Nonaqueous electrolyte solution, and electrochemical device and electronic apparatus including same

Abstract

The invention belongs to the technical field of batteries, particularly relates to the technical field of lithium ion batteries, and particularly relates to a non-aqueous electrolyte which comprises a compound shown in a formula I and a compound shown in a formula II, in the formula I, R1, R2, R3 and R4 are independently selected from any one of a fluorine atom, a difluorophosphoryloxy group, a methanesulfonic acid group and a trifluoromethanesulfonic acid group respectively, and R1, R2, R3 and R4 are independently selected from any one of a fluorine atom, a difluorophosphoryloxy group, a methanesulfonic acid group and a trifluoromethanesulfonic acid group; in the formula II, R5, R6, R7 and R8 are respectively and independently selected from any one of fluorine atoms, trifluoromethyl, and C1-C3 alkyl sulfonic acid groups which are substituted by fluorine atoms or not substituted by fluorine atoms; based on the total mass of the non-aqueous electrolyte, the mass percentage of the compound in the formula I is A, the mass percentage of the compound in the formula II is B, A is more than or equal to 0.01% and less than or equal to 10%, B is more than or equal to 0.05% and less than or equal to 5%, and A / B is more than or equal to 0.01 and less than or equal to 50. According to the present invention, the compound represented by the formula I and the compound represented by the formula II are matched for use in the electrolyte, such that the cycle performance and the high-temperature storage performance of the electrochemical device can be simultaneously improved.

Description

Technical Field

[0001] This application belongs to the technical field of batteries, particularly to the technical field of lithium-ion batteries, and specifically relates to a non-aqueous electrolyte and an electrochemical device and an electronic device comprising the non-aqueous electrolyte. Background Art

[0002] Electrochemical devices, especially lithium-ion batteries, are increasingly widely used in the field of portable electronic products because electrochemical devices, especially lithium-ion batteries, have advantages such as high energy density, high working voltage, light weight, low self-discharge rate, long cycle life, no memory effect, and environmental friendliness. In addition to smart electronic products (including mobile phones, laptops, cameras, etc.) and energy storage products, there is an increasing demand in the fields of higher-power electronic products such as electric vehicles, power tools, drones, and electric ships. High-power electronic products also have higher requirements for the high-temperature gas generation and safety performance of electrochemical devices, especially lithium-ion batteries. Therefore, it is particularly important to develop electrochemical devices, especially lithium-ion batteries, that can balance high-temperature storage and cycling performance. Summary of the Invention

[0003] The purpose of this application is to provide a non-aqueous electrolyte and an electrochemical device and an electronic device comprising the non-aqueous electrolyte to improve the high-temperature storage and cycling performance of the electrochemical device. The specific solutions are as follows:

[0004] According to the first aspect of this application, this application provides a non-aqueous electrolyte, which comprises: a compound of formula I and a compound of formula II;

[0005]

[0006] Wherein, in formula I, R 1 , R 2 , R 3 and R 4 each independently selected from any one of a fluorine atom, a difluorophosphoryloxy group, a methylsulfonic acid group, and a trifluoromethylsulfonic acid group; in formula II, R 5 , R 6 , R 7 and R 8 each independently selected from any one of a fluorine atom, a trifluoromethyl group, a C1-C3 alkylsulfonic acid group substituted or unsubstituted with a fluorine atom; based on the total mass of the non-aqueous electrolyte, the mass percentage of the compound of formula I is A, and the mass percentage of the compound of formula II is B, wherein, A satisfies: 0.01% ≤ A ≤ 10%, B satisfies: 0.05% ≤ B ≤ 5%, and A / B satisfies: 0.01 ≤ A / B ≤ 50.

[0007] When the compound of formula II is used in the electrolyte, the compound of formula II combines with the transition metal element on the surface of the positive electrode material through initial adsorption, and is oxidized and decomposed during the first charging process to form a CEI layer rich in sulfides, achieving the effect of improving the high-temperature storage performance of the electrochemical device. However, when the compound of formula II is used in the electrolyte, there is a problem of insufficient stability at the negative electrode interface, which will lead to deterioration of the cycling performance. In the electrolyte containing the compound of formula II, by introducing the compound of formula I, since the solvation structure of the compound of formula II is adjusted, the compound of formula II mainly exists in the outer layer of the solvation shell, inhibiting the ability of the compound of formula II to be reduced at the negative electrode interface and reducing the reduction decomposition of the compound of formula II at the negative electrode. In addition, the compound of formula I can be catalyzed by the transition metal at the positive electrode interface, and the generated organoboron (B) compound can further synergistically inhibit the activity of the transition metal with the compound of formula II. Therefore, introducing the compound of formula I into the electrolyte containing the compound of formula II can achieve the effect of improving the stability of the positive and negative electrode interfaces, further improving the stability of the electrolyte at the negative electrode, and thus improving the high-temperature storage and cycling performance. And through further research in this application, it is found that regulating the mass percentage A of the compound of formula I in the electrolyte and the ratio A / B between the mass percentage A of the compound of formula I in the electrolyte and the mass percentage B of the compound of formula II in the electrolyte within the above ranges can achieve better improvement of the high-temperature storage and cycling performance of the electrochemical device. If A and A / B are lower than the above ranges, the film-forming effect cannot be achieved, and if they exceed the above ranges, the interfacial kinetics will deteriorate, resulting in deterioration of the cycling performance of the electrochemical device.

[0008] In some embodiments of the present application, the mass percentage A of the compound of formula I satisfies: 0.06% ≤ A ≤ 5%; preferably, A satisfies: 0.1% ≤ A ≤ 5%. Further regulating the mass percentage A of the compound of formula I in the non-aqueous electrolyte within the above range can achieve the effect of further improving the high-temperature storage.

