Electrolyte additive, electrolyte, secondary battery, and electric device

Abstract

The invention provides an electrolyte additive, an electrolyte, a secondary battery and an electric device. The electrolyte additive comprises a compound as shown in a formula I, wherein R1 comprises at least one of F, Cl and halogen substituted or unsubstituted C1-C4 alkyl; r2 contains at least one of H, halogen, substituted or unsubstituted C1-C4 alkyl, silyl, phenyl, carbonyl, sulfinyl or cyano, and a substituent group of the C1-C4 alkyl contains at least one of F and Cl; and R3 contains at least one of H, halogen, halogen substituted or unsubstituted C1-C4 alkyl, silyl, phenyl, carbonyl, sulfinyl and cyano.

Description

Electrolyte additive, electrolyte, secondary battery and electrical device Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to an electrolyte additive, an electrolyte, a secondary battery, and an electrical device. Background Art

[0002] In recent years, secondary batteries 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 widespread use of secondary batteries, higher requirements have been placed on their energy density and cycle performance.

[0003] The electrolyte is the carrier for ion transport in secondary batteries, conducting ions between the positive and negative electrodes. However, during the charge and discharge process of secondary batteries, the electrolyte easily decomposes to produce byproducts, leading to a significant decline in battery performance and even causing safety issues.

[0004] Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide an electrolyte additive that can form a stable interfacial protective film on the electrode surface, reduce the oxidative decomposition of the electrolyte, inhibit gas production, and improve the safety performance, cycle performance, and service life of the battery.

[0006] The first aspect of the present application provides an electrolyte additive, which comprises a compound shown in formula I,

[0007] in, It means that N and R2, N and R3 are all connected by single bonds, or N and R3 are connected by double bonds, and there is no bond between N and R2; R1 contains at least one of F, Cl, halogen-substituted or unsubstituted C1-C4 hydrocarbon groups; R2 contains at least one of H, halogen, substituted or unsubstituted C1-C4 hydrocarbon groups, silanyl, phenyl, carbonyl, sulfinyl or cyano groups, wherein the substituent group of the C1-C4 hydrocarbon group contains at least one of F and Cl; R3 contains H, halogen, halogen-substituted or unsubstituted C1-C4 hydrocarbon groups, silanyl, phenyl, carbonyl, sulfinyl, cyano or At least one of, wherein R4 comprises at least one of a carbonyl group, a substituted or unsubstituted C1-C6 hydrocarbon group, the substituent of the C1-C6 hydrocarbon group comprises at least one of F, Cl, a silyl group, a phenyl group, a carbonyl group, a sulfinyl group, and a cyano group, R5 comprises at least one of H, F, a substituted or unsubstituted C1-C4 hydrocarbon group, the substituent of the C1-C4 hydrocarbon group comprises at least one of F, Cl, a silyl group, a phenyl group, a carbonyl group, a sulfinyl group, and a cyano group, and R6 comprises at least one of F, Cl, a halogen-substituted or unsubstituted C1-C4 hydrocarbon group.

[0008] The electrolyte additive provided by the present application can reduce the content of water and hydrofluoric acid in the electrolyte by reacting with byproducts such as water or hydrofluoric acid, thereby reducing the deterioration of battery performance caused by byproducts; at the same time, it participates in the electrochemical reaction at the interface between the negative electrode active material and the electrolyte to generate inorganic products containing S and N, thereby improving the thermal stability and chemical stability of the interface. In addition, the electron-rich N and the strongly electron-withdrawing -SO2- in the electrolyte additive have high binding stability and are not prone to thermal decomposition reactions, thereby optimizing the cycle stability and storage stability of the battery, especially at high temperatures. The structure will not react with the current collector metal to generate byproducts soluble in the electrolyte, causing current collector corrosion, thereby further improving the cycle stability of the battery.

[0009] In any embodiment, R1 comprises F or -CF3.

[0010] When halogen is included in the electrolyte additive, the reaction activity is further improved and the cycle performance of the battery is further optimized.

[0011] In any embodiment, the chemical bond between N and R3 is a single bond, and R3 comprises H, halogen, halogen-substituted C1-C4 hydrocarbon group, cycloalkyl, phenyl, carbonyl, sulfinyl, cyano or At least one of .

[0012] In any embodiment, the chemical bond between N and R3 is a single bond, and R3 comprises

[0013] When each mole of the electrolyte additive contains at least two moles of -N-SO2- groups, it can more efficiently reduce the internal resistance of the battery and improve the battery cycle stability and storage stability.

[0014] In any embodiment, R3 comprises R6 is the same as R1, and R5 is the same as R2.

[0015] In any embodiment, R3 comprises R4 comprises at least one of a carbonyl group, a carbonyl group or a phenyl-substituted C1-C6 hydrocarbon group.

[0016] When the electrolyte additive has a symmetrical structure, it has better thermal stability and can significantly improve the high-temperature performance of the battery.

[0017] In any embodiment, the chemical bond between N and R3 is a double bond, and R3 comprises a carbonyl group or a sulfinyl group.

[0018] N and R3 are connected by a double bond. The electrolyte additive has higher reactivity and is more likely to form an interface coating on the negative electrode material, which can effectively improve the cycle performance and storage performance of the battery.

