Non-aqueous electrolyte solution, and non-aqueous electrolyte secondary battery

Abstract

To provide: a non-aqueous electrolyte solution with which a non-aqueous electrolyte secondary battery excellent in both durability and charging characteristics; and a non-aqueous electrolyte secondary battery including the non-aqueous electrolyte solution.SOLUTION: A non-aqueous electrolyte solution contains: a non-aqueous solvent: a compound represented by the formula (1) in the figure; and at least one heteroatom-containing lithium salt selected from the group consisting of (A) a lithium salt having an F-S bond, (B) a lithium salt having an oxalic acid skeleton, and (C) a lithium salt having P=O and P-F bonds, and the content of the heteroatom-containing lithium salt is from 0.001 mass% to 5 mass% inclusive. In the formula (1), R1 represents a hydrogen atom or a methyl group, and R2 represents a hydrogen atom, or a hydrocarbon group having 1 to 5 carbon atoms and optionally containing a halogen atom.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a non-aqueous electrolyte capable of providing a non-aqueous electrolyte secondary battery excellent in both durability and charging characteristics, and a non-aqueous electrolyte secondary battery.

Background Art

[0002] In recent years, non-aqueous electrolyte secondary batteries such as lithium secondary batteries have rapidly expanded in their applications and usage amounts. Regarding applications, they have been widely put into practical use from power sources for mobile phones and notebook computers to in-vehicle drive power sources for automobiles, etc. Among them, in recent years, demands regarding charging characteristics such as shortening of charging time by rapid charging have been increasing more and more. So far, various technologies have been proposed to improve the charging characteristics of non-aqueous electrolyte secondary batteries. For example, Patent Document 1 discloses a technology for improving high-current characteristics by using lithium titanium composite oxide particles having a specific average pore diameter as a negative electrode active material. Also, Patent Document 2 discloses a technology for improving rapid charging characteristics by disposing solid particles between the active material layer and the separator. Furthermore, Patent Document 3 discloses a technology capable of improving rapid charging characteristics by performing charging step by step.

[0003] On the other hand, as a basic required characteristic for non-aqueous electrolyte secondary batteries, there is durability represented by cycle characteristics, etc. So far, it has been proposed to use additives in the non-aqueous electrolyte to improve the durability of non-aqueous electrolyte secondary batteries. For example, Patent Document 4 discloses a technology capable of improving cycle characteristics by containing an unsaturated carboxylic acid ester in the non-aqueous electrolyte.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] Durability and charge characteristics are strongly required as battery characteristics of non-aqueous electrolyte secondary batteries. However, according to the verification by the present inventor, a problem has been found that the improvement of durability and the improvement of charge characteristics by additives in non-aqueous electrolytes are in an inverse relationship. Generally, the improvement of durability by additives is due to the specific action of the additives on the active material or the suppression of side reactions with the electrolyte by forming a surface film. However, these actions on the surface increase the resistance at the electrode interface, which in turn leads to a decrease in charge characteristics. However, in the above Patent Document 4, no specific evaluation or verification has been made regarding charge characteristics, and it has been found by the verification of the present inventor that the charge characteristics are not yet satisfactory. The present invention has been made in view of such a background, and an object thereof is to provide a non-aqueous electrolyte capable of providing a non-aqueous electrolyte secondary battery in which durability and charge characteristics, which are in an inverse relationship, are compatible and excellent, and a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte. [Means for Solving the Problems]

[0006] As a result of intensive studies to solve the above problems, the present inventor has found that in a non-aqueous electrolyte used in a non-aqueous electrolyte secondary battery, as the non-aqueous electrolyte, a fluorine-containing carboxylic acid ester compound having an acryloyl group or a methacryloyl group as a partial structure and a specific heteroatom-containing lithium salt can solve the above problems, and has completed Invention A. That is, the gist of Invention A is as follows. [A1]A non-aqueous electrolyte containing a non-aqueous solvent and at least one heteroatom-containing lithium salt selected from the group consisting of a compound represented by the following formula (1) and (A) a lithium salt having an F-S bond, (B) a lithium salt having an oxalic acid skeleton, and (C) a lithium salt having a P=O and P-F bonds, wherein the content of the heteroatom-containing lithium salt is 0.001% by mass or more and 5% by mass or less.

[0007] [Chemical formula]

[0008] (In the above formula (1), R 1 represents a hydrogen atom or a methyl group. R 2 represents a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 5 carbon atoms which may contain a halogen atom.) [A2]The non-aqueous electrolyte according to [A1], wherein the content of the compound represented by the formula (1) is 0.001% by mass or more and 20% by mass or less. [A3]The non-aqueous electrolyte according to [A1] or [A2], wherein the content of the heteroatom-containing lithium salt is 0.001% by mass or more and 3% by mass or less. [A4]The non-aqueous electrolyte according to any one of [A1] to [A3], further comprising at least one selected from the group consisting of LiPF6, LiBF4, LiClO4, and Li(CF3SO2)2N. [A5]The non-aqueous electrolyte according to any one of [A1] to [A4], further comprising a cyclic carbonate compound having a carbon-carbon unsaturated bond or a cyclic carbonate compound having a fluorine atom. [A6]A non-aqueous electrolyte secondary battery comprising a negative electrode capable of occluding and releasing metal ions, a positive electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is the non-aqueous electrolyte according to any one of [A1] to [A5].

[0009] As a result of intensive research to solve the above problems, the present inventors have found that the above problems can be solved by including a fluorine-containing carboxylate compound having an acryloyl group or a methacryloyl group as a partial structure and a specific nitrogen atom-containing compound in a nonaqueous electrolyte solution used in a nonaqueous electrolyte secondary battery, and have completed Invention B. That is, the gist of the present invention is as follows. [B1] A non-aqueous electrolyte solution containing a non-aqueous solvent and a lithium salt as an electrolyte, and containing at least one of a compound represented by formula (2) and a compound represented by formula (3) or an isocyanate compound.

[0010] [ka]

[0011] (In formula (2), R 11 R represents a hydrogen atom or a methyl group. 21 is the number of carbon atoms including fluorine atoms Represents 1 to 10 hydrocarbon groups.

[0012] [ka]

[0013] (In formula (3), R 31 ~R 51 may be the same or different, and may have a substituent. represents an organic group having 1 to 20 carbon atoms which may be substituted. [B2] The nonaqueous electrolyte solution according to [B1], wherein the content of the compound represented by formula (2) is from 0.001% by mass to 20% by mass. The non-aqueous electrolyte according to [B1] or [B2], wherein the content of the compound represented by the formula (3) and / or the isocyanate compound is 0.001% by mass or more and 20% by mass or less. A non-aqueous electrolyte secondary battery comprising a negative electrode capable of occluding and releasing metal ions, a positive electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is the non-aqueous electrolyte according to any one of [B1] to [B3].

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a non-aqueous electrolyte that enables a non-aqueous electrolyte secondary battery with excellent durability and charging characteristics, and a non-aqueous electrolyte secondary battery using the same.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, the present invention will be described in detail. The following description is an example (representative example) of the present invention, and the present invention is not limited thereto. Further, the present invention can be arbitrarily modified and implemented without departing from the gist thereof.

[0016] 〔Non-aqueous electrolyte A〕 The non-aqueous electrolyte according to one embodiment of the present invention A contains a non-aqueous solvent and a compound represented by the following formula (1) (hereinafter, may be referred to as compound (1)) and at least one heteroatom-containing lithium salt selected from the group consisting of (A) a lithium salt having an F-S bond, (B) a lithium salt having an oxalic acid skeleton, and (C) a lithium salt having a P=O and a P-F bond.

[0017]

Chemical formula

[0018] (In the above formula (1), R 1 represents a hydrogen atom or a methyl group. R 2 represents a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 5 carbon atoms which may contain a halogen atom.) The non-aqueous electrolyte of Invention A has the effect of achieving excellent durability and charge characteristics simultaneously. Although the reason why Invention A exhibits such an effect is not clear, it is presumed to be due to the following mechanism. The acryloyl group or methacryloyl group that the compound (1) has as a partial structure undergoes a polymerization reaction by the anion species generated near the negative electrode, and a base layer bonded with a carboxylic acid ester group containing a fluorine atom is formed on the negative electrode. After the formation of the base layer, a lithium salt having a specific skeleton containing a heteroatom ((A) a lithium salt having an F-S bond, (B) a lithium salt having an oxalic acid skeleton), (C) a lithium salt having P=O and P-F bonds) undergoes a reduction decomposition reaction on the negative electrode, and a film containing lithium atoms and heteroatoms is formed on the base layer. At this time, since a film containing lithium is formed on the base layer containing a carboxylic acid ester containing a fluorine atom, the fluorine in the base layer reacts with the lithium in the film, and a film containing a large amount of lithium fluoride is formed. A film containing a large amount of lithium fluoride is known to have high durability. In Invention A, it is considered that the durability is excellent because a film containing a large amount of lithium fluoride is formed. Furthermore, since the film contains a heteroatom derived from the lithium salt, it is considered that the mobility of lithium ions in the film increases and the charge characteristics are improved. That is, it is presumed that a compound having a fluorine atom and a polymerizable group forms a base layer, and a specific lithium salt containing a heteroatom forms a film thereon, so that the base layer and the film react to synergistically form a favorable film that achieves both durability and charge characteristics.

[0019] <Compound (1) represented by formula (1)> The non-aqueous electrolyte of Invention A contains the compound (1) represented by formula (1). In the above formula (1), R 1 is a hydrogen atom or a methyl group, and R 2 is a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 5 carbon atoms which may contain a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom. R 2Preferably, it is a hydrogen atom; a fluorine atom; a hydrocarbon group such as a methyl group, an ethyl group or a propyl group; or a fluorine atom-containing hydrocarbon group such as a trifluoromethyl group or a trifluoroethyl group, more preferably a hydrogen atom or a perfluoroalkyl group, and particularly preferably a hydrogen atom or a trifluoromethyl group.

