening agent relative to the negative electrode active material is usually between 0.1% by mass and 5% by mass.

[0110] [2-2-2-4. Binding agent] The binder used to bind the negative electrode active material can be any material that is stable with non-aqueous electrolytes or liquid media used during electrode manufacturing, and is not particularly limited. Specific examples include rubbery polymers such as styrene-butadiene rubber (SBR), isoprene rubber, butadiene rubber, fluororubber, acrylonitrile-butadiene rubber (NBR), and ethylene-propylene rubber, as well as fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and tetrafluoroethylene-ethylene copolymers. These can be used individually or in combination of two or more in any ratio. The binder content relative to the negative electrode active material is typically between 0.1% by mass and 20% by mass. In particular, when the binder contains a rubbery polymer such as SBR as its main component, the binder content relative to the negative electrode active material is usually between 0.1% by mass and 5% by mass. Furthermore, when the binder contains a fluorine-based polymer such as polyvinylidene fluoride as its main component, the binder content relative to the negative electrode active material is usually between 1% by mass and 15% by mass.

[0111] [2-2-2-5. Current Collector] Any known material can be used as the current collector for holding the negative electrode active material. Examples of negative electrode current collectors include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel, but copper is particularly preferred in terms of ease of processing and cost. Examples of the negative electrode current collector shape include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punched metal, and foamed metal. Among these, metal foil or metal thin film is preferred. The metal thin film may be formed in a mesh shape as appropriate. When the negative electrode current collector is plate-shaped or film-shaped, the thickness of the current collector can be arbitrary, but is usually between 1 μm and 1 mm.

[0112] [2-2-2-6. Thickness of the negative electrode plate] The thickness of the negative electrode (negative electrode plate) is designed to match the positive electrode (positive electrode plate) used and is not particularly limited; however, the thickness of the negative electrode active material layer, obtained by subtracting the thickness of the current collector from the thickness of the negative electrode material, is usually between 15 μm and 300 μm.

[0113] [2-2-2-7. Surface coating of the negative electrode plate] Furthermore, the negative electrode plate may also be one in which a substance with a different composition from the negative electrode active material is attached to its surface (surface-attached substance). Examples of surface-attached substances include oxides such as aluminum oxide, sulfates such as lithium sulfate, and carbonates such as lithium carbonate.

[0114] [2-3. Separator] A separator is usually placed between the positive and negative electrodes to prevent short circuits. In this case, the non-aqueous electrolyte is typically used by impregnating this separator. There are no particular restrictions on the material or shape of the separator; any known material or shape can be used as long as it does not impair the effects of the present invention.

[0115] [2-4.Battery design] [2-4-1. Electrode group] The electrode group may be either a laminated structure in which the positive electrode plate and the negative electrode plate are separated by the separator, or a structure in which the positive electrode plate and the negative electrode plate are spirally wound around the separator. The ratio of the volume of the electrode group to the internal volume of the battery (electrode group occupancy rate) is usually between 40% and 90%.

[0116] [2-4-2. Current collection structure] In the case of electrode groups with the aforementioned laminated structure, a structure formed by bundling the metal core portions of each electrode layer and welding them to a terminal is preferably used. A structure that reduces resistance by providing multiple terminals within the electrode is also preferably used. In the case of electrode groups with the aforementioned wound structure, the internal resistance can be reduced by providing multiple lead structures in both the positive and negative electrodes and bundling them to a terminal.

[0117] [2-4-3. Protective Elements] As protective elements, PTC (Positive Temperature Coefficient) elements whose resistance increases with heat generation due to excessive current, thermal fuses, thermistors, and valves (current interruption valves) that interrupt the current flowing through the circuit due to a rapid rise in internal pressure or temperature of the battery in the event of abnormal heat generation can be used. It is preferable to select the above protective elements that do not operate under normal high-current use, and it is even more preferable to design the system so that abnormal heat generation or thermal runaway does not occur even without protective elements.

[0118] [2-4-4. Exterior] Non-aqueous electrolyte batteries are typically constructed by housing the non-aqueous electrolyte, negative electrode, positive electrode, separator, etc., of the present invention within an outer casing (outer case). There are no restrictions on this outer casing; any known material can be used as long as it does not impair the effects of the present invention. The material of the outer casing can be any substance that is stable with respect to the non-aqueous electrolyte used, and is not particularly limited. However, from the viewpoint of weight reduction and cost, metals such as iron, aluminum, aluminum alloys, or laminated films are preferably used. Iron is particularly preferred due to its pressure resistance required to operate the current interruption valve. Outer cases using the above-mentioned metals include those that create a sealed structure by welding the metals together using laser welding, resistance welding, or ultrasonic welding, or those that create a crimped structure using the above-mentioned metals via a resin gasket.

