Electrolyte and battery

Abstract

The application relates to the technical field of lithium ion batteries, and provides an electrolyte and a battery. The electrolyte comprises an organic solvent, an electrolyte salt, an additive A and an additive B. The additive A is a tetrafluoroborate salt, the additive B is a bisfluorosulfonylimide salt, the additive A and the additive B synergistically form a protective layer on the surface of a positive electrode, can reduce the side reaction of the positive electrode and the electrolyte, stabilize the structure of the positive electrode, can improve the safety performance of the battery under high temperature, and prolongs the cycle service life of the battery.

Description

Technical Field

[0001] This invention relates to the technical field of lithium-ion batteries, and more specifically to an electrolyte and a battery. Background Technology

[0002] A lithium-ion battery is a rechargeable battery that primarily functions by the movement of lithium ions between the positive and negative electrodes. During charging and discharging, Li+ ions repeatedly insert and extract between the two electrodes: during charging, Li+ ions extract from the positive electrode, pass through the electrolyte, and insert into the negative electrode, leaving the negative electrode in a lithium-rich state; the reverse occurs during discharging. Due to its advantages such as high energy density and long cycle life, lithium-ion batteries are widely used in various electronic products and, in recent years, have also been extensively used in electric vehicles, power tools, and energy storage devices.

[0003] With the improvement of people's living standards and their aspirations for a better life, higher demands are being placed on battery energy density. To improve battery energy density, further increasing the voltage of the positive electrode material in lithium-ion batteries is a common approach. However, as the limiting voltage of the positive electrode material continues to increase, its specific capacity gradually increases, leading to severe deterioration of the battery's high-temperature performance and making it impossible to guarantee long cycle life. Especially at high voltages (>4.5V), during long-term charge-discharge cycles, the volume of the positive electrode material expands, causing severe cracks. Electrolyte enters the interior of the positive electrode material, damaging its structure. Simultaneously, the release of active oxygen further accelerates the oxidative decomposition of the electrolyte. Furthermore, the protective film on the negative electrode surface is continuously damaged, ultimately resulting in severe capacity decay of the battery.

[0004] Currently, oxide coatings are typically used to modify the surface of cathode materials, or cathode materials with different morphologies and structures are prepared. However, these processes are complex, costly, and offer poor protection.

[0005] Therefore, developing a battery with long cycle life and high safety performance is of great significance. Summary of the Invention

[0006] The purpose of this invention is to overcome the aforementioned problems in the prior art and to provide an electrolyte and a battery containing the electrolyte. The electrolyte provided by this invention can improve the safety performance of the battery at high temperatures and extend the battery's cycle life.

[0007] The inventors of this invention discovered that additive A in the electrolyte, due to its unsaturated bonds, can undergo a polymerization reaction on the positive electrode surface to form a protective film, reducing the oxidation rate of the electrolyte on the positive electrode surface, decreasing self-discharge, and the BF4- group is relatively stable and not easily decomposed, thus improving the overall stability of the electrolyte. Additive B, the bis(fluorosulfonyl)imide salt, has a nitrogen atom with a lone pair of electrons as its parent central atom, exhibiting good stability and forming a protective layer on the positive electrode surface, thereby reducing side reactions between the positive electrode and the electrolyte and stabilizing the positive electrode structure. Ultimately, this improves the battery's safety performance at high temperatures and extends its cycle life.

[0008] To achieve the above objectives, the first aspect of the present invention provides an electrolyte comprising an organic solvent, an electrolyte salt, additive A, and additive B;

[0009] Wherein, additive A includes at least one of the compounds shown in formula (I):

[0010] In this context, R1, R2, R3, and R4 are independently selected from at least one of hydrogen, alkane groups having 1-40 carbon atoms, olefin groups having 1-40 carbon atoms, and aryl groups having 6-40 carbon atoms; X is selected from at least one of SH-, N, B, and SiH-; and each of R1, R2, R3, and R4 is independently separated by 0, 1, 2, or 3 R groups. a Instead, the R a The additive is independently selected from halogen, cyano or phenyl; the additive B is a difluorosulfonyl imide salt.

[0011] A second aspect of the present invention provides a battery comprising an electrolyte, wherein the electrolyte is the electrolyte described in the first aspect of the present invention.

[0012] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0013] (1) The electrolyte provided by the present invention can form a protective layer on the surface of the positive electrode, thereby reducing the side reactions between the positive electrode and the electrolyte, stabilizing the positive electrode structure, improving the safety performance of the battery at high temperature, and extending the cycle life of the battery.