[0019] In any embodiment, R3 comprises a halogen-substituted or unsubstituted C1-C4 cycloalkyl group.

[0020] In any embodiment, R2, R3 and the nitrogen to which they are attached together form a cyclic structure.

[0021] When the electrolyte additive contains a ring structure, the electrolyte additive has higher reactivity and is easy to form an interface film on the negative electrode active material, thereby improving the cycle stability of the battery.

[0022] In any embodiment, R3 comprises R4 comprises a substituted or unsubstituted C1-C6 cyclic hydrocarbon group. In any embodiment, R3 comprises R4 and the nitrogen atoms connected to both sides thereof form a ring structure together with R2 and R5.

[0023] In any embodiment, the electrolyte additive comprises at least two compounds of Formula I, one of which has the following structure:

[0024] In any embodiment, the compound represented by Formula I is selected from at least one of the compounds represented by Formula I-1 to Formula I-14,

[0025] A second aspect of the present application provides an electrolyte comprising the electrolyte additive of the first aspect.

[0026] In any embodiment, based on the total mass of the electrolyte, the mass content of the compound represented by formula I is less than or equal to 5%, and can be optionally 0.3% to 4%.

[0027] When the mass content of the compound represented by formula I is 0.3% to 4%, it is beneficial to form an interface film of appropriate thickness on the surface of the negative electrode material, reduce the internal resistance of the battery, and improve the cycle stability and storage stability of the battery.

[0028] In any embodiment, the electrolyte further comprises sultone and / or anhydride. Optionally, the sultone comprises one or more of 1,3-propane sultone, 1,4-butane sultone, 1,3-propylene sultone, and methylene disulfonate; optionally, the anhydride comprises one or more of succinic anhydride, maleic anhydride, and citraconic anhydride.

[0029] Sultones help reduce the activity of transition metal ions in the positive electrode, inhibiting their catalytic reactions in the electrolyte. Acid anhydrides can effectively reduce the water and acid content in the electrolyte, slowing the decomposition of cyclic carbonate compounds. The synergistic effect of sultones and / or acid anhydrides with the compound of Formula I can more effectively inhibit gas production, reduce battery internal resistance, and further optimize the battery's cycling and storage performance.

[0030] In any embodiment, based on the total mass of the electrolyte, the mass content of the sultone is less than or equal to 2%, optionally 0.1% to 1%, and / or the mass content of the anhydride is less than or equal to 3%, optionally 0.3% to 3%.

[0031] When the mass content of the sultone and / or the mass content of the anhydride additive is within a suitable range based on the total mass of the electrolyte, it is beneficial to form an effective combination with the electrolyte additive shown in Formula I, forming a stable interface protective film on the electrode surface, reducing gas production, and improving the cycle performance and service life of the battery.

[0032] In any embodiment, the electrolyte comprises a cyclic carbonate and a chain ester, optionally, the cyclic carbonate comprises one or more of fluoroethylene carbonate, difluoroethylene carbonate, ethylene carbonate, and propylene carbonate, and the chain ester comprises one or more of diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, methyl formate, ethyl formate, ethyl acetate, propyl formate, and propyl acetate.

[0033] In any embodiment, based on the total mass of the electrolyte, the mass content of the cyclic carbonate is 5% to 50%, and optionally 10% to 20%.

[0034] In any embodiment, based on the total mass of the electrolyte, the mass content of the chain ester is 50% to 90%, and optionally 70% to 80%.

[0035] When the mass content of the cyclic carbonate and the chain ester is within a suitable range based on the total mass of the electrolyte, it is beneficial to improve the conductivity of the electrolyte and the kinetic performance of the battery.

[0036] In any embodiment, based on the total mass of the electrolyte, the total mass content of the compound represented by formula I, the sultone and the acid anhydride is 0.5% to 10%, optionally 1% to 3%.

[0037] When the total mass content of the compound represented by Formula I, sultone and anhydride is 0.5% to 10% based on the total mass of the electrolyte, the water and acid content in the electrolyte can be effectively reduced, the battery impedance can be reduced, a stable interface structure can be generated, and the battery life can be improved.

[0038] A third aspect of the present application provides a secondary battery, comprising the electrolyte additive of the first aspect or the electrolyte of the second aspect.

[0039] In any embodiment, the secondary battery includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material is a silicon-based material; optionally, based on the total mass of the negative electrode active material, the mass content of the silicon-based material is greater than or equal to 20%, and can be optionally 30%-50%.

[0040] Silicon-based materials have high capacity and can significantly increase the energy density of batteries. However, they exhibit significant volume effects during cycling and suffer from poor cycling stability. The electrolyte additive or electrolyte provided herein can effectively improve the poor stability of silicon-based materials, particularly at high temperatures.

[0041] A fourth aspect of the present application provides an electrical device comprising the electrolyte additive of the first aspect, the electrolyte of the second aspect, or the secondary battery of the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0043] FIG2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG1 ;

[0044] FIG3 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0045] Reference numerals: 1 secondary battery; 11 housing; 12 electrode assembly; 13 cover plate. DETAILED DESCRIPTION

[0046] Below, the embodiments of the binder, preparation method, electrode, battery, and electrical device 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 understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0047] " range " 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 the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, 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 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, 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.

