Electrolyte additive for secondary battery and use thereof

Abstract

An electrolyte additive and a use thereof. The electrolyte additive comprises a compound having the structure shown in formula 1, where X and Y are each independently selected from (II) or (III), and R1 and R2 are each independently selected from a single bond, substituted or unsubstituted -CH2-, and substituted or unsubstituted -CH2-CH2-.

Description

A secondary battery electrolyte additive and its application

[0001] Cross-references to related applications

[0002] This application is based on and claims priority to Chinese Patent Application No. 202411050807.6, filed on August 1, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of secondary battery technology, specifically to an electrolyte additive and its application. Background Technology

[0004] With the development of science and technology and the improvement of human quality of life, green environmental protection is receiving more and more attention. The application range of rechargeable batteries is becoming wider and wider. For example, lithium-ion batteries have seen significant acceleration in research progress due to their high energy density and power density, good safety characteristics, excellent cycle performance and wide range of temperature applications. Higher energy density, excellent cycle performance and good safety are widely used in 3C products, electric vehicles and hybrid vehicles and other equipment.

[0005] Secondary batteries consist of a positive electrode, a negative electrode, a separator, and an electrolyte, each component significantly affecting performance. The solid electrolyte interphase (SEI) film on the electrode surface has been extensively studied and discussed. The performance of the SEI layer between the electrode material and the electrolyte depends on its ionic conductivity, ion transfer number, and stability to the electrolyte, among other factors. However, the inventors have discovered that existing electrodes still suffer from problems such as low conductivity of the surface passivation film (i.e., the aforementioned SEI), easy decomposition, and insufficient high-temperature cycling performance. Suitable electrolyte additives can help solve these problems.

[0006] Therefore, how to develop a secondary battery electrolyte additive that combines film-forming properties with good conductivity, stability, and cycle performance is an urgent problem to be solved. Summary of the Invention

[0007] In view of this, one object of this disclosure is to provide an electrolyte additive that contains a compound having the structure shown in Formula 1—a cyclic structure with sulfate, sulfite, or carbonate groups at both ends linked together by a cyclic structure containing a ketone carbonyl group in the middle, wherein the ketone carbonyl group can coordinate with metal ions (e.g., lithium ions) in the electrolyte salt, which facilitates the additive moving to the electrode surface with the current and undergoing an electrochemical reaction on the electrode surface; on the one hand, the ester-containing ring can open and react with the electrolyte salt (e.g., lithium salt) in the electrolyte to form an organic electrolyte salt (e.g., an organic lithium salt); on the other hand, the cyclic ketone structure opens and reacts with organic matter in the battery or self-polymerizes and cross-links to form a dual electrolyte salt (e.g., lithium salt) organic film with good stability, high structural strength, and good ion permeability, thereby improving the high-temperature storage and high-temperature cycling performance of the battery.

[0008] Another object of this disclosure is to provide an electrolyte.

[0009] Another object of this disclosure is to provide a secondary battery.

[0010] In a first aspect, embodiments of this disclosure provide an electrolyte additive comprising a compound having the structure shown in Formula 1:

[0011] Where X and Y are each independently selected R1 and R2 are each independently selected from single bonds, substituted or unsubstituted -CH2-, or substituted or unsubstituted -CH2-CH2-.

[0012] In some embodiments, the substituents in the substituted or unsubstituted -CH2- and substituted or unsubstituted -CH2-CH2- are halogens.

[0013] In some embodiments, the compound with the structure shown in Formula 1 includes at least one of compound 1 to compound 10:

[0014] Secondly, embodiments of this disclosure provide an electrolyte comprising a non-aqueous organic solvent, an electrolyte salt, and an electrolyte additive as described in any of the embodiments of the first aspect of this disclosure.

[0015] In some embodiments, the compound with the structure shown in Formula 1 has a mass content of 0.05-10% in the electrolyte, optionally 0.1-5%.

[0016] In some embodiments, the non-aqueous organic solvent includes at least one of ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents, and sulfone solvents.

[0017] In some embodiments, the electrolyte salt includes at least one selected from lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt, and aluminum salt, and may be lithium salt or sodium salt.

[0018] In some embodiments, the lithium salt includes LiPF6, LiBOB, LiDFOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiN(SO2F)2, LiClO4, LiAlCl4, LiCF3SO3, and Li2B. 10 Cl 10 At least one of the following: lithium salts of lower aliphatic carboxylic acids.

[0019] In some embodiments, when the electrolyte salt is a lithium salt, the concentration of the lithium salt in the electrolyte is 0.1-8 mol / L.

[0020] In some embodiments, the sodium salt includes at least one of sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

[0021] In some embodiments, when the electrolyte salt is a sodium salt, the concentration of the sodium salt in the electrolyte is 0.1-2 mol / L.

[0022] In some embodiments, the electrolyte further includes auxiliary additives selected from at least one of cyclic carbonate compounds, cyclic sulfate compounds, sulfonyl lactone compounds, phosphate compounds, borate ester compounds, and nitrile compounds.

[0023] In some embodiments, the cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate, or a compound having the structure shown in Formula 2.

[0024] In Equation 2, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group.

[0025] In some embodiments, the cyclic sulfate compound is selected from vinyl sulfate, 4-methylvinyl sulfate, propylene sulfate, etc. At least one of them.

[0026] In some embodiments, the sulfonyl lactone compound is selected from 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, propenyl-1,3-sulfonyl lactone, etc. At least one of them.

[0027] In some embodiments, the phosphate ester compounds include saturated phosphate ester compounds and unsaturated phosphate ester compounds, wherein the saturated phosphate ester compounds include tris(trimethylsilane) phosphate esters, and the unsaturated phosphate ester compounds include compounds having the structure shown in Formula 3:

[0028] In Equation 3, R 31 R 32 R 32 Each group is independently selected from C1-C5 saturated hydrocarbon groups, C1-C5 unsaturated hydrocarbon groups, C1-C5 halohydrocarbon groups, or -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and the R 31 The R 32 The R 33 At least one of them is an unsaturated hydrocarbon group.

[0029] In some embodiments, the borate ester compound includes at least one of tris(trimethylsilane)borate and tris(triethylsilane)borate.

[0030] In some embodiments, the nitrile compound includes at least one selected from succinic anhydride, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octadionitrile, nonadionitrile, and sebaconitil.

[0031] Thirdly, embodiments of this disclosure provide a secondary battery, including a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte is the electrolyte described in any of the embodiments of the second aspect of this disclosure.

[0032] In some embodiments, the secondary battery is selected from lithium metal batteries, lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, magnesium-ion batteries, potassium-ion batteries, zinc-ion batteries, or lithium aluminum ions.

[0033] In some embodiments, the secondary battery is a lithium-ion battery, and the positive electrode active material of the secondary battery is selected from lithium-containing sulfides, lithium-containing selenides, lithium-containing halides, and LiFe. 1-x’ M' x’ PO4, LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M1-x-y-z At least one of O2, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1;

[0034] In other embodiments, the secondary battery is a sodium-ion battery, and the positive electrode active material is selected from at least one of sodium-containing transition metal oxides, sodium-containing Prussian materials, sodium-containing phosphates, sodium-containing sulfates, and sodium-containing titanates.

