Nonaqueous electrolyte for electrochemical device, electrochemical device precursor, and method for manufacturing electrochemical device

Abstract

To provide a non-aqueous electrolyte capable of suppressing the initial resistance of an electrochemical device and suppressing an increase in resistance after high-temperature storage even when the electrochemical device is stored for a long period of time in high-temperature environment.SOLUTION: A non-aqueous electrolyte contains a fluorinated lithium sulfonate compound (I) and a compound (II) represented by the following formula (II). In the formula (II), R21 and R22 are each independently composed of at least one atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and a halogen atom (except for a case where R21 and R22 are hydrogen atoms, and a case where one of R21 and R22 is a hydrogen atom, the other of R21 and R22 is a methyl group).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a non-aqueous electrolyte, an electrochemical device precursor, and a method for manufacturing an electrochemical device. [Background technology]

[0002] Lithium-ion secondary batteries have been attracting attention as batteries with high energy density.

[0003] Patent Document 1 discloses a non-aqueous electrolyte secondary battery (hereinafter referred to as "lithium ion secondary battery"). The lithium ion secondary battery disclosed in Patent Document 1 includes a positive electrode, a negative electrode, a non-aqueous electrolyte, and an outer case. The positive electrode, the negative electrode, and the non-aqueous electrolyte are sealed in the outer case. Each of the positive electrode and the negative electrode is capable of absorbing and releasing lithium ions. The non-aqueous electrolyte contains lithium fluorosulfonate and sulfate ions. The content of sulfate ions in the non-aqueous electrolyte is 1.0 × 10 -7 mol / L or more 1.0×10 -2 mol / L or less. The positive electrode has a positive electrode active material layer on a current collector. The positive electrode active material layer contains at least one material selected from the group consisting of lithium-cobalt composite oxide, lithium-cobalt-nickel composite oxide, lithium-manganese composite oxide, lithium-cobalt-manganese composite oxide, lithium-nickel composite oxide, lithium-cobalt-nickel composite oxide, lithium-nickel composite oxide, lithium-nickel-manganese composite oxide, and lithium-nickel-cobalt-manganese composite oxide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6750716 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the lithium ion secondary battery disclosed in Patent Document 1 may have a high DC resistance immediately after aging treatment (hereinafter referred to as "initial resistance"). Furthermore, when the lithium ion secondary battery disclosed in Patent Document 1 is charged or discharged in a high-temperature environment, the DC resistance after charging or discharging in the high-temperature environment (hereinafter referred to as "resistance after high-temperature storage") may increase.

[0006] In view of the above circumstances, an object of the present disclosure is to provide a nonaqueous electrolyte solution, an electrochemical device precursor, and a method for producing an electrochemical device that can suppress the initial resistance of an electrochemical device and suppress an increase in resistance after high-temperature storage even when the electrochemical device is stored in a high-temperature environment for a long period of time. [Means for solving the problem]

[0007] The means for solving the above problems include the following embodiments.

[0008] <1> a fluorinated lithium sulfonate compound (I); Compound (II) represented by the following formula (II) A non-aqueous electrolyte comprising:

[0009] [ka]

[0010] [In formula (II), R 21 and R 22 each independently represents a group composed of at least one atom selected from the group consisting of carbon, hydrogen, nitrogen, oxygen, sulfur, phosphorus, and halogen atoms (provided that R 21 and R 22 is a hydrogen atom, and R 21 and R 22 One of the atoms is a hydrogen atom, and R 21 and R 22 (Except when the other is a methyl group.) <2> R 21 and the R 22at least one of the above is a group containing a sulfonyl group or a hydrocarbon group having 1 to 6 carbon atoms; <1> The non-aqueous electrolyte solution according to claim 1. <3> R 21 and the R 22 at least one of which is a hydrocarbon group having 3 to 6 carbon atoms, a group represented by the following formula (ii-1), or a group represented by the following formula (ii-2): <1> or <2> The non-aqueous electrolyte solution according to claim 1.

[0011] [ka]

[0012] <4> R 21 and the R 22 At least one of the above is a group represented by formula (ii-1). <3> The non-aqueous electrolyte solution according to claim 1. <5> The above-mentioned composition further contains a cyclic carbonate compound (III) containing a carbon-carbon unsaturated bond. <1> ~ <4> 10. The non-aqueous electrolyte solution according to claim 9, <6> The compound (IV) further contains a compound (IV) represented by the following formula (IV): <1> ~ <5> 10. The non-aqueous electrolyte solution according to claim 9,

[0013] [ka]

[0014] [In formula (IV), R 41 and R 42 each independently represents a fluorine atom, a trifluoromethyl group, or a pentafluoroethyl group. <7> The above-mentioned compound (V) further contains a compound (V) represented by the following formula (V): <1> ~ <6> 10. The non-aqueous electrolyte solution according to claim 9,

[0015] [ka]

[0016] [In formula (V), M is an alkali metal; b is an integer from 1 to 3, m is an integer from 1 to 4, n is an integer from 0 to 8, q is 0 or 1; R 51 represents 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 groups may contain a substituent or a heteroatom in the structure, and when q is 1 and m is 2 to 4, m R 51 may be bonded to each other. R 52 is a halogen atom, 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 (these groups may contain a substituent or a heteroatom in the structure, and when n is 2 to 8, n R 52 may be bonded to each other to form a ring; Q 1 , and Q 2 are each independently an oxygen atom or a carbon atom. <8> The compound (VI) further comprises at least one compound selected from the group consisting of lithium monofluorophosphate and lithium difluorophosphate. <1> ~ <7> 10. The non-aqueous electrolyte solution according to claim 9, <9> Case and a positive electrode, a negative electrode, a separator, and an electrolyte solution housed in the case; Equipped with the positive electrode is a positive electrode capable of absorbing and desorbing lithium ions, the negative electrode is capable of absorbing and desorbing lithium ions, The electrolyte solution <1> ~ <8> 10. An electrochemical device precursor, which is the nonaqueous electrolyte solution according to any one of the above items. <10> The positive electrode contains, as a positive electrode active material, a lithium-containing composite oxide represented by the following formula (X): <9> The electrochemical device precursor according to claim 1. LiNi a Cob Mn c O2… Formula (X) [In formula (X), a, b, and c each independently represent a number greater than 0 and less than 1.00, and the sum of a, b, and c represents a number greater than or equal to 0.99 and less than or equal to 1.00.] <11> The positive electrode contains lithium iron phosphate as a positive electrode active material. <9> The electrochemical device precursor according to claim 1. <12> The aforementioned <9> ~ <11> preparing an electrochemical device precursor according to any one of the above; charging and discharging the electrochemical device precursor; A method for manufacturing an electrochemical device, comprising: [Effects of the Invention]

[0017] The present disclosure provides a nonaqueous electrolyte solution, an electrochemical device precursor, and a method for producing an electrochemical device that can suppress the initial resistance of an electrochemical device and suppress an increase in resistance after high-temperature storage even when the electrochemical device is stored in a high-temperature environment for a long period of time. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view of an electrochemical device precursor according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0019] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, the amount of each component in a composition means the total amount of the multiple substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition. In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0020] [Nonaqueous electrolyte] The nonaqueous electrolyte of the present disclosure will now be described.

[0021] The nonaqueous electrolyte is suitable for use as an electrolyte in electrochemical devices, including lithium ion secondary batteries, which will be described in detail below with reference to FIG.

[0022] The non-aqueous electrolyte solution contains a fluorinated lithium sulfonate compound (I) and a compound (II) represented by the following formula (II) (hereinafter referred to as "cyclic sulfone compound (II)"). The fluorinated lithium sulfonate compound (I) and the cyclic sulfone compound (II) will be described in detail below.

[0023] [ka]

[0024] In other words, the non-aqueous electrolyte contains fluorosulfonate ions (FSO3 - ) and lithium ion (Li + ) and a cyclic sulfone compound (II).

[0025] The nonaqueous electrolyte solution contains the fluorinated lithium sulfonate compound (I) and the cyclic sulfone compound (II), and therefore can suppress the initial resistance of the electrochemical device and also suppress an increase in resistance after high-temperature storage even when the electrochemical device is stored in a high-temperature environment for a long period of time. The reason why the initial resistance of the electrochemical device is suppressed and the increase in resistance after high-temperature storage is suppressed even when the electrochemical device is stored in a high-temperature environment for a long period of time is presumed to be mainly as follows. When an electrochemical device using the nonaqueous electrolyte solution of the present disclosure is charged or discharged (hereinafter referred to as "charge / discharge"), a solid electrolyte interphase (SEI) film (hereinafter referred to as "SEI film") is thought to be formed on the surface of the negative electrode and the surface of the positive electrode. Hereinafter, when there is no need to distinguish between the SEI film of the negative electrode and the SEI film of the positive electrode, the SEI film of the negative electrode and the SEI film of the positive electrode may be simply referred to as "SEI film". The SEI film is thought to be formed mainly by lithium ions in the non-aqueous electrolyte and decomposition products of the non-aqueous electrolyte that are decomposed during the charging and discharging of the electrochemical device. The formation of an SEI film is thought to make it difficult for side reactions, other than the original battery reaction, to occur during the charge / discharge cycle of the electrochemical device, even if the device is stored in a high-temperature environment for a long period of time. The battery reaction is the reaction in which lithium ions enter and exit (intercalate) between the positive and negative electrodes. Side reactions include the reductive decomposition reaction of the non-aqueous electrolyte by the negative electrode, the oxidative decomposition reaction of the non-aqueous electrolyte by the positive electrode, and the elution of metal elements from the positive electrode active material. In an electrochemical device using the nonaqueous electrolyte solution of the present disclosure, the SEI film is less likely to thicken during charge-discharge cycles immediately after aging treatment and after storage in a high-temperature environment, and therefore lithium ions in the nonaqueous electrolyte solution are less likely to be consumed. For the reasons described above, the nonaqueous electrolyte solution of the present disclosure can suppress the initial resistance of an electrochemical device and can also suppress an increase in resistance after high-temperature storage even when the electrochemical device is stored in a high-temperature environment for a long period of time.

[0026] <Fluorinated lithium sulfonate compounds (I)> The non-aqueous electrolyte contains a fluorinated lithium sulfonate compound (I) represented by the following formula (I).

[0027] [ka]

[0028] The upper limit of the content of the fluorinated lithium sulfonate compound (I) is 10.0 mass% or less, preferably 5.0 mass% or less, more preferably 3.0 mass% or less, still more preferably 2.0 mass% or less, and particularly preferably 0.9 mass% or less, based on the total amount of the non-aqueous electrolyte. If the upper limit of the content of the fluorinated lithium sulfonate compound (I) is within the above range, it becomes possible to improve the characteristics of the electrochemical device, such as the capacitance value and resistance value, in a balanced manner. The lower limit of the content of the fluorinated lithium sulfonate compound (I) is 0.01 mass% or more, preferably 0.1 mass% or more, more preferably 0.3 mass% or more, and particularly preferably 0.6 mass% or more, based on the total amount of the non-aqueous electrolyte. When the lower limit of the content of the fluorinated lithium sulfonate compound (I) is within the above range, a sufficient amount of SEI film derived from the fluorinated lithium sulfonate compound (I) is formed, and battery characteristics after durability tests such as high-temperature storage tests can be improved.

[0029] <Cyclic sulfone compound (II)> The non-aqueous electrolyte contains a cyclic sulfone compound (II) represented by the following formula (II).