[0048] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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).

[0053] The electrolyte in the prior art mainly uses lithium hexafluorophosphate as lithium salt. During the circulation and storage process, lithium hexafluorophosphate easily produces water and hydrogen fluoride. Water easily reacts violently with metal materials, causing battery safety problems; while hydrogen fluoride catalyzes the decomposition of the electrolyte, destroying the interface structure between the electrolyte and the active material, and also causes the dissolution of transition metal ions in the positive electrode active material, destroying the lattice structure and deteriorating the performance of the battery cell. In the prior art, additives are often added to the electrolyte to form an interface coating layer at the interface of the electrolyte active material by an in-situ coating method to improve the interface stability. However, the interface coating layer formed in the current prior art generates a single interface component, which cannot effectively protect the electrode active material during long-term charge and discharge cycles, and the effect on improving the battery cell performance is not ideal; and it produces serious gas at high temperatures, making it difficult to effectively improve the high-temperature performance of the battery.

[0054] Based on this, the present application proposes an electrolyte additive, which can improve the cycle performance and storage performance of secondary batteries, especially improve the performance of batteries at high temperatures.

[0055] In some embodiments, the electrolyte additive comprises a compound of Formula I,

[0056] in, It means that N and R2, N and R3 are all connected by single bonds, or N and R3 are connected by double bonds, and there is no bond between N and R2; R1 contains at least one of F, Cl, halogen-substituted or unsubstituted C1-C4 hydrocarbon groups; R2 contains at least one of H, halogen, substituted or unsubstituted C1-C4 hydrocarbon groups, silanyl, phenyl, carbonyl, sulfinyl or cyano groups, wherein the substituent group of the C1-C4 hydrocarbon group contains at least one of F and Cl; R3 contains H, halogen, halogen-substituted or unsubstituted C1-C4 hydrocarbon groups, silanyl, phenyl, carbonyl, sulfinyl, cyano or At least one of, wherein R4 comprises at least one of a carbonyl group, a substituted or unsubstituted C1-C6 hydrocarbon group, the substituent of the C1-C6 hydrocarbon group comprises at least one of F, Cl, a silyl group, a phenyl group, a carbonyl group, a sulfinyl group, and a cyano group, R5 comprises at least one of H, F, a substituted or unsubstituted C1-C4 hydrocarbon group, the substituent of the C1-C4 hydrocarbon group comprises at least one of F, Cl, a silyl group, a phenyl group, a carbonyl group, a sulfinyl group, and a cyano group, and R6 comprises at least one of F, Cl, a halogen-substituted or unsubstituted C1-C4 hydrocarbon group.

[0057] As used herein, the term "C1-C4 hydrocarbon group" refers to a hydrocarbon group having 1 to 4 carbon atoms, which may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, and optionally includes a double bond or a triple bond. Non-limiting examples of C1-C4 hydrocarbon groups may include methyl (CH3-), ethyl (C2H5-), isopropyl ((CH3)2CH-), vinyl (CH2=CH-), and propynyl (HC≡CCH2-).

[0058] As used herein, the term "silyl" refers to a -Si(X1)(X2)(X3) group, where X1, X2, and X3 each independently comprise hydrogen, a substituted or unsubstituted C1-C3 alkyl group. Examples of silyl groups include, but are not limited to, -SiH3 and -Si(CH3)3.

[0059] As used herein, the term "phenyl" refers to

[0060] As used herein, the term "carbonyl" refers to

[0061] As used herein, the term "sulfinyl" refers to

[0062] As used herein, the term "cyano" refers to

[0063] As used herein, the term "cyclic structure" refers to a structure in which atoms in a molecule are arranged in a ring. The number of rings in the cyclic structure is not limited, and for example, it can be a 4-membered ring, a 5-membered ring, a 6-membered ring, or a 7-membered ring.

[0064] Herein, the term "C1-C6 hydrocarbon group" may be understood with reference to the definition of the term "C1-C4 hydrocarbon group".

[0065] As used herein, the term "cycloalkyl" refers to a hydrocarbon group having a cyclic structure. The cycloalkyl group may optionally include unsaturated bonds, such as double bonds and triple bonds. The number of rings in the cycloalkyl group is not limited, and includes, but is not limited to, a three-membered ring, a four-membered ring, a five-membered ring, a six-membered ring, a seven-membered ring, and the like. Non-limiting examples of cycloalkyl groups include cyclopropyl, cyclobutyl, and cyclopentenyl.

[0066] In some embodiments, R1 comprises F. In some embodiments, R1 comprises Cl. In some embodiments, R1 comprises a halogen-substituted C1-C4 hydrocarbon group. In some embodiments, R1 comprises an unsubstituted C1-C4 hydrocarbon group.

[0067] In some embodiments, R2 comprises H. In some embodiments, R2 comprises halogen. In some embodiments, R2 comprises a substituted or unsubstituted C1-C4 hydrocarbon group. In some embodiments, R2 comprises a silane group. In some embodiments, R2 comprises a phenyl group. In some embodiments, R2 comprises a carbonyl group. In some embodiments, R2 comprises a sulfinyl group. In some embodiments, R2 comprises a cyano group.