[0014] (2) The electrolyte provided by the present invention has a simple preparation process, low cost, and good battery protection effect.

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Detailed Implementation

[0016] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0017] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0018] The first aspect of the present invention provides an electrolyte comprising an organic solvent, an electrolyte salt, additive A, and additive B;

[0019] Wherein, additive A includes at least one of the compounds shown in formula (I):

[0020] In this context, R1, R2, R3, and R4 are independently selected from at least one of hydrogen, alkane groups having 1-40 carbon atoms, olefin groups having 1-40 carbon atoms, and aryl groups having 6-40 carbon atoms; X is selected from at least one of SH-, N, B, and SiH-; and each of R1, R2, R3, and R4 is independently separated by 0, 1, 2, or 3 R groups. a Instead, the R a The additive is independently selected from halogen, cyano or phenyl; the additive B is a difluorosulfonyl imide salt.

[0021] In this invention, additives A and B in the electrolyte are used together to reduce side reactions between the positive electrode and the electrolyte, improve the stability of the electrolyte and positive electrode structure, thereby enhancing the battery's safety performance at high temperatures and extending the battery's cycle life.

[0022] Additive A of the present invention can be prepared by methods known in the art or can be purchased commercially.

[0023] To further improve the safety performance and lifespan of the battery, one or more of the technical features can be further optimized.

[0024] In one example, in formula (I), R1, R2, R3, and R4 are independently selected from at least one of hydrogen, an alkane group having 1-20 carbon atoms (preferably an alkane group having 1-5 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl), an olefin group having 1-20 carbon atoms (preferably an olefin group having 1-5 carbon atoms, vinyl, propenyl, butenyl, pentenyl, isobutylenyl), and an aryl group having 6-26 carbon atoms (e.g., phenyl).

[0025] In one instance, X is selected from SH- or N.

[0026] In one example, additive A is selected from at least one of the compounds shown in formulas I-1 to I-12:

[0027]

[0028] In one example, the content of additive A is 0.01-10 wt% based on the total weight of the electrolyte, for example, 0.01 wt%, 0.1 wt%, 1 wt%, 2 wt%, 5 wt%, 8 wt%, or 10 wt%.

[0029] Preferably, the content of additive A is 0.05-5 wt%, more preferably 0.1-1 wt%, based on the total weight of the electrolyte.

[0030] In this invention, additive A has unsaturated bonds and five-membered rings, and undergoes a polymerization reaction on the positive electrode surface to form a protective film with a three-dimensional network structure, protecting the positive electrode and improving the stability of the electrolyte. Optimizing the specific structure and dosage of additive A can enhance its effectiveness.

[0031] In one example, the difluorosulfonyl imide salt comprises at least one of the compounds shown in formula (II):

[0032] In this context, R5 is selected from at least one of Li, Na, K, Rb, Cs, and Fr.

[0033] In one example, the additive B is selected from at least one of the compounds shown in formulas II-1 to II-6:

[0034]

[0035] In one example, the content of the difluorosulfonamide salt is 0.1-15 wt% based on the total weight of the electrolyte, for example, 0.1 wt%, 1 wt%, 2 wt%, 5 wt%, 8 wt%, 10 wt%, or 15 wt%.

[0036] Preferably, the content of the difluorosulfonamide salt is 1-10 wt%, based on the total weight of the electrolyte.

[0037] In this invention, additive B, bis(fluorosulfonyl)imide salt, can form a protective layer on the positive electrode surface, reducing side reactions between the positive electrode and the electrolyte, and stabilizing the positive electrode structure. Optimizing the specific structure and dosage of additive B can enhance its effectiveness.

[0038] In one example, the electrolyte further includes additive C, which comprises at least one of the compounds shown in formula (III):

[0039] In this context, Y is selected from at least one of O, S, NH-, BH-, PH-, and SiH2-, R6 and R7 are independently selected from at least one of hydrogen, alkane group with 1-40 carbon atoms, olefin group with 1-40 carbon atoms, and aryl group with 6-40 carbon atoms, and n is an integer from 1 to 10.

[0040] In one example, in formula (III), R6 and R7 are independently selected from at least one of hydrogen, an alkane group having 1-20 carbon atoms (preferably an alkane group having 1-5 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl), an olefin group having 1-20 carbon atoms (preferably an olefin group having 1-5 carbon atoms, vinyl, propenyl, butenyl, pentenyl, isobutylenyl), and an aryl group having 6-26 carbon atoms (e.g., phenyl).

