Electrolyte additive, electrolyte and application thereof

Abstract

The invention relates to an electrolyte additive which is a borate compound with a structure as shown in a formula I. M is Li, Na or K; the borate compound as shown in the formula I at least comprises a heterocyclic ring without B, X1, X2, X3 and X4 are respectively and independently selected from O, O-Y or NR5, an O atom or an N atom is connected with B, Y is selected from carbonyl, C1-C4 alkylene or sulfuryl, and R5 is a hydrogen atom or C1-C4 alkyl; r < 1 >, R < 2 >, R < 3 > and R < 4 > are respectively and independently selected from a 5-to 10-membered heterocyclic ring, a C1-C4 alkyl group or a C1-C4 halogenated alkyl group; and / or B is bonded with X1, X2, R1 and R2 to form a 4-10-membered monoring or bicyclic ring, and / or B is bonded with X3, X4, R3 and R4 to form a 4-10-membered monoring or bicyclic ring. According to the electrolyte additive, heterocyclic rings are introduced into a borate structure, so that the high-temperature storage performance and the cycle performance of the battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolyte additives, and in particular to an electrolyte additive and an electrolyte and applications thereof. Background Art

[0002] In recent years, lithium batteries have become the most promising new generation of energy storage devices due to their significant advantages such as high energy density, high power density, long cycle life and green environmental protection, and the explosive growth of the new energy market will continue to drive the growth of lithium battery demand. With the growing demand for high energy density batteries in portable electronic devices, new energy vehicles and large-scale power grid energy storage equipment, insufficient battery life is the biggest obstacle to their large-scale application. Therefore, improving the energy density of lithium batteries is the biggest guarantee for improving consumers' recognition and purchasing power of new energy equipment.

[0003] High energy density lithium-ion batteries need to use high nickel layered transition metal oxide materials (such as lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide), high voltage layered transition metal oxide materials (such as high voltage lithium cobalt oxide, high voltage lithium nickel cobalt manganese oxide) or high voltage spinel lithium nickel manganese oxide materials as positive electrode active materials. These positive electrode active materials have strong oxidizing properties and easily lead to oxidative decomposition of the electrolyte.

[0004] Gas is generated, causing the battery to swell and the cycle life to decline. In order to improve the performance of these high energy density lithium-ion batteries, it has been reported that some additives that can form a protective film on the surface of these positive active materials are used, such as unsaturated bond-containing phosphates (such as tripropargyl phosphate) and unsaturated bond-containing sulfonates (such as 1,3-propylene sultone).

[0005] However, the protective film formed by the prior art positive electrode film-forming additives has poor ionic conductivity, which will lead to increased internal resistance of the battery and fail to meet the requirements of high-rate discharge and low-temperature discharge. Therefore, it is necessary to seek electrolyte additives that can form positive electrode protective films with good ionic conductivity. Summary of the invention

[0006] The problem to be solved by the present invention is to provide an electrolyte additive that can form a positive electrode protective film with high ion conductivity.

[0007] In view of the above problems, the object of the present invention is to provide an electrolyte additive and an electrolyte and applications thereof.

[0008] In order to solve the above problems, the technical solution of the present invention is as follows:

[0009] The present application provides an electrolyte additive, wherein the electrolyte additive is a borate compound having a structure shown in Formula I,

[0010]

[0011] M is Li, Na or K; and the borate compound represented by Formula I contains at least one heterocyclic ring without B, X1, X2, X3 and X4 are each independently selected from O, OY or NR5, wherein the O atom or the N atom is connected to B, Y is selected from a carbonyl group, a C1-C4 alkylene group or a sulfonyl group, and R5 is a hydrogen atom or a C1-C4 alkyl group;

[0012] The R1, R2, R3 and R4 satisfy one of the following conditions:

[0013] i, R1, R2, R3 and R4 are each independently selected from a 5-10 membered heterocycle, a C1-C4 alkyl group or a C1-C4 haloalkyl group;

[0014] ii. B is bonded to X1, X2, R1, and R2 to form a 4-10-membered monocyclic or bicyclic ring, and R3 and R4 are each independently selected from a 5-10-membered heterocyclic ring, a C1-C4 alkyl group, or a C1-C4 haloalkyl group;

[0015] iii. B is bonded with X3, X4, R3 and R4 to form a 4-10 membered monocyclic or bicyclic ring, and R1 and R2 are each independently selected from a 5-10 membered heterocyclic ring, a C1-C4 alkyl group or a C1-C4 haloalkyl group;

[0016] iiii. B bonds with X1, X2, R1, and R2 to form a 4-10-membered monocyclic or bicyclic ring, and B bonds with X3, X4, R3, and R4 to form a 4-10-membered monocyclic or bicyclic ring.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The electrolyte additive of the present invention contains heterocyclic structures such as pyridine, pyrazine, pyrimidine, pyrrole, oxazole, thiophene, thiazole, furan, etc., wherein the N, S or O atoms on the heterocyclic ring can undergo complexation with the transition metal elements in the positive electrode active material, so that the additive is adsorbed on the surface of the positive electrode active material to form a uniform protective film, inhibiting the decomposition reaction of the electrolyte on the surface of the positive electrode active material, thereby significantly improving the high temperature storage performance and cycle performance of the battery.

[0019] 2. The electrolyte additive of the present invention contains a borate structure, and the protective film formed by adsorption on the surface of the positive electrode active material has good ion conductivity, which can effectively avoid the problem of increased internal resistance of the battery due to the presence of the protective film, and can meet the requirements of high-rate discharge and low-temperature discharge.

[0020] 3. The electrolyte additive of the present invention introduces heterocycles into the borate structure to form a positive electrode protective film with high ionic conductivity. The synergistic effect of the two not only improves the high-temperature storage performance and cycle performance of the battery, but also meets the requirements of high-rate discharge and low-temperature discharge.

[0021] 4. The preparation method of the electrolyte additive of the present invention is simple and easy, the raw material cost is low, and it is suitable for large-scale production. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and technical effect of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention is described clearly and completely. The embodiments described below are part of the embodiments of the present invention, not all of them. In combination with the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The electrolyte additive of the present invention contains a borate with a heterocyclic structure. The heterocyclic structure containing N, S or O elements in the additive molecule can undergo complexation with the transition metal element in the positive electrode active material, so that the additive can be effectively adsorbed on the surface of the positive electrode active material to form a protective layer. The borate in the additive molecule can dissociate lithium ions or sodium ions, so that the protective layer has good lithium ion and sodium ion transmission capabilities, ensuring that the battery has a lower impedance.

