Electrolyte, battery monomer containing electrolyte, battery and electric device

Abstract

The embodiment of the invention provides an electrolyte, a battery monomer containing the electrolyte, a battery and an electric device. The electrolyte comprises a first additive, and the first additive comprises an isocyanate compound shown in the formula (I), r comprises a hydrogen atom, a halogen atom, a nitrogen-containing group, an oxygen-containing group, a sulfur-containing group, a phosphorus-containing group, an alkyl group, a naphthenic base, a phenyl group, an aryl group, a halogenated phenyl group and at least one of an alkyl group, a naphthenic base, a phenyl group, an aryl group and a halogenated phenyl group containing at least one isocyanic acid radical, and n is any natural number from 0 to 8; the lithium salt comprises lithium bis (fluorosulfonyl) imide, the weight content of the lithium bis (fluorosulfonyl) imide in the lithium salt is 30-85% based on the total weight of the lithium salt, and the cycle performance and the storage life of the battery containing the electrolyte are improved. # imgabs0 #

Description

Electrolyte, battery cell containing same, battery and electrical device Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an electrolyte, a battery cell containing the electrolyte, a battery, and an electrical device. Background Art

[0002] In recent years, secondary batteries, due to their high energy density and recyclability, have been widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. With the rapid development and widespread application of secondary batteries, higher requirements have been placed on their cycling performance, storage life, and other performance characteristics.

[0003] Therefore, how to improve the cycle performance and storage life of secondary batteries is a technical problem that needs to be solved urgently.

[0004] Summary of the Invention

[0005] The present invention provides an electrolyte, a battery cell containing the electrolyte, a battery, and an electrical device. The battery containing the electrolyte has improved cycle performance and storage life.

[0006] In a first aspect, an electrolyte is provided, comprising: a first additive, wherein the first additive comprises an isocyanate compound represented by formula (I):

[0007] Wherein, R includes at least one of a hydrogen atom, a halogen atom, a nitrogen-containing group, an oxygen-containing group, a sulfur-containing group, a phosphorus-containing group, an alkyl group, a cycloalkyl group, a phenyl group, an aryl group, a halogenated phenyl group, and an alkyl group, cycloalkyl group, a phenyl group, an aryl group, and a halogenated phenyl group containing at least one isocyanate group, and the value of n is any natural number from 0 to 8; the lithium salt includes lithium bis(fluorosulfonyl)imide, and the weight content of the lithium bis(fluorosulfonyl)imide in the lithium salt is 30% to 85% based on the total weight of the lithium salt.

[0008] In an embodiment of the present application, the electrolyte includes a first additive and a lithium salt, wherein the first additive includes an isocyanate compound, and the lithium salt includes lithium bis(fluorosulfonyl)imide. The electrode material of the battery easily absorbs water. During the use of the battery, the water adsorbed by the electrode material will diffuse into the electrolyte, and there is a possibility that it will react with the lithium salt in the electrolyte to generate acidic substances, causing the electrolyte to deteriorate and increase the internal resistance of the battery; at the same time, it will corrode the electrode interface film, affecting the service life of the battery; at the same time, the reduction potential of water is high and it is easily reduced, which will cause the first efficiency and initial capacity of the battery to be low. Isocyanate compounds have good acid binding capacity, which can reduce the impact of moisture on battery performance. At the same time, they will participate in the formation of the electrode interface film, improve the thermal stability of the electrode interface film, reduce the possibility of gas expansion of the battery, and improve the cycle performance and storage life of the battery. However, isocyanate compounds will affect the kinetic performance of the battery and increase the film formation impedance of the electrode interface film, while lithium bis(fluorosulfonyl)imide easily dissociates into lithium ions in the electrolyte, improving the conductivity of the battery, improving the kinetic performance of the battery, and reducing the film formation impedance of the electrode interface film. Adding isocyanate compounds and lithium bis(fluorosulfonyl)imide to the electrolyte at the same time improves the cycle life and storage performance of the battery while taking into account the dynamic performance of the battery. Furthermore, due to the low oxidation potential of lithium bis(fluorosulfonyl)imide, it will easily corrode the aluminum foil of the electrode plate during the use of the battery and increase the risk of thermal runaway of the battery. Therefore, it is necessary to mix lithium bis(fluorosulfonyl)imide with other types of lithium salts and control the weight content of lithium bis(fluorosulfonyl)imide in the total lithium salt to be 30% to 85%. While ensuring that the content of lithium bis(fluorosulfonyl)imide can effectively improve the dynamic performance of the cell, the content of lithium bis(fluorosulfonyl)imide is controlled not to be too high, reducing the possibility of lithium bis(fluorosulfonyl)imide corroding the aluminum foil, increasing the service life of the battery, and reducing the risk of thermal runaway of the battery. In other words, the technical solution provided by the embodiment of the present application not only improves the cycle performance and storage life of the battery, but also reduces the risk of thermal runaway of the battery.

[0009] In one possible embodiment, the first additive includes at least one of the following substances:

[0010] In a possible embodiment, the weight ratio of the lithium bis(fluorosulfonyl)imide to the isocyanate compound in the electrolyte is 6:1 to 20:0.001.

[0011] The weight ratio of lithium bis(fluorosulfonyl)imide to isocyanate compound in the electrolyte needs to be within an appropriate range, which can not only ensure the acid binding capacity of the isocyanate compound, reduce the impact of moisture on battery performance, and improve the cycle performance and storage life of the battery, but also enable lithium bis(fluorosulfonyl)imide to offset the adverse effect of the isocyanate compound on increasing the film formation impedance of the electrode interface film, thereby improving the dynamic performance of the battery.

[0012] In a possible implementation, based on the total weight of the electrolyte, the weight content of the lithium bis(fluorosulfonyl)imide in the electrolyte is 3% to 20%.

[0013] A high weight content of lithium bis(fluorosulfonyl)imide in the electrolyte will increase the lithium salt concentration, which in turn increases the viscosity of the electrolyte, deteriorating the low-temperature performance of the battery and increasing the battery production cost. A low weight content of lithium bis(fluorosulfonyl)imide in the electrolyte will not effectively improve the battery's kinetic performance. Therefore, the weight content of lithium bis(fluorosulfonyl)imide in the electrolyte is set to 3% to 20%.