[0068] In some embodiments, R3 comprises H. In some embodiments, R3 comprises a halogen. In some embodiments, R3 comprises a halogen-substituted or unsubstituted C1-C4 hydrocarbon group. In some embodiments, R3 comprises a silane group. In some embodiments, R3 comprises a phenyl group. In some embodiments, R3 comprises a carbonyl group. In some embodiments, R3 comprises a sulfinyl group. In some embodiments, R3 comprises a cyano group. In some embodiments, R2, R3, and the nitrogen to which they are attached together form a cyclic structure.

[0069] In some embodiments, R3 comprises The structure of Formula I is shown below In some embodiments, R4 and the nitrogen atoms connected to both sides thereof form a ring structure together with R2 and R5.

[0070] In some embodiments, R4 comprises a carbonyl group. In some embodiments, R4 comprises a substituted C1-C6 hydrocarbon group, and the substituent group may include at least one of F, Cl, a silanyl group, a phenyl group, a carbonyl group, a sulfinyl group, and a cyano group. In some embodiments, R4 comprises an unsubstituted C1-C6 hydrocarbon group. In some embodiments, R5 comprises H. In some embodiments, R5 comprises a halogen. In some embodiments, R5 comprises a substituted or unsubstituted C1-C4 hydrocarbon group, and the substituent group may include at least one of F, Cl, a silanyl group, a phenyl group, a carbonyl group, a sulfinyl group, and a cyano group. In some embodiments, R6 comprises at least one of F, Cl, a halogen-substituted or unsubstituted C1-C4 hydrocarbon group.

[0071] The electrolyte additive provided by the present application can reduce the content of water and hydrofluoric acid in the electrolyte by reacting with byproducts such as water or hydrofluoric acid, thereby reducing the deterioration of battery performance caused by byproducts; at the same time, it participates in electrochemical reactions at the interface between the negative electrode active material and the electrolyte to generate inorganic products containing S and N, thereby improving the thermal stability and chemical stability of the interface. The electron-rich N and the strongly electron-withdrawing O=S=O in the electrolyte additive have high binding stability and are not prone to thermal decomposition reactions, thereby optimizing the cycle stability and storage stability of the battery, especially at high temperatures. The structure will not react with the current collector metal to generate byproducts soluble in the electrolyte, causing current collector corrosion, thereby further improving the cycle stability of the battery.

[0072] In some embodiments, R1 comprises F or -CF3.

[0073] When halogen is included in the electrolyte additive, the reaction activity is further improved and the cycle performance of the battery is further optimized.

[0074] In some embodiments, the chemical bond between N and R3 is a single bond, and Formula I is R3 contains H, halogen, halogen-substituted C1-C4 hydrocarbon group, cycloalkyl group, phenyl, carbonyl, sulfinyl, cyano or At least one of .

[0075] In some embodiments, R3 comprises R6 is the same as R1, and R5 is the same as R2.

[0076] When the electrolyte additive has a symmetrical structure, it has better thermal stability and can significantly improve the high-temperature performance of the battery.

[0077] In some embodiments, R3 comprises R4 comprises at least one of a carbonyl group, a carbonyl group or a phenyl-substituted C1-C6 hydrocarbon group. In some embodiments, the chemical bond between N and R3 is a double bond, R3 comprises a carbonyl group or a sulfinyl group, and Formula I is

[0078] N and R3 are connected by a double bond, and the electrolyte additive has higher reactivity, which can effectively improve the cycle performance and storage performance of the battery.

[0079] In some embodiments, R3 comprises a halogen-substituted or unsubstituted C1-C4 cycloalkyl group.

[0080] When the electrolyte additive contains a ring structure, the electrolyte additive has higher reactivity and is easy to form an interface film on the negative electrode active material, thereby improving the cycle stability of the battery.

[0081] In some embodiments, R2, R3 and the nitrogen to which they are attached together form a cyclic structure.

[0082] In some embodiments, the chemical bond between N and R3 is a single bond, and R3 comprises

[0083] When each mole of the electrolyte additive contains at least two moles of -N-SO2- groups, it can more efficiently reduce the internal resistance of the battery and improve the battery cycle stability and storage stability.

[0084] In some embodiments, R3 comprises R4 includes a substituted or unsubstituted C1-C6 cyclic hydrocarbon group.

[0085] In some embodiments, R3 comprises R4 and the nitrogen atoms connected to both sides thereof form a ring structure together with R2 and R5.

[0086] In some embodiments, the electrolyte additive comprises at least two compounds of Formula I, one of which has the following structure:

[0087] The combination of two electrolyte additives represented by Formula I with different structures can more effectively improve the cycle performance and storage performance of the battery compared to a single component.

[0088] In some embodiments, the electrolyte additive comprises at least two compounds of Formula I, one of which has the structure shown in A-1 and the other has the structure shown in A-2.

