Electrolyte and secondary battery

Abstract

To provide an electrolyte or the like which can reduce a resistance value of a secondary battery at a low temperature.SOLUTION: The electrolyte contains a fluorine-containing ether compound (1) represented by the following formula (1), a fluorine-containing ether compound (2) represented by the following formula (2), and lithium bis(fluorosulfonyl)imide. Formula (1): HCF2-CF2-O-Rf1 (where Rf1 represents a C1-5 alkyl group which may be fluorinated). Formula (2): CF3-CHF-CF2-O-Rf2 (where Rf2 represents a C1-5 alkyl group which may be fluorinated).SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to an electrolytic solution and a secondary battery.

Background Art

[0002] With the recent trend towards lighter and smaller electrical products, the development of electrochemical devices such as lithium-ion secondary batteries with high energy density has been underway. In addition, as the application fields of electrochemical devices such as lithium-ion secondary batteries expand, there is a demand for improving their characteristics. In particular, in the future, when lithium-ion secondary batteries are used for in-vehicle applications, improving battery characteristics will become even more important.

[0003] Patent Document 1 describes an electrolytic solution for a secondary battery containing two specific fluorine-containing ether compounds and at least one selected from a specific fluorine-containing phosphate ester compound and a specific sulfone compound in specific contents. Patent Document 2 describes a secondary battery including a negative electrode and an electrolytic solution, wherein the negative electrode contains a negative electrode active material containing a silicon-containing compound, and the electrolytic solution contains a specific fluorine-containing ether compound, a specific fluorine-containing phosphate ester compound, a specific sulfone compound, and a cyclic carbonate compound in specific contents. Patent Document 3 describes a non-aqueous electrolytic solution containing a solvent for dissolving an electrolyte salt containing a fluorine-containing solvent, at least one compound selected from the group consisting of a specific cyclic siloxane compound, a specific fluorosilane compound, and a specific compound, and an electrolyte salt.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to provide an electrolytic solution capable of reducing the resistance value of a secondary battery at low temperature, and a secondary battery including the electrolytic solution.

Means for Solving the Problems

[0006] The present disclosure (1) relates to an electrolytic solution containing a fluorinated ether compound (1) represented by the following formula (1), a fluorinated ether compound (2) represented by the following formula (2), and lithium bis(fluorosulfonyl)imide. Formula (1): HCF2-CF2-O-Rf 1 (In the formula, Rf 1 is an optionally fluorinated alkyl group having 1 to 5 carbon atoms) Formula (2): CF3-CHF-CF2-O-Rf 2 (In the formula, Rf 2 is an optionally fluorinated alkyl group having 1 to 5 carbon atoms)

[0007] The present disclosure (2) is the electrolytic solution of the present disclosure (1) in which the total content of the fluorinated ether compounds (1) and (2) is 5 to 90% by volume with respect to the electrolytic solution.

[0008] The present disclosure (3) is the electrolytic solution of the present disclosure (1) or (2) in which the total content of the fluorinated ether compounds (1) and (2) is 20 to 90% by volume with respect to the electrolytic solution.

[0009] The present disclosure (4) is an electrolytic solution in any combination with any one of the present disclosures (1) to (3) in which the content of lithium bis(fluorosulfonyl)imide is 0.01 to 8 M with respect to the electrolytic solution.

[0010] The electrolyte solution of the present disclosure (5) is any combination of the present disclosures (1) to (4) in which the content of the fluorine-containing ether compound (2) is 0.00005 to 6% by volume with respect to the fluorine-containing ether compound (1).

[0011] In the present disclosure (6), the Rf in the above formula (1) 1 is a fluorinated alkyl group having 1 to 3 carbon atoms, and the Rf in the above formula (2) 2 is a fluorinated alkyl group having 1 to 3 carbon atoms, and it is an electrolyte solution of any combination of any of the present disclosures (1) to (5).

[0012] In the present disclosure (7), the fluorine-containing ether compound (1) is at least one selected from the group consisting of HCF2CF2OCH2CF2CF2H and CH3CH2CH2OCF2CF2H, and the fluorine-containing ether compound (2) is at least one selected from the group consisting of CF3CHFCF2OCH2CF2CF2H and CH3CH2CH2OCF2CHFCF3, and it is an electrolyte solution of any combination of any of the present disclosures (1) to (6).

[0013] In the present disclosure (8), the fluorine-containing ether compound (1) is HCF2CF2OCH2CF2CF2H, and the fluorine-containing ether compound (2) is CF3CHFCF2OCH2CF2CF2H, and it is an electrolyte solution of any combination of any of the present disclosures (1) to (7).

[0014] The electrolyte solution of the present disclosure (9) is an electrolyte solution of any combination of any of the present disclosures (1) to (8), further containing at least one solvent selected from the group consisting of carbonate and carboxylic acid ester and a lithium salt.

[0015] The secondary battery of the present disclosure (10) is a secondary battery including an electrolyte solution of any combination of any of the present disclosures (1) to (9).

Advantages of the Invention

[0016] According to the present disclosure, it is possible to provide an electrolyte solution capable of reducing the resistance value of a secondary battery at low temperature, and a secondary battery including the electrolyte solution.

Mode for Carrying Out the Invention

[0017] Hereinafter, the present disclosure will be specifically described.

[0018] The present disclosure relates to an electrolytic solution containing a fluorinated ether compound (1) represented by the following formula (1), a fluorinated ether compound (2) represented by the following formula (2), and lithium bis(fluorosulfonyl)imide. Formula (1): HCF2-CF2-O-Rf 1 (In the formula, Rf 1 is an optionally fluorinated alkyl group having 1 to 5 carbon atoms) Formula (2): CF3-CHF-CF2-O-Rf 2 (In the formula, Rf 2 is an optionally fluorinated alkyl group having 1 to 5 carbon atoms)

[0019] By containing two specific fluorinated ether compounds and lithium bis(fluorosulfonyl)imide, the electrolytic solution of the present disclosure can reduce the resistance value at low temperatures of secondary batteries such as lithium-ion secondary batteries.

[0020] In formula (1), Rf 1 is an optionally fluorinated alkyl group having 1 to 5 carbon atoms. Rf 1 The above alkyl group as Rf preferably has 1 to 4 carbon atoms, and more preferably has 1 to 3 carbon atoms. Rf 1 The above alkyl group as Rf may be linear or branched. Rf 1 may be a fluorinated alkyl group or a non-fluorinated alkyl group, but is preferably a fluorinated alkyl group. Rf 1Among them, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, -CH(CH3)2, -CH2CH(CH3)2, -CF3, -CF2H, -CF2CF3, -CH2CF3, -CH2CF2H, -CH2CFH2, -CH2CH2CF3, -CH2CF2CF3, -CH2CF2CF2H, -CH2CF2CFH2, -CH2CF2CF2CF2CF2H are preferable, and -CH2CF2CF2H is particularly preferable in terms of reducing the resistance value at low temperatures.

[0021] As the fluorine-containing ether compound (1), among others, HCF2CF2OCH3, HCF2CF2OCH2CH3, HCF2CF2OCF3, HCF2CF2OCF2H, HCF2CF2OCF2CF3, HCF2CF2OCH2CF3, HCF2CF2OCH2CF2H, HCF2CF2OCH2CFH2, HCF2CF2OCH2CH2CF3, HCF2CF2OCH2CF2CF3, HCF2CF2OCH2CF2CF2H, HCF2CF2OCH2CF2CFH2, HCF2CF2OCH2CH2CH3, HCF2CF2OCH2CH2CH2CH3, HCF2CF2OCH(CH3)2, HCF2CF2OCH2CH(CH3)2, HCF2CF2OCH2CF2CF2CF2CF2H are preferable, and HCF2CF2OCH2CF2CF2H is particularly preferable in terms of reducing the resistance value at low temperatures.

[0022] The fluorine-containing ether compound (1) may be used alone or in combination of two or more.

[0023] The fluorine-containing ether compound (1) preferably has a fluorine content of 40 to 75% by mass. When having a fluorine content within this range, it becomes particularly excellent in the balance between nonflammability and compatibility. Also, it is preferable in terms of good oxidation resistance and safety. The lower limit of the above fluorine content is more preferably 45% by mass, still more preferably 50% by mass, and particularly preferably 55% by mass. The upper limit is more preferably 70% by mass, and still more preferably 66% by mass. The fluorine content of the fluorine-containing ether compound (1) is a value calculated by {(the number of fluorine atoms × 19) / the molecular weight of the fluorine-containing ether compound (1)} × 100 (%) based on the structural formula of the fluorine-containing ether compound (1).

[0024] In formula (2), Rf 2 is an optionally fluorinated alkyl group having 1 to 5 carbon atoms. Rf 2 The above alkyl group as Rf preferably has 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms. Rf 2 The above alkyl group as Rf may be linear or branched. Rf 2 may be a fluorinated alkyl group or a non-fluorinated alkyl group, but is preferably a fluorinated alkyl group. Rf 2 As Rf, among others, methyl group, ethyl group, n-propyl group, n-butyl group, -CH(CH3)2, -CH2CH(CH3)2, -CF3, -CF2H, -CF2CF3, -CH2CF3, -CH2CF2H, -CH2CFH2, -CH2CH2CF3, -CH2CF2CF3, -CH2CF2CF2H, -CH2CF2CFH2, -CH2CF2CF2CF2CF2H are preferred, and -CH2CF2CF2H is particularly preferred from the viewpoint of reducing the resistance value at low temperatures.

[0025] As the fluorine-containing ether compound (2), among others, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, CF3CHFCF2OCF3, CF3CHFCF2OCF2H, CF3CHFCF2OCF2CF3, CF3CHFCF2OCH2CF3, CF3CHFCF2OCH2CF2H, CF3CHFCF2OCH2CFH2, CF3CHFCF2OCH2CH2CF3, CF3CHFCF2OCH2CF2CF3, CF3CHFCF2OCH2CF2CF2H, CF3CHFCF2OCH2CF2CFH2, CF3CHFCF2OCH2CH2CH3, CF3CHFCF2OCH2CH2CH2CH3, CF3CHFCF2OCH(CH3)2, CF3CHFCF2OCH2CH(CH3)2, CF3CHFCF2OCH2CF2CF2CF2CF2H are preferred, and CF3CHFCF2OCH2CF2CF2H is particularly preferred in terms of reducing the resistance value at low temperatures.

[0026] The fluorine-containing ether compound (2) may be used alone or in combination of two or more.

[0027] The combination of the fluorine-containing ether compounds (1) and (2) is not particularly limited, and the above-mentioned ones can be appropriately combined. Among others, in terms of reducing the resistance value at low temperatures, the fluorine-containing ether compound (1) is at least one selected from the group consisting of HCF2CF2OCH2CF2CF2H and CH3CH2CH2OCF2CF2H, and the fluorine-containing ether compound (2) is preferably at least one selected from the group consisting of CF3CHFCF2OCH2CF2CF2H and CH3CH2CH2OCF2CHFCF3, and more preferably the fluorine-containing ether compound (1) is HCF2CF2OCH2CF2CF2H and the fluorine-containing ether compound (2) is CF3CHFCF2OCH2CF2CF2H.

[0028] Preferably, the total content of the fluorine-containing ether compounds (1) and (2) in the electrolyte of the present disclosure is 5 to 90% by volume based on the above electrolyte. In terms of reducing the resistance value at low temperatures, the total content of the fluorine-containing ether compounds (1) and (2) is preferably 10% by volume or more, more preferably 15% by volume or more, still more preferably 20% by volume or more, even more preferably 25% by volume or more, and preferably 85% by volume or less, more preferably 70% by volume or less, still more preferably 60% by volume or less, even more preferably 55% by volume or less, particularly preferably 45% by volume or less, particularly preferably 40% by volume or less, and particularly preferably 35% by volume or less, based on the above electrolyte.

[0029] The content of the fluorine-containing ether compound (1) is preferably 0.00001% by volume or more and less than 90% by volume based on the above electrolyte. In terms of reducing the resistance value at low temperatures, the content of the fluorine-containing ether compound (1) is preferably 0.1% by volume or more, more preferably 0.5% by volume or more, still more preferably 1% by volume or more, even more preferably 5% by volume or more, particularly preferably 8% by volume or more, particularly preferably 10% by volume or more, particularly preferably 15% by volume or more, particularly preferably 20% by volume or more, particularly preferably 25% by volume or more, and preferably 85% by volume or less, more preferably 80% by volume or less, still more preferably 70% by volume or less, even more preferably 60% by volume or less, particularly preferably 55% by volume or less, particularly preferably 45% by volume or less, particularly preferably 40% by volume or less, and particularly preferably 35% by volume or less, based on the above electrolyte.

[0030] The content of the fluorine-containing ether compound (2) is preferably 0.00001% by volume or more and less than 90% by volume with respect to the above electrolytic solution. In terms of reducing the resistance value at low temperatures, the content of the fluorine-containing ether compound (2) is more preferably 0.00008% by volume or more, still more preferably 0.0001% by volume or more, even more preferably 0.001% by volume or more, particularly preferably 0.01% by volume or more, preferably 20% by volume or less, more preferably 10% by volume or less, still more preferably 4% by volume or less, even more preferably 3% by volume or less, particularly preferably 2% by volume or less, particularly more preferably 1% by volume or less, particularly preferably 0.1% by volume or less, and particularly more preferably 0.05% by volume or less with respect to the above electrolytic solution.

[0031] The content of the fluorine-containing ether compound (2) may be 0.00005 to 6% by volume with respect to the fluorine-containing ether compound (1), and preferably 0.001 to 5% by volume. When the content of the fluorine-containing ether compound (2) is within the above range, the resistance value at low temperatures can be further reduced. The content of the fluorine-containing ether compound (2) is more preferably 0.01% by volume or more, still more preferably 0.05% by volume or more, preferably 3% by volume or less, still more preferably 1% by volume or less, even more preferably 0.5% by volume or less, and particularly preferably 0.3% by volume or less with respect to the fluorine-containing ether compound (1).

[0032] The electrolytic solution of the present disclosure contains lithium bis(fluorosulfonyl)imide (LiN(FSO2)2). The content of lithium bis(fluorosulfonyl)imide is preferably 0.01 to 8 M (mol / L) with respect to the above electrolytic solution. In terms of reducing the resistance value at low temperatures, the content of lithium bis(fluorosulfonyl)imide is more preferably 0.05 M or more, still more preferably 0.10 M or more, even more preferably 0.15 M or more, particularly preferably 0.20 M or more, more preferably 5 M or less, still more preferably 4 M or less, even more preferably 3 M or less, and particularly preferably 2 M or less. Also, it is preferably 1 M or less, preferably 0.6 M or less, and preferably 0.4 M or less.

[0033] When lithium bis(fluorosulfonyl)imide is used alone as the electrolyte salt, the content of lithium bis(fluorosulfonyl)imide is preferably 0.01 to 8 M (mol / L) with respect to the above electrolytic solution. In terms of reducing the resistance value at low temperatures, the content of lithium bis(fluorosulfonyl)imide is more preferably 0.05 M or more, still more preferably 0.10 M or more, even more preferably 0.15 M or more, particularly preferably 0.20 M or more, particularly more preferably 0.30 M or more, particularly preferably 0.40 M or more, particularly more preferably 0.50 M or more, particularly more preferably 0.60 M or more, more preferably 5 M or less, still more preferably 3 M or less, even more preferably 2 M or less, and particularly preferably 1 M or less.

[0034] When using an electrolyte salt other than lithium bis(fluorosulfonyl)imide in combination, the content of lithium bis(fluorosulfonyl)imide is preferably 0.01 to 8 M (mol / L) with respect to the above electrolyte solution. In terms of being able to reduce the resistance value at low temperatures, the content of lithium bis(fluorosulfonyl)imide is more preferably 0.05 M or more, still more preferably 0.10 M or more, even more preferably 0.15 M or more, particularly preferably 0.20 M or more with respect to the above electrolyte solution. Also, it is more preferably 5 M or less, still more preferably 4 M or less, even more preferably 3 M or less, particularly preferably 2 M or less, still more preferably 1 M or less, even more preferably 0.6 M or less, and particularly preferably 0.4 M or less.

[0035] The electrolyte solution of the present disclosure preferably contains a solvent. Although the fluorine-containing ether compounds (1) and (2) can be used as the solvent, it can also further contain a solvent other than the fluorine-containing ether compounds (1) and (2).

[0036] The above solvent preferably contains at least one selected from the group consisting of carbonates and carboxylic acid esters.

[0037] The above carbonate may be a cyclic carbonate or a chain carbonate.

[0038] The above cyclic carbonate may be a non-fluorinated cyclic carbonate or a fluorinated cyclic carbonate.

[0039] Examples of the above non-fluorinated cyclic carbonate include non-fluorinated saturated cyclic carbonates, and non-fluorinated saturated alkylene carbonates having an alkylene group with 2 to 6 carbon atoms are preferred, and non-fluorinated saturated alkylene carbonates having an alkylene group with 2 to 4 carbon atoms are more preferred.

[0040] Among them, as the above non-fluorinated saturated cyclic carbonate, at least one selected from the group consisting of ethylene carbonate, propylene carbonate, cis-2,3-pentylene carbonate, cis-2,3-butylene carbonate, 2,3-pentylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 1,2-butylene carbonate, and butylene carbonate is preferable in terms of high dielectric constant and suitable viscosity.

[0041] The above non-fluorinated saturated cyclic carbonate may be used alone, or two or more thereof may be used in combination in any combination and ratio.

[0042] When the above non-fluorinated saturated cyclic carbonate is included, the content of the above non-fluorinated saturated cyclic carbonate is preferably 5 to 90% by volume, more preferably 10 to 60% by volume, and still more preferably 15 to 45% by volume with respect to the above solvent.

[0043] The above fluorinated cyclic carbonate is a cyclic carbonate having a fluorine atom. A solvent containing a fluorinated cyclic carbonate can be suitably used even under a high voltage. In this specification, "high voltage" means a voltage of 4.2 V or more. The upper limit of "high voltage" is preferably 5.5 V, more preferably 5.4 V.

[0044] The above fluorinated cyclic carbonate may be a fluorinated saturated cyclic carbonate or a fluorinated unsaturated cyclic carbonate.

[0045] The above fluorinated saturated cyclic carbonate is a saturated cyclic carbonate having a fluorine atom, and specifically, the following general formula (A):

[0046]

Chemical formula

[0047] When the above-mentioned fluorinated saturated cyclic carbonate is included, when the electrolyte solution of the present disclosure is applied to a high-voltage lithium-ion secondary battery or the like, the oxidation resistance of the electrolyte solution is improved, and stable and excellent charge-discharge characteristics can be obtained. In addition, in this specification, the "ether bond" is a bond represented by -O-.

[0048] From the viewpoints of good dielectric constant and oxidation resistance, one or two of X 1 ~X 4 are preferably -F, a fluorinated alkyl group which may have an ether bond, or a fluorinated alkoxy group which may have an ether bond.

[0049] Since a decrease in viscosity at low temperature, an increase in flash point, and further an improvement in solubility of the electrolyte salt can be expected, X 1 ~X 4 is preferably -H, -F, a fluorinated alkyl group (a), a fluorinated alkyl group (b) having an ether bond, or a fluorinated alkoxy group (c).

[0050] The above-mentioned fluorinated alkyl group (a) is one in which at least one of the hydrogen atoms of the alkyl group is substituted with a fluorine atom. The number of carbon atoms of the fluorinated alkyl group (a) is preferably 1 to 20, more preferably 1 to 17, still more preferably 1 to 7, and particularly preferably 1 to 5. If the carbon number is too large, the low-temperature characteristics may deteriorate or the solubility of the electrolyte salt may decrease. If the carbon number is too small, the solubility of the electrolyte salt may decrease, the discharge efficiency may decrease, and the viscosity may increase.

[0051] Among the fluorinated alkyl groups (a) above, those with 1 carbon atom include CFH2-, CF2H-, and CF3-. In particular, CF2H- or CF3- is preferable in terms of high-temperature storage characteristics, and CF3- is most preferable.

[0052] Among the fluorinated alkyl groups (a) above, those with 2 or more carbon atoms include the following general formula (a-1): R a1 -R a2 - (a-1) (In the formula, R a1 is an alkyl group having 1 or more carbon atoms which may have a fluorine atom; R a2 is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; provided that at least one of R a1 and R a2 has a fluorine atom) can be preferably exemplified in terms of good solubility of the electrolyte salt. In addition, R a1 and R a2 may further have other atoms other than carbon atoms, hydrogen atoms, and fluorine atoms.

[0053] R a1 is an alkyl group having 1 or more carbon atoms which may have a fluorine atom. As R a1 , a linear or branched alkyl group having 1 to 16 carbon atoms is preferable. The carbon number of R a1 is more preferably 1 to 6, and even more preferably 1 to 3.

[0054] R a1 Specifically, as a linear or branched alkyl group, CH3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-,

[0055]

Chemical formula

[0056] include the following, etc.

[0057] In addition, when R a1 is a linear alkyl group having a fluorine atom, examples include CF3-, CF3CH2-, CF3CF2-, CF3CH2CH2-, CF3CF2CH2-, CF3CF2CF2-, CF3CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2-, CF3CH2CF2CH2-, CF3CF2CF2CH2-, CF3CF2CF2CF2-, CF3CF2CH2CF2-, CF3CH2CH2CH2CH2-, CF3CF2CH2CH2CH2-, CF3CH2CF2CH2CH2-, CF3CF2CF2CH2CH2-, CF3CF2CF2CF2CH2-, CF3CF2CH2CF2CH2-, CF3CF2CH2CH2CH2CH2-, CF3CF2CF2CF2CH2CH2-, CF3CF2CH2CF2CH2CH2-, HCF2-, HCF2CH2-, HCF2CF2-, HCF2CH2CH2-, HCF2CF2CH2-, HCF2CH2CF2-, HCF2CF2CH2CH2-, HCF2CH2CF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CH2CH2CH2-, HCF2CH2CF2CH2CH2-, HCF2CF2CF2CF2CH2-, HCF2CF2CF2CF2CH2CH2-, FCH2-, FCH2CH2-, FCH2CF2-, FCH2CF2CH2-, FCH2CF2CF2-, CH3CF2CH2-, CH3CF2CF2-, CH3CF2CH2CF2-, CH3CF2CF2CF2-, CH3CH2CF2CF2-, CH3CF2CH2CF2CH2-, CH3CF2CF2CF2CH2-, CH3CF2CF2CH2CH2-, CH3CH2CF2CF2CH2-, CH3CF2CH2CF2CH2CH2-, CH3CF2CH2CF2CH2CH2-, HCFClCF2CH2-, HCF2CFClCH2-, HCF2CFClCF2CFClCH2-, HCFClCF2CFClCF2CH2-, etc.

[0058] In addition, when Ra1 When it is a branched alkyl group having a fluorine atom,

[0059]

Chemical formula

[0060]

Chemical formula

[0061] etc. are preferably exemplified. However, since having branches such as CH3- or CF3- tends to increase the viscosity, the number thereof is preferably small (1) or zero.

[0062] R a2 is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom. R a2 may be linear or branched. An example of the minimum structural unit constituting such a linear or branched alkylene group is shown below. R a2 is composed of these alone or in combination.

[0063] (i) Linear minimum structural unit: -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2-

[0064] (ii) Branched minimum structural unit:

[0065]

Chemical formula

[0066] Among the above examples, since the dehydrochlorination reaction by a base does not occur and it is more stable, it is preferably composed of structural units not containing Cl.

[0067] R a2When it is linear, it consists only of the above-described linear minimum structural units, and among them, -CH2-, -CH2CH2- or -CF2- is preferable. From the viewpoint of further improving the solubility of the electrolyte salt, -CH2- or -CH2CH2- is more preferable.

[0068] R a2 When it is branched-chain, it contains at least one of the above-described branched-chain minimum structural units, and is preferably exemplified by the general formula -(CX a X b )-(X a is H, F, CH3 or CF3; X b is CH3 or CF3. However, when X b is CF3, X a is H or CH3). These can particularly further improve the solubility of the electrolyte salt.

[0069] Preferable fluorinated alkyl groups (a) include, for example, CF3CF2-, HCF2CF2-, H2CFCF2-, CH3CF2-, CF3CHF-, CH3CF2-, CF3CF2CF2-, HCF2CF2CF2-, H2CFCF2CF2-, CH3CF2CF2-,

[0070]

Chemical formula

[0071]

Chemical formula

[0072] and the like.

[0073] The fluorinated alkyl group (b) having the ether bond is one in which at least one hydrogen atom of the alkyl group having the ether bond is substituted with a fluorine atom. The fluorinated alkyl group (b) having the ether bond preferably has 2 to 17 carbon atoms. If the number of carbon atoms is too large, the viscosity of the fluorinated saturated cyclic carbonate increases, and the number of fluorine-containing groups increases, so that a decrease in the solubility of the electrolyte salt due to a decrease in the dielectric constant and a decrease in the compatibility with other solvents may be observed. From this viewpoint, the number of carbon atoms of the fluorinated alkyl group (b) having the ether bond is more preferably 2 to 10, and even more preferably 2 to 7.

[0074] The alkylene group constituting the ether moiety of the fluorinated alkyl group (b) having the ether bond may be a linear or branched alkylene group. An example of the minimum structural unit constituting such a linear or branched alkylene group is shown below.

[0075] (i) Linear minimum structural unit: -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2-

[0076] (ii) Branched minimum structural unit:

[0077]

Chemical formula

[0078] The alkylene group may be composed of these minimum structural units alone, or may be composed of a combination of linear (i) with each other, branched (ii) with each other, or linear (i) and branched (ii). Preferred specific examples will be described later.

[0079] Among the above examples, since the dehydrochlorination reaction by a base does not occur and it is more stable, it is preferably composed of a structural unit not containing Cl.

[0080] As the more preferred fluorinated alkyl group (b) having an ether bond, the general formula (b-1): R 3 -(OR 4 ) n1 - (b-1) (wherein R 3 may have a fluorine atom, preferably an alkyl group having 1 to 6 carbon atoms; R 4 may have a fluorine atom, preferably an alkylene group having 1 to 4 carbon atoms; n1 is an integer of 1 to 3; provided that at least one of R 3 and R 4 has a fluorine atom).

[0081] R 3 and R 4 can be exemplified as follows, and by appropriately combining these, a fluorinated alkyl group (b) having an ether bond represented by the above general formula (b-1) can be constituted, but it is not limited to these only.

[0082] (1) As R 3 , a general formula: X c 3C-(R 5 ) n2 -(wherein the three X c are the same or different and each is H or F; R 5 is an alkylene group which may have a fluorine atom and has 1 to 5 carbon atoms; n2 is 0 or 1) is preferable.

[0083] When n2 is 0, examples of R 3 include CH3-, CF3-, HCF2- and H2CF-.

[0084] As specific examples when n2 is 1, R 3As straight-chain ones, examples include CF3CH2-, CF3CF2-, CF3CH2CH2-, CF3CF2CH2-, CF3CF2CF2-, CF3CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2-, CF3CH2CF2CH2-, CF3CF2CF2CH2-, CF3CF2CF2CF2-, CF3CF2CH2CF2-, CF3CH2CH2CH2CH2-, CF3CF2CH2CH2CH2-, CF3CH2CF2CH2CH2-, CF3CF2CF2CH2CH2-, CF3CF2CF2CF2CH2-, CF3CF2CH2CF2CH2-, CF3CF2CH2CH2CH2CH2-, CF3CF2CF2CF2CH2CH2-, CF3CF2CH2CF2CH2CH2-, HCF2CH2-, HCF2CF2-, HCF2CH2CH2-, HCF2CF2CH2-, HCF2CH2CF2-, HCF2CF2CH2CH2-, HCF2CH2CF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CH2CH2CH2-, HCF2CH2CF2CH2CH2-, HCF2CF2CF2CF2CH2-, HCF2CF2CF2CF2CH2CH2-, FCH2CH2-, FCH2CF2-, FCH2CF2CH2-, CH3CF2-, CH3CH2-, CH3CF2CH2-, CH3CF2CF2-, CH3CH2CH2-, CH3CF2CH2CF2-, CH3CF2CF2CF2-, CH3CH2CF2CF2-, CH3CH2CH2CH2-, CH3CF2CH2CF2CH2-, CH3CF2CF2CF2CH2-, CH3CF2CF2CH2CH2-, CH3CH2CF2CF2CH2-, CH3CF2CH2CF2CH2CH2-, CH3CH2CF2CF2CH2CH2-, CH3CF2CH2CF2CH2CH2-, etc.