[0009] In some embodiments of the present application, the ratio A / B between the mass percentage A of the compound of formula I and the mass percentage B of the compound of formula II satisfies: 0.05 ≤ A / B ≤ 50. Further regulating the ratio A / B between the mass percentage A of the compound of formula I in the non-aqueous electrolyte and the mass percentage B of the compound of formula II in the non-aqueous electrolyte within the above range can achieve the effect of further improving the high-temperature storage.

[0010] In some embodiments of the present application, the mass percentage B of the compound of Formula II satisfies: 0.05% ≤ B ≤ 3.4%; preferably, B satisfies: 0.1% ≤ B ≤ 3%. By controlling the mass percentage B of the compound of Formula II in the non-aqueous electrolyte within the above range, it is possible to further improve the high-temperature storage performance of the battery while further reducing its reductive decomposition at the negative electrode.

[0011] In some embodiments of the present application, the compound of Formula I includes at least one of the following compounds of Formula I-1 to Formula I-9:

[0012]

[0013] In the technical solution provided by the present application, when at least one of the above compounds is selected as the compound of Formula I, the effect is better when used in combination with the compound of Formula II in the electrolyte, and better high-temperature storage and cycling performance can be achieved.

[0014] In some embodiments of the present application, the compound of Formula II includes at least one of the following compounds of Formula II-1 to Formula II-9:

[0015]

[0016] In the technical solution provided by the present application, when at least one of the above compounds is selected as the compound of Formula II, the effect is better when used in combination with the compound of Formula I in the electrolyte, and better high-temperature storage and cycling performance can be achieved. In some embodiments of the present application, the non-aqueous electrolyte further includes a carbonate substance; the carbonate substance includes at least one of vinylene carbonate, ethylene vinylene carbonate, or fluoroethylene carbonate; based on the total mass of the non-aqueous electrolyte, the mass percentage of the carbonate substance is F, and F satisfies: 0.1% ≤ F ≤ 5%. In the further solution provided by the present application, introducing a carbonate substance into the electrolyte containing the compound of Formula II and the compound of Formula I can form a polycarbonate-rich structure at the negative electrode interface. This structure can evenly wrap elements such as boron, phosphorus, and sulfur at the negative electrode interface to form a stable SEI film, achieving the effect of further improving the cycling performance; at the same time, the content of the carbonate substance in the electrolyte will also further affect the high-temperature storage and cycling performance of the electrochemical device. When the content of the carbonate substance is too high, too much carbonate will accumulate at the negative electrode interface, resulting in deterioration of the high-temperature storage performance. When the content of the carbonate substance is too low, the improvement effect will not be achieved. Therefore, further controlling the mass percentage F of the carbonate substance in the non-aqueous electrolyte within the above range can achieve further improvement of the high-temperature storage and cycling performance.

[0017] In some embodiments of the present application, the ratio F / (A + B) between the mass percentage F of the carbonate substance, the mass percentage A of the compound of Formula I, and the mass percentage B of the compound of Formula II satisfies the following relationship: 0.01 ≤ F / (A + B) ≤ 50; preferably, F / (A + B) satisfies the following relationship: 0.1 ≤ F / (A + B) ≤ 5. Further regulating F / (A + B) within the above range can achieve the effect of further improving the high-temperature storage and cycling performance. If F / (A + B) exceeds the above range, too much carbonate will accumulate at the negative electrode interface, resulting in the deterioration of the high-temperature storage performance. If F / (A + B) is lower than the above range, the improvement effect will not be achieved.

[0018] According to the second aspect of the present application, the present application also provides an electrochemical device, which includes: a positive electrode, a negative electrode, and an electrolyte, and the electrolyte is selected from the non-aqueous electrolytes described in any one of the first aspects of the present application. The electrochemical device containing the above non-aqueous electrolyte has good high-temperature storage and cycling performance.

[0019] In some embodiments of the present application, the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a nickel-cobalt-manganese-based transition metal oxide. In the electrolyte system provided by the present application, the compounds of Formula I and Formula II in the electrolyte are more likely to combine with the transition metal nickel, and the catalytic effect of nickel element on the compounds of Formula I and Formula II is more obvious, and the film-forming effect is better. Using the electrolyte system provided by the present application in combination with the above positive electrode active material can more significantly improve the high-temperature storage effect.

[0020] In some embodiments of the present application, the particle size Dv10 of the positive electrode active material is 0.5 μm to 4 μm.

[0021] In some embodiments of the present application, the particle size Dv50 of the positive electrode active material is 2 μm to 10 μm.

[0022] In some embodiments of the present application, the particle size Dv90 of the positive electrode active material is 7.9 μm - 11.4 μm.

[0023] In some embodiments of the present application, the pole piece compaction density of the positive electrode active material is 2.5 to 3.6 g / cm 3 .

[0024] When the positive electrode active material is in the above-mentioned particle size range, it has a suitable specific surface area. The suitable specific surface area can effectively react with the compounds of formula I and formula II in the electrolyte to form a film, further improving the high-temperature storage performance of the electrochemical device, and the suitable specific surface area can also reduce the negative impact of cycle deterioration caused by the contact between the electrolyte solvent and the active site.

[0025] In some embodiments of the present application, the negative electrode includes a negative electrode current collector and a negative electrode material layer located on at least one surface of the negative electrode current collector, and the particle size Dv10 of the negative electrode active material of the negative electrode active material layer is 5 μm to 10 μm.

[0026] In some embodiments of the present application, the particle size Dv50 of the negative electrode active material is 10 μm-20 μm.

[0027] In some embodiments of the present application, the particle size Dv90 of the negative electrode active material is 27.8 μm-38.1 μm.

[0028] In some embodiments of the present application, the compaction density of the negative electrode active material is 1.5 g / cm 3 ~1.7g / cm 3 .

[0029] When the negative electrode active material is within the above particle size range, it has a suitable specific surface area, and the suitable specific surface area can effectively react with the compounds of formula I and formula II in the electrolyte to form a film, further improving the high temperature storage performance of the electrochemical device.