[0089] R1 and R1' each independently contain at least one of F, Cl, and a halogen-substituted or unsubstituted C1-C4 hydrocarbon group; R2 and R2' each independently contain at least one of H, a halogen, a substituted or unsubstituted C1-C4 hydrocarbon group, a silanyl group, a phenyl group, a carbonyl group, a sulfinyl group, or a cyano group; R3 contains at least one of H, a halogen, a halogen-substituted or unsubstituted C1-C4 hydrocarbon group, a silanyl group, a phenyl group, a carbonyl group, a sulfinyl group, or a cyano group; optionally, R2, R3, and the nitrogen to which they are connected together form a cyclic structure; R4 Contains at least one of a carbonyl group, a substituted or unsubstituted C1-C6 hydrocarbon group, and the substituent group may include F, Cl, a silyl group, a phenyl group, a carbonyl group, a sulfinyl group, and a cyano group; R5 contains at least one of H, a halogen, a substituted or unsubstituted C1-C4 hydrocarbon group, and the substituent group may include at least one of a silyl group, a phenyl group, a carbonyl group, a sulfinyl group, and a cyano group; R6 contains at least one of a F, Cl, a halogen-substituted or unsubstituted C1-C4 hydrocarbon group; optionally, R4 and the N groups connected to both sides thereof form a cyclic structure together with R2' and R5.

[0090] In some embodiments, the compound represented by Formula I is selected from at least one of the compounds represented by Formula I-1 to Formula I-14.

[0091] [Electrolyte]

[0092] In one embodiment of the present application, an electrolyte is provided, comprising the electrolyte additive according to any embodiment.

[0093] In some embodiments, based on the total mass of the electrolyte, the mass content of the compound represented by Formula I is less than or equal to 5%, and can be optionally 0.3% to 4%.

[0094] In some embodiments, based on the total mass of the electrolyte, the mass content of the compound represented by Formula I may be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3% or more. %, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.8%, 4.9% or 5%.

[0095] When the mass content of the compound represented by Formula I is less than or equal to 5%, it is beneficial to form an interface film of appropriate thickness on the surface of the negative electrode material, reduce the internal resistance of the battery, and improve the cycle stability and storage stability of the battery.

[0096] In some embodiments, the electrolyte further comprises sultone and / or anhydride. Optionally, the sultone comprises one or more of 1,3-propane sultone, 1,4-butane sultone, 1,3-propylene sultone, and methylene disulfonate; optionally, the anhydride comprises one or more of succinic anhydride, maleic anhydride, and citraconic anhydride.

[0097] Sultones help reduce the activity of transition metal ions in the positive electrode, inhibiting their catalytic reactions in the electrolyte. Acid anhydrides can effectively reduce the water and acid content in the electrolyte, slowing the decomposition of cyclic carbonate compounds. The synergistic effect of sultones and / or acid anhydrides with the compound of Formula I can more effectively inhibit gas production, reduce battery internal resistance, and further optimize the battery's cycling and storage performance.

[0098] In some embodiments, based on the total mass of the electrolyte, the mass content of sultone is less than or equal to 2%, and can be optionally 0.1% to 1%; and / or the mass content of anhydride is less than or equal to 3%, and can be optionally 0.3% to 3%.

[0099] In some embodiments, the mass content of sultone, based on the total mass of the electrolyte, may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0%.

[0100] In some embodiments, the mass content of the anhydride is 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or 3% based on the total mass of the electrolyte.

[0101] When the mass content of sultone and / or the mass content of anhydride is within a suitable range based on the total mass of the electrolyte, it is beneficial to form an effective combination with the electrolyte additive represented by Formula I, forming a stable interfacial protective film on the electrode surface, reducing gas production, and improving the cycle performance and service life of the battery.

[0102] In some embodiments, the electrolyte comprises a cyclic ester and a chain ester. Optionally, the cyclic ester comprises one or more of fluoroethylene carbonate, difluoroethylene carbonate, ethylene carbonate, and propylene carbonate. Alternatively, the chain ester comprises one or more of diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, methyl formate, ethyl formate, ethyl acetate, propyl formate, and propyl acetate.

[0103] In some embodiments, the electrolyte contains a fluorinated cyclic carbonate, which may be fluoroethylene carbonate or bisfluoroethylene carbonate.

[0104] The SEI film formed by fluorinated cyclic carbonates represented by fluoroethylene carbonate on the negative electrode material is thin, tough and self-healing, which can suppress the problem of structural breakage of silicon-based materials due to volume expansion under charging and discharging conditions, and improve the service life of silicon-based materials. Therefore, it is a commonly used electrolyte component in silicon-based secondary batteries. However, fluorinated cyclic carbonate additives are easily decomposed at high temperatures to produce hydrogen fluoride, which destroys the interface structure between the electrolyte and the negative electrode active material, while causing the dissolution of the transition metal of the positive electrode active material, destroying the lattice structure and affecting the performance of the battery cell. The combination of the electrolyte additive and the fluorinated cyclic carbonate provided in the present application can effectively suppress the high-temperature gas production phenomenon of the fluorinated cyclic ester, while improving the capacity and energy density of the secondary battery, significantly improving the cycle stability and storage stability of the battery.

[0105] In some embodiments, the mass content of the fluorinated cyclic carbonate is 8%-15% based on the total mass of the electrolyte.

[0106] In some embodiments, the mass content of the cyclic carbonate is 5% to 50%, optionally 10% to 20%, based on the total mass of the electrolyte.

[0107] In some embodiments, the mass content of the cyclic carbonate may be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50% based on the total mass of the electrolyte.