[0014] In one possible embodiment, based on the total weight of the electrolyte, the weight content of the isocyanate compound in the electrolyte is 0.001% to 0.5%. Optionally, the weight content of the isocyanate compound in the electrolyte is 0.005% to 0.3%. Further optionally, the weight content of the isocyanate compound in the electrolyte is 0.01% to 0.1%.

[0015] An excessively high isocyanate content in the electrolyte significantly increases the film formation resistance of the electrode interface film and affects the battery's charging capacity. An excessively low isocyanate content in the electrolyte binds less hydrofluoric acid, and the remaining free hydrofluoric acid in the electrolyte can affect battery performance. Therefore, the isocyanate content in the electrolyte is set to 0.001% to 0.5% by weight.

[0016] In a possible embodiment, the lithium salt further includes at least one of lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium difluorophosphate, and lithium hexafluorophosphate.

[0017] Lithium bis(fluorosulfonyl)imide reacts with the aluminum foil of the electrode plate to form a complex. This complex is unstable. After dissolving in a solvent, the lithium bis(fluorosulfonyl)imide can continue to react with the aluminum foil, causing continuous corrosion over time. If the lithium salt includes at least one of the above substances, these substances can form a stable coordination compound with the aluminum foil, AlF3 and LiF, forming a stable passivation layer that prevents further corrosion of the aluminum foil.

[0018] In a possible implementation, the electrolyte further includes a second additive, and the second additive includes at least one of carbonate, sulfonate, and fluorinated compound.

[0019] The content of isocyanate compounds in the electrolyte is limited. In order to ensure that the total amount of additives in the electrolyte is sufficient, other additives need to be added to reduce the risk of battery diving. In addition, carbonates, sulfonates and fluorinated compounds can participate in the formation of electrode interface films, help form a stable interface film, and improve the battery's cycle performance and storage life.

[0020] In one possible embodiment, the second additive includes at least one of vinylene carbonate, fluoroethylene carbonate, bisfluoroethylene carbonate, vinyl ethylene carbonate, vinyl sulfate, and 1,3-propane sultone.

[0021] In a possible embodiment, the electrolyte further includes a solvent, and the solvent includes at least one of a cyclic ester and a chain ester.

[0022] Ester solvents generally have the advantages of low melting point and high dielectric constant. Adding ester solvents such as cyclic esters and chain esters to the electrolyte can effectively reduce the viscosity of the electrolyte and increase the conductivity of the electrolyte, thereby achieving the purpose of improving the low-temperature performance and rate performance of the electrolyte.

[0023] In one possible embodiment, the solvent includes at least one of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, γ-butyrolactone, tetrahydrofuran, sulfolane, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl formate, methyl acetate, ethyl acetate, methyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

[0024] In a second aspect, a battery cell is provided, comprising: the electrolyte according to the first aspect or any possible implementation of the first aspect.

[0025] In a third aspect, a battery is provided, comprising: the battery cell according to the second aspect or any possible implementation of the second aspect.

[0026] In a fourth aspect, an electrical device is provided, comprising: the battery in the third aspect or any possible implementation of the third aspect.

[0027] In an embodiment of the present application, the electrolyte includes a first additive and a lithium salt, wherein the first additive includes an isocyanate compound, and the lithium salt includes lithium bis(fluorosulfonyl)imide. The electrode material of the battery easily absorbs water. During the use of the battery, the water adsorbed by the electrode material will diffuse into the electrolyte, and there is a possibility that it will react with the lithium salt in the electrolyte to generate acidic substances, causing the electrolyte to deteriorate and increase the internal resistance of the battery; at the same time, it will corrode the electrode interface film, affecting the service life of the battery; at the same time, the reduction potential of water is high and it is easily reduced, which will cause the first efficiency and initial capacity of the battery to be low. Isocyanate compounds have good acid binding capacity, which can reduce the impact of moisture on battery performance. At the same time, they will participate in the formation of the electrode interface film, improve the thermal stability of the electrode interface film, reduce the possibility of gas expansion of the battery, and improve the cycle performance and storage life of the battery. However, isocyanate compounds will affect the kinetic performance of the battery and increase the film formation impedance of the electrode interface film, while lithium bis(fluorosulfonyl)imide easily dissociates into lithium ions in the electrolyte, improving the conductivity of the battery, improving the kinetic performance of the battery, and reducing the film formation impedance of the electrode interface film. Adding isocyanate compounds and lithium bis(fluorosulfonyl)imide to the electrolyte at the same time improves the cycle life and storage performance of the battery while taking into account the dynamic performance of the battery. Furthermore, due to the low oxidation potential of lithium bis(fluorosulfonyl)imide, it will easily corrode the aluminum foil of the electrode plate during the use of the battery and increase the risk of thermal runaway of the battery. Therefore, it is necessary to mix lithium bis(fluorosulfonyl)imide with other types of lithium salts and control the weight content of lithium bis(fluorosulfonyl)imide in the total lithium salt to be 30% to 85%. While ensuring that the content of lithium bis(fluorosulfonyl)imide can effectively improve the dynamic performance of the cell, the content of lithium bis(fluorosulfonyl)imide is controlled not to be too high, reducing the possibility of lithium bis(fluorosulfonyl)imide corroding the aluminum foil, increasing the service life of the battery, and reducing the risk of thermal runaway of the battery. In other words, the technical solution provided by the embodiment of the present application not only improves the cycle performance and storage life of the battery, but also reduces the risk of thermal runaway of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0029] FIG1 is a schematic diagram of a battery cell disclosed in an embodiment of the present application;

[0030] FIG2 is a schematic diagram of the exploded structure of a battery cell disclosed in one embodiment of the present application;

[0031] FIG3 is a schematic diagram of the exploded structure of a battery disclosed in one embodiment of the present application;

[0032] FIG4 is a schematic diagram of an electrical device disclosed in an embodiment of the present application. DETAILED DESCRIPTION

[0033] Below, the embodiments of the electrolyte, battery cells containing the electrolyte, batteries, and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0034] In the description of this application, it should be noted that, unless otherwise specified, "plurality" means more than two; terms such as "upper," "lower," "left," "right," "inner," and "outer" indicating directions or positional relationships are merely for the purpose of facilitating the description of this application and simplifying the description, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting this application. Furthermore, terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0035] " scope " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and selected lower limit and upper limit define the boundary of special scope.The scope that this mode limits can be to include end value or not include end value, and can be combined arbitrarily, and promptly any lower limit can form a scope with any upper limit combination.For example, if the scope of 60-120 and 80-110 is listed for specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected.In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are listed, then the following scope can all be expected: 1-3,1-4,1-5,2-3,2-4 and 2-5.In the present application, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, and wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0037] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0038] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0039] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0040] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0041] Unless otherwise specified, the following terms have the following meanings. Any undefined terms have their generally accepted meanings in the art.