[0020] Specific examples of the compound (1) include 2,2,2-trifluoroethyl acrylate, 2,2,2-trifluoroethyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate. Among them, 2,2,2-trifluoroethyl acrylate is preferred because of its optimal reaction potential. The compound (1) is characterized by being a fluorine-containing carboxylic acid ester compound having an acryloyl group or a methacryloyl group as a partial structure. The acryloyl group or the methacryloyl group is a partial structure necessary for forming an underlayer by a polymerization reaction on the negative electrode, and the fluorine atom is considered necessary for introducing a large amount of lithium fluoride into the film. In addition, it is also necessary that the reaction potential is suitable for a specific heteroatom-containing lithium salt. If the reaction potential is too high, it will cause the decomposition of the compound (1) itself, and if it is too low, a synergistic reaction with the specific heteroatom-containing lithium salt cannot be obtained. Among the fluorine-containing carboxylic acid ester compounds having an acryloyl group or a methacryloyl group as a partial structure, when the structure corresponds to the compound (1), the reaction potential is considered to be suitable for a specific heteroatom-containing lithium salt.

[0021] The content of the compound (1) in the non-aqueous electrolyte is not particularly limited as long as the effects of the present Invention A are not significantly impaired. Specifically, the lower limit of the content of the compound (1) in the non-aqueous electrolyte is preferably 0.001% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more with respect to the total amount of the non-aqueous electrolyte. Further, the upper limit is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less with respect to the total amount of the non-aqueous electrolyte. When the concentration of the compound (1) is within the above preferred range, the effects of improving durability and charging characteristics are more likely to be further manifested without impairing other battery performances. There are no particular restrictions on the method for identifying the compound (1) and measuring its content, and it can be appropriately selected from known methods and used. Examples of known methods include gas chromatography, nuclear magnetic resonance (NMR) spectroscopy, and the like. The compound (1) only needs to be contained in the non-aqueous electrolyte, and in addition to the case where it is added, it also includes those generated in the non-aqueous electrolyte or in the non-aqueous electrolyte battery during battery operation.

[0022] <A2. Specific Heteroatom-Containing Lithium Salts> The non-aqueous electrolyte of the present Invention A contains at least one heteroatom-containing lithium salt selected from the group consisting of (A) a lithium salt having an F-S bond, (B) a lithium salt having an oxalic acid skeleton, and (C) a lithium salt having a P=O and a P-F bond. Among them, (A) a lithium salt having an F-S bond or (B) a lithium salt having an oxalic acid skeleton is preferable, and (A) a lithium salt having an F-S bond is more preferable.

[0023] (A) A lithium salt having an F-S bond, (B) a lithium salt having an oxalic acid skeleton, and (C) a lithium salt having P=O and P-F bonds. The content of the heteroatom-containing lithium salt selected from the group consisting of in the non-aqueous electrolyte is not particularly limited as long as the effect of the present invention A is not significantly impaired. Specifically, the lower limit of the content of the heteroatom-containing lithium salt in the non-aqueous electrolyte is preferably 0.001% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, based on the total amount of the non-aqueous electrolyte. Further, the upper limit is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 3% by mass or less, and most preferably 2% by mass or less, based on the total amount of the non-aqueous electrolyte. When the concentration of the heteroatom-containing lithium salt is within the above preferred range, the effect of improving durability and charging characteristics is more likely to be exhibited without impairing other battery performances.

[0024] In addition, (A) a lithium salt having an F-S bond, (B) a lithium salt having an oxalic acid skeleton, and (C) a lithium salt having P=O and P-F bonds may be combined in two or more kinds. In particular, a combination of (A) a lithium salt having an F-S bond and (C) a lithium salt having P=O and P-F bonds is preferable. When the non-aqueous electrolyte contains two or more kinds of heteroatom-containing lithium salts, it is preferable that the total amount thereof satisfies the above range.

[0025] <A2-1. (A) Lithium salt having an F-S bond> The lithium salt having an F-S bond (which may be referred to as "heteroatom-containing lithium salt (A)") used in the present invention A is not particularly limited as long as it is a lithium salt having an F-S bond in the molecule, and any one can be used as long as the effect of the present invention A is not significantly impaired. Examples of the heteroatom-containing lithium salt (A) include Lithium fluorosulfonate (LiFSO3); Lithium fluorosulfonyl imide salts such as lithium bis(fluorosulfonyl)imide (LiN(FSO2)2), LiN(FSO2)(CF3SO2); Lithium fluorosulfonyl methide salts such as LiC(FSO2)3; Lithium fluorosulfonyl borates such as LiBF3(FSO3), LiB(FSO2)4; etc. are included, but are not particularly limited thereto. The heteroatom-containing lithium salt (A) can be used alone or in combination of two or more.

[0026] Among these, LiFSO3 or LiN(FSO2)2 is preferable, and particularly LiFSO3 is preferable. In the non-aqueous electrolyte of the present invention A, the heteroatom-containing lithium salt (A) is preferably used as an auxiliary electrolyte. That is, the lower limit value is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more based on the total amount of the non-aqueous electrolyte. Also, the upper limit value is preferably 20% by mass or less, more preferably 10% by mass or less, further preferably 5% by mass or less, particularly preferably 3% by mass or less, and especially preferably 2% by mass or less based on the total amount of the non-aqueous electrolyte. There are no particular restrictions on the method for identifying and measuring the content of the heteroatom-containing lithium salt (A), and it can be appropriately selected from known methods and used. Known methods include, for example, ion chromatography, nuclear magnetic resonance (NMR) spectroscopy, etc. When the concentration of the heteroatom-containing lithium salt (A) is within the above preferable range, the effect of improving durability and charging characteristics is more likely to be manifested without impairing other battery performances.

[0027] <A2-2. (B) Salt having an oxalic acid skeleton> As the salt having an oxalic acid skeleton (B) used in the present Invention A (which may be referred to as "heteroatom-containing lithium salt (B)"), there is no particular limitation as long as it is a salt having an oxalic acid skeleton in the molecule, and any salt can be used as long as the effects of the present invention are not significantly impaired. Examples of the heteroatom-containing lithium salt (B) include, but are not particularly limited to, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium tetrafluoro(oxalato)phosphate, and lithium difluorobis(oxalato)phosphate (LiDFOP). The heteroatom-containing lithium salt (B) can be used alone or in combination of two or more.

[0028] Among these, LiBOB, LiDFOB, and LiDFOP are more preferable, and LiBOB is particularly preferable. In the non-aqueous electrolyte of the present Invention A, the content of the heteroatom-containing lithium salt (B) is not particularly limited as long as the effects of the present Invention A are not significantly impaired, but the heteroatom-containing lithium salt (B) is preferably used as a secondary electrolyte. That is, the lower limit of the content of the heteroatom-containing lithium salt (B) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more based on the total amount of the non-aqueous electrolyte. Also, the upper limit is preferably 20% by mass or less, more preferably 10% by mass or less, further preferably 5% by mass or less, particularly preferably 3% by mass or less, and most preferably 2% by mass or less based on the total amount of the non-aqueous electrolyte. There is no particular limitation on the method for identifying and measuring the content of the heteroatom-containing lithium salt (B), and it can be appropriately selected from known methods and used. Examples of known methods include ion chromatography and nuclear magnetic resonance (NMR) spectroscopy. When the concentration of the heteroatom-containing lithium salt (B) is within the above preferable range, the effect of improving durability and charging characteristics is more likely to be manifested without impairing other battery performances.

[0029] <Lithium salts having A2-3.(C)P=O and P-F bonds> As the lithium salt having A2-3.(C)P=O and P-F bonds (which may be referred to as "heteroatom-containing lithium salt (C)") used in Invention A, there is no particular limitation as long as it is a lithium salt having P=O and P-F bonds in the molecule, and any one can be used as long as the effects of Invention A are not significantly impaired. Examples of the heteroatom-containing lithium salt (C) include, but are not particularly limited to, lithium difluorophosphate (LiPO2F2) and lithium fluorophosphate (Li2PO3F). The heteroatom-containing lithium salt (C) can be used alone or in combination of two or more. Among these, LiPO2F2 is particularly preferred.

[0030] In the non-aqueous electrolyte of Invention A, the content of the heteroatom-containing lithium salt (C) is not particularly limited as long as the effects of the present invention are not significantly impaired, but the heteroatom-containing lithium salt (C) is preferably used as an auxiliary electrolyte. That is, the lower limit of the salt content of the heteroatom-containing lithium salt (C) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more based on the total amount of the non-aqueous electrolyte. The upper limit is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 3% by mass or less, and most preferably 2% by mass or less based on the total amount of the non-aqueous electrolyte. The method for identifying and measuring the content of the heteroatom-containing lithium salt (C) is not particularly limited, and can be appropriately selected from known methods and used. Known methods include, for example, ion chromatography, nuclear magnetic resonance (NMR) spectroscopy, and the like. When the concentration of the heteroatom-containing lithium salt (C) is within the above preferred range, the effect of improving durability and charging characteristics is more likely to be manifested without impairing other battery performances.

[0031] <A3. Non-aqueous solvent> The non-aqueous electrolyte of Invention A, like a general non-aqueous electrolyte, usually contains, as its main component, a non-aqueous solvent that dissolves the electrolyte described later. There are no particular restrictions on the non-aqueous solvent, and known organic solvents can be used. The organic solvent is not particularly limited, but preferably, at least one selected from saturated cyclic carbonates, chain carbonates, chain carboxylic acid esters, cyclic carboxylic acid esters, ether compounds, and sulfone compounds is mentioned. These non-aqueous solvents can be used alone or in combination of two or more.

[0032] <A3-1. Saturated cyclic carbonate> Examples of the saturated cyclic carbonate usually include those having an alkylene group with 2 to 4 carbon atoms. Examples of the saturated cyclic carbonate with 2 to 4 carbon atoms include ethylene carbonate, propylene carbonate, butylene carbonate, etc. Among them, ethylene carbonate or propylene carbonate is preferable from the viewpoint of improving battery characteristics due to the improvement of lithium ion dissociation degree. The saturated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.

[0033] The content of the saturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of Invention A are not significantly impaired. However, in 100% by volume of the non-aqueous solvent, it is usually 3% by volume or more, preferably 5% by volume or more. By setting it within this range, it is possible to avoid a decrease in electrical conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte, and it becomes easier to keep the high-current discharge characteristics, stability against the negative electrode, and cycle characteristics of the non-aqueous electrolyte secondary battery within a good range. The upper limit is usually 90% by volume or less, preferably 85% by volume or less, more preferably 80% by volume or less in 100% by volume of the non-aqueous solvent. By setting it within this range, the viscosity of the non-aqueous electrolyte can be set within an appropriate range, the decrease in ionic conductivity can be suppressed, and thus the input / output characteristics of the non-aqueous electrolyte secondary battery can be further improved, or the durability such as cycle characteristics and storage characteristics can be further improved, which is preferable.