[0108] In some embodiments, based on the total mass of the electrolyte, the mass content of the chain ester is 50% to 90%, and optionally 70% to 80%.

[0109] In some embodiments, the mass content of the chain ester may be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90% based on the total mass of the electrolyte.

[0110] When the mass content of the cyclic carbonate and the chain ester is within a suitable range based on the total mass of the electrolyte, it is beneficial to improve the conductivity of the electrolyte and the kinetic performance of the battery.

[0111] In some embodiments, based on the total mass of the electrolyte, the total mass content of the compound represented by Formula I, the sultone additive, and the acid anhydride additive is 0.5% to 10%, optionally 1% to 3%.

[0112] In some embodiments, based on the total mass of the electrolyte, the total mass content of the compound represented by Formula I, sultone and anhydride can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0113] When the total mass content of the compound represented by Formula I, sultone and anhydride is 0.5% to 10% based on the total mass of the electrolyte, the water and acid content in the electrolyte can be effectively reduced, the battery impedance can be reduced, a stable interface structure can be generated, and the battery life can be improved.

[0114] In some embodiments, the electrolyte comprises a lithium salt comprising LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2), LiPF6, LiBF4, lithium dioxalatoborate, lithium difluorooxalatoborate, LiAsF6, Li(FSO2)2N, LiCF3SO3, LiClO4, one or more, wherein x and y are natural numbers.

[0115] [Positive electrode]

[0116] 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, wherein the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

[0117] 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.

[0118] 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.).

[0119] In some embodiments, the positive electrode active material may adopt the positive electrode active material for 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-containing phosphates with an 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 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 NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) 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.

[0120] In some embodiments, the positive electrode active material is a nickel-rich material, and the molar ratio of nickel in the transition metal of the positive electrode active material is higher than 85%.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] [Negative electrode]

[0125] 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.

[0126] 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.

[0127] 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.).

[0128] In some embodiments, the negative electrode active material may adopt the negative electrode active material for batteries known in the art. As an example, the negative electrode active material may include at least one of the following materials: lithium metal and its alloys, artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate, etc. The silicon-based material may contain at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites and silicon alloys. The tin-based material may contain at least one of elemental tin, tin oxide compounds 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 can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0129] In some embodiments, the negative electrode film layer may further optionally 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).

[0130] In some embodiments, the negative electrode film layer may further optionally 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.

[0131] In some embodiments, the negative electrode film layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0132] 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.

[0133] [Isolation film]

[0134] In some embodiments, the secondary battery 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.

[0135] 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.

[0136] [Secondary battery]

[0137] In some embodiments, the secondary battery includes a negative electrode active material, which is a silicon-based material; optionally, based on the total mass of the negative electrode active material, the mass content of the silicon-based material is greater than or equal to 20%, and more optionally 30%-50%.

[0138] Silicon-based materials have high capacity and can significantly increase the energy density of batteries. However, they exhibit significant volume effects during cycling and suffer from poor cycling stability. The electrolyte additive or electrolyte provided herein can effectively improve the poor stability of silicon-based materials, particularly at high temperatures.

[0139] The electrolyte additive comprising the compound represented by Formula I of the present application is suitable for high energy density batteries, so that the batteries have both high cycle performance and storage stability.

[0140] In one embodiment of the present application, an electrical device is provided, comprising at least one of the electrolyte additive according to any embodiment, the electrolyte according to any embodiment, or the secondary battery according to any embodiment.

[0141] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0142] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG1 shows a secondary battery 1 having a square structure as an example.

[0143] In some embodiments, referring to Figure 2, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 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 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the secondary battery 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0144] In addition, the present application also provides an electrical device, which includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can include, but is not limited to, 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.

[0145] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0146] FIG3 shows an example of an electric device, which may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0147] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0148] Example

[0149] 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.

[0150] 1. Preparation method

[0151] Example 1

[0152] (1) Preparation of positive electrode sheet

[0153] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) in a weight ratio of 90:5:5, and are fully stirred and mixed to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode collector, and then dried, cold pressed, and cut to obtain a positive electrode sheet.

[0154] (2) Preparation of negative electrode sheet

[0155] The negative electrode active material silicon dioxide material and artificial graphite (the mass ratio of the two is 3:7), the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in the solvent deionized water in a weight ratio of 90:4:4:2, and are evenly mixed to prepare a negative electrode slurry; then the negative electrode slurry is evenly coated on the negative electrode collector copper foil once or multiple times, and the negative electrode film is obtained after drying, and then the negative electrode sheet is obtained by cold pressing and slitting.

[0156] (3) Preparation of electrolyte

[0157] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), the organic solvents fluoroethylene carbonate (FEC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) were mixed uniformly in a mass ratio of 1:2:7. 12.5wt% of LiPF6 lithium salt was added and dissolved in the organic solvent. Subsequently, 2.0wt% of the compound represented by Formula I-1, 0.5wt% of 1,3-propane sultone, and 0.5wt% of succinic anhydride were added to the organic solvent as additives and mixed uniformly to obtain the electrolyte of Example 1.

[0158] (4) Isolation membrane

[0159] Polypropylene film is used as the isolation film.