[0030] [ka]

[0031] In formula (II), R 21 and R 22 each independently represents a group composed of at least one atom selected from the group consisting of carbon, hydrogen, nitrogen, oxygen, sulfur, phosphorus, and halogen atoms (provided that R 21 and R 22 is a hydrogen atom, and R 21 and R 22 One of the atoms is a hydrogen atom, and R 21 and R 22 (Except when the other is a methyl group).

[0032] Hereinafter, a group composed of at least one atom selected from the group consisting of carbon, hydrogen, nitrogen, oxygen, sulfur, phosphorus, and halogen atoms will be referred to as a "first group."

[0033] In formula (II), R 21 and R 22 At least one of these is preferably a group containing a sulfonyl group (-S(=O)2-) or a hydrocarbon group having 1 to 6 carbon atoms. Hereinafter, a group containing a sulfonyl group (-S(=O)2-) or a hydrocarbon group having 1 to 6 carbon atoms will be referred to as a "second group". In other words, R 21 and R 22 is preferably a case where both are the second group, or one is the second group and the other is the first group (but excluding the second group). This makes it possible for the non-aqueous electrolyte to further reduce the initial resistance of the electrochemical device, and also to suppress an increase in resistance after high-temperature storage even when the electrochemical device is stored in a high-temperature environment for a long period of time.

[0034] Examples of the group containing a sulfonyl group include a sulfonate group (-OS(=O)2-), a sulfonyloxy group (-OS(=O)2O-), an alkylenesulfonyl group, and an arylenesulfonyl group.

[0035] The hydrocarbon group having 1 to 6 carbon atoms may be a straight-chain hydrocarbon group, or may be a hydrocarbon group having a branched and / or cyclic structure. Examples of hydrocarbon groups having 1 to 6 carbon atoms include alkyl groups having 1 to 6 carbon atoms and alkenyl groups having 1 to 6 carbon atoms. Examples of alkyl groups having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, 1-ethylpropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, 3,3-dimethylbutyl, n-pentyl, isopentyl, neopentyl, 1-methylpentyl, n-hexyl, isohexyl, sec-hexyl, and tert-hexyl groups. Examples of the alkenyl group having 1 to 6 carbon atoms include a vinyl group, a 1-propenyl group, an allyl group, a 1-butenyl group, a 2-butenyl group, a 3-butenyl group, a pentenyl group, a hexenyl group, an isopropenyl group, a 2-methyl-2-propenyl group, a 1-methyl-2-propenyl group, and a 2-methyl-1-propenyl group. The hydrocarbon group having 1 to 6 carbon atoms is preferably an alkyl group, an alkenyl group, or an alkynyl group, more preferably an alkyl group or an alkenyl group, and particularly preferably an alkyl group.

[0036] R 21 and R 22 It is more preferable that at least one of the groups is a hydrocarbon group having 3 to 6 carbon atoms, a group represented by the following formula (ii-1), or a group represented by the following formula (ii-2).

[0037] [ka]

[0038] Hereinafter, a hydrocarbon group having 3 to 6 carbon atoms, a group represented by the following formula (ii-1), or a group represented by the following formula (ii-2) will be referred to as a "third group". In other words, R 21 and R 22 is more preferably a case where both are tertiary groups, or one is a tertiary group and the other is a first group (excluding tertiary groups). This makes it possible for the non-aqueous electrolyte to further reduce the initial resistance of the electrochemical device, and also to suppress an increase in resistance after high-temperature storage even when the electrochemical device is stored in a high-temperature environment for a long period of time.

[0039] Examples of hydrocarbon groups having 3 to 6 carbon atoms include alkyl groups having 3 to 6 carbon atoms and alkenyl groups having 3 to 6 carbon atoms. Examples of alkyl groups having 3 to 6 carbon atoms include n-propyl, isopropyl, 1-ethylpropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, 3,3-dimethylbutyl, n-pentyl, isopentyl, neopentyl, 1-methylpentyl, n-hexyl, isohexyl, sec-hexyl, and tert-hexyl. Examples of alkenyl groups having 3 to 6 carbon atoms include allyl, 1-butenyl, 2-butenyl, 3-butenyl, pentenyl, hexenyl, isopropenyl, 2-methyl-2-propenyl, 1-methyl-2-propenyl, and 2-methyl-1-propenyl. The hydrocarbon group having 3 to 6 carbon atoms is preferably an alkyl group, an alkenyl group, or an alkynyl group, more preferably an alkyl group or an alkenyl group, and particularly preferably an alkyl group.

[0040] R 21 and R 22 It is more preferable that at least one of the above is a group represented by formula (ii-1). Hereinafter, the group represented by the following formula (ii-1) will be referred to as a "fourth group". In other words, R 21 and R 22 It is more preferred that both of the groups are quaternary groups, or that one of the groups is a quaternary group and the other is a first group (excluding the quaternary group). This allows the nonaqueous electrolyte to further reduce the initial resistance of the electrochemical device and to suppress an increase in resistance after high-temperature storage even when the electrochemical device is stored in a high-temperature environment for a long period of time.Furthermore, the nonaqueous electrolyte can suppress a decrease in capacity [mAh / g] after charging or discharging in a high-temperature environment (hereinafter referred to as "capacity after high-temperature storage") even when the electrochemical device is stored in a high-temperature environment for a long period of time.

[0041] R 21 and R 22When is composed of the first group, specific examples of the cyclic sulfone compound (II) include compounds represented by the following formulae (II-1) to (II-14).

[0042] [ka]

[0043] R 21 and R 22 When at least one of the groups is the second group, specific examples of the cyclic sulfone compound (II) include compounds represented by the above formulae (II-1) to (II-8). R 21 and R 22 When at least one of the groups is a third group, specific examples of the cyclic sulfone compound (II) include compounds represented by the above formulae (II-1) to (II-7). R 21 and R 22 When at least one of the groups is a fourth group, specific examples of the cyclic sulfone compound (II) include compounds represented by the above formula (II-2).

[0044] The upper limit of the content of the cyclic sulfone compound (II) is preferably 10.0 mass% or less, more preferably 5.0 mass% or less, even more preferably 3.0 mass% or less, even more preferably 2.0 mass% or less, and particularly preferably 0.9 mass% or less, based on the total amount of the non-aqueous electrolyte. If the upper limit of the content of the cyclic sulfone compound (II) is within the above range, it is possible to suppress decomposition of the non-aqueous solvent on the positive electrode or negative electrode while suppressing an increase in the thickness of the SEI film. As a result, the characteristics of the electrochemical device after high-temperature storage are improved. Improving the characteristics of an electrochemical device after high-temperature storage includes at least one of suppressing an increase in resistance after high-temperature storage even when the electrochemical device is stored in a high-temperature environment for a long period of time, and suppressing a decrease in capacity after high-temperature storage even when the electrochemical device is stored in a high-temperature environment for a long period of time. The lower limit of the content of the cyclic sulfone compound (II) is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, even more preferably 0.3 mass% or more, and particularly preferably 0.6 mass% or more, based on the total amount of the non-aqueous electrolyte. If the lower limit of the content of the cyclic sulfone compound (II) is within the above range, an SEI film having a thickness that can suppress decomposition of the non-aqueous solvent in the non-aqueous electrolyte is formed. As a result, the characteristics of the electrochemical device after high-temperature storage are improved.

[0045] <Cyclic carbonate compound (III)> The non-aqueous electrolyte preferably further contains a cyclic carbonate compound (III) containing a carbon-carbon unsaturated bond (hereinafter simply referred to as "unsaturated cyclic carbonate compound (III)").

[0046] The nonaqueous electrolyte solution further contains an unsaturated cyclic carbonate compound (III) in addition to the fluorinated lithium sulfonate compound (I) and the cyclic sulfone compound (II), thereby making it possible to further suppress a decrease in capacity and an increase in DC resistance even when the electrochemical device is stored in a high-temperature environment for a long period of time. This effect is presumably due to the following reasons. The unsaturated cyclic carbonate compound (III) is easily reductively decomposed by the negative electrode and forms an SEI film before the nonaqueous electrolyte is reductively decomposed on the negative electrode, even during charge-discharge cycles after storage in a high-temperature environment. This suppresses the decomposition of the nonaqueous electrolyte at the negative electrode. As a result, the increase in DC resistance of the electrochemical device is further suppressed.

[0047] Examples of the unsaturated cyclic carbonate compound (III) include vinylene carbonate compounds (III-1) and ethylene carbonate compounds (III-2).

[0048] The vinylene carbonate compound (III-1) is represented by the following formula (III-1).

[0049] [ka]

[0050] In formula (III-1), R 31 and R 32 each independently represents a hydrogen atom, a methyl group, an ethyl group, or a propyl group.

[0051] Specific examples of the vinylene carbonate compound (III-1) include compounds represented by the following formulas (III-11) to (III-17).

[0052] [ka]

[0053] The ethylene carbonate compound (III-2) is represented by the following formula (III-2).

[0054] [ka]

[0055] In formula (III-2), R 31 and R 32 each independently represents a hydrogen atom or an alkenyl group having 2 to 3 carbon atoms (provided that R 31 and R 32 Except when is a hydrogen atom.

[0056] In formula (III-2), R 31 and R 32 Examples of the alkenyl group having 2 to 3 carbon atoms represented by the formula include a vinyl group and an allyl group.

[0057] Specific examples of the ethylene carbonate compound (III-2) include compounds represented by the following formulae (III-21) to (III-24).

[0058] [ka]

[0059] When the non-aqueous electrolyte contains the unsaturated cyclic carbonate compound (III), the upper limit of the content of the unsaturated cyclic carbonate compound (III) is preferably 10.0 mass% or less, more preferably 5.0 mass% or less, and even more preferably 3.0 mass% or less, based on the total amount of the non-aqueous electrolyte. When the upper limit of the content of the unsaturated cyclic carbonate compound (III) is within the above range, decomposition of the non-aqueous solvent on the positive electrode or negative electrode can be suppressed, while an increase in the thickness of the SEI film can be suppressed. As a result, the characteristics of the electrochemical device after high-temperature storage are improved. The lower limit of the content of the unsaturated cyclic carbonate compound (III) is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, and even more preferably 0.3 mass% or more, based on the total amount of the non-aqueous electrolyte. If the lower limit of the content of the unsaturated cyclic carbonate compound (III) is within the above range, an SEI film having a thickness that can suppress decomposition of the non-aqueous solvent in the non-aqueous electrolyte is formed. As a result, the characteristics of the electrochemical device after high-temperature storage are improved.

[0060] <Compound (IV)> The non-aqueous electrolyte preferably contains a compound represented by the following formula (IV) (hereinafter referred to as "sulfonimide lithium salt compound (IV)").

[0061] [ka]

[0062] In formula (IV), R 41 and R 42 each independently represents a fluorine atom, a trifluoromethyl group, or a pentafluoroethyl group.

[0063] The nonaqueous electrolyte solution further contains a sulfonimide lithium salt compound (IV) in addition to the fluorinated lithium sulfonate compound (I) and the cyclic sulfone compound (II), thereby making it possible to further suppress a decrease in capacity and an increase in DC resistance even when the electrochemical device is stored in a high-temperature environment for a long period of time. This effect is presumably due to the following reasons. After an electrochemical device is stored in a high-temperature environment, the sulfonimide lithium salt compound (IV) is easily decomposed by oxidation at the positive electrode before the nonaqueous electrolyte is reductively decomposed on the negative electrode, forming an SEI film. This suppresses the decomposition of the nonaqueous electrolyte at the positive electrode. As a result, the increase in DC resistance of the electrochemical device is further suppressed even when the electrochemical device is stored at high temperatures for a long period of time.