[0042] "Alkyl" refers to a monovalent saturated hydrocarbon group having one or more carbon atoms. For example, alkyl includes straight-chain alkyl and branched-chain alkyl groups, such as methyl (CH3-), ethyl (CH3CH2-), n-propyl (CH3CH2CH2-), isopropyl ((CH3)2CH-), n-butyl (CH3CH2CH2CH2-), isobutyl ((CH3)2CHCH2-), sec-butyl ((CH3)(CH3CH2)CH-), tert-butyl ((CH3)3C-), n-pentyl (CH3CH2CH2CH2CH2-), neopentyl ((CH3)3CCH2-), etc.

[0043] "Substituted alkyl" refers to an alkyl group in which one or more carbon atoms in a straight or branched chain are replaced by any heteroatom or substituent. Alternatively, the substituent may be an isocyanate.

[0044] "Aryl" refers to an aromatic compound having a single ring or multiple condensed rings. For example, aryl includes phenyl, naphthyl, indenyl, etc. Aryl also includes a single ring fused to an aryl group, for example, tetrahydronaphthyl, 2,3-dihydroindanyl, etc.

[0045] "Phenyl" refers to a group having a benzene ring as a functional group.

[0046] "Halophenyl" refers to a benzene ring in which one or more hydrogen atoms are replaced by a halogen atom.

[0047] The "halogen atom" refers to fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

[0048] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are embedded in and released from the positive and negative electrodes. The electrolyte in the electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, prevents a short circuit while allowing ions to pass through, ensuring the normal electrochemical reactions in the secondary battery.

[0049] Secondary batteries can include lithium-ion batteries, sodium-ion batteries, magnesium-ion batteries, and others. This application uses lithium-ion batteries as an example. Lithium-ion batteries are a typical type of secondary battery. Because they rely on chemical reactions involving the intercalation and deintercalation of lithium ions between the positive and negative electrodes for charging and discharging, lithium-ion batteries are also known as rocking-chair batteries. During charging, lithium ions are released from the positive electrode, moved to the negative electrode, and then intercalated into the positive electrode. During discharge, lithium ions are released from the negative electrode, moved to the positive electrode, and then intercalated into the positive electrode.

[0050] In recent years, secondary batteries have developed greatly and are widely used in power tools, electronic products, electric vehicles, aerospace and other fields. At the same time, higher requirements are placed on the volume capacity, energy density, cycle performance, service life, safety performance, etc. of secondary batteries.

[0051] The battery's electrode material has a large specific surface area and is easy to absorb water. During the use of the battery, the water adsorbed by the electrode material will diffuse into the electrolyte and react with the lithium salt in the electrolyte to generate acidic substances, causing the electrolyte to deteriorate and increasing the internal resistance of the battery. At the same time, it will corrode the electrode interface film and affect the battery's service life.

[0052] In view of this, the present application provides an electrolyte comprising a first additive and a lithium salt. The first additive comprises an isocyanate compound, and the lithium salt comprises lithium bis(fluorosulfonyl)imide. The isocyanate compound has good acid binding capacity, which can reduce the influence of moisture on battery performance. At the same time, it will participate in the formation of the electrode interface film, improve the thermal stability of the electrode interface film, reduce the possibility of gas production and expansion of the battery, and improve the cycle performance and storage life of the battery. However, the isocyanate compound will affect the kinetic performance of the battery and increase the film formation impedance of the electrode interface film, while lithium bis(fluorosulfonyl)imide easily dissociates into lithium ions in the electrolyte, increases the electrical conductivity of the battery, improves the kinetic performance of the battery, and reduces the film formation impedance of the electrode interface film. By adding the isocyanate compound and lithium bis(fluorosulfonyl)imide to the electrolyte at the same time, the kinetic performance of the battery is taken into account while improving the cycle life and storage performance of the battery. Furthermore, due to the low oxidation potential of lithium bis(fluorosulfonyl)imide, it is easy to corrode the aluminum foil of the electrode plate during battery use and increase the risk of thermal runaway of the battery. Therefore, it is necessary to mix lithium bis(fluorosulfonyl)imide with other types of lithium salts and control the weight content of lithium bis(fluorosulfonyl)imide in the total lithium salt to be 30% to 85%. While ensuring that the content of lithium bis(fluorosulfonyl)imide can effectively improve the dynamic performance of the cell, the content of lithium bis(fluorosulfonyl)imide is controlled not too high, reducing the possibility of lithium bis(fluorosulfonyl)imide corroding the aluminum foil, increasing the service life of the battery, and reducing the risk of thermal runaway of the battery. In other words, the technical solution provided by the embodiment of the present application not only improves the cycle performance and storage life of the battery, but also reduces the risk of thermal runaway of the battery.

[0053] The following describes in detail several embodiments of the present application.

[0054] [Electrolyte]

[0055] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The electrolyte provided in this application includes a first additive and a lithium salt. Specifically, the first additive includes an isocyanate compound represented by formula (I):

[0056] Wherein, R includes at least one of a hydrogen atom, a halogen atom, a nitrogen-containing group, an oxygen-containing group, a sulfur-containing group, a phosphorus-containing group, an alkyl group, a cycloalkyl group, a phenyl group, an aryl group, a halogenated phenyl group, and an alkyl group, cycloalkyl group, a phenyl group, an aryl group, and a halogenated phenyl group containing at least one isocyanate group, and the value of n is any natural number between 0 and 8.