[0030] According to the third aspect of the present application, the present application further provides an electronic device, which includes the electrochemical device described in any one of the second aspects of the present application. DETAILED DESCRIPTION

[0031] The technical solution of the present application is further described below through specific embodiments, which do not limit the protection scope of the present application. Some non-essential modifications and adjustments made by others based on the concept of the present application still fall within the protection scope of the present application.

[0032] 1. Electrolyte

[0033] According to the first aspect of the present application, the non-aqueous electrolyte comprises: a compound of formula I and a compound of formula II;

[0034]

[0035] Wherein, in Formula I, R 1 , R 2 , R 3 and R 4Each independently selected from any one of a fluorine atom, a difluorophosphoryloxy group, a methylsulfonic acid group, and a trifluoromethylsulfonic acid group; in Formula II, R 5 、R 6 、R 7 and R 8 are each independently selected from any one of a fluorine atom, a trifluoromethyl group, and a C1-C3 alkylsulfonic acid group which may or may not be substituted with a fluorine atom; based on the total mass of the non-aqueous electrolyte, the mass percentage of the compound of Formula I is A, and the mass percentage of the compound of Formula II is B, where A satisfies: 0.01% ≤ A ≤ 10%, B satisfies: 0.05% ≤ B ≤ 5%, and A / B satisfies: 0.01 ≤ A / B ≤ 50.

[0036] Specifically, the structural formula of the difluorophosphoryloxy group is represented as When R 1 、R 2 、R 3 or R 4 is selected from the difluorophosphoryloxy group, the O in P-O in the structural formula of the difluorophosphoryloxy group is connected to B to form the compound of Formula I. Specifically, the structural formula of the methylsulfonic acid group is represented as When R 1 、R 2 、R 3 or R 4 is selected from the methylsulfonic acid group, the O in S-O in the methylsulfonic acid group is connected to B to form the compound of Formula I. The structural formula of the trifluoromethylsulfonic acid group is represented as When R 1 、R 2 、R 3 or R 4 is selected from the trifluoromethylsulfonic acid group, the O in S-O in the trifluoromethylsulfonic acid group is connected to B to form the compound of Formula I.

[0037] Specifically, in the technical solution provided by the present application, based on the total mass of the non-aqueous electrolyte, the mass percentage A of the compound of Formula I can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8.0%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%, 8.7%, 8.8%, 8.9%, 9.0%, 9.1%, 9.2%, 9.3%, 9.4%, 9.5%, 9.6%, 9.7%, 9.8%, 9.9%, 10% or a range composed of any two of the above values. Specifically, based on the total mass of the non-aqueous electrolyte, the mass percentage B of the compound of Formula II can be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0% or a range composed of any two of the above values.Based on the total mass of the non-aqueous electrolyte, the ratio A / B of the mass percentage A of the compound of Formula I to the mass percentage B of the compound of Formula II can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 4.0, 4.5, 5.0, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19.0, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 or a range composed of any two of the above values.

[0038] When the compound of Formula II is used in the electrolyte, through initial adsorption, the compound of Formula II combines with the transition metal elements on the surface of the positive electrode material and undergoes oxidative decomposition during the first charging process to form a CEI layer rich in sulfides, achieving the effect of improving the high-temperature storage performance of the battery. However, when the compound of Formula II is used in the electrolyte, there is a problem of insufficient stability at the negative electrode interface, which will lead to deterioration of the cycling performance. In the electrolyte containing the compound of Formula II, by introducing the compound of Formula I, since the solvation structure of the compound of Formula II is adjusted, the compound of Formula II mainly exists in the outer layer of the solvation shell, inhibiting the ability of the compound of Formula II to be reduced at the negative electrode interface and reducing the reduction decomposition of the compound of Formula II at the negative electrode. In addition, the compound of Formula I can be catalyzed by the transition metal at the positive electrode interface to generate an organoboron (B) compound, which can further cooperate with the compound of Formula II to inhibit the activity of the transition metal. Therefore, introducing the compound of Formula I into the electrolyte containing the compound of Formula II can achieve the effect of improving the stability of the positive and negative electrode interfaces, further improving the stability of the electrolyte at the negative electrode, thereby improving the high-temperature storage and cycling performance. And through further research in this application, it is found that controlling the mass percentage A of the compound of Formula I in the electrolyte and the ratio A / B between the mass percentage A of the compound of Formula I in the electrolyte and the mass percentage B of the compound of Formula II in the electrolyte within the above ranges can achieve better effects of improving high-temperature storage and cycling performance. If A and A / B are lower than the above ranges, the film-forming effect will not be achieved; if they exceed the above ranges, the interfacial kinetics will deteriorate, leading to deterioration of the cycling performance.

[0039] In some embodiments of the present application, based on the total mass of the non-aqueous electrolyte, the mass percentage A of the compound of Formula I satisfies: 0.06% ≤ A ≤ 5%; preferably, A satisfies: 0.1% ≤ A ≤ 5%. Further regulating the mass percentage A of the compound of Formula I in the electrolyte within the above range can achieve the effect of further improving high-temperature storage.

[0040] In some embodiments of the present application, based on the total mass of the non-aqueous electrolyte, the ratio A / B between the mass percentage A of the compound of Formula I and the mass percentage B of the compound of Formula II satisfies: 0.05 ≤ A / B ≤ 50. Further regulating the range of the ratio A / B between the mass percentage A of the compound of Formula I and the mass percentage B of the compound of Formula II in the electrolyte within the above range can achieve the effect of further improving high-temperature storage.

[0041] In some embodiments of the present application, based on the total mass of the non-aqueous electrolyte, the mass percentage B of the compound of Formula II satisfies: 0.05% ≤ B ≤ 3.4%; preferably, B satisfies: 0.1% ≤ B ≤ 3%. Regulating the mass percentage B of the compound of Formula II in the non-aqueous electrolyte within the above range can achieve the effect of further improving the high-temperature storage performance of the battery while further reducing its reductive decomposition at the negative electrode.

