Electrolyte and battery using same

Abstract

The invention belongs to the field of batteries, and particularly discloses an electrolyte and a battery using the electrolyte. The electrolyte comprises a metal salt and an organic solvent, the electrolyte further comprises an electrolyte additive, and the electrolyte additive comprises a compound shown in the formula (I) and at least one selected from fluoroethylene carbonate, 1, 3-propane sultone, vinylene carbonate, vinylethylene carbonate, ethylene sulfate and lithium difluorophosphate. When the electrolyte additive is added into the electrolyte, the transmission kinetics of lithium ions in the electrolyte can be improved, the cycle performance of a battery applying the electrolyte at high and low temperatures and the storage stability of the battery at high temperature are improved, and meanwhile, the electrolyte additive has a protection effect on a positive electrode; and the oxidation degree of the solvent on the positive electrode is reduced, so that side reactions are reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of batteries, and particularly relates to an electrolyte and a battery using the electrolyte. BACKGROUND

[0002] Lithium ion batteries have the advantages of high voltage, high capacity, no memory effect, long service life, etc., and have been widely used in computers, mobile phones, electronic watches and other portable electronic devices. In the future, they will also have broad development prospects in the fields of smart grid, advanced energy storage and smart buildings. With the continuous expansion of the application range of lithium ion batteries, people have put forward higher requirements for lithium ion batteries: higher energy density and cycle life, higher safety, wider service temperature range, lower self-discharge rate and lower raw material cost.

[0003] Since the cathode of the lithium ion battery uses a high-potential cathode active material and the anode uses a low-potential anode active material, the potential window of the electrolyte is narrower than that of the active material. The electrolyte is exposed to the surface of the cathode and anode electrodes and is easily decomposed. The main salt LiPF6 of the lithium ion battery is easily decomposed under the action of high temperature or trace water to produce HF, which destroys the SEI film and corrodes the electrode material, releases transition metal ions, further promotes the decomposition of the electrolyte, forms a vicious cycle, and causes the performance of the lithium ion battery to deteriorate; in addition, the application of fast charging technology also brings many problems: (1) thermal effect: for single cells, the fast charging condition needs to withstand the heat problem caused by the increase of current. Under fast charging, the temperature difference between the inside and outside of the battery exceeds 10℃, and the uneven distribution of heat and the high temperature will cause a series of problems: the disintegration of the binder, the decomposition of the electrolyte, the loss of the SEI passivation film and lithium dendrites, which directly lead to the reduction of the cycle life of the battery and the safety problems caused by thermal runaway. (2) lithium precipitation effect: under high charging rate, the process of lithium ion insertion into the negative electrode becomes uneven, and lithium will deposit on the surface of the negative electrode because it cannot be timely inserted into the negative electrode graphite layer, and gradually form lithium dendrites. The higher the charging rate, the more lithium dendrites are deposited. The accumulation of lithium dendrites may pierce the separator, causing internal short circuit of the battery and leading to thermal runaway. Lithium dendrites will continuously consume active lithium ions during the growth process, which is irreversible, resulting in the reduction of battery capacity and the reduction of battery service life. SUMMARY

[0004] In order to overcome at least one technical problem existing in the prior art, one of the purposes of the present application is to provide an electrolyte additive which is applied in a battery and can improve the cycle stability of the battery at high and low temperatures and the storage stability of the battery at high temperature, so that the battery can work stably under the condition of high voltage and large change of working environment.

[0005] The second object of the present application is to provide an electrolyte containing the electrolyte additive described above, which can improve the cycle stability at high and low temperatures and the storage stability at high temperature when applied to a battery.

[0006] The third object of the present application is to provide a battery which has good cycle stability at high and low temperatures, and has a high capacity retention rate and a high capacity recovery rate even after being stored at high temperature for one month.

[0007] The fourth object of the present application is to provide an electric device.

[0008] To achieve the above objects, the technical solution adopted by the present application is: The first aspect of the present application provides an electrolyte additive, which comprises an additive A, the additive A being a compound represented by formula (I):

[0009] Formula (I), wherein ring A is selected from a nitrogen-containing five-membered ring substituted or unsubstituted with R1; ring B is selected from , a phenyl ring substituted or unsubstituted with R2; L is selected from nothing, a chemical bond or -O-Si(R4)2-; When L is nothing, ring A is selected from a nitrogen-containing five-membered ring substituted with R1, and ring B is selected from an unsubstituted phenyl ring, ring A and ring B are fused to form a compound represented by the following structure: ; The number of R1 is 1, 2 or 3, each R1 is independently selected from H, F or -SO2F; R2 is selected from C 1~5 alkyl, -CF3 or -SO2N(CF3)2; R3 is selected from C 1~5 alkyl, -CF3 or -Si(CH3)3; R4 is selected from C 1~5 alkyl.

[0010] In some embodiments of the present application, the number of nitrogen atoms in the nitrogen-containing five-membered ring is an integer from 1 to 3.