[0034] <A3-2. Chain carbonate> As the chain carbonate, those having 3 to 7 carbon atoms are preferred. Specific examples of the chain carbonate having 3 to 7 carbon atoms include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate, and the like. Among these, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl-n-propyl carbonate are preferred, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferred.

[0035] In addition, chain carbonates having a fluorine atom (hereinafter, may be abbreviated as "fluorinated chain carbonate") can also be preferably used. The number of fluorine atoms in the fluorinated chain carbonate is not particularly limited, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, the fluorine atoms may be bonded to the same carbon or different carbons. Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, fluorinated diethyl carbonate derivatives, and the like.

[0036] The chain carbonate may be used alone or in combination of two or more in any combination and ratio. The content of the chain carbonate is not particularly limited, but it is usually 15% by volume or more, preferably 20% by volume or more, more preferably 25% by volume or more in 100% by volume of the non-aqueous solvent. Also, it is usually 90% by volume or less, preferably 85% by volume or less, more preferably 80% by volume or less in 100% by volume of the non-aqueous solvent. By setting the content of the chain carbonate within the above range, the viscosity of the non-aqueous electrolyte can be set within an appropriate range, the decrease in ionic conductivity can be suppressed, and the decrease in electrical conductivity due to the decrease in the dielectric constant of the non-aqueous electrolyte can be avoided. As a result, it becomes easier to make the input / output characteristics and charge / discharge rate characteristics of the non-aqueous electrolyte secondary battery fall within a good range.

[0037] <A3-3. Chain carboxylic acid ester> Examples of the chain carboxylic acid ester include those having 3 to 7 carbon atoms in total in its structural formula. Specifically, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, t-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, n-propyl isobutyrate, isopropyl isobutyrate, etc. can be mentioned. Among these, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. are preferable from the viewpoints of improving ionic conductivity due to viscosity reduction and suppressing battery swelling during durability tests such as cycling and storage. The content of the chain carboxylic acid ester is not particularly limited, but it is usually 3% by volume or more, preferably 5% by volume or more, more preferably 10% by volume or more in 100% by volume of the non-aqueous solvent, and usually 30% by volume or less, preferably 20% by volume or less, more preferably 15% by volume or less. By setting the content of the chain carboxylic acid ester within the above range, the viscosity of the non-aqueous electrolyte can be set within an appropriate range, the decrease in ionic conductivity can be suppressed, and thus the output characteristics of the non-aqueous electrolyte secondary battery can be easily set within a good range.

[0038] <A3-4. Cyclic carboxylic acid ester> Examples of the cyclic carboxylic acid ester include those having 3 to 12 carbon atoms in total in its structural formula. Specifically, gamma-butyrolactone, gamma-valerolactone, gamma-caprolactone, epsilon-caprolactone, etc. can be mentioned. Among these, gamma-butyrolactone is particularly preferable from the viewpoint of improving battery characteristics due to the improvement of lithium ion dissociation degree. The content of the cyclic carboxylic acid ester is not particularly limited, but it is usually 3% by volume or more, preferably 5% by volume or more, more preferably 10% by volume or more in 100% by volume of the non-aqueous solvent and usually 30% by volume or less, preferably 20% by volume or less, more preferably 15% by volume or less. By setting the content of the cyclic carboxylic acid ester within the above range, the viscosity of the non-aqueous electrolyte can be set within an appropriate range, the decrease in ionic conductivity can be suppressed, and thus the output characteristics of the non-aqueous electrolyte secondary battery can be easily set within a good range.

[0039] <A3-5. Ether compounds> As the ether compound, a linear ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms are preferable. As chain ethers having 3 to 10 carbon atoms, there are diethyl ether, di(2-fluoroethyl) ether, di(2,2-difluoroethyl) ether, di(2,2,2-trifluoroethyl) ether, ethyl(2-fluoroethyl) ether, ethyl(2,2,2-trifluoroethyl) ether, ethyl(1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl)(2,2,2-trifluoroethyl) ether, (2-fluoroethyl)(1,1,2,2-tetrafluoroethyl) ether, (2,2,2-trifluoroethyl)(1,1,2,2-tetrafluoroethyl) ether, ethyl-n-propyl ether, ethyl(3-fluoro-n-propyl) ether, ethyl(3,3,3-trifluoro-n-propyl) ether, ethyl(2,2,3,3-tetrafluoro-n-propyl) ether, ethyl(2,2,3,3,3-pentafluoro-n-propyl) ether, 2-fluoroethyl-n-propyl ether, (2-fluoroethyl)(3-fluoro-n-propyl) ether, (2-fluoroethyl)(3,3,3-trifluoro-n-propyl) ether, (2-fluoroethyl)(2,2,3,3-tetrafluoro-n-propyl) ether, (2-fluoroethyl)(2,2,3,3,3-pentafluoro-n-propyl) ether, 2,2,2-trifluoroethyl-n-propyl ether, (2,2,2-trifluoroethyl)(3-fluoro-n-propyl) ether, (2,2,2-trifluoroethyl)(3,3,3-trifluoro-n-propyl) ether, (2,2,2-trifluoroethyl)(2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,2-trifluoroethyl)(2,2,3,3,3-pentafluoro-n-propyl) ether, 1,1,2,2-tetrafluoroethyl-n-propyl ether, (1,1,2,2-tetrafluoroethyl)(3-fluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl)(3,3,3-trifluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl)(2,2,3,3-tetrafluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl)(2,2,3,3,3-Pentafluoro-n-propyl) ether, di-n-propyl ether, (n-propyl)(3-fluoro-n-propyl) ether, (n-propyl)(3,3,3-trifluoro-n-propyl) ether, (n-propyl)(2,2,3,3-tetrafluoro-n-propyl) ether, (n-propyl)(2,2,3,3,3-pentafluoro-n-propyl) ether, di(3-fluoro-n-propyl) ether, (3-fluoro-n-propyl)(3,3,3-trifluoro-n-propyl) ether, (3-fluoro-n-propyl)(2,2,3,3-tetrafluoro-n-propyl) ether, (3-fluoro-n-propyl)(2,2,3,3,3-pentafluoro-n-propyl) ether, di(3,3,3-trifluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl)(2,2,3,3-tetrafluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl)(2,2,3,3,3-pentafluoro-n-propyl) ether, di(2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,3,3-tetrafluoro-n-propyl)(2,2,3,3,3-pentafluoro-n-propyl) ether, di(2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, methoxy(2-fluoroethoxy)methane, methoxy(2,2,2-trifluoroethoxy)methane methoxy(1,1,2,2-tetrafluoroethoxy)methane, diethoxymethane, ethoxy(2-fluoroethoxy)methane, eth, Kishi(2,2,2-trifluoroethoxy)methane, ethoxy(1,1,2,2-tetrafluoroethoxy)methane, di(2-fluoroethoxy)methane, (2-fluoroethoxy)(2,2,2-trifluoroethoxy)methane, (2-fluoroethoxy)(1,1,2,2-tetrafluoroethoxy)methane di(2,2,2-trifluoroethoxy)methane, (2,2,2-trifluoroethoxy)(1,1,2,2-tetrafluoroethoxy)methane, di(1,1,2,2-tetrafluoroethoxy)methane, dimethoxyethane, methoxyethoxyethane, methoxy(2-fluoroethoxy)ethane, methoxy(2,2,2-trifluoroethoxy)ethane, methoxy(1,1,2,2-tetrafluoroethoxy)ethane, diethoxyethane, ethoxy(2-fluoroethoxy)ethane, ethoxy(2,2,2-trifluoroethoxy)ethane, ethoxy(1,1,2,2-tetrafluoroethoxy)ethane, di(2-fluoroethoxy)ethane, (2-fluoroethoxy)(2,2,2-trifluoroethoxy)ethane, (2-fluoroethoxy)(1,1,2,2-tetrafluoroethoxy)ethane, di(2,2,2-trifluoroethoxy)ethane, (2,2,2-trifluoroethoxy)(1,1,2,2-tetrafluoroethoxy)ethane, di(1,1,2,2-tetrafluoroethoxy)ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, etc. are mentioned.

[0040] Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, etc., and fluorinated compounds thereof.

[0041] Among these, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether are preferable in that they have a high solvating ability for lithium ions and improve lithium ion dissociation. Particularly preferred are dimethoxymethane, diethoxymethane, and ethoxymethoxymethane because of their low viscosity and high ionic conductivity. The content of the ether-based compound is not particularly limited, but in 100% by volume of the non-aqueous solvent, it 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, more preferably 20% by volume or less. If the content of the ether-based compound is within the above preferred range, it is easy to ensure the effect of improving the lithium ion dissociation degree of the ether and the ionic conductivity resulting from the viscosity reduction. Further, when the negative electrode active material is a carbonaceous material, the phenomenon of co-insertion of the chain ether with lithium ions can be suppressed, so that the input / output characteristics and charge / discharge rate characteristics can be within an appropriate range.

[0042] <A3-6. Sulfone Compounds> The sulfone compound is not particularly limited and may be a cyclic sulfone or a chain sulfone, but a cyclic sulfone having 3 to 6 carbon atoms or a chain sulfone having 2 to 6 carbon atoms is preferable. The number of sulfonyl groups in one molecule of the sulfone compound is preferably 1 or 2. Examples of the cyclic sulfone include monosulfone compounds such as trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones; disulfone compounds such as trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones; and the like. Among these, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable from the viewpoints of dielectric constant and viscosity, and tetramethylene sulfones (sulfolanes) are particularly preferable.

[0043] As the sulfolanes, sulfolane and sulfolane derivatives are preferable. The sulfolane derivative As the compound, those 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 are preferable. Among these, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2,4-difluorosulfolane, 2,5-difluorosulfolane, 3,4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methylsulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoromethylsulfolane, 2-trifluoromethylsulfolane, 3-trifluoromethylsulfolane, 2-fluoro-3-(trifluoromethyl)sulfolane, 3-fluoro-3-(trifluoromethyl)sulfolane, 4-fluoro-3-(trifluoromethyl)sulfolane, 5-fluoro-3-(trifluoromethyl)sulfolane, etc. are preferable in terms of high ionic conductivity and high input / output.

[0044] In addition, examples of the chain sulfone include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n-butyl methyl sulfone, n-butyl ethyl sulfone, t-butyl methyl sulfone, t-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, perfluoroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, di(trifluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl-n-propyl sulfone, difluoromethyl-n-propyl sulfone, trifluoromethyl-n-propyl sulfone, fluoromethyl isopropyl sulfone, difluoromethyl isopropyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl-n-propyl sulfone, trifluoroethyl isopropyl sulfone, pentafluoroethyl-n-propyl sulfone, pentafluoroethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, pentafluoroethyl-n-butyl sulfone, pentafluoroethyl-t-butyl sulfone, and the like.

