Non-aqueous electrolyte solution

Abstract

The non-aqueous electrolyte solution according to the present disclosure is for a secondary battery comprising a negative electrode. The negative electrode comprises a current collector and a negative-electrode mixture layer formed on the current collector. The negative-electrode mixture layer contains a negative-electrode active material. The negative-electrode mixture layer satisfies (a) or (b) below. The content of the binder is 0.5 mass% or less in relation to the total amount of the negative-electrode mixture layer. The non-aqueous electrolyte solution contains an additive. The total content of the additive is 2.0 mass% or more in relation to the total amount of the non-aqueous electrolyte solution.　(a) The negative-electrode mixture layer does not contain a binder, and (b) the negative-electrode mixture layer further contains a binder, and the content of the binder is more than 0 mass% and 0.5 mass% or less in relation to the total amount of the negative-electrode mixture layer.

Description

non-aqueous electrolyte

[0001] This disclosure relates to a non-aqueous electrolyte.

[0002] The performance of energy storage devices (such as small, lightweight, and high-output lithium-ion secondary batteries) has been improving in recent years. With the advancement of energy storage devices, they are now used not only in small electrical appliances but also in large products (such as automobiles). Lithium-ion secondary batteries require various characteristics (such as output characteristics and charge / discharge characteristics) to meet specific requirements. For example, excellent capacity retention after charge / discharge cycles is a very important evaluation criterion for lithium-ion secondary batteries.

[0003] A known method for improving the capacity retention rate of lithium-ion secondary batteries after charge-discharge cycles is to incorporate various additives into the non-aqueous electrolyte. Patent Document 1 discloses that the capacity retention rate after charge-discharge cycles may decrease depending on the combination of graphite and additives in the electrolyte.

[0004] Patent Document 1: Patent No. 7484725

[0005] By reducing the amount of binder in the negative electrode (i.e., the amount of binder in the negative electrode composite layer), various properties of a non-aqueous electrolyte secondary battery can be improved. In this disclosure, "non-aqueous electrolyte secondary battery" refers to a lithium-ion secondary battery containing a non-aqueous electrolyte. On the other hand, when the amount of binder is reduced (i.e., the binder content relative to the total amount of the negative electrode composite layer is 0% by mass or greater than 0% by mass and less than or equal to 0.5% by mass), the contact area between the negative electrode active material and the non-aqueous electrolyte increases significantly. Therefore, a larger amount of additives contained in the non-aqueous electrolyte is required. As a result, it tends to be difficult to obtain sufficient charge-discharge characteristics with conventional amounts.

[0006] An object of one aspect of this disclosure is to provide a non-aqueous electrolyte that can improve the capacity retention rate after high-temperature charge-discharge cycle testing in a non-aqueous electrolyte secondary battery equipped with a negative electrode having a low binder content.

[0007] The means for solving the above problems include the following embodiments. <1-1> A non-aqueous electrolyte for a secondary battery having a negative electrode, wherein the negative electrode comprises a current collector and a negative electrode composite layer formed on the current collector, the negative electrode composite layer contains a negative electrode active material, the negative electrode composite layer satisfies either (a) or (b) below, the non-aqueous electrolyte contains an additive, and the total content of the additive is 2.0% by mass or more with respect to the total amount of the non-aqueous electrolyte. (a) The negative electrode composite layer does not contain a binder. (b) The negative electrode composite layer further contains a binder, and the amount of the binder is greater than 0% by mass and less than or equal to 0.5% by mass with respect to the total amount of the negative electrode composite layer. <1-2> The non-aqueous electrolyte according to <1-1>, wherein the additive contains at least one selected from the group consisting of a compound represented by the following formula (I-1), a compound represented by the following formula (I-2), a compound represented by the following formula (II), a compound represented by the following formula (III), a compound represented by the following formula (IV), a compound represented by the following formula (V), a compound represented by the following formula (VI), a compound represented by the following formula (VII), a compound represented by the following formula (VIII), a compound represented by the following formula (IX-1), a compound represented by the following formula (IX-1), a compound represented by the following formula (X), and a compound represented by the following formula (XI).

[0008]

[0009]

[0010]

[0011]

[0012] (In formula (I-1), M ＋ represents an alkali metal ion, ammonium ion, imidazolium ion, pyridinium ion, pyrrolidinium ion, piperidinium ion, or phosphonium ion. In formula (I-2), two M ＋each independently represent an alkali metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion. In formula (II), Q represents a boron atom (B) or a phosphorus atom (P). R ２１ each independently represent a single bond (-), or a divalent hydrocarbon group having 1 to 6 carbon atoms which may optionally contain at least one functional group selected from the group consisting of a halogeno group and an oxa group (-O-) as a substituent. Each X independently represents a halogeno group. When Q is a boron atom (B), a represents 1 or 2, b represents 2 when a is 1, and b represents 0 when a is 2. When Q is a phosphorus atom (P), a represents an integer of 1 to 3, b represents 4 when a is 1, b represents 2 when a is 2, and b represents 0 when a is 3. c represents an integer of 1 to 3. M ＋ each independently represent an alkali metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion. In formula (III), two R ３１ each independently represent a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may optionally contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms which contains a fluoro group (-F) as a substituent. M ＋ represents an alkali metal ion, an alkaline earth metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion. In formula (IV), R ４１ represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may optionally contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms which contains a fluoro group (-F) as a substituent. R ４２ represents a hydrocarbon group having 1 to 12 carbon atoms which may optionally contain at least one functional group selected from the group consisting of a fluoro group (-F) and an oxa group (-O-) as a substituent, or a fluorocarbon group having 1 to 12 carbon atoms which may optionally contain an oxa group (-O-) as a substituent. M ＋R represents an alkali metal ion, alkaline earth metal ion, ammonium ion, imidazolium ion, pyridinium ion, pyrrolidinium ion, piperidinium ion, or phosphonium ion. In formula (V), R ５１ This represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain a fluoro group (-F) or an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which contains a fluoro group (-F) as a substituent. ＋ R represents an alkali metal ion, alkaline earth metal ion, ammonium ion, imidazolium ion, pyridinium ion, pyrrolidinium ion, piperidinium ion, or phosphonium ion. In formula (VI), R ６１ Each of these independently represents a fluoro group (-F), a fluorine carbide group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms which contains a fluoro group (-F) as a substituent. i represents an integer from 1 to 4. In formula (VII), R ７１ Each independently represents a fluoro group (-F), a fluorine carbide group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of a fluoro group and an oxa group (-O-). j represents an integer from 0 to 2. In formula (VIII), the double line (solid and dotted) represents a single bond (-) or a double bond (=). R ８１ Each independently represents a fluoro group (-F), a fluorine carbide group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of a fluoro group and an oxa group (-O-). k represents an integer from 0 to 4. In formula (IX-1), R ９１ and R ９２ These can be independently substituted with a halogen group, an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ R represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain at least one functional group selected from the group consisting of ).９１ The substituents are a halogen group, an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ Represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain at least one functional group selected from the group consisting of ). ９３ These can be independently substituted with a halogen group, a cyano group (-CN), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ This represents a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of ). In formula (X), R １０１ is a methylene group (-CH ２ -), ethylene group (-CH ２ CH ２ -), or n-propylene group (-CH ２ CH ２ CH ２ Represents (-). １０２ Each of these independently represents a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (x-3), a group represented by formula (x-4), a group represented by formula (x-5), a group represented by formula (x-6), a group represented by formula (x-7), or a group represented by formula (x-8), which may each contain at least one functional group selected from the group consisting of a halogen group (-X) and an oxa group (-O-) as a substituent. １０１ is a methylene group (-CH ２ When -, m represents an integer between 0 and 2. １０１ is an ethylene group (-CH ２ CH ２ When -, m represents an integer from 0 to 4. １０１ is an n-propylene group (-CH ２ CH ２ CH ２ When -, m represents an integer from 0 to 6. In equation (XI), the two R １１１ Each of these independently represents a hydrocarbon group having 1 to 12 carbon atoms or a trialkylsilyl group having 3 to 18 carbon atoms.) <1-3> The negative electrode active material has a median diameter (D ５０A non-aqueous electrolyte according to <1-1> or <1-2>, wherein the negative electrode composite layer contains graphite particles of 10 μm or less. <1-4> A non-aqueous electrolyte according to any one of <1-1> to <1-3>, wherein the negative electrode composite layer contains a conductive additive, and the conductive additive contains carbon nanotubes. <1-5> A non-aqueous electrolyte according to <1-4>, wherein the conductive additive consists of carbon nanotubes, and the content of the carbon nanotubes is 0.5% by mass or less with respect to the total amount of the negative electrode composite layer. <1-6> A non-aqueous electrolyte according to any one of <1-1> to <1-4>, wherein the negative electrode composite layer contains a conductive additive different from carbon nanotubes, and the content of the conductive additive is 0.5% by mass or less with respect to the total amount of the negative electrode composite layer.

[0013] The means for solving the above problems include the following embodiments: <2-1> A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, wherein the negative electrode comprises a current collector and a negative electrode composite layer formed on the current collector, the negative electrode composite layer comprises a negative electrode active material, the negative electrode composite layer satisfies either (a) or (b) below, the non-aqueous electrolyte comprises an additive, and the total content of the additive is 2.0% by mass or more with respect to the total amount of the non-aqueous electrolyte. (a) The negative electrode composite layer does not contain a binder. (b) The negative electrode composite layer further contains a binder, and the amount of the binder is greater than 0% by mass and less than or equal to 0.5% by mass with respect to the total amount of the negative electrode composite layer. <2-2> The non-aqueous electrolyte secondary battery according to <2-1>, wherein the additive contains at least one selected from the group consisting of a compound represented by the following formula (I-1), a compound represented by the following formula (I-2), a compound represented by the following formula (II), a compound represented by the following formula (III), a compound represented by the following formula (IV), a compound represented by the following formula (V), a compound represented by the following formula (VI), a compound represented by the following formula (VII), a compound represented by the following formula (VIII), a compound represented by the following formula (IX-1), a compound represented by the following formula (IX-2), a compound represented by the following formula (X), and a compound represented by the following formula (XI).

[0014]

[0015]

[0016]

[0017]

[0018] (In formula (I-1), M ＋ represents an alkali metal ion, ammonium ion, imidazolium ion, pyridinium ion, pyrrolidinium ion, piperidinium ion, or phosphonium ion. In formula (I-2), two M ＋ Each of these independently represents an alkali metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion. In formula (II), Q represents a boron atom (B) or a phosphorus atom (P). ２１ Each independently represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain a single bond (-) or at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent. Each independently represents a halogen group. When Q is a boron atom (B), a represents 1 or 2, when a is 1, b represents 2, and when a is 2, b represents 0. When Q is a phosphorus atom (P), a represents an integer from 1 to 3, when a is 1, b represents 4, when a is 2, b represents 2, and when a is 3, b represents 0. c represents an integer from 1 to 3. In formula (III), the two R ３１ Each of these independently represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain a fluoro group (-F), an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which contains a fluoro group (-F) as a substituent. ＋ R represents an alkali metal ion, alkaline earth metal ion, ammonium ion, imidazolium ion, pyridinium ion, pyrrolidinium ion, piperidinium ion, or phosphonium ion. In formula (IV), R ４１ R represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain a fluoro group (-F) or an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which contains a fluoro group (-F) as a substituent.４２ This represents a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of a fluoro group (-F) and an oxa group (-O-) as a substituent, or a fluorine carbide group having 1 to 12 carbon atoms, which may contain an oxa group (-O-) as a substituent. ＋ R represents an alkali metal ion, alkaline earth metal ion, ammonium ion, imidazolium ion, pyridinium ion, pyrrolidinium ion, piperidinium ion, or phosphonium ion. In formula (V), R ５１ This represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain a fluoro group (-F) or an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which contains a fluoro group (-F) as a substituent. ＋ R represents an alkali metal ion, alkaline earth metal ion, ammonium ion, imidazolium ion, pyridinium ion, pyrrolidinium ion, piperidinium ion, or phosphonium ion. In formula (VI), R ６１ Each of these independently represents a fluoro group (-F), a fluorine carbide group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms which contains a fluoro group (-F) as a substituent. i represents an integer from 1 to 4. In formula (VII), R ７１ Each independently represents a fluoro group (-F), a fluorine carbide group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of a fluoro group and an oxa group (-O-). j represents an integer from 0 to 2. In formula (VIII), the double line (solid and dotted) represents a single bond (-) or a double bond (=). R ８１ Each independently represents a fluoro group (-F), a fluorine carbide group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of a fluoro group and an oxa group (-O-). k represents an integer from 0 to 4. In formula (IX-1), R ９１ and R ９２These can be independently substituted with a halogen group, an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ R represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain at least one functional group selected from the group consisting of ). ９１ The substituents are a halogen group, an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ Represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain at least one functional group selected from the group consisting of ). ９３ These can be independently substituted with a halogen group, a cyano group (-CN), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ This represents a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of ). In formula (X), R １０１ is a methylene group (-CH ２ -), ethylene group (-CH ２ CH ２ -), or n-propylene group (-CH ２ CH ２ CH ２ Represents (-). １０２ Each of these independently represents a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (x-3), a group represented by formula (x-4), a group represented by formula (x-5), a group represented by formula (x-6), a group represented by formula (x-7), or a group represented by formula (x-8), which may each contain at least one functional group selected from the group consisting of a halogen group (-X) and an oxa group (-O-) as a substituent. １０１ is a methylene group (-CH ２ When -, m represents an integer between 0 and 2. １０１ is an ethylene group (-CH ２ CH ２ When -, m represents an integer from 0 to 4. １０１ is an n-propylene group (-CH ２ CH ２ CH ２ When -, m represents an integer from 0 to 6. In equation (XI), the two R １１１Each of these independently represents a hydrocarbon group having 1 to 12 carbon atoms or a trialkylsilyl group having 3 to 18 carbon atoms.) <2-3> The negative electrode active material has a median diameter (D ５０ ) comprising graphite particles of 10 μm or less, as described in <2-1> or <2-2>. <2-4> A non-aqueous electrolyte secondary battery according to any one of <2-1> to <2-3>, wherein the negative electrode composite layer comprises a conductive additive, and the conductive additive comprises carbon nanotubes. <2-5> A non-aqueous electrolyte secondary battery according to any one of <2-1> to <2-4>, wherein the negative electrode composite layer comprises a conductive additive different from carbon nanotubes, and the content of the conductive additive is 0.5% by mass or less with respect to the total amount of the negative electrode composite layer.

