Non-aqueous electrolyte and secondary battery

Abstract

In order to overcome the problem of poor high-temperature storage performance of the secondary battery in the prior art, the application provides a non-aqueous electrolyte and a battery, which comprise an electrolyte salt, a non-aqueous organic solvent and an additive, wherein the additive comprises a compound shown in structural formula 1: wherein R1 and R2 are each independently selected from a hydrogen atom, a halogen atom, a C1-C5 hydrocarbon group or a C1-C5 halogenated hydrocarbon group. The non-aqueous electrolyte provided by the application can form a stable SEI film on the negative electrode surface, reduce the decomposition of the solvent on the negative electrode, and improve the high-temperature storage performance and high-temperature cycle performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of energy storage battery device technology, specifically relating to a non-aqueous electrolyte and a secondary battery. Background Technology

[0002] Rechargeable batteries, with their large capacity, fast charging speed, and long cycle life, are widely used in various electronic devices in daily life. Numerous studies have shown that the main reason for the shortened lifespan of rechargeable batteries is that the electrodes are prone to reacting with the electrolyte under high temperature and pressure conditions, causing electrode material loss and electrolyte deterioration. Furthermore, the large amounts of gas generated in these conditions often cause the battery to expand in size. All these changes easily lead to deterioration of battery performance and a shortened lifespan.

[0003] In existing technologies, to improve the performance of secondary batteries, many researchers have added various negative electrode film-forming additives to the electrolyte, such as vinylene carbonate, fluoroethylene carbonate, ethylene ethylene carbonate, and 1,3-propanesulfonate lactone, to improve the quality of the CEI or SEI film, thereby enhancing battery performance. However, adding these substances to the electrolyte does not effectively inhibit solvent decomposition on the positive or negative electrode surface, thus damaging the already formed CEI or SEI film. Consequently, the high-temperature storage and cycle performance of lithium-ion batteries remains poor. Therefore, developing a non-aqueous electrolyte that can ensure excellent electrochemical performance of secondary batteries at high temperatures is crucial. Summary of the Invention

[0004] To address the problem of poor high-temperature performance of existing secondary batteries, this application provides a non-aqueous electrolyte and a secondary battery.

[0005] To address the aforementioned technical problems, this application provides a non-aqueous electrolyte, comprising an electrolyte salt, a non-aqueous organic solvent, and an additive, wherein the additive comprises a compound shown in structural formula 1:

[0006]

[0007] R1 and R2 are each independently selected from hydrogen atoms, halogen atoms, C1-C5 hydrocarbon groups, or C1-C5 halohydrocarbon groups.

[0008] Preferably, the compound represented by structural formula 1 is selected from at least one of the following compounds:

[0009]

[0010] Preferably, based on the total mass of the non-aqueous electrolyte, the mass percentage of the compound represented by structural formula 1 is 0.05% to 10%.

[0011] Preferably, based on the total mass of the non-aqueous electrolyte, the mass percentage of the compound represented by structural formula 1 is 0.1% to 5%.

[0012] Preferably, the concentration of the electrolyte salt in the non-aqueous electrolyte is 0.1 mol / L to 8 mol / L;

[0013] The electrolyte salt is selected from lithium salt or sodium salt.

[0014] Preferably, the lithium salt is selected from 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: LiSO3F, LiTOP (lithium trioxane phosphate), LiDODFP (lithium difluorodioxane phosphate), LiOTFP (lithium tetrafluorooxane phosphate), and lower aliphatic carboxylic acid lithium salts;

[0015] The sodium salt is selected from at least one of NaPF6, NaClO4, NaAsF6, NaSbF6, NaPOF4, NaPO2F2, NaC4BO8, NaC2BF2O4, NaODFB, NaN(SO2C2F5)2, NaN(SO2CF3)(SO2C4F9)2, NaC(SO2CF3) and Na(C2F5)PF3.

[0016] Preferably, the non-aqueous electrolyte further includes auxiliary additives, which include at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds;

[0017] Based on the total mass of the non-aqueous electrolyte as 100%, the amount of the auxiliary additive is 0.01% to 30%.

[0018] Preferably, the cyclic sulfate compound is selected from vinyl sulfate, propylene sulfate, etc. Or at least one of vinyl methyl sulfate;

[0019] The sulfonyl lactone compound is selected from 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, or 1,3-propenesulfonyl lactone. At least one of them;

[0020] 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 the compound shown in structural formula 2.

[0021]

[0022] In structural formula 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;

[0023] The phosphate ester compound is selected from at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, or the compound shown in structural formula 3:

[0024]

[0025] In structural formula 3, R 31 R 32 R 32 Each is independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halohydrocarbon groups, and -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;

[0026] The borate ester compound is selected from at least one of tris(trimethylsilane)borate ester and tris(triethylsilane)borate ester;

[0027] The nitrile compounds include at least one of butadionitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptacyanide, octadionitrile, nonadionitrile, and sebaconitol.

[0028] Preferably, the non-aqueous organic solvent includes at least one of ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents, and sulfone solvents.

[0029] On the other hand, this application provides a secondary battery, including a positive electrode, a negative electrode, and any one of the above-mentioned non-aqueous electrolytes.

[0030] Preferably, the secondary battery is a lithium metal battery, a lithium-ion battery, or a sodium-ion battery.