[0085] n2 is 1 and R 3 As branched-chain ones,

[0086] [Chemical formula]

[0087] etc. can be cited.

[0088] However, since the viscosity tends to increase when there are branches such as CH3- or CF3-, R 3 is more preferably linear.

[0089] (2) In -(OR 4 ) n1 - in the general formula (b-1), n1 is an integer of 1 to 3, preferably 1 or 2. When n1 = 2 or 3, R 4 may be the same or different.

[0090] R 4 Preferred specific examples of R can be exemplified by the following linear or branched-chain ones.

[0091] Examples of the linear ones include -CH2-, -CHF-, -CF2-, -CH2CH2-, -CF2CH2-, -CF2CF2-, -CH2CF2-, -CH2CH2CH2-, -CH2CH2CF2-, -CH2CF2CH2-, -CH2CF2CF2-, -CF2CH2CH2-, -CF2CF2CH2-, -CF2CH2CF2-, -CF2CF2CF2-, etc.

[0092] Examples of the branched-chain ones include

[0093]

Chemical formula

[0094] etc.

[0095] The fluorinated alkoxy group (c) is obtained by substituting at least one hydrogen atom of the alkoxy group with a fluorine atom. The fluorinated alkoxy group (c) preferably has 1 to 17 carbon atoms. More preferably, it has 1 to 6 carbon atoms.

[0096] Examples of the fluorinated alkoxy group (c) include the general formula: X d 3C-(R 6 ) n3-O-(three Xs d are the same or different and each is H or F; R 6 is preferably an alkylene group which may have a fluorine atom and has 1 to 5 carbon atoms; n3 is 0 or 1; provided that any of the three Xs d contains a fluorine atom) is particularly preferred.

[0097] Specific examples of the fluorinated alkoxy group (c) include a fluorinated alkoxy group in which an oxygen atom is bonded to the terminal of the alkyl group exemplified as R a1 in the general formula (a-1) above.

[0098] The fluorine content of the fluorinated alkyl group (a), the fluorinated alkyl group (b) having an ether bond, and the fluorinated alkoxy group (c) in the above fluorinated saturated cyclic carbonate is preferably 10% by mass or more. If the fluorine content is too low, there is a risk that the viscosity reduction effect at low temperatures and the flash point increase effect cannot be sufficiently obtained. From this viewpoint, the fluorine content is more preferably 12% by mass or more, and still more preferably 15% by mass or more. The upper limit is usually 76% by mass. The fluorine content of the fluorinated alkyl group (a), the fluorinated alkyl group (b) having an ether bond, and the fluorinated alkoxy group (c) is a value calculated by {(number of fluorine atoms × 19) / formula weight of each group} × 100 (%) based on the structural formula of each group.

[0099] Also, from the viewpoint of good dielectric constant and oxidation resistance, the fluorine content of the entire fluorinated saturated cyclic carbonate is preferably 10% by mass or more, and more preferably 15% by mass or more. The upper limit is usually 76% by mass. The fluorine content of the above fluorinated saturated cyclic carbonate is a value calculated by {(number of fluorine atoms × 19) / molecular weight of the fluorinated saturated cyclic carbonate} × 100 (%) based on the structural formula of the fluorinated saturated cyclic carbonate.

[0100] Specific examples of the above fluorinated saturated cyclic carbonate include, for example, the following.

[0101] X 1 ~X 4 As specific examples of fluorinated saturated cyclic carbonates in which at least one of

[0102]

Chemical formula

[0103] In addition,

[0104]

Chemical formula

[0105] etc. can also be used.

[0106] X 1 ~X 4 As specific examples of fluorinated saturated cyclic carbonates in which at least one of

[0107]

Chemical formula

[0108]

Chemical formula

[0109]

Chemical formula

[0110] etc. can be mentioned.

[0111] X 1 ~X 4At least one of them is a fluorinated alkyl group (b) having an ether bond or a fluorinated alkoxy group (c), and specific examples of the fluorinated saturated cyclic carbonate in which the rest are all -H include

[0112]

Chemical formula

[0113]

Chemical formula

[0114]

Chemical formula

[0115]

Chemical formula

[0116]

Chemical formula

[0117]

Chemical formula

[0118] etc. can be mentioned.

[0119] Among them, as the above fluorinated saturated cyclic carbonate, it is preferably any of the following compounds.

[0120]

Chemical formula

[0121]

Chemical formula

[0122] Examples of the fluorinated saturated cyclic carbonate include trans-4,5-difluoro-1,3-dioxolan-2-one, 5-(1,1-difluoroethyl)-4,4-difluoro-1,3-dioxolan-2-one, 4-methylene-1,3-dioxolan-2-one, 4-methyl-5-trifluoromethyl-1,3-dioxolan-2-one, 4-ethyl-5-fluoro-1,3-dioxolan-2-one, 4-ethyl-5,5-difluoro-1,3-dioxolan-2-one, 4-ethyl-4,5-difluoro-1,3-dioxolan-2-one, 4-ethyl-4,5,5-trifluoro-1,3-dioxolan-2-one, 4,4-difluoro-5-methyl-1,3-dioxolan-2-one, 4-fluoro-5-methyl-1,3-dioxolan-2-one, 4-fluoro-5-trifluoromethyl-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, and the like.

[0123] Among them, fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethylethylene carbonate (3,3,3-trifluoropropylene carbonate), and 2,2,3,3,3-pentafluoropropyl ethylene carbonate are more preferable as the fluorinated saturated cyclic carbonate.

[0124] The above-mentioned fluorinated unsaturated cyclic carbonate is a cyclic carbonate having an unsaturated bond and a fluorine atom, and a fluorinated ethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon double bond is preferred. Specifically, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4-fluoro-5-vinyl ethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4,4-difluoro-4-vinyl ethylene carbonate, 4,4-difluoro-4-allyl ethylene carbonate, 4-fluoro-4-vinyl ethylene carbonate, 4-fluoro-4,5-diallyl ethylene carbonate, 4,5-difluoro-4-vinyl ethylene carbonate, 4,5-difluoro-4,5-divinyl ethylene carbonate, 4,5-difluoro-4,5-diallyl ethylene carbonate, etc. may be mentioned.

[0125] The above-mentioned fluorinated cyclic carbonate may be used alone, or two or more thereof may be used in combination at any combination and ratio.

[0126] When the above-mentioned fluorinated cyclic carbonate is included, the content of the above-mentioned fluorinated cyclic carbonate is preferably 5 to 90% by volume, more preferably 10 to 60% by volume, and still more preferably 15 to 45% by volume with respect to the above-mentioned solvent.

[0127] The above-mentioned chain carbonate may be a non-fluorinated chain carbonate or a fluorinated chain carbonate.

[0128] Examples of the non-fluorinated chain carbonate include hydrocarbon chain carbonates such as CH3OCOOCH3 (dimethyl carbonate: DMC), CH3CH2OCOOCH2CH3 (diethyl carbonate: DEC), CH3CH2OCOOCH3 (ethyl methyl carbonate: EMC), CH3OCOOCH2CH2CH3 (methyl propyl carbonate), methyl butyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl isopropyl carbonate, methyl-2-phenylphenyl carbonate, phenyl-2-phenylphenyl carbonate, trans-2,3-pentylene carbonate, trans-2,3-butylene carbonate, and ethyl phenyl carbonate. Among them, it is preferably at least one selected from the group consisting of ethyl methyl carbonate, diethyl carbonate, and dimethyl carbonate.

[0129] The above non-fluorinated chain carbonate may be used alone or in combination of two or more in any combination and ratio.

[0130] When the above non-fluorinated chain carbonate is included, the content of the non-fluorinated chain carbonate is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and still more preferably 50 to 80% by volume based on the above solvent.

[0131] The above fluorinated chain carbonate is a chain carbonate having a fluorine atom. A solvent containing a fluorinated chain carbonate can be preferably used even under high voltage.

[0132] Examples of the above fluorinated chain carbonate include the general formula (B): Rf 2 OCOOR 7 (B) (In the formula, Rf 2 is a fluorinated alkyl group having 1 to 7 carbon atoms, and R 7is an alkyl group which may contain fluorine atoms having 1 to 7 carbon atoms. Compounds represented by ) can be mentioned.

[0133] Rf 2 is a fluorinated alkyl group having 1 to 7 carbon atoms, and R 7 is an alkyl group which may contain fluorine atoms having 1 to 7 carbon atoms. The above fluorinated alkyl group is one in which at least one of the hydrogen atoms of the alkyl group is replaced with a fluorine atom. When R 7 is an alkyl group containing a fluorine atom, it becomes a fluorinated alkyl group. Rf 2 and R 7 are preferably those having 1 to 7 carbon atoms and more preferably 1 to 2 carbon atoms in that they have low viscosity. If the number of carbon atoms is too large, the low-temperature characteristics may deteriorate or the solubility of the electrolyte salt may decrease. If the number of carbon atoms is too small, a decrease in the solubility of the electrolyte salt, a decrease in discharge efficiency, or an increase in viscosity may be observed.

[0134] Examples of the fluorinated alkyl group having 1 carbon atom include CFH2-, CF2H-, CF3-, etc. In particular, CFH2- or CF3- is preferable in terms of high-temperature storage characteristics.

[0135] Examples of the fluorinated alkyl group having 2 or more carbon atoms include the following general formula (d-1): R d1 -R d2 - (d-1) (In the formula, R d1 is an alkyl group having 1 or more carbon atoms which may have a fluorine atom; R d2 is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; provided that at least one of R d1 and R d2 has a fluorine atom) can be preferably exemplified in terms of good solubility of the electrolyte salt. In addition, R d1 and R d2 may further have other atoms other than carbon atoms, hydrogen atoms, and fluorine atoms.

[0136] R d1 is an alkyl group having 1 or more carbon atoms which may have a fluorine atom. R d1 is preferably a linear or branched alkyl group having 1 to 6 carbon atoms. R d1 More preferably, the number of carbon atoms is 1 to 3.

[0137] R d1 Specifically, as the linear or branched alkyl group, CH3-, CF3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-,

[0138] [Chemical formula]

[0139] etc. can be mentioned.

[0140] Also, R d1When it is a linear alkyl group having a fluorine atom, examples include CF3-, CF3CH2-, CF3CF2-, CF3CH2CH2-, CF3CF2CH2-, CF3CF2CF2-, CF3CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2-, CF3CH2CF2CH2-, CF3CF2CF2CH2-, CF3CF2CF2CF2-, CF3CF2CH2CF2-, CF3CH2CH2CH2CH2-, CF3CF2CH2CH2CH2-, CF3CH2CF2CH2CH2-, CF3CF2CF2CH2CH2-, CF3CF2CF2CF2CH2-, CF3CF2CH2CF2CH2-, CF3CF2CH2CH2CH2CH2-, CF3CF2CF2CF2CH2CH2-, CF3CF2CH2CF2CH2CH2-, HCF2-, HCF2CH2-, HCF2CF2-, HCF2CH2CH2-, HCF2CF2CH2-, HCF2CH2CF2-, HCF2CF2CH2CH2-, HCF2CH2CF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CH2CH2CH2-, HCF2CH2CF2CH2CH2-, HCF2CF2CF2CF2CH2-, HCF2CF2CF2CF2CH2CH2-, FCH2-, FCH2CH2-, FCH2CF2-, FCH2CF2CH2-, FCH2CF2CF2-, CH3CF2CH2-, CH3CF2CF2-, CH3CF2CH2CF2-, CH3CF2CF2CF2-, CH3CH2CF2CF2-, CH3CF2CH2CF2CH2-, CH3CF2CF2CF2CH2-, CH3CF2CF2CH2CH2-, CH3CH2CF2CF2CH2-, CH3CF2CH2CF2CH2CH2-, CH3CF2CH2CF2CH2CH2-, HCFClCF2CH2-, HCF2CFClCH2-, HCF2CFClCF2CFClCH2-, HCFClCF2CFClCF2CH2-, etc.

[0141] Also, R d1 When it is a branched alkyl group having a fluorine atom,

[0142]

Chemical formula

[0143]

Chem.

[0144] etc. are preferably mentioned. However, since having a branch such as CH3- or CF3- tends to increase the viscosity, the number thereof is preferably small (1) or zero.

[0145] R d2 is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom. R d2 may be linear or branched. An example of the minimum structural unit constituting such a linear or branched alkylene group is shown below. R d2 is composed of these alone or in combination.

[0146] (i) Linear minimum structural unit: -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2-

[0147] (ii) Branched minimum structural unit:

[0148]

Chem.

[0149] Among the above examples, since the dehydrochlorination reaction by a base does not occur and it is more stable, it is preferably composed of structural units not containing Cl.

[0150] R d2 When it is linear, it consists only of the above-mentioned linear minimum structural units, and among them, -CH2-, -CH2CH2- or -CF2- is preferable. From the viewpoint of further improving the solubility of the electrolyte salt, -CH2- or -CH2CH2- is more preferable.

[0151] R d2When it is branched-chain, it comprises at least one of the above-described branched-chain minimum structural units, and is preferably exemplified by those represented by the general formula -(CX a X b )-(X a is H, F, CH3 or CF3; X b is CH3 or CF3. However, when X b is CF3, X a is H or CH3). These can further improve the solubility of the electrolyte salt in particular.

[0152] Specific examples of preferred fluorinated alkyl groups include, for example, CF3CF2-, HCF2CF2-, H2CFCF2-, CH3CF2-, CF3CH2-, CF3CF2CF2-, HCF2CF2CF2-, H2CFCF2CF2-, CH3CF2CF2-,

[0153]

Chem.

[0154]

Chem.

[0155] and the like.

[0156] Among them, as the fluorinated alkyl groups of Rf 2 and R 7 , CF3-, CF3CF2-, (CF3)2CH-, CF3CH2-, C2F5CH2-, CF3CF2CH2-, HCF2CF2CH2-, CF3CFHCF2CH2-, CFH2-, CF2H- are preferred, and from the viewpoints of high flame retardancy, good rate characteristics and oxidation resistance, CF3CH2-, CF3CF2CH2-, HCF2CF2CH2-, CFH2-, CF2H- are more preferred.

[0157] R 7 When it is an alkyl group not containing a fluorine atom, it is an alkyl group having 1 to 7 carbon atoms. R 7In terms of low viscosity, it preferably has 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms.

[0158] Examples of the alkyl group without a fluorine atom include CH3-, CH3CH2-, (CH3)2CH-, C3H7-, etc. Among them, CH3- and CH3CH2- are preferred in terms of low viscosity and good rate characteristics.

[0159] The fluorinated chain carbonate preferably has a fluorine content of 15 to 70% by mass. When the fluorine content is within the above range, the compatibility with the solvent and the solubility of the salt can be maintained. The above fluorine content is more preferably 20% by mass or more, still more preferably 30% by mass or more, particularly preferably 35% by mass or more, more preferably 60% by mass or less, and still more preferably 50% by mass or less. In the present disclosure, the fluorine content is based on the structural formula of the above fluorinated chain carbonate, {(number of fluorine atoms × 19) / molecular weight of fluorinated chain carbonate} × 100 (%) which is the value calculated by.

[0160] The fluorinated chain carbonate is preferably any of the following compounds in terms of low viscosity.

[0161]

Chemical formula

[0162] As the above fluorinated chain carbonate, methyl 2,2,2-trifluoroethyl carbonate (F3CH2COC(=O)OCH3) is particularly preferred.

[0163] The above fluorinated chain carbonate may be used alone or in combination of two or more in any combination and ratio.

[0164] When the fluorinated chain carbonate is included, the content of the fluorinated chain carbonate is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and still more preferably 50 to 80% by volume with respect to the solvent.

[0165] The carboxylic acid ester may be a cyclic carboxylic acid ester or a chain carboxylic acid ester.

[0166] The cyclic carboxylic acid ester may be a non-fluorinated cyclic carboxylic acid ester or a fluorinated cyclic carboxylic acid ester.

[0167] Examples of the non-fluorinated cyclic carboxylic acid ester include non-fluorinated saturated cyclic carboxylic acid esters, and non-fluorinated saturated cyclic carboxylic acid esters having an alkylene group having 2 to 4 carbon atoms are preferred.

[0168] Specific examples of the non-fluorinated saturated cyclic carboxylic acid ester having an alkylene group having 2 to 4 carbon atoms include β-propiolactone, γ-butyrolactone, ε-caprolactone, δ-valerolactone, and α-methyl-γ-butyrolactone. Among them, γ-butyrolactone and δ-valerolactone are particularly preferred in terms of improving the lithium ion dissociation degree and load characteristics.

[0169] The non-fluorinated saturated cyclic carboxylic acid ester may be used alone or in combination of two or more in any combination and ratio.

[0170] When the non-fluorinated saturated cyclic carboxylic acid ester is included, the content of the non-fluorinated saturated cyclic carboxylic acid ester is preferably 0 to 90% by volume, more preferably 0.001 to 90% by volume, still more preferably 1 to 60% by volume, and particularly preferably 5 to 40% by volume with respect to the solvent.

[0171] The above-mentioned chain carboxylic acid ester may be a non-fluorinated chain carboxylic acid ester or a fluorinated chain carboxylic acid ester. When the above-mentioned solvent contains the above-mentioned chain carboxylic acid ester, an increase in resistance after high-temperature storage of the electrolytic solution can be further suppressed.

[0172] Examples of the non-fluorinated chain carboxylic acid ester include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, tert-butyl propionate, tert-butyl butyrate, sec-butyl propionate, sec-butyl butyrate, n-butyl butyrate, methyl pyrophosphate, ethyl pyrophosphate, tert-butyl formate, tert-butyl acetate, sec-butyl formate, sec-butyl acetate, n-hexyl pivalate, n-propyl formate, n-propyl acetate, n-butyl formate, n-butyl pivalate, n-octyl pivalate, ethyl 2-(dimethoxyphosphoryl)acetate, ethyl 2-(dimethylphosphoryl)acetate, ethyl 2-(diethoxyphosphoryl)acetate, ethyl 2-(diethylphosphoryl)acetate, isopropyl propionate, isopropyl acetate, ethyl formate, ethyl 2-propynyl oxalate, isopropyl formate, isopropyl butyrate, isobutyl formate, isobutyl propionate, isobutyl butyrate, isobutyl acetate, and the like.

[0173] Among them, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate are preferable, and ethyl propionate and propyl propionate are particularly preferable.

[0174] The above-mentioned non-fluorinated chain carboxylic acid ester may be used alone or in combination of two or more in any combination and ratio.

[0175] When the non-fluorinated chain carboxylic acid ester is included, the content of the non-fluorinated chain carboxylic acid ester is preferably 0 to 90% by volume, more preferably 0.001 to 90% by volume, still more preferably 1 to 60% by volume, and particularly preferably 5 to 40% by volume with respect to the solvent.

[0176] The fluorinated chain carboxylic acid ester is a chain carboxylic acid ester having a fluorine atom. A solvent containing the fluorinated chain carboxylic acid ester can be suitably used even under a high voltage.

[0177] Examples of the fluorinated chain carboxylic acid ester include the following general formula: R 31 COOR 32 (In the formula, R 31 and R 32 are each independently an alkyl group which may contain a fluorine atom having 1 to 4 carbon atoms, and at least one of R 31 and R 32 contains a fluorine atom.) The fluorinated chain carboxylic acid ester represented by the formula is preferable in terms of good compatibility with other solvents and oxidation resistance.

[0178] R 31 and R 32Examples include non-fluorinated alkyl groups such as methyl group (-CH3), ethyl group (-CH2CH3), propyl group (-CH2CH2CH3), isopropyl group (-CH(CH3)2), normal butyl group (-CH2CH2CH2CH3), tertiary butyl group (-C(CH3)3); -CF3, -CF2H, -CFH2, -CF2CF3, -CF2CF2H, -CF2CFH2, -CH2CF3, -CH2CF2H, -CH2CFH2, -CF2CF2CF3, -CF2CF2CF2H, -CF2CF2CFH2, -CH2CF2CF3, -CH2CF2CF2H, -CH2CF2CFH2, -CH2CH2CF3, -CH2CH2CF2H, -CH2CH2CFH2, -CF(CF3)2, -CF(CF2H)2, -CF(CFH2)2, -CH(CF3)2, -CH(CF2H)2, -CH(CFH2)2, -CF(OCH3)CF3, -CF2CF2CF2CF3, -CF2CF2CF2CF2H, -CF2CF2CF2CFH2, -CH2CF2CF2CF3, -CH2CF2CF2CF2H, -CH2CF2CF2CFH2, -CH2CH2CF2CF3, -CH2CH2CF2CF2H, -CH2CH2CF2CFH2, -CH2CH2CH2CF3, -CH2CH2CH2CF2H, -CH2CH2CH2CFH2, -CF(CF3)CF2CF3, -CF(CF2H)CF2CF3, -CF(CFH2)CF2CF3, -CF(CF3)CF2CF2H, -CF(CF3)CF2CFH2, -CF(CF3)CH2CF3, -CF(CF3)CH2CF2H, -CF(CF3)CH2CFH2, -CH(CF3)CF2CF3, -CH(CF2H)CF2CF3, -CH(CFH2)CF2CF3, -CH(CF3)CF2CF2H, -CH(CF3)CF2CFH2, -CH(CF3)CH2CF3, -CH(CF3)CH2CF2H, -CH(CF3)CH2CFH2, -CF2CF(CF3)CF3, -CF2CF(CF2H)CF3, -CF2CF(CFH2)CF3, -CF2CF(CF3)CF2H, -CF2CF(CF3)CFH2, -CH2CF(CF3)CF3, -CH2CF(CF2H)CF3, -CH2CF(CFH2)CF3, -CH2CF(CF3)CF2H, -CH2CF(CF3)CFH2, -CH2CH(CF3)CF3, -CH2CH(CF2H)CF3,Examples of the fluorinated alkyl group include -CH2CH(CFH2)CF3, -CH2CH(CF3)CF2H, -CH2CH(CF3)CFH2, -CF2CH(CF3)CF3, -CF2CH(CF2H)CF3, -CF2CH(CFH2)CF3, -CF2CH(CF3)CF2H, -CF2CH(CF3)CFH2, -C(CF3)3, -C(CF2H)3, -C(CFH2)3, and the like. Among them, a methyl group, an ethyl group, -CF3, -CF2H, -CF2CF3, -CH2CF3, -CH2CF2H, -CH2CFH2, -CH2CH2CF3, -CH2CF2CF3, -CH2CF2CF2H, -CH2CF2CFH2 are particularly preferred because of their good compatibility with other solvents, viscosity, and oxidation resistance.

[0179] Specific examples of the fluorinated chain carboxylic acid ester include, for example, CF3CH2C(=O)OCH3 (methyl 3,3,3-trifluoropropionate), HCF2C(=O)OCH3 (methyl difluoroacetate), HCF2C(=O)OC2H5 (ethyl difluoroacetate), CF3C(=O)OCH2CH2CF3, CF3C(=O)OCH2C2F5, CF3C(=O)OCH2CF2CF2H (2,2,3,3-tetrafluoropropyl trifluoroacetate), CF3C(=O)OCH2CF3, CF3C(=O)OCH(CF3)2, ethyl pentafluorobutyrate, methyl pentafluoropropionate, ethyl pentafluoropropionate, methyl heptafluoroisobutyrate, isopropyl trifluorobutyrate, ethyl trifluoroacetate, tert-butyl trifluoroacetate, n-butyl trifluoroacetate, methyl tetrafluoro-2-(methoxy)propionate, 2,2-difluoroethyl acetate, 2,2,3,3-tetrafluoropropyl acetate, CH3C(=O)OCH2CF3 (2,2,2-trifluoroethyl acetate), 1H,1H-heptafluorobutyl acetate, methyl 4,4,4-trifluorobutyrate, ethyl 4,4,4-trifluorobutyrate, ethyl 3,3,3-trifluoropropionate, 3,3,3-trifluoropropyl 3,3,3-trifluoropropionate, ethyl 3-(trifluoromethyl)butyrate, methyl 2,3,3,3-tetrafluoropropionate, butyl 2,2-difluoroacetate, methyl 2,2,3,3-tetrafluoropropionate, methyl 2-(trifluoromethyl)-3,3,3-trifluoropropionate, methyl heptafluorobutyrate, and the like, and one or more of these can be exemplified. Among them, CF3CH2C(=O)OCH3, HCF2C(=O)OCH3, HCF2C(=O)OC2H5, CF3C(=O)OCH2C2F5, CF3C(=O)OCH2CF2CF2H, CF3C(=O)OCH2CF3, CF3C(=O)OCH(CF3)2, ethyl pentafluorobutyrate, methyl pentafluoropropionate, ethyl pentafluoropropionate, methyl heptafluoroisobutyrate, isopropyl trifluorobutyrate, ethyl trifluoroacetate, tert-butyl trifluoroacetate, n-butyl trifluoroacetate, methyl tetrafluoro-2-(methoxy)propionate, 2,2-difluoroethyl acetate, 2,2,3,3-tetrafluoropropyl acetate, CH3C(=O)OCH2CF3, 1H,1H-heptafluorobutyl acetate, methyl 4,4,4-trifluorobutyrate, ethyl 4,4,4-trifluorobutyrate, ethyl 3,3,3-trifluoropropionate, 3,3,3-trifluoropropyl 3,3,3-trifluoropropionate, ethyl 3-(trifluoromethyl)butyrate, methyl 2,3,3,3-tetrafluoropropionate, butyl 2,2-difluoroacetate, methyl 2,2,3,3-tetrafluoropropionate, methyl 2-(trifluoromethyl)-3,3,3-trifluoropropionate, methyl heptafluorobutyrate are preferable because of their good compatibility with other solvents and rate characteristics. CF3CH2C(=O)OCH3, HCF2C(=O)OCH3, HCF2C(=O)OC2H5, CH3C(=O)OCH2CF3 are more preferable, and HCF2C(=O)OCH3, HCF2C(=O)OC2H5, CH3C(=O)OCH2CF3 are particularly preferable.

[0180] The above fluorinated chain carboxylic acid ester may be used alone or in combination of two or more in any combination and ratio.

[0181] When the above fluorinated chain carboxylic acid ester is included, the content of the above fluorinated chain carboxylic acid ester is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and still more preferably 50 to 80% by volume based on the above solvent.

[0182] Preferably, the solvent contains at least one selected from the group consisting of the cyclic carbonate, the linear carbonate, and the linear carboxylic acid ester. More preferably, the solvent contains the cyclic carbonate and at least one selected from the group consisting of the linear carbonate and the linear carboxylic acid ester. The cyclic carbonate is preferably a saturated cyclic carbonate. The electrolyte containing the solvent having the above composition can further improve the high-temperature storage characteristics and cycle characteristics of the electrochemical device.

[0183] When the solvent contains the cyclic carbonate and at least one selected from the group consisting of the linear carbonate and the linear carboxylic acid ester, it is preferable that the total amount of the cyclic carbonate and at least one selected from the group consisting of the linear carbonate and the linear carboxylic acid ester is 10 to 100% by volume, more preferably 30 to 100% by volume, and still more preferably 50 to 100% by volume.

[0184] When the solvent contains the cyclic carbonate and at least one selected from the group consisting of the linear carbonate and the linear carboxylic acid ester, the volume ratio of the cyclic carbonate to at least one selected from the group consisting of the linear carbonate and the linear carboxylic acid ester is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 or more, still more preferably 15 / 85 or more, particularly preferably 20 / 80 or more, more preferably 90 / 10 or less, still more preferably 60 / 40 or less, and particularly preferably 50 / 50 or less.