[0019] According to one aspect of this disclosure, a non-aqueous electrolyte secondary battery having a negative electrode with a low binder content is provided that can improve the capacity retention rate after a high-temperature charge-discharge cycle test.

[0020] Figure 1 is a cross-sectional view showing a stacked non-aqueous electrolyte secondary battery, which is an example of a non-aqueous electrolyte secondary battery of the present disclosure. Figure 2 is a cross-sectional view showing a coin-type non-aqueous electrolyte secondary battery, which is another example of a non-aqueous electrolyte secondary battery of the present disclosure.

[0021] In explaining this disclosure, specific examples will be given, but the content is not limited to the following, and may be modified as appropriate, as long as it does not deviate from the intent of this disclosure.

[0022] In the present disclosure, a numerical range expressed using "~" means a range including the numerical values described before and after "~" as the lower limit and the upper limit. In the numerical ranges described stepwise in the present disclosure, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of the numerical range described in another stepwise description. In the numerical ranges described in the present disclosure, the upper limit or lower limit of the numerical range may be replaced with the values shown in the examples. In the present disclosure, when there are a plurality of substances corresponding to each component in the composition, the amount of each component means the total amount of the plurality of substances present in the composition unless otherwise specified. In the present disclosure, combinations of preferred embodiments are more preferred embodiments. In the present disclosure, the term "process" includes not only an independent process, but also a case that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0023] (1) Nonaqueous Electrolyte A nonaqueous electrolyte according to one embodiment of the present disclosure (hereinafter may be simply abbreviated as "nonaqueous electrolyte") is a nonaqueous electrolyte for a nonaqueous electrolyte secondary battery including a negative electrode (hereinafter also referred to as "specific negative electrode"). The negative electrode (that is, the specific negative electrode) includes a current collector and a negative electrode mixture layer formed on the current collector. The negative electrode mixture layer contains a negative electrode active material. The negative electrode mixture layer satisfies the following (a) or (b). The nonaqueous electrolyte contains an additive. The content of the additive is 2.0% by mass or more based on the total amount of the nonaqueous electrolyte. (a) The negative electrode mixture layer does not contain a binder (that is, the content of the binder is 0% by mass relative to the total amount of the negative electrode mixture layer) (b) The negative electrode mixture layer further contains a binder, and the content of the binder is more than 0% by mass and 0.5% by mass or less relative to the total amount of the negative electrode mixture layer

[0024] The negative electrode of a non-aqueous electrolyte secondary battery is usually obtained by applying a slurry to a current collector, drying it, and compressing it to form a negative electrode composite layer on the current collector. The slurry usually contains a negative electrode active material, a binder, and a solvent, and optionally further contains a conductive additive and a thickener dispersed in the solvent. In order to ensure the moldability of the negative electrode composite layer, the amount of binder is generally higher than 0.5% by mass relative to the total amount of solids in the slurry. The disclosers have shown that various properties of a non-aqueous electrolyte secondary battery can be improved by not incorporating a binder into the negative electrode composite layer, or by reducing the amount of binder compared to conventional methods. On the other hand, when no binder is incorporated into the negative electrode composite layer, or when the amount of binder is reduced (i.e., when the binder content relative to the total amount of the negative electrode composite layer is 0% by mass or more than 0% by mass and 0.5% by mass or less), the contact area between the negative electrode active material and the non-aqueous electrolyte increases. Therefore, a larger amount of additives is required in the non-aqueous electrolyte. As a result, the present disclosers have revealed that it tends to be difficult to obtain sufficient charge-discharge characteristics with conventional additive amounts. The present disclosers have found that by increasing the total content of additives to 2.0% by mass or more, the charge-discharge characteristics (especially the capacity retention rate after high-temperature charge-discharge cycle testing) can be improved. The following provides a detailed explanation of "additives," "binding agents," etc.

[0025] (1.1) Additives The non-aqueous electrolyte contains additives. The total amount of additives is 2.0% by mass or more relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered as 100% by mass). The total amount of additives may be 2.20% by mass or more, 2.40% by mass or more, 2.60% by mass or more, 2.80% by mass or more, or 2.95% by mass or more. The total amount of additives may be 60.00% by mass or less, 30.00% by mass or less, 20.00% by mass or less, 10.00% by mass or less, 5.00% by mass or less, 3.50% by mass or less, 2.95% by mass or less, or 2.50% by mass or less. When the total amount of additives is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0026] The number of types of additives in the non-aqueous electrolyte solution is usually 1 or more, preferably 2 or more, and more preferably 3 or more. The number of types of additives is usually 10 or less, preferably 8 or less, and more preferably 6 or less. When the number of types of additives is within the above range, it becomes easier to improve various characteristics of a non-aqueous electrolyte secondary battery.

[0027] The type of additive in the non-aqueous electrolyte solution is not particularly limited, and known additives can be appropriately selected. Examples of the additives include a compound represented by the following formula (I-1) (hereinafter also referred to as "compound (I-1)"), a compound represented by the following formula (I-2) (hereinafter also referred to as "compound (I-2)"), a compound represented by the following formula (II) (hereinafter also referred to as "compound (II)"), a compound represented by the following formula (III) (hereinafter also referred to as "compound (III)"), a compound represented by the following formula (IV) (hereinafter also referred to as "compound (IV)"), a compound represented by the following formula (V) (hereinafter also referred to as "compound (V)"), a compound represented by the following formula (VI) (hereinafter also referred to as "compound (VI)"), a compound represented by the following formula (VII), a compound represented by the following formula (VIII) (hereinafter also referred to as "compound (VII)"), a compound represented by the following formula (IX-1) (hereinafter also referred to as "compound (IX-1)"), a compound represented by the following (IX-2) (hereinafter also referred to as "compound (IX-2)"), a compound represented by the following formula (X) (hereinafter also referred to as "compound (X)"), and a compound represented by the following formula (XI) (hereinafter also referred to as "compound (XI)"). The non-aqueous electrolyte solution may contain two or more types of additives.

[0028] It is preferable that the additive includes at least one selected from the group consisting of compound (I-1), compound (I-2), compound (II), compound (III), compound (IV), compound (V), compound (VI), compound (VII), compound (IX-1), compound (IX-2), compound (X), and compound (XI). This allows a favorable coating film to be formed on the surface of the active material, and improves the capacity retention rate after a high-temperature charge-discharge cycle test.

[0029] Hereinafter, compound (I-1) to compound (XI) will be described in detail.

[0030]

[0031]

[0032]

[0033] (1.1.1) Compound (I-1) and Compound (I-2) Compound (I-1) is represented by the following formula (I-1). Compound (I-2) is represented by the following formula (I-2).

[0034]

[0035] In formula (I-1), M ＋ This represents alkali metal ions, ammonium ions, imidazolium ions, pyridinium ions, pyrrolidinium ions, piperidinium ions, or phosphonium ions.

[0036] In equation (I-2), two M ＋ Each of these independently represents an alkali metal ion, ammonium ion, imidazolium ion, pyridinium ion, pyrrolidinium ion, piperidinium ion, or phosphonium ion.

[0037] Compounds (I-1) and (I-2) may also act as electrolytes as described later. In this disclosure, regardless of their function, compounds (I-1) and (I-2) contained in a non-aqueous electrolyte are considered "additives".

[0038] M ＋ Examples of alkali metal ions include lithium ions (Li ＋ ), sodium ions (Na ＋ ), and potassium ions (K ＋ ) are some examples. M ＋ Examples of "ammonium ions" represented by the following formula (m1) include the ion represented by M. ＋ An example of an "imidazolium ion" represented by the following formula (m²) is the ion represented by M. ＋ Examples of "pyridinium ions" represented by the formula (m³) below include the ion represented by the following formula: M ＋Examples of the "pyrrolidinium ion" represented by include ions represented by the following formula (m4). M ＋ Examples of the "piperidinium ion" represented by include ions represented by the following formula (m5). M ＋ Examples of the "phosphonium ion" represented by include ions represented by the following formula (m6).

[0039]

[0040] In formulas (m1) to (m6), each R' is independently a hydrogen atom (-H), or a halogeno group, an oxa group (-O-), a carbonyl group (>C=O), a sulfonyl group (>S(=O) ２ ), a secondary amino group (-NH-), and a tertiary amino group (-N<), represents a hydrocarbon group having 1 to 20 carbon atoms which may contain at least one functional group selected from the group consisting of. M ＋ is preferably a lithium ion (Li ＋ ).

[0041] Examples of the compound (I-1) include lithium difluorophosphate (LiPO ２ F ２ ) represented by the following formula (I-1-1). Examples of the compound (I-2) include lithium monofluorophosphate (Li ２ PO ３ F) represented by the following formula (I-2-1). The non-aqueous electrolyte may contain two or more types of compound (I-1), or may contain two or more types of compound (I-2).

[0042]

[0043] The content of compound (I-1) and compound (I-2) is not particularly limited and may be 0% to 10% by mass relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered to be 100% by mass). The content of compound (I-1) and compound (I-2) may be 0.01% by mass or more, 0.10% by mass or more, 0.30% by mass or more, 0.60% by mass or more, 0.90% by mass or more, or 1.10% by mass or more. The content of compound (I-1) and compound (I-2) may be 5.00% by mass or less, 4.00% by mass or less, 3.00% by mass or less, 2.00% by mass or less, 1.30% by mass or less, 1.10% by mass or less, or 0.80% by mass or less. When the content of compound (I-1) and compound (I-2) is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0044] (1.1.2) Compound (II) Compound (II) is represented by the following formula (II).

[0045]

[0046] In formula (II), Q represents a boron atom (B) or a phosphorus atom (P). ２１ Each independently represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain a single bond (-) or at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent. Each independently represents a halogen group. When Q is a boron atom (B), a represents 1 or 2, when a is 1, b represents 2, and when a is 2, b represents 0. When Q is a phosphorus atom (P), a represents an integer from 1 to 3, when a is 1, b represents 4, when a is 2, b represents 2, and when a is 3, b represents 0. c represents an integer from 1 to 3. M ＋ Each of these independently represents an alkali metal ion, ammonium ion, imidazolium ion, pyridinium ion, pyrrolidinium ion, piperidinium ion, or phosphonium ion.

[0047] Compound (II) may also act as an electrolyte, as described later. In this disclosure, regardless of its function, compound (II) contained in a non-aqueous electrolyte is considered an "additive".

[0048] When Q is a boron atom, compound (II) is a borate. When Q is a phosphorus atom, compound (II) is a phosphate.

[0049] R ２１ The "single bond (-)" represented by R ２１ This means that the carbon atoms of the carbonyl groups (C=O) at both ends are directly bonded together, forming an oxalate ligand (oxalate ion ligand). ２１ The term "divalent hydrocarbon group" as represented by R refers to a hydrocarbon group with two bond positions. ２１ The “divalent hydrocarbon group” represented by may be a linear aliphatic hydrocarbon group, or a hydrocarbon group having at least one structure selected from the group consisting of branched structures, cyclic structures, and carbon-carbon unsaturated bond structures (e.g., carbon-carbon double bond structures and carbon-carbon triple bond structures). The number of these structures is also not limited. (Acyclic) aliphatic hydrocarbon groups, monocyclic aliphatic hydrocarbon groups, polycyclic aliphatic hydrocarbon groups, monocyclic aromatic hydrocarbon groups, and polycyclic aromatic hydrocarbon groups are included in “hydrocarbon groups”. Alkylene groups, alkenylene groups, alkynylene groups, and arylene groups, etc., are also included in “divalent hydrocarbon groups”. ２１ The expression "a divalent hydrocarbon group having 1 to 6 carbon atoms which may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent" means that the hydrogen atoms of the divalent hydrocarbon group may be substituted with a halogen group (for example, a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and an iodine group (-I), etc.), the carbon atoms of the divalent hydrocarbon group may be substituted with an oxa group (-O-), and the hydrogen atoms of the divalent hydrocarbon group may be substituted with a halogen group and the carbon atoms of the divalent hydrocarbon group may be substituted with an oxa group (-O-).