[0031] The non-aqueous electrolyte provided in this application includes a compound shown in structural formula 1. During battery charging, it can undergo a reduction reaction at the negative electrode to open the ring and generate polyvalent anion radicals. These polyvalent anion radicals further react to generate polyvalent salts with higher molecular weights. The polyvalent salts form a regular network structure SEI film on the surface of the negative electrode. This SEI film has great flexibility and is not easily broken even at high temperatures. The stable SEI film helps improve the high-temperature cycle performance and high-temperature storage performance of the battery, extending the cycle life of the battery. It is speculated that this is because the compound shown in structural formula 1 can undergo a reduction reaction at the negative electrode during battery charging to open the ring and generate polyvalent anion radicals. These polyvalent anion radicals further react to form polyvalent salts with higher molecular weights. The polyvalent salts have greater flexibility and are not easily broken even at high temperatures. Good oxidation resistance means that the SEI film formed by the polyvalent salt on the negative electrode surface also has better oxidation resistance, which can slow down the oxidation process of the electrolyte and significantly improve the high-temperature cycle performance and high-temperature storage performance of lithium-ion batteries. On the other hand, since the compound shown in structural formula 1 has a double-ring structure with two carbon atoms, the structure is more stable. One side is a five-membered ring cyclic sulfate, and the other side is a five-membered ring cyclic carbonate. The sulfate group can form an interface film on the negative electrode surface, inhibiting the co-intercalation and reductive decomposition of solvent molecules on the negative electrode and improving the high-temperature performance of the battery. The carbonate group also participates in film formation and can effectively prevent further decomposition of the electrolyte. Therefore, a small amount of addition can change the cycle performance of the electrolyte and also has good flame retardant effect, which can significantly improve the flash point of the electrolyte. Detailed Implementation

[0032] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] This application provides a non-aqueous electrolyte, comprising an electrolyte salt, a non-aqueous organic solvent, and an additive, wherein the additive comprises a compound shown in structural formula 1:

[0034]

[0035] R1 and R2 are each independently selected from hydrogen atoms, halogen atoms, C1-C5 hydrocarbon groups, or C1-C5 haloalkyl groups. C1-C5 hydrocarbon groups can be alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, isopropyl, or isobutyl; alkenyl groups such as vinyl, propenyl, or butenyl; or alkynyl groups such as ethynyl, propynyl, or butynyl. Halogen atoms include at least one of F, Cl, Br, I, and At.

[0036] During battery charging, non-aqueous organic solvents are unstable at high temperatures and easily undergo reduction and decomposition on the negative electrode surface. Simultaneously, their accumulation at the negative electrode interface causes a continuous increase in battery impedance, damages the SEI film, and affects the battery's cycle performance and storage performance under high-temperature conditions. Through extensive research, the inventors discovered that adding the compound shown in Structural Formula 1 as an additive to the non-aqueous electrolyte allows it to undergo a reduction reaction at the negative electrode, generating multivalent anionic free radicals. These free radicals further react to form high-molecular-weight multivalent salts, which form a regular network-structured SEI film on the negative electrode surface. This SEI film exhibits significant flexibility, making it less prone to rupture even at high temperatures, and its impedance increase is relatively slow. This effectively reduces the decomposition of electrolyte solvents at the negative electrode, reduces gas generation, and thus improves the electrochemical performance of lithium-ion batteries under high-temperature conditions. Furthermore, the multivalent salts possess better oxidation resistance, slowing down the electrolyte oxidation process and significantly enhancing the high-temperature cycle performance and storage performance of lithium-ion batteries.

[0037] The compound shown in structural formula 1 has a sulfate ester group that can form a solid electrolyte interphase film on the surface of the battery electrode, inhibiting the co-intercalation and reductive decomposition of solvent molecules at the negative electrode, improving the cycle performance and high-temperature performance of lithium-ion batteries. The cyclic carbonate group can also participate in film formation, effectively preventing further decomposition of the electrolyte. A small amount of addition can change the cycle performance of the electrolyte, and it also has a good flame retardant effect, which can significantly improve the flash point of the electrolyte.

[0038] During battery charging and discharging, the addition of the compound shown in Structural Formula 1 to the non-aqueous electrolyte can induce an electrochemical reaction on the electrode surface and simultaneously achieve moderate cross-linking to form a relatively stable thin film structure, thereby improving the battery's electrical performance. The co-carbon five-membered cyclic ester compound shown in Structural Formula 1 helps lithium-ion batteries form a stable SEI film during charging and discharging, effectively improving the battery's high-temperature performance and power characteristics, enabling the prepared lithium-ion battery to maintain excellent electrochemical performance even under high-temperature conditions.

[0039] There are various methods for preparing the compound shown in structural formula 1. Those skilled in the art can know the preparation methods of the above-mentioned compound based on common general knowledge in the field. One method for preparing compound 1 is listed below. It should be noted that other reactants can also be used to prepare the compound shown in structural formula 1 of this application, and all of them are within the protection scope of this application.

[0040] The specific synthetic route for the reaction of ethylene dichlorocarbonate (DCEC) with fuming sulfuric acid to generate a co-carbon five-membered ring sulfuric acid is as follows:

[0041]

[0042] In some embodiments, the compound represented by structural formula 1 is selected from at least one of the following compounds:

[0043]

[0044]

[0045] In some embodiments, the mass percentage of the compound represented by structural formula 1 is 0.05% to 10% based on the total mass of the non-aqueous electrolyte (100%).

[0046] In some preferred embodiments, the mass percentage of the compound represented by structural formula 1 is 0.1% to 5% based on the total mass of the non-aqueous electrolyte (100%).

[0047] In specific embodiments, the mass percentage of the compound represented by structural formula 1 in the non-aqueous electrolyte can be 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%.

[0048] When the mass percentage of the compound shown in Structural Formula 1 is within the range of 0.05% to 10%, an electrochemical reaction can occur on the electrode surface, forming a structurally stable thin film. This effectively maintains the stability of the film formation on the electrode surface and improves battery performance. Taking lithium batteries as an example, adding the compound shown in Structural Formula 1 to the electrolyte within the above range can form a regular network structure and a highly flexible SEI film at the negative electrode interface. The SEI film does not rupture under high temperature conditions and can reduce the decomposition and oxidation reactions of the electrolyte solvent on the negative electrode, reduce gas generation, and improve the high-temperature storage performance of the battery. If the amount of the compound shown in Structural Formula 1 is too small, it cannot form a regular network structure SEI film at the negative electrode interface during battery charging, thus failing to significantly improve battery performance. If the amount of the compound shown in Structural Formula 1 is too large, the content of other additives in the electrolyte decreases, affecting the film formation reaction on the negative electrode surface. Furthermore, excessive decomposition products may also affect the function of other substances in the electrolyte.