[0024] As used above and throughout this specification, the following terms shall have the following meanings unless otherwise specified herein:

[0025] Sulfacyl means -S(=O)2-;

[0026] An alkylene group refers to a group derived from a branched or straight-chain saturated aliphatic alkane by removing two hydrogen atoms, and the removed hydrogen atoms may be derived from the same carbon atom or different carbon atoms; the alkylene group described in the present application is preferably -CH2-, -CH(CH3)- or -C(CH3)2-.

[0027] The alkyl group described in the present application can be a straight chain or a branched chain alkyl group. C1-C4 alkyl groups refer to all alkyl groups having 1 to 4 carbon atoms, i.e., CH3-, CH3CH2-, CH3CH2CH-, (CH3)2CH-, CH3CH2CH2 CH2-, CH3CH2CH(CH3)-, and (CH3)3C-, etc.

[0028] The term "halogen" in the term "haloalkyl" as used herein refers to any radiation stable atom in column 7 of the periodic table, such as fluorine, chlorine, bromine or iodine, and fluorine and chlorine are preferred. The haloalkyl described herein may be a straight chain or branched chain haloalkyl.

[0029] When it is said that two R groups are bonded together with the atoms to which they are attached (e.g., B, X1, X2) to form a ring (e.g., a borate ester ring or a boron nitrogen heterocycle), each R group in the ring is not limited by the definition of the R group when it is not a ring. For example, when B, X1, X2, R1 and R2 are bonded to form a 4-10 membered monocyclic or bicyclic ring, the substructure has the following structure:

[0030]

[0031] Wherein ring A is a 4-10 membered monocyclic or bicyclic ring as described, the monocyclic ring is a boroheterocyclic ring, the bicyclic ring is a boroheterocyclic ring substituted with a heterocyclic ring or an aromatic ring, or a borohetero-fused ring.

[0032] In the present application, a boron heterocycle refers to a monocyclic heterocycle containing one or more boron atoms in the ring, preferably a monocyclic heterocycle containing one boron atom. A boron heterocyclic condensed ring refers to a condensed heterocyclic ring formed by condensing a boron heterocycle with a heterocyclic ring or an aromatic ring.

[0033] In order to better understand the above technical solution, the present invention is further described in detail below.

[0034] In a first aspect, in a specific embodiment of the present invention, the present invention provides an electrolyte additive, wherein the electrolyte additive is a borate compound having a structure shown in Formula I,

[0035]

[0036] Wherein, M is Li, Na or K; and the borate compound represented by Formula I contains at least one heterocyclic ring without B, X1, X2, X3 and X4 are each independently selected from O, OY or NR5, wherein the O atom or the N atom is connected to B, Y is selected from a carbonyl group, a C1-C4 alkylene group or a sulfonyl group, and R5 is a hydrogen atom or a C1-C4 alkyl group;

[0037] The R1, R2, R3 and R4 satisfy one of the following conditions:

[0038] i, R1, R2, R3 and R4 are each independently selected from a 5-10 membered heterocycle, a C1-C4 alkyl group or a C1-C4 haloalkyl group;

[0039] ii. B is bonded to X1, X2, R1, and R2 to form a 4-10-membered monocyclic or bicyclic ring, and R3 and R4 are each independently selected from a 5-10-membered heterocyclic ring, a C1-C4 alkyl group, or a C1-C4 haloalkyl group;

[0040] iii. B is bonded with X3, X4, R3 and R4 to form a 4-10 membered monocyclic or bicyclic ring, and R1 and R2 are each independently selected from a 5-10 membered heterocyclic ring, a C1-C4 alkyl group or a C1-C4 haloalkyl group;

[0041] iiii. B bonds with X1, X2, R1, and R2 to form a 4-10-membered monocyclic or bicyclic ring, and B bonds with X3, X4, R3, and R4 to form a 4-10-membered monocyclic or bicyclic ring.

[0042] In some embodiments of the present application, B is bonded to X1, X2, R1, R2 to form a 4-10-membered monocyclic ring or B is bonded to X3, X4, R3, R4 to form a 4-10-membered monocyclic ring, which is a substituted or unsubstituted boron heterocycle. In some embodiments of the present application, the boron heterocycle is a boronate ester ring or a boron nitrogen heterocycle; in some embodiments of the present application, the boronate ester ring is a boronate ester ring formed by boric acid and a hydroxyl, carboxyl, sulfonic acid or phosphoric acid-containing compound. In some embodiments of the present application, the boronate ester ring is one selected from the following structures:

[0043]

[0044] In some embodiments of the present application, when B is bonded with X1, X2, R1, and R2 to form a 4-10 membered monocyclic ring and / or B is bonded with X3, X4, R3, and R4 to form a 4-10 membered monocyclic ring, R1 and R2 together form a group -R8-R7-R9-, wherein R7 is (CR 11 R 12 ) n group, n=an integer of 0-2, R8 and R9 are each independently selected from substituted or unsubstituted C1-C4 alkylene, carbonyl or sulfonyl, R 11 and R 12 Each is independently selected from a hydrogen atom or a C1-C4 alkyl group; and / or, R3 and R4 together form a group -R8-R7-R9-, wherein R7 is (CR 11 R 12 ) n group, n=an integer of 0-2, R8 and R9 are each independently selected from substituted or unsubstituted C1-C4 alkylene, carbonyl or sulfonyl, R 11 and R 12 Each is independently selected from a hydrogen atom or a C1-C4 alkyl group.

[0045] In some embodiments of the present application, the bicyclic ring is a 4-10 membered bicyclic ring; preferably a 4-10 membered boron heterocyclic ring and a heterocyclic ring or an aromatic ring formed by a boron heterocyclic ring or a heterocyclic ring substituted by a heterocyclic ring or an aromatic ring. In some embodiments of the present application, the boron heterocyclic ring is selected from a borate ester ring or a boron nitrogen heterocyclic ring. In some embodiments of the present application, the bicyclic ring is formed by the reaction of boric acid with a heterocyclic or aromatic ring compound containing a hydroxyl group, a carboxyl group, a sulfonic acid group or a phosphate group. In some embodiments of the application, the heterocyclic ring is preferably a heteroaromatic ring, preferably selected from one of pyridine, pyrrole, pyrazine, pyrimidine, oxazole, thiophene, thiazole or furan, and the aromatic ring is selected from a benzene ring.

