CN113498562A

CN113498562A - Electrolyte solution, electrochemical device, and electronic device

Info

Publication number: CN113498562A
Application number: CN202080016641.XA
Authority: CN
Inventors: 彭谢学; 郑建明; 唐超
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2020-11-03
Filing date: 2020-11-03
Publication date: 2021-10-12
Also published as: WO2022094770A1

Abstract

An electrolyte, an electrochemical device containing the electrolyte, and an electronic device containing the electrochemical device. The electrolyte includes a compound represented by formula (I-A); in the formula (I-A), R¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R¹⁶、R¹⁷、R¹⁸Each independently represents the presence or absence; when it indicates the presence, R¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R¹⁶、R¹⁷、R¹⁸Each independently selected from substituted or unsubstituted C₁‑C₁₀Alkylene, substituted or unsubstituted C₂‑C₁₀Alkenylene, substituted or unsubstituted C₂‑C₁₀Alkynylene, substituted or unsubstituted C₃‑C₁₀Alkenylene, substituted or unsubstituted C₆‑C₁₀Arylene, substitutedOr unsubstituted C₃‑C₁₀Any one of alicyclic hydrocarbon groups, and, when substituted, the substituent group includes at least one of halogen and cyano; m and n are each independently selected from integers of 0 to 2. The electrolyte is suitable for an electrochemical device and can improve the high-temperature storage performance, the cycle performance and the floating charge performance of the electrochemical device.

Description

Electrolyte solution, electrochemical device, and electronic device

Technical Field

The present application relates to an electrolyte, an electrochemical device, and an electronic device.

Background

Electrochemical devices, such as lithium ion batteries, have been receiving much attention due to their characteristics of high energy density, high power density, and stable service life, and thus are widely used. With the rapid development of technology, the diversity of market demands, and the rise of energy storage systems and electric automobile industries in the coming years, more demands are made on lithium ion batteries, such as thinner, lighter, more diversified shapes, higher safety, higher energy density, and the like.

Disclosure of Invention

In some embodiments, the present application provides an electrolyte comprising a compound represented in formula (I-a);

in the formula (I-A),

R¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R¹⁶、R¹⁷、R¹⁸each independently represents the presence or absence; when it indicates the presence, R¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R¹⁶、R¹⁷、R¹⁸Each independently selected from substituted or unsubstituted C₁-C₁₀Alkylene, substituted or unsubstituted C₂-C₁₀Alkenylene, substituted or unsubstituted C₂-C₁₀Alkynylene, substituted or unsubstituted C₃-C₁₀Alkenylene, substituted or unsubstituted C₆-C₁₀An arylene group,Substituted or unsubstituted C₃-C₁₀Any one of alicyclic hydrocarbon groups, and, when substituted, the substituent group includes at least one of halogen and cyano;

m and n are each independently selected from integers of 0 to 2.

In some embodiments, the compound represented by formula (I-A) includes at least one of the compounds represented by formula (I-1) to formula (I-20);

in some embodiments, the compound represented by formula (I-a) is present in an amount of 0.01% to 10% by mass, based on the mass of the electrolyte.

In some embodiments, the electrolyte further includes a sulfur oxygen double bond-containing compound including at least one of compounds represented by formula (II-a) and formula (II-B);

in the formulae (II-A) and (II-B),

R²¹、R²²、R²³and R²⁴Each independently selected from substituted or unsubstituted C₁-C₅Alkyl, substituted or unsubstituted C₂-C₁₀Alkenyl, substituted or unsubstituted C₂-C₁₀Alkynyl, substituted or unsubstituted C₃-C₁₀Alicyclic hydrocarbon group, substituted or unsubstituted C₆-C₁₀Aryl, substituted or unsubstituted C₁-C₆Any one of the heteroatom-containing groups, and, when substituted, the substituent comprises at least one of a halogen and a heteroatom-containing group, the heteroatomComprises at least one of O, S, P, N, Si and B, wherein R²¹And R²²Can be bonded to form a ring structure, R²³And R²⁴Can be bonded to form a ring structure.

In some embodiments, the compound containing a thiooxy double bond includes at least one of the compounds represented by formula (II-1) to formula (II-60);

in some embodiments, the sulfur oxygen double bond-containing compound is present in an amount of not more than 5% by mass based on the mass of the electrolyte.

In some embodiments, the electrolyte further comprises a boron-containing lithium salt compound.

In some embodiments, the boron-containing lithium salt compound comprises at least one of lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis-oxalate borate.

In some embodiments, the boron-containing lithium salt compound is present in an amount of 0.01 to 1% by mass, based on the mass of the electrolyte.

In some embodiments, the electrolyte further comprises at least one of a dinitrile compound, a trinitrile compound.

In some embodiments, the dinitrile compound comprises at least one of the following compounds:

the trinitrile compound comprises at least one of the following compounds:

in some embodiments, the sum of the mass percentages of the dinitrile compound and the trinitrile compound is 0.5% to 10% based on the mass of the electrolyte.

In some embodiments, the compound represented by formula (I-a) is present in an amount of a% by mass based on the mass of the electrolyte; the sum of the mass percentage contents of the dinitrile compound and the trinitrile compound is b% based on the mass of the electrolyte; wherein a/b between a and b is more than or equal to 0.1 and less than or equal to 1.

In some embodiments, the electrolyte further includes a lithium phosphate salt compound including at least one of lithium difluorophosphate, lithium difluorobis-oxalate phosphate, lithium tetrafluoro-oxalate phosphate.

In some embodiments, the lithium phosphate salt compound is present in an amount of 0.01% to 2% by mass, based on the mass of the electrolyte.

In some embodiments, the present application also provides an electrochemical device comprising a positive electrode sheet, a negative electrode sheet, a separator, and the above electrolyte.

In some embodiments, the present application also provides an electronic device comprising the electrochemical device described above.

Detailed Description

It is to be understood that the disclosed embodiments are merely exemplary of the application that may be embodied in various forms and that, therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present application.

In the description of the present application, unless otherwise expressly specified or limited, the terms "first", "second", "third", "fourth", "fifth", "sixth", "formula (I-a)", "formula (II-B)", "formula (III-a)" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or existence of relationship to each other.

In the description of the present application, unless otherwise indicated, the functional groups of all compounds may be substituted or unsubstituted.

In the description of this application, the term "heteroatom" means an atom other than C, H. In some embodiments, the heteroatom comprises at least one of B, N, O, Si, P, S.

In the description of the present application, the term "heteroatom-containing group" refers to a functional group that contains at least one heteroatom. In some embodiments, the heteroatom-containing group comprises at least one of an alkoxy group, a sulfonate group.

In the description of the present application, the term "alkylene" refers to a divalent alkyl group, the term "alkenylene" refers to a divalent alkenyl group, the term "alkynylene" refers to a divalent alkynyl group, and the term "arylene" refers to a divalent aryl group.

In the description of this application, the term "alkenyl" denotes a group in which two alkenyl groups share the same carbon. In some embodiments, the alkenylene group is a divalent group of the formula-CH ═ C ═ CH-.

In the description of the present application, the term "alicyclic hydrocarbon group" means a cyclic hydrocarbon having aliphatic properties, and containing a closed carbon ring in the molecule. In the description of the present application, the term "alicyclic hydrocarbon group" means a divalent alicyclic hydrocarbon group.