[0042] In some embodiments of the present application, the compound of Formula I includes at least one of the following compounds of Formula I-1 to Formula I-9:

[0043]

[0044]

[0045] In the technical solution provided by the present application, when at least one of the above compounds is selected as the compound of Formula I, the effect is better when used in combination with the compound of Formula II in the electrolyte, and better high-temperature storage, cycling and other performances can be achieved.

[0046] In some embodiments of the present application, the compound of Formula II includes at least one of the following compounds of Formula II-1 to Formula II-9:

[0047]

[0048] In the technical solution provided by the present application, when at least one of the above compounds is selected as the compound of Formula II, the effect is better when used in combination with the compound of Formula I in the electrolyte, and better high-temperature storage, cycling and other performances can be achieved.

[0049] In some embodiments of the present application, the non-aqueous electrolyte further includes a carbonate substance; the carbonate substance includes at least one of vinylene carbonate, ethylene vinylene carbonate, and fluoroethylene carbonate; based on the total mass of the non-aqueous electrolyte, the mass percentage of the carbonate substance is F, and F satisfies: 0.1% ≤ F ≤ 5%.

[0050] Specifically, based on the total mass of the non-aqueous electrolyte, the mass percentage F of the carbonate substance in the non-aqueous electrolyte can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0% or a range composed of any two of the above values.

[0051] In a further solution provided by the present application, introducing a carbonate substance into the electrolyte containing the compound of formula II and the compound of formula I can form a polycarbonate-rich structure at the negative electrode interface. This structure can uniformly wrap and cover elements such as boron, phosphorus, and sulfur at the negative electrode interface to form a stable SEI film, achieving the effect of further improving the cycling performance; at the same time, the content of the carbonate substance in the electrolyte will also further affect the high-temperature storage and cycling performance of the electrochemical device. When the content of the carbonate substance is too high, too much carbonate will accumulate at the negative electrode interface, resulting in deterioration of the high-temperature storage performance. If the content of the carbonate substance is too low, the improvement effect will not be achieved. Therefore, further regulating the mass percentage F of the carbonate substance in the non-aqueous electrolyte within the above range can achieve further improvement of the high-temperature storage and cycling performance.

[0052] In some embodiments of the present application, the ratio F / (A + B) between the mass percentage F of the carbonate substance, the mass percentage A of the compound of Formula I, and the mass percentage B of the compound of Formula II satisfies the following relationship: 0.01 ≤ F / (A + B) ≤ 50. Specifically, based on the total mass of the non-aqueous electrolyte, the ratio F / (A + B) between the mass percentage F of the carbonate substance, the mass percentage A of the compound of Formula I, and the mass percentage B of the compound of Formula II can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 4.0, 4.5, 5.0, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19.0, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 or a range composed of any two of the above values. Preferably, F / (A + B) satisfies the following relationship: 0.1 ≤ F / (A + B) ≤ 5. Further regulating F / (A + B) within the above range can achieve the effect of further improving the high-temperature storage and cycling performance.

[0053] In some embodiments of the present application, the non-aqueous electrolyte provided by the present application may further contain some other components, and the other components may include but are not limited to: diethyl carbonate (DEC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC). In some embodiments of the present application, the other components may include ether solvents, and the ether solvents include but are not limited to at least one of 1,3-dioxolane (DOL) and dimethoxyethane (DME).

[0054] In some embodiments of the present application, the electrolyte of the present application may further include an electrolyte salt. The present application does not particularly limit the type of the electrolyte salt, as long as the object of the present application can be achieved. For example, the electrolyte salt may include, but is not limited to, a lithium salt or a sodium salt. The lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methyl, lithium difluoro(oxalato)phosphate or lithium tetrafluoro(oxalato)phosphate; the sodium salt may include, but is not limited to, at least one of sodium hexafluorophosphate, sodium perchlorate, sodium trifluoromethanesulfonate, sodium tetrachloroaluminate, sodium tetrachloroborate, sodium tetrafluoroborate, sodium nitrate, sodium tetrafluorophosphate, sodium hexafluoroarsenate, sodium hexafluoroantimonate or sodium hexafluoroarsenate. The present application does not particularly limit the mass percentage content of the electrolyte salt, as long as the object of the present application can be achieved. In some embodiments, based on the total mass of the non-aqueous electrolyte, the mass percentage of the electrolyte salt in the electrolyte is 10% to 20%. Specifically, based on the total mass of the non-aqueous electrolyte, the mass percentage of the electrolyte salt is 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or a range composed of any two of the above values.

[0055] In some embodiments of the present application, the preparation method of the electrolyte provided by the present application is not limited, and it can be prepared in the conventional way of the electrolyte. In some embodiments, the electrolyte of the present application can be prepared by mixing each component.

[0056] II. Electrochemical Device

[0057] According to the second aspect of the present application, the present application also provides an electrochemical device. In some embodiments of the present application, the electrochemical device of the present application includes, but is not limited to: all kinds of primary batteries, secondary batteries, fuel cells, solar cells or capacitors. In some embodiments of the present application, the electrochemical device is a lithium secondary battery. In some embodiments of the present invention, the lithium secondary battery includes, but is not limited to: lithium metal secondary battery, lithium ion secondary battery, lithium polymer secondary battery or lithium ion polymer secondary battery. In some embodiments of the present application, the electrochemical device of the present application can also be a non-aqueous anode battery system.

[0058] The electrochemical device includes: a positive electrode, a negative electrode and an electrolyte, and the electrolyte is selected from the non-aqueous electrolytes described in any item of the first aspect of the present application. The electrochemical device containing the above electrolyte has excellent high-temperature storage and cycling performance.

[0059] 1. Positive Electrode

[0060] In some embodiments of the present application, the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material. In some embodiments of the present application, the positive electrode active material includes a lithium transition metal composite oxide. In some embodiments, the positive electrode active material is selected from at least one of the following: lithium cobalt oxide, lithium nickel manganese cobalt ternary material, lithium manganese oxide, lithium nickel manganese oxide, or lithium iron phosphate.