[0064] Specific examples of the sulfonimide lithium salt compound (IV) include compounds represented by the following formulae (IV-1) to (IV-3).

[0065] [ka]

[0066] When the non-aqueous electrolyte contains sulfonimide lithium salt compound (IV), the upper limit of the content of sulfonimide lithium salt compound (IV) is preferably 10.0 mass% or less, more preferably 5.0 mass% or less, and even more preferably 3.0 mass% or less, based on the total amount of the non-aqueous electrolyte. When the upper limit of the content of sulfonimide lithium salt compound (IV) is within the above range, the SEI film does not impair the conductivity of lithium cations, and the electrochemical device can operate. Furthermore, since the SEI film contains a structure mainly composed of sulfonimide, the battery characteristics of the electrochemical device are improved. The lower limit of the content of the sulfonimide lithium salt compound (IV) is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, based on the total amount of the nonaqueous electrolyte. When the lower limit of the content of the sulfonimide lithium salt compound (IV) is within the above range, the SEI film contains a sufficient amount of a structure mainly composed of sulfonimide. This facilitates the formation of a thermally and chemically stable polymer structure. Therefore, at high temperatures, elution of SEI film components that impair the durability of the SEI film and deterioration of the SEI film are unlikely to occur. As a result, the durability of the SEI film is improved. Furthermore, the increase in DC resistance of the electrochemical device can be further suppressed even when stored for long periods in a high-temperature environment.

[0067] <Compound (V)> The non-aqueous electrolyte preferably contains a compound (V) represented by the following formula (V) (hereinafter referred to as "cyclic dicarbonyl compound (V)").

[0068] [ka]

[0069] In formula (V), M is an alkali metal; b is an integer from 1 to 3, m is an integer from 1 to 4, n is an integer from 0 to 8, q is 0 or 1; R 51 represents 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 groups may contain a substituent or a heteroatom in the structure, and when q is 1 and m is 2 to 4, m R 51 may be bonded to each other. R 52 is a halogen atom, 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 (these groups may contain a substituent or a heteroatom in the structure, and when n is 2 to 8, n R 52 may be bonded to each other to form a ring; Q 1 , and Q 2 are each independently an oxygen atom or a carbon atom.

[0070] The nonaqueous electrolyte solution contains a cyclic dicarbonyl compound (V) in addition to the fluorinated lithium sulfonate compound (I) and the cyclic sulfone compound (II), and thereby the decrease in capacity and the increase in DC resistance of the electrochemical device are further suppressed even during charge-discharge cycles after high-temperature storage. This effect is presumably due to the following reasons. The nonaqueous electrolyte solution contains a cyclic dicarbonyl compound (V) in addition to the fluorinated lithium sulfonate compound (I) and the cyclic sulfone compound (II). This allows the SEI film to contain bonds derived from the cyclic dicarbonyl compound (V) within the film, in addition to the above-described reaction products. This facilitates the formation of a thermally and chemically stable polymer structure. Therefore, leaching of SEI film components, which impairs the durability of the SEI film, and deterioration of the SEI film are unlikely to occur at high temperatures. As a result, the decrease in capacity and increase in DC resistance of the electrochemical device are further suppressed during charge-discharge cycles after long-term storage in a high-temperature environment.

[0071] M is an alkali metal. Examples of the alkali metal include lithium, sodium, and potassium. Among these, M is preferably lithium. b represents the valence of the anion and the number of cations, and is an integer of 1 to 3, preferably 1. When b is 3 or less, the salt of the anionic compound is easily dissolved in the mixed organic solvent. Each of m and n is a value related to the number of ligands. Each of m and n is determined depending on the type of M. m is an integer of 1 to 4. n is an integer of 0 to 8. q is 0 or 1. When q is 0, the chelate ring is a five-membered ring, and when q is 1, the chelate ring is a six-membered ring. R 51represents 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, halogenated alkylene groups, arylene groups, or halogenated arylene groups may contain a substituent or a heteroatom in their structure. Specifically, these groups may contain a substituent in place of a hydrogen atom. Examples of the substituent include 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. Furthermore, the carbon element of these groups may be replaced by a nitrogen atom, a sulfur atom, or an oxygen atom. Furthermore, when q is 1 and m is 2 to 4, m R 51 may be bonded to each other. An example of such a ligand is ethylenediaminetetraacetic acid. R 52 represents a halogen atom, 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. These alkyl groups, halogenated alkyl groups, aryl groups, and halogenated aryl groups are represented by R 51 Similarly, the structure may contain a substituent or a heteroatom, and when n is 2 to 8, n R 52 may be bonded to each other to form a ring. 52 As the group, an electron-withdrawing group is preferred, and a fluorine atom is particularly preferred. Q 1 , and Q 2 each independently represents O or S. That is, the ligand bonds to Y via these hetero atoms.

[0072] Specific examples of the cyclic dicarbonyl compound (V) include compounds represented by the following formulae (V-1) and (V-2).

[0073] [ka]

[0074] When the non-aqueous electrolyte contains a cyclic dicarbonyl compound (V), the upper limit of the content of the cyclic dicarbonyl compound (V) is preferably 10% by mass or less, more preferably 5.0% by mass or less, even more preferably 3.0% by mass or less, and particularly preferably 2.0% by mass or less, based on the total amount of the non-aqueous electrolyte. When the upper limit of the content of the cyclic dicarbonyl compound (V) is within the above range, the SEI film does not impair the conductivity of lithium cations, and the electrochemical device can operate. Furthermore, since the SEI film contains a cyclic dicarbonyl structure, the battery characteristics of the electrochemical device are improved. The lower limit of the content of the cyclic dicarbonyl compound (V) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.10% by mass or more, based on the total amount of the nonaqueous electrolyte. When the lower limit of the content of the cyclic dicarbonyl compound (V) is within the above range, the SEI film contains a sufficient amount of a structure mainly composed of cyclic dicarbonyl. This facilitates the formation of a thermally and chemically stable inorganic salt or polymer structure. Therefore, elution of SEI film components that impair the durability of the SEI film and deterioration of the SEI film are unlikely to occur at high temperatures. As a result, the durability of the SEI film and the characteristics of the electrochemical device after high-temperature storage are improved.

[0075] <Compound (VI)> The non-aqueous electrolyte preferably contains at least one compound (VI) selected from the group consisting of lithium monofluorophosphate and lithium difluorophosphate (hereinafter referred to as "lithium fluorophosphate compound (VI)"). Lithium difluorophosphate is represented by the following formula (VI-1), and lithium monofluorophosphate is represented by the following formula (VI-2).

[0076] [ka]

[0077] The non-aqueous electrolyte solution contains the lithium fluorophosphate compound (VI) in addition to the fluorinated lithium sulfonate compound (I) and the cyclic sulfone compound (II), and thereby the decrease in capacity and the increase in DC resistance of the electrochemical device are further suppressed even during charge-discharge cycles after storage in a high-temperature environment.

[0078] When the non-aqueous electrolyte contains the lithium fluorophosphate compound (VI), the upper limit of the content of the lithium fluorophosphate compound (VI) is preferably 5.0 mass % or less, more preferably 3.0 mass % or less, and even more preferably 2.0 mass % or less, based on the total amount of the non-aqueous electrolyte. When the upper limit of the content of the lithium fluorophosphate compound (VI) is within the above range, the solubility of the lithium fluorophosphate compound (VI) in the non-aqueous solvent can be ensured. The lower limit of the content of the lithium fluorophosphate compound (VI) 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, based on the total amount of the non-aqueous electrolyte solution. When the lower limit of the content of the lithium fluorophosphate compound (VI) is within the above range, the DC resistance of the electrochemical device can be further reduced.

[0079] <Non-aqueous solvent> The non-aqueous electrolyte generally contains a non-aqueous solvent. Various known non-aqueous solvents can be appropriately selected as the non-aqueous solvent. The non-aqueous solvent may be one type only or two or more types.

[0080] Examples of non-aqueous solvents include cyclic carbonates, fluorine-containing cyclic carbonates, chain carbonates, fluorine-containing chain carbonates, aliphatic carboxylic acid esters, fluorine-containing aliphatic carboxylic acid esters, γ-lactones, fluorine-containing γ-lactones, cyclic ethers, fluorine-containing cyclic ethers, chain ethers, fluorine-containing chain ethers, nitriles, amides, lactams, nitromethane, nitroethane, sulfolane, trimethyl phosphate, dimethyl sulfoxide, and dimethyl sulfoxide phosphate.

[0081] Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Examples of fluorine-containing cyclic carbonates include fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), and trifluoropropylene carbonate. Examples of chain carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and dipropyl carbonate (DPC). Examples of fluorine-containing chain carbonates include methyl 2,2,2-trifluoroethyl carbonate. Examples of aliphatic carboxylic acid esters include methyl formate, methyl acetate, methyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylbutyrate, ethyl formate, ethyl acetate, ethyl propionate, ethyl butyrate, ethyl isobutyrate, and ethyl trimethylbutyrate. Examples of the fluorine-containing aliphatic carboxylic acid esters include methyl difluoroacetate, methyl 3,3,3-trifluoropropionate, ethyl difluoroacetate, and 2,2,2-trifluoroethyl acetate. Examples of γ-lactones include γ-butyrolactone and γ-valerolactone. Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, and 1,4-dioxane. Examples of chain ethers include 1,2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, 1,2-dimethoxyethane, and 1,2-dibutoxyethane. Examples of fluorine-containing chain ethers include HCF2CF2CH2OCF2CF2H, CF3CF2CH2OCF2CF2H, HCF2CF2CH2OCF2CFHCF3, CF3CF2CH2OCF2CFHCF3, CF 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. Examples of nitriles include acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, and 3-methoxypropionitrile. Examples of amides include N,N-dimethylformamide. Examples of lactams include N-methylpyrrolidinone, N-methyloxazolidinone, and N,N'-dimethylimidazolidinone.

[0082] The non-aqueous solvent preferably contains at least one selected from the group consisting of cyclic carbonates, fluorine-containing cyclic carbonates, chain carbonates, and fluorine-containing chain carbonates. In this case, the total proportion of the cyclic carbonates, fluorine-containing cyclic carbonates, chain carbonates, and fluorine-containing chain carbonates is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 80% by mass or more and 100% by mass or less, based on the total amount of the non-aqueous solvent.

[0083] The non-aqueous solvent preferably contains at least one selected from the group consisting of cyclic carbonates and chain carbonates. In this case, the total proportion of the cyclic carbonates and chain carbonates in the non-aqueous solvent is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 80% by mass or more and 100% by mass or less, based on the total amount of the non-aqueous solvent.

[0084] The upper limit of the content of the non-aqueous solvent is preferably 99% by mass or less, more preferably 97% by mass or less, and further preferably 90% by mass or less, based on the total amount of the non-aqueous electrolyte. The lower limit of the content of the non-aqueous solvent is preferably 60 mass % or more, and more preferably 70 mass % or more, based on the total amount of the non-aqueous electrolyte.

[0085] The intrinsic viscosity of the non-aqueous solvent is preferably 10.0 mPa·s or less at 25° C., from the viewpoint of further improving the dissociation property of the electrolyte and the mobility of ions.

[0086] <Electrolytes> The non-aqueous electrolyte generally contains an electrolyte.