[0057] The lithium salt includes lithium bis(fluorosulfonyl)imide. Based on the total weight of the lithium salt, the weight content of lithium bis(fluorosulfonyl)imide in the lithium salt is 30% to 85%.

[0058] Specifically, the electrolyte provided in the embodiments of the present application includes both an isocyanate compound and lithium bis(fluorosulfonyl)imide. The isocyanate compound has good acid binding capacity, which can reduce the impact of moisture on battery performance. At the same time, it will participate in the film formation of the electrode interface film, improve the thermal stability of the electrode interface film, reduce the possibility of battery gas expansion, and improve the cycle performance and storage life of the battery. However, the isocyanate compound will affect the kinetic performance of the battery and increase the film formation impedance of the electrode interface film, while lithium bis(fluorosulfonyl)imide easily dissociates into lithium ions in the electrolyte, improving the electrical conductivity of the battery, improving the kinetic performance of the battery, and reducing the film formation impedance of the electrode interface film.

[0059] Therefore, the electrolyte provided in the embodiment of the present application adds an isocyanate compound and lithium bis(fluorosulfonyl)imide to the electrolyte at the same time, which improves the cycle life and storage performance of the battery while taking into account the dynamic performance of the battery. Furthermore, since lithium bis(fluorosulfonyl)imide has a low oxidation potential, it will easily corrode the aluminum foil of the electrode plate during the use of the battery and increase the risk of thermal runaway of the battery. Therefore, it is necessary to mix lithium bis(fluorosulfonyl)imide with other types of lithium salts and control the weight content of lithium bis(fluorosulfonyl)imide in the total lithium salt to be 30% to 85%. While ensuring that the content of lithium bis(fluorosulfonyl)imide can effectively improve the dynamic performance of the cell, the content of lithium bis(fluorosulfonyl)imide is controlled not to be too high, reducing the possibility of lithium bis(fluorosulfonyl)imide corroding the aluminum foil, increasing the service life of the battery, and reducing the risk of thermal runaway of the battery. In other words, the technical solution provided in the embodiment of the present application not only improves the cycle performance and storage life of the battery, but also reduces the risk of thermal runaway of the battery.

[0060] Optionally, in some embodiments, the first additive includes at least one of the following substances:

[0061] It should be understood that the isocyanate compound included in the first additive provided in the embodiment of the present application is only for example and should not be understood as limiting the isocyanate compound of the present application.

[0062] Optionally, in some embodiments, the weight ratio of lithium bis(fluorosulfonyl)imide to the isocyanate compound in the electrolyte is 6:1 to 20:0.001.

[0063] Specifically, the weight ratio of lithium bis(fluorosulfonyl)imide to the isocyanate compound in the electrolyte can be 6:1, 12:1, 24:1, 48:1, 96:1, 192:1, 384:1, 768:1, 1.536:0.001, 3.072:0.001, 6.144:0.001, 12.288:0.001, 20:0.001, or the ratio value is within the range obtained by combining any two of the above ratio values.

[0064] The weight ratio of lithium bis(fluorosulfonyl)imide to isocyanate compound in the electrolyte needs to be within an appropriate range, which can not only ensure the acid binding capacity of the isocyanate compound, reduce the impact of moisture on battery performance, and improve the cycle performance and storage life of the battery, but also enable lithium bis(fluorosulfonyl)imide to offset the adverse effect of the isocyanate compound on increasing the film formation impedance of the electrode interface film, thereby improving the dynamic performance of the battery.

[0065] Optionally, in some embodiments, based on the total weight of the electrolyte, the weight content of lithium bis(fluorosulfonyl)imide in the electrolyte is 3% to 20%.

[0066] Specifically, the weight content of lithium bis(fluorosulfonyl)imide in the electrolyte can be 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%, 18.5%, 19%, 19.5%, 20%, or its value is within the range obtained by combining any two of the above values.

[0067] A high weight content of lithium bis(fluorosulfonyl)imide in the electrolyte will increase the lithium salt concentration, which in turn increases the viscosity of the electrolyte, deteriorating the low-temperature performance of the battery and increasing the battery production cost. A low weight content of lithium bis(fluorosulfonyl)imide in the electrolyte will not effectively improve the battery's kinetic performance. Therefore, the weight content of lithium bis(fluorosulfonyl)imide in the electrolyte is set to 3% to 20%.

[0068] Optionally, in some embodiments, the weight content of the isocyanate compound in the electrolyte is 0.001% to 0.5% based on the total weight of the electrolyte. Optionally, the weight content of the isocyanate compound in the electrolyte is 0.005% to 0.3%. Further optionally, the weight content of the isocyanate compound in the electrolyte is 0.01% to 0.1%.

[0069] Specifically, the weight content of the isocyanate compound in the electrolyte can be 0.001%, 0.0015%, 0.002%, 0.0025%, 0.003%, 0.0035%, 0.004%, 0.0045%, 0.005%, 0.0055%, 0.006%, 0.0065%, 0.007%, 0.0075%, 0.008%, 0.0085%, 0.009%, 0.0095%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or a value within the range obtained by combining any two of the above values.

[0070] An excessively high isocyanate content in the electrolyte significantly increases the film formation resistance of the electrode interface film and affects the battery's charging capacity. An excessively low isocyanate content in the electrolyte binds less hydrofluoric acid, and the remaining free hydrofluoric acid in the electrolyte can affect battery performance. Therefore, the isocyanate content in the electrolyte is set to 0.001% to 0.5% by weight.

[0071] Optionally, in some embodiments, the lithium salt further includes at least one of lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium difluorophosphate, and lithium hexafluorophosphate.

[0072] Lithium bis(fluorosulfonyl)imide reacts with the aluminum foil of the electrode plate to form a complex. This complex is unstable. After dissolving in a solvent, the lithium bis(fluorosulfonyl)imide can continue to react with the aluminum foil, causing continuous corrosion over time. If the lithium salt includes at least one of the above substances, these substances can form a stable coordination compound with the aluminum foil, AlF3 and LiF, forming a stable passivation layer that prevents further corrosion of the aluminum foil.