[0035] The electrolyte additives described in this disclosure can bring at least the following beneficial effects:

[0036] This electrolyte additive contains a compound with the structure shown in Formula 1—a cyclic structure with sulfate, sulfite, or carbonate groups at both ends linked by a cyclic structure containing a ketone carbonyl group in the middle. The ketone carbonyl group can coordinate with metal ions (e.g., lithium ions) in the electrolyte salt, which facilitates the additive's movement to the electrode surface with the current and the occurrence of electrochemical reactions on the electrode surface. Simultaneously, during the electrochemical reaction, it is empirically predicted that the cyclic sulfate, cyclic sulfite, and cyclic carbonate open their rings and react with the electrolyte salt (e.g., lithium salt) in the electrolyte to form organic electrolyte salts (e.g., organic lithium salts). At the same time, the cyclic ketone structure opens its ring and polymerizes and crosslinks with organic matter in the battery or itself to form a stable, structurally strong, and ion-permeable dual electrolyte salt (e.g., lithium salt) organic film, thereby improving the battery's high-temperature storage and high-temperature cycling performance.

[0037] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Detailed Implementation

[0038] The embodiments of this disclosure are described in detail below. These embodiments are exemplary and intended to explain this disclosure, and should not be construed as limiting this disclosure.

[0039] In this disclosure, the disclosure of numerical ranges includes all values ​​throughout the range and the disclosure of further subdivisions of the range, including the endpoints and subranges given for these ranges.

[0040] Unless otherwise specified, all raw materials and equipment involved in this disclosure are those that can be manufactured commercially or by known methods; and all methods involved are conventional methods unless otherwise specified.

[0041] <Electrolyte Additives>

[0042] The electrolyte additives of this disclosure include compounds having the structure shown in Formula 1:

[0043] Where X and Y are each independently selected R1 and R2 are each independently selected from single bonds, substituted or unsubstituted -CH2-, or substituted or unsubstituted -CH2-CH2-.

[0044] In embodiments of this disclosure, the term "substitution" means that hydrogen in the structure is replaced by a substituent (e.g., halogen).

[0045] In some embodiments, the substituents in the substituted -CH2- and substituted -CH2-CH2- are halogens.

[0046] In embodiments of this disclosure, the term "halogen" refers to F, Cl, Br, or I.

[0047] In some embodiments, the compound with the structure shown in Formula 1 above includes at least one of compound 1 to compound 10:

[0048] Those skilled in the art, knowing the structural formula of the compound shown in structural formula 1, can understand the preparation method of the above compound based on common knowledge in the field of chemical synthesis. For example:

[0049] Compound 1 can be prepared by the following method: 1,4-cyclohexanedione is condensed with 4-6 equivalents of formaldehyde aqueous solution in 1-10 wt% (e.g., 5.5 wt%) of calcium oxide at 30-80°C (e.g., 55°C) to prepare tetrahydroxymethylcyclohexanedione. Then, tetrahydroxycyclohexanedione is reacted with 2-3 equivalents (e.g., 2.5 equivalents) of sulfite at 30-80°C (e.g., 55°C) to prepare sulfite. Then, it is oxidized with 2-3 equivalents (e.g., 2.5 equivalents) of hydrogen peroxide (e.g., hydrogen peroxide with a mass content of 20%) under 0.1-1 wt% phosphotungstic acid catalysis to obtain crude compound 1. After recrystallization, compound 1 is obtained.

[0050] By way of non-limiting example, compound 2 can be prepared by aldol condensation of 1,4-cyclohexanedione with 4 to 6 equivalents (e.g., 5 equivalents, etc.) of aqueous formaldehyde in 1 to 10 wt% (e.g., 5.5 wt%, etc.) of calcium oxide at 30 to 80°C (e.g., 55°C, etc.) to prepare tetrahydroxymethylcyclohexanedione, and then preparing crude compound 2 by reacting tetrahydroxycyclohexanedione with 2 to 10 equivalents (e.g., 6 equivalents, etc.) of dimethyl carbonate in 0.1 to 10 wt% (e.g., 5 wt%, etc.) of potassium carbonate under catalysis, and then recrystallizing to prepare compound 2.

[0051] By way of non-limiting example, compound 3 can be prepared by aldol condensation of 1,3-cyclopentanedione with 4 to 6 equivalents (e.g., 5 equivalents, etc.) of aqueous formaldehyde in 1 to 10 wt% (e.g., 5.5 wt%, etc.) of calcium oxide at 30 to 80°C (e.g., 55°C, etc.) to prepare tetrahydroxymethylcyclopentanedione. Then, tetrahydroxycyclopentanedione is reacted with 2 to 3 equivalents (e.g., 2.5 equivalents, etc.) of thionyl chloride at 30 to 80°C (e.g., 55°C, etc.) to prepare sulfite. Then, it is oxidized with 0.1 to 1 wt% (e.g., 0.5 wt%, etc.) of phosphotungstic acid catalyzed by 2 to 3 equivalents (e.g., 2.5 equivalents, etc.) of hydrogen peroxide (e.g., hydrogen peroxide with a mass content of 20%) to obtain crude compound 3. After recrystallization, compound 3 is obtained.

[0052] By way of non-limiting example, compound 4 can be prepared by aldol condensation of 1,3-cyclopentanedione with 4 to 6 equivalents (e.g., 5 equivalents, etc.) of aqueous formaldehyde in 1 to 10 wt% (e.g., 5.5 wt%) of calcium oxide at 30 to 80°C (e.g., 55°C, etc.) to prepare tetrahydroxymethylcyclopentanedione. Then, the tetrahydroxycyclopentanedione is reacted with 2 to 3 equivalents (e.g., 2.5 equivalents, etc.) of sulfoxide at 30 to 80°C (e.g., 55°C, etc.) to prepare crude compound 4. After recrystallization, compound 4 is obtained.

[0053] By way of non-limiting example, compound 5 can be prepared by aldol condensation of 1,3-cyclobutanedione with 4 to 6 equivalents (e.g., 5 equivalents, etc.) of aqueous formaldehyde in 1 to 10 wt% (e.g., 5.5 wt%) of calcium oxide at 30 to 80°C (e.g., 55°C, etc.) to prepare tetrahydroxymethylcyclobutanedione. Then, tetrahydroxycyclobutanedione is reacted with 2 to 3 equivalents (e.g., 2.5 equivalents, etc.) of sulfite at 30 to 80°C (e.g., 55°C, etc.) to prepare a sulfite ester. This ester is then oxidized with 2 to 3 equivalents (e.g., 2.5 equivalents, etc.) of hydrogen peroxide (e.g., hydrogen peroxide with a mass content of 20%) catalyzed by 0.1 to 1 wt% phosphotungstic acid to obtain crude compound 5, which is then recrystallized to obtain compound 5.

[0054] By way of non-limiting example, compound 6 can be prepared by aldol condensation of 1,4-cyclohexanedione with 4 to 6 equivalents (e.g., 5 equivalents, etc.) of aqueous formaldehyde in 1 to 10 wt% (e.g., 5.5 wt%) of calcium oxide at 30 to 80°C (e.g., 55°C, etc.) to prepare tetrahydroxymethylcyclohexanedione. Then, tetrahydroxycyclohexanedione is reacted with 2 to 3 equivalents (e.g., 2.5 equivalents, etc.) of sulfite at 30 to 80°C (e.g., 55°C, etc.) to prepare a sulfite ester. This ester is then oxidized with 0.5 to 2 equivalents (e.g., 1.2 equivalents, etc.) of hydrogen peroxide (e.g., hydrogen peroxide with a mass content of 20%) under 0.1 to 1 wt% phosphotungstic acid catalysis to obtain crude compound 6. Recrystallization yields compound 6.