[0049] In some embodiments, the concentration of electrolyte salt in the non-aqueous electrolyte is 0.1 mol / L to 8 mol / L; in some preferred embodiments, the concentration of electrolyte salt in the non-aqueous electrolyte is 0.5 mol / L to 2.5 mol / L.

[0050] In some embodiments, the electrolyte salt is selected from lithium salts or sodium salts.

[0051] In a preferred embodiment, the lithium salt is selected from 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 LiSO3F, LiTOP (lithium trioxane phosphate), LiDODFP (lithium difluorodioxane phosphate), LiOTFP (lithium tetrafluorooxane phosphate), and lower aliphatic carboxylic acid lithium salts.

[0052] In a preferred embodiment, the sodium salt is selected from at least one of NaPF6, NaClO4, NaAsF6, NaSbF6, NaPOF4, NaPO2F2, NaC4BO8, NaC2BF2O4, NaODFB, NaN(SO2C2F5)2, NaN(SO2CF3)(SO2C4F9)2, NaC(SO2CF3), and Na(C2F5)PF3.

[0053] In specific embodiments, the concentration of the electrolyte salt can be 0.5 mol / L, 1 mol / L, 1.2 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, 6 mol / L, 7 mol / L, or 8 mol / L.

[0054] In some embodiments, the non-aqueous electrolyte further includes auxiliary additives, which include at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, unsaturated phosphate compounds, borate ester compounds, and nitrile compounds;

[0055] Based on the total mass of the non-aqueous electrolyte as 100%, the amount of the auxiliary additive is 0.01% to 30%.

[0056] It should be noted that, unless otherwise specified, the amount of any one of the optional substances in the auxiliary additives added to the non-aqueous electrolyte is generally less than 10%, preferably 0.1-5%, and more preferably 0.1% to 3%. Specifically, the amount of any one of the optional substances in the auxiliary additives can be 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%.

[0057] In some preferred embodiments, the cyclic sulfate compound is selected from vinyl sulfate (DTD), propylene sulfate, etc. Or at least one of vinyl methyl sulfate;

[0058] The sulfonyl lactone compound is selected from at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, or 1,3-propenesulfonyl lactone (PS).

[0059] The cyclic carbonate compound is selected from at least one of propylene carbonate (PC), vinylene carbonate (VC), ethylene ethylene carbonate, methylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate, or fluoroethylene carbonate, or the compound shown in structural formula 2.

[0060]

[0061] In structural formula 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.

[0062] In some embodiments, the compound represented by structural formula 2 includes At least one of them.

[0063] The phosphate ester compound is selected from at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, or the compound shown in structural formula 3:

[0064]

[0065] In structural formula 3, R31 R 32 R 32 Each is independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halohydrocarbon groups, and -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.

[0066] In some embodiments, the compound represented by structural formula 3 may be 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.

[0067] The borate ester compound is selected from at least one of tris(trimethylsilane)borate ester and tris(triethylsilane)borate ester;

[0068] The nitrile compounds include at least one of butadionitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptacyanide, octadionitrile, nonadionitrile, and sebaconitol.

[0069] In the non-aqueous electrolyte, compared with single addition or combination of other existing additives, the compound shown in structural formula 1, when added together with the auxiliary additive, exhibits a significant synergistic effect in improving battery performance. This indicates that the compound shown in structural formula 1 and the auxiliary additive, when forming a film together on the electrode surface, can compensate for the film formation defects of single addition and obtain a more stable passivation film.

[0070] In other embodiments, the auxiliary additives also include other additives that can improve battery performance: for example, additives that improve battery safety performance, such as flame retardant additives like fluorophosphates and cyclophosphonitriles, or overcharge prevention additives like tert-amylbenzene and tert-butylbenzene.

[0071] In some embodiments, the solvent includes at least one of ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents, and sulfone solvents.

[0072] In some embodiments, the ether solvent includes cyclic ethers or chain ethers, preferably chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms. Specifically, the cyclic ether may include, but is not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF). The chain ether may include, but is not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Because chain ethers have high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred. An ether compound may be used alone or in any combination and ratio of two or more. There are no particular limitations on the amount of ether compounds added, and it can be arbitrary as long as it does not significantly impair the performance of the high-pressure lithium-ion battery of the present invention. Typically, the volume ratio is 1% or more, preferably 2% or more, and more preferably 3% or more when the non-aqueous solvent volume ratio is 100%. Furthermore, the volume ratio is typically 30% or less, preferably 25% or less, and more preferably 20% or less. When using two or more ether compounds in combination, the total amount of ether compounds should satisfy the above-mentioned range. When the amount of ether compounds added is within the above-mentioned preferred range, it is easy to ensure the improved ionic conductivity resulting from the increased lithium-ion dissociation degree and decreased viscosity of the chain ethers. In addition, when the negative electrode active material is a carbon material, the phenomenon of co-intercalation between the chain ethers and lithium ions can be suppressed, thus enabling the input / output characteristics and charge / discharge rate characteristics to reach an appropriate range.

[0073] In some embodiments, the nitrile solvent includes at least one of acetonitrile, glutaronitrile, and malononitrile.