[0073] Optionally, in some embodiments, the electrolyte further includes a second additive, and the second additive includes at least one of carbonate, sulfonate, and fluorinated compound.

[0074] Specifically, the second additive includes at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), bisfluoroethylene carbonate (DFEC), vinyl ethylene carbonate (VEC), diethylene sulfate (DTD), and 1,3-propane sultone.

[0075] The content of isocyanate compounds in the electrolyte is limited. In order to ensure that the total amount of additives in the electrolyte is sufficient, other additives need to be added to reduce the risk of battery diving. In addition, carbonates, sulfonates and fluorinated compounds can participate in the formation of electrode interface films, help form a stable interface film, and improve the battery's cycle performance and storage life.

[0076] Optionally, in some embodiments, the electrolyte further includes a solvent, and the solvent includes at least one of a cyclic ester and a chain ester.

[0077] Specifically, the solvent includes at least one of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, γ-butyrolactone, tetrahydrofuran, sulfolane, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl formate, methyl acetate, ethyl acetate, methyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

[0078] Ester solvents generally have the advantages of low melting point and high dielectric constant. Adding ester solvents such as cyclic esters and chain esters to the electrolyte can effectively reduce the viscosity of the electrolyte and increase the conductivity of the electrolyte, thereby achieving the purpose of improving the low-temperature performance and rate performance of the electrolyte.

[0079] The battery cell, battery and electrical device of the present application are described below with reference to the accompanying drawings.

[0080] The present application also provides a battery cell. Typically, a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the battery's charge and discharge process, active ions are embedded and released back and forth between the positive and negative electrode sheets. The electrolyte in the electrolyte acts as an ion conductor between the positive and negative electrode sheets. The separator is disposed between the positive and negative electrode sheets, primarily to prevent a short circuit between the positive and negative electrodes while allowing ions to pass through.

[0081] It should be understood that the "embedding" process described in this application refers to the process in which active ions are embedded in the positive electrode active material or the negative electrode active material due to an electrochemical reaction, and the "extraction" and "de-intercalation" processes described in this application refer to the process in which active ions are removed from the positive electrode active material or the negative electrode active material due to an electrochemical reaction.

[0082] [Positive electrode]

[0083] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0084] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0085] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0086] In some embodiments, the positive electrode active material may be a positive electrode active material for lithium ion batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates containing olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for lithium ion batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0087] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0088] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0089] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0090] [Negative electrode]

[0091] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0092] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0093] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0094] In some embodiments, the negative electrode active material may adopt negative electrode active materials for batteries that are well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0095] In some embodiments, the negative electrode film layer may further include a binder. The binder may include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0096] In some embodiments, the negative electrode film layer may further include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0097] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0098] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0099] [Isolation film]

[0100] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0101] In some embodiments, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0102] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0103] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0104] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0105] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 20 having a square structure as an example.

[0106] In some embodiments, referring to Figure 2, the outer packaging may include a shell 21 and a cover plate 23. The shell 21 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 21 has an opening connected to the receiving cavity, and the cover plate 23 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 22 through a winding process or a lamination process. The electrode assembly 22 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 22. The number of electrode assemblies 22 contained in the battery cell 20 can be one or more, and those skilled in the art can select according to specific actual needs.

[0107] In some embodiments, the battery 10 may include multiple battery cells 20. For example, FIG3 is a schematic structural diagram of a battery 10 according to one embodiment of the present application. The battery 10 may include multiple battery cells 20. The battery 10 may also include a housing 11 having a hollow interior and housing the multiple battery cells 20. For example, the multiple battery cells 20 may be connected in parallel, in series, or in a mixed combination and then placed in the housing 11.

[0108] Optionally, the battery 10 may also include other structures, which will not be described in detail here. For example, the battery 10 may also include a busbar component, which is used to achieve electrical connection between multiple battery cells 20, such as parallel connection, series connection, or mixed connection. Specifically, the busbar component can achieve electrical connection between the battery cells 20 by connecting the electrode terminals of the battery cells 20. Furthermore, the busbar component can be fixed to the electrode terminals of the battery cells 20 by welding. The electrical energy of the multiple battery cells 20 can be further led out through the box 11 through a conductive mechanism. Optionally, the conductive mechanism may also belong to the busbar component.

[0109] The number of battery cells 20 can be set to any value based on different power requirements. Multiple battery cells 20 can be connected in series, parallel, or in a hybrid manner to achieve higher capacity or power. Since each battery 10 may include a large number of battery cells 20, for ease of installation, the battery cells 20 can be grouped, with each group of battery cells 20 forming a battery module. The number of battery cells 20 included in a battery module is not limited and can be set according to requirements. A battery can include multiple battery modules, which can be connected in series, parallel, or in a hybrid manner.

[0110] In addition, the present application also provides an electric device, which includes at least one of the battery cells, battery modules or batteries provided in the present application. The battery cells, battery modules or batteries can be used as the power source of the electric device, and can also be used as the energy storage unit of the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0111] As the electrical device, a battery cell, a battery module or a battery can be selected according to its usage requirements.

[0112] Figure 4 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery cell, a battery or battery module can be used.

[0113] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0114] [Example]

[0115] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0116] (1) Preparation of battery cells

[0117] (1.1) Preparation of positive electrode sheet

[0118] Lithium iron phosphate (LFP) with an olivine structure, polyvinylidene fluoride (PVDF), and carbon black (SP) are mixed with a solvent in a mass ratio of 97:2.5:0.5, and stirred to obtain a uniformly dispersed positive electrode slurry. The positive electrode slurry is evenly coated on both surfaces of the aluminum foil, and then dried, cold pressed, and cut to obtain a positive electrode sheet.

[0119] (1.2) Preparation of negative electrode sheet

[0120] The negative electrode active materials artificial graphite, carbon black (SP), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) are mixed with a solvent in a mass ratio of 97:0.5:1.5:1, and stirred to obtain a uniformly dispersed negative electrode slurry. The negative electrode slurry is evenly coated on both surfaces of the copper foil, and then dried, cold pressed, and cut to obtain the negative electrode sheet.