[0050] R ２１ The number of carbon atoms in the hydrocarbon group represented is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and particularly preferably 2 or less.

[0051] R ２１Examples include a single bond (-), a methylene group (-CH ２ -), an ethylene group (-CH ２ CH ２ -), and an n-propylene group (-CH ２ CH ２ CH ２ -), etc. Among these, a single bond (-) is preferred.

[0052] Examples of the "halogeno group" represented by X include a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and iodo (-I), etc. Among these, a fluoro group (-F) is preferred.

[0053] When Q is a boron atom (B), it is preferable that a is 2, b is 0, and c is 1.

[0054] When Q is a phosphorus atom (P), it is preferable that a is 1, b is 4, and c is 1.

[0055] M in formula (II) ＋ is the same as those exemplified as M in formula (I-1) ＋

[0056] Examples of the compound (II) include lithium bis(oxalato)borate (LiBOB) represented by the following formula (II-1), lithium difluorooxalatoborate (LiDFOB) represented by the following formula (II-2), lithium tetrafluorooxalatophosphate (LiTFOP) represented by the following formula (II-3), and lithium difluorobis(oxalato)phosphate (LiDFBOP) represented by the following formula (II-4), etc. The non-aqueous electrolyte solution may contain two or more types of the compound (II).

[0057]

[0058] ​The content of compound (II) is not particularly limited and may be 0% to 10% by mass relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered to be 100% by mass). The content of compound (II) may be 0.01% or more by mass, 0.1% or more by mass, 0.3% or more by mass, 0.4% or more by mass, 0.6% or more by mass, or 0.9% or more by mass. The content of compound (II) may be 5.0% or less by mass, 4.0% or less by mass, 3.0% or less by mass, 2.0% or less by mass, 1.20% or less by mass, 0.80% or less by mass, or 0.6% or less by mass. When the content of compound (II) is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0059] (1.1.3) Compound (III) Compound (III) is represented by the following formula (III).

[0060]

[0061] In equation (III), the two R ３１ Each of these independently represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain a fluoro group (-F), an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which contains a fluoro group (-F) as a substituent. ＋ This represents alkali metal ions, alkaline earth metal ions, ammonium ions, imidazolium ions, pyridinium ions, pyrrolidinium ions, piperidinium ions, or phosphonium ions.

[0062] Compound (III) may also act as an electrolyte, as described later. In this disclosure, regardless of its function, compound (III) contained in a non-aqueous electrolyte is considered an "additive".

[0063] R ３１The term "fluorinated carbide group" as expressed in this way refers to a group in which all hydrogen atoms of a hydrocarbon group are replaced with fluorine atoms. The concept of "fluorinated carbide group" includes perfluoroalkyl groups. A fluorinated carbide group may be a linear carbide group, or it may be a fluorinated carbide group having at least one structure selected from the group consisting of a branched structure, a cyclic structure, and a carbon-carbon unsaturated bond structure (e.g., a carbon-carbon double bond structure and a carbon-carbon triple bond structure). ３１ The expression "carbon hydrocarbon group having 1 to 12 carbon atoms and containing a fluoro group (-F) as a substituent" means a hydrocarbon group in which one or more hydrogen atoms are replaced by fluorine atoms. The expression "carbon hydrocarbon group having 1 to 12 carbon atoms and possibly containing an oxa group (-O-) as a substituent" means that the carbon atoms of the hydrocarbon group may be replaced by an oxa group (-O-).

[0064] R ３１ The number of carbon atoms in the fluorine carbide group represented by is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. ３１ The number of carbon atoms in the hydrocarbon group represented is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0065] R ３１ Examples include fluoro groups (-F) and trifluoromethyl groups (-CF) ３ ), pentafluoroethyl group (-C ２ F ５ ), n-heptafluoropropyl group (-C ３ F ７ ), pentafluorophenyl group (-C ６ F ５ ), trifluoromethoxy group (-OCF ３ ), pentafluoroethoxy group (-OC ２ F ５ ), n-heptafluoropropoxy group (-OC ３ F ７ ), pentafluorophenoxy group (-OC ６ F ５ ), fluoromethyl group (-CH ２ F), difluoromethyl group (-CHF２ ), 2,2,2-trifluoroethyl group (-CH ２ CF ３ ), p-fluorophenyl group (-C ６ H ４ F), methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (-CH ２ CH ２ CH ３ ), i-propyl group (-CH(CH ３ ) ２ ), n-butyl group (-CH ２ CH ２ CH ２ CH ３ ), s-butyl group (-CH ２ CH (CH ３ ) ２ ), t-butyl group (-C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ), cyclohexyl group (-C ６ H １１ ), phenyl group (-C ６ H ５ ), fluorophenyl group (-C ６ H ４ F), trifluoromethylphenyl group (-C ６ H ４ CF ３ ), and trifluoromethoxyphenyl group (-C ６ H ４ OCF ３ Examples include the fluoro group (-F) or the trifluoromethyl group (-CF). ３ ) is preferable.

[0066] M in equation (III) ＋ M in equation (I-1) ＋ This is similar to the example given. M ＋ For example, lithium ion (Li ＋) is preferable.

[0067] Examples of compound (III) include lithium bis(fluorosulfonyl)imide (LiFSI) represented by the following formula (III-1), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) represented by the following formula (III-2). The non-aqueous electrolyte may contain two or more types of compound (III).

[0068]

[0069] The content of compound (III) is not particularly limited and may be 0% to 10% by mass relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered to be 100% by mass). The content of compound (III) may be 0.01% or more by mass, 0.1% or more by mass, 0.3% or more by mass, 0.6% or more by mass, or 0.9% or more by mass. The content of compound (III) may be 5.0% or less by mass, 4.0% or less by mass, 3.0% or less by mass, or 2.0% or less by mass. When the content of compound (III) is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0070] (1.1.4) Compound (IV) Compound (IV) is represented by the following formula (IV).

[0071]

[0072] In formula (IV), R ４１ R represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain a fluoro group (-F) or an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which contains a fluoro group (-F) as a substituent. ４２ This represents a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of a fluoro group (-F) and an oxa group (-O-) as a substituent, or a fluorine carbide group having 1 to 12 carbon atoms, which may contain an oxa group (-O-) as a substituent. ＋ This represents alkali metal ions, alkaline earth metal ions, ammonium ions, imidazolium ions, pyridinium ions, pyrrolidinium ions, piperidinium ions, or phosphonium ions.

[0073] Compound (IV) may also act as an electrolyte, as described later. In this disclosure, regardless of its function, compound (IV) contained in a non-aqueous electrolyte is considered an "additive."

[0074] R ４１ The "fluorine carbide group" represented by R ３１ This is similar to the example given as a "fluorine carbide group" represented by R. ４１ The "hydrocarbon group" represented by R ３１ This is similar to the example given as a "hydrocarbon group" represented by . The oxa group (-O-) may be located at the terminal end of the fluorine carbide group or hydrocarbon group. The oxa group (-O-) is the sulfonyl group (>S (=O) of formula (IV) ２ It may be an alkoxy group (-OR) bonded to the )

[0075] R ４１ The number of carbon atoms in the fluorine carbide group represented by is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. ４１ The number of carbon atoms in the hydrocarbon group represented is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0076] R ４１ Examples include fluoro groups (-F) and trifluoromethyl groups (-CF) ３ ), pentafluoroethyl group (-C ２ F ５ ), n-heptafluoropropyl group (-C ３ F ７ ), pentafluorophenyl group (-C ６ F ５ ), trifluoromethoxy group (-OCF ３ ), pentafluoroethoxy group (-OC ２ F ５ ), n-heptafluoropropoxy group (-OC ３ F ７ ), pentafluorophenoxy group (-OC ６ F ５ ), fluoromethyl group (-CH ２ F), difluoromethyl group (-CHF２ ), 2,2,2-trifluoroethyl group (-CH ２ CF ３ ), p-fluorophenyl group (-C ６ H ４ F), methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (-CH ２ CH ２ CH ３ ), i-propyl group (-CH(CH ３ ) ２ ), n-butyl group (-CH ２ CH ２ CH ２ CH ３ ), s-butyl group (-CH ２ CH (CH ３ ) ２ ), t-butyl group (-C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ), cyclohexyl group (-C ６ H １１ ), phenyl group (-C ６ H ５ ), fluorophenyl group (-C ６ H ４ F), trifluoromethylphenyl group (-C ６ H ４ CF ３ ), and trifluoromethoxyphenyl group (-C ６ H ４ OCF ３ Examples include the fluoro group (-F) or the trifluoromethyl group (-CF). ３ ) is preferable.

[0077] R ４２ The term "hydrocarbon group" as represented by R refers to a hydrocarbon group with one bond position (i.e., a monovalent hydrocarbon group). ４２The "hydrocarbon group" represented by may be an aliphatic hydrocarbon group having a linear structure, or a hydrocarbon group having at least one structure selected from the group consisting of branched structures, cyclic structures, and carbon-carbon unsaturated bond structures (e.g., carbon-carbon double bond structures and carbon-carbon triple bond structures). The number of these structures is also not limited. (Acyclic) aliphatic hydrocarbon groups, monocyclic aliphatic hydrocarbon groups, polycyclic aliphatic hydrocarbon groups, monocyclic aromatic hydrocarbon groups, and polycyclic aromatic hydrocarbon groups are included in "hydrocarbon groups". Alkyl groups, alkenyl groups, alkynyl groups, and aryl groups, etc., are also included in "monovalent hydrocarbon groups". ４２ The expression "a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of a fluoro group (-F) and an oxa group (-O-) as a substituent" means that the hydrogen atoms of the monovalent hydrocarbon group may be substituted with a fluoro group (-F), the carbon atoms of the monovalent hydrocarbon group may be substituted with an oxa group (-O-), or the hydrogen atoms of the monovalent hydrocarbon group may be substituted with a fluoro group (-F) and the carbon atoms of the monovalent hydrocarbon group may be substituted with an oxa group (-O-). The oxa group (-O-) may be located at the terminal end of the fluorine carbide group or hydrocarbon group. The oxa group (-O-) may be an alkoxy group (-OR) bonded to the carbonyl group (>C=O) of formula (IV).

[0078] R ４２ The number of carbon atoms in the hydrocarbon group represented by is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. ４２ The number of carbon atoms in the fluorine carbide group represented by is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0079] R ４２ For example, a methoxy group (-OCH ３ ), ethoxy group (-OCH ２ CH ３ ), n-propoxy group (-OCH ２ CH ２ CH ３ ), t-butyroxy group (-OC(CH ３ )２ ), phenoxy group (-OC ６ H ５ ), fluorophenoxy group (-OC ６ H ４ F), trifluoromethylphenoxy group (-OC ６ H ４ CF ３ ), trifluoromethoxyphenoxy group (-OC ６ H ４ OCF ３ ), methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (-CH ２ CH ２ CH ３ ), i-propyl group (-CH(CH ３ ) ２ ), n-butyl group (-CH ２ CH ２ CH ２ CH ３ ), s-butyl group (-CH ２ CH (CH ３ ) ２ ), t-butyl group (-C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ), cyclohexyl group (-C ６ H １１ ), phenyl group (-C ６ H ５ ), fluoromethyl group (-CH ２ F), difluoromethyl group (-CHF ２ ), 2,2,2-trifluoroethyl group (-CH ２ CF ３ ), p-fluorophenyl group (-C ６ H ４ F), fluorophenyl group (-C ６ H ４ F), trifluoromethylphenyl group (-C ６ H ４ CF３ ), trifluoromethoxyphenyl group (-C ６ H ４ OCF ３ ), trifluoromethoxy group (-OCF ３ ), pentafluoroethoxy group (-OC ２ F ５ ), n-heptafluoropropoxy group (-OC ３ F ７ ), pentafluorophenoxy group (-OC ６ F ５ ), trifluoromethyl group (-CF ３ ), pentafluoroethyl group (-C ２ F ５ ), n-heptafluoropropyl group (-C ３ F ７ ), and pentafluorophenyl group (-C ６ F ５ Examples include the methoxy group (-OCH). ３ ), ethoxy group (-OCH ２ CH ３ ), or n-propoxy group (-OCH ２ CH ２ CH ３ ) is preferable.