[0046] In some embodiments of the present application, the bicyclic ring is selected from one of the following structures:

[0047]

[0048] In some embodiments of the present application, when B is bonded to X1, X2, R1, R2 to form a 4-10 membered bicyclic ring and / or B is bonded to X3, X4, R3, R4 to form a 4-10 membered bicyclic ring, R1 and R2 together form a 5-10 membered heterocyclic ring or aromatic ring or together form a group Among them, R 10 is a 5-10 membered heterocyclic or aromatic ring; and / or, R3 and R4 together form a 5-10 membered heterocyclic or aromatic ring or together form a group Among them, R 10 It is a 5-10 membered heterocyclic ring or aromatic ring.

[0049] In some embodiments of the present application, the substituted or unsubstituted C1-C4 alkylene group is selected from one of methylene, ethylene, propylene, butylene, isopropylene or tert-butylene.

[0050] In some embodiments of the present application, the monocyclic or bicyclic ring may be substituted by one or more of the following substituents: C1-C4 alkyl, C1-C4 haloalkyl, halogen, cyano, alkoxy and amino.

[0051] In some embodiments of the present application, the 5-10 membered heterocycle is a 5-10 membered heteroaromatic ring, preferably, the 5-10 membered heteroaromatic ring is selected from one of pyrridine, pyrrole, pyrazine, pyrimidine, oxazole, thiophene, thiazole or furan; and / or,

[0052] The C1-C4 alkyl group is selected from one of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl; and / or,

[0053] The C1-C4 haloalkyl group is selected from 2-fluoroethyl, 2,2-difluoroethyl, 1,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-fluoropropyl, 2-fluoropropyl, 2,2-difluoropropyl, 1,3-difluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 4-fluorobutyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl or 2,2,3,3,tetrafluorobutyl.

[0054] In some embodiments of the present application, the monocyclic ring is selected from one of the following structures:

[0055]

[0056] In some embodiments of the present application, the electrolyte additive contains one or more of the following compounds:

[0057]

[0058]

[0059]

[0060]

[0061] In a second aspect, the present application provides an electrolyte additive, wherein the electrolyte additive contains a borate compound represented by formula I,

[0062]

[0063] Wherein, M is Li, Na or K; and the borate compound represented by Formula I contains at least one heterocyclic ring without B, X1, X2, X3 and X4 are each independently selected from O or NR5, wherein R5 is a hydrogen atom or a C1-C4 alkyl group;

[0064] Wherein, R1 and R2 are each independently selected from a 5-10 membered heterocycle, a C1-C4 alkyl group, a C1-C4 haloalkyl group or a -C y -R6, where C y R1 and R2 are selected from carbonyl, C1-C4 alkylene or sulfonyl, R6 is selected from 5-10 membered heterocycle, C1-C4 alkyl or C1-C4 haloalkyl; or, R1 and R2 together form a 5-10 membered heterocycle or aromatic ring, or form a group -R8-R7-R9- or together form a group Wherein, R7 is selected from a 5-10 membered heterocyclic ring or an aromatic ring or (CR 11 R 12 ) n group, n=an integer of 0-2, R8 and R9 are each independently selected from a carbonyl group, a C1-C4 alkylene group or a sulfonyl group, R 11 and R 12 Each is independently selected from a hydrogen atom or a C1-C4 alkyl group, R 10 is selected from a 5-10 membered heterocyclic ring or an aromatic ring;

[0065] R3 and R4 are each independently selected from a 5-10 membered heterocycle, a C1-C4 alkyl group, a C1-C4 haloalkyl group or a -C y -R6, where C y R3 and R4 are selected from carbonyl, C1-C4 alkylene or sulfonyl, R6 is selected from 5-10 membered heterocycle, C1-C4 alkyl or C1-C4 haloalkyl; R3 and R4 together form a 5-10 membered heterocycle or aromatic ring, or together form a group -R8-R7-R9- or together form a group Wherein, R7 is selected from a 5-10 membered heterocyclic ring or an aromatic ring or (CR 11 R 12 ) n group, n=an integer of 0-2, R8 and R9 are each independently selected from a carbonyl group, a C1-C4 alkylene group or a sulfonyl group, R 11 and R 12 Each is independently selected from a hydrogen atom or a C1-C4 alkyl group, R 10 Selected from 5-10 membered heterocyclic ring or aromatic ring.

[0066] In some embodiments of the present application, the substituted or unsubstituted C1-C4 alkylene group is selected from one of methylene, ethylene, propylene, butylene, isopropylene or tert-butylene.

[0067] In some embodiments of the present application, the heterocyclic ring or aromatic ring may be substituted by one or more of the following substituents: C1-C4 alkyl, C1-C4 haloalkyl, halogen, cyano, alkoxy and amino.

[0068] In some embodiments of the present application, the heterocycle is a 5-10 membered heterocycle, preferably the 5-10 membered heterocycle is a 5-10 membered heteroaromatic ring, more preferably one selected from pyrrole, pyrrole, pyrazine, pyrimidine, oxazole, thiophene, thiazole or furan; and / or,

[0069] The C1-C4 alkyl group is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl and tert-butyl; and / or,

[0070] The C1-C4 haloalkyl group is selected from 2-fluoroethyl, 2,2-difluoroethyl, 1,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-fluoropropyl, 2-fluoropropyl, 2,2-difluoropropyl, 1,3-difluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 4-fluorobutyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl or 2,2,3,3,tetrafluorobutyl.

[0071] In some embodiments of the present application, the electrolyte additive is selected from one or more of Additive 1, Additive 2, Additive 3, Additive 4, Additive 5, Additive 6, Additive 7, Additive 8, Additive 9, Additive 10, Additive 11, Additive 12, Additive 13, Additive 14, Additive 15, Additive 16, Additive 17, Additive 18, Additive 19, Additive 20, Additive 21, Additive 22, Additive 23, Additive 24, Additive 25, Additive 26, Additive 27, Additive 28, Additive 29, Additive 30, Additive 31, Additive 32, Additive 33, Additive 34, Additive 35, Additive 36, Additive 37, Additive 38, Additive 39, Additive 40, Additive 41, Additive 42, Additive 43, Additive 44 and Additive 45.