[0121] (1.3) Preparation of isolation membrane

[0122] Conventional polyethylene film is used as the separator.

[0123] (1.4) Preparation of electrolyte

[0124] Electrolyte 1: In an argon environment, based on the total mass of the electrolyte, 25% of ethylene carbonate (EC), 55% of dimethyl carbonate (DMC), 20% of ethyl methyl carbonate (EMC), 2% of vinylene carbonate (VC), 0.5% of hexamethylene diisocyanate, 7% of lithium hexafluorophosphate (LiPF6), and 3% of lithium difluorosulfonimide (LiFSI) were mixed and dissolved to obtain electrolyte 1.

[0125] Electrolyte 2: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.3% of hexamethylene diisocyanate by mass, 7% of LiPF6 by mass, and 3% of LiFSI by mass were mixed and dissolved to obtain electrolyte 2.

[0126] Electrolyte 3: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.1% of hexamethylene diisocyanate by mass, 7% of LiPF6 by mass, and 3% of LiFSI by mass were mixed and dissolved to obtain electrolyte 3.

[0127] Electrolyte 4: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.1% of hexamethylene diisocyanate by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 4.

[0128] Electrolyte 5: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.1% of hexamethylene diisocyanate by mass, 1.5% of LiPF6 by mass, and 8.5% of LiFSI by mass were mixed and dissolved to obtain electrolyte 5.

[0129] Electrolyte 6: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.1% of hexamethylene diisocyanate by mass, 10% of LiPF6 by mass, and 10% of LiFSI by mass were mixed and dissolved to obtain electrolyte 6.

[0130] Electrolyte 7: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of carbon DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.1% of hexamethylene diisocyanate by mass, 5% of LiPF6 by mass, and 15% of LiFSI by mass were mixed and dissolved to obtain electrolyte 7.

[0131] Electrolyte 8: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.1% of hexamethylene diisocyanate by mass, 3% of LiPF6 by mass, and 17% of LiFSI by mass were mixed and dissolved to obtain electrolyte 8.

[0132] Electrolyte 9: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.01% of hexamethylene diisocyanate by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 9.

[0133] Electrolyte 10: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.002% of hexamethylene diisocyanate by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 10.

[0134] Electrolyte 11: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.001% of hexamethylene diisocyanate by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 11.

[0135] Electrolyte 12: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.001% of hexamethylene diisocyanate by mass, 5% of LiPF6 by mass, and 15% of LiFSI by mass were mixed and dissolved to obtain electrolyte 12.

[0136] Electrolyte 13: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.001% of hexamethylene diisocyanate by mass, 3.5% of LiPF6 by mass, and 20% of LiFSI by mass were mixed and dissolved to obtain electrolyte 13.

[0137] Electrolyte 14: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.1% of toluene diisocyanate by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 14.

[0138] Electrolyte 15: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.1% of p-fluorophenyl isocyanate by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 15.

[0139] Electrolyte 16: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.1% of p-cyanophenyl isocyanate by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 16.

[0140] Electrolyte 17: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 1% of VC by mass, 1% of fluoroethylene carbonate (FEC) by mass, 0.1% of hexamethylene diisocyanate by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass are mixed and dissolved to obtain electrolyte 17.

[0141] Electrolyte 18: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 1% of VC by mass, 1% of vinyl sulfate (DTD) by mass, 0.1% of hexamethylene diisocyanate by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass are mixed and dissolved to obtain electrolyte 18.

[0142] Electrolyte 19: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 1% of VC by mass, 1% of 1,3-propane sultone by mass, 0.1% of hexamethylene diisocyanate by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 19.

[0143] Electrolyte 20: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 0.1% of hexamethylene diisocyanate by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 20.

[0144] Electrolyte 21: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 7% of LiPF6 by mass, and 3% of LiFSI by mass were mixed and dissolved to obtain electrolyte 21.

[0145] Electrolyte 22: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 22.

[0146] Electrolyte 23: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 1.5% of LiPF6 by mass, and 8.5% of LiFSI by mass were mixed and dissolved to obtain electrolyte 23.

[0147] Electrolyte 24: In an argon environment, based on the total mass of the electrolyte, 25% by mass of EC, 55% by mass of DMC, 20% by mass of EMC, 2% by mass of VC, 10% by mass of LiPF6, and 10% by mass of LiFSI were mixed and dissolved to obtain electrolyte 24.

[0148] Electrolyte 25: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 5% of LiPF6 by mass, and 15% of LiFSI by mass were mixed and dissolved to obtain electrolyte 25.

[0149] Electrolyte 26: In an argon environment, based on the total mass of the electrolyte, 25% by mass of EC, 55% by mass of DMC, 20% by mass of EMC, 2% by mass of VC, 3.5% by mass of LiPF6, and 20% by mass of LiFSI were mixed and dissolved to obtain electrolyte 26.

[0150] Electrolyte 27: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 1% of VC by mass, 1% of FEC by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 27.

[0151] Electrolyte 28: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 1% of VC by mass, 1% of DTD by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 28.

[0152] Electrolyte 29: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 1% of VC by mass, 1% of 1,3-propane sultone by mass, 4% of LiPF6 by mass, and 6% of LiFSI by mass were mixed and dissolved to obtain electrolyte 29.

[0153] Electrolyte 30: In an argon environment, based on the total mass of the electrolyte, 25% by mass of EC, 55% by mass of DMC, 20% by mass of EMC, 2% by mass of VC, 0.1% by mass of hexamethylene diisocyanate, and 10% by mass of LiPF6 were mixed and dissolved to obtain electrolyte 30.

[0154] Electrolyte 31: In an argon environment, based on the total mass of the electrolyte, 25% of EC by mass, 55% of DMC by mass, 20% of EMC by mass, 2% of VC by mass, 0.001% of hexamethylene diisocyanate by mass, 3.5% of LiPF6 by mass, and 30% of LiFSI by mass were mixed and dissolved to obtain electrolyte 31.