[0080] Examples of compounds represented by formula (IV) include lithium salts represented by formula (IV-1), formula (IV-2), formula (IV-3), and formula (IV-4). The non-aqueous electrolyte may contain two or more compounds represented by formula (IV).

[0081]

[0082] The content of compound (IV) is not particularly limited and may be 0% to 10% by mass relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered to be 100% by mass). The content of compound (IV) may be 0.01% or more by mass, 0.10% or more by mass, 0.30% or more by mass, 0.60% or more by mass, 0.80% or more by mass, or 0.90% or more by mass. The content of compound (IV) may be 5.00% or less by mass, 4.0% or less by mass, 3.00% or less by mass, 2.00% or less by mass, or 1.20% or less by mass. When the content of compound (IV) is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0083] (1.1.5) Compound (V) Compound (V) is represented by the following formula (V).

[0084]

[0085] In formula (V), R ５１ This represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain a fluoro group (-F) or an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which contains a fluoro group (-F) as a substituent. ＋ This represents alkali metal ions, alkaline earth metal ions, ammonium ions, imidazolium ions, pyridinium ions, pyrrolidinium ions, piperidinium ions, or phosphonium ions.

[0086] Compound (V) may also act as an electrolyte as described later. In this disclosure, regardless of its function, compound (V) contained in a non-aqueous electrolyte is considered an "additive".

[0087] R ５１ The "fluorine carbide group" represented by R ３１ This is similar to the example given as a "fluorine carbide group" represented by R. ５１ The "hydrocarbon group" represented by R ３１ This is similar to the example given as a "hydrocarbon group" represented by .

[0088] R ５１The number of carbon atoms in the fluorine carbide group represented by is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. ５１ The number of carbon atoms in the hydrocarbon group represented is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0089] M in equation (V) ＋ M in equation (I-1) ＋ This is similar to the example given. M ＋ For example, lithium ion (Li ＋ It is especially preferable that it be of the following nature.

[0090] Compound (V) is lithium fluorosulfonate (LiSO4), represented by the following formula (V-1). ３ F) Lithium trifluoromethanesulfonate (LiSO2), represented by the following formula (V-2) ３ CF ３ Examples include the following. The non-aqueous electrolyte may contain two or more compounds (V).

[0091]

[0092] The content of compound (V) is not particularly limited and may be 0% to 10% by mass relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered to be 100% by mass). The content of compound (V) may be 0.01% or more by mass, 0.10% or more by mass, 0.30% or more by mass, 0.60% or more by mass, or 0.90% or more by mass. The content of compound (V) may be 5.00% or less by mass, 4.00% or less by mass, 3.00% or less by mass, 2.00% or less by mass, or 1.00% or less by mass. When the content of compound (V) is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0093] (1.1.6) Compound (VI) Compound (VI) is represented by the following formula (VI).

[0094]

[0095] In formula (VI), R ６１Each of these independently represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain a fluoro group (-F), an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which contains a fluoro group (-F) as a substituent. i represents an integer from 1 to 4.

[0096] Compound (VI) may also act as an electrolyte, as described later. In this disclosure, regardless of its function, compound (VI) contained in a non-aqueous electrolyte is considered an "additive."

[0097] R ６１ The "fluorine carbide group" represented by R ３１ This is similar to the example given as a "fluorine carbide group" represented by R. ６１ The "hydrocarbon group" represented by R ３１ This is similar to the example given as a "hydrocarbon group" represented by .

[0098] R ６１ The number of carbon atoms in the fluorine carbide group represented by is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. ６１ The number of carbon atoms in the hydrocarbon group represented is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0099] R ６１ Examples include fluoro groups (-F) and trifluoromethyl groups (-CF) ３ ), pentafluoroethyl group (-C ２ F ５ ), n-heptafluoropropyl group (-C ３ F ７ ), pentafluorophenyl group (-C ６ F ５ ), trifluoromethoxy group (-OCF ３ ), pentafluoroethoxy group (-OC ２ F ５ ), n-heptafluoropropoxy group (-OC ３ F ７ ), pentafluorophenoxy group (-OC ６ F ５ ), fluoromethyl group (-CH ２F), difluoromethyl group (-CHF ２ ), 2,2,2-trifluoroethyl group (-CH ２ CF ３ ), p-fluorophenyl group (-C ６ H ４ F), methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (-CH ２ CH ２ CH ３ ), i-propyl group (-CH(CH ３ ) ２ ), n-butyl group (-CH ２ CH ２ CH ２ CH ３ ), s-butyl group (-CH ２ CH (CH ３ ) ２ ), t-butyl group (-C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ), cyclohexyl group (-C ６ H １１ ), phenyl group (-C ６ H ５ ), fluorophenyl group (-C ６ H ４ F), trifluoromethylphenyl group (-C ６ H ４ CF ３ ), and trifluoromethoxyphenyl group (-C ６ H ４ OCF ３ Examples include the fluoro group (-F) or the trifluoromethyl group (-CF). ３ ) is preferable.

[0100] i is preferably 1.

[0101] Examples of compound (VI) include monofluoroethylene carbonate (FEC) represented by the following formula (VI-1), difluoroethylene carbonate (DFEC) represented by the following formula (VI-2), and trifluoropropylene carbonate (TFPC) represented by the following formula (VI-3). The non-aqueous electrolyte may contain two or more types of compound (VI).

[0102]

[0103] The content of compound (VI) is not particularly limited and may be 0% to 10% by mass relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered to be 100% by mass). The content of compound (VI) may be 0.01% or more by mass, 0.1% or more by mass, 0.3% or more by mass, 0.6% or more by mass, or 0.9% or more by mass. The content of compound (VI) may be 5.0% or less by mass, 4.0% or less by mass, 3.0% or less by mass, or 2.0% or less by mass. When the content of compound (VI) is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0104] (1.1.7) Compound (VII) Compound (VII) is represented by the following formula (VII).

[0105]

[0106] In formula (VII), R ７１ Each of these independently represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain a fluoro group (-F), an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of a fluoro group and an oxa group (-O-). j represents an integer from 0 to 2.

[0107] Compound (VII) may also act as an electrolyte, as described later. In this disclosure, regardless of its function, compound (VII) contained in a non-aqueous electrolyte is considered an "additive".

[0108] R ７１ The "fluorine carbide group" represented by R ３１ This is similar to the example given as a "fluorine carbide group" represented by R. ７１The "hydrocarbon group" represented by R ３１ This is similar to the example given as a "hydrocarbon group" represented by .

[0109] R ７１ The number of carbon atoms in the fluorine carbide group represented by is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. ７１ The number of carbon atoms in the hydrocarbon group represented is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0110] R ７１ Examples include fluoro groups (-F) and trifluoromethyl groups (-CF) ３ ), pentafluoroethyl group (-C ２ F ５ ), n-heptafluoropropyl group (-C ３ F ７ ), pentafluorophenyl group (-C ６ F ５ ), trifluoromethoxy group (-OCF ３ ), pentafluoroethoxy group (-OC ２ F ５ ), n-heptafluoropropoxy group (-OC ３ F ７ ), pentafluorophenoxy group (-OC ６ F ５ ), fluoromethyl group (-CH ２ F), difluoromethyl group (-CHF ２ ), 2,2,2-trifluoroethyl group (-CH ２ CF ３ ), p-fluorophenyl group (-C ６ H ４ F), methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (-CH ２ CH ２ CH ３ ), i-propyl group (-CH(CH ３ ) ２ ), n-butyl group (-CH ２ CH２ CH ２ CH ３ ), s-butyl group (-CH ２ CH (CH ３ ) ２ ), t-butyl group (-C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ), cyclohexyl group (-C ６ H １１ ), phenyl group (-C ６ H ５ ), fluorophenyl group (-C ６ H ４ F), trifluoromethylphenyl group (-C ６ H ４ CF ３ ), and trifluoromethoxyphenyl group (-C ６ H ４ OCF ３ Examples include the fluoro group (-F) or the trifluoromethyl group (-CF). ３ ) is preferable.

[0111] It is preferable that j is 0.

[0112] Examples of compound (VII) include vinylene carbonate (VC) represented by the following formula (VII-1), carbonate represented by the following formula (VII-2), and carbonate (TFPC) represented by the following formula (VII-3). The non-aqueous electrolyte may contain two or more types of compound (VII).

[0113]

[0114] The content of compound (VII) is not particularly limited and may be 0% to 10% by mass relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered to be 100% by mass). The content of compound (VII) may be 0.01% or more by mass, 0.10% or more by mass, 0.30% or more by mass, 0.60% or more by mass, 0.80% or more by mass, 0.90% or more by mass, 1.50% or more by mass, or 1.80% or more by mass. The content of compound (VII) may be 5.00% or less by mass, 4.00% or less by mass, 3.00% or less by mass, 2.00% or less by mass, 1.80% or less by mass, 1.50% or less by mass, or 1.30% or less by mass. When the content of compound (VII) is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0115] (1.1.8) Compound (VIII) Compound (VIII) is represented by the following formula (VIII).

[0116]

[0117] In equation (VIII), the double line (solid and dotted) represents a single bond (-) or a double bond (=). ８１ Each of these independently represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain a fluoro group (-F), an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of a fluoro group and an oxa group (-O-). k represents an integer from 0 to 4.

[0118] When the double line (solid and dotted) represents a single bond (-), it means that compound (VIII) is a propensultone compound. When the double line (solid and dotted) represents a double bond (=), it means that compound (VIII) is a propensultone compound.

[0119] R ８１ The "fluorine carbide group" represented by R ３１ This is similar to the example given as a "fluorine carbide group" represented by R. ８１ The "hydrocarbon group" represented by R ３１ This is similar to the example given as a "hydrocarbon group" represented by .

[0120] R ８１ The number of carbon atoms in the fluorine carbide group represented by is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. ８１ The number of carbon atoms in the hydrocarbon group represented is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0121] R ８１ Examples include fluoro groups (-F) and trifluoromethyl groups (-CF) ３ ), pentafluoroethyl group (-C ２ F ５ ), n-heptafluoropropyl group (-C ３ F ７ ), pentafluorophenyl group (-C ６ F ５ ), trifluoromethoxy group (-OCF ３ ), pentafluoroethoxy group (-OC ２ F ５ ), n-heptafluoropropoxy group (-OC ３ F ７ ), pentafluorophenoxy group (-OC ６ F ５ ), fluoromethyl group (-CH ２ F), difluoromethyl group (-CHF ２ ), 2,2,2-trifluoroethyl group (-CH ２ CF ３ ), p-fluorophenyl group (-C ６ H ４ F), methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (-CH ２ CH ２ CH ３ ), i-propyl group (-CH(CH ３ ) ２ ), n-butyl group (-CH ２ CH ２ CH ２ CH ３ ), s-butyl group (-CH ２ CH (CH ３ )２ ), t-butyl group (-C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ), cyclohexyl group (-C ６ H １１ ), phenyl group (-C ６ H ５ ), fluorophenyl group (-C ６ H ４ F), trifluoromethylphenyl group (-C ６ H ４ CF ３ ), trifluoromethoxyphenyl group (-C ６ H ４ OCF ３ Examples include the fluoro group (-F) or the trifluoromethyl group (-CF). ３ ) is preferable.

[0122] k is preferably 0 or 1.

[0123] Examples of compound (VIII) include 1,3-propanesultone (PS) represented by formula (VIII-1) below, sultone represented by formula (VIII-2) below, sultone represented by formula (VIII-3) below, sultone represented by formula (VIII-4) below, 1-propene-1,3-sultone (PRS) represented by formula (VIII-5) below, sultone represented by formula (VIII-6) below, sultone represented by formula (VIII-7) below, sultone represented by formula (VIII-8) below, and the like. The non-aqueous electrolyte may contain two or more types of compound (VIII).

[0124]

[0125] The content of compound (VIII) is not particularly limited and may be 0% to 10% by mass relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered to be 100% by mass). The content of compound (VIII) may be 0.01% or more by mass, 0.1% or more by mass, 0.3% or more by mass, 0.6% or more by mass, or 0.9% or more by mass. The content of compound (VIII) may be 5.0% or less by mass, 4.0% or less by mass, 3.0% or less by mass, or 2.0% or less by mass. When the content of compound (VIII) is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0126] (1.1.9) Compound (IX-1) and Compound (IX-2) Compound (IX-1) is represented by the following formula (IX-1). Compound (IX-2) is represented by the following formula (IX-2).

[0127]

[0128] In formula (IX-1), R ９１ and R ９２ These can be independently substituted with a halogen group, an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ R represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain at least one functional group selected from the group consisting of ). ９３ These can be independently substituted with a halogen group, a cyano group (-CN), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ This represents a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of ).

[0129] In formula (IX-2), R ９１ The substituents are a halogen group, an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ Represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain at least one functional group selected from the group consisting of ). ９３These can be independently substituted with a halogen group, a cyano group (-CN), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ This represents a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of ).