[0045] Among these, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, t-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, trifluoromethyl-n-propyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, trifluoromethyl-n-butyl sulfone, trifluoromethyl-t-butyl sulfone, etc. are preferable in terms of high ionic conductivity and high input / output. The content of the sulfone-based compound is not particularly limited, but in 100% by volume of the non-aqueous solvent, it is usually 0.3% by volume or more, preferably 0.5% by volume or more, more preferably 1% by volume or more, and usually 40% by volume or less, preferably 35% by volume or less, more preferably 30% by volume or less. If the content of the sulfone-based compound is within the above range, an electrolyte solution with excellent high-temperature storage stability tends to be obtained.

[0046] <A4. Electrolyte> <A4-1. Lithium salts other than specific heteroatom-containing lithium salts> The non-aqueous electrolyte of the present invention A can contain, as an electrolyte, one or more lithium salts other than the specific heteroatom-containing lithium salts (hereinafter, also referred to as "other lithium salts"). The other lithium salts are not particularly limited as long as they are used for this kind of application, and can be used as the main electrolyte or as a secondary electrolyte, but it is preferable to use them as the main electrolyte. Specific examples of the other lithium salts include the following. The other lithium salts can be used alone or in combination of two or more.

[0047] Other lithium salts that can be used in the non-aqueous electrolyte of Invention A include, for example, LiClO4, LiBF4, LiPF6, LiAsF6, LiTaF6, LiCF3SO3, LiC4F9SO3, Li(CF3SO2)2N, Li(C2F5SO2)2N, Li(CF3SO2)3C, LiBF3(C2F5), LiB(C6F5)4, LiPF3(C2F5)3 and the like. Among these, preferred are at least one selected from LiPF6, LiBF4, LiClO4, and Li(CF3SO2)2N; more preferred are at least one selected from LiPF6, LiBF4, and Li(CF3SO2)2N; and particularly preferred is LiPF6. The lithium salts listed above may be used alone or in combination of two or more.

[0048] When using other lithium salts as the main salt, the concentration (content) of the other lithium salts is arbitrary as long as the effects of Invention A are not significantly impaired. However, in the non-aqueous electrolyte, it is preferably 0.5 mol / L or more, more preferably 0.6 mol / L or more, still more preferably 0.7 mol / L or more. On the other hand, it is preferably 3 mol / L or less, more preferably 2 mol / L or less, still more preferably 1.8 mol / L or less. The content (% by mass) of the other lithium salts is preferably 6% by mass or more, more preferably 7% by mass or more, still more preferably 8% by mass or more, based on the total amount of the non-aqueous electrolyte. On the other hand, it is preferably 30% by mass or less, more preferably 22% by mass or less, still more preferably 20% by mass or less. By the content of the other lithium salts being within the above range, the ionic conductivity can be appropriately increased.

[0049] When using other lithium salts as secondary salts, the content of the other lithium salts is arbitrary as long as the effects of Invention A are not significantly impaired, but it is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more based on the total amount of the non-aqueous electrolyte. Also, as the upper limit, it is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 3% by mass or less, and especially preferably 2% by mass or less based on the total amount of the non-aqueous electrolyte.

[0050] The concentration of electrolytes such as all the above-mentioned lithium salts in the final composition of the non-aqueous electrolyte of Invention A is arbitrary as long as the effects of Invention A are not significantly impaired, but it is preferably 0.5 mol / L or more, more preferably 0.6 mol / L or more, and even more preferably 0.7 mol / L or more. On the other hand, it is preferably 3 mol / L or less, more preferably 2 mol / L or less, and even more preferably 1.8 mol / L or less. In terms of weight%, based on the total amount of the non-aqueous electrolyte, it is preferably 6% by mass or more, more preferably 7% by mass or more, and even more preferably 8% by mass or more. On the other hand, it is preferably 30% by mass or less, more preferably 22% by mass or less, and even more preferably 20% by mass or less. By the lithium salt content being within the above range, the ionic conductivity can be appropriately increased.

[0051] In addition, the identification and measurement of the content of the other lithium salts listed above are performed by ion chromatography. When at least one selected from LiPF6, LiBF4, LiClO4, and Li(CF3SO2)2N is contained as a main electrolyte in the non-aqueous electrolyte of the present invention as another lithium salt, the ratio of the mass of the content in the non-aqueous electrolyte of the heteroatom-containing lithium salt selected from the group consisting of (A) lithium salt having an F-S bond, (B) lithium salt having an oxalic acid skeleton, and (C) lithium salt having P=O and P-F bonds to the other lithium salt (heteroatom-containing lithium salt (mass%) / other lithium salt (mass%)) is not particularly limited as long as the effects of the present invention are not significantly impaired, but is preferably 0.002 or more, more preferably 0.02 or more, and particularly preferably 0.04 or more. Further, as the upper limit value, it is preferably 0.8 or less, more preferably 0.5 or less, and particularly preferably 0.2 or less. When the mass ratio of the above compounds is within the above preferred range, the effect of improving durability and charging characteristics is more likely to be exhibited without impairing other battery performances.

[0052] <A5. Additive> In addition to the various compounds listed above, the non-aqueous electrolyte of Invention A may contain various additives as long as the effects of Invention A are not significantly impaired. Examples of the additives include compounds having a cyano group such as malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azela nitrile, sebaconitrile, undecanedinitrile, dodecanedinitrile; isocyanato compounds such as 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1,2-bis(isocyanatomethyl)benzene, 1,3-bis(isocyanatomethyl)benzene, 1,4-bis(isocyanatomethyl)benzene; carboxylic anhydride compounds such as acrylic anhydride, 2-methylacrylic anhydride, 3-methylacrylic anhydride, benzoic anhydride, 2-methylbenzoic anhydride, 4-methylbenzoic anhydride, 4-tert-butylbenzoic anhydride, 4-fluorobenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, methoxyformic anhydride, ethoxyformic anhydride, succinic anhydride, maleic anhydride; thioether compounds such as trimethyl[2-(phenylthio)ethoxy]silane, trimethyl[1-fluoro-2-(phenylthio)ethoxy]silane, trimethyl[2-fluoro-2-(phenylthio)ethoxy]silane; cyclic carbonates having an unsaturated bond such as vinylene carbonate, vinyl ethylene carbonate; carbonates having a fluorine atom such as fluoroethylene carbonate; sulfonic acid ester compounds such as 1,3-propane sultone; etc. Further, examples of the overcharge inhibitor include cyclohexylbenzene, t-butylbenzene, t-amylbenzene, biphenyl, alkyl biphenyl, terphenyl, a partially hydrogenated product of terphenyl, diphenyl ether, dibenzofuran, etc. These compounds may be used in appropriate combinations. Among these, from the viewpoint of the capacity retention rate, vinylene carbonate or fluoroethylene carbonate is particularly preferable, and it is more preferable to use them in combination.

[0053] Hereinafter, a non-aqueous electrolyte according to an embodiment of Invention B will be described in detail. The following description is an example (representative example) of Invention B, and Invention B is not limited thereto. Further, Invention B can be arbitrarily modified and implemented without departing from the scope of its gist. [Non-aqueous electrolyte B] The non-aqueous electrolyte according to an embodiment of Invention B contains a non-aqueous solvent and a lithium salt as an electrolyte, and a compound represented by formula (2) (hereinafter sometimes referred to as compound (2)) and a compound represented by formula (3) (hereinafter sometimes referred to as compound (3)) or an isocyanato compound (hereinafter sometimes referred to as compound (4)), and contains at least one of them.

[0054] [Chemical formula]

[0055] (In the above formula (2), R 11 represents a hydrogen atom or a methyl group. R 21 represents a hydrocarbon group having 1 to 10 carbon atoms containing a fluorine atom.)

[0056] [Chemical formula]

[0057] (In the above formula (3), R 31 ~R 51 may be the same as or different from each other, and represents an organic group having 1 to 20 carbon atoms which may have a substituent .) The non-aqueous electrolyte of Invention B has the effect of achieving excellent durability and charging characteristics simultaneously. The reason why Invention B exhibits such an effect is not clear, but it is presumed to be due to the following mechanism. The acryloyl group or methacryloyl group that the compound (2) has as a partial structure undergoes a polymerization reaction by anion species generated near the negative electrode, and a base layer bonded with a carboxylic acid ester group containing a fluorine atom is formed on the negative electrode. After the formation of the base layer, a specific nitrogen atom-containing compound (compound (3) or compound (4)) and a lithium salt contained in the system as an electrolyte react to form a film containing lithium atoms and nitrogen atoms on the base layer. At this time, since a film containing lithium is formed on the base layer containing a carboxylic acid ester containing a fluorine atom, fluorine in the base layer and lithium in the film react to form a film containing a large amount of lithium fluoride. A film containing a large amount of lithium fluoride is known to have high durability, and for this reason, it is considered to be excellent in durability. Furthermore, by including nitrogen atoms derived from the nitrogen atom-containing compound in the film, the mobility of lithium ions in the film is increased, and it is considered that the charging characteristics are improved. That is, it is presumed that a compound having a fluorine atom and a polymerizable group forms a base layer, and a specific compound containing a nitrogen atom and a lithium salt of an electrolyte form a film thereon, and the base layer and the film react to synergistically form a favorable film that achieves both durability and charging characteristics.

[0058] <B1. Compound (2) represented by formula (2)> The non-aqueous electrolyte of Invention B contains the compound (2) represented by formula (2). In formula (2), R 11 is a hydrogen atom or a methyl group, and R 21 is a hydrocarbon group having 1 to 10 carbon atoms containing a fluorine atom. R 21 is preferably a hydrocarbon group having 1 to 5 carbon atoms containing a fluorine atom, more preferably a hydrocarbon group having 2 carbon atoms containing a fluorine atom such as a trifluoroethyl group, a hydrocarbon group having 3 carbon atoms containing a fluorine atom such as a hexafluoroisopropyl group, or a hexafluoro orobutyl or the like, which is a hydrocarbon group having 4 carbon atoms containing a fluorine atom, and particularly preferably a trifluoroethyl group or a hexafluoroisopropyl group.