(electrolyte)

[ first additive ]

In some embodiments, the electrolyte comprises a first additive comprising a compound represented by formula (I-a);

in the formula (I-A),

R¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R¹⁶、R¹⁷、R¹⁸each independently represents the presence or absence; when it indicates the presence, R¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R¹⁶、R¹⁷、R¹⁸Each independently selected from substituted or unsubstituted C₁-C₁₀Alkylene, substituted or unsubstituted C₂-C₁₀Alkenylene, substituted or unsubstituted C₂-C₁₀Alkynylene, substituted or unsubstituted C₃-C₁₀Alkenylene, substituted or unsubstituted C₆-C₁₀Arylene, substituted or unsubstituted C₃-C₁₀Any one of alicyclic hydrocarbon groups, and, when substituted, the substituent group includes at least one of halogen and cyano;

m and n are each independently selected from integers of 0 to 2.

The main way to increase the energy density of the electrochemical device may be to increase the charging voltage of the electrochemical device or to increase the capacity of active materials in the electrochemical device. However, these methods tend to accelerate the decomposition of the electrolyte in the electrochemical device. In addition, increasing the charging voltage of the electrochemical device also causes oxygen release from the positive electrode of the electrochemical device, further accelerating the decomposition of the electrolyte in the electrochemical device and causing gas evolution.

The compound containing the formula (I-A) is added into the electrolyte, so that the high-temperature storage performance, the cycle performance and the floating charge performance of the electrochemical device can be remarkably improved. After the electrochemical device is fully charged, the electrochemical device is continuously charged, so that the electrochemical device is in a fully charged state for a long time, and the phenomenon is referred to as floating charge; the float-charge performance of an electrochemical device can directly affect its reliability, e.g., gassing, excessive thickness, and capacity fade. The compound represented by the formula (I-A) can stabilize transition metal in a high valence state in the positive plate, can be oxidized to form a film on the surface of the positive plate, relieves electrolyte decomposition caused by oxygen release, reduces gas generation of an electrochemical device, has a high reduction potential, can form a film on a negative electrode, and is favorable for improving the stability of the negative electrode. Therefore, the addition of the compound comprising formula (I-a) to the electrolyte can improve the high-temperature storage performance, the cycle performance, and the float charge performance of the electrochemical device, contributing to the achievement of further enhancement of the energy density of the electrochemical device in a high charge state.

In some embodiments, the compound represented by formula (I-A) comprises at least one of the compounds represented by formulae (I-1) to (I-20);

in some embodiments, the compound represented by formula (I-a) is present in an amount of 0.01% to 10% by mass, based on the mass of the electrolyte. When the mass percentage of the first additive is within the above range, the high-temperature storage performance, the cycle performance, and the float charge performance of the electrochemical device can be further improved. In some embodiments, the compound represented by formula (I-a) is present in an amount of 0.1% to 7% by mass based on the mass of the electrolyte. In some embodiments, the compound represented by formula (I-a) is present in an amount of 1% to 4% by mass based on the mass of the electrolyte.

[ second additive ]

In some embodiments, the electrolyte further comprises a second additive comprising a sulfoxidipine-containing compound comprising at least one of compounds represented by formula (II-a) and formula (II-B);

in the formulae (II-A) and (II-B),

R²¹、R²²、R²³and R²⁴Each independently selected from substituted or unsubstituted C₁-C₅Alkyl, substituted or unsubstituted C₂-C₁₀Alkenyl, substituted or unsubstituted C₂-C₁₀Alkynyl, substituted or unsubstituted C₃-C₁₀Alicyclic hydrocarbon group, substituted or unsubstituted C₆-C₁₀Aryl, substituted or unsubstituted C₁-C₆And, when substituted, the substituent comprises at least one of a halogen and a heteroatom-containing group, including at least one of O, S, P, N, Si, B, wherein R²¹And R²²Can be bonded to form a ring structure, R²³And R²⁴Can be bonded to form a ring structure.

When the first additive and the second additive are simultaneously added to the electrolyte, the high-temperature storage performance, the cycle performance, and the float charge performance of the electrochemical device can be further improved. The probable reason is that the sulfur-containing oxygen-bis-building compound has strong oxidation resistance, is not easy to be oxidized on the surface of the positive electrode, and can be reduced on the surface of the metal lithium under the condition of lithium precipitation of the anode to form a protective film to inhibit the decomposition and heat generation of the metal lithium and the electrolyte. Therefore, when the second additive is used together with the first additive, it is possible to further suppress decomposition of the electrolyte and enhance protection of the positive and negative electrode active materials, thereby further improving the high-temperature storage performance, the cycle performance, and the float charge performance of the electrochemical device.

In some embodiments, the sulfoxidime containing compound comprises at least one of the compounds represented by formulas (II-1) to (II-60);

in some embodiments, the sulfur oxygen double bond-containing compound is present in an amount of no greater than 5% by mass, based on the mass of the electrolyte. When the mass percentage of the second additive is within the above range, the high-temperature storage performance, the cycle performance, and the float charge performance of the electrochemical device can be further improved. In some embodiments, the sulfur oxygen double bond-containing compound is present in an amount of 0.5 to 3.5% by mass based on the mass of the electrolyte.

In some embodiments, the compound containing a thiooxy double bond comprises at least one of a compound represented by formula (II-12) and a compound represented by formula (II-23); and the sum of the mass percentages of the compound represented by formula (II-12) and the compound represented by formula (II-23) is not more than 5% based on the mass of the electrolyte. When the sum of the mass percentages of the compound represented by formula (II-12) and the compound represented by formula (II-23) satisfies the above range, the high-temperature storage performance, the cycle performance, and the float charge performance of the electrochemical device can be further improved.

[ third additive ]

In some embodiments, the electrolyte further comprises a third additive comprising a boron-containing lithium salt compound. In some embodiments, the boron-containing lithium salt compound comprises lithium tetrafluoroborate (LiBF)₄) Lithium difluoroborate (LiDFOB) and lithium bis (oxalato) borate (LiBOB).

When the first additive and the third additive are simultaneously added to the electrolyte, the high-temperature storage performance, the cycle performance, and the float charge performance of the electrochemical device can be further improved. Possible reasons are boron-containing lithium salt compounds, such as lithium tetrafluoroborate (LiBF)₄) Lithium difluorooxalato borate (LiDFOB) and lithium bis (oxalato) borate (LiBOB) can form a film on the surface of the negative electrode, and when the lithium difluorooxalato borate (LiDFOB) and the lithium bis (oxalato) borate (LiBOB) are used together with the first additive, the decomposition of the electrolyte can be further inhibited, the gas generation of an electrochemical device can be reduced, and the electrochemical device can be further improvedHigh temperature storage performance and cycle performance of the device.

In some embodiments, the boron-containing lithium salt compound comprises lithium tetrafluoroborate (LiBF)₄) And lithium difluoroborate (LiDFOB). The thermal stability of lithium tetrafluoroborate and lithium difluorooxalato borate is higher than that of lithium hexafluorophosphate, a fluorine-containing protective film can be better formed on the surface of the negative electrode, and the reaction between the lithium hexafluorophosphate and the negative electrode is reduced, so that the generation of gas is inhibited, and the high-temperature performance of the battery is further improved.

In some embodiments, the boron-containing lithium salt compound is present in an amount of 0.01 to 1% by mass, based on the mass of the electrolyte. When the mass percentage of the third additive is within the above range, the high-temperature storage performance, the cycle performance, and the float charge performance of the electrochemical device can be further improved. In some embodiments, the boron-containing lithium salt compound is present in an amount of 0.1% to 1% by mass, based on the mass of the electrolyte.

[ fourth additive ]

In some embodiments, the electrolyte further comprises a fourth additive, the fourth additive comprising at least one of a dinitrile compound, a dinitrile compound.

When the first additive and the fourth additive are added into the electrolyte at the same time, the high-temperature storage performance and the floating charge performance of the electrochemical device can be further improved, and the balance between the performance and the cost of the electrochemical device is realized.