[0087] The electrolyte preferably contains at least one of a fluorine-containing lithium salt (hereinafter sometimes referred to as a "fluorine-containing lithium salt") and a fluorine-free lithium salt.

[0088] Examples of the fluorine-containing lithium salt include inorganic acid anion salts and organic acid anion salts. Examples of inorganic acid anion salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), and lithium hexafluorotantalate (LiTaF6). Examples of organic acid anion salts include lithium trifluoromethanesulfonate (LiCF3SO3), etc. Among these, LiPF6 is particularly preferred as the fluorine-containing lithium salt. Fluorine-free lithium salts include lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), and lithium decachlorodecaborate (Li2B 10 Cl 10 ) etc.

[0089] When the electrolyte contains a fluorine-containing lithium salt, the content of the fluorine-containing lithium salt is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 80% by mass or more and 100% by mass or less, based on the total amount of the electrolyte.

[0090] When the fluorine-containing lithium salt contains lithium hexafluorophosphate (LiPF6), the content of lithium hexafluorophosphate (LiPF6) is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 80% by mass or more and 100% by mass or less, based on the total amount of the electrolyte.

[0091] When the non-aqueous electrolyte contains an electrolyte, the concentration of the electrolyte in the non-aqueous electrolyte is preferably 0.1 mol / L or more and 3 mol / L or less, and more preferably 0.5 mol / L or more and 2 mol / L or less.

[0092] When the non-aqueous electrolyte contains lithium hexafluorophosphate (LiPF6), the concentration of lithium hexafluorophosphate (LiPF6) in the non-aqueous electrolyte is preferably 0.1 mol / L or more and 3 mol / L or less, more preferably 0.5 mol / L or more and 2 mol / L or less.

[0093] <Other ingredients> The non-aqueous electrolyte may contain other components as needed.

[0094] Other components include acid anhydrides.

[0095] [Electrochemical device precursors] Next, the electrochemical device precursor of the present disclosure will be described.

[0096] The electrochemical device precursor includes a case, a positive electrode, a negative electrode, a separator, and an electrolyte. The case accommodates the positive electrode, the negative electrode, the separator, and the electrolyte. The positive electrode is capable of absorbing and releasing lithium ions. The negative electrode is capable of absorbing and releasing lithium ions. The separator separates the positive electrode and the negative electrode. The electrolyte is the nonaqueous electrolyte solution of the present disclosure.

[0097] The electrochemical device precursor refers to an electrochemical device before charging and discharging, that is, in the electrochemical device precursor, the negative electrode does not include an SEI film, and the positive electrode does not include an SEI film.

[0098] <Case> The shape of the case is not particularly limited and may be appropriately selected depending on the application of the electrochemical device precursor, etc. Examples of the case include a case including a laminate film and a case consisting of a battery can and a battery can lid.

[0099] <Positive electrode> The positive electrode preferably contains at least one positive electrode active material that is capable of absorbing and releasing lithium ions.

[0100] The positive electrode includes a positive electrode current collector and a positive electrode mixture layer. The positive electrode mixture layer is provided on at least a portion of the surface of the positive electrode current collector.

[0101] Examples of the material for the positive electrode current collector include metals and alloys. Specifically, examples of the material for the positive electrode current collector include aluminum, nickel, stainless steel (SUS), and copper. Among these, from the viewpoint of the balance between high conductivity and cost, aluminum is preferred as the material for the positive electrode current collector. Here, "aluminum" refers to pure aluminum or an aluminum alloy. The positive electrode current collector is preferably aluminum foil. The material for the aluminum foil is not particularly limited, and examples include A1085 and A3003.

[0102] The positive electrode mixture layer contains a positive electrode active material and a binder.

[0103] The positive electrode active material is not particularly limited as long as it is a material that can absorb and release lithium ions, and can be adjusted appropriately depending on the application of the electrochemical device precursor, etc.

[0104] Examples of the positive electrode active material include a first oxide, a second oxide, and lithium metal phosphate. The first oxide contains lithium (Li) and nickel (Ni) as constituent metal elements. The second oxide contains Li, Ni, and at least one metal element other than Li and Ni as its constituent metal elements. Examples of metal elements other than Li and Ni include transition metal elements and typical metal elements. The second oxide preferably contains the metal elements other than Li and Ni in an amount equivalent to or less than Ni in atomic number terms. The metal element other than Li and Ni may be, for example, at least one selected from the group consisting of Co, Mn, Al, Cr, Fe, V, Mg, Ca, Na, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce. These positive electrode active materials may be used alone or in combination.

[0105] The positive electrode preferably contains, as a positive electrode active material, a lithium-containing composite oxide (hereinafter sometimes referred to as "NCM") represented by the following formula (X).

[0106] LiNi a Co b Mn c O2… Formula (X)

[0107] In formula (X), a, b, and c each independently represent a number greater than 0 and less than 1, and the sum of a, b, and c is 0.99 or greater and 1.00 or less.

[0108] NCM has the advantages of high energy density per unit volume and excellent thermal stability.

[0109] A specific example of NCM is LiNi 0.33 Co 0.33 Mn0.33 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 Examples include O2 and the like.

[0110] The positive electrode active material may contain a lithium-containing composite oxide represented by the following formula (Y) (hereinafter sometimes referred to as "NCA").

[0111] Li t Ni 1-x-y Co x Al y O2… Formula (Y) <\(0000666\)><\(0000667\)><\(0000668\)>In formula (Y), t is 0.95 or more and 1.15 or less, x is 0 or more and 0.3 or less, y is 0.1 or more and 0.2 or less, and the sum of x and y is less than 0.5. <\(0000669\)><\(0000670\)><\(0000671\)>Specific examples of NCA include LiNi<\(0000110\)>Co<\(0000111\)>Al<\(0000112\)>O2 and the like. <\(0000672\)><\(\\(0000673\)><\(0000674\)>Examples of lithium metal phosphate include, for example, lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO < (1-X) > 4), lithium manganese iron phosphate (LiMn<\(0000113\)>Fe<\(0000114\)>PO4; 0 < X < 1) and the like. Lithium metal phosphate is preferably lithium iron phosphate. <\(0000675\)><\(0000676\)><\(0000677\)>When the positive electrode includes a positive electrode current collector and a positive electrode composite layer containing a positive electrode active material and a binder, the lower limit of the content of the positive electrode active material in the positive electrode composite layer is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, and particularly preferably 70% by mass or more, relative to the total amount of the positive electrode composite layer. The upper limit of the content of the positive electrode active material in the positive electrode mixture layer is preferably 99.9 mass % or less, and more preferably 99 mass % or less, based on the total amount of the positive electrode mixture layer.

[0116] Examples of binders include polyvinyl acetate, polymethyl methacrylate, nitrocellulose, fluororesin, and rubber particles. Examples of fluororesins include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and vinylidene fluoride-hexafluoropropylene copolymer. Examples of rubber particles include styrene-butadiene rubber particles and acrylonitrile rubber particles. Among these, from the viewpoint of improving the oxidation resistance of the positive electrode mixture layer, fluororesin is preferred as the binder. One type of binder can be used alone, or two or more types can be used in combination as necessary.

[0117] The content of the binder in the positive electrode mixture layer is preferably 0.1% by mass or more and 4% by mass or less, based on the total amount of the positive electrode mixture layer, from the viewpoint of achieving both the physical properties of the positive electrode mixture layer (e.g., electrolyte permeability, peel strength, etc.) and battery performance. When the binder content is 0.1% by mass or more, the adhesion of the positive electrode mixture layer to the positive electrode current collector and the binding strength between the positive electrode active materials are further improved. When the binder content is 4% by mass or less, the amount of positive electrode active material in the positive electrode mixture layer can be increased, thereby further improving capacity.

[0118] The positive electrode mixture layer preferably contains a conductive additive.

[0119] Known conductive additives can be used as the material for the conductive additive. As known conductive additives, conductive carbon materials are preferred. Examples of conductive carbon materials include graphite, carbon black, conductive carbon fiber, and fullerene. These can be used alone or in combination of two or more. Examples of conductive carbon fibers include carbon nanotubes, carbon nanofibers, and carbon fibers. Examples of graphite include artificial graphite and natural graphite. Examples of natural graphite include flake graphite, lump graphite, and amorphous graphite.

[0120] The conductive additive may be a commercially available product. Examples of commercially available carbon black include Toka Black #4300, #4400, #4500, #5500 (furnace black manufactured by Tokai Carbon Co., Ltd.), Printex L (furnace black manufactured by Degussa Corporation), Raven 7000, 5750, 5250, 5000ULTRA III, 5000ULTRA, Conductex SC ULTRA, Conductex 975ULTRA, and PUER BLACK100, 115, 205, etc. (Columbian Furnace Black), #2350, #2400B, #2600B, #30050B, #3030B, #3230B, #3350B, #3400B, #5400B, etc. (Mitsubishi Chemical Furnace Black), MONARCH1400, 1300, 900, VulcanXC-72R, BlackPearls2000, Examples include LITX-50, LITX-200 (furnace black, manufactured by Cabot Corporation), Ensaco250G, Ensaco260G, Ensaco350G, Super-P (manufactured by TIMCAL), Ketjenblack EC-300J, EC-600JD (manufactured by Akzo), Denkablack, Denkablack HS-100, FX-35 (acetylene black, manufactured by Denka Co., Ltd.), and the like.

[0121] The positive electrode mixture layer may contain other components such as a thickener, a surfactant, a dispersant, a wetting agent, and an antifoaming agent.

[0122] <Negative electrode> The negative electrode contains at least one negative electrode active material that is capable of absorbing and releasing lithium ions.

[0123] More preferably, the negative electrode includes a negative electrode current collector and a negative electrode mixture layer, the negative electrode mixture layer being provided on at least a portion of the surface of the negative electrode current collector.

[0124] The material of the negative electrode current collector is not particularly limited and any known material can be used, for example, a metal or alloy. Specifically, the material of the negative electrode current collector can be aluminum, nickel, stainless steel (SUS), nickel-plated steel, copper, etc. Among them, copper is preferred as the material of the negative electrode current collector from the viewpoint of workability. Copper foil is preferred as the negative electrode current collector.

[0125] The negative electrode mixture layer contains a negative electrode active material and a binder.

[0126] The negative electrode active material is not particularly limited as long as it is a material capable of absorbing and releasing lithium ions. The negative electrode active material is preferably at least one material selected from the group consisting of metallic lithium, lithium-containing alloys, metals or alloys capable of alloying with lithium, oxides capable of doping and dedoping lithium ions, transition metal nitrides capable of doping and dedoping lithium ions, and carbon materials capable of doping and dedoping lithium ions. Among these, the negative electrode active material is preferably a carbon material capable of doping and dedoping lithium ions (hereinafter referred to as "carbon material").

[0127] Examples of carbon materials include carbon black, activated carbon, graphite materials, and amorphous carbon materials. These carbon materials may be used alone or in combination of two or more. The form of the carbon material is not particularly limited, and examples include fibrous, spherical, and flake forms. The particle size of the carbon material is not particularly limited, and is preferably 5 μm or more and 50 μm or less, more preferably 20 μm or more and 30 μm or less. Examples of amorphous carbon materials include hard carbon, coke, mesocarbon microbeads (MCMB) fired at 1500° C. or less, and mesophase pitch carbon fiber (MCF). Examples of graphite materials include natural graphite and artificial graphite. Examples of artificial graphite include graphitized MCMB and graphitized MCF. The graphite material may contain boron. The graphite material may be coated with a metal or amorphous carbon. Examples of metal materials that coat the graphite material include gold, platinum, silver, copper, and tin. The graphite material may be a mixture of amorphous carbon and graphite.