[0055] By way of non-limiting example, compound 7 can be prepared by aldol condensation of 1,3-cyclohexanedione with 4 to 6 equivalents (e.g., 5 equivalents, etc.) of aqueous formaldehyde in 1 to 10 wt% (e.g., 5.5 wt%) of calcium oxide at 30 to 80°C (e.g., 55°C, etc.) to prepare tetrahydroxymethylcyclohexanedione. Then, tetrahydroxycyclohexanedione is reacted with 2 to 3 equivalents (e.g., 2.5 equivalents, etc.) of sulfite at 30 to 80°C (e.g., 55°C, etc.) to prepare a sulfite ester. This ester is then oxidized with 0.1 to 1 wt% (e.g., 0.5 wt%) of phosphotungstic acid catalyzed by 2 to 3 equivalents (e.g., 2.5 equivalents, etc.) of hydrogen peroxide (e.g., hydrogen peroxide with a mass content of 20%) to obtain crude compound 7, which is then recrystallized to obtain compound 7.

[0056] By way of non-limiting example, compound 8 can be prepared by aldol condensation of 1,3-cyclohexanedione with 4 to 6 equivalents (e.g., 5 equivalents, etc.) of aqueous formaldehyde in 1 to 10 wt% (e.g., 5.5 wt%, etc.) of calcium oxide at 30 to 80°C (e.g., 55°C, etc.) to prepare tetrahydroxymethylcyclohexanedione. Then, 2 to 10 equivalents (e.g., 6 equivalents, etc.) of dimethyl carbonate of tetrahydroxycyclohexanedione is used to prepare crude compound 8 under the catalysis of 0.1 to 10 wt% (e.g., 5.5 wt%, etc.) of potassium carbonate. Compound 8 is then prepared by recrystallization.

[0057] By way of non-limiting example, compound 9 can be prepared by aldol condensation of 1,4-cyclohexanedione with 4 to 6 equivalents (e.g., 5 equivalents, etc.) of aqueous formaldehyde in 1 to 10 wt% (e.g., 5.5 wt%) of calcium oxide at 30 to 80°C (e.g., 55°C, etc.) to prepare tetrahydroxymethylcyclohexanedione, and then reacting tetrahydroxycyclohexanedione with 0.5 to 1.5 equivalents (e.g., 1 equivalent, etc.) of sulfoxide at 30 to 80°C (e.g., 55°C, etc.) to prepare the compound. The product is then prepared by reacting dimethyl carbonate with 2 to 10 equivalents (e.g., 6 equivalents, etc.) of tetrahydroxycyclohexanedione under the catalysis of 0.1 to 10 wt% (e.g., 5.5 wt%, etc.) of potassium carbonate. Compound 9 crude product was obtained by oxidation with 0.1-1 wt% (e.g., 0.5 wt%) phosphotungstic acid catalyzed by 2-3 equivalents (e.g., 2.5 equivalents) of hydrogen peroxide (e.g., hydrogen peroxide with a mass content of 20%), and then recrystallized to obtain compound 9.

[0058] By way of non-limiting example, compound 10 can be prepared by aldol condensation of 1,3-cyclopentanedione with 4 to 6 equivalents (e.g., 5 equivalents, etc.) of aqueous formaldehyde in 1 to 10 wt% (e.g., 5.5 wt%, etc.) of calcium oxide at 30 to 80°C (e.g., 55°C, etc.) to prepare tetrahydroxymethylcyclopentanedione, and then reacting tetrahydroxycyclopentanedione with 0.5 to 1.5 equivalents (e.g., 1 equivalent, etc.) of sulfoxide at 30 to 80°C (e.g., 55°C, etc.) to prepare the compound. Then, add 2 to 10 equivalents (e.g., 6 equivalents, etc.) of dimethyl carbonate in 0.1 to 10 wt% (e.g., 5.5 wt%) of tetrahydroxycyclohexanedione.

[0059] Preparation of potassium carbonate Compound 10 crude product was obtained by oxidation with 2 to 3 equivalents (e.g., 2.5 equivalents, etc.) of hydrogen peroxide (e.g., hydrogen peroxide with a mass content of 20%) under 0.1 to 1 wt% phosphotungstic acid catalysis, and then recrystallized to obtain compound 10.

[0060] The equivalents and mass fractions mentioned above are relative to the main reactant.

[0061] The electrolyte additive of this disclosure contains a compound having the structure shown in Formula 1—a cyclic structure with sulfate, sulfite, or carbonate groups at both ends linked together by a cyclic structure containing a ketone carbonyl group in the middle. The ketone carbonyl group can coordinate with metal ions (e.g., lithium ions) in the electrolyte salt, which facilitates the additive moving to the electrode surface with the current and undergoing an electrochemical reaction on the electrode surface. At the same time, when the cyclic structure undergoes an electrochemical reaction, the ester-containing ring can open and react with the electrolyte salt (e.g., lithium salt) in the electrolyte to form an organic electrolyte salt (e.g., organic lithium salt). Simultaneously, the cyclic ketone structure opens and polymerizes and crosslinks with organic matter in the battery or itself to form a dual electrolyte salt (e.g., lithium salt) organic film with good stability, high structural strength, and good ion permeability, thereby improving the battery's high-temperature storage and high-temperature cycling performance.

[0062] Electrolyte

[0063] The electrolyte of this disclosure includes a non-aqueous organic solvent, an electrolyte salt, and an electrolyte additive of this disclosure.

[0064] In some embodiments, the compound with the structure shown in Formula 1 has a mass content of 0.05-10% in the electrolyte, based on the total mass of the electrolyte (100%), including but not limited to 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, or 10%.

[0065] In the embodiments of this disclosure, when the content of the compound of the structure shown in Formula 1 is within the above range, the stability of the film formed on the electrode surface can be effectively maintained and the battery performance can be improved. If the content of the compound of the structure shown in Formula 1 is too low, it is difficult to significantly improve the performance of the battery. If the content of the compound of the structure shown in Formula 1 is too high, it may affect the function of other substances in the electrolyte due to the excessive decomposition products.

[0066] As an alternative example, with the total mass of the electrolyte being 100%, the compound with the structure shown in Formula 1 has a mass content of 0.1-5% in the electrolyte.

[0067] In some embodiments, the electrolyte salt includes, but is not limited to, at least one of lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt, and aluminum salt.

[0068] As an alternative example, the electrolyte salt is a lithium salt or a sodium salt.

[0069] Alkali metal ions, formed by the dissociation of electrolyte salts in the electrolyte, intercalate and deintercalate between the positive and negative electrodes to complete the charge-discharge cycle. The concentration of the electrolyte salt directly affects the transfer rate of alkali metal ions, which in turn affects the potential change of the negative electrode. During fast charging, it is necessary to maximize the movement speed of alkali metal ions to prevent the negative electrode potential from dropping too quickly, which could lead to the formation of lithium dendrites and pose a safety hazard to the battery. This also helps prevent the battery's cycle capacity from decaying too rapidly. If the electrolyte salt content is too low, the intercalation and deintercalation efficiency of alkali metal ions between the positive and negative electrodes will be reduced, failing to meet the requirements of fast charging. Conversely, if the electrolyte salt content is too high, the viscosity of the non-aqueous electrolyte will increase, which is also detrimental to improving the intercalation and deintercalation efficiency of alkali metal ions and increases the battery's internal resistance.

[0070] In some embodiments, lithium salts include, but are not limited to, LiPF6, LiBOB, LiDFOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiN(SO2F)2, LiClO4, LiAlCl4, LiCF3SO3, and Li2B. 10 Cl 10 At least one of the following: lithium salts of lower aliphatic carboxylic acids.

[0071] In some embodiments, when the electrolyte salt is a lithium salt, the concentration of the lithium salt in the electrolyte is 0.1-8 mol / L, including but not limited to 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, or 8 mol / L.

[0072] As an alternative example, when the electrolyte salt is a lithium salt, the concentration of the lithium salt in the electrolyte is 0.5-2.5 mol / L.