In some embodiments, the dinitrile compound, and the dinitrile compound may be substituted, and, when substituted, the substituent is halogen. In some embodiments, the halogen may be fluorine.

the trinitrile compound comprises at least one of the following compounds:

in some embodiments, the sum of the mass percentages of the dinitrile compound and the trinitrile compound is 0.5% to 10% based on the mass of the electrolyte. When the mass percentage of the fourth additive is within the above range, the high-temperature storage performance and the float charge performance of the electrochemical device can be further improved. In some embodiments, the sum of the mass percentages of the dinitrile compound and the trinitrile compound is 0.5% to 8% based on the mass of the electrolyte.

In some embodiments, the compound represented by formula (I-a) is present in an amount of a% by mass based on the mass of the electrolyte; the sum of the mass percentage contents of the dinitrile compound and the trinitrile compound is b% based on the mass of the electrolyte; wherein a/b between a and b is more than or equal to 0.1 and less than or equal to 1. When the weight ratio of the first additive to the fourth additive satisfies the above range, the high-temperature storage performance and the float charge performance of the electrochemical device can be further improved while taking into account the kinetic performance. If the weight ratio of the first additive to the fourth additive exceeds 1, the relative content of the formula (I-A) is too high, so that the viscosity is too high, the dynamics are influenced, the cost is too high, and the effect cannot be realized if the relative content of the formula (I-A) is too low.

[ fifth additive ]

In some embodiments, the electrolyte further comprises a fifth additive comprising a lithium phosphate salt compound comprising lithium difluorophosphate (LiPO)₂F₂) Lithium difluorobis (oxalato) phosphate (LiDFOP), and lithium tetrafluoro (oxalato) phosphate (LiTFOP).

When the first additive and the fifth additive are simultaneously added to the electrolyte, the high-temperature storage performance and the float charge performance of the electrochemical device can be further improved. The reason is that the lithium phosphate salt compound is capable of forming a film at the cathode, and when used together with the first additive, the decomposition of the electrolyte can be further suppressed, thereby further improving the high-temperature storage performance and the float charge performance of the electrochemical device.

In some embodiments, the lithium phosphate-containing compound is present in an amount of 0.01 to 2% by mass, based on the mass of the electrolyte. When the mass percentage of the fifth additive is within the above range, the high-temperature storage performance and the float charge performance of the electrochemical device can be further improved. In some embodiments, the lithium phosphate-containing compound is present in an amount of 0.1 to 1% by mass, based on the mass of the electrolyte.

[ sixth additive ]

In some embodiments, the electrolyte further includes a sixth additive including at least one of a cyclic carbonate-based compound, a fluorine-substituted carbonate-based compound, and an unsaturated carbonate-based compound.

In some embodiments, the cyclic carbonate-based compound comprises a compound represented by formula (III-a);

in the formula (III-A),

R³selected from substituted or unsubstituted C₁-C₆Alkylene, substituted or unsubstituted C₂-C₆Any one of alkenylene, and, when substituted, the substituent comprises halogen, C₁-C₆Alkyl radical, C₂-C₆At least one alkenyl group.

When the cyclic carbonate compound is added into the electrolyte, the stability and flexibility of SEI film formation can be further enhanced in an auxiliary manner, so that the protective effect of the active material is further increased, the interface contact probability of the active material and the electrolyte is reduced, and the impedance increase caused by byproduct accumulation in the circulation process is improved.

In some embodiments, the compound represented by formula (III-A) comprises at least one of the compounds represented by formulae (III-1) to (III-12);

in some embodiments, the cyclic carbonate compound is present in an amount of 0.01 to 30% by mass, based on the mass of the electrolyte. In some embodiments, the cyclic carbonate compound is present in an amount of 0.1 to 10% by mass, based on the mass of the electrolyte.

[ organic solvent ]

In some embodiments, the electrolyte further comprises an organic solvent. The organic solvent is an organic solvent known in the art to be suitable for an electrochemical device, and for example, a nonaqueous organic solvent is generally used.