[0061] In some embodiments of the present application, the positive electrode active material is selected from nickel cobalt manganese-based transition metal oxides; in some embodiments, the positive electrode active material is selected from NCM811. In the electrolyte system provided by the present application, the compounds of Formula I and Formula II in the electrolyte are more likely to combine with the transition metal nickel, and the catalytic effect of nickel element on the compounds of Formula I and Formula II is more obvious, and the film-forming effect is better. Using the electrolyte system provided by the present application in combination with the above positive electrode active material can more significantly improve the high-temperature storage effect.

[0062] In some embodiments of the present application, the Dv10 particle size of the positive electrode active material is 0.5 μm to 4 μm. Specifically, the Dv10 particle size of the positive electrode active material can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 4.0 μm or a range composed of any two of the above values.

[0063] In some embodiments of the present application, the particle size Dv50 of the positive electrode active material is 2 μm to 10 μm. Specifically, the particle size Dv50 of the positive electrode active material can be 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 4.0 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 5.0 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6.0 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, 6.9 μm, 7.0 μm, 7.1 μm, 7.2 μm, 7.3 μm, 7.4 μm, 7.5 μm, 7.6 μm, 7.7 μm, 7.8 μm, 7.9 μm, 8.0 μm, 8.1 μm, 8.2 μm, 8.3 μm, 8.4 μm, 8.5 μm, 8.6 μm, 8.7 μm, 8.8 μm, 8.9 μm, 9.0 μm, 9.1 μm, 9.2 μm, 9.3 μm, 9.4 μm, 9.5 μm, 9.6 μm, 9.7 μm, 9.8 μm, 9.9 μm, 10 μm or a range composed of any two of the above values.

[0064] In some embodiments of the present application, the particle size Dv90 of the positive electrode active material is 7.9 μm - 11.4 μm. Specifically, the particle size Dv90 of the positive electrode active material can be 7.9 μm, 8.0 μm, 8.1 μm, 8.2 μm, 8.3 μm, 8.4 μm, 8.5 μm, 8.6 μm, 8.7 μm, 8.8 μm, 8.9 μm, 9.0 μm, 9.1 μm, 9.2 μm, 9.3 μm, 9.4 μm, 9.5 μm, 9.6 μm, 9.7 μm, 9.8 μm, 9.9 μm, 10 μm, 10.1 μm, 10.2 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.6 μm, 10.7 μm, 10.8 μm, 10.9 μm, 11 μm or a range composed of any two of the above values.

[0065] In some embodiments of the present application, the tap density of the positive electrode active material is 2.5 - 3.6 g / cm 3 . Specifically, the tap density of the positive electrode active material can be 2.5 g / cm 3 g / cm 3 , 2.6 g / cm 3 , 2.7 g / cm3 , 2.8 g / cm 3 , 2.9 g / cm 3 , 3.0 g / cm 3 , 3.1 g / cm 3 , 3.2 g / cm 3 , 3.3 g / cm 3 , 3.4 g / cm 3 , 3.5 g / cm 3 , 3.6 g / cm 3 or a range composed of any two of the above values.

[0066] When the positive electrode active material is within the above particle size range, it has a suitable specific surface area. The suitable specific surface area can effectively undergo a film-forming reaction with the compounds of Formula I and Formula II in the electrolyte, further improving the high-temperature storage performance of the electrochemical device. Moreover, the suitable specific surface area can also reduce the negative impact of the deterioration of the cycle caused by the contact between the electrolyte solvent and the active sites.

[0067] In some embodiments of the present application, the particle size of the positive electrode active material is tested for the average particle size and the number of particles by scanning electron microscopy (SEM). Specifically: a test area is selected in the scanning electron microscopy field of view, and the average particle size and the number of particles in the test area are counted. The tap density of the positive electrode active material is measured by (the mass of the single-sided wafer - the mass of the aluminum foil of the wafer) / the area of the unit wafer.

[0068] In some embodiments of the present application, the positive electrode active material layer further includes a binder. The binder can improve the binding between the positive electrode active material particles and can also improve the binding between the positive electrode active material and the positive electrode current collector. In some embodiments, the binder includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon, etc.

[0069] In some embodiments of the present application, the positive electrode active material layer further includes a conductive agent to endow the electrode with conductivity. The conductive agent can include any conductive material as long as it does not cause chemical changes. Non-limiting examples of the conductive material include carbon-based materials (such as carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (such as metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (such as polyphenylene derivatives), and mixtures thereof.

[0070] In some embodiments of the present application, the positive electrode current collector is a metal, such as aluminum foil.

[0071] In some embodiments of the present application, the structure of the positive electrode is a positive electrode structure known to those skilled in the art and can be used in electrochemical devices.

[0072] In some embodiments of the present application, the preparation method of the positive electrode is a preparation method of the positive electrode known to those skilled in the art and can be used in electrochemical devices. For example, the positive electrode can be obtained by the following method: mixing a positive electrode active material, a conductive agent, and a binder in a solvent to prepare a positive electrode active material slurry, and coating the positive electrode active material slurry on a positive electrode current collector, drying, and cold pressing to form a positive electrode active material layer. In some embodiments, the solvent may include water, N-methylpyrrolidone, etc., but is not limited thereto.

[0073] 2. Negative electrode

[0074] In some embodiments of the present application, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes graphite, and the graphite includes at least one of artificial graphite or natural graphite.

[0075] In some embodiments of the present application, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, and the Dv10 of the negative electrode active material of the negative electrode active material layer is 5 μm to 10 μm. Specifically, the Dv50 of the negative electrode active material can be 5.0 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6.0 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, 6.9 μm, 7.0 μm, 7.1 μm, 7.2 μm, 7.3 μm, 7.4 μm, 7.5 μm, 7.6 μm, 7.7 μm, 7.8 μm, 7.9 μm, 8.0 μm, 8.1 μm, 8.2 μm, 8.3 μm, 8.4 μm, 8.5 μm, 8.6 μm, 8.7 μm, 8.8 μm, 8.9 μm, 9.0 μm, 9.1 μm, 9.2 μm, 9.3 μm, 9.4 μm, 9.5 μm, 9.6 μm, 9.7 μm, 9.8 μm, 9.9 μm, 10 μm or a range composed of any two of the above values.