[0074] In some embodiments, the carbonate solvent includes cyclic carbonates or chain carbonates. Cyclic carbonates include at least one selected from ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), and butylene carbonate (BC); chain carbonates include at least one selected from dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). The content of cyclic carbonates is not particularly limited and is arbitrary within a range that does not significantly impair the performance of the high-pressure lithium-ion battery of the present invention. However, when using only one type, its content is typically 3% or more, preferably 5% or more, by volume relative to the total amount of solvent in the non-aqueous electrolyte. By setting this range, a decrease in conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, making it easier to achieve good high-current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery. Furthermore, the upper limit is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less. By setting this range, the oxidation / reduction resistance of the non-aqueous electrolyte can be improved, thereby contributing to enhanced stability during high-temperature storage. The content of the chain carbonate is not particularly limited, but relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 15% or more by volume, preferably 20% or more, and more preferably 25% or more. Furthermore, it is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less. By keeping the chain carbonate content within the above range, it is easier to achieve an appropriate viscosity for the non-aqueous electrolyte, suppressing the decrease in ionic conductivity, and thus contributing to achieving a favorable range of output characteristics for the non-aqueous electrolyte battery. When using two or more chain carbonates in combination, it is sufficient to ensure that the total amount of chain carbonate meets the above range.

[0075] In some embodiments, fluorine-containing chain carbonates (hereinafter referred to as "fluorinated chain carbonates") are also preferably used. There is no particular limitation on the number of fluorine atoms in a fluorinated chain carbonate as long as it is 1 or more, but it is generally 6 or less, preferably 4 or less. When a fluorinated chain carbonate has multiple fluorine atoms, these fluorine atoms can be bonded to the same carbon atom or to different carbon atoms. Examples of fluorinated chain carbonates include dimethyl fluorinated carbonate derivatives, methyl ethyl fluorinated carbonate derivatives, and diethyl fluorinated carbonate derivatives.

[0076] Carboxylic acid ester solvents include cyclic carboxylic acid esters and / or chain carbonates. Examples of cyclic carboxylic acid esters include at least one of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonates include at least one of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), and butyl propionate.

[0077] In some embodiments, the sulfone solvent includes cyclic sulfones and chain sulfones, but preferably, in the case of cyclic sulfones, it is typically a compound with 3 to 6 carbon atoms, more preferably 3 to 5 carbon atoms, and in the case of chain sulfones, it is typically a compound with 2 to 6 carbon atoms, more preferably 2 to 5 carbon atoms. There are no particular limitations on the amount of sulfone solvent added, and it is arbitrary within a range that does not significantly impair the performance of the high-pressure lithium-ion battery of the present invention. Relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 0.3% or more by volume, preferably 0.5% or more by volume, more preferably 1% or more by volume, and typically 40% or less by volume, preferably 35% or less by volume, more preferably 30% or less by volume. When using two or more sulfone solvents in combination, the total amount of sulfone solvent should satisfy the above range. When the amount of sulfone solvent added is within the above range, an electrolyte with excellent high-temperature storage stability is tended to be obtained.

[0078] In a preferred embodiment, the solvent is a mixture of cyclic carbonates and chain carbonates.

[0079] Another embodiment of the present invention provides a secondary battery, including a positive electrode, a negative electrode, and a non-aqueous electrolyte as described above.

[0080] Because the secondary battery uses the non-aqueous electrolyte described above, it can form a high-performance passivation film on the positive and negative electrodes, thereby effectively improving the battery's high-temperature storage performance and high-temperature cycle performance, and enhancing the battery's power characteristics.

[0081] In a preferred embodiment, the secondary battery is a lithium metal battery, a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, etc.

[0082] In some embodiments, the positive electrode includes a positive electrode material layer, which includes a positive electrode active material. There are no particular limitations on the type of positive electrode active material, as long as it is a positive electrode active material or a conversion type positive electrode material that can reversibly insert / deintercalate metal ions (such as lithium ions or sodium ions).

[0083] In a preferred embodiment, the secondary battery is a lithium-ion battery. The type and content of the positive electrode active material of the lithium-ion battery are not limited and can be selected according to actual needs. The positive electrode active material can be selected from LiFe... 1-x’ M' x’ PO4, LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-zAt 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, 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. The positive electrode active material may also be selected from one or more of sulfides, selenides, and halides.

[0084] Preferably, the positive electrode active material may be selected from LiCoO2, LiNiO2, LiMnO2, LiNi x Co y Mn z O2, LiNi 1- a Co a O2, LiNi 1-a Mn a O2, LiCo 1-a Mn a O2, LiNi x1 Co y1 Mn z1 O4, LiMn2O4, LiMn 2-b Ni b O4, LiMn 2-b Co b O4, Li2MnO4, LiV3O8, LiCoPO4, LiFePO4, etc., wherein 0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1, 0 < a < 1, 0 < x1 < 2, 0 < y1 < 2, 0 < z1 < 2, x1 + y1 + z1 = 2, 0 < b < 2. The positive electrode active material may also be selected from one or more of sulfides, selenides, and halides.