[0128] The negative electrode mixture layer preferably contains a conductive additive. Examples of the conductive additive include the same conductive additives as those exemplified as the conductive additives that can be contained in the positive electrode mixture layer.

[0129] In addition to the above components, the negative electrode mixture layer may contain other components such as a thickener, a surfactant, a dispersant, a wetting agent, and an antifoaming agent.

[0130] <separator> The separator may be, for example, a porous resin plate. Materials for the porous resin plate include resin and nonwoven fabric containing the resin. Examples of resin include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyester, cellulose, and polyamide.

[0131] In particular, the separator is preferably a porous resin sheet having a single layer or a multilayer structure. The porous resin sheet is mainly made of one or more polyolefin resins. The thickness of the separator is preferably 5 μm or more and 30 μm or less. The separator is preferably disposed between the positive electrode and the negative electrode.

[0132] [Example of electrochemical device precursor] An example of an electrochemical device precursor 1 according to an embodiment of the present disclosure will be specifically described with reference to Fig. 1. Fig. 1 is a cross-sectional view of an electrochemical device precursor 1 according to an embodiment of the present disclosure.

[0133] The electrochemical device precursor 1 is a laminated type. As shown in FIG. 1 , the electrochemical device precursor 1 includes a battery element 10, a positive electrode lead 21, a negative electrode lead 22, and an exterior body 30. The battery element 10 is enclosed inside the exterior body 30. The exterior body 30 is formed of a laminate film. The positive electrode lead 21 and the negative electrode lead 22 are each attached to the battery element 10. The positive electrode lead 21 and the negative electrode lead 22 are each led out in opposite directions, from the inside to the outside of the exterior body 30.

[0134] As shown in Fig. 1, battery element 10 is formed by laminating positive electrode 11, separator 13, and negative electrode 12. Positive electrode 11 has positive electrode composite layers 11B formed on both main surfaces of positive electrode current collector 11A. Negative electrode 12 has negative electrode composite layers 12B formed on both main surfaces of negative electrode current collector 12A. Positive electrode composite layer 11B formed on one main surface of positive electrode current collector 11A of positive electrode 11 and negative electrode composite layer 12B formed on one main surface of negative electrode current collector 12A of negative electrode 12 adjacent to positive electrode 11 face each other via separator 13.

[0135] The nonaqueous electrolyte solution according to this embodiment is poured into the exterior casing 30 of the electrochemical device precursor 1. The nonaqueous electrolyte solution according to this embodiment permeates the positive electrode composite layer 11B, the separator 13, and the negative electrode composite layer 12B. In the electrochemical device precursor 1, adjacent positive electrode composite layers 11B, separators 13, and negative electrode composite layers 12B form one cell layer 14. The positive electrode 11 may be formed by forming the positive electrode composite layer 11B on one main surface of a positive electrode current collector 11A, and the negative electrode 12 may be formed by forming the negative electrode composite layer 12B on one main surface of a negative electrode current collector 12A.

[0136] In this embodiment, the electrochemical device precursor 1 is a laminated type, but the present disclosure is not limited to this, and the electrochemical device precursor 1 may be, for example, a wound type. A wound type is formed by stacking a positive electrode, a separator, a negative electrode, and a separator in this order and winding them into a layered configuration. The wound type includes a cylindrical type and a rectangular type. 1 , the directions in which the positive electrode lead 21 and the negative electrode lead 22 protrude from the inside of the exterior body 30 to the outside are opposite directions relative to the exterior body 30, but the present disclosure is not limited to this. For example, the directions in which the positive electrode lead and the negative electrode lead protrude from the inside of the exterior body 30 to the outside may be the same direction relative to the exterior body 30.

[0137] An example of an electrochemical device according to an embodiment of the present disclosure described below is an electrochemical device in which an SEI film is formed on each surface of a positive electrode composite layer 11B and a negative electrode composite layer 12B in an electrochemical device precursor 1 by charging and discharging the electrochemical device precursor 1.

[0138] [Electrochemical Devices] Next, the electrochemical device of the present disclosure will be described.

[0139] The electrochemical device of the present disclosure is obtained by charging and discharging an electrochemical device precursor. Specifically, the electrochemical device includes a case, a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode, the negative electrode, the separator, and the electrolyte are housed in the case. The positive electrode is capable of absorbing and releasing lithium ions. The negative electrode is capable of absorbing and releasing lithium ions. The electrolyte is the nonaqueous electrolyte solution of the present disclosure. The negative electrode includes an SEI film. The positive electrode includes an SEI film.

[0140] The electrochemical device differs from the electrochemical device precursor mainly in the first point that the negative electrode includes an SEI film and the second point that the positive electrode includes an SEI film. That is, the electrochemical device is similar to the electrochemical device precursor except for the first and second points. Therefore, hereinafter, a description of the components of the electrochemical device other than the first and second points will be omitted.

[0141] Regarding the first point, when the negative electrode includes a negative electrode current collector and a negative electrode composite layer, the phrase "the negative electrode includes an SEI film" includes a first negative electrode form and a second negative electrode form. The first negative electrode form refers to a form in which an SEI film is formed on at least a portion of the surface of the negative electrode composite layer. The second negative electrode form refers to a form in which an SEI film is formed on the surface of a negative electrode active material, which is a constituent material of the negative electrode composite layer.

[0142] Regarding the second point, when the positive electrode includes a positive electrode current collector and a positive electrode composite layer, the phrase "the positive electrode includes an SEI film" includes a first positive electrode form and a second positive electrode form. The first positive electrode form refers to a form in which an SEI film is formed on at least a portion of the surface of the positive electrode composite layer. The second positive electrode form refers to a form in which an SEI film is formed on the surface of a positive electrode active material, which is a constituent material of the positive electrode composite layer.

[0143] The SEI membrane contains, for example, at least one selected from the group consisting of decomposition products of the fluorinated lithium sulfonate compound (I), decomposition products of the cyclic sulfone compound (II), reaction products of the fluorinated lithium sulfonate compound (I) or the cyclic sulfone compound (II) with an electrolyte, and decomposition products of the reaction products.

[0144] The components of the SEI film of the positive electrode and the components of the SEI film of the negative electrode may be the same or different, and the thicknesses of the SEI film of the positive electrode and the SEI film of the negative electrode may be the same or different.

[0145] [Method for producing electrochemical device precursor] Next, a method for producing an electrochemical device precursor according to an embodiment of the present disclosure will be described.

[0146] The method for manufacturing an electrochemical device precursor according to this embodiment includes a first preparation step, a second preparation step, a third preparation step, a containing step, and a pouring step. The containing step and the pouring step are performed in this order. The first preparation step, the second preparation step, and the third preparation step are each performed before the containing step.

[0147] In the first preparation step, a positive electrode is prepared. The positive electrode can be prepared, for example, by applying a positive electrode mixture slurry to the surface of a positive electrode current collector and drying the slurry. The positive electrode mixture slurry contains a positive electrode active material and a binder. The solvent contained in the positive electrode mixture slurry is preferably an organic solvent, such as N-methyl-2-pyrrolidone (NMP). The method for applying the positive electrode mixture slurry is not particularly limited, and examples thereof include slot die coating, slide coating, curtain coating, and gravure coating. The method for drying the positive electrode mixture slurry is not particularly limited, and examples thereof include drying with warm air, hot air, or low-humidity air; vacuum drying; and drying by infrared (e.g., far-infrared) irradiation. The drying time is not particularly limited, and is preferably 1 minute to 30 minutes. The drying temperature is not particularly limited, and is preferably 40°C to 80°C. The cathode mixture slurry is applied to a cathode current collector, and the dried product is preferably subjected to a pressure treatment. This reduces the porosity of the cathode mixture layer. Examples of pressure treatment methods include die pressing and roll pressing.

[0148] In the second preparation step, a negative electrode is prepared. The negative electrode can be prepared, for example, by applying a negative electrode mixture slurry to the surface of a negative electrode current collector and drying the slurry. The negative electrode mixture slurry contains a negative electrode active material and a binder. Examples of the solvent contained in the negative electrode mixture slurry include water and a liquid medium compatible with water. When the solvent contained in the negative electrode mixture slurry includes a liquid medium compatible with water, the coating properties on the negative electrode current collector can be improved. Examples of the liquid medium compatible with water include alcohols, glycols, cellosolves, aminoalcohols, amines, ketones, carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid esters, phosphoric acid esters, ethers, and nitriles. Examples of the method for applying, drying, and pressurizing the negative electrode mixture slurry include the same methods as those exemplified as the method for applying, drying, and pressurizing the positive electrode mixture slurry.

[0149] In the third preparation step, a non-aqueous electrolyte is prepared. A method for preparing the non-aqueous electrolyte solution includes, for example, a step of dissolving an electrolyte in a non-aqueous solvent to obtain a solution, and a step of adding and mixing the fluorinated lithium sulfonate compound (I) and the cyclic sulfone compound (II) to the obtained solution to obtain the non-aqueous electrolyte solution.

[0150] In the housing step, the positive electrode, the negative electrode, and the separator are housed in a case. For example, in the housing step, a battery element is fabricated from a positive electrode, a negative electrode, and a separator. Next, the positive electrode current collector of the positive electrode is electrically connected to the positive electrode lead, and the negative electrode current collector of the negative electrode is electrically connected to the negative electrode lead. Next, the battery element is housed and fixed in a case. The method for electrically connecting the positive electrode current collector and the positive electrode lead is not particularly limited, and examples thereof include ultrasonic welding, resistance welding, etc. The method for electrically connecting the negative electrode current collector and the negative electrode lead is not particularly limited, and examples thereof include ultrasonic welding, resistance welding, etc.

[0151] Hereinafter, the state in which the positive electrode, negative electrode, and separator are housed in the case will be referred to as an "assembly."

[0152] In the injection step, the nonaqueous electrolyte solution according to the present embodiment is injected into the assembly, thereby allowing the nonaqueous electrolyte solution to permeate the positive electrode mixture layer, the separator, and the negative electrode mixture layer, thereby obtaining an electrochemical device precursor.

[0153] [Method for manufacturing an electrochemical device] Next, a method for manufacturing an electrochemical device according to an embodiment of the present disclosure will be described.

[0154] The method for manufacturing an electrochemical device according to this embodiment includes a fourth preparation step and an aging step, which are performed in this order.

[0155] In the fourth preparation step, an electrochemical device precursor is prepared by the same method as that described in the method for producing an electrochemical device precursor.

[0156] In the aging step, the electrochemical device precursor is charged and discharged, thereby forming an SEI film, and thus obtaining an electrochemical device.

[0157] Hereinafter, the treatment of charging and discharging the electrochemical device precursor will be referred to as "aging treatment."

[0158] The aging treatment may be carried out in an environment of 25°C or higher and 70°C or lower. The aging process may include a first charging phase, a first holding phase, a second charging phase, a second holding phase, and a charge / discharge phase.