[0130] R ９１ and R ９２ The "divalent hydrocarbon group" represented by R ２１ This is similar to the example given as a "divalent fluorine carbide group" represented by .

[0131] R ９１ The number of carbon atoms in the hydrocarbon group represented is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and particularly preferably 2 or less. ９２ The number of carbon atoms in the hydrocarbon group represented is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and particularly preferably 2 or less.

[0132] R ９１ For example, the methylene group (-CH ２ -), ethylene group (-CH ２ CH ２ -), n-propylene group (-CH ２ CH ２ CH ２ -), and n-butylene group (-CH ２ CH ２ CH ２ CH ２ Examples include methylene group (-CH). ２ -) is preferable. R ９２ For example, the methylene group (-CH ２ -), ethylene group (-CH ２ CH ２ -), n-propylene group (-CH ２ CH ２ CH ２ -), and n-butylene group (-CH ２ CH ２ CH ２ CH ２ Examples include methylene group (-CH). ２ -) is preferable.

[0133] R ９３ The substituents are halogeno groups, cyano groups (-CN), oxa groups (-O-), carbonyl groups (>C=O), and sulfonyl groups (>S(=O)). ２ A hydrocarbon group having 1 to 12 carbon atoms may contain at least one functional group selected from the group consisting of the following: a hydrogen atom of a monovalent hydrocarbon group may be substituted with a halogen group, a hydrogen atom of a monovalent hydrocarbon group may be substituted with a cyano group (-CN), a carbon atom of a monovalent hydrocarbon group may be substituted with an oxa group (-O-), a carbon atom of a monovalent hydrocarbon group may be substituted with a carbonyl group (>C=O), or a carbon atom of a monovalent hydrocarbon group may be substituted with a sulfonyl group (>S(=O) ２ ) may be replaced with.

[0134] R ９３ The number of carbon atoms in the hydrocarbon group represented is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0135] R ９３ For example, a methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (-CH ２ CH ２ CH ３ ), i-propyl group (-CH(CH ３ ) ２ ), n-butyl group (-CH ２ CH ２ CH ２ CH ３ ), s-butyl group (-CH ２ CH (CH ３ ) ２ ), t-butyl group (-C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ), cyclohexyl group (-C ６ H １１), and phenyl group (-C ６ H ５ Examples include:

[0136] Examples of compound (IX-1) include methylene methane disulfonate (MMDS) represented by the following formula (IX-1-1). Examples of compound (IX-2) include disulfonic acid esters represented by the following formula (IX-2-1). The non-aqueous electrolyte may contain two or more types of compound (IX-1). The non-aqueous electrolyte may contain two or more types of compound (IX-2).

[0137]

[0138] The content of compound (IX-1) and compound (IX-2) is not particularly limited and may be 0% to 10% by mass relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered to be 100% by mass). The content of compound (IX-1) and compound (IX-2) may be 0.01% by mass or more, 0.1% by mass or more, 0.3% by mass or more, 0.6% by mass or more, or 0.9% by mass or more. The content of compound (IX-1) and compound (IX-2) may be 5.0% by mass or less, 4.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less. When the content of these compounds (IX-1) and compounds (IX-2) is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0139] (1.1.10) Compound (X) Compound (X) is represented by the following formula (X).

[0140]

[0141] In formula (X), R １０１ is a methylene group (-CH ２ -), ethylene group (-CH ２ CH ２ -), or n-propylene group (-CH ２ CH ２ CH ２ Represents (-). １０２Each of these independently represents a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (x-3), a group represented by formula (x-4), a group represented by formula (x-5), a group represented by formula (x-6), a group represented by formula (x-7), or a group represented by formula (x-8), which may each contain at least one functional group selected from the group consisting of a halogen group (-X) and an oxa group (-O-). １０１ is a methylene group (-CH ２ When -, m represents an integer between 0 and 2. １０１ is an ethylene group (-CH ２ CH ２ When -, m represents an integer from 0 to 4. １０１ is an n-propylene group (-CH ２ CH ２ CH ２ When (-), m represents an integer between 0 and 6.

[0142]

[0143] R １０１ is an ethylene group (-CH ２ CH ２ -), or n-propylene group (-CH ２ CH ２ CH ２ It is preferable that it be -, and the ethylene group (-CH ２ CH ２ -) is more preferable.

[0144] R １０２ The term "hydrocarbon group" as represented by R refers to a hydrocarbon group with one bond position (i.e., a monovalent hydrocarbon group). １０２The "hydrocarbon group" represented by may be an aliphatic hydrocarbon group having a linear structure, or a hydrocarbon group having at least one structure selected from the group consisting of branched structures, cyclic structures, and carbon-carbon unsaturated bond structures (e.g., carbon-carbon double bond structures and carbon-carbon triple bond structures). The number of these structures is also not limited. (Acyclic) aliphatic hydrocarbon groups, monocyclic aliphatic hydrocarbon groups, polycyclic aliphatic hydrocarbon groups, monocyclic aromatic hydrocarbon groups, and polycyclic aromatic hydrocarbon groups are included in "hydrocarbon groups". Alkyl groups, alkenyl groups, alkynyl groups, and aryl groups, etc., are also included in "monovalent hydrocarbon groups". １０２ The expression "a hydrocarbon group having 1 to 6 carbon atoms which may contain at least one functional group selected from the group consisting of a halogen group (-X) and an oxa group (-O-) as a substituent" means that the hydrogen atoms of the monovalent hydrocarbon group may be substituted with a halogen group (-X), the carbon atoms of the monovalent hydrocarbon group may be substituted with an oxa group (-O-), and the hydrogen atoms of the monovalent hydrocarbon group may be substituted with a halogen group (-X) and the carbon atoms of the monovalent hydrocarbon group may be substituted with an oxa group (-O-).

[0145] In equations (x-3), (x-4), (x-5), (x-6), (x-7), and (x-8), the dashed lines indicate that the end of the dashed line is R. １０１ The methylene group (-CH ２ -) ``Ethylene group (-CH ２ CH ２ -) or "n-propylene group (-CH ２ CH ２ CH ２ -) means that it is bonded as a substituent to the hydrogen atom. The two wavy lines in (x-8) have R at the end of each line. １０１ The methylene group (-CH ２ -) ``Ethylene group (-CH ２ CH ２ -) or "n-propylene group (-CH ２ CH ２ CH ２ -) means that it is bonded as a substituent to a hydrogen atom. For example, the ends of the two wavy lines are R １０１It may be bonded to the same carbon atom or to different carbon atoms.

[0146] R １０２ The number of carbon atoms in the hydrocarbon group represented is preferably 5 or less, more preferably 4 or less.

[0147] R １０２ For example, a methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (-CH ２ CH ２ CH ３ ), i-propyl group (-CH(CH ３ ) ２ ), n-butyl group (-CH ２ CH ２ CH ２ CH ３ ), s-butyl group (-CH ２ CH (CH ３ ) ２ ), t-butyl group (-C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ), cyclohexyl group (-C ６ H １１ ), phenyl group (-C ６ H ５ ), fluorophenyl group (-C ６ H ４ F), trifluoromethylphenyl group (-C ６ H ４ CF ３ ), trifluoromethoxyphenyl group (-C ６ H ４ OCF ３ Examples include the group represented by formula (x-3), the group represented by formula (x-4), the group represented by formula (x-5), the group represented by formula (x-6), the group represented by formula (x-7), and the group represented by formula (x-8). Among these, the n-propyl group (-CH) is particularly noteworthy. ２ CH ２ CH３ A base represented by formula (x-3) is preferred.

[0148] m is preferably 0 or 1.

[0149] Examples of compound (X) include 1,3,2-dioxathiolane 2,2-dioxide (DTD) represented by the following formula (X-1), sulfate esters represented by the following formula (X-2), sulfate esters represented by the following formula (X-3), sulfate esters represented by the following formula (X-4), sulfate esters represented by the following formula (X-5), sulfate esters represented by the following formula (X-6), sulfate esters represented by the following formula (X-7), and sulfate esters represented by the following formula (X-8). The non-aqueous electrolyte may contain two or more types of compound (X).

[0150]

[0151] The content of compound (X) is not particularly limited and may be 0% to 10% by mass relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered to be 100% by mass). The content of compound (X) may be 0.01% or more by mass, 0.10% or more by mass, 0.30% or more by mass, 0.60% or more by mass, 0.80% or more by mass, 0.90% or more by mass, 1.50% or more by mass, or 1.80% or more by mass. The content of compound (X) may be 5.00% or less by mass, 4.00% or less by mass, 3.00% or less by mass, 2.00% or less by mass, 1.50% or less by mass, or 1.20% or less by mass. When the content of compound (X) is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0152] (1.1.11) Compound (XI) Compound (XI) is represented by the following formula (XI).

[0153]

[0154] In equation (XI), two R １１１ Each of these independently represents a hydrocarbon group having 1 to 12 carbon atoms or a trialkylsilyl group having 3 to 18 carbon atoms.

[0155] R １１１ The "trialkylsilyl group with 3 to 18 carbon atoms" represented by -SiR３ As shown, it is a group in which three hydrocarbon groups are bonded to a silicon atom, and the number of carbon atoms represents the total number of carbon atoms in the three hydrocarbon groups.

[0156] R １１１ The number of carbon atoms in the hydrocarbon group represented by is preferably 2 or more, more preferably 3 or more, preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. １１１ The number of carbon atoms in the trialkylsilyl group represented by is preferably 12 or less, more preferably 9 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0157] R １１１ Examples of hydrocarbon groups represented include the methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (-CH ２ CH ２ CH ３ ), i-propyl group (-CH(CH ３ ) ２ ), n-butyl group (-CH ２ CH ２ CH ２ CH ３ ), s-butyl group (-CH ２ CH (CH ３ ) ２ ), t-butyl group (-C(CH ３ ) ２ ), cyclohexyl group (-C ６ H １１ ), and phenyl group (-C ６ H ５ Examples include: ３１ Examples of trialkylsilyl groups represented by this include the trimethylsilyl group (-Si(CH ３ ) ３ ), and triethylsilyl group (-Si(CH ２ CH ３ ) ３ Examples include i-propyl group (-CH(CH ３ ) ２ ), cyclohexyl group (-C ６ H１１ ), or trimethylsilyl group (-Si(CH ３ ) ３ ) is preferable.

[0158] Examples of compound (XI) include N,N'-di-i-propylcarbodiimide represented by the following formula (XI-1), N,N'-dicyclohexylcarbodiimide represented by the following formula (XI-2), and N,N'-bis(trimethylsilyl)carbodiimide represented by the following formula (XI-3). The non-aqueous electrolyte may contain two or more types of compound (XI).

[0159]

[0160] The content of compound (XI) is not particularly limited and may be 0% to 10% by mass relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is considered to be 100% by mass). The content of compound (XI) may be 0.01% or more by mass, 0.1% or more by mass, 0.3% or more by mass, 0.6% or more by mass, or 0.9% or more by mass. The content of compound (XI) may be 5.0% or less by mass, 4.0% or less by mass, 3.0% or less by mass, or 2.0% or less by mass. When the content of compound (XI) is within the above range, it becomes easier to improve the capacity retention rate after high-temperature charge-discharge cycle testing.

[0161] (1.1.12) Preferred Embodiments The additive is preferably satisfied with the following conditions (i), (ii), or (iii): (i) The additive contains compound (VII) and compound (X); (ii) The additive contains compound (VII) but does not contain compound (X); (iii) The additive contains only compound (X). By satisfying conditions (i), (ii), or (iii), the non-aqueous electrolyte of this disclosure can further improve the capacity retention rate after high-temperature charge-discharge cycle testing in a non-aqueous electrolyte secondary battery equipped with a negative electrode with a low binder content. When the additive satisfies (i), the content of compound (VII) relative to the total amount of the non-aqueous electrolyte may be 0.5% to 1.5% by mass, and the content of compound (X) relative to the total amount of the non-aqueous electrolyte may be 0.5% to 1.5% by mass. If the additive satisfies (ii), the content of compound (VII) relative to the total amount of the non-aqueous electrolyte may be 0.5% to 2.5% by mass, and the content of compound (X) relative to the total amount of the non-aqueous electrolyte may be 0% by mass. If the additive satisfies (iii), the content of compound (X) relative to the total amount of the non-aqueous electrolyte may be 2.00% to 2.50% by mass.

[0162] The additive may contain only compound (VII) and compound (X). The reason is not entirely clear, but it is thought that compound (X) first forms a uniform film on the entire surface of the active material during the initial charge, and then compound (VII) forms a film on the areas of the negative electrode active material surface where compound (X) was insufficient. When the additive contains only compound (VII) and compound (X), the content of compound (VII) relative to the total amount of the non-aqueous electrolyte may be 0.5% to 1.5% by mass, and the content of compound (X) relative to the total amount of the non-aqueous electrolyte may be 0.5% to 1.5% by mass.