[0076] In some embodiments of the present application, the Dv50 particle size of the negative electrode active material is 10 μm - 20 μm. Specifically, the Dv50 particle size of the negative electrode active material can be 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, 20 μm, or a range composed of any two of the above values.

[0077] In some embodiments of the present application, the Dv90 particle size of the negative electrode active material is 27.8 μm - 38.1 μm. Specifically, the Dv90 particle size of the negative electrode active material can be 27.8 μm, 27.9 μm, 28 μm, 28.1 μm, 28.2 μm, 28.3 μm, 28.4 μm, 28.5 μm, 28.6 μm, 28.7 μm, 28.8 μm, 28.9 μm, 29.0 μm, 29.1 μm, 29.2 μm, 29.3 μm, 29.4 μm, 29.5 μm, 29.6 μm, 29.7 μm, 29.8 μm, 29.9 μm, 30 μm, 30.5 μm, 31 μm, 31.5 μm, 32 μm, 32.5 μm, 33 μm, 33.5 μm, 34 μm, 34.5 μm, 35 μm, 35.5 μm, 36 μm, 36.5 μm, 37 μm, 37.5 μm, 37.5 μm, 38.0 μm, 38.1 μm, or a range composed of any two of the above values.

[0078] In some embodiments of the present application, the tap density of the negative electrode active material is 1.5 g / cm 3 ~1.7 g / cm 3 。Specifically, the tap density of the negative electrode active material can be 1.5 g / cm 3 、1.51 g / cm 3 、1.52 g / cm 3 、1.53 g / cm 3 、1.54 g / cm 3 、1.55 g / cm 3 、1.56 g / cm 3 、1.57 g / cm 3 、1.58 g / cm 3 、1.59 g / cm 3 、1.6 g / cm 3 、1.61 g / cm 3 、1.62 g / cm 3 、1.63 g / cm 3 、1.64 g / cm3 , 1.65 g / cm 3 , 1.66 g / cm 3 , 1.67 g / cm 3 , 1.68 g / cm 3 , 1.69 g / cm 3 , 1.7 g / cm 3 or a range composed of any two of the above values.

[0079] When the negative electrode active material is within the above particle size range, it has a suitable specific surface area, and the suitable specific surface area can effectively undergo a film-forming reaction with the compounds of Formula I and Formula II in the electrolyte, further improving the high-temperature storage performance of the electrochemical device.

[0080] In some embodiments of the present application, the particle size of the negative electrode active material is tested for the average particle size and the number of particles by scanning electron microscopy (SEM). Specifically: a test area is selected in the scanning electron microscopy field of view, and the average particle size and the number of particles in the test area are counted. The tap density of the negative electrode active material is measured by (the mass of the single-sided wafer - the mass of the aluminum foil of the wafer) / the area of the unit wafer.

[0081] In some embodiments of the present application, the negative electrode active material layer further includes a conductive agent to improve the electrode conductivity. Any conductive material can be used as the conductive material as long as it does not cause chemical changes. Examples of the conductive agent include, but are not limited to: carbon-based materials, such as carbon black, acetylene black, Ketjen black, carbon fiber, etc.; metal-based materials, such as metal powders or metal fibers including copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives, etc.; or mixtures thereof.

[0082] In some embodiments of the present application, the negative electrode active material layer further includes a thickening agent. The thickening agent can be selected from sodium carboxymethyl cellulose.

[0083] In some embodiments of the present application, the negative electrode active material layer further includes a binder, and the binder can include various adhesive polymers, such as polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0084] In some embodiments of the present application, the negative electrode current collector includes, but is not limited to: copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metals, and any combination thereof. In some embodiments, the negative electrode current collector is a copper foil.

[0085] In some embodiments of the present application, the structure of the negative electrode can be a negative electrode structure known to those skilled in the art and applicable to electrochemical devices.

[0086] In some embodiments of the present application, the preparation method of the negative electrode is a preparation method of the negative electrode known to those skilled in the art and applicable to electrochemical devices. Exemplarily, the negative electrode can be obtained by the following method: mixing a negative electrode active material, a conductive agent, and a binder in a solvent, and heating a thickener as needed to prepare a negative electrode active material slurry, and coating the negative electrode active material slurry on a negative electrode current collector, drying, and cold pressing to form a negative electrode active material layer. In some embodiments, the solvent can include, but is not limited to, water and N-methylpyrrolidone.

[0087] 3. Separator

[0088] In some embodiments of the present application, the electrochemical device further includes a separator. In some embodiments, the separator includes a substrate layer, which is a non-woven fabric, a film, or a composite film with a porous structure. The material of the substrate layer can be selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, the material of the substrate layer can be selected from at least one of a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film. A surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer can be a polymer layer, an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. Specifically, the inorganic layer includes inorganic particles and a binder. The inorganic particles can be selected from one or a combination of several of alumina, silica, magnesia, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder can be selected from one or a combination of several of polyvinylidene fluoride, a polymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0089] In some embodiments of the present application, the preparation method of the electrochemical device provided in the present application is not limited and can be prepared in the manner of a conventional electrochemical device. In some embodiments, the electrochemical device of the present application can be prepared by the following method: stacking the positive electrode, the separator, and the negative electrode in sequence, with the separator acting as a separator between the positive and negative electrodes, and then winding to obtain a bare battery cell; after welding the electrode tabs, placing the bare battery cell in an outer packaging foil-aluminum plastic film, injecting the above-prepared electrolyte, and then undergoing processes such as vacuum packaging, standing, formation, shaping, and capacity testing to obtain the electrochemical device.