[0159] In the first charging phase, the electrochemical device precursor is charged in an environment of 25°C or higher and 70°C or lower. In the first holding phase, the electrochemical device precursor after the first charging phase is held in an environment of 25°C or higher and 70°C or lower. In the second charging phase, the electrochemical device precursor after the first holding phase is charged in an environment of 25°C or higher and 70°C or lower. In the second holding phase, the electrochemical device precursor after the second charging phase is held in an environment of 25°C or higher and 70°C or lower. In the charge / discharge phase, the electrochemical device precursor after the second holding phase is subjected to one or more combinations of charging and discharging in an environment of 25°C or higher and 70°C or lower.

[0160] Even if the electrochemical device obtained by the method for producing an electrochemical device according to this embodiment is stored in a high-temperature environment for a long period of time, the effect of suppressing a decrease in capacity and an increase in DC resistance of the electrochemical device is more effectively exhibited. [Example]

[0161] Hereinafter, embodiments of the present disclosure will be described in detail with reference to examples, but the present disclosure is not limited to the descriptions of these examples.

[0162] Example 1-1 A non-aqueous electrolyte solution was prepared as follows.

[0163] (Preparation of non-aqueous electrolyte) Ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC) were mixed in a volume ratio of EC:DMC:EMC = 30:35:35 to obtain a mixed solvent (non-aqueous solvent). LiPF6 (electrolyte) was dissolved in the resulting mixed solvent so that the concentration in the finally obtained non-aqueous electrolyte solution was 1 mol / L, to obtain an electrolyte solution.

[0164] Hereinafter, the obtained electrolyte solution will be referred to as the "basic electrolyte solution."

[0165] The fluorinated lithium sulfonate compound (I) and the cyclic sulfone compound (II-1) were added as additives to the base electrolyte solution in amounts (mass%) relative to the total amount of the finally obtained non-aqueous electrolyte solution shown in Table 1. In this way, a non-aqueous electrolyte solution was obtained. The fluorinated lithium sulfonate compound (I) is represented by the following formula (I): The cyclic sulfone compound (II-1) is represented by the following formula (II-1).

[0166] [ka]

[0167] <Preparation of electrochemical device precursors> An aluminum laminated battery was fabricated as an electrochemical device precursor in the following manner.

[0168] (1st preparation step) The positive electrode was prepared as follows. Li(Ni) as the positive electrode active material 0.5 Co 0.2 Mn 0.3 A first mixture was prepared by adding 94% by mass of ZnO (O2), 3% by mass of carbon black as a conductive additive, and 3% by mass of polyvinylidene fluoride (PVDF) as a binder. The first mixture was dispersed in N-methylpyrrolidone solvent to prepare a positive electrode mixture slurry. An aluminum foil with a thickness of 20 μm was prepared as a positive electrode current collector. The obtained positive electrode mixture slurry was applied to an aluminum foil (positive electrode current collector), dried, and then rolled with a press to obtain a positive electrode blank. This positive electrode blank includes a region where a positive electrode active material mixture layer (hereinafter referred to as "positive electrode mixture layer") is formed and a region where no positive electrode mixture layer is formed (hereinafter referred to as "uncoated portion for tab bonding"). The uncoated portion for tab bonding is an uncoated portion that serves as a margin. The resulting positive electrode blank was slit to obtain a positive electrode. The positive electrode had a positive electrode composite layer and an uncoated portion for tab bonding. The positive electrode composite layer had a width of 29 mm and a length of 40 mm. The uncoated portion for tab bonding had a width of 5 mm and a length of 11 mm.

[0169] (Second preparation process) The negative electrode was prepared as follows. Graphite (96% by mass) was used as the negative electrode active material, carbon black (1% by mass) was used as a conductive additive, 1% by mass of sodium carboxymethyl cellulose dispersed in pure water as a thickener (solid content), and 2% by mass of styrene-butadiene rubber (SBR) dispersed in pure water as a binder (solid content) were mixed to obtain a negative electrode mixture slurry. A copper foil with a thickness of 10 μm was prepared as a negative electrode current collector. The obtained negative electrode mixture slurry was applied to a copper foil (negative electrode current collector), dried, and then rolled with a press to obtain a negative electrode blank. This negative electrode blank includes a region where a negative electrode active material mixture layer (hereinafter referred to as "negative electrode mixture layer") is formed and a region where no negative electrode mixture layer is formed (hereinafter referred to as "uncoated portion for tab bonding"). The uncoated portion for tab bonding is an uncoated portion that serves as a margin. The resulting negative electrode blank was slit to obtain a negative electrode. The negative electrode had a negative electrode composite layer and an uncoated portion for tab bonding. The size of the negative electrode composite layer was 30 mm wide and 41 mm long. The size of the uncoated portion for tab bonding was 5 mm wide and 11 mm long.

[0170] (3rd preparation step) The non-aqueous electrolyte obtained by the above-described non-aqueous electrolyte production was prepared.

[0171] (Storage process) A porous polypropylene film was prepared as a separator. A laminate was obtained by stacking the positive electrode, negative electrode, and separator so that the coated surface of the negative electrode was in contact with the separator and the coated surface of the positive electrode was in contact with the separator. An aluminum positive electrode tab (positive electrode lead) was then bonded to the uncoated tab-bonding portion of the positive electrode of the resulting laminate using an ultrasonic bonding machine. A nickel negative electrode tab (negative electrode lead) was then bonded to the uncoated tab-bonding portion of the negative electrode of the resulting laminate using an ultrasonic bonding machine. The laminate with the bonded positive and negative electrode tabs was sandwiched between a pair of laminate films (cases) in which both sides of the aluminum were coated with a resin layer, and then three sides were heat-sealed to obtain a laminate (assembly). At this time, the positive and negative electrode tabs were allowed to protrude from one of the three sealed sides of the laminate that was adjacent to the unsealed opening.

[0172] (Injection process) The nonaqueous electrolyte solution obtained above was poured into the opening of the laminate, and the opening of the laminate was sealed, thereby obtaining an aluminum laminate battery (electrochemical device precursor).

[0173] [Examples 1-2 to 2-4, Comparative Examples 1-1 to 2-1] An aluminum laminated battery (electrochemical device precursor) was obtained in the same manner as in Example 1-1, except that the additives, fluorinated lithium sulfonate compound (I), cyclic sulfone compound (II-2), cyclic sulfone compound (C-1), vinylene carbonate compound (III-11), and sulfonimide lithium salt compound (IV-1), were added to the base electrolyte solution in amounts (mass %) shown in Table 1 or Table 2 relative to the total amount of the non-aqueous electrolyte solution finally obtained. The fluorinated lithium sulfonate compound (I) is represented by the following formula (I). The cyclic sulfone compound (II-2) is represented by the following formula (II-2). The cyclic sulfone compound (C-1) is represented by the following formula (C-1). The vinylene carbonate compound (III-11) is represented by the following formula (III-11). The sulfonimide lithium salt compound (IV-1) is represented by the following formula (IV-1).

[0174] [ka]

[0175] [First Evaluation Test: Examples 1-1 to 2-4 and Comparative Examples 1-1 to 2-1] A first evaluation test of the aluminum laminate batteries obtained in Examples 1-1 to 2-4 and Comparative Examples 1-1 to 2-1 was carried out as follows. The resulting aluminum laminated battery was subjected to the first aging treatment described below to obtain a first battery. The resulting first battery was subjected to the first initial charge / discharge treatment described below to obtain a second battery. The resulting second battery was subjected to the first DC resistance evaluation treatment described below to obtain a third battery. The resulting third battery was subjected to the first high-temperature storage treatment to obtain a fourth battery. The resulting fourth battery was subjected to the first later charge / discharge treatment described below to obtain a fifth battery. The initial resistance, resistance after high-temperature storage, initial capacity, and capacity after high-temperature storage were measured for the resulting first to fifth batteries by the following measurement methods. The measurement results are shown in Tables 1 and 2.

[0176] <First aging treatment> The aluminum laminated battery (electrochemical device battery precursor) was subjected to the following first aging treatment to obtain a first battery. An aluminum laminated battery (electrochemical device battery precursor) was charged at a temperature range of 25°C to 70°C with an end voltage range of 1.5V to 3.5V, and then left to rest for 5 to 50 hours. Next, the battery precursor was charged at a temperature range of 25°C to 70°C with an end voltage range of 3.5V to 4.2V, and held for 5 to 50 hours. Next, the battery precursor was charged to 4.2V at a temperature range of 25°C to 70°C, and then discharged to 2.5V. This produced a first battery.

[0177] <First initial charge / discharge process> The first battery was subjected to the following first initial charge / discharge treatment to obtain a second battery. The first battery was stored in a temperature environment of 25°C for 12 hours. Next, the first battery was subjected to a cycle (hereinafter referred to as a "stabilization cycle") in which the first battery was charged at a constant current and constant voltage (0.2C-CCCV) at a charge rate of 0.2C to 4.2V (SOC (State of Charge) 100%), then rested for 30 minutes, and then discharged at a constant current (0.2C-CC) at a discharge rate of 0.2C to 2.5V. This stabilization cycle was performed a total of three times on the first battery to stabilize the first battery. Thereafter, the first battery was subjected to a first charge, followed by a 30-minute rest, and then a first discharge. The first charge refers to a constant current and constant voltage charge (0.5C-CCCV) at a charge rate of 0.2C to 4.2V. The first discharge refers to a constant current discharge (1C-CC) at a discharge rate of 1C to 2.5V. This resulted in a second battery.

[0178] <First DC Resistance Evaluation Process> The second battery was subjected to the following first DC resistance evaluation treatment to obtain a third battery. The second battery was CCCV charged to 3.7 V at a charge rate of 0.2 C in a temperature environment of 25°C. "CCCV charging" means charging at a constant current and constant voltage. Next, the second battery was subjected to CC10s discharge at a discharge rate of 1C and CC10s charge at a charge rate of 1C in a temperature environment of 25°C. "CC10s discharge" means discharging at a constant current for 10 seconds. "CC10s charge" means charging at a constant current for 10 seconds. Next, the second battery was subjected to CC10s discharge at a discharge rate of 2C and CC20s charge at a charge rate of 1C. Next, the second battery was subjected to CC10s discharge at a discharge rate of 3C and CC30s charge at a charge rate of 1C. Next, the second battery was subjected to CC10s discharge at a discharge rate of 4C and CC40s charge at a charge rate of 1C. Next, the second battery was subjected to CC10s discharge at a discharge rate of 5 C and CC50s charge at a charge rate of 1 C. In this way, a third battery was obtained.

[0179] <First high-temperature preservation treatment> The third battery was subjected to the following first high-temperature storage treatment to obtain a fourth battery. The third battery was charged at a constant current of 0.2 C to 4.2 V in a temperature environment of 25° C. The third battery in the charged state was then left to stand in an atmosphere of 60° C. for 28 days, thereby obtaining a fourth battery.

[0180] <First stage charge / discharge treatment> The fourth battery was subjected to the first later charge-discharge treatment described below to obtain a fifth battery. The fourth battery was cooled in a 25°C environment, and then subjected to a second discharge, a second charge, and a third discharge. The second discharge refers to a constant current discharge (1C-CC) to 2.5V at a discharge rate of 1C. The second charge refers to a constant current / constant voltage charge (0.2C-CCCV) to 4.2V at a charge rate of 0.2C. The third discharge refers to a constant current discharge (1C-CC) to 2.5V at a discharge rate of 1C. This resulted in the fifth battery.