[0073] In some embodiments, the sodium salt includes, but is not limited to, at least one of sodium perchlorate (NaClO4), sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium bis(fluorosulfonyl)imide (NaFSI), sodium trifluoromethanesulfonate (NaOTf), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI).

[0074] In some embodiments, when the electrolyte salt is a sodium salt, the concentration of the sodium salt in the electrolyte is 0.1-2 mol / L, including but not limited to 0.1 mol / L, 0.4 mol / L, 0.5 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, or 2 mol / L.

[0075] As an alternative example, when the electrolyte salt is a sodium salt, and the concentration of the sodium salt in the electrolyte is 0.4-1.5 mol / L.

[0076] In some embodiments, the electrolyte further includes auxiliary additives, including but not limited to at least one of cyclic carbonate compounds, cyclic sulfate compounds, sulfonyl lactone compounds, phosphate compounds, borate ester compounds, and nitrile compounds.

[0077] In some embodiments, the cyclic carbonate compounds include, but are not limited to, at least one of vinylene carbonate, ethylene ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate, or compounds having the structure shown in Formula 2.

[0078] In Equation 2, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group.

[0079] By way of non-limiting example, C1-C5 groups include, but are not limited to, C1-C5 cyano, C1-C5 ester, C1-C5 alkyl, trifluoromethyl, or C1-C5 sulfonate groups.

[0080] In embodiments of this disclosure, the term "cyano" refers to -CN.

[0081] In the embodiments of this disclosure, the term "ester group" refers to the functional group of the ester in a carboxylic acid derivative, with the structural formula -COOR (R is generally an alkyl group or other non-H group).

[0082] In embodiments of this disclosure, the term "sulfonate group" refers to the formula -O-SO2-R i The group, wherein R i It is an alkyl group, etc.

[0083] As an optional example, the compounds having the structure shown in Formula 2 include, but are not limited to, at least one of the compounds shown in Compounds 2-1 to 2-6 below:

[0084] In some embodiments, the cyclic sulfate compound is selected from vinyl sulfate, 4-methylvinyl sulfate, propylene sulfate, etc. At least one of them.

[0085] In some embodiments, the sulfonyl lactone compound is selected from 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, propenyl-1,3-sulfonyl lactone, etc. At least one of them.

[0086] In some embodiments, the phosphate ester compounds include saturated phosphate ester compounds and unsaturated phosphate ester compounds, wherein the saturated phosphate ester compounds include tris(trimethylsilane) phosphate esters, and the unsaturated phosphate ester compounds include compounds having the structure shown in Formula 3:

[0087] In Equation 3, R 31 R 32 R 32 Each group is independently selected from C1-C5 saturated hydrocarbon groups, C1-C5 unsaturated hydrocarbon groups, C1-C5 halohydrocarbon groups, or -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 R 32 R 33 At least one of them is an unsaturated hydrocarbon group.

[0088] In the embodiments of this disclosure, the term "saturated hydrocarbon group," also known as alkyl, refers to a straight-chain or branched alkyl radical containing 1 to 5 carbon atoms. Examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, etc.

[0089] In the embodiments of this disclosure, the term "unsaturated hydrocarbon group" refers to a hydrocarbon compound whose molecule contains carbon-carbon double or triple bonds.

[0090] By way of non-limiting example, the C1-C5 unsaturated hydrocarbon groups and C1-C5 haloalkanes have 1, 2, 3, 4, or 5 carbon atoms. For example, C1-C5 unsaturated hydrocarbon groups include, but are not limited to, vinyl, ethynyl, propenyl, 2-methylpropene, 1,4-butadienyl, propynyl, etc. C1-C5 haloalkanes include, but are not limited to, trifluoromethyl, trifluoroethyl, monofluoropropyl, monofluorobutyl, or difluoropentyl, etc.

[0091] As a non-restrictive example, the value of m above can be 1, 2, or 3, that is, Si(C m H 2m+1 )3 can be Si(CH3)3, Si(C2H5)3, or Si(C3H7)3.

[0092] As an optional example, the compounds having the structure shown in Formula 3 include, but are not limited to, at least one of the following: triargyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, diallyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate.

[0093] In some embodiments, the borate ester compound includes, but is not limited to, at least one of tris(trimethylsilane)borate, tris(triethylsilane)borate, etc.

[0094] In some embodiments, the nitrile compound includes, but is not limited to, at least one of succinic acid, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octadionitrile, nonadionitrile, sebaconitol, etc.

[0095] In the embodiments of this disclosure, with the total mass of the electrolyte as 100%, the mass content of the auxiliary additives in the electrolyte varies depending on the type of auxiliary additive chosen. Specifically, in some embodiments, when the auxiliary additive is selected from at least one of the following substances other than fluoroethylene carbonate: cyclic carbonates, cyclic sulfates, sulfonyl lactones, phosphates, borates, and nitriles, the content of any one of these optional substances in the non-aqueous electrolyte is less than 10%, including but not limited to 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, etc. 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%, etc.; optionally, the content of any of the above optional substances in the non-aqueous electrolyte is 0.1-5%, and further optionally 0.1% to 3%. In other embodiments, when fluoroethylene carbonate is selected as the auxiliary additive, the content of fluoroethylene carbonate is 0.05% to 30% based on the total mass of the electrolyte (100%), including but not limited to 0.05%, 1%, 2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 22.5%, 25%, 27.5%, or 30%.

[0096] In the electrolyte of the embodiments of this disclosure, compared with single addition or combination of other existing additives, when the compound shown in structural formula 1 is added together with the auxiliary additive, it shows a significant synergistic effect in improving battery performance. This indicates that the compound shown in structural formula 1 and the auxiliary additive can form a film together on the electrode surface to compensate for the film formation defects of single addition and obtain a more stable passivation film.

[0097] In some embodiments, the non-aqueous organic solvent includes, but is not limited to, at least one of ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents, and sulfone solvents.

[0098] In some embodiments, the ether solvent includes cyclic ethers or chain ethers.

[0099] By way of non-limiting example, cyclic ethers may specifically include, but are not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), 2-trifluoromethyltetrahydrofuran (2-CF3-THF), etc.

[0100] By way of non-limiting example, the chain ether may specifically include, but is not limited to, at least one of dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), diethylene glycol dimethyl ether (TEGDME), etc.

[0101] By way of a non-limiting example, nitrile solvents may specifically include, but are not limited to, at least one of acetonitrile, glutaronitrile, malononitrile, etc.

[0102] In some embodiments, carbonate solvents include, but are not limited to, cyclic carbonates or chain carbonates.

[0103] By way of non-limiting example, cyclic carbonates may specifically include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), gamma-butyrolactone (GBL), butylene carbonate (BC), etc.

[0104] By way of non-limiting example, the chain carbonate may specifically include, but is not limited to, at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), etc.

[0105] By way of non-limiting example, carboxylic acid ester solvents may specifically include, but are not limited to, at least one of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate, etc.

[0106] By way of non-limiting example, sulfone solvents include, but are not limited to, at least one of dimethyl sulfoxide, sulfolane, diethyl sulfone, methyl ethyl sulfone, or dimethyl sulfone.

[0107] Secondary batteries

[0108] The secondary battery of this disclosure embodiment includes a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte is the electrolyte of this disclosure embodiment.

[0109] In some embodiments, the secondary battery is selected from lithium metal batteries, lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, magnesium-ion batteries, potassium-ion batteries, zinc-ion batteries, or lithium aluminum ions.