[0090] III. Electronic Devices

[0091] According to the third aspect of the present application, the present application further provides an electronic device, and the electronic device includes the electrochemical device as described in any of the second aspects of the present application. In some embodiments of the present application, the electronic device includes, but is not limited to: laptop computers, pen input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, minidiscs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc. In addition, the electrochemical device provided by the present application is applicable not only to the above-mentioned exemplified electronic devices, but also to energy storage power stations, marine vehicles, and air vehicles, and the air vehicles include air vehicles within the atmosphere and air vehicles outside the atmosphere.

[0092] Hereinafter, the embodiments of the present application will be described in more detail by specific examples and comparative examples.

[0093] I. Test Methods Used in Examples and Comparative Examples

[0094] (1) High-temperature Storage Performance Test of Lithium-ion Batteries

[0095] Place the lithium-ion battery in a constant temperature environment of 25°C and let it stand for 30 minutes to make the lithium-ion battery reach a constant temperature state of 25°C. Charge it at a constant current of 0.5C to 4.5V and then charge it at a constant voltage of 4.5V until the current is 0.025C, and record the thickness of the lithium-ion battery at this time as the initial thickness H0. Transfer the lithium-ion battery to a constant temperature oven at 60°C for storage for 30 days. During this period, test and record the thickness of the lithium-ion battery every 6 days. The test thickness recorded after 30 days is the storage thickness H1. The high-temperature storage thickness expansion rate = (H1 - H0) / H0 × 100%. Evaluate the high-temperature storage performance of the lithium-ion battery through the high-temperature storage thickness expansion rate.

[0096] (2) Cycle Performance Test of Lithium-ion Batteries

[0097] The lithium-ion battery was placed in a constant temperature environment of 25°C and left to stand for 30 min to allow the lithium-ion battery to reach a constant temperature state of 25°C. It was charged at a constant current of 0.5C to 4.5V, charged at a constant voltage of 4.5V until the current reached 0.025C, left to stand for 5 min, and discharged at a constant current of 0.5C to 3.0V. The initial discharge capacity was recorded as C0. The above charge-discharge steps were cycled 150 times, and the discharge capacity after 150 cycles was recorded as C1. The cycle capacity retention rate = C1 / C0 × 100%. The cycle performance of the lithium-ion battery was evaluated by the cycle capacity retention rate.

[0098] II. Specific Examples and Comparative Examples

[0099] Example 1-1

[0100] (1) Preparation of the positive electrode

[0101] The positive electrode active material NCM811, the conductive agent Super P, and the binder polyvinylidene fluoride were mixed at a weight ratio of 97:1.4:1.6, added to the N-methylpyrrolidone (NMP) solvent, and stirred evenly under the action of a vacuum mixer to obtain a positive electrode slurry. The solid content of the positive electrode slurry was 72 wt%. The positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil. The coated aluminum foil was dried at 85°C, and then after cold pressing, slicing, and slitting, it was dried in a vacuum at 85°C for 4 h to obtain the positive electrode.

[0102] (2) Preparation of the negative electrode

[0103] The negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) were mixed at a weight ratio of 96:2:0.8:1.2, added with deionized water, and a negative electrode slurry was obtained under the action of a vacuum mixer. The solid content of the negative electrode slurry was 54 wt%. The negative electrode slurry was evenly coated on the negative electrode current collector copper foil according to the areal density of the negative electrode active material of 7.8 mg / cm 2 The coated copper foil was dried at 85°C, and then after cold pressing, slicing, and slitting, it was dried in a vacuum at 120°C for 12 h to obtain the negative electrode.

[0104] (3) Preparation of the electrolyte

[0105] In a dry argon atmosphere glove box (with water content < 10 ppm), the solvents were mixed in a mass ratio of EC:DEC:EMC = 30:40:30. Then, fully dried lithium salt LiPF6 (1 mol / kg, abbreviated as 1M) was added. After dissolution and thorough stirring, Compound I (Formula I-1) and Compound II (Formula II-1) were added. After mixing evenly, an electrolyte solution was obtained. Among them, based on the total mass of the electrolyte solution, the mass percentage of Compound I (Formula I-1) was 0.01%, the mass percentage of Compound II (Formula II-1) was 5%, the mass percentage of LiPF6 was 12.5%, and the balance was a mixed solvent composed of EC, DEC, and EMC.

[0106] (4) Preparation of the separator

[0107] A 9-μm-thick polyethylene (PE) separator was selected. After coating with PVDF slurry and an inorganic particle slurry (with a mass ratio of flaky boehmite to Al2O3 of 70:30) and drying, the final separator was obtained. The coating thickness was 3 μm, and the porosity of the separator was 55%.

[0108] (5) Preparation of the lithium-ion battery

[0109] The positive electrode, separator, and negative electrode were stacked in sequence, with the separator placed between the positive and negative electrodes to play an insulating role. Then, it was wound to obtain a bare battery cell. After welding the tabs, the bare battery cell was placed in an outer packaging aluminum-plastic film, and the above-prepared electrolyte was injected. Then, through processes such as vacuum packaging, standing, formation (constant current charging at 0.2C to 4.3V, and then constant voltage charging at 4.3V to 0.05C), shaping, and capacity testing, a soft-pack lithium-ion battery was obtained.

[0110] Examples 1-2 to 1-26

[0111] Except for adjusting the specific type and content A / % of Compound I and the specific type and content B / % of Compound II according to Table 1, the other parameters were the same as those in Example 1-1.

[0112] Comparative Examples 1-1 to 1-13

[0113] Except for adjusting the specific type and content A / % of Compound I and the specific type and content B / % of Compound II according to Table 1, the other parameters were the same as those in Example 1-1.