[0011] In some embodiments of the present application, ring A is selected from imidazole or .

[0012] In some embodiments of the present application, the number of R1 is 3.

[0013] In some embodiments of the present application, each R1 is independently selected from F or -SO2F.

[0014] In some embodiments of the present application, C 1~5 alkyl is selected from -CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)2, -CH2CH2CH2CH3, -CH2CH(CH3)2, -C(CH3)3, -CH2CH2CH2CH2CH3, -C(CH3)2CH2CH3, or -CH2C(CH3)3.

[0015] In some embodiments of the present application, R4 is methyl.

[0016] In some embodiments of the present application, the chemical bond is a single bond.

[0017] In some embodiments of the present application, the compound of formula (I) is selected from at least one of: , , ,

[0018] In some embodiments of the present application, the electrolyte additive further comprises an additive B, and the additive B is selected from at least one of fluoroethylene carbonate, 1,3-propane sultone, vinylene carbonate, vinyl ethylene carbonate, vinyl sulfate, lithium difluorophosphate.

[0019] In some embodiments of the present application, the mass ratio of the additive A and the additive B is 1: (0.03-150); in some preferred embodiments of the present application, the mass ratio of the additive A and the additive B is 1: (1-50); in some further preferred embodiments of the present application, the mass ratio of the additive A and the additive B is 1: (1-20); in some still further preferred embodiments of the present application, the mass ratio of the additive A and the additive B is 1: (1-10).

[0020] The second aspect of the present application provides an electrolyte comprising a metal salt and an organic solvent, wherein the electrolyte further comprises the electrolyte additive.

[0021] In some embodiments of the present application, the mass of the electrolyte additive is 0.2-18% of the total mass of the electrolyte.

[0022] In some embodiments of the present application, the mass of the additive A in the electrolyte additive is 0.1-3% of the total mass of the electrolyte; in some preferred embodiments of the present application, the mass of the additive A in the electrolyte additive is 0.1-1% of the total mass of the electrolyte.

[0023] ​In some embodiments of the present invention, the mass of additive B in the electrolyte additive is 0.1 to 15% of the total mass of the electrolyte.

[0024] In some embodiments of the present invention, the concentration of the metal salt in the electrolyte is 0.5~2 mol / L.

[0025] In some embodiments of the present invention, the metal salt includes lithium salt, sodium salt, or potassium salt.

[0026] In some embodiments of the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate borate) (LiBOB), lithium difluorobis(oxalate phosphate) (LiDFBOP), lithium difluorophosphate (LiPO2F2), lithium hexafluoroantimonyate (LiSbF6), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), tris(trifluoromethanesulfonyl)methyl lithium (Li(CF3SO2)3C), lithium bis(trifluoromethanesulfonyl)imide (Li(CF3SO2)2N), lithium bis(fluorosulfonyl)imide (Li(FSO2)2N), lithium nonafluorobutyrate (LiC4F9SO3), lithium perchlorate (LiClO4), lithium aluminate (LiAlO2), and lithium tetrachloroaluminate (LiAlCl4).

[0027] In some embodiments of the present invention, the sodium salt is selected from at least one of sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4), sodium tetrafluoroborate (NaBF4), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium bis(fluorosulfonyl)imide (NaFSI), and sodium trifluoromethanesulfonate (NaOTf).

[0028] In some embodiments of the present invention, the potassium salt is selected from at least one of potassium hexafluorophosphate (KPF6), potassium perchlorate (KClO4), potassium tetrafluoroborate (KBF4), potassium bis(trifluoromethanesulfonyl)imide (KTFSI), potassium bis(fluorosulfonyl)imide (KFSI), and potassium trifluoromethanesulfonate (KOTf).

[0029] In some embodiments of the present invention, additive B in the electrolyte additive includes fluoroethylene carbonate, 1,3-propane sulpholactone, vinylene carbonate, and vinyl sulfate.

[0030] In some embodiments of the present invention, the mass of the fluoroethylene carbonate is 0.5 to 1.5% of the total mass of the electrolyte.

[0031] In some embodiments of the present invention, the mass of the 1,3-propanesulfonyl lactone is 0.3 to 0.8% of the total mass of the electrolyte.

[0032] In some embodiments of the present invention, the mass of the vinylene carbonate is 1.5 to 2.5% of the total mass of the electrolyte.

[0033] In some embodiments of the present invention, the mass of the vinyl sulfate is 0.3 to 0.8% of the total mass of the electrolyte.

[0034] In some embodiments of the present invention, the additive B further includes an alkali metal difluorophosphate; the mass of the alkali metal difluorophosphate is 0.1 to 0.5% of the total mass of the electrolyte.

[0035] In some embodiments of the present invention, the alkali metal difluorophosphate is selected from lithium difluorophosphate, potassium difluorophosphate, or sodium difluorophosphate.

[0036] A third aspect of the present invention provides a battery comprising the electrolyte described in the second aspect of the present invention, wherein the battery is a lithium-ion battery, a sodium-ion battery, or a potassium-ion battery.