[0085] In a preferred embodiment, the secondary battery is a sodium-ion battery. The type and content of the positive electrode active material of the sodium-ion battery are not limited and can be selected according to actual needs. Preferably, the positive electrode active material can be selected from one or more of metallic sodium, carbon materials, alloy materials, over-plated metal oxides, over-plated metal sulfides, phosphorus-based materials, titanate materials, Prussian blue-like materials, sodium-containing layered oxides, sodium-containing sulfate compounds, and sodium-containing phosphate compounds. The carbon material can be selected from one or more of graphite, soft carbon, and hard carbon. The alloy material can be selected from an alloy material composed of at least two of Si, Ge, Sn, Pb, and Sb. The alloy material can also be selected from an alloy material composed of at least one of Si, Ge, Sn, Pb, and Sb with C. The chemical formula of the over-plated metal oxide and the over-plated metal sulfide is M1. x N y M1 can be selected from one or more of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V, and N is selected from O or S. More preferably, the transition metal oxide is NaNi. e Fe f Mn p O2 (e+f+p=1, 0≤e≤1, 0≤f≤1, 0≤p≤1) or NaNi e Co f Mn p O2 (e+f+p=1, 0≤m≤1, 0≤f≤1, 0≤p≤1), wherein the phosphorus-based material may be selected from one or more of red phosphorus, white phosphorus, and black phosphorus. The chemical formula of the phosphate is Na3(MO). 1-g PO4)2F 1+2g The phosphate has the following chemical formulas: 0 ≤ g ≤ 1, M is selected from at least one of Al, V, Ge, Fe, and Ga, more preferably, the phosphate is Na3(VPO4)2F3 or Na3(VOPO4)2F; and / or the phosphate has the chemical formula Na2MPO4F, M is selected from at least one of Fe and Mn, more preferably, the phosphate is Na2FePO4F or Na2MnPO4F. The sulfate has the chemical formula Na2M(SO4)2·2H2O, M can be selected from at least one of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V. The titanate material can be selected from Na2Ti3O7 or Na2Ti6O. 13 Na4Ti5O 12 Li4Ti5O 12 One or more of NaTi2(PO4)3, wherein the molecular formula of the Prussian blue material is Na x M[M′(CN)6] y·zH2O, where M is a transition metal, M' is a transition metal, 0 < x ≤ 2, 0.8 ≤ y < 1, 0 < z ≤ 20. More preferably, the Prussian blue-based material is Na x Mn[Fe(CN)6] y ·nH2O (0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 10) or Na x Fe[Fe(CN)6] y ·nH2O (0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 10).

[0086] 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.

[0087] The positive electrode current collector is selected from metal materials capable of conducting electrons. Preferably, the positive electrode current collector includes at least one of aluminum, nickel, tin, copper, and stainless steel.

[0088] In some embodiments, the positive electrode 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.

[0089] The positive electrode binder includes at least one of thermoplastic resins such as polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene, copolymers of tetrafluoroethylene - hexafluoropropylene, copolymers of tetrafluoroethylene - perfluoroalkyl vinyl ether, copolymers of ethylene - tetrafluoroethylene, copolymers of vinylidene fluoride - tetrafluoroethylene, copolymers of vinylidene fluoride - trifluoroethylene, copolymers of vinylidene fluoride - trichloroethylene, copolymers of vinylidene fluoride - fluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; sodium carboxymethyl cellulose; and styrene - butadiene rubber.

[0090] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.

[0091] In some embodiments, when the secondary battery is a lithium-ion battery, the negative electrode includes a negative electrode active material, which includes at least one of carbon-based, silicon-based, tin-based, lithium-based, sodium-based, potassium-based, magnesium-based, zinc-based, and aluminum-based negative electrodes. The carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.; the silicon-based negative electrode may include silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials, etc.; the tin-based negative electrode may include tin, tin-carbon, tin oxide, and tin metal compounds; and the lithium-based negative electrode may include metallic lithium or lithium alloys. Specifically, the lithium alloy may be at least one of lithium-silicon alloy, lithium-sodium alloy, lithium-potassium alloy, lithium-aluminum alloy, lithium-tin alloy, and lithium-indium alloy.

[0092] In a preferred embodiment, when the secondary battery is a sodium-ion battery, its negative electrode active material includes 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.

[0093] 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 negative electrode current collector is selected from a metallic material that can conduct electrons. Preferably, the negative electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0094] 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, the negative electrode binder, and the negative electrode conductive agent are blended to obtain the negative electrode material layer. The negative electrode binder and the negative electrode conductive agent can be the same as the positive electrode binder and the positive electrode conductive agent, respectively, and will not be described in detail here.

[0095] In some embodiments, the secondary battery further includes a separator located between the positive electrode and the negative electrode.

[0096] The diaphragm can be a conventional diaphragm, such as a polymer diaphragm, non-woven fabric, 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.

[0097] The present invention will be further illustrated by the following examples.

[0098] The compounds involved in the following examples and comparative examples are shown in Table 1 below:

[0099] Table 1

[0100]

[0101] Example 1

[0102] This embodiment uses the preparation of a lithium-ion battery as an example to illustrate the present invention, including the following operation steps:

[0103] 1) Preparation of non-aqueous electrolyte:

[0104] Ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EC) were mixed in a mass ratio of EC:DEC:EC = 1:1:1. Then, lithium hexafluorophosphate (LiPF6) was added to a molar concentration of 1 mol / L, along with the compound and auxiliary additives shown in structural formula 1. The types and contents of the compound and auxiliary additives shown in structural formula 1 in the non-aqueous electrolyte are shown in Table 2, based on the total weight of the non-aqueous electrolyte as 100%.

[0105] 2) Preparation of the positive electrode:

[0106] The positive electrode active material, lithium nickel cobalt manganese oxide (LiNiO), was mixed in a mass ratio of 93:4:3. 0.5 Co 0.2 Mn 0.3 O2, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) are dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The slurry is uniformly coated on both sides of an aluminum foil, dried, calendered, and vacuum dried, and then aluminum leads are welded on using an ultrasonic welder to obtain the positive electrode plate. The thickness of the electrode plate is between 120-150 μm.

[0107] 3) Preparation of the negative electrode:

[0108] 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. The slurry was coated on both sides of a copper 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 between 120-150 μm.

[0109] 4) Cell fabrication:

[0110] A three-layer separator with a thickness of 20 μm is placed between the positive electrode and the negative electrode. Then, the sandwich structure composed of the positive electrode, the negative electrode and the separator is wound up. The wound body is then flattened and placed in an aluminum foil packaging bag. It is then vacuum baked at 75°C for 48 hours to obtain the battery cell to be injected with electrolyte.