[0072] In a third aspect, the present application also provides an electrolyte, which includes an electrolyte salt, a solvent and the above-mentioned electrolyte additive.

[0073] In some embodiments of the present application, based on the mass of the electrolyte, the mass percentage of the electrolyte additive is 0.1-5%.

[0074] In some embodiments of the present application, the solvent is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate and propyl propionate.

[0075] In some embodiments of the present application, the electrolyte salt includes a lithium salt or a sodium salt;

[0076] Preferably, the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide.

[0077] Preferably, the sodium salt is selected from one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(trifluoromethylsulfonyl)imide and sodium bis(trifluoromethylsulfonyl)imide.

[0078] In a fourth aspect, the present application further provides a battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte is an electrolyte containing the above-mentioned electrolyte additive or the above-mentioned electrolyte;

[0079] Preferably, the battery is a lithium ion battery, a sodium ion battery or a potassium ion battery.

[0080] The compounds of the present invention can be prepared by a variety of synthetic methods known to those skilled in the art, including the specific embodiments exemplified in the examples, embodiments formed by combining them with other chemical syntheses, and equivalent substitutions known to those skilled in the art, and preferred embodiments include but are not limited to the embodiments described herein.

[0081] Reagents:

[0082] Lithium hydroxide, boric acid, 2-hydroxypyridine, 2-hydroxymethylpyrimidine, 2-pyridinemethanol, 2-pyridinesulfonic acid, 2-hydroxymethylpyrazine, 2-aminopyridine, 2,3-pyridinedicarboxylic acid, 2,3-pyrazine dimethanol, 4-pyridinephosphoric acid, oxalic acid, methanedisulfonic acid, trifluoroacetic acid, 2-pyrazinecarboxylate, pinacol, dimethylmalonic acid, 4-pyrimidinecarboxylic acid, 2,2,2-trifluoroethanol, N,N'-dimethylethylenediamine, pyrrole-2-carboxylic acid, oxazole-5-carboxylic acid, 2-thiophenemethanol, furan-2,3-carboxylic acid, benzyl alcohol, phthalic acid, etc. were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0083] LiNi 0.8 Co 0.1 Mn 0.1 O2 was purchased from Hubei Rongbai Lithium Battery Materials Co., Ltd.;

[0084] Conductive agent PVDF Binder Purchased from SOLVAY (SHANGHAI) Co., Ltd;

[0085] Artificial graphite was purchased from Tianjin Better New Energy Technology Co., Ltd.

[0086] Hereinafter, the present invention will be described in more detail using various preparation examples, embodiments and comparative examples, but the technical scope of the present invention is not limited to these examples. It should be noted that, unless otherwise specifically stated, all percentages, parts and ratios used in the present invention are based on mass.

[0087] Preparation Example 1

[0088] 30.9 g of boric acid (0.5 mol), 190 g of 2-hydroxypyridine (2 mol) and 12 g of lithium hydroxide (0.5 mol) were dissolved in 500 mL of water, and the water was removed by rotary evaporation at 60° C. After the reaction solution was basically dry, the solid was transferred to a vacuum oven and continued to react at 120° C. for 48 h to obtain a white powder, which was additive 1. The structural formula of additive 1 is as follows:

[0089]

[0090] Preparation Example 2

[0091] The difference between Preparation Example 2 and Preparation Example 1 is that 220 g of 2-hydroxymethylpyrimidine (2 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain Additive 2, wherein the structural formula of Additive 2 is as follows:

[0092]

[0093] Preparation Example 3

[0094] The difference between Preparation Example 3 and Preparation Example 1 is that 218 g of 2-pyridinemethanol (2 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain Additive 3, wherein the structural formula of Additive 3 is as follows:

[0095]

[0096] Preparation Example 4

[0097] The difference between Preparation Example 4 and Preparation Example 1 is that 318 g of 2-pyridinesulfonic acid (2 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain Additive 4, wherein the structural formula of Additive 4 is as follows:

[0098]

[0099] Preparation Example 5

[0100] The difference between Preparation Example 5 and Preparation Example 1 is that 220 g of 2-hydroxymethylpyrazine (2 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those in Preparation Example 1 to obtain Additive 5, wherein the structural formula of Additive 5 is as follows:

[0101]

[0102] Preparation Example 6

[0103] The difference between Preparation Example 6 and Preparation Example 1 is that 188 g of 2-aminopyridine (2 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain Additive 6, wherein the structural formula of Additive 6 is as follows:

[0104]

[0105] Preparation Example 7

[0106] The difference between Preparation Example 7 and Preparation Example 1 is that 167 g of 2,3-pyridinedicarboxylic acid (1 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those in Preparation Example 1 to obtain additive 33, wherein the structural formula of additive 33 is as follows:

[0107]

[0108] Preparation Example 8

[0109] The difference between Preparation Example 8 and Preparation Example 1 is that 140 g of 2,3-pyrazine dimethanol (1 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain additive 34, wherein the structural formula of additive 34 is as follows:

[0110]

[0111] Preparation Example 9

[0112] The difference between Preparation Example 9 and Preparation Example 1 is that 159 g of 4-pyridine phosphoric acid (1 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those in Preparation Example 1 to obtain additive 35, wherein the structural formula of additive 35 is as follows:

[0113]

[0114] Preparation Example 10

[0115] The difference between Preparation Example 10 and Preparation Example 1 is that 83.5 g of 2,3-pyridinedicarboxylic acid (0.5 mol) and 79.5 g of 4-pyridinephosphoric acid (0.5 mol) are used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain additive 36, wherein the structural formula of additive 36 is as follows:

[0116]

[0117] Preparation Example 11

[0118] The difference between Preparation Example 11 and Preparation Example 1 is that 83.5 g of 2,3-pyridinedicarboxylic acid (0.5 mol) and 45 g of oxalic acid (0.5 mol) are used instead of 2-hydroxypyridine, and the other conditions are the same as those in Preparation Example 1 to obtain Additive 37, wherein the structural formula of Additive 37 is as follows:

[0119]

[0120] Preparation Example 12

[0121] The difference between Preparation Example 12 and Preparation Example 1 is that 83.5 g of 2,3-pyridinedicarboxylic acid (0.5 mol) and 88 g of methanedisulfonic acid (0.5 mol) are used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain additive 38, wherein the structural formula of additive 38 is as follows:

[0122]

[0123] Preparation Example 13

[0124] The difference between Preparation Example 13 and Preparation Example 1 is that 83.5 g of 2,3-pyridinedicarboxylic acid (0.5 mol) and 95 g of 2-hydroxypyridine (1 mol) are used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain Additive 20, wherein the structural formula of Additive 20 is as follows:

[0125]

[0126] Preparation Example 14

[0127] The difference between the preparation of Preparation Example 14 and Preparation Example 1 is that 83.5 g of 2,3-pyridinedicarboxylic acid (0.5 mol) and 114 g of trifluoroacetic acid (1 mol) are used instead of 2-hydroxypyridine, and the drying conditions in the vacuum oven are changed to: continue the reaction at 60° C. for 8 h, gradually increase the temperature to 80° C. and 100° C., and dry for 12 h respectively. The other conditions are the same as those in Preparation Example 1 to obtain Additive 21, wherein the structural formula of Additive 21 is as follows:

[0128]

[0129] Preparation Example 15

[0130] The difference between Preparation Example 15 and Preparation Example 1 is that 45 g of oxalic acid (0.5 mol) and 124 g of 2-carboxylic acid pyrazine (1 mol) are used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain additive 22, wherein the structural formula of additive 22 is as follows:

[0131]

[0132] Preparation Example 16

[0133] The difference between Preparation Example 16 and Preparation Example 1 is that 59 g of pinacol (0.5 mol) and 95 g of 2-hydroxypyridine (1 mol) are used instead of 2-hydroxypyridine, and the other conditions are the same as those in Preparation Example 1 to obtain additive 23, wherein the structural formula of additive 23 is as follows:

[0134]

[0135] Preparation Example 17

[0136] The difference between Preparation Example 17 and Preparation Example 1 is that 66 g of dimethylmalonic acid (0.5 mol) and 124 g of 4-pyrimidinecarboxylic acid (1 mol) are used instead of 2-hydroxypyridine, and the other conditions are the same as those in Preparation Example 1 to obtain additive 24, wherein the structural formula of additive 24 is as follows:

[0137]

[0138] Preparation Example 18

[0139] The difference between Preparation Example 18 and Preparation Example 1 is that 95 g of 2-hydroxypyridine (1 mol) and 100 g of 2,2,2-trifluoroethanol (1 mol) are used instead of 2-hydroxypyridine, and the other conditions are the same as those in Preparation Example 1 to obtain Additive 8, wherein the structural formula of Additive 8 is as follows:

[0140]

[0141] Preparation Example 19

[0142] The difference between Preparation Example 19 and Preparation Example 1 is that 95 g of 2-hydroxypyridine (1 mol) and 44 g of N,N'-dimethylethylenediamine (0.5 mol) are used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain Additive 25, wherein the structural formula of Additive 25 is as follows:

[0143]

[0144] Preparation Example 20

[0145] The difference between Preparation Example 20 and Preparation Example 1 is that 222 g of pyrrole-2-carboxylic acid (2 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain Additive 7, wherein the structural formula of Additive 7 is as follows:

[0146]

[0147] Preparation Example 21

[0148] The difference between Preparation Example 21 and Preparation Example 1 is that 226 g of oxazole-5-carboxylic acid (2 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain Additive 16, wherein the structural formula of Additive 16 is as follows:

[0149]

[0150] Preparation Example 22

[0151] The difference between Preparation Example 22 and Preparation Example 1 is that 228 g of 2-thiophene methanol (2 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain additive 17, wherein the structural formula of additive 17 is as follows:

[0152]

[0153] Preparation Example 23

[0154] The difference between Preparation Example 23 and Preparation Example 1 is that 156 g of furan-2,3-carboxylic acid (1 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain additive 39, wherein the structural formula of additive 39 is as follows:

[0155]

[0156] Preparation Example 24

[0157] The difference between Preparation Example 24 and Preparation Example 1 is that 216 g of benzyl alcohol (2 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain additive 46, wherein the structural formula of additive 46 is as follows:

[0158]

[0159] Preparation Example 25

[0160] The difference between Preparation Example 25 and Preparation Example 1 is that 166 g of phthalic acid (1 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain additive 47, wherein the structural formula of additive 47 is as follows:

[0161]

[0162] Preparation Example 26

[0163] The difference between the preparation of Preparation Example 26 and Preparation Example 1 is that 62 g of ethylene glycol (1 mol) is used instead of 2-hydroxypyridine, and the other conditions are the same as those of Preparation Example 1 to obtain additive 48, wherein the structural formula of additive 48 is as follows:

[0164]

[0165] Example 1

[0166] 1. Battery production

[0167] 1.1 Preparation of positive electrode

[0168] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, Carbon black conductive agent PVDF Binder The mixture was put into a double planetary mixer at a weight ratio of 96.5:1.5:2. The total weight of the positive electrode active material, carbon black conductive agent and binder was 1 kg. 0.5 kg of N-methylpyrrolidone (NMP) was added and stirred thoroughly and filtered through a filter to obtain a positive electrode material slurry with a solid content of 65%. The slurry was then coated on both sides of an aluminum foil with a thickness of 12 μm using an extrusion coater. After baking and hot rolling, a positive electrode plate was obtained. The surface density of the single-sided coating of the positive electrode plate was 20 mg / cm 2 The single-side coating thickness is 60 μm, and the obtained positive electrode plate is placed in a vacuum oven at 120° C. and dried for 24 h to obtain a positive electrode.

[0169] 1.2 Preparation of negative electrode

[0170] The negative electrode active material artificial graphite, carbon black conductive agent Sodium carboxymethyl cellulose (CMC) was mixed in a weight ratio of 97:1.5:1.5 and then put into a double planetary mixer. The total weight of the negative electrode active material, carbon black conductive agent and sodium carboxymethyl cellulose was 1 kg. 0.8 kg of deionized water (DIW) was added. After fully stirring, 1% of the total weight of the negative electrode material solids and 50% of styrene-butadiene rubber emulsion (SBR) was added. After continuing to stir, the mixture was filtered through a filter to obtain a negative electrode material slurry with a solid content of 45%. The slurry was then applied to both sides of a copper foil with a thickness of 6 μm using an extrusion coater. After baking and hot rolling, a negative electrode plate was obtained. The surface density of the single-sided coating of the negative electrode plate was 13 mg / cm 2 The single-side coating thickness is 80 μm, and the obtained negative electrode plate is placed in a vacuum oven at 100°C and dried for 24 hours to obtain a negative electrode.