[0037] A fourth aspect of the present invention provides an electrical device comprising the electrolyte described in the second aspect of the present invention or the battery described in the third aspect of the present invention.

[0038] In some embodiments of the present invention, the electrical equipment includes vehicles, computers, drones, power banks, and other devices that require batteries.

[0039] The beneficial effects of this invention are as follows: When the electrolyte additive of this invention is added to the electrolyte, it can improve the transport kinetics of lithium ions in the electrolyte, enhance the cycle performance of batteries using this electrolyte at high and low temperatures and their storage stability at high temperatures, and at the same time, it has a protective effect on the positive electrode, reducing the degree of solvent oxidation on the positive electrode and thus reducing the occurrence of side reactions. Furthermore, the electrolyte additive of this invention, by introducing the compound shown in formula (I), can establish a highly stable interfacial film on the positive and negative electrodes, and can be used to manufacture high-performance batteries.

[0040] When the electrolyte additive containing the compound shown in formula (I) is added to the electrolyte and used in lithium-ion batteries, the lithium-ion batteries produced can retain a capacity of 78.6-93.6% after 50 cycles at a low temperature of 10°C, a capacity of 81.2-93.2% after 300 cycles at a high temperature of 45°C, and a capacity of 78.5-90.5% and a capacity recovery rate of 81.8-92.6% after 30 days of storage at a high temperature of 60°C, exhibiting good high-temperature low-cycle stability and high-temperature storage stability. Attached Figure Description

[0041] Figure 1The NMR spectrum of the compound represented by formula (2) in the embodiment of the present invention is shown. Detailed Implementation

[0042] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0043] In some embodiments of the present invention, an electrolyte additive is provided, the electrolyte additive comprising additive A, wherein additive A is a compound represented by formula (I):

[0044] Formula (I), Among them, ring A is selected from nitrogen-containing five-membered rings that are either R1-substituted or unsubstituted; Ring B is selected from R2-substituted or unsubstituted benzene rings; L is selected from non-existent, chemical bond, or -O-Si(R4)2-; When L is not present, ring A is selected from a nitrogen-containing five-membered ring with R1 substitution, and ring B is selected from an unsubstituted benzene ring, ring A and ring B fuse to form a compound with the structure shown below: ; The number of R1s is 1, 2, or 3, and each R1 is independently selected from H, F, or -SO2F; R2 is selected from C 1~5 Alkyl groups, -CF3, or -SO2N(CF3)2; R3 is selected from C 1~5 Alkyl groups, -CF3, or -Si(CH3)3; R4 is selected from C 1~5 Alkyl groups.

[0045] The electrolyte additive in this invention contains a compound represented by formula (I). The nitrogen atom in ring A has a lone pair of electrons that are not conjugated, giving it a certain degree of alkalinity, thus allowing it to react with H. + Combined, this reduces the acidity of the electrolyte using this electrolyte additive. Furthermore, the compound shown in formula (I) can form a nitrogen-rich and lithium-philic SEI film, promoting uniform lithium deposition and effectively suppressing side reactions. Simultaneously, the formed SEI film is rich in lithium fluoride and a benzene ring framework, exhibiting good permeability to lithium ions and enhancing lithium ion transport kinetics. The nitrogen atoms in the compound shown in formula (I) can capture H2 produced by the decomposition of LiPF6 at high temperatures or in trace amounts of water. +This serves to remove water and suppress acid. Simultaneously, the benzene ring in the compound shown in formula (I) protects the cathode material, effectively preventing Fe... 2+ The dissolution of the compound; the benzene ring in the compound shown in formula (I) is conducive to film formation at the negative electrode, which improves the cycle performance of the battery; in addition, after the compound shown in formula (I) undergoes redox under the action of potential, it can form a high ionic conductivity material with nitrogen-rich and sulfur-rich groups at the positive and negative electrodes, and it can inhibit the dehydrogenation reaction of EC on the surface of the positive electrode, thereby continuously repairing the damaged CEI film. Therefore, when the electrolyte additive in this invention is applied to the battery, it can improve the cycle stability of the battery at high and low temperatures and the storage stability at high temperatures, so that the battery has a high capacity retention rate at both high and low temperatures, and still has a high capacity retention rate and capacity recovery rate after one month of storage at high temperature.

[0046] In some embodiments of the present invention, the number of nitrogen atoms in the nitrogen-containing five-membered ring is an integer from 1 to 3; in some embodiments of the present invention, the number of nitrogen atoms in the nitrogen-containing five-membered ring is 1, 2 or 3.

[0047] In some embodiments of the present invention, ring A is selected from imidazole or... .

[0048] In some embodiments of the present invention, ring B is selected from unsubstituted benzene rings, or .

[0049] In some embodiments of the present invention, the number of R1 is 3.

[0050] In some embodiments of the present invention, each R1 is independently selected from F or -SO2F.