[0111] 5) Electrolyte injection and formation of the battery cell:

[0112] In a glove box where the dew point is controlled below -40°C, the electrolyte prepared above is injected into the battery cell, vacuum sealed, and left to stand for 24 hours.

[0113] 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.

[0114] Examples 2-18

[0115] Examples 2-18 illustrate the lithium-ion battery and its preparation method disclosed in this invention, including most of the operational steps in Example 1, with the following differences:

[0116] The additives and their contents shown in Examples 2 to 18 of Table 2 or Table 3 are used.

[0117] Comparative Examples 1-7

[0118] Comparative Examples 1-7 are used to illustrate the lithium-ion battery and its preparation method disclosed in this invention, including most of the operation steps in Example 1, with the following differences:

[0119] The additives and their contents shown in Comparative Examples 1 to 7 in Table 2 were used.

[0120] Performance testing

[0121] (1) High-temperature storage performance test

[0122] The formed lithium-ion battery was charged at room temperature with a constant current of 1C to 4.2V, then charged with constant current and constant voltage to the cutoff current of 0.05C. It was then discharged at a constant current of 1C to 3.0V. The initial discharge capacity D1, initial battery volume V1, and initial impedance F1 were measured. After being fully charged, the battery was stored at 60℃ for 30 days, then discharged at 1C to 3V. The retention capacity D2, recovery capacity D3, impedance F2 after storage, and battery volume V2 after storage were measured. The calculation formulas are as follows:

[0123] Battery capacity retention rate (%) = Retained capacity D2 / Initial capacity D1 × 100%;

[0124] Battery capacity recovery rate (%) = Recovered capacity D3 / Initial capacity D1 × 100%;

[0125] Volume expansion rate (%) = (Battery volume after storage V2 - Initial battery volume V1) / Initial battery volume V1 × 100%;

[0126] Internal resistance growth rate (%) = (storage impedance F2 - initial impedance F1) / initial impedance F1 × 100%.

[0127] (2) High-temperature cycling performance test

[0128] The lithium-ion battery was placed in an oven at a constant temperature of 45°C and charged at a constant current of 1C to 4.2V. Then it was charged at a constant voltage until the current dropped to 0.02C. Finally, it was discharged at a constant current of 1C to 3.0V. This cycle was repeated, and the discharge capacity of the first week and the discharge capacity of the last week were recorded.

[0129] Calculate the capacity retention rate during the cycle using the following formula:

[0130] Battery capacity retention rate (%) = Discharge capacity in the last week / Discharge capacity in the first week × 100%.

[0131] The electrolyte parameters and test data for Examples 1-13 and Comparative Examples 1-7 are shown in Table 2.

[0132] Table 2

[0133]

[0134]

[0135] The test results from Examples 1-9 and Comparative Example 1 show that, compared to the non-aqueous electrolyte without the addition of the compound shown in Structural Formula 1, adding the compound shown in Structural Formula 1 as an additive to the non-aqueous electrolyte effectively improves the high-temperature cycle capacity retention, high-temperature storage capacity retention, capacity recovery rate, volume expansion rate, and internal resistance growth rate of the lithium-ion battery. This indicates that the passivation film formed by the decomposition of the compound shown in Structural Formula 1 on the positive and negative electrode surfaces has high high-temperature stability, improving the performance stability of the positive and negative electrode materials during long-term cycling and enhancing the cycle performance and storage performance of the lithium-ion battery at high temperatures. The test results from Examples 1-9 show that, with the increase of the content of the compound shown in Structural Formula 1, the high-temperature storage performance and high-temperature cycle performance of the lithium-ion battery first increase and then decrease. In particular, when the content of the compound is 0.5%-5.0%, the lithium-ion battery exhibits the best overall performance. This indicates that during the charge-discharge cycle of the lithium-ion battery, when the content of the compound shown in Structural Formula 1 in the electrolyte is 0.5%-5.0%, the formed SEI film is regular and of moderate thickness, exhibiting better stability.

[0136] A comparison of Examples 4 and Comparative Examples 2-5 shows that, compared to traditional vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propanesulfonate lactone (PS), and tris(trimethylsilane) phosphate (TMSP), using the compound shown in Structural Formula 1 provided in this application as an additive can significantly improve the storage performance of lithium-ion batteries at high temperatures. This indicates that the passivation film formed by the co-carbon five-membered cyclic ester compound shown in Structural Formula 1 has superior high-temperature stability and is not easily damaged under high-temperature conditions. A comparison of Examples 4 and 10 shows that the auxiliary additive and the compound shown in Structural Formula 1 have a synergistic effect in improving the high-temperature storage and cycle performance of the battery.

[0137] A comparison of Examples 1-9 and Comparative Examples 6-7 shows that when the content of the compound shown in Structural Formula 1 is too low, it is difficult to form a complete passivation film on the positive and negative electrode surfaces, and the improvement in lithium-ion battery performance is not significant. When the content of the compound shown in Structural Formula 1 is higher than 10%, the high-temperature storage performance of the battery decreases, the rate of increase in battery internal resistance increases, the thickness expansion rate increases, and the high-temperature cycle performance is poor. It is speculated that the SEI film formed by the compound shown in Structural Formula 1 with excessive content is thicker, which increases the cross-sectional impedance of the positive and negative electrodes and degrades the high-temperature performance of the battery.

[0138] The test results of Examples 4, 10-13 show that the combination of vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propanesulfonate lactone (PS), or tris(trimethylsilane) phosphate (TMSP) with the compound shown in Structural Formula 1 can significantly improve the high-temperature cycle performance of lithium-ion batteries. It is speculated that this is because VC, DTD, PS, TMSP and the compound shown in Structural Formula 1 jointly participate in the formation of passivation films on the positive and negative electrode surfaces, which is beneficial to improving the quality of the passivation film.

[0139] The electrolyte parameters and electrical performance data for Examples 4 and 14-18 are shown in Table 3.