[0041] In one instance, Y is selected from at least one of O, S, and PH-.

[0042] In one instance, n is an integer from 1 to 4.

[0043] In one example, the additive C is selected from at least one of the compounds shown in formulas III-1 to III-27:

[0044]

[0045]

[0046] The inventors of this invention discovered that the nitrile functional group (-CN) in additive C reacts with the Co in the positive electrode active material. 3+ With a more negative binding energy, it is easier to accumulate on the positive electrode surface. At the same time, the nitrile functional group coordinates with the high-valence transition metal atoms on the positive electrode surface, and together with the polymer network structure formed by additive A, it works on the positive electrode surface to reduce the side reactions of the positive electrode and the electrolyte.

[0047] In one example, the content of additive C is 0.1-15 wt% based on the total weight of the electrolyte, for example, 0.1 wt%, 1 wt%, 2 wt%, 5 wt%, 8 wt%, 10 wt%, or 15 wt%.

[0048] Preferably, the content of additive C is 1-10 wt% based on the total weight of the electrolyte. A higher preferred amount of additive C can enhance its effectiveness.

[0049] In one example, the electrolyte further includes functional additives. The types of functional additives are not specifically limited and can be selected as needed in the field.

[0050] In one example, the functional additive is selected from at least one of 1,3-propenesulfonate lactone, adiponitrile, succinate, triglycerides, 1,1,3,3-propanetetracarbonyl nitrile, and 1,3,6-hexanetrionitrile.

[0051] In one example, the content of the functional additive is 1-12 wt% based on the total weight of the electrolyte.

[0052] In one example, the organic solvent is selected from at least one of carbonates and their derivatives, carboxylic acid esters and their derivatives, and ethers and their derivatives.

[0053] In this invention, the term "derivative" refers to a compound formed by replacing atoms or groups of atoms in a compound molecule (carbonate, carboxylic acid ester, ether) with other atoms or groups of atoms, such as fluorides formed by replacing atoms or groups of atoms in carbonates, carboxylic acid esters, or ethers with one or more fluorine atoms.

[0054] For example, the carbonate-based non-aqueous organic solvents include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), and fluoroethylene carbonate (FEC).

[0055] For example, the carboxylic acid ester non-aqueous organic solvents include propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate (PP), ethyl propionate (EP), methyl butyrate, and ethyl butyrate.

[0056] For example, the ether-based non-aqueous organic solvents include 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, ethyl propyl ether, and ethylene glycol dimethyl ether.

[0057] In one example, the electrolyte salt is selected from conductive lithium salts, which can be lithium salts commonly used in the field of lithium batteries.

[0058] In one example, the conductive lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium tetrafluorooxalate phosphate (LiOTFP), lithium bis(fluorosulfonyl)imide (LiTFSI), lithium bis(trifluoromethyl)sulfonyl)imide (LiTFSI), lithium difluorobis(oxalate) phosphate (LiDFBP), lithium tetrafluoroborate (LiBF4), lithium bis(oxalate) borate (LiBOB), lithium hexafluoroantimonyate (LiSbF6), lithium hexafluoroarsenate (LiAsF6), lithium 4,5-dicyano-2-trifluoromethyl-imidazolium (LiTDI), lithium di(trifluoromethyl)imide, lithium di(pentafluoroethyl)imide, lithium tri(trifluoromethyl)sulfonyl)methyl, and lithium di(trifluoromethyl)imide.

[0059] In one example, the content of the conductive lithium salt is 10-20 wt% based on the total weight of the electrolyte, for example, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%.

[0060] The electrolyte provided by this invention is used in lithium-ion batteries, which can improve the safety performance of the battery at high temperatures and extend the cycle life of the battery.

[0061] A second aspect of the present invention provides a battery comprising an electrolyte, wherein the electrolyte is the electrolyte described in the first aspect of the present invention.

[0062] In one example, the battery is a lithium-ion battery.

[0063] In one example, the lithium-ion battery further includes a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, and a separator.

[0064] In one example, the positive electrode sheet includes a positive current collector and a positive active material layer coated on one or both surfaces of the positive current collector, the positive active material layer including a positive active material, a conductive agent, and a binder.

[0065] In one example, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material is 80-99.8 wt%, the content of the conductive agent is 0.1-10 wt%, and the content of the binder is 0.1-10 wt%.