[0160] (5) Preparation of batteries

[0161] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in a battery casing, dried, and then injected with electrolyte, and then undergoes formation, static and other processes to produce a lithium-ion battery.

[0162] See Table 1 for specific parameters.

[0163] Example 2-18

[0164] The preparation methods of Examples 2-18 are basically the same as those of Example 1, except that the composition of the electrolyte of the secondary battery is adjusted. Specific parameters are shown in Table 1.

[0165] The electrolyte in Example 19 does not contain FEC, and the mixing ratio of EC to EMC is 3:7.

[0166] Comparative Examples 1-3 do not contain the compound represented by Formula I, and the preparation method is basically the same as that of Example 1. The specific parameters are shown in Table 1.

[0167] The preparation method of the electrolyte of Comparative Example 1 is as follows:

[0168] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), the organic solvent EC / EMC was mixed uniformly in a mass ratio of 3 / 7, 12.5wt% LiPF6 lithium salt was added and dissolved in the organic solvent, and stirred uniformly to obtain the electrolyte of Comparative Example 1.

[0169] 2. Battery performance test

[0170] 1. Capacity retention after 800 cycles at 45°C

[0171] At 45°C, the lithium-ion batteries prepared in each example and comparative example were charged at a constant current of 1C to 4.3V, then charged at a constant voltage of 4.3V until the current was less than 0.05C. The lithium-ion batteries were then discharged at a constant current of 1C to 3.0V. This constituted one charge-discharge cycle, and the discharge capacity at this point was recorded as the discharge capacity of the battery's first cycle. This charging and discharging cycle was repeated, and the discharge capacity after the 800th cycle was recorded.

[0172] Capacity retention rate (%) of a lithium-ion battery after 800 cycles at 45° C. = (discharge capacity at the 800th cycle / discharge capacity at the first cycle)×100%.

[0173] 2. Battery internal resistance

[0174] At 25°C, the lithium-ion batteries prepared in each embodiment and comparative example and the lithium-ion battery after 800 cycles at 45°C were charged to 4.3V at a constant current of 1C. They were then charged at a constant voltage of 4.3V until the current was less than 0.05C, and then discharged at 1C for 30 minutes, adjusting the battery's capacity to 50% SOC. The positive and negative test leads of a TH2523A AC internal resistance tester were then placed in contact with the positive and negative electrodes of the battery, respectively. The internal resistance of the battery was read using the internal resistance tester and recorded as the initial battery internal resistance (mΩ) and the battery internal resistance (mΩ) after 800 cycles, respectively.

[0175] 3. Volume expansion rate after storage at 60°C for 50 days

[0176] At 25°C, the lithium-ion battery prepared in each embodiment and comparative example was charged at a constant current of 1C to a voltage of 4.3V, and then charged at a constant voltage of 4.3V to a current of 0.05C. At this time, the volume of the lithium-ion battery was tested and recorded as V1; then the fully charged lithium-ion battery was placed in a constant temperature box at 60°C and stored for 50 days. The volume was tested by the water displacement method and recorded as V2.

[0177] The volume expansion ratio (%) of a lithium-ion battery after storage at 60°C for 50 days = (V2-V1) / V1×100%.

[0178] 3. Test Results

[0179] The test results of the above embodiments and comparative examples are shown in Table 1.

[0180] Table 1

[0181] As can be seen from Table 1, the electrolytes of the batteries of Examples 1-19 include an electrolyte additive comprising the compound represented by Formula I. Compared with the electrolytes of Comparative Examples 1-3 that do not include the compound represented by Formula I, the batteries of Examples 1-19 exhibit lower internal resistance, higher cycle capacity retention rate, and lower volume expansion rate.

[0182] From the comparison of Examples 1-16 and Comparative Examples 1-3, it can be seen that when one or more of the compounds of Formula I-1 to Formula I-14 of the present application are used as electrolyte additives, they can effectively reduce the internal resistance of the battery, improve the cycle capacity retention rate of the battery, and reduce the volume expansion rate of the battery.

[0183] From the comparison of Examples 1-14 and Examples 15-16, it can be seen that the simultaneous addition of multiple different compounds of Formula I can exert a synergistic effect. Under the same addition amount, the internal resistance of the battery is more significantly reduced, the cycle capacity retention rate is improved, and the volume expansion rate is reduced. Compared with Comparative Example 3, when the compound of Formula I-2 and Formula I-12 in Example 15 and the compound of Formula I-3 and Formula I-13 in Example 16 are added to the electrolyte, the initial internal resistance of the battery and the internal resistance after 800 cycles are significantly reduced, the capacity retention rate after 800 cycles is increased by more than 3 times, and the volume expansion rate after 50 days of storage is reduced by nearly 2 times.

[0184] Comparison of Example 12 with Examples 17-18 shows that the addition of 1,3-propane sultone or succinic anhydride in the electrolyte can synergistically act with the compound represented by Formula I to further improve the cycle capacity retention rate of the battery and reduce the volume expansion rate of the battery.

[0185] From the comparison between Example 2 and Example 19, it can be seen that the addition of fluoroethylene carbonate (FEC) to the electrolyte can synergize with the compound of Formula I, sultone and anhydride, thereby further improving the cycle capacity retention rate of the battery and further reducing the volume expansion rate without increasing the internal resistance of the battery.