[0051] In some embodiments of the present invention, C 1~5 The alkyl group is selected from -CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)2, -CH2CH2CH2CH3, -CH2CH(CH3)2, -C(CH3)3, -CH2CH2CH2CH2CH3, -C(CH3)2CH2CH3 or -CH2C(CH3)3.

[0052] In some embodiments of the present invention, R4 is a methyl group.

[0053] In some embodiments of the present invention, the chemical bond is a single bond.

[0054] In some embodiments of the present invention, the compound represented by formula (I) is selected from: , , , At least one of them.

[0055] In some embodiments of the present invention, the electrolyte additive further includes additive B, which is selected from at least one of fluoroethylene carbonate, 1,3-propane sulpholone, vinylene carbonate, ethylene ethylene carbonate, vinyl sulfate, and lithium difluorophosphate; in some embodiments of the present invention, additive B includes fluoroethylene carbonate, 1,3-propane sulpholone, vinylene carbonate, and vinyl sulfate; in some embodiments of the present invention, additive B includes fluoroethylene carbonate, 1,3-propane sulpholone, vinylene carbonate, alkali metal difluorophosphate, and vinyl sulfate.

[0056] In some embodiments of the present invention, the mass ratio of additive A to additive B is 1:(0.03~150); in some embodiments of the present invention, the mass ratio of additive A to additive B is 1:0.03, 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, or 1:90. The ratio of additive A to additive B is 1:(1~50); in some preferred embodiments of the present invention, the ratio of additive A to additive B is 1:(1~20); in some preferred embodiments of the present invention, the ratio of additive A to additive B is 1:(1~20); in some preferred embodiments of the present invention, the ratio of additive A to additive B is 1:(1~10).

[0057] In some embodiments of the present invention, the present invention also provides an electrolyte comprising a metal salt and an organic solvent, and the electrolyte further comprising the above-mentioned electrolyte additives.

[0058] In some embodiments of the present invention, the mass of the electrolyte additive is 0.2% to 18% of the total mass of the electrolyte; in some embodiments of the present invention, the mass of the electrolyte additive is any value or a range formed by any two of the following: 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18% of the total mass of the electrolyte.

[0059] In some embodiments of the present invention, the mass of additive A in the electrolyte additive is 0.1-3% of the total mass of the electrolyte; in some embodiments of the present invention, the mass of additive A in the electrolyte additive is any value or a range formed by any two of the following: 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0% of the total mass of the electrolyte; in some preferred embodiments of the present invention, the mass of additive A in the electrolyte additive is 0.1-1.5% of the total mass of the electrolyte; in some further preferred embodiments of the present invention, the mass of additive A in the electrolyte additive is 0.5-1.5% of the total mass of the electrolyte. When the amount of additive A is within the range defined in this invention, the battery has a lower internal resistance and can better improve the battery's high-temperature cycle stability and high-temperature storage stability. The sulfonic acid groups contained in additive A are beneficial to the increase of the battery's direct current resistance (DCIR), increasing the cell's impedance. In addition, the phenyl groups in additive A, after undergoing reduction polymerization, will increase the viscosity of the electrolyte, thereby reducing the cell's kinetic performance and affecting the cell's cycle performance.

[0060] In some embodiments of the present invention, the mass of additive B in the electrolyte additive is 0.1-15% of the total mass of the electrolyte; in some embodiments of the present invention, the mass of additive B in the electrolyte additive is any value or a range formed by any two of the following: 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15% of the total mass of the electrolyte.

[0061] In some embodiments of the present invention, the concentration of the metal salt in the electrolyte is 0.5~2 mol / L; in some embodiments of the present invention, the concentration of the metal salt in the electrolyte is any value or a range formed by any two of the following: 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, and 2.0 mol / L.

[0062] In some embodiments of the present invention, the metal salt includes lithium salt, sodium salt, or potassium salt.

[0063] In some embodiments of the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate borate) (LiBOB), lithium difluorobis(oxalate phosphate) (LiDFBOP), lithium difluorophosphate (LiPO2F2), lithium hexafluoroantimonyate (LiSbF6), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), tris(trifluoromethanesulfonyl)methyl lithium (Li(CF3SO2)3C), lithium bis(trifluoromethanesulfonyl)imide (Li(CF3SO2)2N), lithium bis(fluorosulfonyl)imide (Li(FSO2)2N), lithium nonafluorobutyrate (LiC4F9SO3), lithium perchlorate (LiClO4), lithium aluminate (LiAlO2), and lithium tetrachloroaluminate (LiAlCl4).

[0064] In some embodiments of the present invention, the sodium salt is selected from at least one of sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO6), sodium tetrafluoroborate (NaBF4), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium bis(fluorosulfonyl)imide (NaFSI), and sodium trifluoromethanesulfonate (NaOTf).

[0065] In some embodiments of the present invention, the potassium salt is selected from at least one of potassium hexafluorophosphate (KPF6), potassium perchlorate (KClO4), potassium tetrafluoroborate (KBF4), potassium bis(trifluoromethanesulfonyl)imide (KTFSI), potassium bis(fluorosulfonyl)imide (KFSI), and potassium trifluoromethanesulfonate (KOTf).