[0119] [2-4-5. Shape] Furthermore, the shape of the outer case is arbitrary and can be any of the following: cylindrical, rectangular, laminated, coin-shaped, large, etc. [Examples]

[0120] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0121] The compounds used in this example are listed below. Compound (A): Vinyl ethylene sulfite

[0122] [ka]

[0123] LiPO2F2: Lithium difluorophosphate LiBOB: Lithium bis(oxalate) borate LiSO3F: Lithium fluorosulfonate ES: Ethylene sulfite DMS: Dimethyl sulfite VEC: Vinyl ethylene carbonate

[0124] <Examples 1-4, Comparative Examples 1-8> (Preparation of non-aqueous electrolyte) Under a dry argon atmosphere, a non-aqueous electrolyte was prepared by dissolving thoroughly dried LiPF6 in a mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio 3:4:3) to a concentration of 1.2 mol / L (14.3 mass%) in the non-aqueous electrolyte. Further, vinyl ethylene sulfite as compound (A) and a specific anion-containing compound were dissolved in the non-aqueous electrolyte in the amounts shown in Table 1. A non-aqueous electrolyte secondary battery was then prepared using this non-aqueous electrolyte by the method described below. Note that in Example 1, the specific anion-containing compound was not used; in Comparative Examples 1, 5, and 7, vinyl ethylene sulfite was not used; and in Comparative Examples 2-4, ES, DMS, or VEC were used instead of compound (A), respectively. (Fabrication of positive electrode 1) The positive electrode active material is lithium cobalt nickel manganese oxide (Li) which is compound (B).1.00 Ni 0.61 Co 0.20 Mn 0.19 90 parts by mass of O2 (Ni / M molar ratio = 0.61, carbonate concentration 91 μmol / g), 7 parts by mass of acetylene black as a conductive material, and 3 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed in N-methyl-2-pyrrolidone to form a slurry. This slurry was uniformly applied to a 15 μm thick aluminum foil, dried, and then roll-pressed to form positive electrode 1. The density of the positive electrode active material layer in positive electrode 1 was 3.3 g / cm³. 3 That was the case. (Fabrication of positive electrode 2) Positive electrode 2 was fabricated using the same method as positive electrode 1, with 97 parts by mass of lithium cobalt oxide (LiCoO2) (Ni / M molar ratio = 0, carbonate concentration 6 μmol / g) as the positive electrode active material, 1.5 parts by mass of acetylene black as the conductive material, and 1.5 parts by mass of polyvinylidene fluoride (PVdF) as the binder. The density of the positive electrode active material layer in positive electrode 2 was 3.6 g / cm³. 3 That was the case. (Fabrication of positive electrode 3) Lithium cobalt nickel manganese oxide (Li) is used as the positive electrode active material. 1.05 Ni 0.34 Mn 0.33 Co 0.33 Positive electrode 3 was prepared using the same method as positive electrode 1, with 85 parts by mass of O2 (Ni / M molar ratio = 0.34, carbonate concentration 12 μmol / g), 10 parts by mass of acetylene black as a conductive material, and 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder. The density of the positive electrode active material layer in positive electrode 2 was 2.6 g / cm³. 3 That was the case.

[0125] (Fabrication of the negative electrode) 49 parts by mass of graphite powder as the negative electrode active material, 50 parts by mass of aqueous dispersion of sodium carboxymethylcellulose (concentration of sodium carboxymethylcellulose 1% by mass) as a thickener, and 1 part by mass of aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber 50% by mass) as a binder were mixed in a disperser to form a slurry. The resulting slurry was uniformly applied to a 10 μm thick copper foil, dried, and roll-pressed to form the negative electrode.

[0126] (Manufacturing of non-aqueous electrolyte secondary batteries) The positive and negative electrodes and polyolefin separators prepared as described above were stacked in the order of negative electrode, separator, and positive electrode. The resulting battery elements were wrapped in an aluminum laminate film, injected with the aforementioned non-aqueous electrolyte, and then vacuum-sealed to produce a sheet-like non-aqueous electrolyte secondary battery. The positive electrode used was the one described in Table 1.