[0171] 1.3 Preparation of dry cells

[0172] The positive plate, the negative plate and the PE separator coated with a commercially available 2μm boehmite coating on both sides of a 9μm thick polyethylene porous film are cut into a certain shape, wherein the size of the active material area on the positive plate is 48mm×44mm, the size of the active material area on the negative plate is 52mm×46mm, the size of the separator is 56mm×50mm, and the current collector lead-out parts are respectively reserved on the positive plate and the negative plate; then, they are stacked layer by layer in the manner of negative plate, separator, positive plate, separator, negative plate, ..., with a total of 18 positive plates and 19 negative plates, the outermost layer being the negative plate; then, the current collector lead-out parts of the positive plates are welded together with an ultrasonic welder, and the positive ears are welded on, and the current collector lead-out parts of the negative plates are welded together with an ultrasonic welder, and the negative ears are welded on, so as to obtain a laminated body.

[0173] The laminated body is placed in a packaging bag made of two pieces of aluminum-plastic film after being punched out, and the hot melt adhesive on the tab is welded to the packaging bag by hot melting. The tab is led out of the packaging bag, and an air bag and a liquid injection port are left on one side of the packaging bag, so that a dry battery cell is obtained.

[0174] 1.4 Preparation of electrolyte

[0175] Ethylene sulfite and ethyl methyl carbonate are mixed in a volume ratio of 3:7 to obtain a uniform mixture, and then the mixed solvent is dehydrated with an activated 3A molecular sieve to reduce the water content of the mixed solvent to within 20 ppm. Then, lithium hexafluorophosphate (LiPF6) is dissolved in the mixed solvent in a glove box with a dew point below -40°C to prepare an electrolyte with a LiPF6 concentration of 1.2 mol / L. Additive 1 prepared in Preparation Example 1 is added in an amount of 1% by weight of the entire electrolyte to obtain the desired electrolyte.

[0176] 1.5 Preparation of batteries

[0177] In a glove box with a dew point below -40°C, the electrolyte was injected into the dry cell from the injection port. After standing for 24 hours, the injection port outside the airbag was sealed with a vacuum heat sealer, and the gas in the cell was extracted at the same time, thus obtaining an unformed cell. The weight of the unformed cell was weighed and the weight of the dry cell was subtracted to obtain the weight of the injected electrolyte.

[0178] 1.6 Battery Formation

[0179] The battery cell is formed by using a charging and discharging device, firstly charged to 3.6V with a constant current of 0.05C, then sealed with a vacuum heat sealer and the airbag is cut off, then charged to 4.2V with a constant current of 0.2C, then charged at a constant voltage until the current drops to 0.05C, and then discharged to 3.0V with a constant current of 0.2C, thus obtaining a formed battery cell, i.e., the gel electrolyte lithium ion battery of the present invention.

[0180] 2. Battery testing

[0181] 2.1 First discharge capacity test

[0182] At room temperature, the formed battery was charged to 4.2V at a constant current of 1C, then charged at a constant voltage until the current dropped to 0.05C, and then discharged to 3.0V at a constant current of 1C to obtain the first discharge capacity (Ah). Then part of the battery was subjected to high temperature storage test, and the other part of the battery was subjected to charge and discharge cycle test.

[0183] 2.2 Internal resistance test

[0184] Charge the battery to a half-charged state, connect the test fixture to the internal resistance tester, and clamp the positive and negative electrodes of the battery respectively. Test the AC impedance of the battery at 1KHz, which is the internal resistance of the battery.

[0185] 2.3 High temperature storage test

[0186] The battery was charged at room temperature with a constant current of 1C to 4.2V, and then charged at a constant voltage until the current dropped to 0.05C. The battery was then transferred to a 60°C oven for storage for 7 days. The thickness of the test battery was taken out and the thickness expansion rate was calculated compared with the thickness before high-temperature storage, that is, thickness expansion rate = (battery thickness after high-temperature storage - battery thickness before high-temperature storage) / battery thickness before high-temperature storage * 100%;

[0187] After the battery is cooled to room temperature, it is discharged at a constant current of 1C to 3.0V. The obtained discharge capacity is compared with the discharge capacity before high-temperature storage to calculate the capacity retention rate, that is, capacity retention rate = discharge capacity after high-temperature storage / discharge capacity before high-temperature storage * 100%;

[0188] The battery was then charged to 4.2V at a constant current of 1C, then charged at a constant voltage until the current dropped to 0.05C, and then discharged to 3.0V at a constant current of 1C. The discharge capacity obtained was compared with the discharge capacity before high-temperature storage to obtain the capacity recovery rate, that is, capacity recovery rate = discharge capacity after charging and discharging again after high-temperature storage / discharge capacity before high-temperature storage*100%.

[0189] 2.4 Charge and discharge cycle test

[0190] The battery was charged to 4.2V at a constant current of 1C at room temperature (25°C) and high temperature (45°C), then charged at a constant voltage until the current dropped to 0.05C, and then discharged to 3.0V at a constant current of 1C. This cycle was repeated for 1000 times, and the discharge capacity retention rate was calculated by comparing the last discharge capacity with the first discharge capacity.

[0191] 2.5 Hot box test

[0192] Carry out battery heating experiment in accordance with GB / T 31485-2015, place the battery in a temperature box, heat the temperature from room temperature to 130℃±2℃ at a rate of 5℃ / min, and maintain this temperature for 30 minutes. If there is no abnormality in the battery, heat it by 5℃ for 30 minutes each time thereafter, and observe whether the battery is abnormal. For example, continue to heat it to 135℃ and maintain it for 30 minutes, heat it to 140℃ and maintain it for 30 minutes, heat it to 145℃ and maintain it for 30 minutes... until the battery smokes or burns, and record this temperature, which is the thermal runaway temperature.

[0193] The above test results are shown in Table 1.