[0185] The above solvent preferably also contains at least one selected from the group consisting of the above non-fluorinated saturated cyclic carbonate, the above non-fluorinated chain carbonate, and the above non-fluorinated chain carboxylic acid ester. More preferably, it contains the above non-fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the above non-fluorinated chain carbonate and the above non-fluorinated chain carboxylic acid ester. The electrolyte containing the solvent of the above composition can be suitably used for an electrochemical device used at a relatively low voltage.

[0186] When the above solvent contains the above non-fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the above non-fluorinated chain carbonate and the above non-fluorinated chain carboxylic acid ester, it is preferable that the total of the above non-fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the above non-fluorinated chain carbonate and the above non-fluorinated chain carboxylic acid ester is 5 to 100% by volume, more preferably 20 to 100% by volume, and still more preferably 30 to 100% by volume.

[0187] When the above electrolyte contains the above non-fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the above non-fluorinated chain carbonate and the above non-fluorinated chain carboxylic acid ester, the volume ratio of the above non-fluorinated saturated cyclic carbonate to at least one selected from the group consisting of the above non-fluorinated chain carbonate and the above non-fluorinated chain carboxylic acid ester is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 or more, still more preferably 15 / 85 or more, particularly preferably 20 / 80 or more, more preferably 90 / 10 or less, still more preferably 60 / 40 or less, and particularly preferably 50 / 50 or less.

[0188] The above solvent preferably also contains at least one selected from the group consisting of the above fluorinated saturated cyclic carbonate, the above fluorinated linear carbonate, and the above fluorinated linear carboxylic acid ester. More preferably, it contains the above fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the above fluorinated linear carbonate and the above fluorinated linear carboxylic acid ester. The electrolyte containing the solvent of the above composition can be suitably used not only for electrochemical devices used at relatively low voltages but also for electrochemical devices used at relatively high voltages.

[0189] When the above solvent contains the above fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the above fluorinated linear carbonate and the above fluorinated linear carboxylic acid ester, it is preferable that the total of the above fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the above fluorinated linear carbonate and the above fluorinated linear carboxylic acid ester is 5 to 100% by volume, more preferably 10 to 100% by volume, and still more preferably 30 to 100% by volume.

[0190] When the above solvent contains the above fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the above fluorinated linear carbonate and the above fluorinated linear carboxylic acid ester, the volume ratio of the above fluorinated saturated cyclic carbonate to at least one selected from the group consisting of the above fluorinated linear carbonate and the above fluorinated linear carboxylic acid ester is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 or more, still more preferably 15 / 85 or more, particularly preferably 20 / 80 or more, more preferably 90 / 10 or less, still more preferably 60 / 40 or less, and particularly preferably 50 / 50 or less.

[0191] Also, an ionic liquid can be used as the above solvent. An "ionic liquid" is a liquid composed of ions formed by combining an organic cation and an anion.

[0192] The organic cation is not particularly limited, and examples thereof include imidazolium ions such as dialkylimidazolium cations and trialkylimidazolium cations; tetraalkylammonium ions; alkylpyridinium ions; dialkylpyrrolidinium ions; and dialkylpiperidinium ions.

[0193] The anion that serves as the counterion for these organic cations is not particularly limited, and examples thereof include PF6 anion, PF3(C2F5)3 anion, PF3(CF3)3 anion, BF4 anion, BF2(CF3)2 anion, BF3(CF3) anion, bisoxalatoborate anion, P(C2O4)F2 anion, Tf (trifluoromethanesulfonyl) anion, Nf (nonafluorobutanesulfonyl) anion, bis(fluorosulfonyl)imide anion, bis(trifluoromethanesulfonyl)imide anion, bis(pentafluoroethanesulfonyl)imide anion, dicyanoamine anion, and halide anions.

[0194] The above solvent is preferably a non-aqueous solvent, and the electrolyte solution of the present disclosure is preferably a non-aqueous electrolyte solution. The content of the above solvent is preferably 70 to 99.999% by mass in the electrolyte solution, more preferably 80% by mass or more, and more preferably 92% by mass or less.

[0195] The electrolyte solution of the present disclosure preferably contains an electrolyte salt. Lithium bis(fluorosulfonyl)imide can be used as the electrolyte salt, but it is preferable to further contain an electrolyte salt other than lithium bis(fluorosulfonyl)imide in that the resistance value at low temperatures can be further reduced. As the above electrolyte salt, any of those that can be used in an electrolyte solution can be used, such as lithium salts, ammonium salts, metal salts, liquid salts (ionic liquids), inorganic polymer salts, and organic polymer salts.

[0196] As the electrolyte salt for the electrolyte of the lithium-ion secondary battery, a lithium salt (excluding lithium bis(fluorosulfonyl)imide) is preferred. Any of the above lithium salts can be used, and specifically, the following can be mentioned. For example, LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, LiTaF6, LiWF7, LiAsF6, LiAlCl4, LiI, LiBr, LiCl, LiB 10 Cl 10 , inorganic lithium salts such as Li2SiF6, Li2PFO3, LiPO2F2; Lithium tungstates such as LiWOF5; Lithium carboxylate salts such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, CF3CF2CF2CF2CO2Li; Lithium salts having an S=O group such as FSO3Li, CH3SO3Li, CH2FSO3Li, CHF2SO3Li, CF3SO3Li, CF3CF2SO3Li, CF3CF2CF2SO3Li, CF3CF2CF2CF2SO3Li, lithium methyl sulfate, lithium ethyl sulfate (C2H5OSO3Li), lithium 2,2,2-trifluoroethyl sulfate; Lithium imide salts such as LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium bisperfluoroethanesulfonylimide, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, lithium cyclic 1,2-ethanedisulfonylimide, lithium cyclic 1,3-propanedisulfonylimide, lithium cyclic 1,4-perfluorobutanedisulfonylimide, LiN(CF3SO2)(FSO2), LiN(CF3SO2)(C3F7SO2), LiN(CF3SO2)(C4F9SO2), LiN(POF2)2; Lithium methide salts such as LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3; In addition, salts represented by the formula: LiPF a (C n F 2n+1 ) 6-a (wherein a is an integer from 0 to 5 and n is an integer from 1 to 6), such as LiPF3(C2F5)3, LiPF3(CF3)3, LiPF3(iso-C3F7)3, LiPF5(iso-C3F7), LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF3CF3, LiBF3C2F5, LiBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2 and other fluorine-containing organic lithium salts, LiSCN, LiB(CN)4, LiB(C6H5)4, Li2(C2O4), LiP(C2O4)3, Li2B 12 F b H 12-b (b is an integer from 0 to 3), etc. can be mentioned.

[0197] Among them, LiPF6, LiBF4, LiSbF6, LiTaF6, LiPO2F2, FSO3Li, CF3SO3Li, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, etc. are particularly preferred in terms of having effects such as improving output characteristics, high-rate charge and discharge characteristics, high-temperature storage characteristics, cycle characteristics, etc., and at least one lithium salt selected from the group consisting of LiPF6 and LiBF4 is most preferred. LiPF6 is particularly preferred in terms of being able to further reduce the resistance value at low temperatures.

[0198] The content of the lithium salt (excluding lithium bis(fluorosulfonyl)imide) is preferably 0.01 to 8 M (mol / L) with respect to the above electrolyte solution. In terms of reducing the resistance value at low temperatures, the content of the lithium salt (excluding lithium bis(fluorosulfonyl)imide) is more preferably 0.05 M or more, still more preferably 0.10 M or more, even more preferably 0.15 M or more, particularly preferably 0.20 M or more, especially preferably 0.50 M or more with respect to the above electrolyte solution. Also, it is more preferably 5 M or less, still more preferably 3 M or less, even more preferably 2 M or less, particularly preferably 1 M or less.

[0199] When the electrolyte solution of the present disclosure contains LiPF6, the molar ratio (LiPF6 / LiFSI) of LiPF6 to lithium bis(fluorosulfonyl)imide (LiFSI) is preferably 1 / 99 or more, more preferably 10 / 90 or more, still more preferably 30 / 70 or more, even more preferably 50 / 50 or more, even more preferably 60 / 40 or more in terms of further reducing the resistance value at low temperatures. Also, it is preferably 99 / 1 or less, more preferably 90 / 10 or less, still more preferably 85 / 15 or less, even more preferably 80 / 20 or less.

[0200] These electrolyte salts may be used alone or in combination of two or more. A preferred example of using two or more in combination is the combination of LiPF6 and LiBF4, or the combination of LiPF6 and LiPO2F2, C2H5OSO3Li or FSO3Li, which has the effect of improving the high-temperature storage characteristics, load characteristics and cycle characteristics.

[0201] In this case, there is no limitation on the blending amount of LiBF4, LiPO2F2, C2H5OSO3Li or FSO3Li with respect to 100% by mass of the entire electrolyte solution, and it is arbitrary as long as the effects of the present disclosure are not significantly impaired. However, with respect to the electrolyte solution of the present disclosure, it is usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less.

[0202] Another example is the combined use of an inorganic lithium salt and an organic lithium salt. The combined use of both has the effect of suppressing deterioration due to high-temperature storage. Preferred organic lithium salts include CF3SO3Li, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, etc. In this case, the proportion of the organic lithium salt with respect to 100% by mass of the entire electrolytic solution is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and is preferably 30% by mass or less, particularly preferably 20% by mass or less.

[0203] The concentration of these electrolyte salts in the electrolytic solution is not particularly limited as long as the effects of the present disclosure are not impaired. From the viewpoint of keeping the electrical conductivity of the electrolytic solution within a good range and ensuring good battery performance, the total molar concentration of lithium in the electrolytic solution is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, still more preferably 0.5 mol / L or more, and is preferably 3 mol / L or less, more preferably 2.5 mol / L or less, still more preferably 2.0 mol / L or less.

[0204] If the total molar concentration of lithium is too low, the electrical conductivity of the electrolytic solution may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity, and the battery performance may decrease.

[0205] As the electrolyte salt for the electrolytic solution of the electric double layer capacitor, an ammonium salt is preferred. Examples of the above ammonium salt include the following (IIa) to (IIe). (IIa) Tetraalkyl quaternary ammonium salt General formula (IIa):

[0206] [Chemical] (wherein, R 1a , R 2a , R 3a and R 4a are the same or different and each may be an alkyl group which may contain an ether bond having 1 to 6 carbon atoms; X - is an anion) The tetraalkyl quaternary ammonium salt represented by can be preferably exemplified. Further, those in which some or all of the hydrogen atoms of this ammonium salt are substituted with fluorine atoms and / or fluorine-containing alkyl groups having 1 to 4 carbon atoms are also preferable from the viewpoint of improving oxidation resistance.

[0207] As a specific example, general formula (IIa-1):

[0208] [Chemical] (wherein, R 1a , R 2a and X - is an anion; x and y are the same or different and are integers of 0 to 4, and x + y = 4) The tetraalkyl quaternary ammonium salt represented by, general formula (IIa-2):

[0209] [Chemical] (wherein, R 5a is an alkyl group having 1 to 6 carbon atoms; R 6a is a divalent hydrocarbon group having 1 to 6 carbon atoms; R 7a is an alkyl group having 1 to 4 carbon atoms; z is 1 or 2; X - is an anion) The alkyl ether group-containing trialkyl ammonium salt represented by, etc. can be mentioned. By introducing an alkyl ether group, a decrease in viscosity can be achieved.

[0210] The anion X - may be an inorganic anion or an organic anion. Examples of the inorganic anion include, for example, AlCl4 - , BF4- , PF6 - , AsF6 - , TaF6 - , I - , SbF6 - include. As organic anions, for example, bisoxalatoborate anion, difluorooxalatoborate anion, tetrafluorooxalatophosphate anion, difluorobisoxalatophosphate anion, CF3COO - , CF3SO3 - , (CF3SO2)2N - , (C2F5SO2)2N - etc. can be mentioned.

[0211] Among these, BF4 - , PF6 - , AsF6 - , SbF6 - are preferred.

[0212] Suitable specific examples of tetraalkyl quaternary ammonium salts include Et4NBF4, Et4NClO4, Et4NPF6, Et4NAsF6, Et4NSbF6, Et4NCF3SO3, Et4N(CF3SO2)2N, Et4NC4F9SO3, Et3MeNBF4, Et3MeNClO4, Et3MeNPF6, Et3MeNAsF6, Et3MeNSbF6, Et3MeNCF3SO3, Et3MeN(CF3SO2)2N, Et3MeNC4F9SO3, and in particular, Et4NBF4, Et4NPF6, Et4NSbF6, Et4NAsF6, Et3MeNBF4, N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium salts, etc. can be mentioned.

[0213] (IIb) Spirocyclic bipyrrolidinium salt General formula (IIb-1):

[0214] [Chemical formula] (In the formula, R 8a and R 9aare the same or different and are each an alkyl group having 1 to 4 carbon atoms; X - is an anion; n1 is an integer of 0 to 5; n2 is an integer of 0 to 5) a spiro ring bipyrrolidinium salt represented by the formula: General formula (IIb-2):

[0215] [Chemical formula] (In the formula, R 10a and R 11a are the same or different and are each an alkyl group having 1 to 4 carbon atoms; X - is an anion; n3 is an integer of 0 to 5; n4 is an integer of 0 to 5) a spiro ring bipyrrolidinium salt represented by the formula, or general formula (IIb-3):

[0216] [Chemical formula] (In the formula, R 12a and R 13a are the same or different and are each an alkyl group having 1 to 4 carbon atoms; X - is an anion; n5 is an integer of 0 to 5; n6 is an integer of 0 to 5) Preferred examples of the spiro ring bipyrrolidinium salt include those in which some or all of the hydrogen atoms of the spiro ring bipyrrolidinium salt are substituted with fluorine atoms and / or fluorine-containing alkyl groups having 1 to 4 carbon atoms, which are also preferred from the viewpoint of improved oxidation resistance.

[0217] For the anion X - preferred specific examples are the same as in the case of (IIa). Among them, BF4−, PF6−, (CF3SO2)2N− or (C2F5SO2)2N− are preferred from the viewpoint of high dissociation property and low internal resistance under high voltage.

[0218] Preferred specific examples of the spiro ring bipyrrolidinium salt include, for example, [Chemical formula] and the like.

[0219] This spirocyclic bipyrrolidinium salt is excellent in terms of solubility in solvents, oxidation resistance, and ionic conductivity.

[0220] (IIc) Imidazolium salt General formula (IIc):

[0221]

Chemical formula

[0222] Preferred specific examples of the anion X - are the same as those in (IIa).

[0223] Preferred specific examples include, for example

[0224]

Chemical formula

[0225] This imidazolium salt is excellent in that it has low viscosity and good solubility.

[0226] (IId): N-alkylpyridinium salt General formula (IId):

[0227]

Chemical formula

[0228] Anion X - The preferable specific examples are the same as those of (IIa).

[0229] Preferable specific examples include, for example

[0230]

Chemical formula

[0231] This N-alkylpyridinium salt is excellent in that it has low viscosity and good solubility.

[0232] (IIe) N,N-dialkylpyrrolidinium salt General formula (IIe):

[0233]

Chemical formula

[0234] Anion X - The preferable specific examples are the same as those of (IIa).

[0235] Preferable specific examples include, for example

[0236] [Chemical]

[0237] [Chemical] etc. can be mentioned.

[0238] This N,N-dialkylpyrrolidinium salt is excellent in that it has low viscosity and good solubility.

[0239] Among these ammonium salts, (IIa), (IIb), and (IIc) are preferable in terms of good solubility, oxidation resistance, and ion conductivity. Furthermore,

[0240] [Chemical] (wherein Me is a methyl group; Et is an ethyl group; X - , x, and y are the same as in formula (IIa-1)) is preferable.

[0241] Also, a lithium salt may be used as the electrolyte salt for the electric double layer capacitor. Examples of the lithium salt include LiPF6, LiBF4, LiAsF6, LiSbF6, and LiN(SO2C2H5)2. Furthermore, a magnesium salt may be used to further improve the capacitance. Examples of the magnesium salt include Mg(ClO4)2, Mg(OOC2H5)2, etc.

[0242] When the electrolyte salt is the above ammonium salt, the concentration is preferably 0.7 mol / L or more. If it is less than 0.7 mol / L, not only the low-temperature characteristics deteriorate, but also the initial internal resistance may increase. The concentration of the above electrolyte salt is more preferably 0.9 mol / L or more. In terms of low-temperature characteristics, the upper limit of the above concentration is preferably 2.0 mol / L or less, and more preferably 1.5 mol / L or less. When the ammonium salt is triethylmethylammonium tetrafluoroborate (TEMABF4), its concentration is preferably 0.7 to 1.5 mol / L in terms of excellent low-temperature characteristics. In the case of spirobipyrrolidinium tetrafluoroborate (SBPBF4), it is preferably 0.7 to 2.0 mol / L.

[0243] The electrolyte of the present disclosure has the general formula (2):

Chemical formula

[0244] When n21 is 2 or 3, the two or three Xs 21 may be the same or different. Y 21 and Z 21 When there are a plurality of Ys 21 and Zs 21 present, the plurality of Ys 21 and Zs 21 may be the same or different.

[0245] X 21 is preferably a group represented by -CY 21 Z 21 -(wherein Y 21 and Z 21 are as described above) or -CY 21 =CZ 21 -(wherein Y 21 and Z 21 are as described above).

[0246] Y 21As for this, at least one selected from the group consisting of H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2- is preferable. Z 21 As for this, at least one selected from the group consisting of H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2- is preferable.

[0247] Or, Y 21 And Z 21 may be bonded to each other to form a carbocyclic ring or a heterocyclic ring which may contain an unsaturated bond and may have aromaticity. The number of carbon atoms in the ring is preferably 3 to 20.

[0248] Next, specific examples of the compound (2) will be described. In the following examples, the "analog" refers to an acid anhydride obtained by replacing a part of the structure of the exemplified acid anhydride with another structure within a range not contrary to the spirit of the present disclosure. For example, dimers, trimers, tetramers, etc. composed of a plurality of acid anhydrides, or those having structural isomerism such as having the same number of carbon atoms in the substituent but having a branched chain, those having different bonding sites of the substituent to the acid anhydride, etc. can be mentioned.

[0249] Specific examples of the acid anhydride forming a 5-membered ring structure include succinic anhydride, methylsuccinic anhydride (4-methylsuccinic anhydride), dimethylsuccinic anhydride (4,4-dimethylsuccinic anhydride, 4,5-dimethylsuccinic anhydride, etc.), 4,4,5-trimethylsuccinic anhydride, 4,4,5,5-tetramethylsuccinic anhydride, 4-vinylsuccinic anhydride, 4,5-divinylsuccinic anhydride, phenylsuccinic anhydride (4-phenylsuccinic anhydride), 4,5-diphenylsuccinic anhydride, 4,4-diphenylsuccinic anhydride, citraconic anhydride, maleic anhydride, methylmaleic anhydride (4-methylmaleic anhydride), 4,5-dimethylmaleic anhydride, phenylmaleic anhydride (4-phenylmaleic anhydride), 4,5-diphenylmaleic anhydride, itaconic anhydride, 5-methylitaconic anhydride, 5,5-dimethylitaconic anhydride, phthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, etc., and their analogs.

[0250] Specific examples of the acid anhydride forming a 6-membered ring structure include cyclohexanedicarboxylic anhydride (such as cyclohexane-1,2-dicarboxylic anhydride), 4-cyclohexene-1,2-dicarboxylic anhydride, glutaric anhydride, glutaconic anhydride, 2-phenylglutaric anhydride, etc., and their analogs.

[0251] Specific examples of the acid anhydride forming other cyclic structures include 5-norbornene-2,3-dicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, pyromellitic dianhydride, diglycolic anhydride, etc., and their analogs.

[0252] While forming a cyclic structure, specific examples of acid anhydrides substituted with halogen atoms include monofluoro succinic anhydride (such as 4-fluoro succinic anhydride), 4,4-difluoro succinic anhydride, 4,5-difluoro succinic anhydride, 4,4,5-trifluoro succinic anhydride, trifluoromethyl succinic anhydride, tetrafluoro succinic anhydride (4,4,5,5-tetrafluoro succinic anhydride), 4-fluoro maleic anhydride, 4,5-difluoro maleic anhydride, trifluoromethyl maleic anhydride, 5-fluoro itaconic anhydride, 5,5-difluoro itaconic anhydride, and the like, and their analogs, etc.

[0253] Among others, as the compound (2), glutaric anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, 4-cyclohexene-1,2-dicarboxylic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, phenyl succinic anhydride, 2-phenyl glutaric anhydride, maleic anhydride, methyl maleic anhydride, trifluoromethyl maleic anhydride, phenyl maleic anhydride, succinic anhydride, methyl succinic anhydride, dimethyl succinic anhydride, trifluoromethyl succinic anhydride, monofluoro succinic anhydride, tetrafluoro succinic anhydride, etc. are preferable, maleic anhydride, methyl maleic anhydride, trifluoromethyl maleic anhydride, succinic anhydride, methyl succinic anhydride, trifluoromethyl succinic anhydride, tetrafluoro succinic anhydride are more preferable, and maleic anhydride, succinic anhydride are even more preferable.

[0254] The compound (2) is represented by the general formula (3):

[0255]

Chemical formula

[0256] [Chem.] (wherein X 41 and X 42 are the same or different and are at least one selected from the group consisting of compounds (4) represented by a group containing at least H, C, O or F).

[0257] X 31 ~X 34 are preferably at least one selected from the group consisting of an alkyl group, a fluorinated alkyl group, an alkenyl group and a fluorinated alkenyl group, which are the same or different. The carbon number of X 31 ~X 34 is preferably from 1 to 10, more preferably from 1 to 3.

[0258] X 31 ~X 34 are more preferably at least one selected from the group consisting of H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2-, which are the same or different.

[0259] X 41 and X 42 are preferably at least one selected from the group consisting of an alkyl group, a fluorinated alkyl group, an alkenyl group and a fluorinated alkenyl group, which are the same or different. The carbon number of X 41 and X 42 is preferably from 1 to 10, more preferably from 1 to 3.

[0260] X 41 and X 42 are more preferably at least one selected from the group consisting of H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2-, which are the same or different.

[0261] Compound (3) is preferably any of the following compounds.

[0262] [Chemical formula]

[0263] Compound (4) is preferably any of the following compounds.

[0264] [Chemical formula]

[0265] Since the above electrolytic solution is less likely to have a decrease in the capacity retention rate and an increase in the amount of gas generated even when stored at a high temperature, it is preferable that the above electrolytic solution contains 0.0001 to 15% by mass of compound (2) with respect to the above electrolytic solution. As the content of compound (2), 0.01 to 10% by mass is more preferable, 0.1 to 3% by mass is still more preferable, and 0.1 to 1.0% by mass is particularly preferable.

[0266] When the above electrolytic solution contains both compound (3) and (4), since the capacity retention rate is less likely to decrease and the amount of gas generated is less likely to increase even when stored at a high temperature, the above electrolytic solution preferably contains 0.08 to 2.50% by mass of compound (3) and 0.02 to 1.50% by mass of compound (4) with respect to the above electrolytic solution, and more preferably contains 0.80 to 2.50% by mass of compound (3) and 0.08 to 1.50% by mass of compound (4).

[0267] The electrolytic solution of the present disclosure may contain at least one selected from the group consisting of nitrile compounds represented by the following general formulas (1a), (1b), and (1c). [Chemical formula] (In the formula, R a and R bEach independently represents a hydrogen atom, a cyano group (CN), a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of the alkyl group are substituted with halogen atoms. n represents an integer from 1 to 10.)

Chemical formula

Chemical formula

[0268] In the general formula (1a) above, R a and R bis, independently, a hydrogen atom, a cyano group (CN), a halogen atom, an alkyl group, or a group in which at least a part of hydrogen atoms of the alkyl group is substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among them, a fluorine atom is preferable. As the alkyl group, those having 1 to 5 carbon atoms are preferable. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and the like. Examples of the group in which at least a part of hydrogen atoms of the alkyl group is substituted with a halogen atom include a group in which at least a part of hydrogen atoms of the above-described alkyl group is substituted with the above-described halogen atom. R a and R b When is an alkyl group or a group in which at least a part of hydrogen atoms of the alkyl group is substituted with a halogen atom, R a and R b may be bonded to each other to form a ring structure (for example, a cyclohexane ring). R a and R b are preferably a hydrogen atom or an alkyl group.

[0269] In the above general formula (1a), n is an integer of 1 to 10. When n is 2 or more, all n R a may be the same, or at least a part thereof may be different. The same applies to R b . n is preferably an integer of 1 to 7, and more preferably an integer of 2 to 5.

[0270] As the nitrile compound represented by the above general formula (1a), dinitrile and tricarbonitrile are preferable. Specific examples of dinitriles include malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile, undecanedinitrile, dodecanedinitrile, methylmalononitrile, ethylmalononitrile, isopropylmalononitrile, tert-butylmalononitrile, methylsuccinonitrile, 2,2-dimethylsuccinonitrile, 2,3-dimethylsuccinonitrile, 2,3,3-trimethylsuccinonitrile, 2,2,3,3-tetramethylsuccinonitrile, 2,3-diethyl-2,3-dimethylsuccinonitrile, 2,2-diethyl-3,3-dimethylsuccinonitrile, bicyclohexyl-1,1-dicarbonitrile, bicyclohexyl-2,2-dicarbonitrile, bicyclohexyl-3,3-dicarbonitrile, 2,5-dimethyl-2,5-hexanedicarbonitrile, 2,3-diisobutyl-2,3-dimethylsuccinonitrile, 2,2-diisobutyl-3,3-dimethylsuccinonitrile, 2-methylglutaronitrile, 2,3-dimethylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,3,3-tetramethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 2,2,3,4-tetramethylglutaronitrile, 2,3,3,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,3'-(ethylenedioxy)dipropionitrile, 3,3'-(ethylenedithio)dipropionitrile, 3,9-bis(2-cyanoethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, butanenitrile, phthalonitrile, etc. Among these, succinonitrile, glutaronitrile, and adiponitrile are particularly preferred. In addition, specific examples of tricarbonitrile include pentane tricarbonitrile, propane tricarbonitrile, 1,3,5 - hexane tricarbonitrile, 1,3,6 - hexane tricarbonitrile, heptane tricarbonitrile, 1,2,3 - propane tricarbonitrile, 1,3,5 - pentane tricarbonitrile, cyclohexane tricarbonitrile, tris cyanoethylamine, tris cyanoethoxypropane, tricyanoethylene, tris(2 - cyanoethyl)amine, etc. Particularly preferred are 1,3,6 - hexane tricarbonitrile and cyclohexane tricarbonitrile, and the most preferred is cyclohexane tricarbonitrile.

[0271] In the above general formula (1b), R c represents a hydrogen atom, a halogen atom, an alkyl group, a group in which at least a part of the hydrogen atoms of the alkyl group are substituted with halogen atoms, or NC - R c1 -X c1 -(R c1 is an alkylene group, X c1 represents an oxygen atom or a sulfur atom. ), and R d and R e each independently represents a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of the alkyl group are substituted with halogen atoms. Examples of the halogen atom, alkyl group, and the group in which at least a part of the hydrogen atoms of the alkyl group are substituted with halogen atoms are the same as those exemplified for the above general formula (1a). In the above NC - R c1 -X c1 - in, R c1 is an alkylene group. As the alkylene group, an alkylene group having 1 to 3 carbon atoms is preferred. R c , R d and R e each independently preferably represents a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of the alkyl group are substituted with halogen atoms. R c , R d and R eAt least one of them is preferably a halogen atom or a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a halogen atom, more preferably a fluorine atom or a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a fluorine atom. R d and R e When is an alkyl group or a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a halogen atom, R d and R e may be bonded to each other to form a ring structure (for example, a cyclohexane ring).

[0272] In the above general formula (1b), m is an integer of 1 to 10. When m is 2 or more, all m R d may be the same or at least a part of them may be different. The same applies to R e . m is preferably an integer of 2 to 7, more preferably an integer of 2 to 5.

[0273] Examples of the nitrile compound represented by the above general formula (1b) include acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 3-methoxypropionitrile, 2-methylbutyronitrile, trimethylacetonitrile, hexanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-difluoropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3'-oxydipropionitrile, 3,3'-thiodipropionitrile, pentafluoropropionitrile, methoxyacetonitrile, benzonitrile and the like. Among these, 3,3,3-trifluoropropionitrile is particularly preferable.