[0127] [Evaluation of non-aqueous electrolyte secondary batteries] The non-aqueous electrolyte secondary battery prepared as described above was evaluated as follows. (Initial charge / discharge) In a constant temperature bath at 25°C, a sheet-shaped non-aqueous electrolyte secondary battery was charged with a current equivalent to 0.05C up to 3.7V, then charged with constant current-constant voltage (hereinafter also referred to as "CC-CV charging") at 0.2C up to a voltage of 4.25V, and finally discharged with a constant current at 0.2C down to 2.5V. Furthermore, the non-aqueous electrolyte secondary battery was stabilized by CC-CV charging to 4.1V at 0.2C and then storing it at 60°C for 24 hours. Subsequently, at 25°C, it was discharged at a constant current of 0.2C to 2.5V, and then CC-CV charging was performed at 0.2C to a voltage of 4.25V. After that, a constant current discharge was performed at 0.2C to 2.5V, and the discharge capacity at this point was taken as the initial capacity. Subsequently, CC-CV charging was performed at 25°C with a current of 0.2C until the voltage reached 3.7V. Constant current discharge was then performed at 25°C at currents of 0.05C, 0.1C, 0.25C, 0.5C, 0.75C, and 1C, and the voltage after 10 seconds was measured. The internal resistance was determined from this current-voltage line and defined as the initial resistance (R1). Next, CC-CV charging was performed at 0.2C up to 4.25V to complete the initial charge and discharge. Here, 1C represents the current value required to discharge the battery's standard capacity in one hour. For example, 0.025C represents 1 / 40th of that current value. The same applies to subsequent values.

[0128] [Evaluation of gas generation amount and linear resistance (DCR) maintenance rate after high-temperature storage] The non-aqueous electrolyte secondary batteries described above, after initial charge and discharge, were stored at 85°C for 24 hours. During this process, the non-aqueous electrolyte secondary batteries before initial charge and discharge and after high-temperature storage were immersed in an ethanol bath at room temperature, and their volume was measured. The volume change was defined as the "amount of gas generated after high-temperature storage" of the battery. This non-aqueous electrolyte secondary battery was subjected to constant current discharge at 0.2C to 2.5V in a constant temperature bath at 25°C, followed by CC-CV charging at 0.2C to a voltage of 4.25V. After that, it was discharged again at 0.2C to 2.5V.

[0129] Subsequently, CC-CV charging was performed at 25°C at 0.2C until the voltage reached 3.7V. Furthermore, constant current discharge was performed at 25°C at 0.05C, 0.1C, 0.25C, 0.5C, 0.75C, and 1C, and the voltage at 10 seconds was measured. The internal resistance was determined from this current-voltage line and defined as the resistance after storage (R2), and the rate of change of R1 and R2 [R2 / R1 × 100] was defined as the "DCR maintenance rate after high-temperature storage". Furthermore, it is preferable that the amount of gas generated after high-temperature storage and the DCR maintenance rate after high-temperature storage are small.

[0130] Table 1 shows the DCR retention rate and gas generation amount after high-temperature storage for examples and comparative examples using any of positive electrodes 1 to 3 (relative values ​​for lithium batteries using each positive electrode, with lithium-ion batteries (Comparative Examples 1, 5, or 7) in which the non-aqueous electrolyte does not contain compound (A) and specific anion-containing compounds set to 100).

[0131] [Table 1]

[0132] As is clear from Table 1, the non-aqueous electrolyte secondary battery (Example 1), which comprises a non-aqueous electrolyte containing compound (A) and a positive electrode 1 having a positive electrode active material containing compound (B), suppressed the deterioration of the DCR maintenance rate after high-temperature storage and suppressed the increase in gas generation after high-temperature storage compared to the non-aqueous electrolyte secondary battery (Comparative Example 1), which comprises a non-aqueous electrolyte without compound (A) and a positive electrode 1, and the non-aqueous electrolyte secondary batteries (Comparative Examples 2-4), which comprises a non-aqueous electrolyte containing ES, DMS, and VEC used in the conventional technology instead of compound (A) and a positive electrode 1. Furthermore, it can be seen that the non-aqueous electrolyte secondary batteries (Examples 2-4), which comprise a non-aqueous electrolyte containing compound (A) and a specific amount of a specific anion-containing compound, and a positive electrode 1 having a positive electrode active material containing compound (B), suppress the deterioration of the DCR maintenance rate after high-temperature storage and suppress the increase in gas generation after high-temperature storage to an even higher level than the non-aqueous electrolyte secondary battery of Example 1. Furthermore, non-aqueous electrolyte secondary batteries (Comparative Examples 6 and 8) equipped with a non-aqueous electrolyte containing compound (A) and a positive electrode 2 or positive electrode 3 that does not contain compound (B) showed less improvement or worsening of the DCR maintenance rate after high-temperature storage and an increase in gas generation after high-temperature storage compared to non-aqueous electrolyte secondary batteries (Comparative Examples 5 and 7) equipped with a non-aqueous electrolyte not containing compound (A) and a positive electrode 2 or positive electrode 3 that does not contain compound (B). In other words, in batteries using a positive electrode 2 or positive electrode 3 that does not contain compound (B), when a non-aqueous electrolyte containing compound (A) was used, no improvement in the DCR maintenance rate after high-temperature storage was observed, and the amount of gas generated after high-temperature storage worsened rather than was suppressed. From this, it can be seen that, as shown in the examples, the effect of improving the DCR maintenance rate after high-temperature storage and suppressing the increase in gas generation after high-temperature storage is a unique effect of non-aqueous electrolyte secondary batteries equipped with a non-aqueous electrolyte containing compound (A) and a positive electrode containing compound (B). Furthermore, based on the results of the non-aqueous electrolyte secondary battery of Example 1 and the non-aqueous electrolyte secondary batteries of Comparative Examples 6 and 8, it is believed that the effects of the present invention were obtained by compound (A) acting on the Ni portion in the positive electrode active material of the positive electrode and forming a film, thereby suppressing side reactions between the positive electrode and components other than compound (A), such as the electrolyte of the non-aqueous electrolyte. [Industrial applicability]