[0066] When the electrolyte of this invention is applied to a sodium-ion battery, the metal salt is a sodium salt; when the electrolyte of this invention is applied to a lithium-ion battery, the metal salt is a lithium salt; when the electrolyte of this invention is applied to a potassium-ion battery, the metal salt is a potassium salt.

[0067] In some embodiments of the present invention, additive B in the electrolyte additive includes fluoroethylene carbonate, 1,3-propane sulpholactone, vinylene carbonate, and vinyl sulfate.

[0068] In some embodiments of the present invention, the mass of fluoroethylene carbonate is 0.5 to 1.5% of the total mass of the electrolyte; in some embodiments of the present invention, the mass of fluoroethylene carbonate is any value or a range formed by any two of the following: 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, and 1.5% of the total mass of the electrolyte.

[0069] In some embodiments of the present invention, the mass of 1,3-propanesulfonyl lactone is 0.3 to 0.8% of the total mass of the electrolyte; in some embodiments of the present invention, the mass of 1,3-propanesulfonyl lactone is any one of 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% of the total mass of the electrolyte, or a range formed by any two of these values.

[0070] In some embodiments of the present invention, the mass of vinylene carbonate is 1.5 to 2.5% of the total mass of the electrolyte; in some embodiments of the present invention, the mass of vinylene carbonate is any value or a range formed by any two of the following: 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, and 2.5% of the total mass of the electrolyte.

[0071] In some embodiments of the present invention, the mass of vinyl sulfate is 0.3 to 0.8% of the total mass of the electrolyte; in some embodiments of the present invention, the mass of vinyl sulfate is any one of 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% of the total mass of the electrolyte, or a range formed by any two of these values.

[0072] In some embodiments of the present invention, additive B further includes an alkali metal difluorophosphate.

[0073] In some embodiments of the present invention, the mass of the alkali metal difluorophosphate is 0.1 to 0.5% of the total mass of the electrolyte; in some embodiments of the present invention, the mass of the alkali metal difluorophosphate is any value or a range formed by any two of the following: 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5% of the total mass of the electrolyte.

[0074] In some embodiments of the present invention, the alkali metal salt of difluorophosphate is selected from lithium difluorophosphate, potassium difluorophosphate, or sodium difluorophosphate. When the electrolyte of the present invention is applied to a sodium-ion battery, the alkali metal salt of difluorophosphate is sodium difluorophosphate; when the electrolyte of the present invention is applied to a lithium-ion battery, the alkali metal salt of difluorophosphate is lithium difluorophosphate; and when the electrolyte of the present invention is applied to a potassium-ion battery, the alkali metal salt of difluorophosphate is potassium difluorophosphate.

[0075] In some embodiments of the present invention, the organic solvent is selected from at least one of carbonate solvents, carboxylic acid ester solvents, ether solvents, fluorocarbonates, carboxylic acid esters, and ether solvents.

[0076] In some embodiments of the present invention, the carbonate solvent is selected from at least one of dimethyl carbonate, ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0077] In some embodiments of the present invention, the carboxylic acid ester solvent is selected from at least one of methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, and butyldecyl lactone.

[0078] In some embodiments of the present invention, the ether solvent is selected from at least one of dibutyl ether, tetraethylene glycol, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran.

[0079] In some embodiments of the present invention, the organic solvent includes ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate; in some preferred embodiments of the present invention, the volume ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate in the organic solvent is 3:(3~5):(2~4).

[0080] In some embodiments of the present invention, the present invention also provides a battery comprising the above-mentioned electrolyte, wherein the battery is a lithium-ion battery, a sodium-ion battery, or a potassium-ion battery.

[0081] In some embodiments of the present invention, the battery further includes a positive electrode and a negative electrode.

[0082] In some embodiments of the present invention, the battery further includes a separator.

[0083] In some embodiments of the present invention, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on the positive current collector.

[0084] In some embodiments of the present invention, the positive electrode active material layer includes a metal salt; in some embodiments of the present invention, the positive electrode active material layer includes lithium iron phosphate, lithium cobalt oxide, NCM ternary material, lithium manganese oxide, or lithium-rich manganese-based material.

[0085] In some embodiments of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0086] In some embodiments of the present invention, the negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder.

[0087] In some embodiments of the present invention, the negative electrode active material includes at least one of graphite, silicon, conductive carbon black, and lithium titanate.

[0088] In some embodiments of the present invention, the conductive agent includes at least one of conductive carbon black, carbon nanotubes, and graphite.

[0089] In some embodiments of the present invention, the adhesive is selected from at least one of styrene-butadiene rubber, polyvinylidene fluoride, sodium carboxymethyl cellulose, polyacrylic acid, and polyimide.

[0090] In some embodiments of the present invention, the present invention also provides an electrical device, which includes the above-described electrolyte or the above-described battery.