[0155] (1.5) Assembly of battery cells

[0156] The positive electrode sheet, negative electrode sheet and separator are made into an electrode assembly through a winding process or a lamination process, and placed in a shell made of an aluminum shell, aluminum-plastic film, etc. After the above-mentioned different electrolytes are injected, left to stand at high temperature, formed, and divided into volumes, the battery cells in different embodiments and comparative examples are obtained.

[0157] Example 1: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 1 according to the above-mentioned method is Example 1.

[0158] Example 2: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 2 according to the above-mentioned method is Example 2.

[0159] Example 3: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 3 according to the above-mentioned method is Example 3.

[0160] Example 4: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 4 according to the above-mentioned method is Example 4.

[0161] Example 5: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 5 according to the above-mentioned method is Example 5.

[0162] Example 6: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 6 according to the above-mentioned method is Example 6.

[0163] Example 7: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 7 according to the above-mentioned method is Example 7.

[0164] Example 8: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 8 according to the above-mentioned method is Example 8.

[0165] Example 9: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 9 according to the above method is Example 9.

[0166] Example 10: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 10 according to the above-mentioned method is Example 10.

[0167] Example 11: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 11 according to the above method is Example 11.

[0168] Example 12: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 12 according to the above method is Example 12.

[0169] Example 13: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 13 according to the above method is Example 13.

[0170] Example 14: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 14 according to the above method is Example 14.

[0171] Example 15: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 15 according to the above method is Example 15.

[0172] Example 16: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 16 according to the above method is Example 16.

[0173] Example 17: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 17 according to the above method is Example 17.

[0174] Example 18: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 18 according to the above method is Example 18.

[0175] Example 19: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 19 according to the above method is Example 19.

[0176] Example 20: The battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 20 according to the above-mentioned method is Example 20.

[0177] Comparative Example 1: A battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 21 according to the above-mentioned method is Comparative Example 1.

[0178] Comparative Example 2: A battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 22 according to the above-mentioned method is Comparative Example 2.

[0179] Comparative Example 3: A battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 23 according to the above-mentioned method is Comparative Example 3.

[0180] Comparative Example 4: A battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 24 according to the above-mentioned method is Comparative Example 4.

[0181] Comparative Example 5: A battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 25 according to the above-mentioned method is Comparative Example 5.

[0182] Comparative Example 6: A battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 26 according to the above-mentioned method is Comparative Example 6.

[0183] Comparative Example 7: A battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 27 according to the above-mentioned method is Comparative Example 7.

[0184] Comparative Example 8: A battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 28 according to the above-mentioned method is Comparative Example 8.

[0185] Comparative Example 9: A battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 29 according to the above-mentioned method is Comparative Example 9.

[0186] Comparative Example 10: A battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 30 according to the above-mentioned method is Comparative Example 10.

[0187] Comparative Example 11: A battery cell obtained by assembling the above-mentioned positive electrode sheet, separator, negative electrode sheet, and electrolyte 31 according to the above-mentioned method is Comparative Example 11.

[0188] The product parameters of different embodiments are detailed in Table 1.

[0189] Next, the testing process of relevant parameters is explained.

[0190] (2) Battery performance test

[0191] (2.1) Determination of initial direct current resistance (DCR)

[0192] At room temperature, the batteries of each embodiment and comparative example were charged at a constant current of 0.5C to 3.65V, then charged at a constant voltage to a current of 0.05C. The batteries were discharged at a constant current of 0.5C for 60 minutes to adjust the battery to 50% SOC. The battery voltage at this time was recorded as U1. The battery was discharged at a constant current of 4C for 30 seconds, with a sampling point at 0.1 seconds. The voltage at the end of discharge was recorded as U2. The discharge DCR of the battery at 50% SOC represents the initial DCR of the battery: initial DCR = (U1 - U2) / 4C.

[0193] (2.2) Determination of 60℃ high temperature cycle performance

[0194] At 60°C, the batteries of each Example and Comparative Example were charged at a constant current of 1C to 3.65V, then charged at a constant voltage to a current of 0.05C. The batteries were allowed to rest for 5 minutes and then discharged at a constant current of 1C to 2.5V. This constituted the first charge-discharge cycle of the battery, and the discharge capacity at this time was recorded as the discharge capacity of the battery's first cycle. The batteries were charged and discharged 1000 times using this method, and the discharge capacity after 1000 cycles was recorded.

[0195] The capacity retention rate (%) of the battery after 1000 cycles at 60° C. = (discharge capacity of the battery after 1000 cycles / discharge capacity of the battery in the first cycle)×100%.

[0196] (2.3) Determination of 60℃ high temperature storage performance

[0197] At 25°C, the batteries of each embodiment and comparative example were charged to 3.65V at a constant current of 1 / 3C, and then charged to a current of 0.05C at a constant voltage. 100% SOC batteries were placed in a 60°C high and low temperature box, and the battery's true capacity was tested every 30 days (1 / 3C discharge to 2.5V, 0.04C discharge to 2.0V, recording the battery's true capacity and charging to 3.65V at 1 / 3C). The battery was then placed in a 60°C high and low temperature box and discharged to 2.5V at a constant current of 1 / 3C. This was the first charge and discharge cycle of the battery, and the discharge capacity was recorded as the discharge capacity of the first cycle. The battery was charged and discharged 1000 times according to the above method, and the discharge capacity after 1000 cycles was recorded.

[0198] The capacity retention rate (%) of the battery after 1000 cycles at 60° C. = (discharge capacity of the battery after 1000 cycles / discharge capacity of the battery in the first cycle)×100%.

[0199] The battery performance tests of Examples 1-20 and Comparative Examples 1-11 were carried out according to the above method. The results are shown in Table 2.

[0200] Table 2: Performance test results of comparative examples and different embodiments

[0201] From the comparison of the results of Comparative Example 1 with Examples 1-3, Comparative Example 2 with Example 4, Comparative Example 3 with Example 5, Comparative Example 4 with Example 6, Comparative Example 5 with Example 7, Comparative Example 6 with Example 8, Comparative Example 7 with Example 17, Comparative Example 8 with Example 18, and Comparative Example 9 with Example 19, it can be seen that the isocyanate compound can effectively improve the cycle performance and storage life of the battery, while also increasing the DCR of the battery.