[0110] In some embodiments, the positive electrode includes a positive electrode material layer, which includes a positive electrode active material. There are no particular restrictions on the type and content of the positive electrode active material, which can be selected according to actual needs. It can be any positive electrode active material or conversion type positive electrode material that can reversibly insert / deintercalate metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions, aluminum ions, etc.).

[0111] As an alternative example, the secondary battery is a lithium-ion battery, and the positive electrode active material of the secondary battery includes, but is not limited to, lithium-containing sulfides, lithium-containing selenides, lithium-containing halides, and LiFe. 1-x’ M' x’ PO4, LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z At least one of O2, etc., wherein M' includes, but is not limited to, at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, etc., and M includes, but is not limited to, at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, etc., and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

[0112] As a non-restrictive enumeration, the values ​​of x', y', y, x, z, and x+y+z include, but are not limited to, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.

[0113] As an alternative example, when the secondary battery is a lithium-ion battery, the positive electrode active material of the secondary battery can be selected from LiCoO2, LiFePO4, LiFe 0.8 Mn 0.2 PO4, LiMn2O4, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O2, LiNi 0.5 Co 0.2 Al 0.3At least one of O2.

[0114] In other embodiments, the secondary battery is a sodium-ion battery, and the positive electrode active material includes, but is not limited to, at least one of sodium-containing transition metal oxides, sodium-containing Prussian materials, sodium-containing phosphates, sodium-containing sulfates, and sodium-containing titanates.

[0115] In some embodiments, the sodium-containing transition metal oxide may be Na. a T b O c T includes, but is not limited to, at least one of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V, etc., where 1≤a≤10, 1≤b≤5, and 1≤c≤20.

[0116] As a non-restrictive enumeration, the values ​​of a include, but are not limited to, 1, 3, 5, 8, or 10; the values ​​of b include, but are not limited to, 1, 2, 3, 4, or 5; and the values ​​of c include, but are not limited to, 1, 3, 5, 7, 10, 13, 15, or 19.

[0117] Optionally, the sodium-containing transition metal oxide is NaNi. m Fe n Mn p O2 (m+n+p=1, 0≤m≤1, 0≤n≤1, 0≤p≤1) or NaNi m Co n Mn p O2(m+n+p=1, 0≤m≤1, 0≤n≤1, 0≤p≤1).

[0118] As a non-restrictive enumeration, the values ​​of m, n, and p include, but are not limited to, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.

[0119] In some embodiments, the molecular formula of the sodium-containing Prussian-like material is Na. d Q[Q′(CN)6] e ·fH₂O, where Q is a transition metal, Q′ is a transition metal, and 0 <d≤2,0.8≤e<1,0<f≤20。

[0120] By way of non-limiting enumeration, Q and Q′ include, but are not limited to, at least one of Cr, Fe, Co, Ni, Cu, Mn, Mo, V, Ti, Zr, etc.

[0121] As a non-restrictive enumeration, the values ​​of d include, but are not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.3, 1.5, 1.8, or 2.

[0122] As a non-restrictive enumeration, the values ​​of e include, but are not limited to, 0.8, 0.85, 0.9, or 0.95.

[0123] As a non-restrictive enumeration, the values ​​of f include, but are not limited to, 0.1, 0.5, 1, 5, 10, 15, or 20.

[0124] Optionally, the sodium-containing Prussian material is Na. h Mn[Fe(CN)6] i ·jH2O (0<h≤2,0<i≤1,0<j≤10) or Na h Fe[Fe(CN)6] i ·jH2O (0<h≤2, 0<i≤1, 0<j≤10).

[0125] As a non-restrictive enumeration, the values ​​of h include, but are not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.3, 1.5, 1.8, or 2.

[0126] As a non-restrictive enumeration, the values ​​of i include, but are not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.

[0127] As a non-restrictive enumeration, the values ​​of j include, but are not limited to, 0.1, 0.5, 1, 3, 5, 8, or 10.

[0128] In some embodiments, the sodium-containing phosphate has the chemical formula Na3(GO). 1-k PO4)2F 1+2k , 0≤k≤1, G is selected from at least one of Al, V, Ge, Fe, Ga, and optionally, the sodium-containing phosphate is Na3(VPO4)2F3 or Na3(VOPO4)2F.

[0129] As a non-restrictive list, the values ​​of k include, but are not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.

[0130] In other embodiments, the sodium-containing phosphate has the chemical formula Na2JPO4F, where J is selected from at least one of Fe and Mn. Optionally, the sodium-containing phosphate is Na2FePO4F or Na2MnPO4F.

[0131] In some embodiments, sodium-containing titanate materials include, but are not limited to, Na2Ti3O7 and Na2Ti6O7. 13 Na4Ti5O 12 Li4Ti5O 12At least one of NaTi2(PO4)3, etc.

[0132] In some embodiments, the sodium-containing sulfate has the chemical formula Na2Z(SO4)2·2H2O, where Z can be selected from at least one of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V.

[0133] In some embodiments, the positive electrode further includes a positive electrode current collector, and the positive electrode material layer is disposed on the surface of the positive electrode current collector.

[0134] In some embodiments, the positive current collector is selected from a metallic material capable of conducting electrons; optionally, the positive current collector includes at least one of Al, Ni, tin, copper, and stainless steel. As an optional example, the positive current collector is selected from aluminum foil.

[0135] In some embodiments, the above-mentioned positive electrode active material layer further includes a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder and the positive electrode conductive agent are blended to obtain the positive electrode material layer.

[0136] In some embodiments, the positive electrode binder includes, but is not limited to, at least one of the following: polyvinylidene fluoride, copolymers of polyvinylidene fluoride, polytetrafluoroethylene, copolymers of polyvinylidene fluoride and hexafluoropropylene, copolymers of tetrafluoroethylene and hexafluoropropylene, copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ethers, copolymers of ethylene and tetrafluoroethylene, copolymers of polyvinylidene fluoride and tetrafluoroethylene, copolymers of polyvinylidene fluoride and trifluoroethylene, copolymers of polyvinylidene fluoride and trichloroethylene, copolymers of polyvinylidene fluoride and fluorinated vinylides, copolymers of polyvinylidene fluoride and hexafluoropropylene and tetrafluoroethylene, thermoplastic polyimide, thermoplastic resins such as polyethylene and polypropylene; acrylic resins; and styrene-butadiene rubber.

[0137] In some embodiments, the positive electrode conductive agent includes, but is not limited to, at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene, or reduced graphene oxide.

[0138] In some embodiments, the negative electrode includes a negative electrode material layer, which includes a negative electrode active material. The type and content of the negative electrode active material are not particularly limited and can be selected according to actual needs.

[0139] In optional embodiments, the secondary battery is a lithium-ion battery, and its negative electrode active material includes, but is not limited to, at least one of carbon-based negative electrodes, silicon-based negative electrodes, tin-based negative electrodes, and lithium negative electrodes. Specifically, carbon-based negative electrodes may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.; silicon-based negative electrodes may include silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials; tin-based negative electrodes may include tin, tin-carbon, tin-oxygen, and tin metal compounds; and lithium negative electrodes may include metallic lithium or lithium alloys. The lithium alloy may specifically be at least one of lithium-silicon alloys, lithium-sodium alloys, lithium-potassium alloys, lithium-aluminum alloys, lithium-tin alloys, and lithium-indium alloys.

[0140] In an optional embodiment, the secondary battery is a sodium-ion battery, and its negative electrode active material includes, but is not limited to, at least one of metallic sodium, graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate, or other metals that can form alloys with sodium. The alloy material may also be selected from at least one of Si, Ge, Sn, Pb, and Sb combined with C; the graphite may be selected from at least one of artificial graphite, natural graphite, and modified graphite; the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys; and the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.