[0059] Specifically, they are 2,2,2-trifluoroethyl acrylate, 2,2,2-trifluoroethyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate. Among them, 2,2,2-trifluoroethyl acrylate or 2,2,2-trifluoroethyl methacrylate is preferred because of the optimal reaction potential.

[0060] The content of the compound (2) in the non-aqueous electrolyte is not particularly limited as long as the effects of the present invention B are not significantly impaired. Specifically, the lower limit of the content of the compound (2) in the non-aqueous electrolyte is preferably 0.001% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more. The upper limit is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 2% by mass or less. When the concentration of the compound (2) is within the above preferred range, the effects of improving durability and charging characteristics are more likely to be further manifested without impairing other battery performances. The method for identifying the compound (2) and measuring its content is not particularly limited, and it can be appropriately selected from known methods and used. Examples of known methods include nuclear magnetic resonance (NMR) spectroscopy, gas chromatography, etc.

[0061] <B2. Specific nitrogen-containing compound> The non-aqueous electrolyte of the present invention B contains at least one of the compound represented by the formula (3) or the isocyanate compound. <B2-1. Compound (3) represented by the formula (3)> The compound (3) is the compound represented by the following formula (3).

[0062] [Chemical formula]

[0063] In the formula (3), R 31~R 51 may be the same as or different from each other and is an organic group having 1 to 20 carbon atoms which may have a substituent. Here, the organic group refers to a functional group composed of atoms selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, and a halogen atom. Specific examples include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, a nitrile group, an ether group, a carbonate group, a carbonyl group, etc. R As 31 ~R 51 ~R , preferably, a vinyl group, an allyl group, an ethynyl group, a propargyl group, an acrylic group via an alkyl group, a methacrylic group via an alkyl group, a vinylsulfonyl group via an alkyl group, a fluorine-substituted vinyl group, a fluorine-substituted allyl group, etc., which are groups having a carbon-carbon unsaturated bond. Particularly preferably, a vinyl group which may be fluorine-substituted, an allyl group which may be fluorine-substituted, an acrylic group via an alkyl group, a methacrylic group via an alkyl group, a vinylsulfonyl group via an alkyl group. More preferably, it is an allyl group. From the viewpoint of symmetry, R 31 ~R 51 are preferably the same.

[0064] There is no limitation on the content of the compound (3) in the non-aqueous electrolyte of the present invention B, and it is arbitrary as long as the effects of the present invention B are not significantly impaired. However, with respect to the total amount of the non-aqueous electrolyte, it 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, further preferably 2% by mass or less, particularly preferably 1% by mass or less. There is no particular limitation on the method for identifying and measuring the content of the compound (3), and it can be appropriately selected from known methods and used. Examples of known methods include nuclear magnetic resonance (NMR) spectroscopy, gas chromatography, etc. When the concentration of the compound (3) is within the above preferable range, the effect of improving durability and charging characteristics is more likely to be exhibited without impairing other battery performances.

[0065] ​<B2-2. Compound (4)> The isocyanate compound (compound (4)) is not particularly limited as long as it is a compound having an isocyanate group in the molecule. Specific examples of the compound (4) include aliphatic hydrocarbon monoisocyanate compounds such as methyl isocyanate, ethyl isocyanate, cyclohexyl isocyanate, vinyl isocyanate, or allyl isocyanate; Aliphatic hydrocarbon diisocyanate compounds such as chain aliphatic hydrocarbon diisocyanates such as butyl diisocyanate or hexamethylene diisocyanate, or alicyclic hydrocarbon diisocyanates such as 1,3-bis(isocyanatomethyl)cyclohexane or dicyclohexylmethane 4,4'-diisocyanate; Aromatic hydrocarbon monoisocyanate compounds such as aromatic monoisocyanates such as phenyl isocyanate, (ortho-, meta-, para-)toluene isocyanate, or aromatic monosulfonyl isocyanates such as (ortho-, meta-, para-)toluenesulfonyl isocyanate; Aromatic hydrocarbon diisocyanate compounds such as m-xylylene diisocyanate, tolylene-2,4-diisocyanate, or diphenylmethane diisocyanate; and the like.

[0066] Preferably, aliphatic hydrocarbon diisocyanate compounds such as chain aliphatic hydrocarbon diisocyanates or alicyclic hydrocarbon diisocyanates; Aromatic hydrocarbon monoisocyanate compounds such as aromatic monoisocyanates or aromatic monosulfonyl isocyanates; It is an aromatic hydrocarbon diisocyanate compound, More preferably, chain aliphatic hydrocarbon-based diisocyanates such as hexamethylene diisocyanate and alicyclic hydrocarbon-based isocyanate compounds such as 1,3-bis(isocyanatomethyl)cyclohexane, Particularly preferably, hexamethylene diisocyanate and 1,3-bis(isocyanatomethyl)cyclohexane.

[0067] There is no restriction on the content of the isocyanate compound in the non-aqueous electrolyte of Invention B, and it is arbitrary as long as the effects of Invention B are not significantly impaired. However, with respect to the total amount of the non-aqueous electrolyte, it 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, still more preferably 2% by mass or less, and particularly preferably 1% by mass or less. There is no particular limitation on the method for identifying and measuring the content of the isocyanate compound, and it can be appropriately selected from known methods and used. Examples of known methods include nuclear magnetic resonance (NMR) spectroscopy, gas chromatography, and the like. In addition, the compound selected from the group consisting of the compound represented by the formula (3) and the isocyanate compound may be used alone or in combination of two or more in any combination and ratio.

[0068] <B3. Non-aqueous solvent> The non-aqueous electrolyte of Invention B, like a general non-aqueous electrolyte, usually contains a non-aqueous solvent that dissolves an electrolyte described later as its main component. There is no particular limitation on the non-aqueous solvent, and known organic solvents can be used. The organic solvent can be the same as in Invention A. That is, the organic solvent is not particularly limited, but preferably at least one selected from saturated cyclic carbonates, chain carbonates, chain carboxylic acid esters, cyclic carboxylic acid esters, ether compounds, and sulfone compounds. Specific examples thereof include those exemplified in Invention A, and the preferred embodiments are also the same as in Invention A. The non-aqueous solvent can be used alone or in combination of two or more.

[0069] <B4. Electrolyte> The non-aqueous electrolyte according to Invention B usually contains a lithium salt as an electrolyte. Examples of the lithium salt used in Invention B include LiClO4, LiBF4, LiPF6, LiAsF6, LiTaF6, LiCF3SO3, LiC4F9SO3, Li(FSO2)2N, Li(CF3SO2)2N, Li(C2F5SO2)2N, Li(CF3SO2)3C, LiBF3(C2F5), LiB(C2O4)2, LiB(C6F5)4, LiPF3(C2F5)3, etc. Among these, preferred ones are LiPF6, LiBF4, LiClO4, LiB(C2O4)2, Li(FSO2)2N or Li(CF3SO2)2N, more preferred ones are LiPF6, LiBF4, Li(FSO2)2N or Li(CF3SO2)2N, still more preferred is at least one of LiPF6 and Li(FSO2)2N, and particularly preferred is LiPF6. The lithium salts listed above may be used alone or in combination of two or more kinds.

[0070] The concentration of electrolytes such as lithium salt in the final composition of the non-aqueous electrolyte of Invention B is arbitrary as long as the effects of the present invention are not significantly impaired, but preferably it is 0.5 mol / L or more, more preferably 0.6 mol / L or more, still more preferably 0.7 mol / L or more. On the other hand, preferably it is 3 mol / L or less, more preferably 2 mol / L or less, still more preferably 1.8 mol / L or less. By the electrolyte concentration being within the above range, the ionic conductivity can be appropriately increased. Also, when two or more kinds of electrolytes are used in combination, the ratio of each electrolyte is arbitrary.

[0071] <B5. Additive> In addition to the various compounds mentioned above, the non-aqueous electrolyte of Invention B may contain various additives as long as the effects of Invention B are not significantly impaired. Examples of the additives include compounds having a cyano group such as malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile, undecanedinitrile, dodecanedinitrile, etc.; carboxylic anhydride compounds such as acrylic anhydride, 2-methylacrylic anhydride, 3-methylacrylic anhydride, benzoic anhydride, 2-methylbenzoic anhydride, 4-methylbenzoic anhydride, 4-tert-butylbenzoic anhydride, 4-fluorobenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, methoxyformic anhydride, ethoxyformic anhydride, succinic anhydride, maleic anhydride, etc.; thioether compounds such as trimethyl[2-(phenylthio)ethoxy]silane, trimethyl[1-fluoro-2-(phenylthio)ethoxy]silane, trimethyl[2-fluoro-2-(phenylthio)ethoxy]silane, etc.; cyclic carbonates having an unsaturated bond such as vinylene carbonate, vinyl ethylene carbonate, etc.; carbonates having a fluorine atom such as fluoroethylene carbonate, etc.; sulfonic acid ester compounds such as 1,3-propane sultone, etc.; phosphates such as lithium difluorophosphate and sulfonates such as lithium fluorosulfonate; etc. However, although lithium difluorophosphate and lithium fluorosulfonate mentioned here fall under the category of lithium salts, they are not treated as electrolytes from the viewpoint of the ionization degree with respect to the non-aqueous solvent used in the non-aqueous electrolyte and are regarded as additives. Also, examples of overcharge preventives include cyclohexylbenzene, t-butylbenzene, t-amylbenzene, biphenyl, alkyl biphenyl, terphenyl, partially hydrogenated terphenyl, diphenyl ether, dibenzofuran, etc. These compounds may be used in appropriate combinations. Among these, from the viewpoint of the capacity retention rate, vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, and lithium fluorosulfonate are particularly preferable, and it is particularly preferable to use them in combination. ; cyclic carbonates having an unsaturated bond such as vinylene carbonate, vinyl ethylene carbonate, etc.; carbonates having a fluorine atom such as fluoroethylene carbonate, etc.; sulfonic acid ester compounds such as 1,3-propane sultone, etc.; phosphates such as lithium difluorophosphate and sulfonates such as lithium fluorosulfonate; etc. However, although lithium difluorophosphate and lithium fluorosulfonate mentioned here fall under the category of lithium salts, they are not treated as electrolytes from the viewpoint of the ionization degree with respect to the non-aqueous solvent used in the non-aqueous electrolyte and are regarded as additives. Also, examples of overcharge preventives include cyclohexylbenzene, t-butylbenzene, t-amylbenzene, biphenyl, alkyl biphenyl, terphenyl, partially hydrogenated terphenyl, diphenyl ether, dibenzofuran, etc. These compounds may be used in appropriate combinations. Among these, from the viewpoint of the capacity retention rate, vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, and lithium fluorosulfonate are particularly preferable, and it is particularly preferable to use them in combination.