[0140] Table 3

[0141]

[0142] As can be seen from the test results of Examples 4 and 14-18, when different compounds of structural formula 1 are used as additives for non-aqueous electrolytes, the high-temperature storage performance and high-temperature cycle performance of lithium-ion batteries are improved to a certain extent.

[0143] Example 19

[0144] Example 19 illustrates the present invention using the preparation of a sodium-ion battery as an example, including the following operational steps:

[0145] 1) Preparation of non-aqueous electrolyte:

[0146] Ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed in a mass ratio of EC:DEC:EMC = 1:1:1. Sodium hexafluorophosphate (NaPF6) was then added to a molar concentration of 1 mol / L. Additives were also added. The content of the compound represented by structural formula 1 in the non-aqueous electrolyte is shown in Table 4, based on the total weight of the non-aqueous electrolyte as 100%.

[0147] 2) Preparation of the positive electrode:

[0148] The positive electrode active material Na3V2(PO4)3, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 94:3:3, and then dispersed in N-methyl-2-pyrrolidone (NMP) to obtain the positive electrode slurry. The slurry is uniformly coated on both sides of an aluminum foil, dried, calendered, and vacuum dried, and then aluminum or nickel leads are welded on using an ultrasonic welder to obtain the positive electrode sheet with a thickness between 80-200 μm.

[0149] 3) Preparation of the negative electrode:

[0150] The negative electrode active materials, spherical hard carbon, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) are mixed in a mass ratio of 97:1:1:1, and then dispersed in deionized water to obtain a negative electrode slurry. The slurry is coated on both sides of an aluminum foil, dried, calendered, and vacuum dried, and then aluminum or nickel leads are welded on using an ultrasonic welder to obtain a negative electrode sheet with a thickness between 80-300 μm.

[0151] 4) The positive electrode, 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 fixtures, resealed, and tested for capacity to complete the preparation of sodium-ion batteries.

[0152] Examples 19-36

[0153] Examples 19-36 illustrate the sodium-ion battery and its preparation method disclosed in this invention, and include most of the operational steps in Example 18, except that:

[0154] The additives and their contents shown in Examples 19-31 in Tables 4 and 5 were used.

[0155] Comparative Examples 8-14

[0156] Comparative Examples 8-14 are used to illustrate the sodium-ion battery and its preparation method disclosed in this invention, including most of the operation steps in Example 19, with the following differences:

[0157] The additives and their contents shown in Comparative Examples 8-14 in Table 4 were used.

[0158] Performance testing

[0159] The sodium-ion batteries prepared above were subjected to the following performance tests:

[0160] (1) High-temperature storage performance test

[0161] The sodium-ion battery, after formation, was charged at room temperature with a constant current of 0.5C to 4.0V, then charged at a constant voltage until the current dropped to 0.03C. It was then discharged at a constant current of 1C to 1.5V. The initial discharge capacity C1, initial battery volume V'1, and initial impedance F'1 were measured. The battery was then fully charged and stored at 60℃ for 30 days. Afterward, it was discharged at 1C to 3V, and the retention capacity C2, recovery capacity C3, impedance F'2 after storage, and battery volume V'2 after storage were measured. The calculation formulas are as follows:

[0162] Battery capacity retention rate (%) = Retained capacity C2 / Initial capacity C1 × 100%;

[0163] Battery capacity recovery rate (%) = Recovered capacity C3 / Initial capacity C1 × 100%;

[0164] Volume expansion rate (%) = (Battery volume after storage V'2 - Initial battery volume V'1) / Initial battery volume V'1 × 100%;

[0165] Internal resistance growth rate (%) = (storage impedance F'2 - initial impedance F'1) / initial impedance F'1 × 100%.

[0166] (2) High-temperature cycling performance test

[0167] After formation, the battery was left to stand at 45°C for 2 hours, then charged at a constant current rate of 0.5C to 4.0V, then charged at a constant voltage rate to 0.03C, and then discharged at a constant current rate of 1C to 1.5V, for 200 cycles.

[0168] The initial discharge capacity C4, the discharge capacity C5 after 200 cycles, and the coulombic efficiency E of the battery were measured.

[0169] Battery capacity retention rate (%) = Discharge capacity C5 / Initial capacity C4 × 100%.

[0170] Electrolyte parameters and electrical performance data for Examples 19-31 and Comparative Examples 8-14 are shown in Table 4.

[0171] Table 4

[0172]

[0173]

[0174] The test results from Examples 19-27 and Comparative Example 8 show that, similar to the role of the compound shown in Structural Formula 1 in lithium-ion batteries, adding the compound shown in Structural Formula 1 to the non-aqueous electrolyte of sodium-ion batteries can also improve the high-temperature cycle capacity retention, high-temperature storage capacity retention, capacity recovery rate, volume expansion rate, and impedance growth rate of sodium-ion batteries. This indicates that the passivation film formed by the decomposition of the compound shown in Structural Formula 1 on the positive and negative electrode surfaces has high high-temperature stability, improving the performance stability of the positive and negative electrode materials during long-term cycling, and enhancing the cycle performance and storage performance of sodium-ion batteries at high temperatures. The test results from Examples 19-27 show that as the content of the compound shown in Structural Formula 1 increases, the high-temperature storage performance and high-temperature cycle performance of sodium-ion batteries first increase and then decrease. In particular, when the content of the compound is 0.5% to 5%, the sodium-ion battery exhibits the best overall performance. This indicates that during the charge-discharge cycle of sodium-ion batteries, when the content of the compound shown in Structural Formula 1 in the electrolyte is 0.5% to 5%, it can ensure that the formed SEI film is regular and of moderate thickness, with better stability.