[0181] <Method for measuring initial resistance> As shown in the following formula (X1), the relative value of the direct current internal resistance (DCIR) of the second battery of Comparative Example 1-2, Example 1-1, or Example 1-2 to the direct current internal resistance (DCIR) of the second battery of Comparative Example 1-1 was defined as the "initial resistance [%]" (see Table 1). As shown in the following formula (X1), the relative value of the DC resistance of the second battery of Example 2-1, Example 2-2, Example 2-3, or Example 2-4 to the DC resistance of the second battery of Comparative Example 2-1 was defined as "initial resistance [%]" (see Table 2).

[0182] Initial resistance [relative value; %] = (DC resistance of second battery [Ω] / DC resistance of second battery of Comparative Example 1-1 or Comparative Example 2-1 [Ω]) × 100 (X1)

[0183] In the first evaluation test, the DC resistance of the second battery was measured by the following method. That is, when the second battery was subjected to the first DC resistance evaluation process, the DC resistance (Ω) of the second battery was calculated based on the amount of voltage drop (= voltage before the start of discharge - voltage 10 seconds after the start of discharge) due to "CC10s discharge" at each of the discharge rates of 1C to 5C and each current value (i.e., each current value corresponding to the discharge rates of 1C to 5C).

[0184] <Method for measuring resistance after high temperature storage> As shown in the following formula (X2), the relative value of the DC resistance of the fifth battery of Comparative Example 1-2, Example 1-1, or Example 1-2 to the DC resistance of the fifth battery of Comparative Example 1-1 was defined as the "resistance after high-temperature storage [%]" (see Table 1). As shown in the following formula (X2), the relative value of the DC resistance of the fifth battery of Example 2-1, Example 2-2, Example 2-3, or Example 2-4 to the DC resistance of the fifth battery of Comparative Example 2-1 was defined as the "resistance after high-temperature storage [%]" (see Table 2).

[0185] Resistance after high-temperature storage [relative value; %] = (DC resistance [Ω] of the fifth battery / DC resistance [Ω] of the fifth battery of Comparative Example 1-1 or Comparative Example 2-1) × 100 (X2)

[0186] In the first evaluation test, the DC resistance of the fifth battery was measured by the following method. That is, the fifth battery was subjected to a DC resistance evaluation process similar to the first DC resistance evaluation process described above. The DC resistance (Ω) of the fifth battery was calculated based on the voltage drop (= voltage before discharge start - voltage 10 seconds after discharge start) due to "CC10s discharge" at each of the discharge rates of 1C to 5C and each current value (i.e., each current value corresponding to the discharge rates of 1C to 5C).

[0187] <Method for measuring initial capacity> As shown in the following formula (X3), the relative value of the initial capacity of the first battery of Comparative Example 1-2, Example 1-1, or Example 1-2 to the initial capacity of the first battery of Comparative Example 1-1 was defined as "initial capacity [%]" (see Table 1). As shown in the following formula (X3), the relative value of the initial capacity of the first battery of Example 2-1, Example 2-2, Example 2-3, or Example 2-4 to the initial capacity of the first battery of Comparative Example 2-1 was defined as "initial capacity [%]" (see Table 2).

[0188] Initial capacity [relative value; %] = (initial capacity [mAh / g] of first battery / initial capacity [mAh / g] of first battery of Comparative Example 1-1 or Comparative Example 2-1) × 100 (X4)

[0189] In the first evaluation test, the initial capacity of the first battery indicates the capacity obtained when the first discharge was performed in the first initial charge / discharge treatment described above.

[0190] <Method for measuring capacity after high-temperature storage> As shown in the following formula (X4), the relative value of the post-high-temperature storage capacity of the fourth battery of Comparative Example 1-2, Example 1-1, or Example 1-2 to the post-high-temperature storage capacity of the fourth battery of Comparative Example 1-1 was defined as "post-high-temperature storage capacity [%]" (see Table 1). As shown in the following formula (X4), the relative value of the post-high-temperature storage capacity of the fourth battery of Example 2-1, Example 2-2, Example 2-3, or Example 2-4 to the post-high-temperature storage capacity of the fourth battery of Comparative Example 2-1 was defined as "post-high-temperature storage capacity [%]" (see Table 2).

[0191] Capacity after high-temperature storage [relative value; %] = (Capacity after high-temperature storage of the fourth battery [mAh / g] / Capacity after high-temperature storage of the fourth battery of Comparative Example 1-1 or Comparative Example 2-1 [mAh / g]) × 100 (X4)

[0192] In the first evaluation test, the post-high-temperature storage capacity of the fourth battery indicates the capacity obtained when the battery was subjected to the third discharge in the first later charge-discharge treatment described above.

[0193] Example 3-1 An aluminum laminate type battery (electrochemical device precursor) was obtained in the same manner as in Example 1-1, except that the second mixture described below was used instead of the first mixture in the first preparation step. The second mixture was obtained by adding LiFePO4 (96 mass%) as a positive electrode active material, carbon black (1.5 mass%) as a conductive additive, and polyvinylidene fluoride (PVDF) (2.5 mass%) as a binder.

[0194] [Example 3-2, Comparative Example 3-1, Comparative Example 3-2] An aluminum laminated battery (electrochemical device precursor) was obtained in the same manner as in Example 3-1, except that the additives, fluorinated lithium sulfonate compound (I), cyclic sulfone compound (II-2), and cyclic sulfone compound (C-1), were added to the base electrolyte solution in amounts (mass %) shown in Table 3 relative to the total amount of the non-aqueous electrolyte solution finally obtained.

[0195] [Second Evaluation Test: Examples 3-1 and 3-2, and Comparative Examples 3-1 and 3-1] A second evaluation test was carried out on the aluminum laminate batteries obtained in Examples 3-1 and 3-2 and Comparative Examples 3-1 and 3-2. In the second evaluation test, the fifth battery was obtained in the same manner as in the first evaluation test, except that the second aging treatment described below was performed instead of the first aging treatment, the second initial charge / discharge treatment described below was performed instead of the first initial charge / discharge treatment, the second DC resistance evaluation treatment described below was performed instead of the first DC resistance evaluation treatment, the second high-temperature storage treatment described below was performed instead of the first high-temperature storage treatment, and the first final charge / discharge treatment was performed instead of the first final charge / discharge treatment. The initial resistance, resistance after high-temperature storage, initial capacity, and capacity after high-temperature storage were measured using the obtained batteries Nos. 1 to 5. The measurement results are shown in Table 3.

[0196] <Second aging treatment> The aluminum laminated battery (electrochemical device battery precursor) was subjected to the second aging treatment described below to obtain a first battery. An aluminum laminated battery (electrochemical device battery precursor) was charged at a temperature range of 25°C to 70°C with a cut-off voltage range of 1.5V to 3.0V, and then allowed to rest for 5 to 50 hours. Next, the battery precursor was charged at a temperature range of 25°C to 70°C with a cut-off voltage range of 3.0V to 3.7V, and then discharged to 2.0V. This produced a first battery.

[0197] <Second initial charge / discharge process> The first battery was subjected to the second initial charge-discharge treatment described below to obtain a second battery. The first battery was stored in a 25°C temperature environment for 12 hours. The first battery was then subjected to a cycle (hereinafter referred to as the "stabilization cycle") in which it was charged at a constant current and constant voltage (0.5C-CCCV) at a charge rate of 0.2C to 3.65V (SOC (State of Charge) 100%), then rested for 30 minutes, and then discharged at a constant current (0.5C-CC) at a discharge rate of 0.5C to 2.0V. This stabilization cycle was repeated twice to stabilize the first battery. The third charge was then performed, followed by a 30-minute rest, and a fourth discharge. The third charge represented a constant current and constant voltage charge (0.5C-CCCV) at a charge rate of 0.5C to 3.65V. The fourth discharge represented a constant current discharge (0.5C-CC) at a discharge rate of 0.5C to 2.0V. This resulted in the second battery.

[0198] <Second DC Resistance Evaluation Process> The second battery was subjected to the second DC resistance evaluation treatment described below to obtain a third battery. The second battery was CCCV charged to 3.55 V at a charge rate of 0.5 C in a temperature environment of 25°C. "CCCV charging" means charging at a constant current and constant voltage. Next, the second battery was subjected to CC10s discharge at a discharge rate of 0.5C and CC50s charge at a charge rate of 0.1C in a temperature environment of 25°C. "CC10s discharge" means discharging at a constant current for 10 seconds. "CC50s charge" means charging at a constant current for 50 seconds. Next, the second battery was subjected to CC10s discharge at a discharge rate of 0.8C and CC80s charge at a charge rate of 0.1C. Next, the second battery was subjected to CC10s discharge at a discharge rate of 1.0C and CC100s charge at a charge rate of 0.1C. Next, the second battery was subjected to CC10s discharge at a discharge rate of 1.5 C and CC150s charge at a charge rate of 0.1 C. This produced a third battery.

[0199] <Second high-temperature preservation treatment> The third battery was subjected to the second high-temperature storage treatment described below to obtain a fourth battery. The third battery was charged at a constant current and constant voltage at a charge rate of 0.5 C to 3.65 V in a temperature environment of 25° C. Then, the third battery in the charged state was left standing in an atmosphere of 60° C. for 14 days, thereby obtaining a fourth battery.

[0200] <Second-stage charge / discharge treatment> The fourth battery was subjected to the second later charge-discharge treatment described below to obtain a fifth battery. The fourth battery was cooled in a 25°C environment, and then subjected to a fifth discharge, a fourth charge, and a sixth discharge. The fifth discharge represents a constant current discharge (0.5C-CC) to 2.0 V at a discharge rate of 0.5C. The fourth charge represents a constant current / constant voltage charge (0.5C-CCCV) to 3.65 V at a charge rate of 0.5C. The sixth discharge represents a constant current discharge (0.5C-CC) to 2.0 V at a discharge rate of 0.5C. This yielded the fifth battery.

[0201] <Method for measuring initial resistance> As shown in the following formula (X5), the relative value of the direct current internal resistance (DCIR) of the second battery of Comparative Example 3-2, Example 3-1, or Example 3-2 to the direct current internal resistance (DCIR) of the second battery of Comparative Example 3-1 was defined as the "initial resistance [%]" (see Table 3).

[0202] Initial resistance [relative value; %] = (DC resistance of second battery [Ω] / DC resistance of second battery of Comparative Example 3-1 [Ω]) × 100 (X5)

[0203] In the second evaluation test, the DC resistance of the second battery was measured by the following method. That is, when the second battery was subjected to the above-mentioned second DC resistance evaluation process, the DC resistance (Ω) of the second battery was calculated based on each voltage drop due to "CC10s discharge" at each discharge rate of 0.5C to 1.5C (= voltage before the start of discharge - voltage 10 seconds after the start of discharge) and each current value (i.e., each current value corresponding to the discharge rate of 0.5C to 1.5C).

[0204] <Method for measuring resistance after high temperature storage> As shown in the following formula (X6), the relative value of the DC resistance of the fifth battery of Comparative Example 3-2, Example 3-1, or Example 3-2 to the DC resistance of the fifth battery of Comparative Example 3-1 was defined as the "resistance after high-temperature storage [%]" (see Table 3).

[0205] Resistance after high-temperature storage [relative value; %] = (DC resistance of the fifth battery [Ω] / DC resistance of the fifth battery of Comparative Example 3-1 [Ω]) × 100 (X6)

[0206] In the second evaluation test, the DC resistance of the fifth battery was measured by the following method. That is, the fifth battery was subjected to a DC resistance evaluation process similar to the second DC resistance evaluation process described above. The DC resistance (Ω) of the fifth battery was calculated based on the voltage drop (= voltage before the start of discharge - voltage 10 seconds after the start of discharge) due to "CC 10s discharge" at discharge rates of 0.5C to 1.5C and the current values ​​(i.e., current values ​​corresponding to discharge rates of 0.5C to 1.5C).