[0066] Preferably, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material is 90-99.6 wt%, the content of the conductive agent is 0.2-5 wt%, and the content of the binder is 0.2-5 wt%.

[0067] For example, the positive electrode active material is selected from at least one of transition metal lithium oxide, lithium iron phosphate, and lithium manganese oxide; the chemical formula of the transition metal lithium oxide is Li. 1+x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; M is one or a combination of several of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0068] In one example, the negative electrode sheet includes a negative current collector and a negative active material layer coated on one or both surfaces of the negative current collector, the negative active material layer including a negative active material, a conductive agent, and a binder.

[0069] In one example, based on the total weight of the negative electrode active material layer, the content of the negative electrode active material is 80-99.8 wt%, the content of the conductive agent is 0.1-10 wt%, and the content of the binder is 0.1-10 wt%.

[0070] Preferably, based on the total weight of the negative electrode active material layer, the content of the negative electrode active material is 90-99.6 wt%, the content of the conductive agent is 0.2-5 wt%, and the content of the binder is 0.2-5 wt%.

[0071] For example, the negative electrode active material includes at least one of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, and soft carbon.

[0072] In one example, the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0073] In one example, the adhesive is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0074] In one example, the separator is selected from at least one of polyethylene, polypropylene, multilayer polyethylene-polypropylene, polyethylene-polypropylene blends, polyimide, polyetherimide, polyamide, meta-aramid, para-aramid, and meta-para-aramid blends.

[0075] The battery described in the second aspect of the present invention contains the electrolyte described in the first aspect of the present invention, which improves the safety performance and extends the service life of the battery.

[0076] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0077] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0078] The present invention will now be described in detail with reference to specific embodiments, which are intended to understand rather than limit the invention.

[0079] Example 1

[0080] A lithium-ion battery, comprising the following preparation method:

[0081] (1) Preparation of electrolyte

[0082] (1.1) Components (based on 100% of the total mass of the electrolyte):

[0083] Organic solvents: 6 wt% ethylene carbonate (EC), 6 wt% propylene carbonate (PC), 12 wt% diethyl carbonate (DEC), 35.5 wt% propyl propionate (PP), 7 wt% fluoroethylene carbonate (FEC), totaling 66.5 wt%.

[0084] Conductive lithium salt: Lithium hexafluorophosphate (LiPF6), 13 wt%;

[0085] Additive A: I-4, 0.5 wt%;

[0086] Additive B: II-1, 7 wt%;

[0087] Additive C: III-9, 4 wt%;

[0088] Functional additives: adiponitrile (ADN) 3wt%, 1,3,6-hexanetrionitrile (HTCN) 3wt%, 1,3-propanesulfonyl lactone (PS) 3wt%.

[0089] (1.2) Preparation method

[0090] In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), EC / PC / DEC / PP are mixed evenly. Then, fully dried lithium salt is quickly added to the mixture. After dissolving, FEC is added, followed by additives A, B, C, HTCN, ADN, and PS in sequence. The mixture is then thoroughly mixed to obtain the desired electrolyte.

[0091] (2) Preparation of positive electrode

[0092] Lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), super P (SP), and carbon nanotubes (CNT) were mixed in a mass ratio of 96:2:1.5:0.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until it formed a uniform and fluid positive electrode slurry. The positive electrode slurry was then uniformly coated onto both surfaces of an aluminum foil. The coated aluminum foil was dried, and then rolled and slit to obtain the desired positive electrode sheet.

[0093] (3) Preparation of negative electrode sheet

[0094] The negative electrode active materials, artificial graphite, silicon suboxide, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP), and single-walled carbon nanotubes (SWCNTs), were mixed in a mass ratio of 79.5:15:2.5:1.5:1:0.5. Deionized water was added, and the mixture was stirred in a vacuum mixer to obtain a negative electrode active slurry. The negative electrode active slurry was uniformly coated on both surfaces of a copper foil. The coated copper foil was dried at room temperature and then transferred to an 80°C oven for 10 hours. After cold pressing and slitting, the negative electrode sheet was obtained.

[0095] (4) Preparation of lithium-ion batteries

[0096] The positive electrode sheet from step (2), the negative electrode sheet from step (3), and the separator (polyethylene film) are stacked in the order of positive electrode sheet, separator, and negative electrode sheet, and then wound to obtain a battery cell. The battery cell is placed in an outer packaging aluminum foil, and the electrolyte from step (1) is injected into the outer packaging. After vacuum sealing, settling, formation, shaping, and sorting, a lithium-ion battery is obtained. The charging and discharging range of the battery of this invention is 3.0-4.5V.