[0072] [Non-aqueous electrolyte battery] A non-aqueous electrolyte secondary battery (hereinafter sometimes referred to as "the non-aqueous electrolyte secondary battery of the present invention") can be formed using the non-aqueous electrolyte of the present invention A or the non-aqueous electrolyte of the present invention B, a positive electrode, and a negative electrode. A non-aqueous electrolyte secondary battery according to one embodiment of the present invention A is a non-aqueous electrolyte secondary battery including a negative electrode capable of occluding and releasing metal ions, a positive electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is the non-aqueous electrolyte of the present invention A. A non-aqueous electrolyte secondary battery according to one embodiment of the present invention B is a non-aqueous electrolyte secondary battery including a negative electrode capable of occluding and releasing metal ions, a positive electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is the non-aqueous electrolyte of the present invention B. Examples of non-aqueous electrolyte secondary batteries include lithium-ion secondary batteries and sodium-ion secondary batteries, etc., and a lithium-ion secondary battery is preferred. A lithium-ion secondary battery generally includes the non-aqueous electrolyte of the present invention A or the non-aqueous electrolyte of the present invention B, a current collector, a positive electrode active material layer provided on the current collector and capable of occluding and releasing lithium ions, a current collector, and a negative electrode active material layer provided on the current collector and capable of occluding and releasing lithium ions.

[0073] <1. Positive electrode>[ The positive electrode usually has a positive electrode active material layer on a current collector, and the positive electrode active material layer contains a positive electrode active material. Examples of positive electrode materials used as positive electrode active materials for the positive electrode of the non-aqueous electrolyte secondary battery of the present invention include lithium transition metal composite oxides such as lithium cobalt composite oxide represented by a basic composition of LiCoO2, lithium nickel composite oxide represented by LiNiO2, lithium manganese composite oxides represented by LiMnO2 and LiMn2O4, transition metal oxides such as manganese dioxide, and mixtures of these composite oxides, etc. Further, TiS2, FeS2, Nb3S4, Mo3S4, CoS2, V2O5, CrO3, V3O3, FeO2, GeO2, and Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3)O2, LiFePO4, etc. can be used. From the perspective of volumetric density, Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2、 Li(Ni 0.5 Mn 0.2 Co 0.3 )O 2、 Li(Ni 0.6 Mn 0.2 Co 0.2 )O 2、 Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2、 Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc. are particularly preferred.

[0074] <2. Negative Electrode> The negative electrode usually has a negative electrode active material layer on a current collector, and the negative electrode active material layer contains a negative electrode active material. Hereinafter, the negative electrode active material will be described. As the negative electrode active material, there is no particular limitation as long as it can electrochemically occlude and release s-block metal ions such as lithium ions, sodium ions, potassium ions, and magnesium ions. Specific examples thereof include carbonaceous materials, metal compound-based materials, and their oxides, carbides, nitrides, silicides, sulfides, phosphides, etc. These may be used alone or in any combination of two or more.

[0075] ​The carbonaceous material used as the negative electrode active material is not particularly limited, and examples thereof include graphite, amorphous carbon, and carbonaceous substances with low graphitization degree. Examples of the types of graphite include natural graphite and artificial graphite. Further, those coated with carbonaceous substances such as amorphous carbon or graphitized products may also be used. Examples of amorphous carbon include particles obtained by firing bulk mesophase and particles obtained by infusibilizing a carbon precursor and then firing. Examples of carbonaceous substance particles with low graphitization degree include those obtained by firing an organic substance at a temperature usually lower than 2500°C. These may be used alone or in any combination of two or more. It is also preferable to use a combination of the carbonaceous material and Si as the negative electrode active material.

[0076] The metal compound-based material used as the negative electrode active material is not particularly limited, and examples thereof include compounds containing metals or semimetals such as Ag, Al, Bi, Cu, Ga, Ge, In, Ni, Pb, Sb, Si, Sn, Sr, and Zn. Among these, simple substances, alloys, oxides, carbides, nitrides, etc. of silicon (Si) or tin (Sn) are preferable, and in particular, Si simple substance and SiOx (0.5 ≤ O ≤ 1.6) are preferable from the viewpoints of capacity per unit mass and environmental load.

[0077] <3. Separator> A separator is usually interposed between the positive electrode and the negative electrode to prevent short circuit. In this case, the non-aqueous electrolyte is usually impregnated into this separator and used. There are no particular restrictions on the material and shape of the separator, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired.

[0078] The material of the separator is not particularly limited as long as it is stable with respect to the non-aqueous electrolyte. For example, polyolefins such as polyethylene and polypropylene, resins such as polytetrafluoroethylene and polyethersulfone; oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, sulfates such as barium sulfate and calcium sulfate, glass filters made of glass fiber, etc. can be used. Among these, glass filters or polyolefins are preferred, and polyolefins are more preferred. These materials may be used alone, or two or more of them may be used in combination in any combination and ratio. Also, the above materials may be laminated and used.

[0079] The thickness of the separator is arbitrary, but it is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more. Also, it is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is too thin than the above range, the insulation and mechanical strength may decrease. Also, if it is too thick than the above range, not only may the battery performance such as rate characteristics decrease, but also the energy density of the entire non-aqueous electrolyte secondary battery may decrease.

[0080] Examples of the form of the separator include thin film shapes such as non-woven fabrics, woven fabrics, and microporous films. In the case of a thin film shape, those with a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the independent thin film shape, a separator formed by forming a composite porous layer containing inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, alumina particles with a particle size of less than 1 μm for 90% on both sides of the positive electrode can be used to form a porous layer using a fluororesin as a binder.

[0081] As the form of the separator, a porous sheet or non-woven fabric with excellent liquid retention properties is preferred. When using a porous separator such as a porous sheet or non-woven fabric, the porosity of the separator is arbitrary, but it is usually 20% or more, preferably 35% or more, more preferably 45% or more, and usually 90% or less, preferably 85% or less, more preferably 75% or less. If the porosity is too small compared to the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. On the other hand, if it is too large compared to the above range, the mechanical strength of the separator tends to decrease and the insulation property tends to decrease.

[0082] Also, the average pore diameter of the separator is arbitrary, but it is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. If the average pore diameter exceeds the above range, short circuits are likely to occur. On the other hand, if it is below the above range, the membrane resistance may increase and the rate characteristics may deteriorate.

[0083] <4. Conductive Material> The above-mentioned positive electrode and negative electrode may contain a conductive material for improving conductivity. As the conductive material, known conductive materials can be arbitrarily used. Specific examples include metal materials such as copper and nickel; graphite (graphite) such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke. Note that the conductive material may be used alone or in combination of two or more in any combination and ratio.

[0084] The conductive material is usually used in an amount of 0.01 part by mass or more, preferably 0.1 part by mass or more, more preferably 1 part by mass or more, and usually 50 parts by mass or less, preferably 30 parts by mass or less, more preferably 15 parts by mass or less, based on 100 parts by mass of the positive electrode material or negative electrode material. If the content of the conductive material is less than the above range, the conductivity may be insufficient. On the other hand, if the content of the conductive material exceeds the above range, the battery capacity may decrease. In this specification, the positive electrode material is a positive electrode mixture containing a positive electrode active material, a conductive material, a binder, etc. The negative electrode material is a negative electrode mixture containing a negative electrode active material, a binder, a thickener, etc.

[0085] <5. Binder> The above-mentioned positive electrode and negative electrode may contain a binder for improving the binding property. The binder is not particularly limited as long as it is a material stable to the non-aqueous electrolyte and the solvent used during electrode manufacturing. In the case of the coating method, it may be a material that is dissolved or dispersed in the liquid medium used during electrode manufacturing. Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber; thermoplastic elastomer-like polymers such as styrene-butadiene-styrene block copolymer or its hydrogenated product, EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer or its hydrogenated product; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, and propylene-α-olefin copolymer; fluorine-based polymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, and tetrafluoroethylene-ethylene copolymer; polymer compositions having ionic conductivity of alkali metal ions (especially lithium ions); and the like. These substances may be used alone or in combination of two or more in any combination and ratio.

[0086] The proportion of the binder is usually 0.1 part by mass or more with respect to 100 parts by mass of the positive electrode material or negative electrode material, preferably 1 part by mass or more, more preferably 3 parts by mass or more. Also, it is usually 50 parts by mass or less, preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less. When the proportion of the binder is within the above range, the binding property of the electrode can be sufficiently maintained, the mechanical strength of the electrode is maintained, which is preferable in terms of cycle characteristics, battery capacity, and conductivity.

[0087] <6. Liquid Medium> As the liquid medium for forming the slurry, there is no particular limitation on the type as long as it is a solvent capable of dissolving or dispersing the active material, the conductive material, the binder, and, if necessary, the thickener to be used, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include, for example, water, a mixed solvent of alcohol and water, and the like. Examples of the organic solvent include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide. The liquid medium may be used alone or in combination of two or more in any combination and ratio.

[0088] <7. Thickener> When an aqueous medium is used as the liquid medium for forming the slurry, it is preferable to slurrize using a thickener and a latex such as styrene-butadiene rubber (SBR). The thickener is usually used to adjust the viscosity of the slurry. The thickener is not limited as long as the effects of the present invention are not significantly limited. Specifically, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof can be mentioned. These may be used alone or in combination of two or more in any combination and ratio.

[0089] When a thickening agent is further used, it is usually 0.1 part by mass or more, preferably 0.5 part by mass or more, more preferably 0.6 part by mass or more, and usually 5 parts by mass or less, preferably 3 parts by mass or less, more preferably 2 parts by mass or less, based on 100 parts by mass of the positive electrode material or the negative electrode material. If it is less than the above range, the coatability may be significantly reduced. If it exceeds the above range, the proportion of the active material in the active material layer may decrease, resulting in problems such as a decrease in the battery capacity and an increase in the resistance between the active materials.

[0090] <8. Current collector> The material of the current collector is not particularly limited, and known materials can be arbitrarily used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, and copper; and carbonaceous materials such as carbon cloth and carbon paper. Among these, metal materials, especially aluminum, are preferred.