[0133] The non-aqueous electrolyte battery of the present invention can improve the DC resistance (DCR) retention rate after high-temperature storage and suppress the increase in gas generation after high-temperature storage. Therefore, the non-aqueous electrolyte battery of the present invention can be suitably used in all fields, such as electronic devices, where non-aqueous electrolyte batteries have conventionally been used. Furthermore, the non-aqueous electrolyte battery of the present invention can be used in various known applications. Specific examples of applications include, for example, notebook computers, pen-input computers, mobile computers, e-book players, mobile phones, portable fax machines, portable copiers, portable printers, portable audio players, mini video cameras, headphone stereos, video camcorders, LCD televisions, handheld vacuum cleaners, portable CDs, MiniDiscs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, strobes, cameras, household backup power supplies, business backup power supplies, load leveling power supplies, and renewable energy storage power supplies.

Claims

1. A non-aqueous electrolyte for a non-aqueous electrolyte battery having a positive electrode containing a lithium transition metal compound (B) represented by the following compositional formula (2) as the positive electrode active material, Li a1 Ni b1 M c1 O 2 (2) (In compositional formula (2), a1, b1, and c1 are 0.90 ≤ a1 ≤ 1.10, 0.40 ≤ b1 ≤ 0.98, and 0.02 ≤ c1 ≤ 0.60, respectively, and b1 + c1 = 1. M represents at least one element selected from the group consisting of Co, Mn, Al, Mg, Zr, Fe, Ti, and Er.) The non-aqueous electrolyte is characterized in that the non-aqueous electrolyte contains compound (A) represented by formula (II). 【Chemistry 1】 (In formula (II), R １ and R ２ Each of these is independently selected from a hydrogen atom, a halogen atom, a vinyl group, and an allyl group, and either R1 or R2 is selected from a vinyl group and an allyl group.

2. Furthermore, the non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte contains in an amount of 0.001% by mass or more and 5% by mass or less one or more anion-containing compounds selected from the group consisting of phosphate anion-containing compounds having P-F bonds and P=O bonds, anion-containing compounds having S=O bonds, and oxalate complex anion-containing compounds.

3. The non-aqueous electrolyte according to claim 1 or 2, wherein the non-aqueous electrolyte contains 0.01% by mass or more and 10% by mass or less of the compound (A).

4. A non-aqueous electrolyte battery comprising a non-aqueous electrolyte, a positive electrode having a positive electrode active material capable of intercepting and releasing metal ions, and a negative electrode having a negative electrode active material capable of intercepting and releasing metal ions, The non-aqueous electrolyte is the non-aqueous electrolyte according to claim 1 or 2. A non-aqueous electrolyte battery characterized in that the positive electrode active material contains a lithium transition metal compound (B) represented by the following compositional formula (2). Li a1 Ni b1 M c1 O 2 (2) (In compositional formula (2), a1, b1, and c1 are 0.90 ≤ a1 ≤ 1.10, 0.40 ≤ b1 ≤ 0.98, and 0.02 ≤ c1 ≤ 0.60, respectively, and b1 + c1 = 1. M represents at least one element selected from the group consisting of Co, Mn, Al, Mg, Zr, Fe, Ti, and Er.)

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