[0091] In some embodiments of the present invention, the electrical equipment includes vehicles, computers, drones, power banks, and other devices that require batteries.

[0092] In some embodiments of the present invention, the vehicle may be a private car, such as a sedan, SUV, MPV or pickup truck; the vehicle may also be a commercial vehicle, such as a van, bus, small truck or large trailer; the vehicle may be a new energy vehicle, such as a hybrid vehicle or a pure electric vehicle.

[0093] The specific implementation of the present invention will be further described in detail below with reference to specific embodiments and comparative examples: The raw material information used in the following examples and comparative examples is as follows: The compounds of formulas (1) to (4) in this invention can be purchased from companies such as Sigma-Aldrich, TCI Chemicals, Alfa Aesar, WuXi AppTec, and Pharmaron, or can be synthesized using existing synthetic routes. Taking the compound of formula (2) as an example, it can be obtained by the following synthetic method: Weigh 108.702 g (0.55 mol) of 4-chlorobenzenesulfonamide and 34.0385 g (0.5 mol) of imidazole in a glove box and add them to a 300 mL three-necked flask containing diethyl ether. Transfer the mixture to an oil bath in a fume hood, purge with nitrogen for protection, and heat to 80–83 °C. React for 6–8 h. Detect the reaction product by liquid chromatography until no imidazole peak is observed, yielding the crude reaction intermediate: p-(1H-imidazol-1-yl)benzenesulfonamide. Cool and crystallize the crude reaction intermediate, wash with diethyl ether, and collect the purified p-(1H-imidazol-1-yl)benzenesulfonamide.

[0094] The collected refined reaction intermediate was added to a polytetrafluoroethylene three-necked flask containing acetone. The reaction was initiated by adding carbon tetrachloride dropwise. Once no solid remained in the flask, the addition of carbon tetrachloride was stopped, and hydrofluoric acid was added dropwise. The reaction was stopped once no more gas was produced, and the solution in the reaction vessel was collected. The solution was transferred to a low-temperature crystallization tank, and the temperature was lowered from 0°C to -20°C at a rate of 0.5°C / min. The obtained solid was collected, washed with dichloromethane, and the compound shown in formula (2) was obtained. 33 S-NMP NMR image as follows Figure 1 As shown.

[0095] Example 1 This example provides an electrolyte composed of lithium hexafluorophosphate, organic solvents, and additives. The electrolyte formulation is shown in Table 1 below.

[0096] The organic solvent is composed of the following components by volume percentage: ethylene carbonate (EC) 30%, dimethyl carbonate (DMC) 40%, and ethyl methyl carbonate (EMC) 30%. The concentration of lithium hexafluorophosphate in the electrolyte is 1.3 mol / L; Based on the total mass of the electrolyte, the additive consists of 2% by mass vinylene carbonate (VC), 1% by mass fluoroethylene carbonate (FEC), 0.5% by mass 1,3-propanesulfonyl lactone (1,3-PS), 0.5% by mass vinyl sulfate (DTD), 0.3% by mass lithium difluorophosphate (LiDPF), and 0.5% by mass of the compound represented by formula (1).

[0097] The compound shown in formula (1) is named 2-fluoro-2H-benzo[d]imidazolium-1,3-disulfonyl difluoride, and its structural formula is: ; This example provides a method for preparing the above-mentioned electrolyte, and the specific steps are as follows: In a glove box, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are mixed in a volume percentage ratio of 30%, 40%, and 30% respectively to obtain a mixed solvent. Lithium hexafluorophosphate is then added to the mixed solvent to dissolve it, preparing a lithium salt solution of lithium hexafluorophosphate. Additives are then added to the lithium salt solution to obtain the electrolyte used in this example.

[0098] This example also provides a method for preparing a lithium-ion battery, the specific steps of which are as follows: The prepared electrolyte was injected into a fully dried lithium iron phosphate / graphite pouch cell. The positive electrode of the pouch cell had the following material composition: lithium iron phosphate: conductive carbon black (Super P): carbon nanotubes: polyvinylidene fluoride: flexibility agent in a mass ratio of 96.8:0.9:0.3:1.8:0.2; the negative electrode had the following material composition: conductive carbon black (Super P): styrene-butadiene rubber (SBR): sodium carboxymethyl cellulose (CMC) in a mass ratio of 96.6:0.6:1.6:1.2. Then, after a 45°C resting period, high-temperature forming in a fixture (forming temperature 45°C, forming pressure 1 MPa), and a secondary sealing process, the lithium-ion battery in this example was obtained.

[0099] Example 2 The only difference between the electrolyte in this example and the electrolyte in Example 1 is that the mass of the compound represented by formula (1) in this example is 1% of the total mass of the electrolyte, and the specific formulation of the electrolyte is shown in Table 1 below.

[0100] The preparation methods of the electrolyte and lithium-ion battery in this example are the same as those in Example 1.

[0101] Example 3 The only difference between the electrolyte in this example and the electrolyte in Example 1 is that the mass of the compound represented by formula (1) in this example is 1.5% of the total mass of the electrolyte, and the specific formulation of the electrolyte is shown in Table 1 below.