[0114] According to the above test methods, the high-temperature storage performance (high-temperature storage thickness expansion rate, %) and cycling performance (cycling capacity retention rate, %) of the lithium-ion batteries prepared through Examples 1-1 to 1-26 and Comparative Examples 1-1 to 1-13 were tested respectively. The results are shown in Table 1:

[0115] Table 1

[0116]

[0117]

[0118] According to the results presented in Table 1, referring to Comparative Examples 1-1 to 1-11 and Examples 1-1 to 1-26, adding Compound I and Compound II to the electrolyte simultaneously and using them in combination can significantly improve the high-temperature storage performance and cycling performance of lithium-ion batteries. Further referring to Comparative Examples 1-12 to 1-13 and Examples 1-1 to 1-26, as the contents of Compound I and Compound II increase, the corresponding high-temperature storage performance and cycling performance of lithium-ion batteries can be gradually improved. However, when the dosage ratio between Compound I and Compound II is unreasonable,

[0119] it will also lead to a decline in the corresponding improvement effect. It can be seen that only by reasonably synergistically matching Compound I and Compound II can the high-temperature storage performance and cycling performance of lithium-ion batteries be significantly improved.

[0120] Examples 2-1 to 2-9

[0121] Based on the results in Table 1, this corresponding example further explores the effects of other components and dosages on improving the high-temperature cycling, storage and other performances of lithium-ion batteries. Except for adjusting the content A / % of Compound I (Formula I-1), the content B / % of Compound II (Formula II-1), and the type and content F / % of carbonate according to Table 2, the remaining parameters are the same as those in Example 1-11.

[0122] According to the above test methods, the high-temperature storage performance (high-temperature storage thickness expansion rate, %) and cycling performance (cycling capacity retention rate, %) of the lithium-ion batteries prepared by Examples 2-1 to 2-9 were tested respectively. The results are shown in Table 2:

[0123] Table 2

[0124]

[0125] The results presented in Table 2 show that, referring to Examples 1-11 and Examples 2-1 to 2-9, further adding carbonate substances to the electrolyte and using them in combination with the compounds of Formula I and the compounds of Formula II can further improve the high-temperature storage performance and cycling performance of the lithium-ion battery; at the same time, further referring to Examples 2-1 to 2-9, although the addition of carbonate substances can further improve the high-temperature storage and cycling performance of the battery, but as the content of carbonate substances increases, the corresponding performance improvement gradually decreases. It can be seen that the dosage of carbonate substances in the electrolyte will further have a greater impact on the performance improvement effect. Therefore, in the scheme of further adding carbonate substances to the electrolyte, controlling the dosage of carbonate substances within a reasonable range can make the improvement effect of the high-temperature storage and cycling performance of the battery better.

[0126] It can be understood that this application is described through some embodiments. As is known to those skilled in the art, without departing from the scope of this application, various changes or equivalent substitutions can be made to these features and embodiments. Additionally, under the teaching of this application, these features and embodiments can be modified to adapt to specific situations and materials without departing from the scope of this application. Therefore, this application is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by this application.

Claims

1. A non-aqueous electrolyte, characterized in that: The non-aqueous electrolyte comprises: a compound of formula I and a compound of formula II; Wherein, in Formula I, R 1 , R 2 , R 3 and R 4 Each is independently selected from any one of a fluorine atom, a difluorophosphoryloxy group, a methylsulfonic acid group, and a trifluoromethylsulfonic acid group; in Formula II, R 5 , R 6 , R 7 and R 8 Each is independently selected from any one of a fluorine atom, a trifluoromethyl group, and a C1-C3 alkylsulfonic acid group substituted with or without a fluorine atom; Based on the total mass of the non-aqueous electrolyte, the mass percentage of the compound of formula I is A, and the mass percentage of the compound of formula II is B, wherein A satisfies: 0.01%≤A≤10%, B satisfies: 0.05%≤B≤5%, and A / B satisfies: 0.01≤A / B≤50.

2. The non-aqueous electrolyte according to claim 1, characterized in that The non-aqueous electrolyte satisfies at least one of the following conditions (1) to (2): (1) A satisfies: 0.06% ≤ A ≤ 5%; (2) A / B satisfies: 0.05≤A / B≤50.

3. The non-aqueous electrolyte according to claim 1, characterized in that The non-aqueous electrolyte satisfies at least one of the following conditions (3) to (4): (3)0.1％≤A≤5％； (4)0.05％≤B≤3.4％。 4. The non-aqueous electrolyte according to claim 1, characterized in that 0.1％≤B≤3％。 5. The non-aqueous electrolyte according to claim 1, characterized in that The compound of formula I includes at least one of the following compounds of formula I-1 to formula I-9:

6. The non-aqueous electrolyte according to claim 1, characterized in that The compound of formula II includes at least one of the following compounds of formula II-1 to formula II-9:

7. The non-aqueous electrolyte according to claim 1, characterized in that The non-aqueous electrolyte also includes a carbonate substance; the carbonate substance includes: at least one of vinylene carbonate, ethylene carbonate or difluoroethylene carbonate; based on the total mass of the non-aqueous electrolyte, the mass percentage of the carbonate substance is F, and F satisfies: 0.1%≤F≤5%.

8. The non-aqueous electrolyte according to claim 7, characterized in that The ratio F / (A+B) between the mass percentage F of the carbonate substance, the mass percentage A of the compound of formula I and the mass percentage B of the compound of formula II satisfies the following relationship: 0.01≤F / (A+B)≤50.

9. The non-aqueous electrolyte according to claim 8, characterized in that 0.1≤F / (A+B)≤5.

10. An electrochemical device, characterized in that: The electrochemical device comprises: a positive electrode, a negative electrode and the non-aqueous electrolyte according to any one of claims 1 to 9, the positive electrode comprises a positive electrode collector and a positive electrode active material layer arranged on at least one surface of the positive electrode collector, the positive electrode active material layer comprises a positive electrode active material, and the positive electrode active material comprises a nickel-cobalt-manganese-based transition metal oxide.

11. An electronic device, characterized in that: The electronic device comprises the electrochemical device according to claim 10.

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