In some embodiments, the non-aqueous organic solvent is a carbonate, a carboxylate, an ether, a sulfone, or other aprotic solvent. In some embodiments, the carbonate-based non-aqueous organic solvent comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, bis (2,2, 2-trifluoroethyl) carbonate. In some embodiments, the non-aqueous organic solvent of the carboxylate ester type comprises methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, γ -butyrolactone, 2-difluoroethyl acetate, valerolactone, butyrolactone, 2-fluoroacetic acid ethyl ester, 2-difluoroacetic acid ethyl ester, trifluoroacetic acid ethyl ester, 2,3,3, 3-pentafluoropropionic acid ethyl ester, 2,3,3,4,4, 4-heptafluorobutyric acid methyl ester, 4,4, 4-trifluoro-3- (trifluoromethyl) butyric acid methyl ester, 2,3,3,4,4,5,5,5, 5-nonafluoropentanoic acid ethyl ester, 2,3,3,4,4,5,5,6,6,7,7,8,8,9,9, 9-heptadecafluorononanoic acid methyl ester, 2,3,3,4,4,5,5,6,6,7,7,8,8,9,9, 9-heptadecafluorononanoic acid ethyl ester. In some embodiments, the ether non-aqueous organic solvent comprises ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dibutyl ether, bis (2-fluoroethyl) ether, bis (2, 2-difluoroethyl) ether, bis (2,2, 2-trifluoroethyl) ether, ethyl (2-fluoroethyl) ether, ethyl (2,2, 2-trifluoroethyl) ether, ethyl (1,1,2, 2-tetrafluoroethyl) ether, (2-fluoroethyl) (2,2, 2-trifluoroethyl) ether, (2-fluoroethyl) (1,1,2, 2-tetrafluoroethyl) ether, (2,2, 2-trifluoroethyl) (1,1,2, 2-tetrafluoroethyl) ether, ethyl-n-propyl ether, ethyl (3-fluoron-propyl) ether, ethyl (3,3, 3-trifluoro-n-propyl) ether, Ethyl (2,2,3, 3-tetrafluoro-n-propyl) ether, ethyl (2,2,3,3, 3-pentafluoro-n-propyl) ether, 2-fluoroethyl-n-propyl ether, (2-fluoroethyl) (3-fluoro-n-propyl) ether, (2-fluoroethyl) (3,3, 3-trifluoro-n-propyl) ether, (2-fluoroethyl) (2,2,3, 3-tetrafluoro-n-propyl) ether, (2-fluoroethyl) (2,2,3,3, 3-pentafluoro-n-propyl) ether, 2,2, 2-trifluoroethyl-n-propyl ether, (2,2, 2-trifluoroethyl) (3-fluoro-n-propyl) ether, (2,2, 2-trifluoroethyl) (3,3, 3-trifluoro-n-propyl) ether, (2,2, 2-trifluoroethyl) (2,2,3, 3-tetrafluoro-n-propyl ether, (2,2, 2-trifluoroethyl) (2,2,3,3, 3-pentafluoro-n-propyl) ether, 1,1,2, 2-tetrafluoroethyl-n-propyl ether, (1,1,2, 2-tetrafluoroethyl) (3-fluoro-n-propyl) ether, (1, l,2, 2-tetrafluoroethyl) (3,3, 3-trifluoro-n-propyl) ether, (1,1,2, 2-tetrafluoroethyl) (2,2,3, 3-tetrafluoro-n-propyl) ether, (1,1,2, 2-tetrafluoroethyl) (2,2,3,3, 3-pentafluoro-n-propyl) ether, di-n-propyl ether, (n-propyl) (3-fluoro-n-propyl) ether, (n-propyl) (3,3, 3-trifluoro-n-propyl) ether, (n-propyl) (2,2,3, 3-tetrafluoro-n-propyl) ether, (n-propyl) (2,2,3,3, 3-pentafluoro-n-propyl) ether, bis (3-fluoro-n-propyl) ether, (3-fluoro-n-propyl) (3,3, 3-trifluoro-n-propyl) ether, (3-fluoro-n-propyl) (2,2,3, 3-tetrafluoro-n-propyl) ether, (3-fluoro-n-propyl) (2,2,3,3, 3-pentafluoro-n-propyl) ether, bis (3,3, 3-trifluoro-n-propyl) ether, (3,3, 3-trifluoro-n-propyl) (2,2,3, 3-tetrafluoro-n-propyl) ether, (3,3, 3-trifluoro-n-propyl) (2,2,3,3, 3-pentafluoro-n-propyl) ether, bis (2,2,3, 3-tetrafluoro-n-propyl) ether, (2,2,3, 3-tetrafluoro-n-propyl) (2,2,3,3, 3-pentafluoro-n-propyl) ether, bis (2,2,3,3, 3-pentafluoro-n-propyl) ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, methoxy (2-fluoroethoxy) methane, methoxy (2,2, 2-trifluoroethoxy) methane, methoxy (1,1,2, 2-tetrafluoroethoxy) methane, diethoxymethane, ethoxy (2-fluoroethoxy) methane, ethoxy (2,2, 2-trifluoroethoxy) methane, ethoxy (1,1,2, 2-tetrafluoroethoxy) methane, bis (2-fluoroethoxy) methane, (2-fluoroethoxy) (2,2, 2-trifluoroethoxy) methane, (2-fluoroethoxy) (1,1,2, 2-tetrafluoroethoxy) methane, Bis (2,2, 2-trifluoroethoxy) methane, (2,2, 2-trifluoroethoxy) (1,1,2, 2-tetrafluoroethoxy) methane, bis (1,1,2, 2-tetrafluoroethoxy) methane, dimethoxyethane, methoxyethoxyethane, methoxy (2-fluoroethoxy) ethane, methoxy (2,2, 2-trifluoroethoxy) ethane, methoxy (1,1,2, 2-tetrafluoroethoxy) ethane, diethoxyethane, ethoxy (2-fluoroethoxy) ethane, ethoxy (2,2, 2-trifluoroethoxy) ethane, ethoxy (1,1,2, 2-tetrafluoroethoxy) ethane, bis (2-fluoroethoxy) ethane, (2-fluoroethoxy) (2,2, 2-trifluoroethoxy) ethane, bis (2-fluoroethoxy) (2,2, 2-trifluoroethoxy) ethane, bis (2, 2-tetrafluoroethoxy) ethane, bis (2, 2-fluoroethoxy) ethane, bis (2, 2-tetrafluoroethoxy) ethane, bis (2, 2-fluoroethoxy) ethane, 2, 2-tetrafluoroethoxy) ethane, bis (2, 2-fluoroethoxy) ethane, bis (2,2, 2-tetrafluoroethoxy) ethane, bis (2,2, 2-fluoroethoxy) ethane, 2, 2-tetrafluoroethoxy) ethane, 2,2,2, and a mixture, At least one of (2-fluoroethoxy) (1,1,2, 2-tetrafluoroethoxy) ethane, bis (2,2, 2-trifluoroethoxy) ethane, (2,2, 2-trifluoroethoxy) (1,1,2, 2-tetrafluoroethoxy) ethane, bis (1,1,2, 2-tetrafluoroethoxy) ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether tetrahydrofuran, 2-methyltetrahydrofuran, and bis (2,2, 2-trifluoroethyl) ether. In some embodiments, the sulfone-based non-aqueous organic solvent comprises 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulful-ane, 3-fluorosulful-ane, 2-difluorosulfolane, 2, 3-difluorosulfolane, 2, 4-difluorosulfolane, 2, 5-difluorosulfolane, 3, 4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methylsulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, methyl-sulfolane, methyl-2-sulfolane, methyl-3-fluoro-3-methylsulfolane, 2-fluoro-methylsulfolane, 3-difluoromethylsulfone, 2-fluoro-3-methylsulfolane, 2-methylsulfolane, 3-difluoromethylsulfone, 2-fluoro-3-difluoromethylsulfone, 3-difluoromethylsulfone, 3-methylsulfolane, 3-methyl-sulfolane, 3-methyl-sulfolane, 3-methyl-sulfolane, 2-methyl-sulfolane, p, 2-fluoromethylsulphone, 3-fluoromethylsulphone, 2-difluoromethylsulphone, 3-difluoromethylsulphone, 2-trifluoromethylsulpholane, 3-trifluoromethylsulpholane, 2-fluoro-3- (trifluoromethyl) sulpholane, 3-fluoro-3- (trifluoromethyl) sulpholane, 4-fluoro-3- (trifluoromethyl) sulpholane, 5-fluoro-3- (trifluoromethyl) sulpholane, dimethylsulphone, ethylmethylsulphone, diethylsulphone, n-propylmethylsulphone, n-propylethylsulphone, di-n-propylsulphone, isopropylmethylsulphone, isopropylethylsulphone, diisopropylsulphone, n-butylmethylsulphone, n-butylethylsulphone, tert-butylmethylsulphone, tert-butylethylsulphone, monofluoromethylsulphone, difluoromethylsulphone, At least one of trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, perfluoroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, bis (trifluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl n-propyl sulfone, difluoromethyl n-propyl sulfone, trifluoromethyl n-propyl sulfone, fluoromethyl isopropyl sulfone, difluoromethyl isopropyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl n-propyl sulfone, trifluoroethyl isopropyl sulfone, pentafluoroethyl n-propyl sulfone, pentafluoroethyl isopropyl sulfone, trifluoroethyl n-butyl sulfone, trifluoroethyl t-butyl sulfone, pentafluoroethyl n-butyl sulfone, pentafluoroethyl t-butyl sulfone.

The non-aqueous organic solvent may be used alone or in a mixture, and when used in a mixture, the ratio of the mixture may be controlled according to the desired performance of the electrochemical device.

In some embodiments, the non-aqueous organic solvent comprises at least one of Ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), dimethyl carbonate, ethyl acetate, Ethyl Propionate (EP), Propyl Propionate (PP), ethyl 2, 2-difluoroacetate, 2-difluoroethyl acetate, sulfolane.

[ electrolyte salt ]

In some embodiments, the electrolyte further comprises an electrolyte salt. The electrolyte salt is well known to those skilled in the art and is suitable for use in electrochemical devices, and may be selected for various electrochemical devices. For example, for lithium ion batteries, lithium salts are commonly used as electrolyte salts.

In some embodiments, the lithium salt comprises lithium hexafluorophosphate (LiPF)₆)。

In some embodiments, the molar concentration of lithium in the lithium salt is 0.5 to 3mol/L based on the total volume of the electrolyte. In some embodiments, the molar concentration of lithium in the lithium salt is 0.5 to 2mol/L based on the total volume of the electrolyte. In some embodiments, the molar concentration of lithium in the lithium salt is 0.8 to 1.5mol/L based on the total volume of the electrolyte.

(electrochemical device)

The electrochemical device of the present application is, for example, a primary battery, a secondary battery, a fuel cell, a solar cell, or a capacitor. The secondary battery is, for example, a lithium secondary battery including, but not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

In some embodiments, the electrochemical device is adapted for a charge cutoff voltage of not less than 4.2V.

In some embodiments, the electrochemical device comprises a positive electrode tab, a negative electrode tab, a separator, and an electrolyte as described herein before.

[ Positive electrode sheet ]

The positive electrode tab is a positive electrode tab known in the art that can be used in an electrochemical device. In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is disposed on a surface of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material.