[0097] Example 2

[0098] The procedure was carried out in accordance with Example 1, except that the composition of the electrolyte in step (1) was different:

[0099] Organic solvents: 7 wt% ethylene carbonate (EC), 7 wt% propylene carbonate (PC), 14 wt% diethyl carbonate (DEC), 39.9 wt% propyl propionate (PP), 8 wt% fluoroethylene carbonate (FEC), totaling 75.9 wt%.

[0100] Conductive lithium salt: Lithium hexafluorophosphate (LiPF6), 15wt%;

[0101] Additive A: III-1, 0.1 wt%;

[0102] Additive B: II-1, 1 wt%;

[0103] Additive C: III-6, 2wt%;

[0104] Functional additives: adiponitrile (ADN) 2wt%, 1,3,6-hexanetrionitrile (HTCN) 2wt%, 1,3-propanesulfonyl lactone (PS) 2wt%.

[0105] Example 3

[0106] The procedure was carried out in accordance with Example 1, except that the composition of the electrolyte in step (1) was different:

[0107] Organic solvents: 6 wt% ethylene carbonate (EC), 6 wt% propylene carbonate (PC), 11.8 wt% diethyl carbonate (DEC), 30 wt% propyl propionate (PP), 7 wt% fluoroethylene carbonate (FEC), totaling 66.5 wt%.

[0108] Conductive lithium salt: Lithium hexafluorophosphate (LiPF6), 16 wt%;

[0109] Additive A: I-5, 0.2 wt%;

[0110] Additive B: II-1, 5 wt%;

[0111] Additive C: III-22, 6 wt%;

[0112] Functional additives: adiponitrile (ADN) 4wt%, 1,3,6-hexanetrionitrile (HTCN) 4wt%, 1,3-propanesulfonyl lactone (PS) 4wt%.

[0113] Example 4 group

[0114] This set of examples is used to illustrate the effects of structural changes in additive A in the electrolyte;

[0115] Example 4a: Performed as in Example 1, with additive A being I-2;

[0116] Example 4b: Performed as in Example 1, with additive A being I-6;

[0117] Example 4c: The same as in Example 1, with additive A being I-8.

[0118] Example 5 group

[0119] This set of examples is used to illustrate the effects of structural changes in additive C in the electrolyte;

[0120] Example 5a: Performed as in Example 1, with additive C being III-2;

[0121] Example 5b: Performed as in Example 1, with additive C being III-14;

[0122] Example 5c: Performed as in Example 1, with additive C being III-20;

[0123] Example 5d: Performed according to Example 1, with additive C being III-26.

[0124] Example 6 group

[0125] This set of examples is used to illustrate the effect of changing the content of additive A in the electrolyte;

[0126] Example 6a: The procedure was carried out in accordance with Example 1, with additive A accounting for 0.08%;

[0127] Example 6b: The same as in Example 1, but with additive A accounting for 5%.

[0128] Example 7 group

[0129] This set of examples is used to illustrate the effect of changing the content of additive C in the electrolyte;

[0130] Example 7a: The procedure was carried out as in Example 1, with additive C accounting for 0.5%;

[0131] Example 7b: The same as in Example 1, but with additive C accounting for 12%.

[0132] Example 8

[0133] The procedure was carried out in accordance with Example 1, except that additive C was not included.

[0134] Comparative Example 1

[0135] The procedure was carried out in accordance with Example 1, except that additive A was not added.

[0136] Comparative Example 2

[0137] The procedure was carried out in accordance with Example 1, except that additives A, B and C were not added.

[0138] Comparative Example 3 Groups

[0139] The procedure was carried out in accordance with Example 1, except that the content of the additives was changed:

[0140] Comparative Example 3a: The content of additive A is 12%;

[0141] Comparative Example 3b: The content of additive B is 0.05%;

[0142] Comparative Example 3c: The content of additive C is 18%.

[0143] Comparative Example 4

[0144] The procedure was carried out in accordance with Example 1, except that additive A was lithium tetrafluoroborate.

[0145] When the above embodiments and comparative examples do not contain a certain additive, the missing mass percentage is made up with organic solvents to ensure that the mass percentage of other components remains unchanged.