[0186] 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 additive, characterized in that: It comprises a compound shown in formula I, in, It means that N and R2, N and R3 are all connected by single bonds, or N and R3 are connected by double bonds, and there is no bond between N and R2; R1 comprises at least one of F, Cl, halogen-substituted or unsubstituted C1-C4 hydrocarbon groups; R2 comprises at least one of H, halogen, substituted or unsubstituted C1-C4 hydrocarbon group, silane group, phenyl group, carbonyl group, sulfinyl group or cyano group, wherein the substituent group of the C1-C4 hydrocarbon group comprises at least one of F and Cl; R3 includes H, halogen, halogen-substituted or unsubstituted C1-C4 hydrocarbon group, silane group, phenyl group, carbonyl group, sulfinyl group, cyano group or At least one of Wherein, R4 comprises at least one of a carbonyl group, a substituted or unsubstituted C1-C6 hydrocarbon group, and the substituent group of the C1-C6 hydrocarbon group comprises at least one of F, Cl, a silane group, a phenyl group, a carbonyl group, a sulfinyl group, and a cyano group, R5 comprises at least one of H, F, substituted or unsubstituted C1-C4 hydrocarbon groups, and the substituent of the C1-C4 hydrocarbon group comprises at least one of F, Cl, silane, phenyl, carbonyl, sulfinyl, and cyano, R6 comprises at least one of F, Cl, and a halogen-substituted or unsubstituted C1-C4 hydrocarbon group.

2. The electrolyte additive according to claim 1, characterized in that: R1 contains F or -CF3.

3. The electrolyte additive according to claim 1 or 2, characterized in that: The chemical bond between N and R3 is a single bond, and R3 includes H, halogen, halogen-substituted C1-C4 hydrocarbon group, cycloalkyl group, phenyl, carbonyl, sulfinyl, cyano or At least one of .

4. The electrolyte additive according to any one of claims 1 to 3, characterized in that R3 contains R6 is the same as R1, and R5 is the same as R2.

5. The electrolyte additive according to any one of claims 1 to 4, characterized in that R3 contains R4 comprises at least one of a carbonyl group, a carbonyl group or a phenyl-substituted C1-C6 hydrocarbon group.

6. The electrolyte additive according to any one of claims 1 to 5, characterized in that The chemical bond between N and R3 is a double bond, and R3 includes a carbonyl group or a sulfinyl group.

7. The electrolyte additive according to any one of claims 1 to 6, characterized in that: R3 includes a halogen-substituted or unsubstituted C1-C4 cyclic hydrocarbon group.

8. The electrolyte additive according to any one of claims 1 to 7, characterized in that: R2, R3 and the nitrogen to which they are connected together form a ring structure.

9. The electrolyte additive according to any one of claims 1 to 8, characterized in that: R3 contains R4 includes a substituted or unsubstituted C1-C6 cyclic hydrocarbon group.

10. The electrolyte additive according to any one of claims 1 to 9, characterized in that: R3 contains R4 and the N connected to both sides thereof form a ring structure together with R2 and R5.

11. The electrolyte additive according to any one of claims 1 to 10, characterized in that: The electrolyte additive comprises at least two compounds of Formula I, one of which has the following structure:

12. The electrolyte additive according to any one of claims 1 to 11, characterized in that: The compound represented by Formula I is selected from at least one of the compounds represented by Formula I-1 to Formula I-14, 13. An electrolyte, characterized in that: An electrolyte additive comprising the electrolyte additive according to any one of claims 1 to 12.

14. The electrolyte according to claim 13, characterized in that Based on the total mass of the electrolyte, the mass content of the compound represented by formula I is less than or equal to 5%, and can be optionally 0.3% to 4%.

15. The electrolyte according to claim 13 or 14, characterized in that: The electrolyte further comprises sultone and / or anhydride; Optionally, the sultone comprises one or more of 1,3-propane sultone, 1,4-butane sultone, 1,3-propylene sultone, and methylene disulfonate; Optionally, the acid anhydride comprises one or more of succinic anhydride, maleic anhydride, and citraconic anhydride.

16. The electrolyte according to any one of claims 13 to 15, characterized in that Based on the total mass of the electrolyte, the mass content of the sultone is less than or equal to 2%, and can be optionally 0.1% to 1%; and / or the mass content of the anhydride is less than or equal to 3%, and can be optionally 0.3% to 3%.

17. The electrolyte according to claim 15 or 16, characterized in that: Based on the total mass of the electrolyte, the total mass content of the compound represented by formula I, the sultone and the acid anhydride is 0.5% to 10%, and can be optionally 1% to 3%.

18. A secondary battery, characterized in that: The electrolyte additive according to any one of claims 1 to 12 or the electrolyte according to any one of claims 13 to 17.

19. The secondary battery according to claim 18, characterized in that: The secondary battery includes a negative electrode plate, the negative electrode plate includes a negative electrode collector and a negative electrode film layer arranged on at least one side of the negative electrode collector, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material; optionally, based on the total mass of the negative electrode active material, the mass content of the silicon-based material is greater than or equal to 20%, and can be optionally 30%-50%.

20. An electrical device, characterized in that: Includes the secondary battery according to claim 18 or 19.

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