[0194] Example 2

[0195] The difference from Example 1 is that during the preparation of the electrolyte, Additive 2 is used instead of Additive 1, and the added amount is 2% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0196] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0197] Example 3

[0198] The difference from Example 1 is that during the preparation of the electrolyte, Additive 4 is used instead of Additive 1, and the added amount accounts for 3% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0199] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0200] Example 4

[0201] The difference from Example 1 is that during the preparation of the electrolyte, Additive 5 is used instead of Additive 1, and the added amount accounts for 4% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0202] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0203] Example 5

[0204] The difference from Example 1 is that during the preparation of the electrolyte, Additive 6 is used instead of Additive 1, and the added amount accounts for 5% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0205] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0206] Example 6

[0207] The difference from Example 1 is that, during the preparation of the electrolyte, the amount of additive 1 added accounts for 0.1% of the weight of the entire electrolyte, and the rest is the same as Example 1.

[0208] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0209] Example 7

[0210] The difference from Example 1 is that, during the preparation of the electrolyte, the amount of additive 1 added accounts for 5% of the weight of the entire electrolyte, and the rest is the same as Example 1.

[0211] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0212] Example 8

[0213] The difference from Example 1 is that during the preparation of the electrolyte, Additive 6 is used instead of Additive 1, and the added amount accounts for 2% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0214] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0215] Example 9

[0216] The difference from Example 1 is that during the preparation of the electrolyte, additive 33 is used instead of additive 1, and the added amount accounts for 1% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0217] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0218] Example 10

[0219] The difference from Example 1 is that during the preparation of the electrolyte, the additive 35 is used instead of the additive 1, and the added amount accounts for 1.5% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0220] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0221] Embodiment 11

[0222] The difference from Example 1 is that during the preparation of the electrolyte, additive 37 is used instead of additive 1, and the added amount accounts for 1% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0223] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0224] Example 12

[0225] The difference from Example 1 is that during the preparation of the electrolyte, the additive 21 is used instead of the additive 1, and the added amount accounts for 0.8% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0226] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0227] Embodiment 13

[0228] The difference from Example 1 is that during the preparation of the electrolyte, the additive 22 is used instead of the additive 1, and the added amount accounts for 3.2% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0229] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0230] Embodiment 14

[0231] The difference from Example 1 is that during the preparation of the electrolyte, Additive 7 is used instead of Additive 1, and the added amount accounts for 4% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0232] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0233] Embodiment 15

[0234] The difference from Example 1 is that during the preparation of the electrolyte, additive 17 is used instead of additive 1, and the added amount accounts for 1% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0235] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0236] Example 16

[0237] The difference from Example 1 is that, in the preparation process of the electrolyte, additive 39 is used instead of additive 1, and the added amount accounts for 2% of the weight of the entire electrolyte. Other aspects are the same as Example 1.

[0238] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0239] Comparative Example 1

[0240] The difference from Example 1 is that additive 1 is not added during the preparation of the electrolyte, and the rest is the same as Example 1.

[0241] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0242] Comparative Example 2

[0243] The difference from Example 1 is that, during the preparation of the electrolyte, the amount of additive 1 added accounts for 0.05% of the weight of the entire electrolyte, and the rest is the same as Example 1.

[0244] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0245] Comparative Example 3

[0246] The difference from Example 1 is that, during the preparation of the electrolyte, the amount of additive 1 added accounts for 6% of the weight of the entire electrolyte, and the rest is the same as Example 1.

[0247] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0248] Comparative Example 4

[0249] The difference from Example 1 is that during the preparation of the electrolyte, additive 46 is used instead of additive 1, and the added amount accounts for 1% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0250] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0251] Comparative Example 5

[0252] The difference from Example 1 is that during the preparation of the electrolyte, additive 47 is used instead of additive 1, and the added amount accounts for 1% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0253] Comparative Example 6

[0254] The difference from Example 1 is that during the preparation of the electrolyte, additive 48 is used instead of additive 1, and the added amount accounts for 1% of the weight of the entire electrolyte. The rest is the same as Example 1.

[0255] The battery was tested according to the test method of Example 1, and the test results are shown in Table 1.

[0256] Table 1 Battery performance test results

[0257]

[0258]

[0259] The borate-type additive containing a heterocyclic structure used in Examples 1-16 is selected from one of Preparation Examples 1-23. These additives contain heterocyclic structures such as pyridine, pyrazine, pyrimidine, pyrrole, oxazole, thiophene, thiazole, furan, etc., which can undergo strong complexation with the transition metal ions in the positive electrode active material to form a uniform protective film, inhibiting the decomposition reaction of the electrolyte on the surface of the positive electrode active material, thereby significantly improving the high temperature performance and cycle performance of the battery.

[0260] As shown in Table 1, compared with the electrolyte of Comparative Example 1 without adding the borate additive containing a heterocyclic structure of the present invention, the lithium ion batteries obtained by adding the borate additive containing a heterocyclic structure of the present invention to the electrolyte of Examples 1-16 have significantly improved initial performance, high temperature storage and cycle performance, and safety performance. Among them, the capacity of the lithium ion batteries prepared in Examples 1-16 is about 3Ah, the internal resistance is 6.5-9.3mΩ, the high temperature storage thickness expansion rate is 0.2-3.1%, the high temperature storage capacity retention rate is 95.8-98.2%, the normal temperature cycle capacity retention rate of 1000 cycles is 92.3-93.9%, and the high temperature cycle capacity retention rate is 87.0-90.3%. At the same time, the thermal runaway temperature of the hot box test is also 155-180°C.

[0261] In Comparative Example 2, only 0.05% of additive 1 was added to the electrolyte. The high temperature performance, cycle performance and safety performance of the lithium ion battery prepared were comparable to those of Comparative Example 1, but not as good as those of Example 1. In Comparative Example 3, 6% of additive 1 was added to the electrolyte. Although the thermal runaway temperature of the hot box test was 180°C, the internal resistance of the battery increased significantly, and the high temperature storage and cycle performance were seriously deteriorated. In Comparative Examples 4 and 5, borates containing benzene ring structures were added to the electrolyte. The electrochemical performance was significantly lower than that of Examples 1-16. The thermal runaway temperature of the hot box test was only 140°C, mainly because the benzene ring structure could not complex with the transition metal ions of the positive active material and no protective film was formed. In Comparative Example 6, 1% of additive 26 was added to the electrolyte. Because it did not contain heterocyclic structures other than boron heterocycles, it could not complex with the transition metal ions of the positive active material, so the electrochemical performance and safety performance of the lithium ion battery prepared were basically similar to those of Comparative Example 1.