[0274] In the above general formula (1c), Rf and R g and R h and R i and R are each independently a group containing a cyano group (CN), a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of the alkyl group is substituted with a halogen atom. Examples of the halogen atom, the alkyl group, and the group in which at least a part of the hydrogen atoms of the alkyl group is substituted with a halogen atom are those exemplified for the above general formula (1a). Examples of the group containing a cyano group include, in addition to the cyano group, a group in which at least a part of the hydrogen atoms of the alkyl group is substituted with a cyano group. Examples of the alkyl group in this case are those exemplified for the above general formula (1a). R f and R g and R h and R i and at least one of R is a group containing a cyano group. Preferably, at least two of R f and R g and R h and R i are groups containing a cyano group, and more preferably, R h and R i are groups containing a cyano group. When R h and R i are groups containing a cyano group, R f and R g are preferably hydrogen atoms.

[0275] In the above general formula (1c), l is an integer of 1 to 3. When l is 2 or more, all l R f may be the same, or at least a part thereof may be different. The same applies to R g . l is preferably an integer of 1 to 2.

[0276] Examples of the nitrile compound represented by the general formula (1c) include 3 - hexenedinitrile, mucononitrile, maleonitrile, fumaronitrile, acrylonitrile, methacrylonitrile, crotononitrile, 3 - methylcrotononitrile, 2 - methyl - 2 - butenenitrile, 2 - pentenenitrile, 2 - methyl - 2 - pentenenitrile, 3 - methyl - 2 - pentenenitrile, 2 - hexenenitrile, etc. Among them, 3 - hexenedinitrile and mucononitrile are preferred, and 3 - hexenedinitrile is particularly preferred.

[0277] The content of the above - mentioned nitrile compound is preferably 0.2 to 7% by mass based on the electrolytic solution. Thereby, the high - temperature storage characteristics and safety at high voltages of the electrochemical device can be further improved. The lower limit of the total content of the above - mentioned nitrile compound is more preferably 0.3% by mass, still more preferably 0.5% by mass. The upper limit is more preferably 5% by mass, still more preferably 2% by mass, and particularly preferably 0.5% by mass.

[0278] The electrolytic solution of the present disclosure may contain a compound having an isocyanato group (hereinafter, may be abbreviated as "isocyanate"). The above - mentioned isocyanate is not particularly limited, and any isocyanate can be used. Examples of the isocyanate include monoisocyanates, diisocyanates, triisocyanates, etc.

[0279] Specific examples of the monoisocyanates include isocyanatomethane, isocyanatoethane, 1-isocyanatopropane, 1-isocyanatobutane, 1-isocyanatopentane, 1-isocyanatohexane, 1-isocyanatoheptane, 1-isocyanatooctane, 1-isocyanatononane, 1-isocyanatodecane, isocyanatocyclohexane, methoxycarbonyl isocyanate, ethoxycarbonyl isocyanate, propoxycarbonyl isocyanate, butoxycarbonyl isocyanate, methoxysulfonyl isocyanate, ethoxysulfonyl isocyanate, propoxysulfonyl isocyanate, butoxysulfonyl isocyanate, fluorosulfonyl isocyanate, methyl isocyanate, butyl isocyanate, phenyl isocyanate, 2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate, ethyl isocyanate, and the like.

[0280] Specific examples of the diisocyanates include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 1,7-diisocyanatoheptane, 1,8-diisocyanatooctane, 1,9-diisocyanatononane, 1,10-diisocyanatodecane, 1,3-diisocyanatopropene, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2-fluorobutane, 1,4-diisocyanato-2,3-difluorobutane, 1,5-diisocyanato-2-pentene, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato-3,4-difluorohexane, toluene diisocyanate, xylene diisocyanate, tolylene diisocyanate, 1,2-bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-1,1'-diisocyanate, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, isophorone diisocyanate, bicyclo[2.2.1]heptane-2,5-diylbis(methyl isocyanate), bicyclo[2.2.1]heptane-2,6-diylbis(methyl isocyanate), 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, 1,4-phenylene diisocyanate, octamethylene diisocyanate, tetramethylene diisocyanate, and the like.

[0281] Specific examples of the triisocyanates include 1,6,11-triisocyanatoundecane, 4-isocyanatomethyl-1,8-octamethylene diisocyanate, 1,3,5-triisocyanatomethylbenzene, 1,3,5-tris(6-isocyanatohex-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 4-(isocyanatomethyl)octamethylene diisocyanate, and the like.

[0282] Among them, 1,6-diisocyanatohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,3,5-tris(6-isocyanatohex-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,4,4-trimethylhexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate are industrially easily available, and are preferable in that the manufacturing cost of the electrolytic solution can be kept low, and also contribute to the formation of a stable film-like structure from a technical viewpoint, and are more preferably used.

[0283] The content of the isocyanate is not particularly limited and is arbitrary as long as the effects of the present disclosure are not significantly impaired. However, with respect to the electrolytic solution, it is preferably 0.001% by mass or more and 1.0% by mass or less. When the content of the isocyanate is at least this lower limit, a sufficient effect of improving the cycle characteristics can be brought about in the non-aqueous electrolytic solution secondary battery. Also, when it is at most this upper limit, an increase in the initial resistance of the non-aqueous electrolytic solution secondary battery can be avoided. The content of the isocyanate is more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and also more preferably 0.8% by mass or less, still more preferably 0.7% by mass or less, particularly preferably 0.6% by mass or less.

[0284] The electrolyte of the present disclosure may contain a cyclic sulfonic acid ester. The cyclic sulfonic acid ester is not particularly limited, and any cyclic sulfonic acid ester can be used. Examples of the cyclic sulfonic acid ester include saturated cyclic sulfonic acid esters, unsaturated cyclic sulfonic acid esters, saturated cyclic disulfonic acid esters, unsaturated cyclic disulfonic acid esters, and the like.

[0285] Specific examples of the saturated cyclic sulfonic acid ester include 1,3 - propane sultone, 1 - fluoro - 1,3 - propane sultone, 2 - fluoro - 1,3 - propane sultone, 3 - fluoro - 1,3 - propane sultone, 1 - methyl - 1,3 - propane sultone, 2 - methyl - 1,3 - propane sultone, 3 - methyl - 1,3 - propane sultone, 1,3 - butane sultone, 1,4 - butane sultone, 1 - fluoro - 1,4 - butane sultone, 2 - fluoro - 1,4 - butane sultone, 3 - fluoro - 1,4 - butane sultone, 4 - fluoro - 1,4 - butane sultone, 1 - methyl - 1,4 - butane sultone, 2 - methyl - 1,4 - butane sultone, 3 - methyl - 1,4 - butane sultone, 4 - methyl - 1,4 - butane sultone, 2,4 - butane sultone, and the like.

[0286] Specific examples of the unsaturated cyclic sulfonic acid ester include 1 - propene - 1,3 - sultone, 2 - propene - 1,3 - sultone, 1 - fluoro - 1 - propene - 1,3 - sultone, 2 - fluoro - 1 - propene - 1,3 - sultone, 3 - fluoro - 1 - propene - 1,3 - sultone, 1 - fluoro - 2 - propene - 1,3 - sultone, 2 - fluoro - 2 - propene - 1,3 - sultone, 3 - fluoro - 2 - propene - 1,3 - sultone, 1 - methyl - 1 - propene - 1,3 - sultone, 2 - methyl - 1 - propene - 1,3 - sultone, 3 - methyl - 1 - propene - 1,3 - sultone, 1 - methyl - 2 - propene - 1,3 - sultone, 2 - methyl - 2 - propene - 1,3 - sultone, 3 - methyl - 2 - propene - 1,3 - sultone, 1 - butene - 1,4 - sultone, 2 - butene - 1,4 - sultone, 3 - butene - 1,4 - sultone, 1 - fluoro - 1 - butene - 1,4 - sultone, 2 - fluoro - 1 - butene - 1,4 - sultone, 3 - fluoro - 1 - butene - 1,4 - sultone, 4 - fluoro - 1 - butene - 1,4 - sultone, 1 - fluoro - 2 - butene - 1,4 - sultone, 2 - fluoro - 2 - butene - 1,4 - sultone, 3 - fluoro - 2 - butene - 1,4 - sultone, 4 - fluoro - 2 - butene - 1,4 - sultone, 1,3 - propenesultone, 1 - fluoro - 3 - butene - 1,4 - sultone, 2 - fluoro - 3 - butene - 1,4 - sultone, 3 - fluoro - 3 - butene - 1,4 - sultone, 4 - fluoro - 3 - butene - 1,4 - sultone, 1 - methyl - 1 - butene - 1,4 - sultone, 2 - methyl - 1 - butene - 1,4 - sultone, 3 - methyl - 1 - butene - 1,4 - sultone, 4 - methyl - 1 - butene - 1,4 - sultone, 1 - methyl - 2 - butene - 1,4 - sultone, 2 - methyl - 2 - butene - 1,4 - sultone, 3 - methyl - 2 - butene - 1,4 - sultone, 4 - methyl - 2 - butene - 1,4 - sultone, 1 - methyl - 3 - butene - 1,4 - sultone, 2 - methyl - 3 - butene - 1,4 - sultone, 3 - methyl - 3 - butene - 1,4 - sultone, 4 - methyl - 3 - butene - 1,4 - sultone, etc.

[0287] Among them, 1,3 - propane sultone, 1 - fluoro - 1,3 - propane sultone, 2 - fluoro - 1,3 - propane sultone, 3 - fluoro - 1,3 - propane sultone, and 1 - propene - 1,3 - sultone are more preferably used because they can contribute to the ease of acquisition and the formation of a stable film - like structure. The content of the cyclic sulfonic acid ester is not particularly limited and is arbitrary as long as the effects of the present disclosure are not significantly impaired. However, it is preferably 0.001% by mass or more and 3.0% by mass or less with respect to the electrolytic solution.

[0288] When the content of the cyclic sulfonic acid ester is at least this lower limit, a sufficient cycle characteristic improvement effect can be brought to the non - aqueous electrolytic solution secondary battery. Also, when it is at most this upper limit, an increase in the manufacturing cost of the non - aqueous electrolytic solution secondary battery can be avoided. The content of the cyclic sulfonic acid ester is more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and also more preferably 2.5% by mass or less, still more preferably 2.0% by mass or less, and particularly preferably 1.8% by mass or less.

[0289] The electrolytic solution of the present disclosure may further contain polyethylene oxide having a weight - average molecular weight of 2000 to 4000 and having - OH, - OCOOH, or - COOH at the terminal. By containing such a compound, the stability of the electrode interface can be improved, and the characteristics of the electrochemical device can be improved. Examples of the above - mentioned polyethylene oxide include polyethylene oxide mono - ol, polyethylene oxide carboxylic acid, polyethylene oxide di - ol, polyethylene oxide di - carboxylic acid, polyethylene oxide tri - ol, polyethylene oxide tri - carboxylic acid, etc. These may be used alone or in combination of two or more. Among them, a mixture of polyethylene oxide mono - ol and polyethylene oxide di - ol, and a mixture of polyethylene carboxylic acid and polyethylene di - carboxylic acid are preferable in that the characteristics of the electrochemical device become better.

[0290] If the weight average molecular weight of the above polyethylene oxide is too small, there is a risk of being easily oxidatively decomposed. The weight average molecular weight is more preferably 3000 to 4000. The weight average molecular weight can be measured by polystyrene conversion by gel permeation chromatography (GPC) method.

[0291] The content of the above polyethylene oxide is 1×10 -6 ~1×10 -2 mol / kg in the electrolyte is preferred. If the content of the above polyethylene oxide is too large, there is a risk of impairing the characteristics of the electrochemical device. The content of the above polyethylene oxide is more preferably 5×10 -6 mol / kg or more.

[0292] The electrolyte of the present disclosure may further contain, as additives, fluorinated saturated cyclic carbonates, unsaturated cyclic carbonates, overcharge preventives, other known auxiliaries, etc. Thereby, a decrease in the characteristics of the electrochemical device can be suppressed.

[0293] Examples of the fluorinated saturated cyclic carbonate include the compounds represented by the above general formula (A). Among them, fluoroethylene carbonate, difluoroethylene carbonate, monofluoromethyl ethylene carbonate, trifluoromethyl ethylene carbonate, 2,2,3,3,3-pentafluoropropyl ethylene carbonate (4-(2,2,3,3,3-pentafluoro-propyl)-[1,3]dioxolan-2-one) are preferred. The fluorinated saturated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.

[0294] The content of the above fluorinated saturated cyclic carbonate is preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass, and still more preferably 0.1 to 3% by mass with respect to the above electrolyte.

[0295] Examples of the unsaturated cyclic carbonates include vinylene carbonates, ethylene carbonates substituted with substituents having an aromatic ring, a carbon-carbon double bond or a carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, catechol carbonates and the like.

[0296] Examples of the vinylene carbonates include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-divinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, ethynyl ethylene carbonate, propargyl ethylene carbonate, methyl vinylene carbonate, dimethyl vinylene carbonate and the like.

[0297] Specific examples of ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond, or a carbon-carbon triple bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ethylene carbonate, 4-allyl-5-ethynyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate, 4-phenyl-5-vinyl ethylene carbonate, 4-allyl-5-phenyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate, 4-methylene-1,3-dioxolan-2-one, 4,5-dimethylene-1,3-dioxolan-2-one, 4-methyl-5-allyl ethylene carbonate, and the like.

[0298] Among them, as the unsaturated cyclic carbonate, vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ethylene carbonate are preferable. Further, vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate are particularly preferable because they form a more stable interfacial protective film, and vinylene carbonate is most preferable.

[0299] The molecular weight of the unsaturated cyclic carbonate is not particularly limited and may be arbitrary as long as the effects of the present disclosure are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. Within this range, it is easy to ensure the solubility of the unsaturated cyclic carbonate in the electrolyte, and the effects of the present disclosure are likely to be fully manifested. The molecular weight of the unsaturated cyclic carbonate is more preferably 80 or more and even more preferably 150 or less.

[0300] The method for producing the unsaturated cyclic carbonate is not particularly limited, and a known method can be arbitrarily selected for production.

[0301] The unsaturated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.

[0302] The content of the above-mentioned unsaturated cyclic carbonate is not particularly limited and may be arbitrary as long as the effects of the present disclosure are not significantly impaired. The content of the above-mentioned unsaturated cyclic carbonate is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.1% by mass or more in 100% by mass of the electrolyte. Also, the above content is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less. Within the above range, the electrochemical device using the electrolyte is likely to exhibit a sufficient effect of improving cycle characteristics, and it is easy to avoid situations such as deterioration of high-temperature storage characteristics, an increase in gas generation amount, and a decrease in discharge capacity retention rate.

[0303] As the unsaturated cyclic carbonate, in addition to the non-fluorinated unsaturated cyclic carbonate as described above, a fluorinated unsaturated cyclic carbonate can also be preferably used. The fluorinated unsaturated cyclic carbonate is a cyclic carbonate having an unsaturated bond and a fluorine atom. The number of fluorine atoms in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as there is one or more. Among them, the number of fluorine atoms is usually 6 or less, preferably 4 or less, and those having 1 or 2 fluorine atoms are most preferred.

[0304] Examples of the fluorinated unsaturated cyclic carbonate include fluorinated vinylene carbonate derivatives, fluorinated ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon double bond, and the like.

[0305] Examples of the fluorinated vinylene carbonate derivative include 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, and the like.

[0306] Examples of the fluorinated ethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon double bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate, and the like.

[0307] Among them, as the fluorinated unsaturated cyclic carbonate, 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, 4-fluoro-4-vinyl ethylene carbonate, 4-fluoro-4-allyl ethylene carbonate, 4-fluoro-5-vinyl ethylene carbonate, 4-fluoro-5-allyl ethylene carbonate, 4,4-difluoro-4-vinyl ethylene carbonate, 4,4-difluoro-4-allyl ethylene carbonate, 4,5-difluoro-4-vinyl ethylene carbonate, 4,5-difluoro-4-allyl ethylene carbonate, 4-fluoro-4,5-divinyl ethylene carbonate, 4-fluoro-4,5-diallyl ethylene carbonate, 4,5-difluoro-4,5-divinyl ethylene carbonate, 4,5-difluoro-4,5-diallyl ethylene carbonate are more preferably used because they form a stable interfacial protective film.

[0308] The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present disclosure are not significantly impaired. The molecular weight is preferably 50 or more and 500 or less. Within this range, it is easy to ensure the solubility of the fluorinated unsaturated cyclic carbonate in the electrolytic solution.

[0309] The production method of the fluorinated unsaturated cyclic carbonate is not particularly limited, and a known method can be arbitrarily selected for production. The molecular weight is more preferably 100 or more and more preferably 200 or less.

[0310] The fluorinated unsaturated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio. Further, the content of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present disclosure are not significantly impaired. The content of the fluorinated unsaturated cyclic carbonate is usually preferably 0.001% by mass or more, more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more in 100% by mass of the electrolytic solution, and preferably 5% by mass or less, more preferably 4% by mass or less, still more preferably 3% by mass or less. Within this range, the electrochemical device using the electrolytic solution is likely to exhibit a sufficient effect of improving the cycle characteristics, and it is easy to avoid situations such as a decrease in the high-temperature storage characteristics, an increase in the gas generation amount, and a decrease in the discharge capacity retention rate.

[0311] The electrolytic solution of the present disclosure may contain a compound having a triple bond. The type is not particularly limited as long as the compound has one or more triple bonds in the molecule. Specific examples of the compound having a triple bond include, for example, the following compounds. Hydrocarbon compounds such as 1-pentyne, 2-pentyne, 1-hexyne, 2-hexyne, 3-hexyne, 1-heptyne, 2-heptyne, 3-heptyne, 1-octyne, 2-octyne, 3-octyne, 4-octyne, 1-nonyne, 2-nonyne, 3-nonyne, 4-nonyne, 1-dodecyne, 2-dodecyne, 3-dodecyne, 4-dodecyne, 5-dodecyne, phenylacetylene, 1-phenyl-1-propyne, 1-phenyl-2-propyne, 1-phenyl-1-butyne, 4-phenyl-1-butyne, 4-phenyl-1-butyne, 1-phenyl-1-pentyne, 5-phenyl-1-pentyne, 1-phenyl-1-hexyne, 6-phenyl-1-hexyne, diphenylacetylene, 4-ethynyltoluene, dicyclohexylacetylene;

[0312] Monocarbonates such as 2-propynyl methyl carbonate, 2-propynyl ethyl carbonate, 2-propynyl propyl carbonate, 2-propynyl butyl carbonate, 2-propynyl phenyl carbonate, 2-propynyl cyclohexyl carbonate, di-2-propynyl carbonate, 1-methyl-2-propynyl methyl carbonate, 1,1-dimethyl-2-propynyl methyl carbonate, 2-butynyl methyl carbonate, 3-butynyl methyl carbonate, 2-pentynyl methyl carbonate, 3-pentynyl methyl carbonate, 4-pentynyl methyl carbonate; Dicarbonates such as 2-butyne-1,4-diol dimethyl dicarbonate, 2-butyne-1,4-diol diethyl dicarbonate, 2-butyne-1,4-diol dipropyl dicarbonate, 2-butyne-1,4-diol dibutyl dicarbonate, 2-butyne-1,4-diol diphenyl dicarbonate, 2-butyne-1,4-diol dicyclohexyl dicarbonate;

[0313] 2-propynyl acetate, 2-propynyl propionate, 2-propynyl butyrate, 2-propynyl benzoate, 2-propynyl cyclohexanecarboxylate, 1,1-dimethyl-2-propynyl acetate, 1,1-dimethyl-2-propynyl propionate, 1,1-dimethyl-2-propynyl butyrate, 1,1-dimethyl-2-propynyl benzoate, 1,1-dimethyl-2-propynyl cyclohexanecarboxylate, 2-butynyl acetate, 3-butynyl acetate, 2-pentynyl acetate, 3-pentynyl acetate, 4-pentynyl acetate, methyl acrylate, ethyl acrylate, propyl acrylate, vinyl acrylate, 2-propenyl acrylate, 2-butenyl acrylate, 3-butenyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, vinyl methacrylate, 2-propenyl methacrylate, 2-butenyl methacrylate, 3-butenyl methacrylate, methyl 2-propynoate, ethyl 2-propynoate, propyl 2-propynoate, vinyl 2-propynoate, 2-propenyl 2-propynoate, 2-butenyl 2-propynoate, 3-butenyl 2-propynoate, methyl 2-butynoate, ethyl 2-butynoate, propyl 2-butynoate, vinyl 2-butynoate, 2-propenyl 2-butynoate, 2-butenyl 2-butynoate, 3-butenyl 2-butynoate, methyl 3-butynoate, ethyl 3-butynoate, propyl 3-butynoate, vinyl 3-butynoate, 2-propenyl 3-butynoate, 2-butenyl 3-butynoate, 3-butenyl 3-butynoate, methyl 2-pentynoate, ethyl 2-pentynoate, propyl 2-pentynoate, vinyl 2-pentynoate, 2-propenyl 2-pentynoate, 2-butenyl 2-pentynoate, 3-butenyl 2-pentynoate, methyl 3-pentynoate, ethyl 3-pentynoate, propyl 3-pentynoate, vinyl 3-pentynoate, 2-propenyl 3-pentynoate, 2-butenyl 3-pentynoate, 3-butenyl 3-pentynoate, methyl 4-pentynoate, ethyl 4-pentynoate, propyl 4-pentynoate, vinyl 4-pentynoate, 2-propenyl 4-pentynoate, 2-butenyl 4-pentynoate, 3-butenyl 4-pentynoate and other monocarboxylic acid esters, fumaric acid esters, methyl pivalate, ethyl pivalate;

[0314] 2-Butyne-1,4-diol diacetate, 2-butyne-1,4-diol dipropionate, 2-butyne-1,4-diol dibutyrate, 2-butyne-1,4-diol dibenzoate, 2-butyne-1,4-diol dicyclohexanecarboxylate, hexahydrobenzo[1,3,2]dioxathiolan-2-oxide (dicarboxylic acid esters such as 1,2-cyclohexanediol, 2,2-dioxide-1,2-oxathiolan-4-yl acetate, 2,2-dioxide-1,2-oxathiolan-4-yl acetate;

[0315] Methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, propyl 2-propynyl oxalate, 2-propynyl vinyl oxalate, allyl 2-propynyl oxalate, di-2-propynyl oxalate, 2-butynyl methyl oxalate, 2-butynyl ethyl oxalate, 2-butynyl propyl oxalate, 2-butynyl vinyl oxalate, allyl 2-butynyl oxalate, di-2-butynyl oxalate, 3-butynyl methyl oxalate, 3-butynyl ethyl oxalate, 3-butynyl propyl oxalate, 3-butynyl vinyl oxalate, allyl 3-butynyl oxalate, di-3-butynyl oxalate and other oxalic acid diesters;

[0316] Phosphine oxides such as methyl(2-propynyl)(vinyl)phosphine oxide, divinyl(2-propynyl)phosphine oxide, di(2-propynyl)(vinyl)phosphine oxide, di(2-propenyl)2(-propynyl)phosphine oxide, di(2-propynyl)(2-propenyl)phosphine oxide, di(3-butenyl)(2-propynyl)phosphine oxide, and di(2-propynyl)(3-butenyl)phosphine oxide;

[0317] 2-Propynyl methyl(2-propenyl)phosphonate, 2-propynyl 2-butenyl(methyl)phosphonate, 2-propynyl di(2-propenyl)phosphonate, 2-propynyl di(3-butenyl)phosphonate, 1,1-Dimethyl-2-propynyl methyl(2-propenyl)phosphonate, 1,1-Dimethyl-2-propynyl 2-butenyl(methyl)phosphonate, 1,1-Dimethyl-2-propynyl di(2-propenyl)phosphonate, 1,1-Dimethyl-2-propynyl di(3-butenyl)phosphonate, 2-propenyl methyl(2-propynyl)phosphonate, 3-butenyl methyl(2-propynyl)phosphonate, 2-propenyl di(2-propynyl)phosphonate, 3-butenyl di(2-propynyl)phosphonate, 2-propenyl 2-propynyl(2-propenyl)phosphonate, 3-butenyl 2-propynyl(2-propenyl)phosphonate and other phosphonic acid esters;

[0318] 2-Propynyl methyl 2-propenylphosphonate, 2-propynyl methyl(2-butenyl)phosphonate, 2-propynyl (2-propenyl)(2-propenyl)phosphonate, 2-propynyl (3-butenyl)(3-butenyl)phosphonate, 2-propynyl (1,1-dimethyl-2-propynyl)(methyl)phosphonate, 2-propynyl (1,1-dimethyl-2-propynyl)(2-butenyl)phosphonate, 2-propynyl (1,1-dimethyl-2-propynyl)(2-propenyl)phosphonate, 2-propynyl (3-butenyl)(1,1-dimethyl-2-propynyl)phosphonate, methyl (2-propynyl)(2-propenyl)phosphonate, methyl (2-propynyl)(3-butenyl)phosphonate, methyl (1,1-dimethyl-2-propynyl)(2-propenyl)phosphonate, methyl (3-butenyl)(1,1-dimethyl-2-propynyl)phosphonate, ethyl (2-propynyl)(2-propenyl)phosphonate, ethyl (2-propynyl)(3-butenyl)phosphonate, ethyl (1,1-dimethyl-2-propynyl)(2-propenyl)phosphonate, and ethyl (3-butenyl)(1,1-dimethyl-2-propynyl)phosphonate and other phosphonic acid esters;

[0319] Phosphoric acid (methyl)(2-propenyl)(2-propynyl), phosphoric acid (ethyl)(2-propenyl)(2-propynyl), phosphoric acid (2-butenyl)(methyl)(2-propynyl), phosphoric acid (2-butenyl)(ethyl)(2-propynyl), phosphoric acid (1,1-dimethyl-2-propynyl)(methyl)(2-propenyl), phosphoric acid (1,1-dimethyl-2-propynyl)(ethyl)(2-propenyl), phosphoric acid (2-butenyl)(1,1-dimethyl-2-propynyl)(methyl), and phosphoric acid (2-butenyl)(ethyl)(1,1-dimethyl-2-propynyl) and other phosphate esters;

[0320] Among these, compounds having an alkynyloxy group are preferable because they form a negative electrode film more stably in the electrolytic solution.

[0321] Furthermore, compounds such as 2-propynyl methyl carbonate, di-2-propynyl carbonate, 2-butyne-1,4-diol dimethyl dicarbonate, 2-propynyl acetate, 2-butyne-1,4-diol diacetate, methyl 2-propynyl oxalate, and di-2-propynyl oxalate are particularly preferable from the viewpoint of improving storage characteristics.

[0322] The compounds having the above triple bond may be used alone or in combination of two or more in any combination and ratio. There is no limit to the blending amount of the compound having a triple bond with respect to the entire electrolytic solution of the present disclosure, and it is arbitrary as long as the effects of the present disclosure are not significantly impaired. However, with respect to the electrolytic solution of the present disclosure, it is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less. When the above range is satisfied, effects such as output characteristics, load characteristics, cycle characteristics, and high-temperature storage characteristics are further improved.

[0323] In the electrolytic solution of the present disclosure, an overcharge inhibitor can be used in order to effectively suppress battery rupture and ignition when the electrochemical device using the electrolytic solution is in a state such as overcharge.