In some embodiments, the structure of the positive electrode tab is a structure of a positive electrode tab that can be used in an electrochemical device, which is well known in the art.

In some embodiments, the positive current collector is a metal, such as, but not limited to, aluminum foil.

The positive electrode active material may be any conventionally known material capable of reversibly intercalating and deintercalating active ions, which is known in the art and can be used as a positive electrode active material for an electrochemical device.

In some embodiments, the positive active material includes at least one of a composite oxide of metals of lithium and cobalt, manganese, nickel, or a combination thereof. In some embodiments, the positive active material comprises LiCoO₂、LiNiO₂、LiMnO₂、LiMn₂O₄、Li(Ni_aCo_bMn_c)O₂(0<a<1，0<b<1，0<c<1，a+b+c＝1)、LiMn₂O₄LiNi_1-yCo_yO₂、LiCo_l-yMn_yO₂、LiNi_l- _yMn_yO₂(0<y<1)、Li(Ni_aMn_bCo_c)04(0<a<2，0<b<2，0<c<2，a+b+c＝2)、LiMn_2-zNi_zO₄、LiMn_2- _zCo_zO₄(0<z<2)、Li(Ni_aCo_bAl_c)O₂(0<a<1，0<b<1，0<c<1，a+b+c＝1)、LiCoPO₄、LiFePO₄At least one of (1). In some embodiments, the positive active material includes Li (Ni)_aCo_bMn_cM_1-a-b-c)O₂(a is more than or equal to 0 and less than or equal to 1, b is more than or equal to 0 and less than or equal to 1, c is more than or equal to 0 and less than or equal to 1, a + b + c is more than or equal to 0 and less than or equal to 1, and M is Mg, Al, Ti or the combination thereof). In some embodiments, the positive active material includes at least one of sulfide, selenide, and halide.

In some embodiments, the positive electrode active material has a coating layer that coats a surface of the positive electrode active material. In some embodiments, the positive active material is mixed with a positive active material having a coating layer. In some embodiments, the coating element compound in the coating layer comprises at least one of an oxide of the coating element, a hydroxide of the coating element, a oxyhydroxide of the coating element, an oxycarbonate (oxy carbonate) of the coating element, and a basic carbonate of the coating element. In some embodiments, the coating element compound in the coating layer is in an amorphous form or a crystalline form. In some embodiments, the cladding element in the cladding layer comprises Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. By using the coating element in the coating element compound, the coating layer can be formed in any method that does not adversely affect the properties of the positive electrode active material. The method of forming the coating layer may be any method known in the art including, but not limited to, spraying, dipping, and the like.

In some embodiments, the positive electrode active material layer further includes a binder and a conductive material. The binder is a binder known in the art to be used as a positive electrode active material layer. In some embodiments, the binder comprises at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy, nylon. The binder is used to improve the binding property between the positive electrode active material particles and the current collector. The conductive material is a conductive material known in the art that can be used as the positive electrode active material layer. In some embodiments, the conductive material comprises at least one of natural graphite, artificial graphite, conductive carbon black, acetylene black, ketjen black, carbon fiber, metal powder, metal fiber, polyphenylene derivative. In some embodiments, the metal powder comprises at least one of a metal powder of copper, nickel, aluminum, silver. In some embodiments, the metal fibers comprise at least one of metal fibers of copper, nickel, aluminum, silver. The conductive material is used to provide conductivity to the electrodes.

In some embodiments, the method for preparing the positive electrode sheet is a method for preparing a positive electrode sheet that can be used for an electrochemical device, which is well known in the art. In some embodiments, in the preparation of the positive electrode slurry, a solvent is generally added, and the positive electrode active material is dissolved or dispersed in the solvent after adding a binder and, if necessary, a conductive material and a thickener to prepare the positive electrode slurry. The solvent is evaporated during the drying process. The solvent is a solvent known in the art that can be used as the positive electrode active material layer, and is, for example, but not limited to, N-methylpyrrolidone (NMP).

The mixing ratio of the positive electrode active material, the binder, and the conductive material in the positive electrode active material layer is not particularly limited, and may be controlled according to the desired electrochemical device performance.

The application has no special limitation on the compaction density of the positive plate, and can be adjusted according to actual needs. In some embodiments, the positive electrode sheet has a low compacted density4.5g/cm or less³。

[ negative electrode sheet ]

The negative electrode tab is a negative electrode tab known in the art that may be used in an electrochemical device. In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is disposed on a surface of the negative electrode current collector. The negative electrode active material layer contains a negative electrode active material.

In some embodiments, the structure of the negative electrode sheet is a structure of a negative electrode sheet that may be used in an electrochemical device, as is well known in the art.

In some embodiments, the negative current collector is a metal such as, but not limited to, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or combinations thereof.

The negative electrode active material may be selected from a variety of conventionally known materials capable of reversibly intercalating and deintercalating active ions or a variety of conventionally known materials capable of reversibly doping and dedoping active ions, which are known in the art and can be used as a negative electrode active material for an electrochemical device.

In some embodiments, the negative active material comprises at least one of lithium metal, a lithium metal alloy, and a carbon material. In some embodiments, the lithium metal alloy comprises an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, Sn. The carbon material may be selected from various carbon materials known in the art to be used as a carbon-based negative electrode active material for an electrochemical device. In some embodiments, the carbon material comprises at least one of crystalline carbon, amorphous carbon. In some embodiments, the crystalline carbon is natural graphite or artificial graphite. In some embodiments, the crystalline carbon is amorphous, platy, platelet, spherical, or fibrous in shape. In some embodiments, the crystalline carbon is low crystalline carbon or high crystalline carbon. In some embodiments, the low crystalline carbon comprises at least one of soft carbon, hard carbon. In some embodiments, the highly crystalline carbon comprises natural graphite, crystalline graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microbeads, mesophase pitch, high temperature calcined carbonAt least one of (1). In some embodiments, the high temperature calcined carbon is petroleum or coke derived from coal tar pitch. In some embodiments, the amorphous carbon comprises at least one of soft carbon, hard carbon, mesophase pitch carbonization products, fired coke. In some embodiments, the negative active material comprises a transition metal oxide. In some embodiments, the transition metal oxide comprises at least one of vanadium oxide, lithium vanadium oxide. In some embodiments, the negative active material includes Si, SiOx (0)<x<2) Si/C composite, Si-Q alloy, Sn, SnO_zAt least one of Sn-C composite and Sn-R alloy, wherein Q is at least one of alkali metal, alkaline earth metal, elements from groups 13 to 16, transition element and rare earth element, Q is not Si, R is at least one of alkali metal, alkaline earth metal, elements from groups 13 to 16, transition element and rare earth element, and R is not Sn. In some embodiments, Q and R comprise at least one of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po. In some embodiments, SiOx (0)<x<2) Is a porous negative electrode active material. In some embodiments, the SiOx particles have an average particle size (D)₅₀) Is 1-20 μm. In some embodiments, the average diameter of pores in the SiOx particles is 30-500nm, as measured at the surface. In some embodiments, the SiOx particles have a specific surface area of 5 to 50m²(ii) in terms of/g. In some embodiments, the negative active material comprises SiOx (0)<x<2) And is selected from Li₂SiO₃、Li₄SiO₄At least one of (1). In some embodiments, in the Si/C composite, carbon (C) is not agglomerated and dispersed in bulk inside the Si particles, but is uniformly dispersed in an atomic state inside the Si particles. In some embodiments, in the Si/C composite, the molar ratio of C to Si satisfies: 0<C/Si<18. In some embodiments, the weight percent of C is 1 wt% to 50 wt% based on the total weight of the Si/C composite. In some embodiments, the average particle size of the Si/C composite particles is 10-100 μm.