[0163] The additive preferably satisfies the following conditions (ia), (iia), or (iib): (ia) The additive contains compound (VII) and compound (X), and compound (I) or compound (II); (iia) The additive contains compound (VII) but does not contain compound (X), and the content of compound (VII) relative to the total amount of the non-aqueous electrolyte is 1.50% to 2.50% by mass; (iib) The additive contains compound (VII) and compound (II) but does not contain compound (X). By satisfying the conditions (ia), (iia), or (iib), the non-aqueous electrolyte of this disclosure can further improve the capacity retention rate after high-temperature charge-discharge cycle testing in a non-aqueous electrolyte secondary battery equipped with a negative electrode with a low binder content. The additive may contain compound (IV), compound (VII), and compound (X). As a result, in addition to the above effects of compound (VII) and compound (X), compound (IV) is expected to repair the coating that was damaged during the high-temperature charge-discharge cycle test. When the additive satisfies condition (ia), the content of compound (VII) relative to the total amount of the non-aqueous electrolyte may be 0.5% to 1.5% by mass, the content of compound (X) relative to the total amount of the non-aqueous electrolyte may be 0.5% to 1.5% by mass, and the content of compound (I) or compound (II) relative to the total amount of the non-aqueous electrolyte may be 0.5% to 1.5% by mass. When the additive satisfies condition (iib), the content of compound (VII) relative to the total amount of the non-aqueous electrolyte may be 0.5% to 1.5% by mass, and the content of compound (II) relative to the total amount of the non-aqueous electrolyte may be 0.5% to 1.5% by mass.

[0164] The additive preferably satisfies the following condition (ia). By satisfying condition (ia), the non-aqueous electrolyte of this disclosure can further improve the capacity retention rate after high-temperature charge-discharge cycle testing in a non-aqueous electrolyte secondary battery equipped with a negative electrode having a low binder content.

[0165] (1.2) Non-aqueous solvents Non-aqueous electrolytes generally contain a non-aqueous solvent. Various known non-aqueous solvents can be appropriately selected. There may be only one type of non-aqueous solvent, or there may be two or more types.

[0166] Examples of non-aqueous solvents include cyclic carbonates, fluorinated cyclic carbonates, linear carbonates, fluorinated linear carbonates, aliphatic carboxylic acid esters, fluorinated aliphatic carboxylic acid esters, γ-lactones, fluorinated γ-lactones, cyclic ethers, fluorinated cyclic ethers, linear ethers, fluorinated linear ethers, nitriles, amides, lactams, nitromethane, nitroethane, sulfolanes, trimethyl phosphate, dimethyl sulfoxide, and dimethyl sulfoxide phosphate. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Examples of fluorinated cyclic carbonates include fluoroethylene carbonate (FEC). Examples of linear 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 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 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 linear ethers include 1,2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, 1,2-dimethoxyethane, and 1,2-dibutoxyethane. Examples of nitriles include acetonitrile, glutalonitrile, adiponitrile, methoxyacetonitrile, and 3-methoxypropionitrile. Examples of amides include N,N-dimethylformamide.Examples of lactam compounds include N-methylpyrrolidinone, N-methyloxazolidinone, and N,N'-dimethylimidazolidinone.

[0167] The non-aqueous solvent preferably contains at least one selected from the group consisting of cyclic carbonates, fluorine-containing cyclic carbonates, linear carbonates, and fluorine-containing linear carbonates. In this case, the total proportion of cyclic carbonates, fluorine-containing cyclic carbonates, linear carbonates, and fluorine-containing linear carbonates is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass, based on the total amount of the non-aqueous solvent.

[0168] The non-aqueous solvent preferably contains at least one selected from the group consisting of cyclic carbonates and linear carbonates. In this case, the total proportion of cyclic carbonates and linear carbonates is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass, based on the total amount of the non-aqueous solvent.

[0169] The non-aqueous solvent content is preferably 99% by mass, more preferably 97% by mass, and even more preferably 90% by mass, relative to the total amount of the non-aqueous electrolyte. The non-aqueous solvent content is preferably 60% by mass or more, more preferably 70% by mass or more, relative to the total amount of the non-aqueous electrolyte.

[0170] 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 of the electrolyte and the mobility of ions.

[0171] (1.3) Non-aqueous electrolytes generally contain electrolytes.

[0172] The electrolyte preferably contains at least one of a lithium salt containing fluorine (hereinafter sometimes referred to as "fluorinated lithium salt") and a lithium salt that does not contain fluorine.

[0173] Examples of fluorinated lithium salts include inorganic acid anionic salts and organic acid anionic salts. Examples of inorganic acid anionic salts include lithium hexafluoride phosphate (LiPF). ６ ), lithium tetrafluoroborate (LiBF ４ ), lithium hexafluoride arsenate (LiAsF ６ ), and lithium tantalate hexafluoride (LiTaF ６ Examples of organic acid anionic salts include lithium bis(pentafluoroethanesulfonyl)imide (Li(C)). ２ F ５ SO ２ ) ２ Examples include N). Among them, lithium hexafluoride phosphate (LiPF) is an example of a fluorinated lithium salt. ６ ) is preferable.

[0174] Lithium salts that do not contain fluorine include lithium perchlorate (LiClO2). ４ ), lithium aluminum tetrachloride (LiAlCl ４ ), and lithium decachlorodecaborate (Li ２ B １０ Cl １０ ) are some examples.

[0175] When the electrolyte contains a fluorinated lithium salt, the content of the fluorinated lithium salt is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass, relative to the total amount of the electrolyte. ６ If it contains lithium hexafluoride phosphate (LiPF), ６ The content ratio of ) is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass, relative to the total amount of electrolyte.

[0176] When the non-aqueous electrolyte contains an electrolyte, the concentration of the electrolyte in the non-aqueous electrolyte is preferably 0.1 mol / L to 3 mol / L, more preferably 0.5 mol / L to 2 mol / L.

[0177] The non-aqueous electrolyte is lithium hexafluoride phosphate (LiPF). ６ ) If it contains lithium hexafluoride phosphate (LiPF) in a non-aqueous electrolyte, ６ The concentration of the substance is preferably 0.1 mol / L to 3 mol / L, more preferably 0.5 mol / L to 2 mol / L.

[0178] (2) The negative electrode non-aqueous electrolyte is for a non-aqueous electrolyte secondary battery equipped with the specific negative electrode described above. The specific negative electrode has a current collector and a negative electrode composite layer formed on the current collector. The negative electrode composite layer contains a negative electrode active material. The negative electrode composite layer satisfies either (a) or (b) below: (a) The negative electrode composite layer does not contain a binder (i.e., the binder content is 0% by mass of the total amount of the negative electrode composite layer) (b) The negative electrode composite layer further contains a binder, and the binder content is greater than 0% by mass and 0.5% by mass or less of the total amount of the negative electrode composite layer

[0179] The negative electrode composite layer preferably satisfies (a) below. While binders act as reaction inhibitors and cause non-uniformity of the reaction, leading to degradation, satisfying (a) eliminates the presence of reaction inhibitors, allowing the battery reaction to proceed uniformly within the composite layer. This suppresses localized degradation reactions, thereby improving battery life. Note that "binder" refers to a functional polymer material that maintains the structural integrity and electrical contact of the electrodes while withstanding volume changes and stresses associated with charging and discharging.

[0180] Typically, the negative electrode of a non-aqueous electrolyte secondary battery can be manufactured by applying a slurry to a current collector, drying it, and compressing it to form a negative electrode composite layer on the current collector. The slurry comprises a negative electrode active material, a binder, and a solvent, and optionally further comprises a conductive additive and a thickener dispersed in the solvent.

[0181] (2.1) Negative electrode composite layer (2.1.1) Binder When the negative electrode composite layer satisfies (b), the type of binder is not particularly limited and known ones can be appropriately selected. Examples of binders include rubber particles, polyvinyl acetate, polymethyl methacrylate, nitrocellulose, and fluororesins. Examples of rubber particle materials include styrene-butadiene rubber (SBR) and acrylonitrile rubber. Examples of fluororesins include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and vinylidene fluoride-hexafluoropropylene copolymer.

[0182] When the negative electrode composite layer satisfies (b), the binder content relative to the total amount of the negative electrode composite layer is preferably 0.3% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0% by mass. When the binder content is within the above range, the reaction within the electrode becomes more uniform, which suppresses degradation phenomena (e.g., Li electrodeposition and overcharging), and tends to extend the lifespan of the non-aqueous electrolyte secondary battery.

[0183] (2.1.2) Negative electrode active material The element or compound that will be the negative electrode active material may be any of the following (i) to (iii): (i) Elemental carbon and carbon compounds that can be doped / dedoped with lithium ions (ii) Metals and alloys that can be alloyed with lithium (iii) Compounds that can be doped / dedoped with lithium ions (e.g., oxides, nitrides, and carbides) If the negative electrode active material is elemental silicon, the negative electrode active material may be in the form of particulate (powder) elements or compounds. The negative electrode active material may be used alone or by mixing two or more types.

[0184] Examples of negative electrode active materials include elemental carbon particles, elemental silicon particles, silicon oxide particles, and silicon carbide particles. Examples of elemental carbon particles include graphite (natural graphite, artificial graphite) particles, carbon black particles, activated carbon particles, and amorphous carbon particles. Examples of artificial graphite include graphitized mesocarbon microbeads (MCMB) and graphitized mesophase pitch carbon fibers (MCF). Examples of amorphous carbon materials include hard carbon, coke, MCMB and MCF fired at temperatures below 1500°C.

[0185] When the negative electrode active material is in particulate (powder) form, the detailed shape of the negative electrode active material can be fibrous, spherical, potato-shaped, or flake-shaped.

[0186] The median diameter (D) of a single carbon particle ５０ The median diameter (D) of elemental carbon particles is usually 1 μm to 30 μm, preferably 20 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, and particularly preferably 7 μm or less. ５０ ) is usually 1.0 μm or larger.

[0187] The negative electrode active material has a median diameter (D ５０ It is preferable that the negative electrode active material contains graphite particles with a median diameter (D) of 10 μm or less. ５０ The required amount of additives in the non-aqueous electrolyte also increases if the electrolyte contains graphite particles smaller than 10 μm. The Discloser has made it clear that conventional amounts of additives do not provide sufficient charge-discharge characteristics, particularly the capacity retention rate after high-temperature charge-discharge cycle tests. The Discloser has also made it clear that the capacity retention rate after high-temperature charge-discharge cycle tests can be improved by increasing the total additive content to 2.0% by mass or more.

[0188] The BET specific surface area of ​​elemental carbon particles is typically 2.0 m². ２ / g to 8.0m ２ The value is / g, preferably 3.0m ２ / g or more, preferably 5.0m ２ / g or more, more preferably 5.5m ２ The amount is 7.0 m or more, preferably 7.0 m ２ / g or less, more preferably 6.0m ２ It is less than or equal to / g.

[0189] Silicon dioxide is SiO ｘ It is expressed as follows. x (i.e., the oxygen atom content in silicon dioxide) is not particularly limited. x is usually 0 ≤ x < 2, preferably 0.2 or more, more preferably 0.4 or more, even more preferably 0.6 or more, preferably 1.8 or less, more preferably 1.6 or less, and even more preferably 1.4 or less.

[0190] The median diameter (D) of elemental silicon particles, silicon oxide particles, or silicon carbide particles. ５０ The particle size is usually 0.5 μm to 20 μm, preferably 1.0 μm or more, more preferably 3.0 μm or more, preferably 15 μm or less, and more preferably 10 μm or less.

[0191] The BET specific surface area of ​​elemental silicon particles, silicon oxide particles, or silicon carbide particles is typically 1.0 m². ２ / g to 5.0m ２ The value is / g, preferably 1.5m ２ / g or more, more preferably 2.0m ２ The amount is 1 / g or more, preferably 4.5m ２ / g or less, more preferably 4.0m ２ It is less than or equal to / g.

[0192] When the negative electrode active material includes elemental carbon particles and at least one selected from the group consisting of elemental silicon particles, silicon oxide particles, and silicon carbide particles, the total mass of elemental silicon particles, silicon oxide particles, and silicon carbide particles in the negative electrode active material is usually 1% to 20% by mass, preferably 3% or more by mass, more preferably 5% or more by mass, preferably 18% or less by mass, and more preferably 15% or less by mass, when the total mass of the entire negative electrode active material is taken as 100% by mass.

[0193] When the negative electrode active material includes elemental carbon particles and at least one selected from the group consisting of elemental silicon particles, silicon oxide particles, and silicon carbide particles, the total mass of elemental carbon particles in the negative electrode active material is usually 70% to 99% by mass, preferably 80% or more by mass, preferably 95% or less by mass, and more preferably 90% or less by mass, when the total mass of the entire negative electrode active material is taken as 100% by mass. When the total mass of elemental silicon particles, etc., is within the above range, it becomes easier to ensure a balance between the energy density and capacity retention rate of the non-aqueous electrolyte secondary battery.