[0202] Comparing the results of Comparative Example 10 with those of Examples 3-8 shows that adding LiFSI to the electrolyte can reduce the DCR of the battery. In other words, adding both an isocyanate compound and LiFSI to the electrolyte can effectively improve the battery's cycle performance and storage life while also reducing the battery's DCR.

[0203] From the comparison of the results of Comparative Example 10 with Examples 3-8, and Comparative Example 11 with Example 13, it can be seen that when the weight content ratio of LiFSI to the isocyanate compound in the electrolyte is too small, and the proportion of LiFSI in the total lithium salt is too small, LiFSI cannot effectively offset the adverse effect of the isocyanate compound on increasing the film-forming impedance of the electrode interface film, resulting in a larger DCR value of the battery. When the weight content ratio of LiFSI to the isocyanate compound in the electrolyte is too large, and the proportion of LiFSI in the total lithium salt is too large, LiFSI will corrode the aluminum foil, resulting in a decrease in the cycle performance of the battery and a decrease in the storage life. Controlling the weight content ratio of LiFSI to the isocyanate compound in the electrolyte within an appropriate range can not only ensure the acid binding capacity of the isocyanate compound, reduce the effect of moisture on battery performance, improve the cycle performance and storage life of the battery, but also enable lithium bis(fluorosulfonyl)imide to offset the adverse effect of the isocyanate compound on increasing the film-forming impedance of the electrode interface film, thereby improving the dynamic performance of the battery.

[0204] From the comparison of the results of Example 4 and Examples 9-11, it can be seen that within the appropriate range, the higher the content of the isocyanate compound in the electrolyte, the more obvious the improvement in the cycle performance and storage life of the battery, and the greater the DCR value of the battery.

[0205] From the comparison of the results of Examples 3-5, it can be seen that within an appropriate range, the higher the weight content of LiFSI in the total lithium salt, the smaller the DCR value of the battery.

[0206] Comparison of the results of Example 20, Example 4, and Examples 17-19 shows that adding a second additive (at least one of VC, FEC, DTD, and 1,3-propane sultone) to the electrolyte simultaneously with the addition of the isocyanate compound ensures a sufficient total amount of additives in the electrolyte, thereby reducing the risk of battery leakage. Furthermore, the second additive forms monomeric active free radicals during electrochemical reactions, which, together with the isocyanate compound, contribute to the formation of the electrode interface film. This results in a higher molecular weight and a denser, more compact electrode interface film, further improving the quality of the initial film formation.

[0207] The above-mentioned examples of the present application and comparative examples all used lithium iron phosphate batteries for experimental testing. The positive electrode material of the lithium iron phosphate battery is lithium iron phosphate. The lithium iron phosphate material has a large specific surface area and is more likely to absorb water, which has a greater impact on the performance of the lithium iron phosphate battery. The examples of the present application and comparative examples used lithium iron phosphate batteries to test the effect of isocyanate compounds and LiFSI on improving battery performance, and the experimental results were more obvious. From the analysis of the above experimental data, it can be seen that adding isocyanate compounds and LiFSI to the electrolyte at the same time greatly improves the cycle performance and storage life of the lithium iron phosphate battery.

[0208] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An electrolyte comprising: A first additive, wherein the first additive comprises an isocyanate compound represented by formula (I); Wherein, R includes at least one of a hydrogen atom, a halogen atom, a nitrogen-containing group, an oxygen-containing group, a sulfur-containing group, a phosphorus-containing group, an alkyl group, a cycloalkyl group, a phenyl group, an aryl group, a halogenated phenyl group, and an alkyl group, a cycloalkyl group, a phenyl group, an aryl group, and a halogenated phenyl group containing at least one isocyanate group, and the value of n is any natural number between 0 and 8; The lithium salt comprises lithium bis(fluorosulfonyl)imide, and the weight content of the lithium bis(fluorosulfonyl)imide in the lithium salt is 30% to 85% based on the total weight of the lithium salt.

2. The electrolyte according to claim 1, wherein The first additive includes at least one of the following substances:

3. The electrolyte according to claim 1 or 2, wherein The weight ratio of the lithium bis(fluorosulfonyl)imide to the isocyanate compound in the electrolyte is 6:1 to 20:0.

001.

4. The electrolyte according to any one of claims 1 to 3, wherein Based on the total weight of the electrolyte, the weight content of the lithium bis(fluorosulfonyl)imide in the electrolyte is 3% to 20%.

5. The electrolyte according to any one of claims 1 to 4, wherein Based on the total weight of the electrolyte, the weight content of the isocyanate compound in the electrolyte is 0.001% to 0.5%. Optionally, the weight content of the isocyanate compound in the electrolyte is 0.005% to 0.3%. Further optionally, the weight content of the isocyanate compound in the electrolyte is 0.01% to 0.1%.

6. The electrolyte according to any one of claims 1 to 5, wherein The lithium salt further comprises at least one of lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium difluorophosphate and lithium hexafluorophosphate.

7. The electrolyte according to any one of claims 1 to 6, wherein The electrolyte further includes a second additive, and the second additive includes at least one of carbonate, sulfonate, and fluorinated compound.

8. The electrolyte according to claim 7, wherein The second additive includes at least one of vinylene carbonate, fluoroethylene carbonate, bisfluoroethylene carbonate, vinyl ethylene carbonate, vinyl sulfate, and 1,3-propane sultone.

9. The electrolyte according to any one of claims 1 to 8, wherein The electrolyte further includes a solvent, and the solvent includes at least one of a cyclic ester and a chain ester.

10. The electrolyte according to claim 9, wherein The solvent includes at least one of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, γ-butyrolactone, tetrahydrofuran, cyclopentane, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl formate, methyl acetate, ethyl acetate, methyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

11. A battery cell comprising the electrolyte according to any one of claims 1 to 10. 12 . A battery comprising the battery cell according to claim 11 .

13. An electrical device comprising the battery according to claim 12.

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