[0141] In some embodiments, the negative electrode further includes a negative electrode current collector, and the negative electrode material layer is disposed on the surface of the negative electrode current collector. The material of the negative electrode current collector can be the same as that of the positive electrode current collector, and will not be described again here.

[0142] In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, negative electrode binder, and negative electrode conductive agent are blended to obtain the negative electrode material layer. The negative electrode binder and negative electrode conductive agent can be the same as the positive electrode binder and positive electrode conductive agent, respectively, and will not be described in detail here.

[0143] In some embodiments, the secondary battery also includes a separator located between the positive and negative electrodes.

[0144] In some embodiments, the diaphragm can be a conventional diaphragm, such as a ceramic diaphragm, a polymer diaphragm, a nonwoven fabric, an inorganic-organic composite diaphragm, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP, and triple-layer PP / PE / PP diaphragms.

[0145] The secondary battery of this disclosure embodiment uses the electrolyte of this disclosure embodiment. The compound shown in Structural Formula 1 can form a high-performance passivation film on the positive and negative electrodes, thereby effectively improving the high-temperature storage performance and high-temperature cycle performance of the battery, and enhancing the battery power characteristics. In addition, since the secondary battery of this disclosure embodiment uses the electrolyte of this embodiment, it is reasonably presumed that the ketone carbonyl group in the compound shown in Structural Formula 1 can coordinate with the metal (e.g., lithium) in the electrolyte salt and move to the electrode surface with the current to undergo an electrochemical reaction. The cyclic sulfate, cyclic sulfite, and cyclic carbonate open the ring to form an organic sulfuric acid / sulfite / carbonate electrolyte salt (e.g., organic lithium sulfate). At the same time, the ketone carbonyl group opens the ring and cross-links with each other to form a dual electrolyte salt (e.g., lithium salt) organic film with good stability, high structural strength, and good ion permeability, thereby improving the high-temperature storage and high-temperature cycle performance of the battery.

[0146] The following non-limiting embodiments further illustrate certain features of this disclosure.

[0147] I. Performance Testing

[0148] 1. High-temperature cycling performance testing

[0149] The test method is as follows: after formation, the battery is left to stand at 45°C for 2 hours, charged at a constant current rate of 0.5C to 4.0V, then charged at a constant voltage to a current of 0.03C, and then discharged at a constant current rate of 1C to 1.5V, and cycled for 1000 times.

[0150] Measure the initial discharge capacity D1, initial battery volume V1, retention capacity D2 after 1000 cycles, recovery capacity D3, battery volume V2 after cycles, and battery coulombic efficiency E.

[0151] The calculation formula is as follows:

[0152] Battery capacity retention rate (%) after 1000 cycles = Capacity D2 / Initial capacity D1 × 100%;

[0153] Battery capacity recovery rate (%) after 1000 cycles = Capacity D3 / Initial capacity D1 × 100%

[0154] Volume expansion rate (%) = (Battery volume after cycle V2 - Initial battery volume V1) / Initial battery volume V1 × 100%.

[0155] 2. High-temperature storage performance test

[0156] The test method is as follows: After formation, the battery is charged at a constant current of 0.5C to 4.0V at room temperature, then charged at a constant voltage until the current drops to 0.03C, and then discharged at a constant current of 1C to 1.5V. The initial discharge capacity D1, initial battery volume V1, and initial impedance F1 of the battery are measured. After being fully charged, the battery is stored in an environment of 60℃ for 30 days, and then discharged at 1C to 3V. The battery retention capacity D2, recovery capacity D3, impedance F2 after storage, and battery volume V2 after storage are measured.

[0157] The calculation formula is as follows:

[0158] Battery capacity retention rate (%) = Retained capacity D2 / Initial capacity D1 × 100%;

[0159] Battery capacity recovery rate (%) = Recovered capacity D3 / Initial capacity D1 × 100%;

[0160] Volume expansion rate (%) = (Battery volume after storage V2 - Initial battery volume V1) / Initial battery volume V1 × 100%;

[0161] Internal resistance growth rate (%) = Impedance after storage F2 / Initial impedance F1 × 100%.

[0162] II. Examples and Comparative Examples

[0163] The compounds involved in each embodiment and comparative example are shown in Table 1:

[0164] Table 1 shows the compounds involved in each example and comparative example.

[0165] 1. Lithium-ion batteries (Examples 1-18 and Comparative Examples 1-9)

[0166] Example 1

[0167] <Methods for preparing electrolyte>

[0168] The electrolyte preparation method of this embodiment is as follows: ethylene carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC) are mixed in a mass ratio of EC:DEC:EMC = 0.9:1:1, and then lithium hexafluorophosphate (LiPF6) is added to a molar concentration of 1.1 mol / L. Based on the total weight of the electrolyte being 100%, 0.05% of an additive, namely compound 1, is added.

[0169] <Preparation Methods of Lithium-ion Batteries>

[0170] The method for preparing a lithium-ion battery in this embodiment includes the following steps:

[0171] 1) Preparation of the positive electrode: Lithium nickel cobalt manganese oxide (LiNiO) was mixed with the positive electrode active material in a mass ratio of 93:4:3. 0.5 Co 0.2 Mn 0.3 O2, conductive carbon black Super-P, and the binder polyvinylidene fluoride (PVDF) were dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry with a viscosity of approximately 6000 mPa·s. The slurry was uniformly coated on opposite surfaces of an 18 μm thick aluminum foil, dried, calendered, and vacuum dried. Aluminum leads were then welded onto the foil using an ultrasonic welder to obtain a positive electrode sheet with a thickness of 120 μm.

[0172] 2) Preparation of the negative electrode:

[0173] Artificial graphite, conductive carbon black Super-P, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 94:1:2.5:2.5 and then dispersed in deionized water to obtain a negative electrode slurry with a viscosity of approximately 4000 mPa·s. The slurry was coated onto the opposite surfaces of an 8 μm thick copper foil, dried, calendered, and vacuum dried. Nickel leads were then welded on using an ultrasonic welder to obtain a negative electrode plate with a thickness of 120 μm.

[0174] 3) Cell fabrication:

[0175] A three-layer PP / PE / PP separator with a thickness of 20μm is placed between the positive and negative electrodes. Then, the sandwich structure composed of the positive electrode, negative electrode and separator is wound up, and the wound body is flattened and placed in an aluminum foil packaging bag. It is then vacuum baked at 75℃ for 48h to obtain the battery cell to be injected with electrolyte.

[0176] 4) Electrolyte injection and formation of the battery cell:

[0177] In a glove box with the dew point controlled below -40°C, the electrolyte prepared in this embodiment was injected into the battery cell, vacuum sealed, and left to stand for 24 hours.

[0178] The initial formation was then performed as follows: constant current charging at 0.05C for 180 minutes, constant current charging at 0.2C to 3.95V, followed by a second vacuum sealing. Then, it was further charged at a constant current of 0.2C to 4.2V, left to stand at room temperature for 24 hours, and finally discharged at a constant current of 0.2C to 3.0V to obtain a LiNi alloy. 0.5 Co 0.2 Mn 0.3 O2 / artificial graphite lithium-ion battery.

[0179] Examples 1-18 and Comparative Examples 1-9 are basically the same as Example 1, except that the selection and dosage of some additives are different. It should be noted that the additives here include the compound shown in structural formula 1 (electrolyte additive) and / or auxiliary additives.

[0180] Examples 1-9 and Comparative Examples 1-5 investigated the effects of different contents of the compound shown in Structural Formula 1 of this disclosure, specific contents of the same electrolyte additive of this disclosure combined with auxiliary additives, no additives used, and only auxiliary additives used on the high-temperature cycle performance of lithium-ion batteries, as shown in Tables 2 and 3.