In some embodiments, the negative active material layer further comprises a binder. The binder is a binder known in the art to be used as a negative electrode active material layer. In some embodiments, the binder is any binder polymer, such as, but not limited to, vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy, nylon. The binder is used to improve binding properties between the negative active material particles and the negative current collector.

In some embodiments, the negative electrode active material layer further includes a conductive material. The conductive material is a conductive material known in the art that can be used as the anode active material layer. In some embodiments, the conductive material is any conductive material that does not cause a chemical change, such as, but not limited to, carbon-based materials, such as, but not limited to, natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fibers, metal-based materials, such as, but not limited to, metal powders or metal fibers of copper, nickel, aluminum, silver, etc., conductive polymers, such as, but not limited to, polyphenylene derivatives. The conductive material is used to improve the conductivity of the negative electrode sheet.

In some embodiments, the method of preparing the negative electrode sheet is a method of preparing a negative electrode sheet that may be used for an electrochemical device, which is well known in the art. In some embodiments, in the preparation of the negative electrode slurry, a solvent is generally added, and the negative electrode active material is dissolved or dispersed in the solvent after adding a binder and, if necessary, a conductive material and a thickener to prepare the negative electrode slurry. The solvent is evaporated during the drying process. The solvent is a solvent known in the art, such as, but not limited to, water, which can be used as the negative electrode active material layer. The thickener is a thickener known in the art that can be used as the anode active material layer, and is, for example, but not limited to, sodium carboxymethyl cellulose.

The mixing ratio of the positive electrode active material, the binder, and the thickener in the negative electrode active material layer is not particularly limited, and may be controlled according to the desired electrochemical device performance.

The compaction density of the negative electrode plate is not particularly limited and can be adjusted according to actual needs.

[ isolation film ]

The separator is a separator known in the art that can be used for an electrochemical device, such as, but not limited to, polyolefin-based microporous membranes. In some embodiments, the barrier film comprises at least one of Polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-methyl methacrylate copolymer.

In some embodiments, the separator is a single layer separator or a multilayer separator.

In some embodiments, the polyolefin-based microporous membrane is coated with a coating. In some embodiments, the coating comprises at least one of an organic coating selected from at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyimide, acrylonitrile-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, polymethyl methacrylate, polymethyl acrylate, polyethylacrylate, acrylic acid-styrene copolymer, polydimethylsiloxane, sodium polyacrylate, sodium carboxymethylcellulose, and an inorganic coating selected from SiO, and the inorganic coating is selected from at least one of a polymer selected from the group consisting of polyvinyl chloride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyimide, acrylonitrile-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, polymethyl methacrylate, polymethyl acrylate, polyethylacrylate, acrylic acid-styrene copolymer, polydimethylsiloxane, sodium polyacrylate, and sodium carboxymethylcellulose₂、Al₂O₃、CaO、TiO₂、ZnO₂、MgO、ZrO₂、SnO₂At least one of them.

The form and thickness of the separator are not particularly limited. The method for preparing the separator is a method for preparing a separator that can be used in an electrochemical device, which is well known in the art.

[ outer packaging case ]

In some embodiments, the electrochemical device further comprises an overwrap housing. The outer packaging case is a well known outer packaging case in the art that can be used for electrochemical devices and is stable to the electrolyte used, such as, but not limited to, a metal-based outer packaging case.

(electronic device)

The electronic device of the present application is any electronic device such as, but not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a handy cleaner, a portable CD player, a mini disc, a transceiver, an electronic notebook, a calculator, a memory card, a portable recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large-sized household battery, and a lithium ion capacitor. Note that the electrochemical device of the present application is applicable to an energy storage power station, a marine vehicle, and an air vehicle, in addition to the above-exemplified electronic devices. The air transport carrier device comprises an air transport carrier device in the atmosphere and an air transport carrier device outside the atmosphere.

In some embodiments, the electronic device comprises an electrochemical device as described herein.

The present application is further illustrated below with reference to examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application.

In the following examples and comparative examples, reagents, materials and instruments used were commercially available or synthetically available, unless otherwise specified.

The specific reagents used in the electrolyte were as follows:

additive:

a first additive: 1,3,3,5, 7-Heptane Pentanitrile (I-2), 4, 6-tris (2-cyanoethyl) nonanedionitrile (I-6), 1,3,3,5, 7-Heptane hexanenitrile (I-14) nonane-1, 3,5,5,7, 9-hexanenitrile (I-16), 4' - (2, 2-bis (2-cyanoethyl) propane-1, 3-diyl) bis (heptanedionitrile) (I-17)

A second additive: 1. 3-propane sultone (II-12), vinyl sulfate (II-18) and 2, 4-butane sultone (II-23)

A third additive: lithium tetrafluoroborate (LiBF)₄) Lithium difluorooxalato borate (liddob);

a fourth additive: 1.2, 3-tris (2-cyanoethoxy) propane (TCEP), 1,3, 6-Hexanetricarbonitrile (HTCN), 1, 2-bis (2-cyanoethoxy) ethane (DENE), Adiponitrile (AND)

A fifth additive: lithium difluorophosphate (LiPO)₂F₂) Lithium tetrafluoro oxalate phosphate (litfo);

organic solvent: ethylene carbonate (abbreviated EC), propylene carbonate (abbreviated PC), diethyl carbonate (abbreviated DEC), ethyl propionate (abbreviated EP), propyl propionate (abbreviated PP), ethyl methyl carbonate (abbreviated EMC);

lithium salt: lithium hexafluorophosphate (LiPF)₆)。

Among them, the compound represented by the formula (I-A) in the present application is commercially available, or can be synthesized by a preparation method known and conventional in the art, or can also be synthesized by the following preparation method, taking the compound represented by the formula (I-16) as an example, and the specific synthesis steps are:

in a 50mL round bottom flask was added malononitrile (1.6g, 24.2mmol), t-butanol (20mL) and 1g Tritol B (40%), placed in an ice water bath to cool, then 2-methyleneglutaronitrile (5.0g, 47.2mmol) was added dropwise, the mixture was stirred at room temperature for 4 hours, filtered, and washed with ether. Recrystallization from acetone-methanol followed by chromatographic Separation (SiO)₂) The reaction mixture was washed with ethyl acetate EA/dichloromethane DCM (1: 3) eluting to obtain white solid productAbout 3.5 g.¹H NMR(400MHz,CD₃CN,ppm):δ3.12—3.19(m,2H,CH-CN),2.61—2.69(m,4H,CH₂CN),2.50—2.59(m,2H,CH₂),2.29—2.34(m,2H,CH₂),2.06—2.14(m,4H,CH₂CH₂CN),¹³C NMR(400MHz,CD₃CN,ppm):δ119.1,119.05,118.98,114.0,37.9,37.8,34.9,28.5,28.0,15.0.

The compounds represented by the formula (I-1) -formula (I-15) and the formula (I-17) -formula (I-20) can be obtained by a synthetic method similar to that of the compound represented by the formula (I-16), and only the reactants of the synthetic reaction need to be adjusted.

The lithium ion batteries of examples 1 to 43 and comparative examples 1 to 4 were each prepared as follows

(1) Preparation of the electrolyte

At water content<In a 10ppm argon atmosphere glove box, uniformly mixing non-aqueous organic solvents EC, PC, DEC and EMC according to the mass ratio of 3:5:6:6, and fully drying lithium salt LiPF₆Dissolving in the non-aqueous organic solvent, adding a certain amount of additive, and mixing to obtain LiPF₆Electrolyte with the concentration of 1 mol/L.