[0102] The preparation methods of the electrolyte and lithium-ion battery in this example are the same as those in Example 1.

[0103] Example 4 The only difference between the electrolyte in this example and the electrolyte in Example 1 is that the compound shown in Formula (1) in Example 1 is replaced by the compound shown in Formula (2) in this example, and the mass of the compound shown in Formula (2) is 1% of the total mass of the electrolyte. The specific formulation of the electrolyte is shown in Table 1 below.

[0104] The structural formula of the compound shown in formula (2) is:

[0105] The preparation methods of the electrolyte and lithium-ion battery in this example are the same as those in Example 1.

[0106] Example 5 The only difference between the electrolyte in this example and the electrolyte in Example 1 is that the compound shown in Formula (1) in Example 1 is replaced by the compound shown in Formula (3) in this example, and the mass of the compound shown in Formula (3) is 1% of the total mass of the electrolyte. The specific formulation of the electrolyte is shown in Table 1 below.

[0107] The compound shown in formula (3) is named 1-((4-(trifluoromethyl)phenoxy)dimethylsilyl)-1H-imidazolium, and its structural formula is:

[0108] The preparation methods of the electrolyte and lithium-ion battery in this example are the same as those in Example 1.

[0109] Example 6 The only difference between the electrolyte in this example and the electrolyte in Example 1 is that the compound shown in Formula (1) in Example 1 is replaced by the compound shown in Formula (4) in this example, and the mass of the compound shown in Formula (4) is 1% of the total mass of the electrolyte. The specific formulation of the electrolyte is shown in Table 1 below.

[0110] The compound shown in formula (4) is named 2-(1H-imidazol-1-yl)-1-(trimethylsilyl)-1H-benzo[d]imidazolium, and its structural formula is:

[0111] The preparation methods of the electrolyte and lithium-ion battery in this example are the same as those in Example 1.

[0112] Example 7 The electrolyte in this example differs from the electrolyte in Example 1 only in that, based on the total mass of the electrolyte, the additives consist of 2% by mass of vinylene carbonate (VC), 1% by mass of fluoroethylene carbonate (FEC), 0.5% by mass of 1,3-propanesulfonyl lactone (1,3-PS), 0.5% by mass of vinyl sulfate (DTD), and 1.0% by mass of the compound represented by formula (1). The specific formulation of the electrolyte is shown in Table 1 below.

[0113] The preparation methods of the electrolyte and lithium-ion battery in this example are the same as those in Example 1.

[0114] Comparative Example 1 The electrolyte in this example differs from the electrolyte in Example 1 only in that, based on the total mass of the electrolyte, the additives consist of 2% vinylene carbonate (VC), 1% fluoroethylene carbonate (FEC), 0.5% 1,3-propanesulfonyl lactone (1,3-PS), 0.5% ethylene sulfate (DTD), and 0.3% lithium difluorophosphate (LiDPF). The specific formulation of the electrolyte is shown in Table 1 below.

[0115] The preparation methods of the electrolyte and lithium-ion battery in this example are the same as those in Example 1.

[0116] Table 1. Formulations of the electrolytes in Examples 1-7 and Comparative Example 1

[0117] Performance testing: The high-temperature cycle performance, high-temperature storage performance, and low-temperature cycle performance of the lithium-ion batteries prepared in Examples 1-7 and Comparative Example 1 were tested respectively. The specific test methods are as follows: Test method for high-temperature cycling performance: Under high temperature (45℃) conditions, the above lithium-ion battery was charged to 3.75V under 1C constant current and constant voltage conditions, and then discharged to 2.0V under 1C constant current conditions. After 300 charge-discharge cycles, the capacity retention rate after the 300th cycle was calculated according to the following formula: Capacity retention rate after the 300th cycle =

[0118] Test method for high-temperature storage performance: Under normal temperature (25℃) conditions, the lithium-ion battery is charged and discharged once at 0.5C / 1C (discharge capacity recorded as DC0), and then charged to 3.75V under 1C constant current and constant voltage conditions; the lithium-ion battery (100% SOC) is stored in a 60℃ high-temperature chamber for 1 month, and after being removed, it is discharged at 1C under normal temperature conditions (discharge capacity recorded as DC1); then charged and discharged at 0.5C / 1C under normal temperature conditions (discharge capacity recorded as DC2), and the capacity retention rate and capacity recovery rate of the lithium-ion battery are calculated using the following formulas: Capacity retention rate (%) = ×100%; Capacity recovery rate (%) = ×100%.

[0119] Low-temperature cycling performance test method: Under low-temperature (10℃) conditions, the above lithium-ion battery was charged to 3.75V under constant current and constant voltage at 0.5C, and then discharged to 2.0V under constant current at 1C. After 50 charge-discharge cycles, the capacity retention rate after the 50th cycle was calculated according to the following formula: Capacity retention rate (%) after 50 cycles = ×100%.