[0207] <Method for measuring initial capacity> As shown in the following formula (X7), the relative value of the initial capacity of the first battery of Comparative Example 3-2, Example 3-1, or Example 3-2 to the initial capacity of the first battery of Comparative Example 3-1 was defined as "initial capacity [%]" (see Table 3).

[0208] Initial capacity [relative value; %] = (initial capacity [mAh / g] of first battery / initial capacity [mAh / g] of first battery of Comparative Example 3-1) × 100 (X7)

[0209] In the second evaluation test, the initial capacity of the first battery indicates the capacity obtained when the fourth discharge was performed in the second initial charge-discharge treatment described above.

[0210] <Method for measuring capacity after high-temperature storage> As shown in the following formula (X8), the relative value of the post-high-temperature storage capacity of the fourth battery of Comparative Example 3-2, Example 3-1, or Example 3-2 to the post-high-temperature storage capacity of the fourth battery of Comparative Example 3-1 was defined as "post-high-temperature storage capacity [%]" (see Table 3).

[0211] Capacity after high-temperature storage [relative value; %] = (Capacity after high-temperature storage of the fourth battery [mAh / g] / Capacity after high-temperature storage of the fourth battery of Comparative Example 3-1 [mAh / g]) × 100 (X8)

[0212] In the second evaluation test, the post-high-temperature storage capacity of the fourth battery indicates the capacity obtained when the battery was subjected to the sixth discharge in the second final charge-discharge treatment described above.

[0213] [Table 1]

[0214] [Table 2]

[0215] [Table 3]

[0216] In Tables 1 to 3, "content of each additive" indicates the content [mass %] of each additive relative to the total amount of the non-aqueous electrolyte. In Table 1, "-" means that the corresponding component is not contained. In Tables 1 and 2, "NCM523" means Li(Ni 0.5 Co 0.2 Mn 0.3 In Table 3, "LFP" refers to LiFePO4.

[0217] The nonaqueous electrolyte of Comparative Example 1-2 contained a fluorinated lithium sulfonate compound (I) and a cyclic sulfone compound (C-1), but did not contain a cyclic sulfone compound (II). Therefore, the electrochemical device of Comparative Example 1-2 had an initial resistance of 108% and a resistance after high-temperature storage of 95% compared to the electrochemical device of Comparative Example 1-1. This indicates that the initial resistance of the electrochemical device of Comparative Example 1-2 was not suppressed. In other words, it was found that the nonaqueous electrolyte of Comparative Example 1-2 was unable to suppress the initial resistance of the electrochemical device. In contrast, the nonaqueous electrolyte solutions of Examples 1-1 and 1-2 contain a fluorinated lithium sulfonate compound (I) and a cyclic sulfone compound (II). Therefore, the electrochemical devices of Examples 1-1 and 1-2 had initial resistances of 99% or less and resistances after high-temperature storage of 98% or less compared to the electrochemical device of Comparative Example 1-1. Therefore, it was found that the electrochemical devices of Examples 1-1 and 1-2 had reduced initial resistances and suppressed an increase in DC resistance even when stored for long periods in a high-temperature environment. In other words, it was found that the nonaqueous electrolyte solutions of Examples 1-1 and 1-2 suppressed the initial resistance of the electrochemical device and could suppress an increase in DC resistance even when the electrochemical device was stored for long periods in a high-temperature environment. Furthermore, by comparing Example 1-1 and Example 1-2, it is clear that R 21 and R 22 It has been found that when at least one of the groups is a group represented by formula (ii-1), the initial resistance of the electrochemical device can be further reduced and the decrease in capacity after high-temperature storage can be effectively suppressed.

[0218] The nonaqueous electrolyte solutions of Examples 2-1 to 2-4 contain a fluorinated lithium sulfonate compound (I) and a cyclic sulfone compound (II). Therefore, the electrochemical devices of Examples 2-1 to 2-4 had initial resistances of 94% or less and resistances after high-temperature storage of 87% or less compared to the electrochemical device of Comparative Example 2-1. Therefore, it was found that the electrochemical devices of Examples 2-1 to 2-4 had reduced initial resistances and suppressed an increase in DC resistance even when stored for long periods in a high-temperature environment. In other words, it was found that the nonaqueous electrolyte solutions of Examples 2-1 to 2-4 suppress the initial resistance of the electrochemical devices and can suppress an increase in DC resistance even when the electrochemical devices are stored for long periods in a high-temperature environment. Furthermore, the electrochemical devices of Examples 2-1 to 2-4 had initial capacities of 101% or more and capacities after high-temperature storage of 102% or more compared to the electrochemical device of Comparative Example 2-1. Therefore, it was found that the electrochemical devices of Examples 2-1 to 2-4 had high initial capacities and were less likely to lose capacity even when stored in a high-temperature environment for a long period of time. Comparing Example 2-3 with Examples 2-1, 2-2, and 2-4, the electrochemical device of Example 2-3 had a resistance after high-temperature storage of 81%, the lowest among Examples 2-1 to 2-4, and a capacity after high-temperature storage of 104%, the highest among Examples 2-1 to 2-4. This shows that by including a lithium fluorophosphate compound (VI) in the nonaqueous electrolyte in addition to the fluorinated lithium sulfonate compound (I) and the cyclic sulfone compound (II), it is possible to further suppress a decrease in capacity and an increase in DC resistance of the electrochemical device even during charge-discharge cycles after storage in a high-temperature environment. Comparing Example 2-4 with Example 2-1, the electrochemical device of Example 2-4 had a resistance after high-temperature storage of 86%, which was lower than that of Example 2-1, and a capacity after high-temperature storage of 103%, which was higher than that of Example 2-1. This shows that by including a cyclic carbonate ester compound (III) in the nonaqueous electrolyte in addition to the fluorinated lithium sulfonate compound (I) and the cyclic sulfone compound (II), it is possible to further suppress a decrease in capacity and an increase in DC resistance of the electrochemical device even during charge-discharge cycles after storage in a high-temperature environment.

[0219] The nonaqueous electrolyte of Comparative Example 3-2 contained a fluorinated lithium sulfonate compound (I) and a cyclic sulfone compound (C-1), but did not contain a cyclic sulfone compound (II). Therefore, the electrochemical device of Comparative Example 3-2 had an initial resistance of 121% and a resistance after high-temperature storage of 97% compared to the electrochemical device of Comparative Example 3-1. This indicates that the initial resistance of the electrochemical device of Comparative Example 3-2 was not suppressed. In other words, it was found that the nonaqueous electrolyte of Comparative Example 3-2 was unable to suppress the initial resistance of the electrochemical device. In contrast, the nonaqueous electrolyte solutions of Examples 3-1 and 3-2 contain a fluorinated lithium sulfonate compound (I) and a cyclic sulfone compound (II). Therefore, the electrochemical devices of Examples 3-1 and 3-2 had initial resistances of 98% or less and resistances after high-temperature storage of 94% or less compared to the electrochemical device of Comparative Example 3-1. Therefore, it was found that the electrochemical devices of Examples 3-1 and 3-2 had reduced initial resistances and suppressed an increase in DC resistance even when stored for long periods in a high-temperature environment. In other words, it was found that the nonaqueous electrolyte solutions of Examples 3-1 and 3-2 suppressed the initial resistance of the electrochemical device and could suppress an increase in DC resistance even when the electrochemical device was stored for long periods in a high-temperature environment. Furthermore, by comparing Example 3-1 and Example 3-2, it is clear that R 21 and R 22It has been found that when at least one of the groups is a group represented by formula (ii-1), the initial resistance of the electrochemical device can be further reduced and the decrease in capacity after high-temperature storage can be effectively suppressed. [Explanation of symbols]

[0220] 1. Electrochemical device precursors 10 Battery element 11 Positive electrode 11A positive electrode current collector 11B Positive electrode composite layer 12 Negative electrode 12A negative electrode current collector 12B Negative electrode composite layer 13 Separator 14 Cell layer 21 Positive lead 22 Negative lead 30 Exterior body

Claims

1. a fluorinated lithium sulfonate compound (I); Compound (II) represented by the following formula (II): A nonaqueous electrolyte for an electrochemical device comprising: the content of the fluorinated lithium sulfonate compound (I) is 0.01% by mass or more and 10.0% by mass or less with respect to the total amount of the non-aqueous electrolyte solution for electrochemical devices, The non-aqueous electrolyte solution for electrochemical devices has a content of the compound (II) of 0.1 mass % or more and 10.0 mass % or less relative to the total amount of the non-aqueous electrolyte solution for electrochemical devices. 【Chemistry 1】 [In formula (II), R ２１ is a hydrogen atom, and R ２２ is a group represented by the following formula (ii-1): 【Chemistry 2】

2. 2. The nonaqueous electrolyte solution for electrochemical devices according to claim 1, further comprising a cyclic carbonate compound (III) containing a carbon-carbon unsaturated bond.

3. 3. The nonaqueous electrolyte solution for electrochemical devices according to claim 1, further comprising a compound (IV) represented by the following formula (IV): 【Transformation 3】 [In formula (IV), R ４１ and R ４２ each independently represents a fluorine atom, a trifluoromethyl group, or a pentafluoroethyl group.

4. The nonaqueous electrolyte solution for electrochemical devices according to any one of claims 1 to 3, further comprising a compound (V) represented by the following formula (V): 【Chemistry 4】 [In formula (V), M is an alkali metal; b is an integer from 1 to 3, m is an integer from 1 to 4, n is an integer from 0 to 8, q is 0 or 1; R ５１ represents 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 groups may contain a substituent or a heteroatom in the structure, and when q is 1 and m is 2 to 4, m R ５１ may be bonded to each other; R ５２ is a halogen atom, 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 (these groups may contain a substituent or a heteroatom in the structure, and when n is 2 to 8, n R ５２ may be bonded to each other to form a ring; Q １ , and Q ２ are each independently an oxygen atom or a carbon atom.

5. 5. The nonaqueous electrolyte solution for electrochemical devices according to claim 1, further comprising compound (VI) which is at least one selected from the group consisting of lithium monofluorophosphate and lithium difluorophosphate.

6. Case and a positive electrode, a negative electrode, a separator, and an electrolyte solution housed in the case; Equipped with the positive electrode is a positive electrode capable of absorbing and desorbing lithium ions, the negative electrode is capable of absorbing and desorbing lithium ions, An electrochemical device precursor, wherein the electrolytic solution is the nonaqueous electrolytic solution for electrochemical devices according to any one of claims 1 to 5.

7. 7. The electrochemical device precursor according to claim 6, wherein the positive electrode contains, as a positive electrode active material, a lithium-containing composite oxide represented by the following formula (X): LiNi ａ Co ｂ Mn ｃ O ２ … Equation (X) [In formula (X), a, b, and c each independently represent a number greater than 0 and less than 1.00, and the sum of a, b, and c represents a number greater than or equal to 0.99 and less than or equal to 1.00.]

8. The electrochemical device precursor according to claim 6 , wherein the positive electrode comprises lithium iron phosphate as a positive electrode active material.

9. A step of preparing an electrochemical device precursor according to any one of claims 6 to 8; charging and discharging the electrochemical device precursor; A method for manufacturing an electrochemical device, comprising:

Images