[0091] As for the shape of the current collector, in the case of metal materials, metal foils, metal cylinders, metal coils, metal plates, metal thin films, expanded metals, punched metals, foamed metals, etc. can be mentioned. In the case of carbonaceous materials, carbon plates, carbon thin films, carbon cylinders, etc. can be mentioned. Among these, metal thin films are preferred. The thin film may be formed in a mesh shape as appropriate. The thickness of the current collector is arbitrary, but it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. When the thin film is within the above range, the strength required for the current collector is maintained, and it is also preferable from the viewpoint of handleability.

[0092] <9. Battery design> [Electrode group] The electrode group may be either a laminated structure formed by sandwiching the aforementioned positive electrode (also referred to as "positive electrode plate") and negative electrode (also referred to as "negative electrode plate") with the aforementioned separator, or a structure formed by winding the aforementioned positive electrode plate and negative electrode plate spirally with the aforementioned separator in between. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. If the electrode group occupancy rate is below the above range, the battery capacity will be reduced. On the other hand, if it exceeds the above range, the void space will be small, and when the battery gets hot, the members may expand, the vapor pressure of the liquid component of the electrolyte may increase, and the internal pressure may rise, deteriorating various characteristics such as the charge-discharge cycle performance and high-temperature storage performance of the battery. Furthermore, the gas release valve for releasing the internal pressure to the outside may operate.

[0093] [Current collection structure] The current collection structure is not particularly limited, but in order to more effectively improve the discharge characteristics of the non-aqueous electrolyte of the present invention, it is preferable to adopt a structure that reduces the resistance of the wiring part and the joint part. When the internal resistance is reduced in this way, the effect of using the non-aqueous electrolyte of the present invention is particularly well exhibited.

[0094] When the electrode group has the aforementioned laminated structure, a structure formed by bundling the metal core portions of each electrode layer and welding them to the terminal is preferably used. When the area of a single electrode becomes large, the internal resistance increases, so it is also preferably used to provide a plurality of terminals in the electrode to reduce the resistance. When the electrode group has the aforementioned wound structure, a plurality of lead structures are provided for the positive electrode and the negative electrode respectively, and by bundling them to the terminal, the internal resistance can be lowered.

[0095] [Protection element] As protection elements, there are PTC (Positive Temperature Coefficient) elements whose resistance increases along with heat generation due to excessive current or the like, thermal fuses, thermistors, valves (current cutoff valves) that cut off the current flowing through the circuit due to a rapid increase in the internal pressure or internal temperature of the battery during abnormal heat generation, and the like. It is preferable to select a protection element that does not operate under normal use conditions of high current. From the perspective of high output, it is more preferable to design such that abnormal heat generation or thermal runaway does not occur even without a protection element.

[0096] [Outer casing] The non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the above non-aqueous electrolyte, negative electrode, positive electrode, separator, etc. in an outer casing. There is no limitation on this outer casing, and a known one can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Specifically, it is not particularly limited as long as it is a substance stable with respect to the non-aqueous electrolyte used. Usually, for example, metals such as nickel-plated steel sheets, stainless steel, aluminum or aluminum alloys, nickel, titanium, magnesium alloys; or laminated films (laminate films) of resin and aluminum foil; etc. are used. From the perspective of weight reduction, metals such as aluminum or aluminum alloys and laminate films are preferably used.

[0097] In the outer casing using the above metals, those having a sealed structure by welding metals to each other by laser welding, resistance welding, or ultrasonic welding, or those having a caulked structure using the above metals via a resin gasket can be mentioned. In the outer casing using the laminate film, those having a sealed structure by thermally fusing resin layers to each other can be mentioned. In order to improve the sealing property, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when the resin layer is thermally fused through the current collector terminal to form a sealed structure, since it is a joint between metal and resin, a resin having a polar group or a modified resin into which a polar group is introduced is preferably used as the interposed resin.

[0098] [2-4-5. Shape]​ Also, the shape of the exterior body is arbitrary, and it may be, for example, cylindrical, rectangular, laminated, coin-shaped, large-sized, or any other shape.

Examples

[0099] [Experiment A] Hereinafter, the present invention A will be described in more detail with reference to examples and comparative examples. However, the present invention A is not limited to these examples as long as the gist thereof is not exceeded.

[0100] [Preparation of non-aqueous electrolyte] (Examples A1 to A14, Comparative Examples A1 to A13) A mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3:7) was dissolved with LiPF6 at a ratio of 1 mol / L to prepare an electrolyte, which was designated as basic electrolyte A. The following compounds were added to this basic electrolyte to adjust the electrolyte to the contents (mass %) shown in Tables 1 to 4. In the tables, “heteroatom-containing lithium salt (A)” is denoted as “lithium salt (A)”, “heteroatom-containing lithium salt (A)” is denoted as “lithium salt (A)”, and “heteroatom-containing lithium salt (C)” is denoted as “lithium salt (C)”, respectively. Note that the “content (mass %)” in the tables is the content of the compound when the total amount of the non-aqueous electrolyte is 100 mass %.

[0101] <Compound> Compound 1-1: 2,2,2-trifluoroethyl acrylate

[0102]

Chemical formula

[0103] Compound 1-2: 2,2,2-trifluoroethyl methacrylate

[0104]

Chemical formula

[0105] Compounds 1-3: 1,1,1,3,3,3-Hexafluoroisopropyl acrylate

[0106]

Chem.

[0107] Compounds 1-4: 1,1,1,3,3,3-Hexafluoroisopropyl methacrylate

[0108]

Chem.

[0109] Compound 2: 2,2,3,3-Tetrafluoropropyl methacrylate

[0110]

Chem.

[0111] Compound A-1: Lithium fluorosulfonate

[0112]

Chem.

[0113] Compound A-2: Lithium bis(fluorosulfonyl)imide

[0114]

Chem.

[0115] Compound B: Lithium bisoxalate borate

[0116]

Chem.

[0117] Compound C: Lithium difluorophosphate

[0118] [Chemistry]

[0119] Compound D: Lithium Tetrafluoroborate

[0120] [Chemistry]

[0121] [Fabrication of Electrodes] (Examples A1 - 11, Comparative Examples A1 - A13) 50 parts by mass of SiO as the negative electrode active material, 25 parts by mass of polyacrylic acid as the binder, and 25 parts by mass of carbon black as the conductive material were kneaded with a mixer to form a slurry. The obtained slurry was applied to a copper foil with a thickness of 20 μm by the blade method, dried, and rolled with a press machine to fabricate a negative electrode sheet. The fabricated negative electrode sheet was punched into a disk shape with a diameter of 12.5 mm to obtain a negative electrode. Also, a lithium metal foil was punched into a disk shape with a diameter of 14 mm to obtain a counter electrode.

[0122] (Examples A12 - A14) 3 parts by mass of Si and 94.5 parts by mass of a carbonaceous material as the negative electrode active material, 1.5 parts by mass of sodium carboxymethyl cellulose as the thickener, and 1 part by mass of styrene - butadiene rubber as the binder were kneaded with a mixer to form a slurry. The obtained slurry was applied to a copper foil with a thickness of 20 μm by the blade method, dried, and rolled with a press machine to fabricate a negative electrode sheet. The fabricated negative electrode sheet was punched into a disk shape with a diameter of 12.5 mm to obtain a negative electrode. Also, a lithium metal foil was punched into a disk shape with a diameter of 14 mm to obtain a counter electrode.

[0123] [Fabrication of Lithium Secondary Batteries] (Examples A1 - A14, Comparative Examples A1 - A16) The above - mentioned negative electrode, a separator impregnated with the prepared electrolyte solution, and the counter electrode were laminated and sealed in a coin - type metal container to fabricate a coin - type lithium - ion secondary battery.

[0124] [Charge and Discharge Measurement] (Examples A1 - A14, Comparative Examples A1 - A16) At 25°C, charge and discharge were performed 4 times with a voltage range of 1.5V - 5mV and a current value of 1C to stabilize the battery. Then, after charging to 5mV at a current value of 0.1C, it was further charged at a constant voltage of 5mV until the current density reached 0.01C, and then discharged to 1500mV at a current value of 0.1C. Th e discharge capacity at this time was taken as the reference capacity. Then, as a high - rate test, after charging to 5mV at 1C, it was further charged at a constant voltage of 5mV until the current density reached 0.01C, and the evaluation of discharging to 1500mV at 1C was performed 19 cycles. Finally, after charging to 5mV at a current value of 0.1C, it was further charged at a constant voltage of 5mV until the current density reached 0.01C, and an operation of discharging to 1500mV at a current value of 0.1C was performed, and this discharge capacity was taken as the discharge capacity after the cycle test.

[0125] [Evaluation of Durability] (Examples A1 - A14, Comparative Examples A1 - A16) The cycle capacity retention rate (%) was obtained from [(Discharge capacity after cycle test) / (Reference capacity)]×100. In Examples A2 - A11 and Comparative Examples A1 - A16, it was normalized so that the retention rate of Example A1 was 100. Examples A13 and A14 were normalized so that the retention rate of Example A12 was 100. The results are shown in Tables 1 - 4. Note that the lithium secondary batteries of Examples A12 - A14 have different negative electrode active materials from the lithium secondary battery of Example A1, but when Example A1 is set to 100, the retention rates of Examples A12 - A14 are 90, 91, and 92 respectively.

[0126] [Evaluation of Charging Characteristics] (Examples A1 - A14, Comparative Examples A1 - A16) In the above charge-discharge measurement, the charge capacity at the 19th cycle of the high-rate test was defined as the charge capacity at high rate. The higher this capacity, the higher the high-current charge characteristics can be said to be. In Examples A2 to A11 and Comparative Examples A1 to A16, they were normalized so that the charge capacity at high rate of Example A1 became 100. Examples A13 and A14 were normalized so that the charge capacity at high rate of Example A12 became 100. Also, in the 19th cycle of the high-rate test, the time required to charge to 50% of the reference capacity was defined as the charge time at high rate. The shorter this time, the higher the high-current charge characteristics can be said to be. In Examples A2 to A11 and Comparative Examples A1 to A16, they were normalized so that the charge time at high rate of Example A1 became 100. Examples A13 and A14 were normalized so that the charge capacity at high rate of Example A12 became 100. The results are shown in Tables 1 to 4. Note that the lithium secondary batteries of Examples A12 to A14 have different negative electrode active materials from those of the lithium secondary battery of Example A1, but when Example A1 is set to 100, the charge times at high rate of Examples A12 to A14 were 150, 149, and 147, respectively.