[0181] Table 2. Selection of some substances and parameters, and high-temperature cycling performance in Examples 1-9 and Comparative Examples 1-5.

[0182] According to Table 2:

[0183] Comparing the test results of Examples 1-8, it can be seen that as the amount of compound 1 shown in Structural Formula 1 increases, the volume expansion rate of the lithium-ion battery first decreases and then increases, while the capacity retention rate and capacity recovery first increase and then decrease. This indicates that both excessive and insufficient addition will improve the high-temperature cycle performance of the lithium-ion battery. In particular, when the amount of compound 1 shown in Structural Formula 1 is 0.5-5 wt%, the lithium-ion battery has the best high-temperature cycle performance.

[0184] Comparing the test results of Examples 1-8 and Comparative Examples 1-4, it can be seen that, compared with traditional vinylene carbonate (VC), vinyl sulfate (DTD) and 1,3-propanesulfonate lactone (PS), using compound 1 of structural formula 1 provided in this disclosure as an additive can more significantly improve the cycle performance of lithium-ion batteries at high temperatures, indicating that the passivation film formed by compound 1 of structural formula 1 is more stable and has better lithium-ion permeability.

[0185] Comparing the test results of Example 9 and Comparative Example 5, it can be seen that when Compound 1 of Structural Formula 1 provided in this disclosure is used together with ethylene carbonate (VC) as an additive, it can further improve the cycle performance of lithium-ion batteries at high temperatures compared with DTD and ethylene carbonate (VC) as additives.

[0186] Examples 4, 10-18, and Comparative Examples 1-4 investigated the effects of the same content of the compounds shown in different structural formulas 1 of this disclosure, the absence of any additives, and the use of only auxiliary additives on the high-temperature cycle performance of lithium-ion batteries, as shown in Table 3.

[0187] Table 3. Selection of materials and parameters, and high-temperature cycling performance in Examples 4, 10-18 and Comparative Examples 1-4.

[0188] Comparing the test results of Examples 4, 10-18 and Comparative Examples 1-4, it can be seen that, compared with lithium-ion batteries without additives or with existing additives, lithium-ion batteries using the compound shown in Structural Formula 1 provided in this disclosure as an additive have better high-temperature cycle performance.

[0189] Comparative Example 6 (the carbonyl ring in the middle of Structural Formula 1 is replaced with a carbonyl-containing acyclic structure).

[0190] This comparative example is basically the same as Example 4, except that:

[0191] Compound 1 was replaced with compound 11 in the electrolyte.

[0192] Comparative Example 7 (The carbonyl ring in the middle of Structural Formula 1 is replaced with a ring structure without a carbonyl group)

[0193] This comparative example is basically the same as Example 4, except that:

[0194] Compound 1 was replaced with compound 12 in the electrolyte.

[0195] Comparative Example 8 (The carbonyl ring in the middle of Structural Formula 1 is replaced with an acyclic structure containing a carbonyl group)

[0196] This comparative example is basically the same as Example 9, except that:

[0197] Compound 1 was replaced with compound 11 in the electrolyte.

[0198] Comparative Example 9 (The carbonyl ring in the middle of Structural Formula 1 is replaced with a ring structure without a carbonyl group)

[0199] This comparative example is basically the same as Example 9, except that:

[0200] Compound 1 was replaced with compound 12 in the electrolyte.

[0201] The high-temperature cycling performance test results of the lithium-ion batteries corresponding to Examples 4, 9 and Comparative Examples 6-9 are shown in Table 4.

[0202] Table 4. Selection of some substances and parameters, and high-temperature cycling performance in Examples 4 and 9 and Comparative Examples 6-9.

[0203] As can be seen from Table 4, Examples 4 and 9 and Comparative Examples 6 and 8 show that only carbonyl structures exist, and their high-temperature cycling performance is worse than that of existing additives, but not as good as that of Compound 1. It is speculated that without a cyclic structure, the cross-linked structure formed after carbonyl oxidation is not as stable as that of Compound 1. Examples 4 and 9 and Comparative Examples 7 and 9 show that only cyclic structures exist, and their high-temperature cycling performance is comparable to that of existing additives, but not as good as that of Compound 1. It is speculated that without a carbonyl structure, a cross-linked structure cannot be formed, resulting in a film strength that is not as good as that of Compound 1.

[0204] 2. Sodium-ion batteries (Examples 19-36 and Comparative Examples 10-15)

[0205] Example 19

[0206] <Methods for preparing electrolyte>

[0207] The electrolyte preparation method of this embodiment is as follows: ethylene carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC) are mixed in a mass ratio of EC:DEC:EMC = 1:1:1, and then sodium hexafluorophosphate (NaPF6) is added to a molar concentration of 1 mol / L. Based on the total weight of the electrolyte being 100%, 0.05% of an additive, namely compound 1, is added.

[0208] <Preparation Methods of Sodium-ion Batteries>

[0209] The method for preparing the sodium-ion battery in this embodiment includes the following steps:

[0210] 1) Preparation of the positive electrode:

[0211] The positive electrode active material Na3V2(PO4)3, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 94:3:3, and then dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry with a viscosity of approximately 8000 mPa·s. The slurry was uniformly coated on both sides of a 15 μm aluminum foil, and after drying, calendering, and vacuum drying, aluminum leads were welded on using an ultrasonic welder to obtain a positive electrode sheet with a thickness of 150 μm.

[0212] 2) Preparation of the negative electrode:

[0213] The negative electrode active materials, spherical hard carbon, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 97:1:1:1, and then dispersed in deionized water to obtain a negative electrode slurry with a viscosity of approximately 5000 mPa·s. The slurry was coated on both sides of a 15 μm aluminum foil, dried, calendered, and vacuum dried, and then nickel leads were welded on using an ultrasonic welder to obtain a negative electrode sheet with a thickness of 150 μm.

[0214] 3) The positive electrode, separator (20μm three-layer PP / PE / PP separator), and negative electrode are stacked in sequence, and then packaged with aluminum-plastic film, baked, injected with electrolyte, left to stand, formed, shaped with fixture, resealed, and capacity tested to complete the preparation of sodium-ion battery.

[0215] Examples 20-36 and Comparative Examples 10-15 are basically the same as Example 19, except that the selection and dosage of some additives are different. It should be noted that the additives here include the compound shown in structural formula 1 (electrolyte additive) and / or auxiliary additives.

[0216] in:

[0217] Examples 19-27 and Comparative Examples 10 and 11 investigated the effects of different contents of the compound shown in Structural Formula 1 of this disclosure, specific contents of the same electrolyte additive of this disclosure combined with auxiliary additives, no additives used, and only auxiliary additives used on the high-temperature storage performance of sodium-ion batteries, as shown in Table 5.

[0218] Table 5. Selection of some substances and parameters, and high-temperature storage performance in Examples 19-27 and Comparative Examples 10 and 11.

[0219] According to Table 5:

[0220] Comparing the test results of Examples 19-27, it can be seen that as the amount of Compound 1 shown in Structural Formula 1 increases, the volume expansion rate and internal resistance increase rate of the lithium-ion battery first decrease and then increase, while the capacity remains unchanged, first increasing and then decreasing. This indicates that both excessive and insufficient addition will improve the high-temperature storage performance of sodium-ion batteries and reduce their internal resistance growth. In particular, when the amount of Compound 1 shown in Structural Formula 1 is 0.5-5%, the sodium-ion battery has the best impedance reduction and high-temperature storage performance.