[0194] The total content of the negative electrode active material is typically 70% to 99.5% by mass, preferably 75% or more by mass, and preferably 99% or less by mass, when the total amount of the negative electrode composite layer is considered as 100% by mass.

[0195] (2.1.3) The conductive additive negative electrode composite layer preferably further contains a conductive additive. Examples of conductive additives for the negative electrode include carbon black (e.g., acetylene black), carbon nanotubes, amorphous whiskers, and graphite.

[0196] The negative electrode composite layer contains a conductive additive, which preferably contains carbon nanotubes, and more preferably single-walled carbon nanotubes. The carbon nanotubes act as both a conductive additive and a molding aid. Therefore, it becomes easier to ensure moldability even when the amount of binder is reduced.

[0197] The total content of the conductive additive in the negative electrode composite layer is typically 0.01% to 3% by mass, preferably 0.05% or more by mass, more preferably 0.1% or more by mass, preferably 2% or less by mass, and more preferably 1% or less by mass, when the total amount of the negative electrode composite layer is considered as 100% by mass.

[0198] Preferably, the conductive additive consists of carbon nanotubes, and the carbon nanotube content is 0.5% by mass or less relative to the total amount of the negative electrode composite layer. This suppresses side reactions of the electrolyte on the conductive additive and improves high-temperature cycle characteristics. The content of the conductive additive is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, preferably 0.5% by mass or less, and more preferably 0.4% by mass or less.

[0199] The negative electrode composite layer contains a conductive additive different from carbon nanotubes, and the content of the conductive additive is preferably 0.5% by mass or less of the total amount of the negative electrode composite layer. This suppresses side reactions of the electrolyte on the conductive additive and improves high-temperature cycling characteristics. The content of the conductive additive is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, preferably 0.5% by mass or less, and more preferably 0.4% by mass or less.

[0200] (2.1.4) The anode composite layer preferably further contains a thickening agent. The inclusion of a thickening agent in the slurry makes it easier to adjust the viscosity of the slurry and improves productivity. Examples of thickening agents for the anode composite layer include cellulose derivatives such as carboxymethylcellulose (CMC), carboxyethylcellulose, and hydroxyethylcellulose, polyoxyethylene and its modified forms, polyvinyl alcohol and its modified forms, and polysaccharides.

[0201] The total content of the thickening agent in the negative electrode composite layer is usually 0.1% to 5% by mass, preferably 0.5% or more by mass, more preferably 1.0% or more by mass, preferably 3% or less by mass, and more preferably 2% or less by mass, when the total amount of the negative electrode composite layer is considered as 100% by mass.

[0202] (2.1.5) The solvent slurry may contain a solvent. Examples of solvents include water, acetonitrile, N-methylpyrrolidone, acetylpyridine, cyclopentanone, dimethylformamide, dimethyl sulfoxide, methylformamide, methyl ethyl ketone, furfural, and ethylenediamine. The solvent may be a mixed solvent obtained by mixing the aforementioned solvents.

[0203] (2.2) Current collector of the negative electrode Examples of materials for the current collector of the negative electrode include copper, nickel, stainless steel, and nickel-plated steel.

[0204] (3) Non-aqueous electrolyte secondary battery Another embodiment of the present disclosure is a non-aqueous electrolyte secondary battery comprising a "positive electrode", a "negative electrode", a "non-aqueous electrolyte", and a "separator".

[0205] (3.1) Positive electrode The positive electrode can usually be manufactured by applying a slurry to a current collector, drying and compressing it to form a positive electrode composite layer on the current collector. The slurry comprises a positive electrode active material, a binder, and a solvent, and optionally further comprises a conductive additive and a thickener dispersed in the solvent.

[0206] As the positive electrode active material, MoS ２ TiS ２ MnO ２ , V ２ O ５ Transition metal oxides or transition metal sulfides such as LiCoO ２ LiMnO ２ LiMn ２ O ４ LiNiO ２ LiNi Ｘ Co （１－Ｘ） O ２ (0<X<1), LiNi ｘ Co ｙ Mn ｚ O ２ (x, y, and z are each independently greater than 0 and less than 1.00, and the sum of x, y, and z is between 0.99 and 1.00.) (So-called "NCM"; for example, LiNi ０．３３ Co ０．３３ Mn ０．３３ O ２ LiNi ０．５ Co ０．３ Mn ０．２ O ２ LiNi ０．５ Co ０．２ Mn ０．３ O ２ LiNi ０．６ Co ０．２ Mn ０．２ O ２ LiNi０．８ Co ０．１ Mn ０．１ O ２ Composite oxides consisting of lithium and transition metals such as Li ｔ Ni １－ｘ－ｙ Co ｘ Al ｙ O ２ (t is between 0.95 and 1.15, x is between 0 and 0.3, y is between 0.1 and 0.2, and the sum of x and y is less than 0.5.) (So-called "NCA"; for example, LiNi ０．８ Co ０．１５ Al ０．０５ O ２ Composite oxides consisting of lithium, transition metals and typical metals such as ); conductive polymer materials such as polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazole, and polyaniline composites; and lithium iron phosphate (LiFePO) ４ ), Lithium manganese phosphate (LiMnPO ４ ), Lithium iron manganese phosphate (LiMn ｘ Fe １－ｘ PO ４ ; 0 < x < 1), LiCoPO2 ４ ), lithium nickel phosphate (LiNiPO ４ Examples include lithium metal phosphate such as ) and others.

[0207] Examples of binders for the positive electrode include polyvinylidene fluoride. Examples of conductive additives for the positive electrode include carbon black (e.g., acetylene black), amorphous whiskers, and graphite. Examples of thickeners for the positive electrode include carboxymethylcellulose. Examples of solvents for the slurry used to form the positive electrode include organic solvents such as N-methylpyrrolidone.

[0208] The total content of the positive electrode active material is typically 70% to 99.5% by mass, preferably 75% or more by mass, and preferably 99% or less by mass, when the total amount of the positive electrode composite layer is considered as 100% by mass.

[0209] Examples of materials for the positive electrode current collector include aluminum, aluminum alloy, stainless steel, nickel, titanium, tantalum, carbon cloth, and carbon paper.

[0210] (3.2) Separator An example of a separator is a porous resin plate. Examples of materials for the porous resin plate include resin and nonwoven fabric containing this resin. Examples of resins include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyester, cellulose, and polyamide. Among these, the separator is preferably a porous resin sheet with a single-layer or multi-layer structure. The material of the porous resin sheet is mainly at least one polyolefin resin. The thickness of the separator is preferably 5 μm to 30 μm. The separator is preferably placed between the positive electrode and the negative electrode.

[0211] (3.3) Case The shape of the case is not particularly limited and can be appropriately selected depending on the application of the non-aqueous electrolyte secondary battery of this disclosure. Examples of cases include cases including a laminate film, and cases consisting of a battery can and a battery can lid.

[0212] (4) Specific Examples of Non-Aqueous Electrolyte Secondary Batteries (4.1) Stacked Type Figure 1 is a schematic cross-sectional view showing a stacked type non-aqueous electrolyte secondary battery, which is an example of a non-aqueous electrolyte secondary battery of the present disclosure.

[0213] As shown in Figure 1, the non-aqueous electrolyte secondary battery 1 is a stacked battery. More specifically, in the non-aqueous electrolyte secondary battery 1, the battery element 10 is sealed inside a case 30. The case 30 is made of laminate film. The battery element 10 is fitted with a positive electrode lead 21 and a negative electrode lead 22. The positive electrode lead 21 and the negative electrode lead 22 are led out in opposite directions from the inside to the outside of the case 30.

[0214] As shown in Figure 1, the battery element 10 is made up of a stack of a positive electrode 11, a separator 13, and a negative electrode 12. The positive electrode 11 has a positive electrode composite layer 11B formed on both main surfaces of the positive electrode current collector 11A. The negative electrode 12 has a negative electrode composite layer 12B formed on both main surfaces of the negative electrode current collector 12A. The positive electrode composite layer 11B formed on one main surface of the positive electrode current collector 11A of the positive electrode 11 and the negative electrode composite layer 12B formed on one main surface of the negative electrode current collector 12A of the negative electrode 12 adjacent to the positive electrode 11 face each other via the separator 13.

[0215] The non-aqueous electrolyte of this disclosure is injected into the case 30 of the non-aqueous electrolyte secondary battery 1. The non-aqueous electrolyte of this disclosure permeates the positive electrode composite layer 11B, the separator 13, and the negative electrode composite layer 12B. In the non-aqueous electrolyte secondary battery 1, a single cell layer 14 is formed by adjacent positive electrode composite layers 11B, the separator 13, and the negative electrode composite layer 12B. The positive electrode may have a positive electrode composite layer formed on one side of the current collector. The negative electrode may have a negative electrode composite layer formed on one side of the current collector.

[0216] The non-aqueous electrolyte secondary battery 1 is a stacked type non-aqueous electrolyte secondary battery, but the non-aqueous electrolyte secondary battery of this disclosure is not limited thereto, and may be, for example, a wound type non-aqueous electrolyte secondary battery. The wound type non-aqueous electrolyte secondary battery is formed by stacking a positive electrode, a separator, a negative electrode, and a separator in this order and winding them in layers. The wound type non-aqueous electrolyte secondary battery includes cylindrical non-aqueous electrolyte secondary batteries and prismatic non-aqueous electrolyte secondary batteries.

[0217] As shown in Figure 1, in the non-aqueous electrolyte secondary battery 1, the directions in which the positive electrode lead and the negative electrode lead protrude from the inside to the outside of the case 30 are opposite to the case 30, but the disclosure is not limited thereto. For example, the way in which the positive electrode lead and the negative electrode lead protrude from the inside to the outside of the case 30 is the same direction with respect to the case 30.

[0218] The non-aqueous electrolyte secondary battery 1 is obtained by charging and discharging a non-aqueous electrolyte secondary battery precursor. The non-aqueous electrolyte secondary battery precursor is the same as the non-aqueous electrolyte secondary battery 1 except that it has not been charged and discharged (i.e., no SEI (Solid Electrolyte Interphase) film is attached to the surface of the positive electrode and the surface of the negative electrode).

[0219] (4.2) Coin-type Figure 2 is a schematic cross-sectional view showing a coin-type non-aqueous electrolyte secondary battery, which is another example of a non-aqueous electrolyte secondary battery of the present disclosure.

[0220] In the coin-type non-aqueous electrolyte secondary battery shown in Figure 2, a disc-shaped negative electrode 42, a separator 45 into which the non-aqueous electrolyte is injected, a disc-shaped positive electrode 41, and, if necessary, spacer plates 47 and 48 made of stainless steel or aluminum are stacked in this order and housed between the positive electrode can 43 (hereinafter also referred to as the "battery can") and the sealing plate 44 (hereinafter also referred to as the "battery can lid"). The positive electrode can 43 and the sealing plate 44 are crimped and sealed via a gasket 46. In this example, the non-aqueous electrolyte of this disclosure is used as the non-aqueous electrolyte injected into the separator 45.

[0221] (5) Non-aqueous electrolyte secondary battery and method for manufacturing the same The method for manufacturing a non-aqueous electrolyte secondary battery according to the present disclosure includes a step of preparing a non-aqueous electrolyte secondary battery precursor (hereinafter also referred to as the "preparation step") and a step of charging and discharging the non-aqueous electrolyte secondary battery precursor. The non-aqueous electrolyte secondary battery according to the present disclosure is a non-aqueous electrolyte secondary battery obtained by charging and discharging a non-aqueous electrolyte secondary battery precursor.

[0222] The "non-aqueous electrolyte secondary battery precursor" is the same as a non-aqueous electrolyte secondary battery, except that it has not undergone charging and discharging (i.e., no SEI (Solid Electrolyte Interphase) film is attached to the surface of the positive electrode and the surface of the negative electrode).

[0223] According to the non-aqueous electrolyte secondary battery and its manufacturing method, the rate of increase in resistance at room temperature during high-temperature storage of the non-aqueous electrolyte secondary battery can be reduced.

[0224] The preparation step may simply be a step of preparing a pre-manufactured non-aqueous electrolyte secondary battery precursor of the present disclosure for use in the charging and discharging process, or it may be a step of manufacturing the non-aqueous electrolyte secondary battery precursor of the present disclosure.

[0225] In the charging and discharging process, the charging and discharging of the non-aqueous electrolyte secondary battery precursor can be carried out according to known methods. In this process, the charging and discharging cycle may be repeated multiple times for the non-aqueous electrolyte secondary battery precursor. As described above, this charging and discharging preferably forms an SEI film on at least one surface of the positive electrode (particularly the positive electrode active material) and the negative electrode (particularly the negative electrode active material) of the non-aqueous electrolyte secondary battery precursor.

[0226] The charging and discharging process preferably involves performing a combination of charging and discharging one or more times on the non-aqueous electrolyte secondary battery precursor in an environment of 25°C to 70°C.