(2) Preparation of positive plate

A positive electrode active material NCM811 (molecular formula LiNi)_0.8Mn_0.1Co_0.1O₂) Fully stirring and mixing acetylene black serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder in a proper amount of N-methylpyrrolidone (NMP) solvent according to a weight ratio of 96:2:2 to form uniform positive electrode slurry; coating the slurry on a positive current collector Al foil, drying and cold-pressing to obtain a positive plate, wherein the compaction density of the positive plate is 3.50g/cm³。

(3) Preparation of the separator

A single layer Polyethylene (PE) porous polymer film having a thickness of 5 μm and a porosity of 39% containing Al was used as a separator₂O₃And (3) coating the ceramic.

(4) Preparation of negative plate

Fully stirring and mixing a negative electrode active material graphite, a binder Styrene Butadiene Rubber (SBR) and a thickener sodium carboxymethyl cellulose (CMC) in a proper amount of deionized water according to a weight ratio of 97.4:1.4:1.2 to form uniform negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector Cu foil, drying and cold pressing to obtain a negative electrode plate.

(5) Preparation of lithium ion battery

Stacking the prepared positive plate, the isolating film and the negative plate in sequence to enable the isolating film to be positioned between the positive plate and the negative plate to play an isolating role, and then winding to obtain the bare cell; and (3) placing the bare cell in an outer packaging foil, leaving a liquid injection port, injecting the prepared electrolyte from the liquid injection port, and performing vacuum packaging, standing, formation, shaping and other processes to complete the preparation of the lithium ion battery.

In examples 1 to 43 and comparative examples 1 to 4, the kinds and contents of the additives used are shown in table 1, wherein the contents of the respective additives are weight percentages calculated based on the mass of the electrolyte.

TABLE 1 kinds and contents of additives added in examples 1 to 43 and comparative examples 1 to 4

The following tests were performed on the lithium ion batteries of examples 1 to 43 and comparative examples 1 to 4, respectively

(1) Cycle performance test

Charging the battery to 4.2V at 25 deg.C under 2C, constant voltage charging to 0.05C under 4.2V, and discharging to 2.8V at 8C; the lithium ion battery is subjected to a circulation flow of '2C charging-8C discharging' for multiple times according to the conditions, the circulation is carried out for 800 circles, and the discharge capacity of the 2 nd circle is C₀The discharge capacity at the 800 th circle was C₁。

Capacity retention (%) of 800 cycles at room temperature ═ C₁/C₀×100％。

(2) High temperature storage Performance test

Charging the battery at 25 deg.C with 0.5C constant current to 4.2V, then charging at constant voltage to current of 0.05C, and testing the thickness of the lithium ion battery and recordingIs d'₀(ii) a And then placing the lithium ion battery in an oven at 85 ℃, taking out the lithium ion battery after 24 hours, and testing the thickness of the lithium ion battery at the moment and recording the thickness as d'.

Thickness swelling ratio (%) of (d ' -d ' after storage at 85 ℃ for 24 hours '₀)/d’₀×100％。

(meanwhile, if the thickness expansion rate of the lithium ion battery exceeds 50%, the test is suspended and ended.)

The test results of the lithium ion batteries of examples 1 to 43 and comparative examples 1 to 4 are shown in Table 2

Table 2 results of performance test of lithium ion batteries of examples 1 to 43 and comparative examples 1 to 4

Note: failure indicates that the battery fails to cycle for 800 cycles

The lithium ion batteries of examples 44 to 84 and comparative examples 5 to 7 were each prepared as follows

(1) Preparation of the electrolyte

At water content<In a 10ppm argon atmosphere glove box, uniformly mixing non-aqueous organic solvents EC, PC, DEC, EP and PP according to the mass ratio of 1:1:1:1:1, and then fully drying lithium salt LiPF₆Dissolving in the non-aqueous organic solvent, adding a certain amount of additive, and mixing to obtain LiPF₆Electrolyte with the concentration of 1 mol/L.

(2) Preparation of positive plate

Mixing anode active material LCO (molecular formula is LiCoO)₂) The conductive carbon black and the adhesive polyvinylidene fluoride (PVDF for short) are fully stirred and mixed in a proper amount of N-methyl pyrrolidone (NMP for short) solvent according to the weight ratio of 96:2:2 to form uniform anode slurry; coating the slurry on an Al foil of a positive current collector, drying and cold pressing to obtain a positive plate, wherein the positive compacted density is 4.15g/cm³。

(3) Preparation of the separator

(4) Preparation of negative plate

Fully stirring and mixing a negative electrode active material graphite, a binder Styrene Butadiene Rubber (SBR) and a thickener sodium carboxymethyl cellulose (CMC) in a proper amount of deionized water solvent according to a weight ratio of 97.4:1.4:1.2 to form uniform negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector Cu foil, drying and cold pressing to obtain a negative electrode plate.

(5) Preparation of lithium ion battery

In examples 44 to 84 and comparative examples 5 to 7, the kinds and contents of the additives used are shown in tables 3 and 4, wherein the contents of the respective additives are weight percentages calculated based on the mass of the electrolyte.

TABLE 3 kinds and contents of additives added in examples 44-60 and comparative example 5

The following tests were conducted on the lithium ion batteries of examples 44 to 84 and comparative examples 5 to 7, respectively

(1) Float performance test

The cell was discharged at 25 ℃ to 3.0V at 0.5C, charged to 4.45V at 0.5C, and then charged to 0.05C at a constant voltage of 4.45V, at which time the thickness of the lithium ion cell was tested and recorded as D₀(ii) a And then charging the lithium ion battery for 42 days at a constant voltage of 4.45V, and testing the thickness of the lithium ion battery at the moment and recording the thickness as D.

Thickness expansion ratio (%) after 42 days of floating charge to (D-D)₀)/D₀×100％。

(2) High temperature storage Performance test

The cell was constant current charged at 25 ℃ to 4.45V at 0.5C and then constant voltage charged to a current of 0.05C, at which time the lithium ion cell was tested and reported to be D'₀(ii) a And then placing the lithium ion battery in an oven at 85 ℃, taking out the lithium ion battery after 24 hours, and testing the thickness of the lithium ion battery and recording the thickness as D'.

Thickness swelling ratio (%) after storage at 85 ℃ for 24h, (D '-D'₀)/D’₀×100％。

(3) Cycle performance test

The cell was charged at 25 ℃ to 4.45V at 0.7C and to 0.05C at 4.45V at constant voltage. Discharging to 3.0V with 1C current, charging at 0.7C and discharging at 1C, cycling for 800 circles, and setting the discharge capacity at 2 nd circle as C₀The discharge capacity at the 800 th circle was C₁。

The test results of the lithium ion batteries of examples 44 to 84 and comparative examples 5 to 7 are shown in Table 5

TABLE 5 results of Performance test of the lithium ion batteries of examples 44 to 87 and comparative examples 5 to 7

Note: failure indicates that the battery fails to cycle for 800 cycles

As is apparent from the analysis of the relevant data in tables 1 to 5, the addition of the compound represented by formula (I-A) to the lithium ion battery can improve the high-temperature storage performance, the cycle performance and the float charge performance of the electrochemical device. As can be seen from the data on comparative examples 6 and 7 and examples 44 to 50, when only a dinitrile or trinitrile compound is added to the electrolyte, the improvement effect is inferior to that when the compound represented by the formula (I-A) is added to the electrolyte. This is because the cyano group can coordinate with the transition metal in the high valence state in the positive electrode sheet, and the cyano group exists at each vertex in the tetrahedron-like three-dimensional configuration of the compound represented by formula (I-a) because the cyano group exists on all 4 branches connecting the same carbon atom, so that no matter which side of the molecule of the compound represented by formula (I-a) contacts with the surface of the positive electrode material, the cyano group at three vertices on the side can form a triangular anchoring effect with the transition metal on the surface of the positive electrode material, thereby tightly anchoring the molecule of the compound on the surface of the positive electrode material, and simultaneously, the cyano group at another vertex is also attached near the surface of the positive electrode material, thereby coordinating the transition metal ion coming out from the surface of the positive electrode, thereby better stabilizing the transition metal in the high valence state in the positive electrode sheet, and further improving the stability of the positive electrode interface, the decomposition of the electrolyte caused by oxygen release is relieved; meanwhile, the compound represented by the formula (I-a) has a large number of cyano groups, and therefore can have a high reduction potential, and can form a film on a negative electrode and further improve the stability of the negative electrode.