[0221] Comparing Example 22 and Comparative Examples 10-11, it can be seen that the addition of Compound 1 (Structural Formula 1) to the electrolyte significantly improves the high-temperature storage performance of the sodium-ion battery compared to the case without any additives and the case with existing additives.

[0222] Examples 22, 28-36 and Comparative Examples 10, 11 investigated the effects of the same content of the compounds shown in different structural formulas 1 of this disclosure, the absence of any additives, and the use of only auxiliary additives on the high-temperature cycle performance of sodium-ion batteries, as shown in Table 6.

[0223] Table 6. Selection of some substances and parameters, and high-temperature storage performance in Examples 22, 28-36 and Comparative Examples 10-11.

[0224] According to Table 6:

[0225] The test results of Examples 22, 28-36 and Comparative Examples 10, 11 show that, compared with sodium-ion batteries without additives or with existing additives, sodium-ion batteries using the compound shown in Structural Formula 1 provided in this disclosure as an additive have better high-temperature storage performance.

[0226] Comparative Example 12 (The carbonyl ring in the middle of Structural Formula 1 is replaced with a carbonyl-containing acyclic structure)

[0227] This comparative example is basically the same as Example 19, except that:

[0228] Compound 1 was replaced with compound 11 in the electrolyte.

[0229] Comparative Example 13 (The carbonyl ring in the middle of Structural Formula 2 is replaced with a ring structure without a carbonyl group)

[0230] This comparative example is basically the same as Example 22, except that:

[0231] Compound 1 was replaced with compound 12 in the electrolyte.

[0232] Comparative Example 14 (The carbonyl ring in the middle of Structural Formula 1 is replaced with a carbonyl-containing acyclic structure)

[0233] This comparative example is basically the same as Example 19, except that:

[0234] Compound 1 was replaced with compound 11 in the electrolyte.

[0235] Comparative Example 15 (The carbonyl ring in the middle of Structural Formula 1 is replaced with a ring structure without a carbonyl group)

[0236] This comparative example is basically the same as Example 22, except that:

[0237] Compound 1 was replaced with compound 12 in the electrolyte.

[0238] The high-temperature cycling performance test results of the sodium-ion batteries corresponding to Examples 19, 22 and Comparative Examples 10-15 are shown in Table 7.

[0239] Table 7. Selection of some substances and parameters, and high-temperature storage performance in Examples 19, 22 and Comparative Examples 10-15

[0240] As can be seen from Table 7, Examples 22 and Comparative Examples 10, 11, 13 and 15 show that only carbonyl structures have better high-temperature storage performance than existing additives, but not as good as Compound 1. It is speculated that the cross-linked structure formed after the oxidation of the carbonyl group without a ring structure is not as stable as that of Compound 1. The inability to form a cross-linked structure without a carbonyl structure results in a film strength that is not as good as that of Compound 1.

[0241] As can be seen from Examples 19 and Comparative Examples 10, 12 and 14, the carbonyl structure alone has better high-temperature storage performance than no additives, but not as good as Compound 1. It is speculated that the cross-linked structure formed after the oxidation of the carbonyl structure is not as stable as that of Compound 1. The film strength of Compound 1 is not as good as that of Compound 1 because the carbonyl structure cannot form a cross-linked structure.

[0242] In this disclosure, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, all embodiments of this disclosure can be performed individually. Without contradiction, those skilled in the art can combine and integrate different embodiments or examples described in this specification, as well as the features of different embodiments or examples, and all such combinations are considered to be within the scope of protection claimed by this disclosure.

[0243] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. An electrolyte additive comprising a compound having the structure shown in Formula 1: in, X and Y are each independently selected R1 and R2 are each independently selected from single bonds, substituted or unsubstituted -CH2-, or substituted or unsubstituted -CH2-CH2-.

2. The electrolyte additive according to claim 1, wherein, The substituents in the substituted or unsubstituted -CH2- and substituted or unsubstituted -CH2-CH2- are all halogens.

3. The electrolyte additive according to claim 1 or 2, wherein, The compounds with the structure shown in Formula 1 include at least one of compounds 1 to 10:

4. An electrolyte comprising a non-aqueous organic solvent, an electrolyte salt, and an electrolyte additive as described in any one of claims 1 to 3.

5. The electrolyte according to claim 4, wherein, The compound with the structure shown in Formula 1 has a mass content of 0.05-10% in the electrolyte; And / or, the non-aqueous organic solvent includes at least one of ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents, and sulfone solvents; And / or, the electrolyte salt includes at least one of lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt, and aluminum salt.

6. The electrolyte according to claim 5, wherein, The compound with the structure shown in Formula 1 has a mass content of 0.1-5% in the electrolyte; And / or, the electrolyte salt is a lithium salt or a sodium salt; And / or, the lithium salt includes LiPF6, LiBOB, LiDFOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiN(SO2F)2, LiClO4, LiAlCl4, LiCF3SO3, Li2B 10 Cl 10 At least one of the following: lower aliphatic lithium carboxylate salts; And / or, the sodium salt includes at least one of sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

7. The electrolyte according to claim 6, wherein, The electrolyte salt is a lithium salt, and the concentration of the lithium salt in the electrolyte is 0.1-8 mol / L; Alternatively, the electrolyte salt is a sodium salt, and the concentration of the sodium salt in the electrolyte is 0.1-2 mol / L.

8. The electrolyte according to any one of claims 4 to 7, wherein, It also includes auxiliary additives, which are selected from at least one of cyclic carbonate compounds, cyclic sulfate compounds, sulfonyl lactone compounds, phosphate compounds, borate compounds and nitrile compounds.

9. The electrolyte according to claim 8, wherein, The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate, or a compound having the structure shown in Formula 2. In Equation 2, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group; And / or, the cyclic sulfate compound is selected from vinyl sulfate, 4-methylvinyl sulfate, propylene sulfate, etc. At least one of them; And / or, the sulfonyl lactone compound is selected from 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, propenyl-1,3-sulfonyl lactone, At least one of them; And / or, the phosphate ester compounds include saturated phosphate ester compounds and unsaturated phosphate ester compounds, wherein the saturated phosphate ester compounds include tris(trimethylsilane) phosphate esters, and the unsaturated phosphate ester compounds include compounds having the structure shown in Formula 3: In Equation 3, R 31 R 32 R 32 Each group is independently selected from C1-C5 saturated hydrocarbon groups, C1-C5 unsaturated hydrocarbon groups, C1-C5 halohydrocarbon groups, or -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and the R 31 The R 32 The R 33 At least one of them is an unsaturated hydrocarbon group; And / or, the borate ester compound includes at least one of tris(trimethylsilane)borate ester and tris(triethylsilane)borate ester; And / or, the nitrile compounds include at least one of succinic anionyl nitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octanilide, nonadionitrile, and sebacate.

10. A secondary battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein, The electrolyte is the electrolyte as described in any one of claims 1 to 9.

11. The secondary battery according to claim 10, wherein, The secondary battery is selected from lithium metal batteries, lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, magnesium-ion batteries, potassium-ion batteries, zinc-ion batteries, or lithium aluminum ions.

12. The secondary battery according to claim 11, wherein, The secondary battery is a lithium-ion battery, and the positive electrode active material of the secondary battery is selected from lithium-containing sulfides, lithium-containing selenides, lithium-containing halides, and LiFe. 1-x’ M' x’ PO4, LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1- x-y-z At least one of O2, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1; Alternatively, the secondary battery is a sodium-ion battery, and the positive electrode active material is selected from at least one of sodium-containing transition metal oxides, sodium-containing Prussian materials, sodium-containing phosphates, sodium-containing sulfates, and sodium-containing titanates.

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