[0120] The battery performance test results obtained in Examples 1-7 and Comparative Example 1 according to the above test methods are shown in Table 2 below.

[0121] Table 2. Performance test results of the batteries prepared in Examples 1-7 and Comparative Example 1

[0122] As shown in Table 2, compared with Comparative Example 1, Examples 1-7 significantly improved the low-temperature and high-temperature cycle stability and high-temperature storage performance by introducing the compounds shown in Formulas (1) to (4). Specifically, the lithium-ion batteries prepared in Examples 1-7 had a capacity retention rate of 78.6-93.6% after 50 cycles at a low temperature of 10°C, a capacity retention rate of 81.2-93.2% after 300 cycles at a high temperature of 45°C, and a capacity retention rate of 78.5-90.5% and a capacity recovery rate of 81.8-92.6% after 30 days of storage at a high temperature of 60°C, all of which were significantly higher than those in Comparative Example 1.

[0123] In addition, the electrolytes in Examples 1-7 of this invention also contain additives such as vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate. These components work synergistically with the compounds in formulas (1) to (4) to improve the high and low temperature cycle stability and high temperature storage performance of the battery. In this invention, vinylene carbonate mainly forms an organic polymer film at the positive and negative electrodes. This organic polymer film is easily decomposed at high temperatures and has poor thermal stability. Its synergistic effect with fluoroethylene carbonate can solve the problem of high temperature instability of the organic polymer film and participate in the formation of the SEI film. The SEI film contains not only organic polymer film but also inorganic LiF, etc. The stability of the SEI film is improved, which improves the high and low temperature cycle performance of the battery to a certain extent. However, since fluoroethylene carbonate is unstable at high temperatures and is prone to defluorination to form HF, in order to overcome this disadvantage, this invention also introduces 1,3-propanesulfonate lactone into the electrolyte to further improve the cycle stability and storage stability of the battery at high temperatures. Furthermore, by introducing vinyl sulfate, the cycle stability of the battery at low temperatures is further improved.

[0124] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An electrolyte additive, characterized in that: The electrolyte additive includes additive A, which is a compound of formula (I): Formula (I), Among them, ring A is selected from nitrogen-containing five-membered rings that are either R1-substituted or unsubstituted; Ring B is selected from R2-substituted or unsubstituted benzene rings; L is selected from non-existent, chemical bond, or -O-Si(R4)2-; When L is not present, ring A is selected from a nitrogen-containing five-membered ring with R1 substitution, and ring B is selected from an unsubstituted benzene ring, ring A and ring B fuse to form a compound with the structure shown below: ; The number of R1s is 1, 2, or 3, and each R1 is independently selected from H, F, or -SO2F; R2 is selected from C 1~5 Alkyl groups, -CF3, or -SO2N(CF3)2; R3 is selected from C 1~5 Alkyl groups, -CF3, or -Si(CH3)3; R4 is selected from C 1~5 Alkyl groups.

2. The electrolyte additive according to claim 1, characterized in that: The compound represented by formula (I) is selected from: , , , At least one of them.

3. The electrolyte additive according to claim 1 or 2, characterized in that: The electrolyte additive also includes additive B, which is selected from at least one of fluoroethylene carbonate, 1,3-propane sulpholol, vinylene carbonate, ethylene ethylene carbonate, and lithium difluorophosphate.

4. The electrolyte additive according to claim 3, characterized in that: The mass ratio of additive A to additive B is 1:(0.03~150).

5. An electrolyte comprising a metal salt and an organic solvent, characterized in that: The electrolyte further includes the electrolyte additives described in any one of claims 1 to 4.

6. The electrolyte according to claim 5, characterized in that: The mass of the electrolyte additive is 0.2% to 18% of the total mass of the electrolyte; And / or, the concentration of the metal salt in the electrolyte is 0.5~2 mol / L.

7. The electrolyte according to claim 5, characterized in that: Additive B in the electrolyte additive includes fluoroethylene carbonate, 1,3-propane sulpholactone, vinylene carbonate, and vinyl sulfate. The mass of the fluoroethylene carbonate is 0.5-1.5% of the total mass of the electrolyte; The mass of the 1,3-propanesulfonyl lactone is 0.3-0.8% of the total mass of the electrolyte; The mass of the vinylene carbonate is 1.5 to 2.5% of the total mass of the electrolyte; The mass of the ethylene sulfate is 0.3 to 0.8% of the total mass of the electrolyte.

8. The electrolyte according to claim 7, characterized in that: Additive B also includes an alkali metal difluorophosphate; the mass of the alkali metal difluorophosphate is 0.1 to 0.5% of the total mass of the electrolyte.

9. A battery, characterized in that: Includes the electrolyte according to any one of claims 5 to 8, wherein the battery is a lithium-ion battery, a sodium-ion battery, or a potassium-ion battery.

10. An electrical appliance, characterized in that: The electrical device includes the electrolyte as described in any one of claims 5 to 8 or the battery as described in claim 9.

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