[0262] In summary, the electrolyte additive of the present invention introduces a heterocycle into the borate structure to form a positive electrode protective film with high ionic conductivity. The synergistic effect of the heterocycle and borate structures not only improves the high-temperature storage performance and cycle performance of the battery, but also meets the requirements of high-rate discharge and low-temperature discharge.

[0263] Although the present application is disclosed as above with preferred embodiments, it is not used to limit the claims. Any person skilled in the art can make several possible changes and modifications without departing from the concept of the present application. Therefore, the protection scope of the present application shall be based on the scope defined by the claims of the present application. The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. All modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention need to be included in the protection scope of the present invention.

Claims

1. An electrolyte additive, characterized in that: The electrolyte additive is a borate compound with a structure shown in Formula I, M is Li, Na or K; and the borate compound represented by Formula I contains at least one heterocyclic ring without B, X1, X2, X3 and X4 are each independently selected from O, OY or NR5, wherein the O atom or the N atom is connected to B, Y is selected from a carbonyl group, a C1-C4 alkylene group or a sulfonyl group, and R5 is a hydrogen atom or a C1-C4 alkyl group; The R1, R2, R3 and R4 satisfy one of the following conditions: i, R1, R2, R3 and R4 are each independently selected from a 5-10 membered heterocycle, a C1-C4 alkyl group or a C1-C4 haloalkyl group; ii. B is bonded to X1, X2, R1, and R2 to form a 4-10-membered monocyclic or bicyclic ring, and R3 and R4 are each independently selected from a 5-10-membered heterocyclic ring, a C1-C4 alkyl group, or a C1-C4 haloalkyl group; iii. B is bonded with X3, X4, R3 and R4 to form a 4-10 membered monocyclic or bicyclic ring, and R1 and R2 are each independently selected from a 5-10 membered heterocyclic ring, a C1-C4 alkyl group or a C1-C4 haloalkyl group; iiii. B bonds with X1, X2, R1, and R2 to form a 4-10-membered monocyclic or bicyclic ring, and B bonds with X3, X4, R3, and R4 to form a 4-10-membered monocyclic or bicyclic ring.

2. The electrolyte additive according to claim 1, characterized in that: The monocyclic ring is a 4-10 membered boron heterocycle; preferably, the boron heterocycle is a 4-10 membered borate ester ring or a boron nitrogen heterocycle; and / or, The bicyclic ring is a boron heterocycle substituted by a 5-10 membered heterocycle or an aromatic ring, or a fused heterocycle formed by a boron heterocycle and a 5-10 membered heterocycle or an aromatic ring; preferably, the boron heterocycle is a borate ester ring or a boron nitrogen heterocycle.

3. The electrolyte additive according to claim 1 or 2, characterized in that: When B is bonded with X1, X2, R1, and R2 to form a 4-10 membered monocyclic ring and / or B is bonded with X3, X4, R3, and R4 to form a 4-10 membered monocyclic ring, R1 and R2 together form a group -R8-R7-R9-, wherein R7 is (CR 11 R 12 ) n group, n=an integer of 0-2, R8 and R9 are each independently selected from substituted or unsubstituted C1-C4 alkylene, carbonyl or sulfonyl, R 11 and R 12 Each is independently selected from a hydrogen atom or a C1-C4 alkyl group; and / or, R3 and R4 together form a group -R8-R7-R9-, wherein R7 is (CR 11 R 12 ) n group, n=an integer of 0-2, R8 and R9 are each independently selected from substituted or unsubstituted C1-C4 alkylene, carbonyl or sulfonyl, R 11 and R 12 Each is independently selected from a hydrogen atom or a C1-C4 alkyl group; And / or, when B is bonded with X1, X2, R1, R2 to form a 4-10 membered bicyclic ring and / or B is bonded with X3, X4, R3, R4 to form a 4-10 membered bicyclic ring, R1 and R2 together form a 5-10 membered heterocyclic ring or aromatic ring or together form a group Among them, R 10 is a 5-10 membered heterocyclic or aromatic ring; and / or, R3 and R4 together form a 5-10 membered heterocyclic or aromatic ring or together form a group Among them, R 10 It is a 5-10 membered heterocyclic ring or aromatic ring.

4. The electrolyte additive according to any one of claims 1 to 3, characterized in that: The monocyclic or bicyclic ring may be substituted by one or more of the following substituents: C1-C4 alkyl, C1-C4 haloalkyl, halogen, cyano, alkoxy and amino; and / or, The 5-10 membered heterocyclic ring is a 5-10 membered heteroaromatic ring, preferably, the 5-10 membered heteroaromatic ring is selected from one of pyrridine, pyrrole, pyrazine, pyrimidine, oxazole, thiophene, thiazole or furan; and / or, The C1-C4 alkyl group is selected from one of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl; and / or, The C1-C4 haloalkyl is selected from 2-fluoroethyl, 2,2-difluoroethyl, 1,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-fluoropropyl, 2-fluoropropyl, 2,2-difluoropropyl, 1,3-difluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 4-fluorobutyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl or 2,2,3,3,tetrafluorobutyl; and / or, The substituted or unsubstituted C1-C4 alkylene group is selected from one of methylene, ethylene, propylene, butylene, isopropylene or tert-butylene.

5. The electrolyte additive according to any one of claims 1 to 4, characterized in that: The monocyclic ring is selected from one of the following structures: And / or, the bicyclic ring is selected from one of the following structures:

6. The electrolyte additive according to any one of claims 1 to 5, characterized in that: The electrolyte additive contains one or more of the following compounds:

7. An electrolyte, characterized in that: The electrolyte comprises an electrolyte salt, a solvent and an electrolyte additive, wherein the electrolyte additive is the electrolyte additive according to any one of claims 1 to 6.

8. The electrolyte according to claim 7, characterized in that Based on the mass of the electrolyte, the mass percentage of the electrolyte additive is 0.1-5%.

9. The electrolyte according to claim 7 or 8, characterized in that The solvent is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate and propyl propionate; And / or, the electrolyte salt is selected from a lithium salt or a sodium salt; preferably, the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide, or the sodium salt is selected from one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(trifluoromethylsulfonyl)imide and sodium bis(fluorosulfonyl)imide.

10. A battery, characterized in that: It comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte is an electrolyte containing the electrolyte additive according to any one of claims 1 to 6 or an electrolyte according to any one of claims 7 to 9; Preferably, the battery is a lithium ion battery, a sodium ion battery or a potassium ion battery.

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