[0175] As can be seen from the test results of Examples 22 and Comparative Examples 9-12, compared with conventional film-forming additives and their combinations, such as vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propane sulfonate lactone (PS) or fluoroethylene carbonate (FEC), using the compound shown in Structural Formula 1 provided in this application as an additive can more significantly improve the storage performance and cycle performance of sodium-ion batteries at high temperatures, and reduce the battery expansion rate and internal resistance growth rate. This indicates that compared with conventional film-forming additives, the passivation film formed by the compound shown in Structural Formula 1 has better high-temperature stability.

[0176] The test results of Examples 20 and 28-31 show that using vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propanesulfonate lactone (PS), or fluoroethylene carbonate (FEC) in combination with the compound shown in Structural Formula 1 can significantly improve the high-temperature cycle performance of sodium-ion batteries. It is speculated that this is because VC, DTD, PS, or FEC, together with the compound shown in Structural Formula 1, participate in the formation of passivation films on the positive and negative electrode surfaces, which is beneficial to improving the quality of the passivation film.

[0177] The electrolyte parameters and electrical performance data for Examples 22 and 32-36 are shown in Table 5.

[0178] Table 5

[0179]

[0180] As shown in Table 5, the high-temperature storage performance and cycle performance of the batteries were similar even though the types of compounds represented by structural formula 1 were added to the electrolytes in Examples 22 and 32-36 were different. This indicates that when different compounds represented by structural formula 1 are added to the electrolyte as additives, a regular network structure SEI film can be formed on the surface of the negative electrode. Even under high temperature conditions, the SEI film is not easy to break, which improves the high-temperature storage performance and high-temperature cycle performance of the battery. It also reduces the decomposition of the electrolyte on the surface of the negative electrode, reduces gas generation, reduces the thickness expansion rate during high-temperature storage, and the battery has good high-temperature adaptability.

[0181] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nonaqueous electrolyte, characterized by comprising: The non-aqueous electrolyte comprises an electrolyte salt, a non-aqueous organic solvent and an additive, wherein the additive comprises a compound shown in structural formula 1: Structural formula 1 R1, R2 are each independently selected from a hydrogen atom, a halogen atom, a C1-C5 hydrocarbon group or a C1-C5 halogenated hydrocarbon group; The nonaqueous electrolyte further includes an auxiliary additive including a cyclic sulfate compound selected from at least one of vinyl sulfate, propylene sulfate, , , , , or vinyl methyl sulfate.

2. The nonaqueous electrolyte according to claim 1, characterized by The compound shown in structural formula 1 is selected from at least one of the following compounds: Compound 10.

3. The nonaqueous electrolyte according to claim 1, characterized by The mass percentage of the compound shown in structural formula 1 is 0.05% to 10% based on the total mass of the non-aqueous electrolyte.

4. The nonaqueous electrolyte according to claim 1 or 3, characterized by The mass percentage of the compound shown in structural formula 1 is 0.1% to 5% based on the total mass of the non-aqueous electrolyte.

5. The nonaqueous electrolyte according to claim 1, wherein The concentration of the electrolyte salt in the non-aqueous electrolyte is 0.1 mol / L to 8 mol / L.

6. The nonaqueous electrolyte according to claim 1, wherein The electrolyte salt is selected from a lithium salt, 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 , LiSO3F, LiTOP (lithium trioxalate phosphate), LiDODFP (lithium difluorodioxalate phosphate), LiOTFP (lithium tetrafluorooxalate phosphate), and a lithium salt of a lower aliphatic carboxylic acid.

7. The nonaqueous electrolyte according to claim 1, wherein The electrolyte salt is selected from a sodium salt, and the sodium salt is selected from at least one of NaPF6, NaClO4, NaAsF6, NaSbF6, NaPOF4, NaPO2F2, NaC4BO8, NaC2BF2O4, NaODFB, NaN(SO2C2F5)2, NaN(SO2CF3)(SO2C4F9)2, NaC(SO2CF3) and Na(C2F5)PF3.

8. The nonaqueous electrolyte according to claim 1, wherein The auxiliary additive further comprises at least one of a sulfonic acid lactone compound, a cyclic carbonate compound, a phosphate compound, a borate compound and a nitrile compound; The auxiliary additive is added in an amount of 0.01% to 30% based on the total mass of the non-aqueous electrolyte.

9. The nonaqueous electrolyte according to claim 8, wherein the sulfolane compound is selected from at least one of 1,3-propane sulfolane, 1,4-butane sulfolane or 1,3-propene sulfolane, ​ The cyclic carbonate compound is selected from at least one of vinylene carbonate, vinyl ethylene carbonate, methylene vinyl carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate or a compound shown in structural formula 2: Structural formula 2 In the structural formula 2, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 are each independently selected from one of a hydrogen atom, a halogen atom, a C1-C5 group; The phosphate compound is selected from at least one of tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite or a compound shown in structural formula 3: Structural formula 3 R 31 , R 32 , R 32 are each independently selected from the group consisting of C1-C5 saturated hydrocarbon group, unsaturated hydrocarbon group, halogenated hydrocarbon group, -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 which is an unsaturated hydrocarbon group; The borate compound is selected from at least one of tris(trimethylsilyl) borate and tris(triethylsilyl) borate. The nitrile compound comprises at least one of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetristitnile, adiponitrile, pimelonitrile, suberonitrile, azelonitrile and sebonitrile.

10. The nonaqueous electrolyte according to claim 1, wherein The non-aqueous organic solvent comprises at least one of an ether solvent, a nitrile solvent, a carbonate solvent, a carboxylic acid ester solvent and a sulfone solvent.

11. A secondary battery characterized by comprising: The non-aqueous electrolyte comprises a positive electrode, a negative electrode and the non-aqueous electrolyte according to any one of claims 1 to 10.

12. The secondary battery according to claim 11, characterized by The secondary battery is a lithium metal battery, a lithium ion battery, a lithium sulfur battery or a sodium ion battery.

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