[0227] The following are examples of the embodiments of this disclosure, but this disclosure is not limited to these embodiments. Hereinafter, "%" refers to "mass%" unless otherwise specified.

[0228] [Example 1] <Preparation of Non-Aqueous Electrolyte> Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed as non-aqueous solvents to obtain a mixed solvent. The volume ratio (EC:DEC) was 30:70. LiPF was added to the obtained mixed solvent as the electrolyte. ６ The electrolyte was dissolved in the final non-aqueous electrolyte solution at a concentration of 1.0 mol / L. The following additives were added to the resulting solution to obtain a non-aqueous electrolyte solution. A vinylene carbonate (VC) represented by the following formula (VII-1) was added in an amount of 1.0% by mass relative to the total mass of the non-aqueous electrolyte solution, and a sulfate ester represented by the following formula (X-3) was added in an amount of 1.0% by mass relative to the total mass of the non-aqueous electrolyte solution. The vinylene carbonate (VC) represented by formula (VII-1) is an example of compound (VII). The sulfate ester represented by formula (X-3) is an example of compound (X).

[0229]

[0230] <Fabrication of the positive electrode> LiNi as the positive electrode active material ０．７８０ Co ０．１９５ Al ０．０２５ O ２ (NCA, 98 parts by mass, median diameter (D) ５０ A paste-like cathode composite slurry was prepared by kneading together acetylene black (1.5 parts by mass) as a conductive additive, single-walled carbon nanotubes (0.5 parts by mass, composition: bundled single-walled CNT aggregate, average outer diameter per single-walled CNT: 2 nm, average length per single-walled CNT: over 5 μm, ratio (G / D): 80-150) as a conductive additive and molding aid, and N-methylpyrrolidinone as a solvent. Next, this cathode composite slurry was applied to a strip of aluminum foil (cathode current collector) with a thickness of 20 μm, and the resulting coating was dried to obtain coated aluminum foil. Subsequently, a sheet-like cathode was obtained by compressing the coated aluminum foil with a roll press. The cathode consisted of a cathode current collector and a cathode composite layer. The coating density of the cathode composite layer was 20.4 mg / cm². ２ The packing density was 3.0 g / mL.

[0231] <Fabrication of the negative electrode> Natural graphite (99 parts by mass) as the negative electrode active material, median diameter (D ５０ A paste-like negative electrode mixture slurry was prepared by kneading together a 4.1 μm thick copper nanotube (0.5 parts by mass) as a slurry thickener, 0.5 parts by mass (composition: bundled single-walled carbon nanotube aggregate, average outer diameter per single-walled carbon nanotube: 2 nm, average length per single-walled carbon nanotube: over 5 μm, ratio (G / D): 80-150) as a conductive additive and molding aid, and an aqueous solvent. Next, this negative electrode mixture slurry was applied to a 10 μm thick strip of copper foil (negative electrode current collector), and the resulting coating was dried to obtain a coated copper foil. Subsequently, a sheet-like negative electrode was obtained by compressing the coated copper foil with a roll press. The negative electrode consisted of a negative electrode current collector and a negative electrode mixture layer. The coating density of the negative electrode mixture layer was 10.7 mg / cm². ２The packing density was 1.4 g / mL. The negative electrode composite layer did not contain a binder. That is, the binder content was 0% by mass relative to the total amount of the negative electrode composite layer.

[0232] <Preparation of the separator> A microporous polyethylene film with a thickness of 13 μm was prepared as the separator.

[0233] <Preparation of a Non-Aqueous Electrolyte Secondary Battery Precursor> The aforementioned sheet-like negative electrode was punched out into a rectangular shape measuring 15 mm in length and 21 mm in width to obtain a rectangular negative electrode. The aforementioned sheet-like positive electrode was punched out into a rectangular shape measuring 14 mm in length and 20 mm in width to obtain a rectangular positive electrode. The aforementioned separator was punched out into a rectangular shape measuring 20 mm in length and 25 mm in width to obtain a rectangular separator. The rectangular negative electrode, rectangular separator, and rectangular positive electrode were laminated in this order inside a bag-shaped aluminum laminate (hereinafter also referred to as the "laminated bag"). Next, 200 μL of non-aqueous electrolyte was injected into the laminate bag, impregnating the rectangular separator, rectangular positive electrode, and rectangular negative electrode. Then, the battery was sealed by closing the opening of the laminate bag with a heat sealer. As a result, a laminate-type non-aqueous electrolyte secondary battery was obtained.

[0234] <Preparation of Non-Aqueous Electrolyte Secondary Battery (Charging and Discharging of Non-Aqueous Electrolyte Secondary Battery Precursor)> The above non-aqueous electrolyte secondary battery precursor was charged with CC (Constant Current) at a temperature of 25°C and a current of 0.05C for 5 hours. Then, a portion of the laminate bag was cut and the gas was released. After sealing the cut portion, it was left to stand at 25°C for 48 hours. Finally, a non-aqueous electrolyte secondary battery was obtained by repeating CC-CV (Constant Current-Constant Voltage) charging to 4.0V and CC discharge to 2.7V three times at a current of 0.1C.

[0235] <High-Temperature Charge-Discharge Cycle Test> The above non-aqueous electrolyte secondary battery was charged to 4.0V using CC-CV charging at a temperature of 50°C with a current of 0.5C, and then discharged to 2.7V using CC charging. The discharge capacity at this time was defined as the "initial capacity". The same procedure was repeated 500 times. Using the discharge capacity at the 500th cycle (hereinafter also referred to as the "discharge capacity after high-temperature cycling"), the capacity retention rate after the high-temperature cycling test was calculated using the following formula. The results are shown in Table 1.

[0236] <Capacity retention rate after high-temperature cycle test> Capacity retention rate after high-temperature cycle test (%) = [(Discharge capacity after high-temperature cycle) / (Initial capacity)] × 100

[0237] The acceptable range for capacity retention after high-temperature cycling tests is over 72%.

[0238] [Examples 2-10, Comparative Example 1] The same procedure as in Example 1 was followed, except that the type and content of the additives used in the preparation of the non-aqueous electrolyte were changed as shown in Table 1. The results are shown in Table 1. The additives shown in Table 1 are lithium difluorophosphate (LiPO) represented by the following formula (I-1) ２ F ２ ), lithium bis(oxalato)borate (LiBOB) represented by the following formula (II-1), lithium fluorosulfonate (LiSO) represented by the following formula (V-1) ３ F) vinylene carbonate (VC) represented by the following formula (VII-1), and sulfate ester represented by the following formula (X-3).

[0239]

[0240]

[0241] In Table 1, "Capacity Retention Rate" indicates the capacity retention rate after high-temperature cycling tests.

[0242] The non-aqueous electrolytes of Examples 1 to 10 were non-aqueous electrolytes for non-aqueous electrolyte secondary batteries equipped with a negative electrode. The negative electrode had a current collector and a negative electrode composite layer formed on the current collector. The negative electrode composite layer contained a negative electrode active material. The negative electrode composite layer satisfied (a). That is, the negative electrode composite layer did not contain a binder. The non-aqueous electrolyte contained additives. The total content of additives was 2.0% by mass or more of the total amount of the non-aqueous electrolyte. As a result, the capacity retention rate after high-temperature cycle testing of Examples 1 to 10 was over 72%. As a result, it was found that the non-aqueous electrolytes of Examples 1 to 10 are "non-aqueous electrolytes that can improve the capacity retention rate after high-temperature charge-discharge cycle testing in secondary batteries equipped with a negative electrode with a low binder content."

[0243] The disclosure of Japanese Patent Application No. 2025-050689, filed on 25 March 2025, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. A non-aqueous electrolyte for a secondary battery having a negative electrode, wherein the negative electrode comprises a current collector and a negative electrode composite layer formed on the current collector, the negative electrode composite layer contains a negative electrode active material, the negative electrode composite layer satisfies either (a) or (b) below, the non-aqueous electrolyte contains an additive, and the total content of the additive is 2.0% by mass or more with respect to the total amount of the non-aqueous electrolyte. (a) The negative electrode composite layer does not contain a binder. (b) The negative electrode composite layer further contains a binder, and the content of the binder is greater than 0% by mass and 0.5% by mass or less with respect to the total amount of the negative electrode composite layer.

2. The non-aqueous electrolyte according to claim 1, wherein the additive comprises at least one selected from the group consisting of a compound represented by the following formula (I-1), a compound represented by the following formula (I-2), a compound represented by the following formula (II), a compound represented by the following formula (III), a compound represented by the following formula (IV), a compound represented by the following formula (V), a compound represented by the following formula (VI), a compound represented by the following formula (VII), a compound represented by the following formula (VIII), a compound represented by the following formula (IX-1), a compound represented by the following formula (IX-2), a compound represented by the following formula (X), and a compound represented by the following formula (XI). (In formula (I-1), M ＋ represents an alkali metal ion, ammonium ion, imidazolium ion, pyridinium ion, pyrrolidinium ion, piperidinium ion, or phosphonium ion. In formula (I-2), two M ＋ Each of these independently represents an alkali metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion. In formula (II), Q represents a boron atom (B) or a phosphorus atom (P). ２１ Each independently represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain a single bond (-) or at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent. Each independently represents a halogen group. When Q is a boron atom (B), a represents 1 or 2, when a is 1, b represents 2, and when a is 2, b represents 0. When Q is a phosphorus atom (P), a represents an integer from 1 to 3, when a is 1, b represents 4, when a is 2, b represents 2, and when a is 3, b represents 0. c represents an integer from 1 to 3. M ＋ Each of these independently represents an alkali metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion. In formula (III), the two Rs ３１ each independently represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may optionally contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms containing a fluoro group (-F) as a substituent. M ＋ represents an alkali metal ion, an alkaline earth metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion. In formula (IV), R ４１ represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may optionally contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms containing a fluoro group (-F) as a substituent. R ４２ represents a hydrocarbon group having 1 to 12 carbon atoms which may optionally contain at least one functional group selected from the group consisting of a fluoro group (-F) and an oxa group (-O-) as a substituent, or a fluorocarbon group having 1 to 12 carbon atoms which may optionally contain an oxa group (-O-) as a substituent. M ＋ represents an alkali metal ion, an alkaline earth metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion. In formula (V), R ５１ represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may optionally contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms containing a fluoro group (-F) as a substituent. M ＋ represents an alkali metal ion, an alkaline earth metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion. In formula (VI), R ６１ each independently represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may optionally contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms containing a fluoro group (-F) as a substituent. i represents an integer of 1 to 4. In formula (VII), R ７１ Each independently represents a fluoro group (-F), a fluorine carbide group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of a fluoro group and an oxa group (-O-). j represents an integer from 0 to 2. In formula (VIII), the double line (solid and dotted) represents a single bond (-) or a double bond (=). R ８１ Each independently represents a fluoro group (-F), a fluorine carbide group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of a fluoro group and an oxa group (-O-). k represents an integer from 0 to 4. In formula (IX-1), R ９１ and R ９２ These can be independently substituted with a halogen group, an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ R represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain at least one functional group selected from the group consisting of ). ９１ The substituents are a halogen group, an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ Represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain at least one functional group selected from the group consisting of ). ９３ These can be independently substituted with a halogen group, a cyano group (-CN), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O)). ２ This represents a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of ). １０１ is a methylene group (-CH ２ -), ethylene group (-CH ２ CH ２ -), or n-propylene group (-CH ２ CH ２ CH ２ Represents (-). １０２ Each of these independently represents a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (x-3), a group represented by formula (x-4), a group represented by formula (x-5), a group represented by formula (x-6), a group represented by formula (x-7), or a group represented by formula (x-8), which may each contain at least one functional group selected from the group consisting of a halogen group (-X) and an oxa group (-O-) as a substituent. １０１ is a methylene group (-CH ２ When -, m represents an integer between 0 and 2. １０１ is an ethylene group (-CH ２ CH ２ When -, m represents an integer from 0 to 4. １０１ is an n-propylene group (-CH ２ CH ２ CH ２ When -, m represents an integer from 0 to 6. In equation (XI), the two R １１１ Each of these independently represents a hydrocarbon group having 1 to 12 carbon atoms or a trialkylsilyl group having 3 to 18 carbon atoms.

3. The negative electrode active material has a median diameter (D ５０ The non-aqueous electrolyte according to claim 1, comprising graphite particles of 10 μm or less.

4. The non-aqueous electrolyte according to claim 1, wherein the negative electrode composite layer contains a conductive additive, and the conductive additive contains carbon nanotubes.

5. The non-aqueous electrolyte according to claim 4, wherein the conductive additive consists of carbon nanotubes, and the content of the carbon nanotubes is 0.5% by mass or less relative to the total amount of the negative electrode composite layer.

6. The non-aqueous electrolyte according to claim 1, wherein the negative electrode composite layer contains a conductive additive different from carbon nanotubes, and the content of the conductive additive is 0.5% by mass or less relative to the total amount of the negative electrode composite layer.

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