[0324] Examples of the overcharge prevention agent include terphenyl derivatives unsubstituted or substituted with an alkyl group such as biphenyl, o - terphenyl, m - terphenyl, p - terphenyl, partial hydrides of terphenyl derivatives unsubstituted or substituted with an alkyl group, cyclohexylbenzene, t - butylbenzene, t - amylbenzene, diphenyl ether, dibenzofuran, diphenylcyclohexane, 1,1,3 - trimethyl - 3 - phenylindane, cyclopentylbenzene, cyclohexylbenzene, cumene, 1,3 - diisopropylbenzene, 1,4 - diisopropylbenzene, t - butylbenzene, t - amylbenzene, t - hexylbenzene, anisole and other aromatic compounds; partial fluorides of the above aromatic compounds such as 2 - fluorobiphenyl, 4 - fluorobiphenyl, o - cyclohexylfluorobenzene, p - cyclohexylfluorobenzene, o - cyclohexylfluorobenzene, p - cyclohexylfluorobenzene fluorobenzene, fluorotoluene, benzotrifluoride; fluorine - containing anisole compounds such as 2,4 - difluoroanisole, 2,5 - difluoroanisole, 1,6 - difluoroanisole, 2,6 - difluoroanisole, 3,5 - difluoroanisole; aromatic acetates such as 3 - propylphenyl acetate, 2 - ethylphenyl acetate, benzylphenyl acetate, methylphenyl acetate, benzyl acetate, phenethylphenyl acetate; aromatic carbonates such as diphenyl carbonate, methylphenyl carbonate, toluene derivatives such as toluene, xylene, biphenyl derivatives unsubstituted or substituted with an alkyl group such as 2 - methylbiphenyl, 3 - methylbiphenyl, 4 - methylbiphenyl, o - cyclohexylbiphenyl and the like. Among them, biphenyl, alkylbiphenyl, terphenyl, partial hydrogenated terphenyl, aromatic compounds such as cyclohexylbenzene, t - butylbenzene, t - amylbenzene, diphenyl ether, dibenzofuran, diphenylcyclohexane, 1,1,3 - trimethyl - 3 - phenylindane, 3 - propylphenyl acetate, 2 - ethylphenyl acetate, benzylphenyl acetate, methylphenyl acetate, benzyl acetate, diphenyl carbonate, methylphenyl carbonate and the like are preferred.These may be used alone or in combination of two or more. When two or more are used in combination, in particular, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, at least one selected from oxygen-free aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, and t-amylbenzene, and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether and dibenzofuran are preferably used in combination from the viewpoint of the balance between overcharge prevention characteristics and high-temperature storage characteristics.

[0325] The electrolytic solution of the present disclosure may further contain a compound (5) represented by the general formula (5).

[0326] General formula (5):

Chemical formula

[0327] A a+ includes lithium ion, sodium ion, potassium ion, magnesium ion, calcium ion, barium ion, cesium ion, silver ion, zinc ion, copper ion, cobalt ion, iron ion, nickel ion, manganese ion, titanium ion, lead ion, chromium ion, vanadium ion, ruthenium ion, yttrium ion, lanthanoid ion, actinoid ion, tetrabutylammonium ion, tetraethylammonium ion, tetramethylammonium ion, triethylmethylammonium ion, triethylammonium ion, pyridinium ion, imidazolium ion, hydrogen ion, tetraethylphosphonium ion, tetramethylphosphonium ion, tetraphenylphosphonium ion, triphenylsulfonium ion, triethylsulfonium ion, etc.

[0328] When used for applications such as electrochemical devices, A a+ is preferably a lithium ion, sodium ion, magnesium ion, tetraalkylammonium ion, or hydrogen ion, and particularly preferably a lithium ion. A a+ The valence a of the cation of A is an integer from 1 to 3. When it is greater than 3, the crystal lattice energy becomes large, resulting in a problem that it becomes difficult to dissolve in a solvent. Therefore, when solubility is required, 1 is more preferable. Similarly, the valence b of the anion is also an integer from 1 to 3, and particularly 1 is preferable. The constant p representing the ratio of the cation to the anion is necessarily determined by the ratio b / a of the valences of both.

[0329] Next, the ligand part of the general formula (5) will be described. In this specification, Z in the general formula (5) 201 The organic or inorganic part bonded to is called a ligand.

[0330] Z 201 is preferably Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf, or Sb, and more preferably Al, B, or P.

[0331] X 201 represents O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms. These alkylene groups and arylene groups may have substituents or heteroatoms in their structures. Specifically, instead of hydrogen on the alkylene group and arylene group, a halogen atom, a linear or cyclic alkyl group, an aryl group, an alkenyl group, an alkoxy group, an aryloxy group, a sulfonyl group, an amino group, a cyano group, a carbonyl group, an acyl group, an amide group, or a hydroxyl group may be used as a substituent, or a structure in which nitrogen, sulfur, or oxygen is introduced instead of carbon on the alkylene and arylene may also be used. Also, when n202 is 1 and n203 is 2 to 4, n203 X 201They may each be bonded. Examples thereof include ligands such as ethylenediaminetetraacetic acid.

[0332] L 201 represents a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms, or -Z 203 Y 203 (Z 203 and Y 203 will be described later). The alkyl group and aryl group here may also have substituents and heteroatoms in their structures, and when n201 is 2 to 8, n201 Ls 201 may each be bonded to form a ring. As L 201 , a fluorine atom or a cyano group is preferable. In the case of a fluorine atom, the solubility and dissociation degree of the salt of the anion compound are improved, and accordingly, the ionic conductivity is improved. In addition, the oxidation resistance is improved, and thus the occurrence of side reactions can be suppressed. 201

[0333] Y 201 Y 202 and Z 203 each independently represent O, S, NY 204 , a hydrocarbon group, or a fluorinated hydrocarbon group. Y 201 and Y 202 are preferably O, S, or NY 204 , and more preferably O. As a characteristic of compound (5), since there is a bond between Y 201 and Y 202 to Z 201 in the same ligand, these ligands form a chelate structure with Z 201 . Due to the effect of this chelate, the heat resistance, chemical stability, and hydrolysis resistance of this compound are improved. The constant n202 in this ligand is 0 or 1, and particularly, when it is 0, this chelate ring becomes a 5-membered ring, so the chelate effect is most strongly exerted and the stability is increased, which is preferable. In addition, in this specification, a fluorinated hydrocarbon group is a group in which at least one hydrogen atom of a hydrocarbon group is substituted with a fluorine atom.

[0334] Y 203 and Y 204 are each independently H, F, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogenated aryl group having 6 to 20 carbon atoms, and these alkyl groups and aryl groups may have a substituent or a heteroatom in their structures, and when 203 Y or 204 Y is present in plural, they may each be bonded to form a ring.

[0335] In addition, the constant n203 related to the number of the above-described ligands is an integer of 1 to 4, preferably 1 or 2, more preferably 2. Further, the constant n201 related to the number of the above-described ligands is an integer of 0 to 8, preferably an integer of 0 to 4, more preferably 0, 2, or 4. Furthermore, when n203 is 1, n201 is preferably 2, and when n203 is 2, n201 is preferably 0.

[0336] In the general formula (5), the alkyl group, the halogenated alkyl group, the aryl group, and the halogenated aryl group include those having a branch or other functional groups such as a hydroxyl group and an ether bond.

[0337] Compound (5) is a compound represented by the general formula:

Chemical formula

Chemical formula

[0338] Examples of the compound (5) include lithium oxalatoborate salts, and the following formula:

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0339] Examples of the compound (5) also include dicarboxylic acid complex salts in which the complex central element is boron, such as lithium bis(malonato)borate, lithium difluoro(malonato)borate, lithium bis(methylmalonato)borate, lithium difluoro(methylmalonato)borate, lithium bis(dimethylmalonato)borate, and lithium difluoro(dimethylmalonato)borate.

[0340] Examples of the compound (5) also include dicarboxylic acid complex salts in which the complex central element is phosphorus, such as lithium tris(oxalato)phosphate, lithium tris(malonato)phosphate, lithium difluorobis(malonato)phosphate, lithium tetrafluoro(malonato)phosphate, lithium tris(methylmalonato)phosphate, lithium difluorobis(methylmalonato)phosphate, lithium tetrafluoro(methylmalonato)phosphate, lithium tris(dimethylmalonato)phosphate, lithium difluorobis(dimethylmalonato)phosphate, and lithium tetrafluoro(dimethylmalonato)phosphate.

[0341] Examples of the compound (5) also include dicarboxylic acid complex salts in which the complex central element is aluminum, such as LiAl(C2O4)2 and LiAlF2(C2O4).

[0342] Among them, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tris(oxalato)phosphate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate are more preferably used because they can contribute to easy availability and formation of a stable film-like structure. Lithium bis(oxalato)borate is particularly preferred as the compound (5).

[0343] The content of the compound (5) is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, preferably 10% by mass or less, and more preferably 3% by mass or less with respect to the above solvent because more excellent cycle characteristics can be obtained.

[0344] A carboxylic anhydride (excluding the compound (2)) may be used in the electrolyte used in the present disclosure. As the carboxylic anhydride, the compound (6) represented by the following general formula (6) is preferred. The production method of the carboxylic anhydride is not particularly limited, and a known method can be arbitrarily selected for production. General formula (6):

[0345]

Chem.

[0346] R 61 , R 62 As long as it is a monovalent hydrocarbon group, its type is not particularly limited. For example, it may be an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded. The aliphatic hydrocarbon group may be a saturated hydrocarbon group or may contain an unsaturated bond (carbon-carbon double bond or carbon-carbon triple bond). Further, the aliphatic hydrocarbon group may be linear or cyclic. In the case of a linear shape, it may be straight-chain or branched-chain. Furthermore, a group in which a linear and a cyclic are bonded may also be acceptable. Note that R 61 and R 62 may be the same as or different from each other.)

[0347] Also, when the hydrocarbon groups of R 61 , R 62 have a substituent, the type of the substituent is not particularly limited as long as it does not contradict the gist of the present disclosure. Examples include halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom, preferably a fluorine atom. Also, as substituents other than halogen atoms, substituents having functional groups such as ester group, cyano group, carbonyl group, and ether group are also included, preferably cyano group and carbonyl group. The hydrocarbon groups of R 61 , R 62 may have only one of these substituents or two or more of them. When having two or more substituents, those substituents may be the same or different from each other.)

[0348] R 61 , R 62The carbon number of each of the hydrocarbon groups is usually 1 or more, and usually 15 or less, preferably 12 or less, more preferably 10 or less, and still more preferably 9 or less. R 61 and R 62 are bonded to each other to form a divalent hydrocarbon group, the carbon number of the divalent hydrocarbon group is usually 1 or more, and usually 15 or less, preferably 13 or less, more preferably 10 or less, and still more preferably 8 or less. Incidentally, when R 61 , R 62 has a substituent containing a carbon atom, it is preferable that the total carbon number of R 61 , R 62 including the substituent satisfies the above range.

[0349] Next, specific examples of the above compound (6) will be described. In the following examples, the "analog" refers to an acid anhydride obtained by replacing a part of the structure of the exemplified acid anhydride with another structure within a range not contrary to the spirit of the present disclosure. For example, dimers, trimers, and tetramers composed of a plurality of acid anhydrides, or structural isomers such as those having the same carbon number of substituents but having a branched chain, those having different sites where the substituents are bonded to the acid anhydride, and the like can be mentioned.

[0350] First, specific examples of acid anhydrides in which R 61 , R 62 are the same are given below.

[0351] R 61 , R 62 Specific examples of acid anhydrides in which are linear alkyl groups include acetic anhydride, propionic anhydride, butanoic anhydride, 2-methylpropionic anhydride, 2,2-dimethylpropionic anhydride, 2-methylbutanoic anhydride, 3-methylbutanoic anhydride, 2,2-dimethylbutanoic anhydride, 2,3-dimethylbutanoic anhydride, 3,3-dimethylbutanoic anhydride, 2,2,3-trimethylbutanoic anhydride, 2,3,3-trimethylbutanoic anhydride, 2,2,3,3-tetramethylbutanoic anhydride, 2-ethylbutanoic anhydride, and the like, and their analogs.

[0352] R61 and R 62 Specific examples of the acid anhydride in which R is a cyclic alkyl group include cyclopropanecarboxylic anhydride, cyclopentanecarboxylic anhydride, cyclohexanecarboxylic anhydride, and the like, and their analogs.

[0353] R 61 and R 62 Specific examples of the acid anhydride in which R and R are alkenyl groups include acrylic anhydride, 2-methylacrylic anhydride, 3-methylacrylic anhydride, 2,3-dimethylacrylic anhydride, 3,3-dimethylacrylic anhydride, 2,3,3-trimethylacrylic anhydride, 2-phenylacrylic anhydride, 3-phenylacrylic anhydride, 2,3-diphenylacrylic anhydride, 3,3-diphenylacrylic anhydride, 3-butenoic anhydride, 2-methyl-3-butenoic anhydride, 2,2-dimethyl-3-butenoic anhydride, 3-methyl-3-thenoic anhydride, 2-methyl-3-methyl-3-butenoic anhydride, 2,2-dimethyl-3-methyl-3-butenoic anhydride, 3-pentenoic anhydride, 4-pentenoic anhydride, 2-cyclopentene carboxylic anhydride, 3-cyclopentene carboxylic anhydride, 4-cyclopentene carboxylic anhydride, and the like, and their analogs.

[0354] R 61 and R 62 Specific examples of the acid anhydride in which R and R are alkynyl groups include propiolic anhydride, 3-phenylpropiolic anhydride, 2-butynoic anhydride, 2-pentynoic anhydride, 3-butynoic anhydride, 3-pentynoic anhydride, 4-pentynoic anhydride, and the like, and their analogs.

[0355] R 61 and R 62 Specific examples of the acid anhydride in which R and R are aryl groups include benzoic anhydride, 4-methylbenzoic anhydride, 4-ethylbenzoic anhydride, 4-tert-butylbenzoic anhydride, 2-methylbenzoic anhydride, 2,4,6-trimethylbenzoic anhydride, 1-naphthalenecarboxylic anhydride, 2-naphthalenecarboxylic anhydride, and the like, and their analogs.

[0356] Also, R 61 、R 62 Examples of acid anhydrides in which R

[0357] 、R 61 、R 62 is a halogen atom-substituted chain alkyl group are given below. Acid anhydrides obtained by substituting some or all of these fluorine atoms with chlorine atoms, bromine atoms, or iodine atoms are also included in the exemplified compounds. Examples of acid anhydrides in which R

[0358] 、R 61 、R 62 is a halogen atom-substituted cyclic alkyl group include 2-fluorocyclopentanecarboxylic anhydride, 3-fluorocyclopentanecarboxylic anhydride, 4-fluorocyclopentanecarboxylic anhydride, and the like, and their analogs. Examples of acid anhydrides in which R

[0359] 、R 61 、R 62Examples of acid anhydrides in which the alkenyl group is substituted with a halogen atom include 2-fluoroacrylic anhydride, 3-fluoroacrylic anhydride, 2,3-difluoroacrylic anhydride, 3,3-difluoroacrylic anhydride, 2,3,3-trifluoroacrylic anhydride, 2-(trifluoromethyl)acrylic anhydride, 3-(trifluoromethyl)acrylic anhydride, 2,3-bis(trifluoromethyl)acrylic anhydride, 2,3,3-tris(trifluoromethyl)acrylic anhydride, 2-(4-fluorophenyl)acrylic anhydride, 3-(4-fluorophenyl)acrylic anhydride, 2,3-bis(4-fluorophenyl)acrylic anhydride, 3,3-bis(4-fluorophenyl)acrylic anhydride, 2-fluoro-3-butenoic anhydride, 2,2-difluoro-3-butenoic anhydride, 3-fluoro-2-butenoic anhydride, 4-fluoro-3-butenoic anhydride, 3,4-difluoro-3-butenoic anhydride, 3,3,4-trifluoro-3-butenoic anhydride, and the like, and analogs thereof.

[0360] R 61 、R 62 Examples of acid anhydrides in which the alkynyl group is substituted with a halogen atom include 3-fluoro-2-propynoic anhydride, 3-(4-fluorophenyl)-2-propynoic anhydride, 3-(2,3,4,5,6-pentafluorophenyl)-2-propynoic anhydride, 4-fluoro-2-butynoic anhydride, 4,4-difluoro-2-butynoic anhydride, 4,4,4-trifluoro-2-butynoic anhydride, and the like, and analogs thereof.

[0361] R 61 、R 62 Examples of acid anhydrides in which the aryl group is substituted with a halogen atom include 4-fluorobenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, 4-(trifluoromethyl)benzoic anhydride, and the like, and analogs thereof.

[0362] R 61 、R 62Examples of acid anhydrides having substituents with functional groups such as esters, nitriles, ketones, ethers, etc. include methoxyformic anhydride, ethoxyformic anhydride, methyl oxalic anhydride, ethyl oxalic anhydride, 2-cyanoacetic anhydride, 2-oxopropionic anhydride, 3-oxobutyric anhydride, 4-acetylbenzoic anhydride, methoxyacetic anhydride, 4-methoxybenzoic anhydride, etc., and their analogs.

[0363] Subsequently, R 61 and R 62 Specific examples of acid anhydrides in which are different from each other are listed below.

[0364] R 61 and R 62 All combinations of the examples listed above and their analogs are conceivable, but representative examples are listed below.

[0365] Examples of combinations of linear alkyl groups include propionic acetic anhydride, butyric acetic anhydride, propionic butyric anhydride, 2-methylpropionic acetic anhydride, etc.

[0366] Examples of combinations of a linear alkyl group and a cyclic alkyl group include cyclopentanecarboxylic acetic anhydride, cyclohexanecarboxylic acetic anhydride, cyclopentanecarboxylic propionic anhydride, etc.

[0367] Examples of combinations of a linear alkyl group and an alkenyl group include acrylic acetic anhydride, 3-methylacrylic acetic anhydride, 3-butenoic acetic anhydride, propionic acrylic anhydride, etc.

[0368] Examples of combinations of a linear alkyl group and an alkynyl group include propiolic acetic anhydride, 2-butynoic acetic anhydride, 3-butynoic acetic anhydride, 3-phenylpropiolic acetic anhydride propiolic propionic anhydride, etc.

[0369] Examples of combinations of a chain alkyl group and an aryl group include acetic benzoic anhydride, 4-methylacetic benzoic anhydride, 1-naphthalenecarboxylic acetic anhydride, propionic benzoic anhydride, and the like.

[0370] Examples of combinations of a chain alkyl group and a hydrocarbon group having a functional group include fluoroacetic acetic anhydride, trifluoroacetic acetic anhydride, 4-fluoroacetic benzoic anhydride, fluoroacetic propionic anhydride, alkyl oxalic acetic anhydride, 2-cyanoacetic acetic anhydride, 2-oxopropionic acetic anhydride, methoxyacetic acetic anhydride, methoxyacetic propionic anhydride, and the like.

[0371] Examples of combinations of cyclic alkyl groups include cyclopentanoic cyclohexanoic anhydride, and the like.

[0372] Examples of combinations of a cyclic alkyl group and an alkenyl group include acrylic cyclopentanoic anhydride, 3-methylacrylic cyclopentanoic anhydride, 3-butenoic cyclopentanoic anhydride, acrylic cyclohexanoic anhydride, and the like.

[0373] Examples of combinations of a cyclic alkyl group and an alkynyl group include propiolic cyclopentanoic anhydride, 2-butynoic cyclopentanoic anhydride, propiolic cyclohexanoic anhydride, and the like.

[0374] Examples of combinations of a cyclic alkyl group and an aryl group include benzoic cyclopentanoic anhydride, 4-methylbenzoic cyclopentanoic anhydride, benzoic cyclohexanoic anhydride, and the like.

[0375] Examples of combinations of a cyclic alkyl group and a hydrocarbon group having a functional group include fluoroacetic cyclopentanoic anhydride, cyclopentanoic trifluoroacetic anhydride, cyclopentanoic 2-cyanoacetic anhydride, cyclopentanoic methoxyacetic anhydride, cyclohexanoic fluoroacetic anhydride, and the like.

[0376] Examples of combinations of alkenyl groups include acrylic acid 2-methylacrylic anhydride, acrylic acid 3-methylacrylic anhydride, acrylic acid 3-butenoic anhydride, 2-methylacrylic acid 3-methylacrylic anhydride, and the like.

[0377] Examples of combinations of an alkenyl group and an alkynyl group include acrylic acid propiolic anhydride, acrylic acid 2-butynoic anhydride, 2-methylacrylic acid propiolic anhydride, and the like.

[0378] Examples of combinations of an alkenyl group and an aryl group include acrylic acid benzoic anhydride, acrylic acid 4-methylbenzoic anhydride, 2-methylacrylic acid benzoic anhydride, and the like.

[0379] Examples of combinations of an alkenyl group and a hydrocarbon group having a functional group include acrylic acid fluoroacetic anhydride, acrylic acid trifluoroacetic anhydride, acrylic acid 2-cyanoacetic anhydride, acrylic acid methoxyacetic anhydride, 2-methylacrylic acid fluoroacetic anhydride, and the like.

[0380] Examples of combinations of alkynyl groups include propiolic acid 2-butynoic anhydride, propiolic acid 3-butynoic anhydride, 2-butynoic acid 3-butynoic anhydride, and the like.

[0381] Examples of combinations of an alkynyl group and an aryl group include benzoic acid propiolic anhydride, 4-methylbenzoic acid propiolic anhydride, benzoic acid 2-butynoic anhydride, and the like.

[0382] Examples of combinations of an alkynyl group and a hydrocarbon group having a functional group include propiolic acid fluoroacetic anhydride, propiolic acid trifluoroacetic anhydride, propiolic acid 2-cyanoacetic anhydride, propiolic acid methoxyacetic anhydride, 2-butynoic acid fluoroacetic anhydride, and the like.

[0383] Examples of combinations of aryl groups include 4-methylbenzoic anhydride, 1-naphthalenecarboxylic anhydride, 4-methylbenzoic 1-naphthalenecarboxylic anhydride, and the like.

[0384] Examples of combinations of an aryl group and a hydrocarbon group having a functional group include benzoic fluoroacetic anhydride, benzoic trifluoroacetic anhydride, benzoic 2-cyanoacetic anhydride, benzoic methoxyacetic anhydride, 4-methylbenzoic fluoroacetic anhydride, and the like.

[0385] Examples of combinations of hydrocarbon groups having functional groups include fluoroacetic trifluoroacetic anhydride, fluoroacetic 2-cyanoacetic anhydride, fluoroacetic methoxyacetic anhydride, trifluoroacetic 2-cyanoacetic anhydride, and the like.

[0386] Among the acid anhydrides forming the above chain structure, preferably, acetic anhydride, propionic anhydride, 2-methylpropionic anhydride, cyclopentanecarboxylic anhydride, cyclohexanecarboxylic anhydride, etc., acrylic anhydride, 2-methylacrylic anhydride, 3-methylacrylic anhydride, 2,3-dimethylacrylic anhydride, 3,3-dimethylacrylic anhydride, 3-butenoic anhydride, 2-methyl-3-butenoic anhydride, propiolic anhydride, 2-butynoic anhydride, benzoic anhydride, 2-methylbenzoic anhydride, 4-methylbenzoic anhydride, 4-tert-butylbenzoic anhydride, trifluoroacetic anhydride, 3,3,3-trifluoropropionic anhydride, 2-(trifluoromethyl)acrylic anhydride, 2-(4-fluorophenyl)acrylic anhydride, 4-fluorobenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, methoxyformic anhydride, ethoxyformic anhydride, and more preferably, 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.

[0387] These compounds preferably form a bond with lithium oxalate salt appropriately to form a film with excellent durability, and can improve the charge and discharge rate characteristics, input / output characteristics, and impedance characteristics, particularly after the durability test.

[0388] There is no limitation on the molecular weight of the carboxylic anhydride, and it is arbitrary as long as the effects of the present disclosure are not significantly impaired. Usually, it is 90 or more, preferably 95 or more, while usually 300 or less, preferably 200 or less. When the molecular weight of the carboxylic anhydride is within the above range, an increase in the viscosity of the electrolytic solution can be suppressed, and the film density can be optimized, so that the durability can be appropriately improved.

[0389] In addition, there is no particular limitation on the production method of the carboxylic anhydride, and a known method can be arbitrarily selected for production. The carboxylic anhydride described above may be contained alone in any one of the non-aqueous electrolytic solutions of the present disclosure, or two or more kinds may be jointly possessed in any combination and ratio.

[0390] In addition, there is no particular limitation on the content of the carboxylic anhydride in the electrolytic solution of the present disclosure, and it is arbitrary as long as the effects of the present disclosure are not significantly impaired. However, it is preferably contained in the electrolytic solution of the present disclosure at a concentration of usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less. When the content of the carboxylic anhydride is within the above range, the effect of improving the cycle characteristics is likely to be exhibited, and the reactivity is suitable, so that the battery characteristics are likely to be improved.

[0391] Known other auxiliaries can be used in the electrolytic solution of the present disclosure. Other auxiliaries include hydrocarbon compounds such as pentane, heptane, octane, nonane, decane, cycloheptane, benzene, furan, naphthalene, 2-phenylbicyclohexyl, cyclohexane, 2,4,8,10-tetraoxaspiro[5.5]undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane; Fluorinated aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene, benzotrifluoride, monofluorobenzene, 1-fluoro-2-cyclohexylbenzene, 1-fluoro-4-tert-butylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-2-cyclohexylbenzene, fluorinated biphenyl, etc.; Carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate, etc.; Ether compounds such as dioxolane, dioxane, 2,5,8,11-tetraoxadodecane, 2,5,8,11,14-pentaoxapentadecane, ethoxymethoxyethane, trimethoxymethane, glyme, ethyl monoglyme, etc.; Ketone compounds such as dimethyl ketone, diethyl ketone, 3-pentanone, etc.; Acid anhydrides such as 2-allyl succinic anhydride, etc.; Ester compounds such as dimethyl oxalate, diethyl oxalate, ethyl methyl oxalate, di(2-propynyl) oxalate, methyl 2-propynyl oxalate, dimethyl succinate, di(2-propynyl) glutarate, methyl formate, ethyl formate, 2-propynyl formate, 2-butyne-1,4-diyl diformate, 2-propynyl methacrylate, dimethyl malonate, etc.; Amide compounds such as acetamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, etc.; Sulfur-containing compounds such as ethylene sulfate, vinylene sulfate, ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, sulfolene, diphenyl sulfone, N,N-dimethylmethanesulfonamide, N,N-diethylmethanesulfonamide, methyl vinyl sulfonate, ethyl vinyl sulfonate, allyl vinyl sulfonate, propargyl vinyl sulfonate, methyl allyl sulfonate, ethyl allyl sulfonate, allyl allyl sulfonate, propargyl allyl sulfonate, 1,2-bis(vinylsulfonyloxy)ethane, propane disulfonic anhydride, sulfobutyric anhydride, sulfobenzoic anhydride, sulfopropionic anhydride, ethane disulfonic anhydride, methylene methanedisulfonate, 2-propynyl methanesulfonate, pentene sulfite, pentafluorophenyl methanesulfonate, propylene sulfate, propylene sulfite, propanesultone, butylene sulfite, butane-2,3-diyl dimethanesulfonate, 2-butyne-1,4-diyl dimethanesulfonate, 2-propynyl vinyl sulfonate, bis(2-vinylsulfonylethyl) ether, 5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide, 2-propynyl 2-(methanesulfonyloxy)propionate, 5,5-dimethyl-1,2-oxathiolan-4-one 2,2-dioxide, 3-sulfo-propionic anhydride trimethylene methanedisulfonate 2-methyltetrahydrofuran, trimethylene methanedisulfonate, tetramethylene sulfoxide, dimethylene methanedisulfonate, difluoroethyl methyl sulfone, divinyl sulfone, 1,2-bis(vinylsulfonyl)ethane, ethylene bis(methyl sulfonate), ethylene bis(ethyl sulfonate), ethylene sulfate, thiophene 1-oxide; Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide, nitromethane, nitroethane, ethylenediamine; Trimethyl phosphite, triethyl phosphite, triphenyl phosphite, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl vinylphosphonate, diethyl vinylphosphonate, ethyl diethylphosphonoacetate, methyl dimethylphosphinate, ethyl diethylphosphinate, trimethylphosphine oxide, triethylphosphine oxide, bis(2,2-difluoroethyl) 2,2,2-trifluoroethyl phosphate, bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl phosphate, bis(2,2,2-trifluoroethyl) methyl phosphate, bis(2,2,2-trifluoroethyl) ethyl phosphate, bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate, bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl phosphate, tributyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, tris(1,1,1,3,3,3-hexafluoropropan-2-yl) phosphate, trioctyl phosphate, 2-phenylphenyl dimethyl phosphate, 2-phenylphenyl diethyl phosphate, (2,2,2-trifluoroethyl)(2,2,3,3-tetrafluoropropyl) methyl phosphate, methyl 2-(dimethoxyphosphoryl)acetate, methyl 2-(dimethylphosphoryl)acetate, methyl 2-(diethoxyphosphoryl)acetate, methyl 2-(diethylphosphoryl)acetate, methylenebisphosphonic acid methyl, methylenebisphosphonic acid ethyl, ethylenebisphosphonic acid methyl, ethylenebisphosphonic acid ethyl, butylenebisphosphonic acid methyl, butylenebisphosphonic acid ethyl, 2-propynyl 2-(dimethoxyphosphoryl)acetate, 2-propynyl 2-(dimethylphosphoryl)acetate, 2-propynyl 2-(diethoxyphosphoryl)acetate, 2-propynyl 2-(diethylphosphoryl)acetate, tris(trimethylsilyl) phosphate, tris(triethylsilyl) phosphate, tris(trimethoxysilyl) phosphate, tris(trimethylsilyl) phosphite, tris(triethylsilyl) phosphite, tris(trimethoxysilyl) phosphite, trimethylsilyl polyphosphate and other phosphorus-containing compounds; Boron-containing compounds such as tris(trimethylsilyl) borate and tris(trimethoxysilyl) borate; Silane compounds such as dimethoxyaluminoxytriethoxysilane, diethoxyaluminoxytriethoxysilane, dipropoxyaluminoxytriethoxysilane, dibutoxyaluminoxytriethoxysilane, dibutoxyaluminoxytriethoxysilane, titanium tetrakis(trimethylsiloxide), titanium tetrakis(triethylsiloxide), and tetramethylsilane; And the like. These may be used alone or in combination of two or more. By adding these auxiliaries, the capacity retention characteristics and cycle characteristics after high-temperature storage can be improved. Among the above-mentioned other auxiliaries, phosphorus-containing compounds are particularly preferred, and tris(trimethylsilyl) phosphate and tris(trimethylsilyl) phosphite are preferred.