[0146] Test case

[0147] (1) High-temperature cycling performance test at 45℃

[0148] The batteries provided in the examples and comparative examples were subjected to 800 charge-discharge cycles at 45°C and a 1C rate within the charge-discharge cutoff voltage range. The discharge capacity of the first cycle was measured as x1 mAh, and the discharge capacity of the Nth cycle was measured as y1 mAh. The capacity of the Nth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate R1 = y1 / x1. The results are recorded in Table 1.

[0149] (2) 85℃ High Temperature Storage Performance Test

[0150] First, after capacity testing, the battery was allowed to stand for 10 minutes. Then, it was discharged at 0.2C to 3V, allowed to stand for 10 minutes, and then fully charged at 0.5C, cut off at 0.05C, and allowed to stand for 10 minutes. The fully charged voltage, internal resistance, and thickness were tested at 25±5℃. After placing the fully charged battery in an 85℃ oven for 8 hours, the hot battery was removed and its voltage, internal resistance, and thickness were tested. Capacity retention and recovery tests were also performed. The results are recorded in Table 1.

[0151] Table 1

[0152]

[0153] As shown in Table 1, the electrolyte provided in the examples can improve the safety performance of the battery at high temperatures and extend the battery's cycle life.

[0154] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrolyte, characterized by, The electrolyte includes an organic solvent, an electrolyte salt, additive A, and additive B; Wherein, additive A includes at least one of the compounds shown in formula (I): In formula (I), R1, R2, R3, and R4 are independently selected from at least one of hydrogen, alkane groups with 1-40 carbon atoms, olefin groups with 1-40 carbon atoms, and aryl groups with 6-40 carbon atoms; X is selected from at least one of SH-, N, B, and SiH-; and each of R1, R2, R3, and R4 is independently separated by 0, 1, 2, or 3 R groups. a Instead, the R a Independently selected from halogen, cyano, or phenyl; Additive B is a difluorosulfonyl imide salt.

2. The electrolyte according to claim 1, wherein, In formula (I), R1, R2, R3, and R4 are independently selected from at least one of hydrogen, an alkane group having 1-20 carbon atoms, an alkene group having 1-20 carbon atoms, and an aryl group having 6-26 carbon atoms; and / or, The X is selected from SH- or N; and / or, Based on the total weight of the electrolyte, the content of additive A is 0.01-10 wt%.

3. The electrolyte according to claim 1, wherein, The difluorosulfonyl imide salt includes at least one of the compounds shown in formula (II): In formula (II), R5 is selected from at least one of Li, Na, K, Rb, Cs, and Fr; and / or, Based on the total weight of the electrolyte, the content of the difluorosulfonamide salt is 0.1-15 wt%.

4. The electrolyte according to claim 1, wherein, It also includes additive C, which comprises at least one of the compounds shown in formula (III): In formula (III), Y is selected from at least one of O, S, NH-, BH-, PH-, and SiH2-; R6 and R7 are independently selected from at least one of hydrogen, an alkane group with 1-40 carbon atoms, an olefin group with 1-40 carbon atoms, and an aryl group with 6-40 carbon atoms; n is an integer from 1 to 10; and / or, Based on the total weight of the electrolyte, the content of additive C is 0.1-15 wt%.

5. The electrolyte according to any one of claims 1-4, wherein, The additive A is selected from at least one of the compounds shown in formulas I-1 to I-12 below: 。 6. The electrolyte according to any one of claims 1-4, wherein, The additive B is selected from at least one of the compounds shown in formulas II-1 to II-6 below: (II-1) (II-2) (II-3) (II-4) (II-5) (II-6).

7. The electrolyte according to claim 4, wherein, The additive C is selected from at least one of the compounds shown in formulas III-1 to III-27: 。 8. The electrolyte according to any one of claims 1-4, wherein, The electrolyte also includes functional additives; The functional additive is selected from at least one of 1,3-propenesulfonate lactone, adiponitrile, succinate, glyceryl trinitrile, and 1,3,6-hexanetrinitrile; and / or, Based on the total weight of the electrolyte, the content of the functional additive is 1-12 wt%.

9. The electrolyte according to any one of claims 1-4, wherein, The organic solvent is selected from at least one of carbonates and their derivatives, carboxylic acid esters and their derivatives, and ethers and their derivatives; and / or, The electrolyte salt is selected from conductive lithium salts.

10. A battery, characterized in that, The battery includes an electrolyte, which is the electrolyte according to any one of claims 1-9.

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