[0127]

Table 1

[0128]

Table 2

[0129]

Table 3

[0130]

Table 4

[0131] As is clear from Tables 1, 3, and 4 above, it can be seen that the batteries manufactured in Examples A1 to A11 have a high maintenance rate, a high charge capacity at high rates, and a short charge time at high rates compared to Comparative Examples A1 to A16. This result indicates that by using a non-aqueous electrolyte having a composition containing a specific fluorine-containing carboxylic acid ester compound (Compound (1)) and a specific heteroatom-containing lithium salt, the durability and charge characteristics of the non-aqueous electrolyte secondary battery are compatible and excellent. As can be seen from Examples A1 to A4 and Comparative Examples A5 to A8, and Examples A1, A5, A6, A7 and Comparative Examples A1 to A4, only when Compound (1) and a specific heteroatom-containing lithium salt are simultaneously contained, a synergistic effect on durability and charge characteristics is exhibited. Also, as can be seen from Examples A1 to A4 and Comparative Examples A12 to A15, among the fluorine-containing carboxylic acid ester compounds having an acryloyl group or a methacryloyl group as a partial structure, only when it corresponds to Compound (1), a good effect is exhibited. Further, as can be seen from Example A1 and Comparative Example A16, a good effect is exhibited only when a specific heteroatom-containing lithium salt is used. Also, from Examples A12 to A14, it can be seen that even when a carbonaceous material and Si are used in combination as the negative electrode active material, a non-aqueous electrolyte secondary battery having excellent durability and charge characteristics is obtained by using the non-aqueous electrolyte according to Invention A. In addition, although the cycle test periods in each of the Examples and Comparative Examples shown in Tables 1 to 4 above were carried out as a relatively short period in a model manner, significant differences have been confirmed. Since the actual use of the non-aqueous electrolyte secondary battery may extend for several years, it can be understood that these differences in results will become more significant when long-term use is assumed.

[0132] [Experiment B] Hereinafter, the present invention B will be described more specifically with reference to Examples and Comparative Examples. However, the present invention B is not limited to these Examples as long as the gist thereof is not exceeded. (Examples B1 to B9, Comparative Examples B1 to B6) [Preparation of Non-aqueous Electrolyte] A mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3:7) was prepared by dissolving LiPF6 at a ratio of 1 mol / L to obtain a basic electrolyte B. The following compounds were added to this basic electrolyte B in the mass percentages shown in Table 5 to prepare the electrolyte. Note that the "content (mass %)" in the table is the content of the compound when the total amount of the non-aqueous electrolyte is 100 mass %.

[0133] <Compound> Compound B1-1: 2,2,2-trifluoroethyl methacrylate

[0134]

Chemical formula

[0135] Compound B1-2: 2,2,2-trifluoroethyl acrylate

[0136]

Chemical formula

[0137] Compound B1-3: 1,1,1,3,3,3-hexafluoroisopropyl acrylate

[0138]

Chemical formula

[0139] Compound B2: Triallyl isocyanurate

[0140]

Chemical formula

[0141] Compound B3-1: 1,3-bis(isocyanatomethyl)cyclohexane

[0142]

Chemical formula

[0143] Compound B3-2: Hexamethylene diisocyanate

[0144] [Chemical Structure]

[0145] [Fabrication of Electrodes] As the negative electrode active material, 50% by mass of SiO, 25% by mass of polyacrylic acid as the binder, and 25% by mass of carbon black as the conductive material were kneaded with a mixer and slurried. The obtained slurry was applied to a copper foil with a thickness of 20 μm by the blade method, dried, and rolled with a press machine. The fabricated negative electrode sheet was punched into a disc shape with a diameter of 12.5 mm to obtain a negative electrode. Also, a lithium metal foil was punched into a disc shape with a diameter of 14 mm to obtain a counter electrode.

[0146] [Fabrication of Lithium Secondary Battery] The above negative electrode, a separator impregnated with the prepared electrolyte solution, and the counter electrode were laminated and sealed in a coin-type metal container to fabricate a coin-type lithium-ion secondary battery. [Charge and Discharge Measurement] At 25 °C, after charging to 5 mV at a current value of 0.1C in a voltage range of 1.5V to 5mV, further charging was performed at a constant voltage of 5 mV until the current density reached 0.01C, and discharging was performed at a current value of 0.1C until 1500 mV (hereinafter referred to as the low-rate test). This operation was performed 3 times to stabilize the battery. The discharge capacity of the third time of this operation was used as the reference capacity. Thereafter, as the high-rate test, after charging to 5 mV at 1C, further charging was performed at a constant voltage of 5 mV until the current density reached 0.01C, and an evaluation of discharging at 1C until 1500 mV was performed for 19 cycles. Thereafter, the low-rate test was performed once, and the high-rate test was further performed for 19 cycles. Finally, the low-rate test was performed, and this discharge capacity was used as the discharge capacity after the cycle test.

[0147] [Evaluation of Durability] The cycle capacity retention rate (%) was determined from [(discharge capacity after the cycle test) / (reference capacity)] × 100. In Examples B2 to B9 and Comparative Examples B1 to B6, it was normalized so that the retention rate of Example B1 became 100. The results are shown in Table 5. [Evaluation of charging characteristics] In the above charge-discharge measurement, at the 19th cycle of the high-rate test, the time required to charge 50% of the reference capacity was defined as the charging time at high rate. It can be said that the shorter this time, the higher the high-current charging characteristics. Examples B2 to B9 and Comparative Examples B1 to B6 were normalized so that the charging time at high rate of Example B1 became 100. The results are shown in Table 5.

[0148] [Table 5]

[0149] As is clear from Table 5 above, it can be seen that the batteries manufactured in Examples B1 to B9 have a higher retention rate and a shorter charging time at high rate than Comparative Examples B1 to B6. This result shows that by using a non-aqueous electrolyte having a composition containing a specific compound (Compound (2)) having an acryloyl group or a methacryloyl group as a partial structure and a fluorine atom-containing hydrocarbon group and a specific nitrogen-containing compound, the durability and charging characteristics of the non-aqueous electrolyte secondary battery are compatible and excellent. From these results, it can be seen that only when Compound (2) and the specific nitrogen-containing compound are contained simultaneously, they synergistically exert a good effect on the durability and charging characteristics. In addition, although the cycle test periods in each of the above Examples and Comparative Examples shown in Table 5 were carried out as a relatively short period model, significant differences have been confirmed. The actual use of non-aqueous electrolyte secondary batteries may extend for several years Therefore, it can be understood that the difference in these results will become more significant when long-term use is assumed.

[0150] This application is based on Japanese Patent Application (Japanese Patent Application No. 2019-184550) filed on October 7, 2019 and Japanese Patent Application (Japanese Patent Application No. 2019-184551) filed on October 7, 2019, the contents of which are incorporated herein by reference.

Industrial Applicability

[0151] The non-aqueous electrolyte of the present invention can provide a non-aqueous electrolyte secondary battery that is excellent in both durability and charging characteristics. Therefore, the non-aqueous electrolyte of the present invention and the non-aqueous electrolyte secondary battery obtained using the same can be used for various known applications. Specific examples of the applications of the non-aqueous electrolyte of the present invention include, for example, notebook computers, pen input computers, mobile computers, e-book players, mobile phones, mobile faxes, mobile copiers, mobile printers, headphone stereos, video movies, liquid crystal TVs, handy cleaners, portable CDs, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game devices, watches, power tools, strobes, cameras, household backup power supplies, industrial backup power supplies, power supplies for load leveling, natural energy storage power supplies, lithium ion capacitors, and the like.

Claims

1. A non-aqueous electrolyte secondary battery comprising a negative electrode having a negative electrode active material layer capable of absorbing and releasing metal ions, a positive electrode, and a non-aqueous electrolyte, the negative electrode active material layer contains SiOx (0.5≦O≦1.6) as a negative electrode active material, The non-aqueous electrolyte solution is The present invention comprises a non-aqueous solvent, a compound represented by the following formula (1), and at least one heteroatom-containing lithium salt selected from the group consisting of (A) a lithium salt having an F-S bond, (B) a lithium salt having an oxalic acid skeleton, and (C) a lithium salt having a P=O bond and a P-F bond: The content of the heteroatom-containing lithium salt is 0.001% by mass or more and 5% by mass or less, A nonaqueous electrolyte secondary battery, in which the content of the compound represented by formula (1) is 0.001% by mass or more and 20% by mass or less. 【Chemistry 1】 (In the above formula (1), R １ represents a hydrogen atom or a methyl group. ２ represents a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 5 carbon atoms which may contain a halogen atom.

2. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material is SiO.

3. The negative electrode active material contains a binder, 3. The nonaqueous electrolyte secondary battery according to claim 1, wherein the amount of the binder is 3 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the negative electrode material.

4. 4. The nonaqueous electrolyte secondary battery according to claim 1, wherein the content of the heteroatom-containing lithium salt in the nonaqueous electrolyte is 0.001% by mass or more and 3% by mass or less.

5. The non-aqueous electrolyte solution is LiPF ６ , LiBF ４ , LiClO ４ , and Li(CF ３ SO ２ ) ２ The nonaqueous electrolyte secondary battery according to claim 1 , further comprising at least one selected from the group consisting of N.

6. 6. The nonaqueous electrolyte secondary battery according to claim 1, wherein the nonaqueous electrolyte further contains a cyclic carbonate compound having a carbon-carbon unsaturated bond or a cyclic carbonate compound having a fluorine atom.

7. A non-aqueous electrolyte secondary battery comprising a negative electrode having a negative electrode active material layer capable of absorbing and releasing metal ions, a positive electrode, and a non-aqueous electrolyte, the negative electrode active material layer contains SiOx (0.5≦O≦1.6) as a negative electrode active material, The non-aqueous electrolyte solution is A non-aqueous electrolyte secondary battery comprising a non-aqueous solvent and a lithium salt as an electrolyte, and comprising: a compound represented by general formula (2); and at least one of a compound represented by general formula (3) and an isocyanate compound; wherein the content of the compound represented by general formula (2) is 0.001% by mass or more and 20% by mass or less, and the content of the compound represented by general formula (3) and / or the isocyanate compound is 0.001% by mass or more and 20% by mass or less. 【Chemistry 2】 (In formula (2), R １１ represents a hydrogen atom or a methyl group. ２１ represents a hydrocarbon group containing a fluorine atom and having 1 to 10 carbon atoms. 【Chemistry 3】 (In formula (3), R ３１ ~R 5１ may be the same or different, and may have a substituent. represents an organic group having 1 to 20 carbon atoms which may be substituted.)

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