[0392] The blending amount of the other auxiliaries is not particularly limited and is arbitrary as long as the effects of the present disclosure are not significantly impaired. The other auxiliaries are preferably 0.01% by mass or more and 5% by mass or less in 100% by mass of the electrolyte. Within this range, it is easy to sufficiently exhibit the effects of the other auxiliaries, and it is also easy to avoid situations such as deterioration of battery characteristics such as high-load discharge characteristics. The blending amount of the other auxiliaries is more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, and more preferably 3% by mass or less, still more preferably 1% by mass or less.

[0393] The electrolyte of the present disclosure may further contain, as additives, cyclic and chain carboxylic acid esters, ether compounds, nitrogen-containing compounds, boron-containing compounds, organosilicon-containing compounds, flame-retardant (fire-retardant) agents, surfactants, high-dielectric additives, cycle characteristic and rate characteristic improvers, sulfone-based compounds, etc., within the range that does not impair the effects of the present disclosure.

[0394] Examples of the cyclic carboxylic acid ester include those having 3 to 12 carbon atoms in total in the structural formula. Specifically, examples include gamma-butyrolactone, gamma-valerolactone, gamma-caprolactone, epsilon-caprolactone, 3-methyl-gamma-butyrolactone, and the like. Among them, gamma-butyrolactone is particularly preferred from the viewpoint of improving the characteristics of the electrochemical device due to the improvement of the lithium ion dissociation degree.

[0395] The blending amount of the cyclic carboxylic acid ester as an additive is usually preferably 0.1% by mass or more, more preferably 1% by mass or more in 100% by mass of the solvent. When it is within this range, the electrical conductivity of the electrolytic solution is improved, and it becomes easier to improve the large current discharge characteristics of the electrochemical device. Further, the blending amount of the cyclic carboxylic acid ester is preferably 10% by mass or less, more preferably 5% by mass or less. By setting the upper limit in this way, the viscosity of the electrolytic solution is made appropriate, a decrease in electrical conductivity is avoided, an increase in negative electrode resistance is suppressed, and it becomes easier to make the large current discharge characteristics of the electrochemical device within a good range.

[0396] Further, as the cyclic carboxylic acid ester, a fluorinated cyclic carboxylic acid ester (fluorine-containing lactone) can also be preferably used. Examples of the fluorine-containing lactone include the following formula (C):

[0397]

Chemical formula

[0398] (In the formula, X 15 ~X 20 are the same or different and are each -H, -F, -Cl, -CH3 or a fluorinated alkyl group; provided that at least one of X 15 ~X 20 is a fluorinated alkyl group) Examples of the fluorine-containing lactone represented by the formula include those.

[0399] X 15 ~X 20Examples of the fluorinated alkyl group include -CFH2, -CF2H, -CF3, -CH2CF3, -CF2CF3, -CH2CF2CF3, -CF(CF3)2, etc. From the viewpoint of high oxidation resistance and the effect of improving safety, -CH2CF3 and -CH2CF2CF3 are preferred.

[0400] X 15 ~X 20 If at least one of ~X is a fluorinated alkyl group, -H, -F, -Cl, -CH3 or a fluorinated alkyl group may be substituted at only one position of X 15 ~X 20 or may be substituted at a plurality of positions. Preferably, it is 1 to 3 positions, more preferably 1 to 2 positions, from the viewpoint of good solubility of the electrolyte salt.

[0401] The substitution position of the fluorinated alkyl group is not particularly limited, but from the viewpoint of good synthesis yield, X 17 and / or X 18 is particularly preferably X 17 or X 18 being a fluorinated alkyl group, especially -CH2CF3 or -CH2CF2CF3. X other than the fluorinated alkyl group 15 ~X 20 is -H, -F, -Cl or CH3, and -H is particularly preferred from the viewpoint of good solubility of the electrolyte salt.

[0402] Examples of the fluorinated lactone include, in addition to those represented by the above formula, for example, the following formula (D):

[0403]

Chemical formula

[0404] (In the formula, either A or B is CX 226 X 227 (X 226 and X 227is the same or different and is each an alkylene group which may be -H, -F, -Cl, -CF3, -CH3 or a hydrogen atom substituted by a halogen atom and may contain a hetero atom in the chain), and the other is an oxygen atom; Rf 12 is a fluorinated alkyl group or a fluorinated alkoxy group which may have an ether bond; X 221 and X 222 is the same or different and is each -H, -F, -Cl, -CF3 or CH3; X 223 ~X 225 is the same or different and is each -H, -F, -Cl or an alkyl group which may be a hydrogen atom substituted by a halogen atom and may contain a hetero atom in the chain; n = 0 or 1) Examples also include fluorinated lactones represented by .

[0405] As the fluorinated lactone represented by formula (D), the following formula (E):

[0406]

Chemical formula

[0407] (In the formula, A, B, Rf 12 , X 221 , X 222 and X 223 are the same as those in formula (D)) The 5-membered ring structure represented by is preferably mentioned in terms of easy synthesis and good chemical stability. Furthermore, depending on the combination of A and B, the following formula (F):

[0408]

Chemical formula

[0409] (In the formula, Rf 12 , X 221 , X 222 , X 223 , X 226 and X 227 are the same as those in formula (D)) The fluorinated lactone represented by and the following formula (G):

[0410] [Chemical formula]

[0411] (wherein, Rf 12 , X 221 , X 222 , X 223 , X 226 and X 227 are the same as formula (D)) There is a fluorine-containing lactone represented by .

[0412] Among these, from the viewpoints that excellent characteristics such as a high dielectric constant and a high breakdown voltage can be particularly exhibited, and that the solubility of the electrolyte salt and the reduction of the internal resistance are good, the characteristics as the electrolytic solution in the present disclosure are improved.

[0413] [Chemical formula] etc. can be mentioned. By containing a fluorinated cyclic carboxylic acid ester, effects such as an improvement in ionic conductivity, an improvement in safety, and an improvement in stability at high temperatures can be obtained.

[0414] Examples of the above 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, isobutyl propionate, n-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, n-propyl isobutyrate, isopropyl isobutyrate, etc. can be mentioned.

[0415] Among them, 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 viewpoint of improving ionic conductivity due to a decrease in viscosity.

[0416] As the above ether compound, a chain ether having 2 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms are preferable. Examples of the chain ether having 2 to 10 carbon atoms include dimethyl ether, diethyl ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, diethoxymethane, dimethoxyethane, methoxyethoxyethane, diethoxyethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol, diethylene glycol dimethyl ether, pentaethylene glycol, triethylene glycol dimethyl ether, triethylene glycol, tetraethylene glycol, tetraethylene glycol dimethyl ether, diisopropyl ether and the like.

[0417] In addition, as the above ether compound, a fluorinated ether (excluding the fluorine-containing ether compounds (1) and (2)) can also be preferably used. As the above fluorinated ether, the following general formula (I): Rf 3 -O-Rf 4 (I) (In the formula, Rf 3 and Rf 4 are the same or different and are an alkyl group having 1 to 10 carbon atoms or a fluorinated alkyl group having 1 to 10 carbon atoms. However, at least one of Rf 3 and Rf 4 is a fluorinated alkyl group.) The fluorinated ether (I) represented by the formula can be mentioned. By containing the fluorinated ether (I), the flame retardancy of the electrolytic solution is improved, and the stability and safety at high temperature and high voltage are improved.

[0418] In the above general formula (I), Rf3 and Rf 4 At least one of them may be a fluorinated alkyl group having 1 to 10 carbon atoms. However, from the viewpoint of further improving the flame retardancy, stability at high temperature and high voltage, and safety of the electrolytic solution, Rf 3 and Rf 4 are preferably both fluorinated alkyl groups having 1 to 10 carbon atoms. In this case, Rf 3 and Rf 4 may be the same or different from each other. Among them, Rf 3 and Rf 4 are the same or different, Rf 3 is a fluorinated alkyl group having 3 to 6 carbon atoms, and Rf 4 is more preferably a fluorinated alkyl group having 2 to 6 carbon atoms.

[0419] Rf 3 and Rf 4 If the total carbon number of Rf 3 and Rf 4 is too small, the boiling point of the fluorinated ether will be too low. Also, if the carbon number of Rf 3 or Rf 4 is too large, the solubility of the electrolyte salt will decrease, and the compatibility with other solvents will also start to be adversely affected, and the viscosity will increase, resulting in a reduction in rate characteristics. When the carbon number of Rf 3 is 3 or 4, and the carbon number of Rf 4 is 2 or 3, it is advantageous in terms of excellent boiling point and rate characteristics.

[0420] The above-mentioned fluorinated ether (I) preferably has a fluorine content of 40 to 75% by mass. When it has a fluorine content in this range, it will be particularly excellent in the balance between non-flammability and compatibility. Also, it is preferable from the viewpoints of good oxidation resistance and safety. The lower limit of the above-mentioned fluorine content is more preferably 45% by mass, further preferably 50% by mass, and particularly preferably 55% by mass. The upper limit is more preferably 70% by mass, and further preferably 66% by mass. Incidentally, the fluorine content of the fluorinated ether (I) is a value calculated by {(the number of fluorine atoms × 19) / the molecular weight of the fluorinated ether (I)} × 100 (%) based on the structural formula of the fluorinated ether (I).

[0421] Rf 3 Examples of Rf include, for example, CF3CF2CH2-, CF3CFHCF2-, HCF2CF2CF2-, HCF2CF2CH2-, CF3CF2CH2CH2-, CF3CFHCF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CF2CH2-, HCF2CF2CH2CH2-, HCF2CF(CF3)CH2-, etc. Also, Rf 4 Examples of Rf include, for example, -CH2CF2CF3, -CF2CFHCF3, -CF2CF2CF2H, -CH2CF2CF2H, -CH2CH2CF2CF3, -CH2CF2CFHCF3, -CF2CF2CF2CF2H, -CH2CF2CF2CF2H, -CH2CH2CF2CF2H, -CH2CF(CF3)CF2H, -CF2CF2H, -CH2CF2H, -CF2CH3, etc.

[0422] Specific examples of the fluorinated ether (I) include, for example, CF3CF2CH2OCF2CF2H, CF3CF2CH2OCF2CFHCF3, C6F 13 OCH3, C6F 13 OC2H5, C8F 17 OCH3, C8F 17 OC2H5, CF3CFHCF2CH(CH3)OCF2CFHCF3, HCF2CF2OCH(C2H5)2, HCF2CF2OC4H9, HCF2CF2OCH2CH(C2H5)2, HCF2CF2OCH2CH(CH3)2, etc.

[0423] Among them, those containing HCF2- or CF3CFH- at one end or both ends are excellent in polarity and can give a fluorinated ether (I) with a high boiling point. The boiling point of the fluorinated ether (I) is preferably 67 to 120 °C. More preferably 80 °C or higher, and still more preferably 90 °C or higher.

[0424] Examples of such fluorinated ethers (I) include one or more of CF3CH2OCF2CFHCF3, CF3CF2CH2OCF2CFHCF3, HCF2CF2CH2OCH2CF2CF2H, CF3CFHCF2CH2OCF2CFHCF3, CF3CF2CH2OCF2CF2H, etc. Among them, it is preferably at least one selected from the group consisting of CF3CF2CH2OCF2CFHCF3 (boiling point 82°C) and CF3CF2CH2OCF2CF2H (boiling point 68°C) because of their advantages such as high boiling point, good compatibility with other solvents, and good solubility of electrolyte salts.

[0425] Examples of the cyclic ether having 3 to 6 carbon atoms include 1,2-dioxane, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, metaformaldehyde, 2-methyl-1,3-dioxolane, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 2-(trifluoroethyl)dioxolane, 2,2,-bis(trifluoromethyl)-1,3-dioxolane, etc., and fluorinated compounds thereof. Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol - n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, and crown ether are preferable in terms of high solvating ability to lithium ions and improvement of ion dissociation degree. Particularly preferably, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are preferred because of their low viscosity and high ion conductivity.

[0426] Examples of the nitrogen-containing compound include nitrile, fluorine-containing nitrile, carboxylic acid amide, fluorine-containing carboxylic acid amide, sulfonic acid amide, fluorine-containing sulfonic acid amide, acetamide, formamide, etc. Further, 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, N-methylsuccinimide, etc. can also be used. However, the nitrile compounds represented by the above general formulas (1a), (1b) and (1c) shall not be included in the above nitrogen-containing compounds.

[0427] Examples of the boron-containing compound include boric acid esters such as trimethyl borate and triethyl borate, boric acid ethers, and alkyl borates.

[0428] Examples of the organosilicon-containing compound include (CH3)4-Si, (CH3)3-Si-Si(CH3)3, silicone oil, etc.

[0429] Examples of the nonflammable (flame-retardant) agent include phosphate esters and phosphazene-based compounds. Examples of the phosphate ester include fluorine-containing alkyl phosphate esters, non-fluorine-based alkyl phosphate esters, aryl phosphate esters, etc. Among them, a fluorine-containing alkyl phosphate ester is preferable in that it can exhibit a nonflammable effect in a small amount.

[0430] Examples of the phosphazene-based compound include methoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, dimethylaminopentafluorocyclotriphosphazene, diethylaminopentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, ethoxyheptafluorocyclotetraphosphazene, etc.

[0431] Specific examples of the fluorine-containing alkyl phosphate ester include the fluorine-containing dialkyl phosphate ester described in JP-A-11-233141, the cyclic alkyl phosphate ester described in JP-A-11-283669, and the fluorine-containing trialkyl phosphate ester, etc.

[0432] Preferred examples of the nonflammable (flame-retardant) agent include (CH3O)3P=O, (CF3CH2O)3P=O, (HCF2CH2O)3P=O, (CF3CF2CH2)3P=O, (HCF2CF2CH2)3P=O, etc.

[0433] As the surfactant, any of a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant may be used, but from the viewpoint of good cycle characteristics and rate characteristics, it is preferably one containing a fluorine atom.

[0434] Examples of such a surfactant containing a fluorine atom include the following formula (30): Rf 5 COO - M + (30) (In the formula, Rf 5 is a fluorine-containing alkyl group which may contain an ether bond having 3 to 10 carbon atoms; M + is Li + , Na + , K + or NHR’3 + (R’ is the same or different and is each H or an alkyl group having 1 to 3 carbon atoms)) a fluorine-containing carboxylate represented by the formula, and the following formula (40): Rf 6 SO3 - M + (40) (In the formula, Rf 6 is a fluorine-containing alkyl group which may contain an ether bond having 3 to 10 carbon atoms; M + is Li + , Na + , K + or NHR’3 +(R’ is the same or different, and each is H or an alkyl group having 1 to 3 carbon atoms) Fluorine-containing sulfonates represented by the formula are preferred.

[0435] The content of the surfactant is preferably 0.01 to 2% by mass in the electrolytic solution in that it can lower the surface tension of the electrolytic solution without degrading the charge-discharge cycle characteristics.

[0436] Examples of the high-dielectric additive include sulfolane, methylsulfolane, γ-butyrolactone, γ-valerolactone, and the like.

[0437] Examples of the cycle characteristics and rate characteristics improver include methyl acetate, ethyl acetate, tetrahydrofuran, 1,4-dioxane, and the like.

[0438] In addition, the electrolytic solution of the present disclosure may be further combined with a polymer material to form a gel-like (plasticized) gel electrolyte.

[0439] Examples of such polymer materials include conventionally known polyethylene oxide, polypropylene oxide, and modified products thereof (Japanese Patent Laid-Open No. 8-222270, Japanese Patent Laid-Open No. 2002-100405); polyacrylate-based polymers, polyacrylonitrile, fluororesins such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer (Japanese Patent Publication No. 4-506726, Japanese Patent Publication No. 8-507407, Japanese Patent Laid-Open No. 10-294131); composites of these fluororesins and hydrocarbon resins (Japanese Patent Laid-Open No. 11-35765, Japanese Patent Laid-Open No. 11-86630), and the like. In particular, it is desirable to use polyvinylidene fluoride or vinylidene fluoride-hexafluoropropylene copolymer as the polymer material for the gel electrolyte.

[0440] In addition, the electrolytic solution of the present disclosure may also contain an ion conductive compound described in the specification of Japanese Patent Application No. 2004-301934.

[0441] This ionic conductive compound has the formula (101): A-(D)-B (101) [wherein, D is the formula (201): -(D1) n -(FAE) m -(AE) p -(Y) q - (201) (wherein, D1 is the formula (2a):

[0442]

Chemical formula

[0443] (wherein, Rf is a fluorine-containing ether group which may have a crosslinkable functional group; R 10 is a group or a bond that binds Rf to the main chain) an ether unit having a fluorine-containing ether group in the side chain represented by; FAE is the formula (2b):

[0444]

Chemical formula

[0445] (wherein, Rfa is a hydrogen atom, a fluorinated alkyl group which may have a crosslinkable functional group; R 11 is a group or a bond that binds Rfa to the main chain) an ether unit having a fluorinated alkyl group in the side chain represented by; AE is the formula (2c):

[0446]

Chemical formula

[0447] (wherein, R 13 is a hydrogen atom, an alkyl group which may have a crosslinkable functional group, an aliphatic cyclic hydrocarbon group which may have a crosslinkable functional group or an aromatic hydrocarbon group which may have a crosslinkable functional group; R 12 is a group or a bond that binds R 13 to the main chain) the ether unit represented by; Y is a unit containing at least one of the formulas (2d-1) to (2d-3):

[0448] [Chemical formula]

[0449] a unit containing at least one of; n is an integer from 0 to 200; m is an integer from 0 to 200; p is an integer from 0 to 10000; q is an integer from 1 to 100; provided that n + m is not 0, and the bonding order of D1, FAE, AE, and Y is not specified); A and B are the same or different, and may be a hydrogen atom, an alkyl group which may contain a fluorine atom and / or a crosslinkable functional group, a phenyl group which may contain a fluorine atom and / or a crosslinkable functional group, -COOH group, -OR (R is a hydrogen atom or an alkyl group which may contain a fluorine atom and / or a crosslinkable functional group), an ester group or a carbonate group (however, when the terminal of D is an oxygen atom, it is not a -COOH group, -OR, ester group, and carbonate group)] It is an amorphous fluorine-containing polyether compound having a fluorine-containing group in the side chain represented by.

[0450] The electrolytic solution of the present disclosure may contain a sulfone compound. As the sulfone compound, a cyclic sulfone having 3 to 6 carbon atoms and a linear sulfone having 2 to 6 carbon atoms are preferable. The number of sulfonyl groups in one molecule is preferably 1 or 2.

[0451] Examples of the cyclic sulfone include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones which are monosulfone compounds; trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones which are disulfone compounds, and the like. Among them, from the viewpoints of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable.

[0452] As the sulfolanes, sulfolane and / or sulfolane derivatives (hereinafter, may be abbreviated as "sulfolanes" including sulfolane) are preferred. As the sulfolane derivatives, those in which one or more of the hydrogen atoms bonded to the carbon atoms constituting the sulfolane ring are substituted with fluorine atoms or alkyl groups are preferred.

[0453] Among them, 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, 3-sulfolene, 5-fluoro-3-(trifluoromethyl)sulfolane, etc. are preferred in terms of high ionic conductivity and high input / output.

[0454] 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.

[0455] Among them, 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.

[0456] The content of the sulfone-based compound is not particularly limited and can be arbitrary as long as the effects of the present disclosure are not significantly impaired. However, in 100% by volume of the above 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. When the content of the sulfone-based compound is within the above range, the effect of improving the durability such as cycle characteristics and storage characteristics can be easily obtained, and the viscosity of the non-aqueous electrolyte can be set within an appropriate range to avoid a decrease in electrical conductivity, and the input / output characteristics and charge / discharge rate characteristics of the non-aqueous electrolyte secondary battery can be set within an appropriate range.

[0457] From the viewpoint of improving the output characteristics, the electrolyte of the present disclosure preferably contains at least one compound (7) selected from the group consisting of lithium fluorophosphate salts (excluding LiPF6) and lithium salts having an S=O group as an additive. When using the compound (7) as an additive, it is preferable to use a compound other than the compound (7) as the above-described electrolyte salt.

[0458] Examples of the lithium fluorophosphate salts include lithium monofluorophosphate (LiPO3F), lithium difluorophosphate (LiPO2F2), and the like. Examples of the lithium salts having the S=O group include lithium monofluorosulfonate (FSO3Li), lithium methyl sulfate (CH3OSO3Li), lithium ethyl sulfate (C2H5OSO3Li), lithium 2,2,2-trifluoroethyl sulfate, and the like. Among the compounds (7), LiPO2F2, FSO3Li, and C2H5OSO3Li are preferred.

[0459] The content of the compound (7) is preferably 0.001 to 20% by mass, more preferably 0.01 to 15% by mass, still more preferably 0.1 to 10% by mass, and particularly preferably 0.1 to 7% by mass with respect to the above electrolytic solution.

[0460] Other additives may be further blended in the electrolytic solution of the present disclosure as needed. Examples of the other additives include metal oxides, glass, and the like.

[0461] The electrolytic solution of the present disclosure preferably contains at least one selected from the group consisting of an unsaturated cyclic carbonate, a compound (2), a nitrile compound, a fluorinated saturated cyclic carbonate, a lithium salt having an S=O group, a lithium imide salt (excluding lithium bis(fluorosulfonyl)imide), a lithium fluorophosphate salt (excluding LiPF6), a lithium sulfamate compound, a compound (5), and a silyl ester compound of phosphoric acid or phosphorous acid as an additive. By containing these additives, the remaining capacity after high-temperature storage can be further improved, and the gas generation amount can be further reduced. The above additives include unsaturated cyclic carbonates, compound (3), compound (4), nitrile compounds represented by general formula (1a), fluorinated saturated cyclic carbonates, lithium alkyl sulfate compounds, lithium sulfonate compounds, lithium difluorophosphate (LiPO2F2), lithium sulfamate compounds represented by the following general formula (11), lithium bis(oxalato)borate (LIBOB), lithium difluorooxalatoborate (LIDFOB), and M 301 (OSiR 301 3)3(M 301 is P or P=O, and R 301 is independently an alkyl group having 1 to 4 carbon atoms), and it is preferably at least one selected from the group consisting of phosphoric acid or phosphorous acid silyl ester compounds represented by the formula, Vinylene carbonate, vinyl ethylene carbonate, succinic anhydride, maleic anhydride, adiponitrile, fluoroethylene carbonate, difluoroethylene carbonate, C2H5OSO3Li, FSO3Li, LiPO2F2, (CH3CH2)2NSO3Li, (CF3CH2)2NSO3Li, (CF3CH2)(CH3)NSO3Li, (CNCH2)2NSO3Li, LIBOB, LIDFOB, tris(trimethylsilyl) phosphate, tris(triethylsilyl) phosphate, tris(tert-butyldimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, tris(triethylsilyl) phosphite, and tris(tert-butyldimethylsilyl) phosphite, and it is more preferably at least one selected from the group consisting of these. The content of the above lithium sulfamate compound is preferably 0.001 to 5.0% by mass with respect to the electrolytic solution. More preferably, it is 0.01% by mass or more, still more preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more. Also, more preferably, it is 3.0% by mass or less, still more preferably 2.0% by mass or less, particularly preferably 1.5% by mass or less. General formula (11):

Chemical formula

[0462] Hereinafter, the lithium sulfamate compound represented by the general formula (11) (compound (11)) will be described.

[0463] Compound (11) has the general formula (11): [Chemical formula] It is represented by

[0464] In the general formula (11), R 111 and R 112 are each independently -H, -F, Formula: -O p101 -(SiR 113 2O) n101 -SiR 114 3(R 113 and R 114 are, independently of each other, an alkyl group in which one or more hydrogen atoms may be substituted by fluorine atoms, an alkenyl group in which one or more hydrogen atoms may be substituted by fluorine atoms, an alkynyl group in which one or more hydrogen atoms may be substituted by fluorine atoms, or an aryl group in which one or more hydrogen atoms may be substituted by fluorine atoms, n101 is an integer of 0 or more, and p101 is 0 or 1. A group represented by An alkyl group having 1 to 7 carbon atoms, An alkenyl group having 2 to 7 carbon atoms, An alkynyl group having 2 to 7 carbon atoms, An aryl group having 6 to 15 carbon atoms, -SO2X 101 (X 101 is -H, -F, or an alkyl group in which one or more hydrogen atoms may be substituted by fluorine atoms. -SO3X 102 (X 102 is -H, -F, or an alkyl group in which one or more hydrogen atoms may be substituted by fluorine atoms. R 111 and R 112 are substituents that combine to form a cyclic structure and may contain a multiple bond in the cyclic structure, a hydrocarbon group having 2 to 7 carbon atoms, The above substituents may contain one or more divalent to hexavalent heteroatoms in their structures, and one or more hydrogen atoms may be substituted by fluorine or a functional group having 0 to 7 carbon atoms. Note that the number of carbon atoms of each of the above substituents means the number of carbon atoms including the number of carbon atoms of the above functional group.

[0465] The above substituents are -H, -F, the above formula: -O p101 -(SiR 113 2O) n101 -SiR 114 3, the groups represented by the above, the above alkyl group, the above alkenyl group, the above alkynyl group, the above aryl group, the above -SO2X 101 and the above -SO3X 102 or represent the above hydrocarbon group. The above substituents may contain one or more divalent to hexavalent heteroatoms in their structures, and one or more hydrogen atoms may be substituted by fluorine or a functional group having 0 to 7 carbon atoms. Examples of the functional groups that the above substituents may have include, for example, a phenyl group, an anisyl group, a benzyl group, a cyano group, a trialkylsilyl group (the number of carbon atoms of the alkyl group is preferably 1 to 4), -SO2X 103 (X 103 is -H, -F, or an alkyl group in which one or more hydrogen atoms may be substituted by fluorine atoms.), an alkyl group having 1 to 7 carbon atoms in which one or more hydrogen atoms may be substituted by fluorine atoms, a saturated heterocyclic group having 1 to 7 carbon atoms, or an alkoxy group having 1 to 7 carbon atoms is preferable. The number of carbon atoms of the alkyl group in the above X 103 is, for example, 1 to 10.