According to the analysis of the relevant data of examples 1 to 11 and 44 to 50, it can be seen that when the compound represented by the formula (I-a) is present in an amount of 1 to 4% by mass, the improvement effect on the high-temperature storage performance, the cycle performance and the float charge performance of the lithium ion battery is better.

As can be seen from the analysis of the relevant data in tables 1 to 5, when the sulfur-containing dioxygen compound described in the present application is further added to the electrolyte solution to which the compound represented by formula (I-a) is added, the high-temperature storage performance, the cycle performance, and the float charge performance of the lithium ion battery can be further improved at the same time. The sulfur-oxygen-containing bis-amide compound has strong oxidation resistance, so that an electrolyte is not easily oxidized on the surface of a positive electrode, and when the sulfur-oxygen-containing bis-amide compound is used together with a compound represented by the formula (I-A), the coordination of the compound represented by the formula (I-A) and a high-valence transition metal in a positive plate can be promoted, so that a synergistic effect is formed, and the lithium ion battery is better improved.

As can be seen from the analysis of the relevant data in tables 1 to 5, when the boron-containing lithium salt compound described in the present application is further added to the electrolyte solution to which the compound represented by formula (I-a) is added, the high-temperature storage performance, the cycle performance, and the float charge performance of the lithium ion battery can be further improved simultaneously. This is because the thermal stability of lithium tetrafluoroborate and lithium difluorooxalato borate is higher than that of lithium hexafluorophosphate, a fluorine-containing protective film can be better formed on the surface of the negative electrode, the reaction between lithium hexafluorophosphate and the negative electrode is reduced, and when the lithium hexafluorophosphate and the compound represented by the formula (I-a) are used together, the protection of the negative electrode can be enhanced, the stability of the negative electrode is further improved, so that a synergistic effect is formed, and the better improvement of the lithium ion battery is realized.

As can be seen from the analysis of the relevant data in tables 1 to 5, when the dinitrile compound and the trinitrile compound described in the present application are further added to the electrolyte to which the compound represented by formula (I-a) is added, the high-temperature storage performance and the float charge performance of the lithium ion battery can be further improved at the same time, and the balance between the performance and the cost can be achieved. When the sulfur-oxygen-containing bis-nitrile compound, the dinitrile compound and the trinitrile compound are further added to the electrolyte to which the compound represented by the formula (I-A) is added, the high-temperature storage performance and the floating charge performance of the lithium ion battery can be further improved. It is shown that several additive combinations described herein can cooperate with each other to achieve better improvement of lithium ion batteries.

As can be seen from the analysis of the relevant data in tables 1 to 5, when the lithium phosphate salt compound described in the present application is further added to the electrolyte solution to which the compound represented by formula (I-a) is added, the high-temperature storage performance and the float charge performance of the lithium ion battery can be further improved at the same time. When the sulfur-oxygen-containing bis-phosphonium compound and the lithium phosphate compound are further added into the electrolyte solution added with the compound represented by the formula (I-A), the high-temperature storage performance and the floating charge performance of the lithium ion battery can be further improved simultaneously. When the sulfur-oxygen-containing bis-nitrile compound, the dinitrile compound, the trinitrile compound and the lithium phosphate compound are further added into the electrolyte added with the compound represented by the formula (I-A), the high-temperature storage performance and the floating charge performance of the lithium ion battery can be further improved. It is shown that several additive combinations described herein can cooperate with each other to achieve better improvement of lithium ion batteries.

The above detailed description describes exemplary embodiments, but is not intended to limit the combinations explicitly disclosed herein. Thus, unless otherwise specified, various features disclosed herein can be combined together to form a number of additional combinations that are not shown for the sake of brevity.

Claims

1. An electrolytic solution, comprising a compound represented by the formula (I-A);

in the formula (I-A),

m and n are each independently selected from integers of 0 to 2.

2. The electrolyte solution according to claim 1, wherein the compound represented by formula (I-a) includes at least one of compounds represented by formulae (I-1) to (I-20);

3. the electrolyte according to claim 1, wherein the compound represented by formula (I-a) is contained in an amount of 0.01 to 10% by mass based on the mass of the electrolyte.

4. The electrolytic solution according to claim 1, further comprising a compound containing a sulfur-oxygen double bond, the compound containing a sulfur-oxygen double bond comprising at least one of compounds represented by formula (II-a) and formula (II-B);

in the formulae (II-A) and (II-B),

R²¹、R²²、R²³and R²⁴Each independently selected from substituted or unsubstituted C₁-C₅Alkyl, substituted or unsubstituted C₂-C₁₀Alkenyl, substituted or unsubstituted C₂-C₁₀Alkynyl, substituted or unsubstituted C₃-C₁₀Alicyclic hydrocarbon group, substituted or unsubstituted C₆-C₁₀Aryl, substituted or unsubstituted C₁-C₆And, when substituted, the substituent comprises at least one of a halogen and a heteroatom-containing group comprising at least one of O, S, P, N, Si, B, wherein R²¹And R²²Can be bonded to form a ring structure, R²³And R²⁴Can be bonded to form a ring structure.

5. The electrolytic solution according to claim 4, wherein the compound containing a sulfur-oxygen double bond comprises at least one of compounds represented by formulas (II-1) to (II-60);

6. the electrolytic solution according to claim 4, wherein a mass percentage content of the compound containing a sulfur-oxygen double bond is not more than 5% based on a mass of the electrolytic solution.

7. The electrolyte of claim 1, further comprising a boron-containing lithium salt compound.

8. The electrolyte of claim 7, wherein the boron-containing lithium salt compound comprises at least one of lithium tetrafluoroborate, lithium difluorooxalate borate, or lithium bis-oxalate borate.

9. The electrolyte of claim 7, wherein the boron-containing lithium salt compound is present in an amount of 0.01 to 1% by mass, based on the mass of the electrolyte.

10. The electrolyte of claim 1, further comprising at least one of a dinitrile compound and a trinitrile compound.

11. The electrolyte of claim 10,

the dinitrile compound comprises at least one of the following compounds:

the trinitrile compound comprises at least one of the following compounds:

12. the electrolyte of claim 10,

the sum of the mass percentages of the dinitrile compound and the trinitrile compound is 0.5-10% based on the mass of the electrolyte.

13. The electrolyte of claim 10,

the mass percentage content of the compound represented by the formula (I-A) is a% based on the mass of the electrolyte;

the sum of the mass percentage contents of the dinitrile compound and the trinitrile compound is b% based on the mass of the electrolyte;

wherein a/b between a and b is more than or equal to 0.1 and less than or equal to 1.

14. The electrolyte of claim 1, further comprising a lithium phosphate salt compound comprising at least one of lithium difluorophosphate, lithium difluorobis-oxalato-phosphate, and lithium tetrafluorooxalato-phosphate.

15. The electrolyte of claim 14, wherein the lithium phosphate salt compound is present in an amount of 0.01 to 2% by mass, based on the mass of the electrolyte.

16. An electrochemical device comprising a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte according to any one of claims 1 to 15.

17. An electronic device comprising the electrochemical device of claim 16.