[0466] In the above R 111 and R 112 , the alkyl group may be linear, branched, or cyclic, and the number of carbon atoms is preferably 1 to 10, more preferably 1 to 7. The alkyl group may be a fluoroalkyl group in which a hydrogen atom bonded to carbon is substituted by a fluorine atom, or may be one in which a hydrogen atom bonded to carbon is substituted by the above functional group.

[0467] In the above R 111 and R 112In this case, the alkenyl group may be linear, branched or cyclic, preferably having 2 to 10 carbon atoms, more preferably 2 to 7 carbon atoms. The alkenyl group may be a fluoroalkenyl group in which a hydrogen atom bonded to carbon is substituted with a fluorine atom, or may be one in which a hydrogen atom bonded to carbon is substituted with the above functional group.

[0468] The above R 111 and R 112 In this case, the alkynyl group may be linear, branched or cyclic, preferably having 2 to 10 carbon atoms, more preferably 2 to 7 carbon atoms. The alkynyl group may be a fluoroalkynyl group in which a hydrogen atom bonded to carbon is substituted with a fluorine atom, or may be one in which a hydrogen atom bonded to carbon is substituted with the above functional group.

[0469] The above R 111 and R 112 In this case, the aryl group preferably has 6 to 7 carbon atoms. The aryl group may be a fluoroaryl group in which a hydrogen atom bonded to carbon is substituted with a fluorine atom, or may be one in which a hydrogen atom bonded to carbon is substituted with the above functional group.

[0470] The above R 111 and R 112 are of the formula: -O p101 -(SiR 113 2O) n101 -SiR 114 3(R 113 and R 114 are, independently of each other, an alkyl group in which one or more hydrogen atoms may be substituted with fluorine atoms, an alkenyl group in which one or more hydrogen atoms may be substituted with fluorine atoms, an alkynyl group in which one or more hydrogen atoms may be substituted with fluorine atoms or an aryl group in which one or more hydrogen atoms may be substituted with fluorine atoms, n101 is an integer of 0 or more, and p101 is 0 or 1. ) may be a group represented by The above R 113 and R 114In this case, the alkyl group in which one or more hydrogen atoms may be substituted by fluorine atoms preferably has 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms. The alkenyl group and alkynyl group in which one or more hydrogen atoms may be substituted by fluorine atoms preferably have 2 to 10 carbon atoms, more preferably 2 to 7 carbon atoms. The aryl group in which one or more hydrogen atoms may be substituted by fluorine atoms preferably has 6 to 8 carbon atoms, more preferably 6 to 7 carbon atoms. In the above formula, n101 is an integer of 0 or more, preferably 2000 or less, more preferably an integer of 0 to 100, and even more preferably 0 to 10.

[0471] The above R 111 and R 112 may be -SO2X 101 (X 101 is -H, -F, or an alkyl group in which one or more hydrogen atoms may be substituted by fluorine atoms.). The alkyl group in the above -SO2X 101 group preferably has 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms.

[0472] The above R 111 and R 112 may be -SO3X 102 (X 102 is -H, -F, or an alkyl group in which one or more hydrogen atoms may be substituted by fluorine atoms.). The alkyl group in the above -SO3X 102 group preferably has 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms.

[0473] The above R 111 and R 112Specific examples thereof include chain alkyl groups such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, tert-butyl group, pentyl group, i-pentyl group, neopentyl group, sec-pentyl group, 3-pentyl group, tert-pentyl group, hexyl group; cyclic alkyl groups such as cyclopentyl group, cyclohexyl group, norbornyl group, 1-adamantyl group; alkenyl groups such as vinyl group, 1-propenyl group, 2-propenyl group (allyl group), 2-butenyl group, 1,3-butadienyl group; alkynyl groups such as ethynyl group, 1-propynyl group, 2-propynyl group, 2-butynyl group; halogenated alkyl groups such as trifluoromethyl group, 2,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, pentafluoroethyl group, 2,2,3,3,3-pentafluoropropyl group, 1,1,2,3,3,3-hexafluoropropyl group, heptafluoropropyl group; halogenated alkenyl groups such as 1-fluorovinyl group, 2-fluoroallyl group; alkyl groups having a functional group such as cyanomethyl group, alkyl groups having a saturated heterocyclic group such as 3-pyrrolidinopropyl group; aryl groups such as phenyl group which may have an alkyl substituent, an alkoxy substituent, etc.; aralkyl groups such as phenylmethyl group, phenylethyl group; trialkylsilyl groups such as trimethylsilyl group; trialkylsiloxy groups such as trimethylsiloxy group; sulfonyl groups such as fluorosulfonyl group, trifluoromethanesulfonyl group, pentafluoroethanesulfonyl group, etc., but are not limited thereto.

[0474] Also, when R 111 and R 112 are bonded to form a cyclic structure, for example, the nitrogen atom (N) in the general formula (2), R 111 and R 112It may form a cyclic amino group such as a pyrrolidino group or a piperidino group, or may form a heteroatom-containing heterocyclic amino group such as a 4-morpholino group, a succinimidyl group, or a maleimidyl group. These may have one or more hydrogen atoms bonded to carbon substituted with fluorine atoms, or may be those in which the hydrogen atoms bonded to carbon are substituted with the above functional groups. Further, the cyclic structure may contain a double bond or a triple bond.

[0475] The above substituents may contain a heteroatom with a valence of 2 to 6. Examples of the heteroatom include an oxygen atom (O), a sulfur atom (S), a nitrogen atom (N), a silicon atom (Si), a phosphorus atom (P), and a boron atom (B). More preferably, it is an oxygen atom, a sulfur atom, or a nitrogen atom.

[0476] R 111 and R 112 are preferably an alkyl group having 1 to 7 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms, and still more preferably an alkyl group having 1 to 4 carbon atoms. These alkyl groups may contain one or more heteroatoms with a valence of 2 to 6 in the structure, and one or more hydrogen atoms may be substituted with fluorine atoms or a functional group having 0 to 6 carbon atoms (preferably 0 to 4, more preferably 0 to 3). As the above heteroatom, an oxygen atom, a sulfur atom, or a nitrogen atom is preferable, an oxygen atom or a nitrogen atom is more preferable, and a nitrogen atom is still more preferable. The above alkyl group may contain an ether bond (-O-). As the above functional group, a cyano group is preferable.

[0477] Examples of the compound (11) include compounds represented by the following formula.

Chemical formula

Chemical formula

Chemical formula

[0478] In this specification, Me represents a methyl group, Et represents an ethyl group, n-Pr represents a normal propyl group, i-Pr represents an isopropyl group, n-Bu represents a normal butyl group, i-Bu represents an iso-butyl group, s-Bu represents a sec-butyl group, t-Bu represents a tert-butyl group, TMS represents a trimethylsilyl group, and TBDMS represents a tert-butyldimethylsilyl group. Also, when described as follows, R may be bonded to any carbon atom constituting the benzene ring. For example, R may be at any of the o-, m-, and p- positions. [Chemistry] Note that the exemplification of the compounds in this specification includes the geometric isomers (if any) of the compounds and is not limited to the specific examples described.

[0479] Among others, as the compound (11), the compound represented by the following formula is preferable. [Chemistry]

[0480] As the compound (11), a compound represented by the following formula is more preferable. [Chemical formula]

[0481] As the compound (11), a compound represented by the following formula is even more preferable. [Chemical formula]

[0482] The compound (11) may be a compound represented by the following general formula (11a) (hereinafter, also referred to as compound (11a)). General formula (11a): [Chemical formula] (In the formula, R 201 and R 202 are each independently -H, -F, Formula: -O p101 -(SiR 113 2O) n101 -SiR 114 3(R 113 and R 114 are, independently of each other, an alkyl group in which one or more hydrogen atoms may be substituted with fluorine atoms, an alkenyl group in which one or more hydrogen atoms may be substituted with fluorine atoms, an alkynyl group in which one or more hydrogen atoms may be substituted with fluorine atoms, or an aryl group in which one or more hydrogen atoms may be substituted with fluorine atoms, n101 is an integer of 0 or more, and p101 is 0 or 1.), an alkyl group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms, an alkynyl group having 2 to 7 carbon atoms, an aryl group having 6 to 15 carbon atoms, -SO2X 101 (X 101 is -H, -F, or an alkyl group in which one or more hydrogen atoms may be substituted with fluorine atoms.), or -SO3X 102 (X 102 is -H, -F, or an alkyl group in which one or more hydrogen atoms may be substituted by fluorine atoms.) is a substituent, the above substituents may contain one or more divalent to hexavalent heteroatoms in their structures, and one or more hydrogen atoms may be substituted by fluorine or a functional group having 0 to 7 carbon atoms. However, R 201 and R 202 at least one of them is -F.)

[0483] In general formula (11a), it is necessary that at least one of R 201 and R 202 is -F. R in general formula (11a) 201 and R 202 as the above -O p101 -(SiR 113 2O) n101 -SiR 114 3, the above alkyl group, the above alkenyl group, the above alkynyl group, the above aryl group, the above -SO2X 101 and the above -SO3X 102 are the same as R 111 and R 112 in general formula (11).

[0484] As compound (11a), for example, compounds represented by the following formulas can be exemplified.

Chemical formula

[0485] Among others, as compound (11a),

Chemical formula

[0486] Compound (11) can be produced, for example, by the production method described in International Publication No. 2019 / 188207.

[0487] The electrolyte of the present disclosure preferably has a hydrogen fluoride (HF) content of 1 to 1000 ppm. By containing HF, the film formation of the above-described additive can be promoted. If the HF content is too low, the film formation ability on the negative electrode decreases, and the characteristics of the electrochemical device tend to deteriorate. Also, if the HF content is too high, the oxidation resistance of the electrolyte tends to decrease due to the influence of HF. Even if the electrolyte of the present disclosure contains HF within the above range, it does not lower the high-temperature storage recovery capacity rate of the electrochemical device. The HF content is more preferably 5 ppm or more, still more preferably 10 ppm or more, and particularly preferably 20 ppm or more. The HF content is also more preferably 200 ppm or less, still more preferably 100 ppm or less, even more preferably 80 ppm or less, and particularly preferably 50 ppm or less. The HF content can be measured by a neutralization titration method.

[0488] The electrolyte of the present disclosure may be prepared by any method using the above-described components.

[0489] The electrolyte of the present disclosure can be suitably applied to electrochemical devices such as secondary batteries such as lithium-ion secondary batteries, lithium-ion capacitors, hybrid capacitors, and electric double-layer capacitors. Hereinafter, a non-aqueous electrolyte battery using the electrolyte of the present disclosure will be described. The non-aqueous electrolyte battery can adopt a known structure and typically includes a positive electrode and a negative electrode capable of occluding and releasing ions (for example, lithium ions) and the electrolyte of the present disclosure. Such an electrochemical device including the electrolyte of the present disclosure is also one of the present disclosures.

[0490] Examples of the electrochemical device include secondary batteries such as lithium ion secondary batteries, lithium ion capacitors, capacitors (hybrid capacitors, electric double layer capacitors), radical batteries, solar cells (especially dye-sensitized solar cells), lithium ion primary batteries, fuel cells, various electrochemical sensors, electrochromic elements, electrochemical switching elements, aluminum electrolytic capacitors, tantalum electrolytic capacitors, etc. Among them, secondary batteries such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors are preferred. A module including the above electrochemical device is also one aspect of the present disclosure.

[0491] The present disclosure also relates to a secondary battery including the electrolyte of the present disclosure. The above secondary battery preferably includes a positive electrode, a negative electrode, and the above electrolyte. The above secondary battery is preferably a lithium ion secondary battery.

[0492] <Positive Electrode> The positive electrode is composed of a positive electrode active material layer containing a positive electrode active material and a current collector.

[0493] The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Examples thereof include lithium-containing transition metal composite oxides, lithium-containing transition metal phosphate compounds, sulfur-based materials, and conductive polymers. Among them, as the positive electrode active material, lithium-containing transition metal composite oxides and lithium-containing transition metal phosphate compounds are preferred, and in particular, lithium-containing transition metal composite oxides that produce high voltages are preferred.

[0494] As the transition metal of the lithium-containing transition metal composite oxide, V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable. Specific examples include lithium-cobalt composite oxides such as LiCoO2, lithium-nickel composite oxides such as LiNiO2, lithium-manganese composite oxides such as LiMnO2, LiMn2O4, Li2MnO4, etc., and those in which a part of the transition metal atoms that are the main components of these lithium transition metal composite oxides are substituted with other elements such as Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W, etc. Specific examples of the substituted ones include, for example, LiNi 0.5 Mn 0.5 O2, LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.45 Co 0.10 Al 0.45 O2, LiMn 1.8 Al 0.2 O4, LiMn 1.5 Ni 0.5 O4, etc. can be mentioned.

[0495] Among them, as the above lithium-containing transition metal composite oxide, LiMn 1.5 Ni 0.5 O4, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2 are preferable. Among them, in the case of a high voltage of 4.4 V or more, LiMn 1.5 Ni 0.5 O4 is preferable.

[0496] Among them, as the lithium-containing transition metal composite oxide, from the viewpoint of being able to provide a high-capacity lithium-ion secondary battery, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.85 Co 0.10 Al 0.05 O2 is preferable.

[0497] As the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable. Specific examples include, for example, iron phosphates such as LiFePO4, Li3Fe2(PO4)3, LiFeP2O7, cobalt phosphates such as LiCoPO4, and those in which a part of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are substituted with other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc.

[0498] As the lithium-containing transition metal composite oxide, for example, Formula: Li a Mn 2-b M 1 b O4 (wherein, 0.9 ≦ a; 0 ≦ b ≦ 1.5; M 1 is at least one metal selected from the group consisting of Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge) of lithium-manganese spinel composite oxide, Formula: LiNi 1-c M 2 c O2 (wherein, 0 ≦ c ≦ 0.5; M 2 is at least one metal selected from the group consisting of Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge) of lithium-nickel composite oxide, or, Formula: LiCo 1-d M 3d O2 (where 0 ≦ d ≦ 0.5; M 3 is at least one metal selected from the group consisting of Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge). Examples thereof include lithium-cobalt composite oxides represented by the formula.

[0499] Among them, LiCoO2, LiMnO2, LiNiO2, LiMn2O4, LiNi 0.8 Co 0.15 Al 0.05 O2, or LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 are preferred because they can provide a lithium-ion secondary battery with high energy density and high output.

[0500] Other examples of the above positive electrode active materials include LiFePO4, LiNi 0.8 Co 0.2 O2, Li 1.2 Fe 0.4 Mn 0.4 O2, LiNi 0.5 Mn 0.5 O2, LiV3O6, Li2MnO3, and the like.

[0501] Examples of the sulfur-based material include materials containing sulfur atoms, and at least one selected from the group consisting of elemental sulfur, metal sulfides, and organic sulfur compounds is preferred, with elemental sulfur being more preferred. The metal sulfide may be a metal polysulfide. The organic sulfur compound may be an organic polysulfide.

[0502] Examples of the metal sulfide include compounds represented by LiS x (0 < x ≦ 8); compounds represented by Li2S x (0 < x ≦ 8); compounds having a two-dimensional layered structure such as TiS2 and MoS2; Chevrel compounds having a strong three-dimensional skeletal structure represented by the general formula Me x Mo6S8 (Me is various transition metals including Pb, Ag, and Cu), and the like.

[0503] Examples of the organic sulfur compound include carbon sulfide compounds.

[0504] The above organic sulfur compound may be supported on a material having pores such as carbon and used as a carbon composite material. As the sulfur content in the carbon composite material, since the cycle performance is further improved and the overvoltage is further reduced, 10 to 99% by mass is preferable, 20% by mass or more is more preferable, 30% by mass or more is still more preferable, 40% by mass or more is particularly preferable, and 85% by mass or less is preferable for the above carbon composite material. When the above positive electrode active material is the above sulfur simple substance, the sulfur content contained in the above positive electrode active material is equal to the content of the above sulfur simple substance.

[0505] Examples of the conductive polymer include p-doped conductive polymers and n-doped conductive polymers. Examples of the conductive polymer include polyacetylene-based, polyphenylene-based, heterocyclic polymers, ionic polymers, ladder and network polymers.

[0506] In addition, it is preferable to include lithium phosphate in the positive electrode active material because the continuous charging characteristics are improved. There is no limitation on the use of lithium phosphate, but it is preferable to mix and use the above positive electrode active material and lithium phosphate. The amount of lithium phosphate used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more, and preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 5% by mass or less based on the total of the above positive electrode active material and lithium phosphate.

[0507] In addition, a substance having a different composition may be attached to the surface of the positive electrode active material. Examples of the surface-attaching substance include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide, sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

[0508] These surface-attaching substances can be attached to the surface of the positive electrode active material by, for example, a method of dissolving or suspending in a solvent, impregnating and adding to the positive electrode active material, and drying, a method of dissolving or suspending a surface-attaching substance precursor in a solvent, impregnating and adding to the positive electrode active material, and then reacting by heating, etc., a method of adding to a positive electrode active material precursor and simultaneously baking, etc. When carbon is attached, a method of mechanically attaching carbonaceous material in the form of, for example, activated carbon, etc., afterwards can also be used.

[0509] The amount of the surface-attached substance is preferably 0.1 ppm or more, more preferably 1 ppm or more, and even more preferably 10 ppm or more, and preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less, as a lower limit, by mass relative to the positive electrode active material. The surface-attached substance can suppress the oxidation reaction of the electrolyte on the surface of the positive electrode active material, and can improve the battery life, but if the amount of attachment is too small, the effect is not fully manifested, and if it is too large, the ingress and egress of lithium ions is inhibited, and resistance may increase.

[0510] The shape of the particles of the positive electrode active material may be any of the conventional shapes such as block, polyhedron, sphere, oval sphere, plate, needle, column, etc. Primary particles may be aggregated to form secondary particles.

[0511] The tap density of the positive electrode active material is usually 1.5 g / cm 3 More than 2.0 g / cm, preferably 2.0 g / cm 3 More preferably, 2.5 g / cm 3The above is most preferably 3.0 g / cm 3 or more. When the tap density of the positive electrode active material is lower than the above lower limit, the required amount of the dispersion medium increases during the formation of the positive electrode active material layer, and the required amounts of the conductive material and the binder increase, so that the filling rate of the positive electrode active material in the positive electrode active material layer is restricted, and the battery capacity may be restricted. By using a metal composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. Generally, the higher the tap density, the more preferable, and there is no particular upper limit, but usually 4.5 g / cm 3 or less, preferably 4.3 g / cm 3 or less. In the present disclosure, the tap density is the powder packing density (tap density) g / cm when 5 to 10 g of the positive electrode active material powder is put into a 10 ml glass graduated cylinder and tapped 200 times with a stroke of about 20 mm 3 and is determined as such.

[0512] The median diameter d50 of the particles of the positive electrode active material (when the primary particles aggregate to form secondary particles, it is the secondary particle diameter) is preferably 0.3 μm or more, more preferably 0.5 μm or more, still more preferably 0.8 μm or more, and most preferably 1.0 μm or more. Also, it is preferably 30 μm or less, more preferably 27 μm or less, still more preferably 25 μm or less, and most preferably 22 μm or less. If it is less than the above lower limit, it may not be possible to obtain a high tap density product. If it exceeds the upper limit, it takes time for lithium diffusion inside the particles, which may cause a decrease in battery performance or problems such as streaks when preparing the positive electrode of the battery, that is, when slurrying the active material, the conductive material, the binder, etc. with a solvent and coating it in a thin film shape. Here, by mixing two or more kinds of the above positive electrode active materials having different median diameters d50, the fillability during the production of the positive electrode can be further improved.

[0513] In the present disclosure, the median diameter d50 is measured by a known laser diffraction / scattering type particle size distribution measuring device. When using LA-920 manufactured by HORIBA as the particle size distribution meter, as the dispersion medium used for the measurement, an aqueous solution of 0.1 mass% sodium hexametaphosphate is used, and the measurement refractive index 1.24 is set and measured after 5 minutes of ultrasonic dispersion.

[0514] When primary particles aggregate to form secondary particles, the average primary particle diameter of the above positive electrode active material is preferably 0.05 μm or more, more preferably 0.1 μm or more, still more preferably 0.2 μm or more, and the upper limit is preferably 5 μm or less, more preferably 4 μm or less, still more preferably 3 μm or less, and most preferably 2 μm or less. If it exceeds the above upper limit, it is difficult to form spherical secondary particles, which may adversely affect the powder packing property or significantly reduce the specific surface area, resulting in a high possibility of deterioration of battery performance such as output characteristics. Conversely, if it is less than the above lower limit, problems such as poor reversibility of charge and discharge may occur because the crystal is usually underdeveloped.

[0515] In the present disclosure, the primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10,000 times, the longest value of the section by the left and right boundary lines of the primary particles with respect to a horizontal straight line is obtained for any 50 primary particles, and the average value is obtained.

[0516] The BET specific surface area of the positive electrode active material is preferably 0.1 m 2 / g or more, more preferably 0.2 m 2 / g or more, still more preferably 0.3 m 2 / g or more, and the upper limit is preferably 50 m 2 / g or less, more preferably 40 m 2 / g or less, still more preferably 30 m 2 / g or less. If the BET specific surface area is smaller than this range, the battery performance is likely to deteriorate. If it is larger, it is difficult to increase the tap density, and problems may easily occur in the coatability during the formation of the positive electrode active material layer.

[0517] In the present disclosure, the BET specific surface area is defined as the value measured by the nitrogen adsorption BET one-point method by the gas flow method using a nitrogen-helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen to atmospheric pressure becomes 0.3 after preliminary drying the sample at 150 °C for 30 minutes under nitrogen flow using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken Co., Ltd.).

[0518] When the secondary battery of the present disclosure is used as a large lithium-ion secondary battery for hybrid vehicles or distributed power sources, high output is required. Therefore, it is preferable that the particles of the positive electrode active material are mainly secondary particles. The particles of the positive electrode active material preferably contain fine particles having an average particle diameter of the secondary particles of 40 μm or less and an average primary particle diameter of 1 μm or less in an amount of 0.5 to 7.0% by volume. By containing fine particles having an average primary particle diameter of 1 μm or less, the contact area with the electrolyte increases, and the diffusion of lithium ions between the electrode and the electrolyte can be made faster. As a result, the output performance of the battery can be improved.

[0519] As a method for manufacturing the positive electrode active material, a method generally used as a method for manufacturing inorganic compounds is used. In particular, various methods can be considered for creating spherical or elliptical spherical active materials. For example, a raw material substance of a transition metal is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to create and recover a spherical precursor, which is dried if necessary, and then a Li source such as LiOH, Li2CO3, LiNO3, etc. is added and fired at a high temperature to obtain an active material, and the like can be mentioned.

[0520] For the manufacture of the positive electrode, the above positive electrode active material may be used alone, or two or more kinds having different compositions may be used in combination in any combination or ratio. Preferred combinations in this case include combinations with LiMn2O4 such as LiCoO2 and LiNi 0.33 Co 0.33 Mn 0.33 O2 or a combination with a substance obtained by substituting a part of this Mn with another transition metal or the like, or a combination with LiCoO2 or a substance obtained by substituting a part of this Co with another transition metal or the like.

[0521] The content of the above positive electrode active material is preferably 50 to 99.5% by mass, more preferably 80 to 99% by mass, of the positive electrode mixture in terms of high battery capacity. Further, the content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. The upper limit is preferably 99% by mass or less, more preferably 98% by mass or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the electric capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

[0522] The above positive electrode mixture preferably further contains a binder, a thickener, and a conductive material. As the above binder, any material can be used as long as it is safe for the solvent and electrolyte used during electrode manufacturing. For example, resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, chitosan, alginic acid, polyacrylic acid, polyimide, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (acrylonitrile-butadiene rubber), and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers or their hydrogenated products; thermoplastic elastomer-like polymers such as EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-styrene copolymer, styrene-isoprene-styrene block copolymer or their hydrogenated products; 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, polytetrafluoroethylene, vinylidene fluoride copolymer, and tetrafluoroethylene-ethylene copolymer; polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions), etc. can be mentioned. These may be used alone or in combination of two or more in any combination and ratio.

[0523] The content of the binder is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 1.2% by mass or more, and usually 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, and most preferably 10% by mass or less, as the ratio of the binder in the positive electrode active material layer. If the ratio of the binder is too low, the positive electrode active material cannot be sufficiently retained, resulting in insufficient mechanical strength of the positive electrode and deterioration of battery performance such as cycle characteristics. On the other hand, if it is too high, it may lead to a decrease in battery capacity and conductivity.

[0524] Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, polyvinyl pyrrolidone, and salts thereof. It may be used alone or in combination of two or more in any combination and ratio.

[0525] The ratio of the thickener to the active material is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. If it is below this range, the coating property may be significantly deteriorated. If it exceeds this range, problems such as a decrease in the ratio of the active material in the positive electrode active material layer, a decrease in battery capacity, and an increase in the resistance between the positive electrode active materials may occur.

[0526] As the above conductive material, known conductive materials can be arbitrarily used. Specific examples include metal materials such as copper, nickel, and gold; graphite (carbon) such as natural graphite and artificial graphite; carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; carbon materials such as needle coke, carbon nanotubes, fullerenes, and VGCF, which are amorphous carbons. These may be used alone or in combination of two or more in any combination and ratio. The conductive material is usually used in the positive electrode active material layer in an amount of 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and usually 50% by mass or less, preferably 30% by mass or less, more preferably 15% by mass or less. If the content is lower than this range, the conductivity may be insufficient. Conversely, if the content is higher than this range, the battery capacity may decrease.

[0527] As the solvent for forming the slurry, there is no particular limitation on the type as long as it can dissolve or disperse the positive electrode active material, conductive material, binder, and thickener used as necessary. Either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water and a mixed solvent of alcohol and water. 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, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), N-butylpyrrolidone (NBP), 3-methoxy-N,N-dimethylpropionamide, dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide.

[0528] As the material of the current collector for the positive electrode, there may be mentioned metals such as aluminum, titanium, tantalum, stainless steel, nickel, or metallic materials such as their alloys; carbon materials such as carbon cloth and carbon paper. Among these, metallic materials, particularly aluminum or its alloys, are preferred.

[0529] As the shape of the current collector, in the case of metallic materials, there may be mentioned metal foils, metal cylinders, metal coils, metal plates, metal thin films, expanded metals, punched metals, foamed metals, etc., and in the case of carbon materials, there may be mentioned carbon plates, carbon thin films, carbon cylinders, etc. Among these, metal thin films are preferred. Note that the thin film may be formed in a mesh shape as appropriate. The thickness of the thin film is arbitrary, but 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. If the thin film is thinner than this range, the strength required as a current collector may be insufficient. Conversely, if the thin film is thicker than this range, the handleability may be impaired.

[0530] Also, it is preferable from the viewpoint of reducing the electrical contact resistance between the current collector and the positive electrode active material layer that a conductive auxiliary agent is applied to the surface of the current collector. Examples of the conductive auxiliary agent include carbon and noble metals such as gold, platinum, and silver.

[0531] The ratio of the thickness of the current collector to the thickness of the positive electrode active material layer is not particularly limited, but the value of (the thickness of the positive electrode active material layer on one side immediately before injecting the electrolytic solution) / (the thickness of the current collector) is preferably 20 or less, more preferably 15 or less, most preferably 10 or less, and preferably 0.5 or more, more preferably 0.8 or more, most preferably in the range of 1 or more. If it exceeds this range, the current collector may generate heat due to Joule heat during high current density charge and discharge. If it is below this range, the volume ratio of the current collector to the positive electrode active material increases, and the capacity of the battery may decrease.

[0532] The positive electrode can be manufactured by a conventional method. For example, there may be mentioned a method in which the above-mentioned positive electrode active material is added with the above-mentioned binder, thickener, conductive material, solvent, etc. to form a slurry-like positive electrode mixture, which is applied to the current collector, dried, and then pressed to increase the density.

[0533] The above densification can be carried out by a hand press, a roller press, or the like. The density of the positive electrode active material layer is preferably 1.0 g / cm 3 or more, more preferably 1.3 g / cm 3 or more, still more preferably 1.5 g / cm 3 or more, and preferably 5 g / cm 3 or less, more preferably 3.0 g / cm 3 or less, still more preferably 2.5 g / cm 3 or less. If it exceeds this range, the permeability of the electrolytic solution near the current collector / active material interface decreases, and in particular, the charge and discharge characteristics at a high current density deteriorate, and high output may not be obtained. If it is less than this range, the conductivity between the active materials decreases, the battery resistance increases, and high output may not be obtained.

[0534] When using the electrolytic solution of the present disclosure, from the viewpoint of enhancing high output and stability at high temperatures, it is preferable that the area of the positive electrode active material layer is larger than the outer surface area of the battery exterior case. Specifically, it is preferable that the total area of the electrode areas of the positive electrodes with respect to the surface area of the exterior of the secondary battery is 15 times or more, more preferably 40 times or more, in terms of area ratio. The outer surface area of the battery exterior case means the total area obtained by calculation from the dimensions of the length, width, and thickness of the case portion filled with the power generation element excluding the protruding portions of the terminals in the case of a bottomed rectangular shape. In the case of a bottomed cylindrical shape, it is the geometric surface area approximated by regarding the case portion filled with the power generation element excluding the protruding portions of the terminals as a cylinder. The total area of the electrode areas of the positive electrodes means the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material. In a structure in which positive electrode mixture layers are formed on both sides via a current collector foil, it means the sum of the areas calculated separately for each surface.

[0535] The thickness of the positive electrode plate is not particularly limited. However, from the viewpoints of high capacity and high output, the thickness of the mixture layer excluding the metal foil thickness of the core material is preferably 10 μm or more, more preferably 20 μm or more, as a lower limit with respect to one side of the current collector, and preferably 500 μm or less, more preferably 450 μm or less.

[0536] Alternatively, a material with a composition different from that of the above positive electrode plate may be used on the surface of the positive electrode plate. Examples of the surface-attached substances include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; and carbon.

[0537] <Negative electrode> The negative electrode is composed of a negative electrode active material layer containing a negative electrode active material and a current collector.

[0538] The negative electrode material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples include carbon materials, alloy-based materials, lithium-containing metal composite oxide materials, and conductive polymers. These may be used alone or in any combination of two or more.

[0539] Examples of the negative electrode active material include carbonaceous materials capable of occluding and releasing lithium, such as pyrolysis products of organic substances under various thermal decomposition conditions, artificial graphite, and natural graphite; metal oxide materials capable of occluding and releasing lithium, such as tin oxide and silicon oxide; lithium metal; various lithium alloys; and lithium-containing metal composite oxide materials. These negative electrode active materials may be used as a mixture of two or more.

[0540] As the carbonaceous material capable of occluding and releasing lithium, those obtained by heat-treating easily graphitizable pitch obtained from various raw materials to produce artificial graphite or purified natural graphite, or those obtained by carbonizing after surface-treating these graphites with pitch or other organic substances are preferred. Carbonaceous materials obtained by heat-treating natural graphite, artificial graphite, artificial carbonaceous substances, and artificial graphite-like substances one or more times in the range of 400 to 3200 °C, carbonaceous materials in which the negative electrode active material layer is composed of at least two or more different crystalline carbonaceous materials and / or has an interface where different crystalline carbonaceous materials are in contact, and carbonaceous materials in which the negative electrode active material layer has an interface where at least two or more different oriented carbonaceous materials are in contact, are more preferred for having a better balance of initial irreversible capacity and charge-discharge characteristics at high current density. Also, these carbon materials may be used alone or in combination of two or more in any combination and ratio.

[0541] Examples of the carbonaceous materials obtained by heat-treating the above artificial carbonaceous substances and artificial graphite-like substances one or more times in the range of 400 to 3200 °C include coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch and those obtained by oxidizing these pitches, needle coke, pitch coke and carbon agents partially graphitized therefrom, thermal decomposition products of organic substances such as furnace black, acetylene black, pitch-based carbon fibers, carbonizable organic substances and their carbides, or solutions obtained by dissolving carbonizable organic substances in low-molecular organic solvents such as benzene, toluene, xylene, quinoline, n-hexane and their carbides.

[0542] As the metal material (excluding lithium titanium composite oxide) used as the above-mentioned negative electrode active material, as long as it can occlude and release lithium, it may be any of simple lithium, simple metals and alloys that form lithium alloys, or their oxides, carbides, nitrides, silicides, sulfides or phosphides, etc. compounds, and is not particularly limited. The simple metals and alloys that form lithium alloys are preferably materials containing metal and semi-metal elements of Group 13 and Group 14, more preferably simple metals of aluminum, silicon and tin (hereinafter abbreviated as "specific metal elements") and alloys or compounds containing these atoms. These may be used alone or in combination of two or more in any combination and ratio.

[0543] Examples of the negative electrode active material having at least one kind of atom selected from specific metal elements include simple metals of any one of the specific metal elements, alloys composed of two or more specific metal elements, alloys composed of one or two or more specific metal elements and one or two or more other metal elements, and compounds containing one or two or more specific metal elements, and composite compounds such as oxides, carbides, nitrides, silicides, sulfides or phosphides of the compounds. By using these simple metals, alloys or metal compounds as the negative electrode active material, it is possible to increase the capacity of the battery.

[0544] In addition, these composite compounds also include compounds in which several elements such as simple metals, alloys or non-metal elements are complexly bonded. Specifically, for example, in the case of silicon or tin, alloys of these elements and metals that do not act as negative electrodes can be used. For example, in the case of tin, complex compounds containing 5 to 6 elements in a combination of a metal that acts as a negative electrode other than tin and silicon, a metal that does not act as a negative electrode, and a non-metal element can also be used.

[0545] Specifically, Si single crystal, SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu6Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, SiOv (0 < v ≤ 2), LiSiO or tin alone, SnSiO3, LiSnO, Mg2Sn, SnO w (0 < w ≤ 2) can be mentioned. In addition, a composite material containing Si or Sn as the first constituent element and, in addition thereto, second and third constituent elements can be mentioned. The second constituent element is, for example, at least one of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium and zirconium. The third constituent element is, for example, at least one of boron, carbon, aluminum and phosphorus. In particular, since high battery capacity and excellent battery characteristics can be obtained, as the above metal material, silicon or tin alone (which may contain trace impurities), SiO v (0 < v ≤ 2), SnO w (0 ≤ w ≤ 2), Si-Co-C composite material, Si-Ni-C composite material, Sn-Co-C composite material, Sn-Ni-C composite material are preferable.

[0546] The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, but from the viewpoint of high current density charge and discharge characteristics, a material containing titanium and lithium is preferable, more preferably a lithium-containing composite metal oxide material containing titanium, and still more preferably a composite oxide of lithium and titanium (hereinafter abbreviated as "lithium titanium composite oxide"). That is, it is particularly preferable to use a lithium titanium composite oxide having a spinel structure in the negative electrode active material for an electrolyte battery because the output resistance is greatly reduced.

[0547] As the above lithium titanium composite oxide, the general formula: Li x Ti y M z O4 [In the formula, M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb.] It is preferably a compound represented by. Among the above compositions, (i) 1.2 ≤ x ≤ 1.4, 1.5 ≤ y ≤ 1.7, z = 0 (ii) 0.9 ≤ x ≤ 1.1, 1.9 ≤ y ≤ 2.1, z = 0 (iii) 0.7 ≤ x ≤ 0.9, 2.1 ≤ y ≤ 2.3, z = 0 The structure of (i), (ii), or (iii) is particularly preferred because it provides a good balance of battery performance.

[0548] Particularly preferred representative compositions of the above compounds are Li 4 / 3 Ti 5 / 3 O4 in (i), Li1Ti2O4 in (ii), and Li 4 / 5 Ti 11 / 5 O4 in (iii). For the structure with Z ≠ 0, for example, Li 4 / 3 Ti 4 / 3 Al 1 / 3 O4 can be mentioned as a preferred example.

[0549] The above negative electrode binder preferably further contains a binder, a thickener, and a conductive material.

[0550] Examples of the above binder include the same ones as those that can be used for the positive electrode described above. The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, further preferably 10% by mass or less, and particularly preferably 8% by mass or less. If the ratio of the binder to the negative electrode active material exceeds the above range, the proportion of the binder that does not contribute to the battery capacity increases, which may lead to a decrease in the battery capacity. If it is below the above range, the strength of the negative electrode may decrease.

[0551] In particular, when containing a rubbery polymer typified by SBR as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. Further, when containing a fluorine-based polymer typified by polyvinylidene fluoride as a main component, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, and usually 15% by mass or less, preferably 10% by mass or less, more preferably 8% by mass or less.

[0552] Examples of the thickener include the same ones as those of the thickener that can be used for the positive electrode described above. The ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. When the ratio of the thickener to the negative electrode active material is below the above range, the coatability may be significantly deteriorated. Further, when it exceeds the above range, the ratio of the negative electrode active material in the negative electrode active material layer may decrease, and there may be problems such as a decrease in the capacity of the battery and an increase in the resistance between the negative electrode active materials.

[0553] Examples of the conductive material for the negative electrode include metal materials such as copper and nickel; carbon materials such as graphite and carbon black.

[0554] The solvent for forming the slurry is not particularly limited as long as it can dissolve or disperse the negative electrode active material, the binder, and the thickener and the conductive material used as necessary, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), N-butylpyrrolidone (NBP), 3-methoxy-N,N-dimethylpropionamide, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphoramide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like.

[0555] Examples of the material of the current collector for the negative electrode include copper, nickel, stainless steel, and the like. Among them, a copper foil is preferable from the viewpoints of being easily processed into a thin film and cost.

[0556] The thickness of the current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less. If the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be excessively reduced. Conversely, if it is too thin, handling may become difficult.

[0557] The negative electrode can be manufactured by a conventional method. For example, a method can be mentioned in which the above-mentioned negative electrode material, a binder, a thickener, a conductive material, a solvent, etc. are added to form a slurry, applied to a current collector, dried, and then pressed to increase the density. When an alloy material is used, a method of forming a thin film layer (negative electrode active material layer) containing the above-mentioned negative electrode active material by a technique such as vapor deposition, sputtering, or plating can also be used.

[0558] The electrode structure when the negative electrode active material is polarized is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g·cm -3 or more, more preferably 1.2 g·cm -3 or more, particularly preferably 1.3 g·cm -3 or more. Also, preferably 2.2 g·cm -3 or less, more preferably 2.1 g·cm -3 or less, and 2.0 g·cm-3 The following is more preferable, 1.9 g·cm -3 The following is particularly preferable. When the density of the negative electrode active material present on the current collector exceeds the above range, the negative electrode active material particles may be destroyed, leading to an increase in the initial irreversible capacity and deterioration of the charge / discharge characteristics at high current density due to a decrease in the permeability of the electrolyte near the current collector / negative electrode active material interface. On the other hand, when it is below the above range, the conductivity between the negative electrode active materials may decrease, the battery resistance may increase, and the capacity per unit volume may decrease.

[0559] The thickness of the negative electrode plate is designed according to the positive electrode plate to be used and is not particularly limited. However, the thickness of the mixture layer after subtracting the metal foil thickness of the core material is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and usually 300 μm or less, preferably 280 μm or less, more preferably 250 μm or less.

[0560] Also, a material with a different composition adhered to the surface of the above negative electrode plate may be used. Examples of the surface-adhered material include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; and carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate.

[0561] <Separator> The secondary battery of the present disclosure preferably further includes a separator. The material and shape of the above separator are not particularly limited as long as they are stable in the electrolyte and have excellent liquid retention properties, and known ones can be used. Among them, resins, glass fibers, inorganic substances, etc. formed of materials stable to the electrolyte of the present disclosure are used, and it is preferable to use a porous sheet or a non-woven fabric-like form having excellent liquid retention properties.

[0562] As materials for the resin and the glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters, etc. can be used. These materials such as polypropylene / polyethylene two-layer film, polypropylene / polyethylene / polypropylene three-layer film, etc. may be used alone, or two or more kinds may be used in combination at any combination and ratio. Among them, the separator is preferably a porous sheet or non-woven fabric made of polyolefins such as polyethylene and polypropylene as raw materials in terms of good electrolyte permeability and shutdown effect.

[0563] The thickness of the separator is arbitrary, but it is usually 1 μm or more, preferably 5 μm or more, more preferably 8 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is too thin compared to the above range, the insulation and mechanical strength may decrease. Also, if it is too thick compared to the above range, not only may the battery performance such as rate characteristics decrease, but also the energy density of the entire electrolyte battery may decrease.

[0564] Furthermore, when using a porous material such as a porous sheet or non-woven fabric as the separator, 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 deteriorate. Also, if it is too large compared to the above range, the mechanical strength of the separator tends to decrease and the insulation decreases.

[0565] 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 circuit is likely to occur. Also, if it is below the above range, the membrane resistance may increase and the rate characteristics may decrease.

[0566] On one hand, as the inorganic material, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used, and those having a particle shape or a fiber shape are used.

[0567] As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the above independent thin film shape, a separator formed by forming a composite porous layer containing the 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 having a particle size of less than 1 μm for 90% are formed on both sides of the positive electrode to form a porous layer using a fluororesin as a binder.

[0568] <Battery Design> The electrode group may be either a laminated structure in which the above positive electrode plate and negative electrode plate are separated by the above separator, or a structure in which the above positive electrode plate and negative electrode plate are wound in a spiral shape through the above separator. 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.

[0569] When the electrode group occupancy rate is below the above range, the battery capacity becomes small. On the other hand, when it exceeds the above range, the void space is small, and when the battery becomes hot, the members expand, the vapor pressure of the liquid component of the electrolyte increases, the internal pressure rises, and the charge / discharge cycle performance and various characteristics such as high-temperature storage of the battery are deteriorated. Furthermore, a gas release valve for releasing the internal pressure to the outside may operate.

[0570] The current collecting structure is not particularly limited, but in order to more effectively realize the improvement of the charge / discharge characteristics at a high current density by the electrolyte of the present disclosure, it is preferable to have a structure that reduces the resistance of the wiring portion and the joining portion. When the internal resistance is reduced in this way, the effect of using the electrolyte of the present disclosure is particularly well exhibited.

[0571] When the electrode group has the above-described 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 above-described 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.

[0572] The material of the exterior case is not particularly limited as long as it is a substance stable against the electrolytic solution used. Specifically, metals such as nickel-plated steel sheets, stainless steels, aluminum or aluminum alloys, magnesium alloys, etc., or a laminated film (laminate film) of resin and aluminum foil is used. From the viewpoint of weight reduction, metals such as aluminum or aluminum alloys and laminate films are preferably used.

[0573] In the exterior case using 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 exterior case using the above 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 via the current collector terminal to form a sealed structure, since it is a joining of 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.

[0574] The shape of the secondary battery of the present disclosure is arbitrary, and examples thereof include shapes such as cylindrical, square, laminate, coin, and large size. Note that the shapes and configurations of the positive electrode, negative electrode, and separator can be changed according to the shape of each battery and used.

[0575] A module including the secondary battery of the present disclosure is also one of the present disclosures.

[0576] An electric double-layer capacitor comprising the electrolyte solution of the present disclosure is also one of the present disclosures. The above electric double-layer capacitor may include a positive electrode, a negative electrode, and the above-described electrolyte solution. In the above electric double-layer capacitor, at least one of the positive electrode and the negative electrode is a polarizable electrode, and as the polarizable electrode and the non-polarizable electrode, the following electrodes described in detail in JP-A-9-7896 can be used.

[0577] The polarizable electrode mainly composed of activated carbon used in the present disclosure preferably contains non-activated carbon having a large specific surface area and a conductive agent such as carbon black that imparts electron conductivity. The polarizable electrode can be formed by various methods. For example, activated carbon powder, carbon black, and a phenolic resin are mixed, and after press molding, they are fired and activated in an inert gas atmosphere and a steam atmosphere to form a polarizable electrode composed of activated carbon and carbon black. Preferably, this polarizable electrode is joined with a current collector and a conductive adhesive or the like.

[0578] Alternatively, activated carbon powder, carbon black, and a binder can be kneaded in the presence of alcohol, formed into a sheet shape, and dried to obtain a polarizable electrode. For example, polytetrafluoroethylene is used as this binder. Further, activated carbon powder, carbon black, a binder, and a solvent can be mixed to form a slurry, and this slurry can be coated on a metal foil of a current collector and dried to obtain a polarizable electrode integrated with the current collector.

[0579] It is also possible to use polarizable electrodes mainly composed of activated carbon for both electrodes to form an electric double-layer capacitor, but a configuration using a non-polarizable electrode on one side, for example, a configuration combining a positive electrode mainly composed of a battery active material such as a metal oxide and a negative electrode of a polarizable electrode mainly composed of activated carbon, a negative electrode mainly composed of a carbon material capable of reversibly occluding and releasing lithium ions, or a negative electrode of lithium metal or a lithium alloy and a polarizable positive electrode mainly composed of activated carbon is also possible.

[0580] Alternatively, instead of or in combination with activated carbon, carbonaceous materials such as carbon black, graphite, expanded graphite, porous carbon, carbon nanotubes, carbon nanohorns, and Ketjen black may be used.

[0581] As the non-polar electrode, preferably, a carbon material capable of reversibly occluding and releasing lithium ions is mainly used, and an electrode is used in which lithium ions are occluded in this carbon material. In this case, a lithium salt is used as the electrolyte. According to the electric double layer capacitor having this configuration, a withstand voltage exceeding 4 V can be obtained.

[0582] The solvent used for preparing the slurry in the production of the electrode preferably dissolves the binder, and N-methylpyrrolidone, dimethylformamide, toluene, xylene, isophorone, methyl ethyl ketone, ethyl acetate, methyl acetate, dimethyl phthalate, ethanol, methanol, butanol, or water is appropriately selected according to the type of binder.

[0583] Examples of the activated carbon used for the polarizable electrode include phenol resin-based activated carbon, coconut shell-based activated carbon, and petroleum coke-based activated carbon. Among these, it is preferable to use petroleum coke-based activated carbon or phenol resin-based activated carbon in terms of obtaining a large capacity. Further, examples of the activation treatment method of activated carbon include a steam activation treatment method and a molten KOH activation treatment method, and it is preferable to use activated carbon by the molten KOH activation treatment method in terms of obtaining a larger capacity.

[0584] Preferable conductive agents used for the polarizable electrode include carbon black, Ketjen black, acetylene black, natural graphite, artificial graphite, metal fiber, conductive titanium oxide, and ruthenium oxide. The mixing amount of the conductive agent such as carbon black used for the polarizable electrode is preferably 1 to 50% by mass in the total amount with activated carbon so as to obtain good conductivity (low internal resistance), and if it is too much, the capacity of the product will decrease.

[0585] In addition, as the activated carbon used for the polarizable electrode, activated carbon with an average particle diameter of 20 μm or less and a specific surface area of 1500 to 3000 m 2 / g is preferably used so as to obtain an electric double layer capacitor with a large capacity and low internal resistance. Further, preferable carbon materials for constituting an electrode mainly composed of a carbon material capable of reversibly occluding and releasing lithium ions include natural graphite, artificial graphite, graphitized mesocarbon microbeads, graphitized whiskers, gas-phase grown carbon fibers, calcined products of furfuryl alcohol resins, or calcined products of novolak resins.

[0586] The current collector may be any material that is chemically and electrochemically corrosion-resistant. As the current collector for the polarizable electrode mainly composed of activated carbon, stainless steel, aluminum, titanium, or tantalum can be preferably used. Among these, stainless steel or aluminum is a particularly preferable material in terms of both the characteristics and price of the obtained electric double layer capacitor. As the current collector for the electrode mainly composed of a carbon material capable of reversibly occluding and releasing lithium ions, preferably stainless steel, copper, or nickel is used.

[0587] In addition, in order to previously occlude lithium ions in a carbon material capable of reversibly occluding and releasing lithium ions, there are (1) a method of mixing powdery lithium with a carbon material capable of reversibly occluding and releasing lithium ions, (2) a method of placing a lithium foil on an electrode formed of a carbon material capable of reversibly occluding and releasing lithium ions and a binder, immersing this electrode in an electrolytic solution in which a lithium salt is dissolved while being in electrical contact with the electrode to ionize lithium, and taking in lithium ions into the carbon material, and (3) a method of placing an electrode formed of a carbon material capable of reversibly occluding and releasing lithium ions and a binder on the negative side, placing lithium metal on the positive side, immersing it in a non-aqueous electrolytic solution using a lithium salt as an electrolyte, and passing a current to electrochemically take in lithium in an ionized state into the carbon material.

[0588] As electric double layer capacitors, wound type electric double layer capacitors, laminated type electric double layer capacitors, coin type electric double layer capacitors, etc. are generally known, and the above electric double layer capacitors can also be in these forms.

[0589] For example, a wound type electric double layer capacitor is manufactured by winding a positive electrode and a negative electrode each composed of a laminate of a current collector and an electrode layer (electrode) via a separator to form a wound element, placing this wound element in a case made of aluminum or the like, filling it with an electrolytic solution, preferably a non-aqueous electrolytic solution, and then sealing it with a rubber sealing body.

[0590] As the separator, those having a conventionally known material and configuration can be used. For example, a polyethylene porous membrane, polytetrafluoroethylene, polypropylene fibers, glass fibers, a non-woven fabric of cellulose fibers, etc. can be mentioned.

[0591] Also, a laminated type electric double layer capacitor in which sheet-like positive and negative electrodes are laminated via an electrolytic solution and a separator by a known method, or a coin type electric double layer capacitor configured in a coin shape with a gasket fixed and positive and negative electrodes via an electrolytic solution and a separator can also be made.

[0592] The electrolytic solution of the present disclosure is useful as an electrolytic solution for large lithium ion secondary batteries for hybrid vehicles, distributed power sources, and electric double layer capacitors.

[0593] Although the embodiments have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims.

Examples

[0594] Next, the present disclosure will be described with reference to examples, but the present disclosure is not limited to such examples only.

[0595] (Preparation of electrolytic solution) Examples 1 to 53 and Comparative Examples 1 to 5 Ethylene carbonate (EC), dimethyl carbonate (DMC), FE1, FE2, FE3, FE4, and FE5 were mixed in the volume ratios described in Table 1. LiPF6 and LiFSI were added to this mixture in the concentrations described in Table 1. Furthermore, each component described in Table 1 was added in the amounts described in Table 1 to obtain a non-aqueous electrolyte solution.

[0596] (Fabrication of an Aluminum Laminate-Type Lithium-Ion Secondary Battery) [Fabrication of the Positive Electrode] 93 mass% of LiCoO2 (LCO) as the positive electrode active material, 3 mass% of acetylene black as the conductive material, and 4 mass% of polyvinylidene fluoride (PVdF) as the binder were mixed in an N-methylpyrrolidone solvent to form a slurry. The obtained slurry was applied to one side of a 15-μm-thick aluminum foil pre-coated with a conductive aid, dried, and roll-pressed with a press machine. It was then cut into a size of 50 mm in width and 30 mm in length for the active material layer to obtain a positive electrode.

[0597] [Fabrication of the Negative Electrode] To 98 parts by mass of a carbonaceous material (graphite), 1 part by mass of an aqueous dispersion of sodium carboxymethylcellulose (concentration of sodium carboxymethylcellulose: 1 mass%) and 1 part by mass of an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber: 50 mass%) were added as a thickening agent and a binder, and the mixture was mixed with a disperser to form a slurry. The obtained slurry was applied to a 15-μm-thick copper foil and dried. The resulting product was rolled with a press machine and cut into a size of 52 mm in width and 32 mm in length for the active material layer to obtain a negative electrode.

[0598] [Fabrication of the Aluminum Laminate Cell] The positive electrode and the negative electrode were opposed to each other with a 20-μm-thick microporous polyethylene film (separator) interposed therebetween, the non-aqueous electrolyte solution obtained above was injected, and after the non-aqueous electrolyte solution had sufficiently penetrated the separator and the like, it was sealed and subjected to preliminary charging and aging to fabricate a lithium-ion secondary battery.

[0599] (Measurement of Battery Characteristics) [Evaluation of IV Resistance] The above battery was charged to 50% SOC and then moved to a constant temperature bath at -20°C and allowed to stand for 3 hours until the temperature inside the cell became constant. Then, it was discharged at a 1C rate for 10 seconds, and the voltage drop (V) at that time was measured. The resistance value was calculated using the formula V = IR from the obtained voltage value and current value. The above SOC indicates the state of charge, and SOC 100% is the capacity when charged up to 4.3V. For example, SOC 50% indicates half the capacity of SOC 100%. The results are shown in Table 1.

[0600]

Table 1

[0601] The abbreviations in the table are as follows. FE1: HCF2CF2CH2OCF2CF2H FE2: HCF2CF2CH2OCF2CHFCF3 FE3: CF3CF2CH2OCH2CF2CF3 FE4: CH3CH2CH2OCF2CF2H FE5: CH3CH2CH2OCF2CHFCF3 EC: Ethylene carbonate DMC: Dimethyl carbonate VC: Vinylene carbonate FEC: Fluoroethylene carbonate VEC: Vinyl ethylene carbonate DFEC: Difluoroethylene carbonate LiFSI: Lithium bis(fluorosulfonyl)imide Et2NSO3Li: (CH3CH2)2NSO3Li LiBOB: Lithium bisoxalate borate LiDFOB: Lithium difluorooxalate borate

Claims

1. An electrolytic solution containing a fluorine-containing ether compound (1) represented by the following formula (1), a fluorine-containing ether compound (2) represented by the following formula (2), and lithium bis(fluorosulfonyl)imide. Formula (1): HCF ２ -CF ２ -O-Rf １ (wherein, Rf １ is an optionally fluorinated alkyl group having 1 to 5 carbon atoms) Formula (2): CF ３ -CHF-CF ２ -O-Rf ２ (wherein, Rf ２ is an optionally fluorinated alkyl group having 1 to 5 carbon atoms)

2. The electrolytic solution according to Claim 1, wherein the total content of the fluorine-containing ether compounds (1) and (2) is 5 to 90% by volume with respect to the electrolytic solution.

3. The electrolytic solution according to Claim 1 or 2, wherein the total content of the fluorine-containing ether compounds (1) and (2) is 20 to 90% by volume with respect to the electrolytic solution.

4. The electrolytic solution according to Claim 1 or 2, wherein the content of lithium bis(fluorosulfonyl)imide is 0.01 to 8 M with respect to the electrolytic solution.

5. The electrolytic solution according to Claim 1 or 2, wherein the content of the fluorine-containing ether compound (2) is 0.00005 to 6% by volume with respect to the fluorine-containing ether compound (1).

6. The Rf in the formula (1) １ is a fluorinated alkyl group having 1 to 3 carbon atoms, and the Rf in the formula (2) ２ is a fluorinated alkyl group having 1 to 3 carbon atoms. The electrolytic solution according to claim 1 or 2

7. The fluorine-containing ether compound (1) is HCF ２ CF ２ OCH ２ CF ２ CF ２ H and CH ３ CH ２ CH ２ OCF ２ CF ２ is at least one selected from the group consisting of, and the fluorine-containing ether compound (2) is CF ３ CHFCF ２ OCH ２ CF ２ CF ２ H and CH ３ CH ２ CH ２ OCF ２ CHFCF ３ The electrolytic solution according to claim 1 or 2, which is at least one selected from the group consisting of.

8. The fluorine-containing ether compound (1) is HCF ２ CF ２ OCH ２ CF ２ CF ２ H, and the fluorine-containing ether compound (2) is CF ３ CHFCF ２ OCH ２ CF ２ CF ２ H. The electrolytic solution according to claim 1 or 2

9. The electrolytic solution according to Claim 1 or 2, further comprising at least one solvent selected from the group consisting of a carbonate and a carboxylic acid ester, and a lithium salt.

10. A secondary battery comprising the electrolytic solution according to Claim 1 or 2.

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