Electrolyte, electrolytic solution, and secondary battery

Abstract

The application relates to the field of electrochemistry, and provides an electrolyte, an electrolyte solution and a secondary battery. The electrolyte comprises at least one of a compound shown in formula 1, a compound shown in formula 2 or a compound shown in formula 3, wherein X, Y and Z are alkali metal elements. The electrolyte solution comprises the electrolyte provided by the application, is beneficial to improving the oxidation resistance, thermal stability and flame retardant performance of the electrolyte solution, thereby improving the cycle life, high-temperature cycle performance and high-temperature storage performance of the secondary battery, and is beneficial to improving the flame retardant performance of the secondary battery.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to an electrolyte, an electrolyte solution, and a secondary battery. Background Technology

[0002] Current secondary batteries (such as lithium-ion batteries and sodium-ion batteries) are developing towards higher energy density, longer cycle life, higher charge / discharge rates, and wider operating temperature ranges. Traditional electrolyte systems using anions (such as PF6) are increasingly adopting alternatives. - BF4 - ClO4 - These secondary batteries (such as those with poor thermodynamic stability, electrochemical window, compatibility of positive and negative electrode materials, and sensitivity to moisture) have significant shortcomings, which have become one of the key bottlenecks restricting further improvement of their performance.

[0003] The intrinsic properties of electrolyte anions (such as anionic structure, delocalization of negative charge, HOMO and LUMO energy levels, thermodynamic stability, and hydrolytic stability) profoundly affect the electrolyte's conductivity, ion transport number, electrochemical window, and compatibility with positive and negative electrode materials. Therefore, developing novel anionic electrolytes with large anionic volume, high charge delocalization, low coordination ability, high oxidation resistance and thermal stability, and good flame retardant properties has become a research focus. Summary of the Invention

[0004] The purpose of this application is to provide an electrolyte, an electrolyte solution, and a secondary battery to improve the oxidation resistance, thermal stability, and flame retardancy of the electrolyte, thereby improving the cycle life, high-temperature cycle performance, high-temperature storage performance, and flame retardant properties of the secondary battery. The specific technical solution is as follows:

[0005] A first aspect of this application provides an electrolyte comprising at least one of the compounds shown in Formula 1, Formula 2, or Formula 3:

[0006] , , ;

[0007] Among them, X, Y, and Z are alkali metal elements.

[0008] In some embodiments of this application, X, Y, and Z are selected from any one of Li, Na, K, Rb, and Cs.

[0009] In some embodiments of this application, the compound represented by Formula 1 is selected from at least one of the following compounds:

[0010] , ;

[0011] The compound represented by Formula 2 is selected from at least one of the following compounds:

[0012] , ;

[0013] The compound represented by Formula 3 is selected from at least one of the following compounds:

[0014] , .

[0015] A second aspect of this application provides an electrolyte comprising a non-aqueous organic solvent, a solute, and the electrolyte provided in the first aspect of this application.

[0016] In some embodiments of this application, the mass percentage of the electrolyte is 0.01% to 10% based on the mass of the electrolyte; preferably 0.1% to 8%.

[0017] In some embodiments of this application, the solute is selected from lithium salts or sodium salts. The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethyl)sulfonylimide, lithium bis(oxalate-borate), lithium difluorobis(oxalate-borate), lithium difluorobis(oxalate-borate), lithium difluorobis(oxalate-borate), lithium tetrafluorobis(oxalate-borate), and lithium 4,5-dicyano-2-trifluoromethyl-imidazolium. The sodium salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(oxalate-borate), sodium difluorobis(oxalate-borate), sodium difluorobis(oxalate-borate), sodium tetrafluorobis(oxalate-borate), and sodium 4,5-dicyano-2-trifluoromethyl-imidazolium. The mass percentage of the solute is 5% to 20% based on the mass of the electrolyte.

[0018] In some embodiments of this application, the solute includes lithium hexafluorophosphate, and the mass percentage of lithium hexafluorophosphate is 5% to 20% based on the mass of the electrolyte; or, the solute includes sodium hexafluorophosphate, and the mass percentage of sodium hexafluorophosphate is 5% to 20% based on the mass of the electrolyte.

[0019] In some embodiments of this application, the non-aqueous organic solvent is selected from at least one of carbonate solvents and carboxylic acid ester solvents; the carbonate solvent is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate, bis(2,2,2)-trifluoroethyl carbonate, 2,2,3,3-tetrafluoropropyl methyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and 3,3,3-trifluoropropylene carbonate; the carboxylic acid ester solvent is selected from methyl formate, ethyl formate, and butyl formate. The following are at least one of the following: methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, methyl valerate, ethyl valerate, propyl valerate, butyl valerate, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, β-propiolactone, β-butyrolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, 2-fluoro-1,4-butyrolactone, 3-fluoro-1,4-butyrolactone, and 4-fluoro-1,4-butyrolactone.

[0020] The third aspect of this application provides a secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte provided in the second aspect of this application.

[0021] The beneficial effects of this application are:

[0022] This application provides an electrolyte, an electrolyte solution, and a secondary battery. The electrolyte includes at least one of the compounds shown in Formula 1, Formula 2, or Formula 3, wherein X, Y, and Z are alkali metal elements. The electrolyte solution includes the electrolyte provided in this application, which is beneficial for improving the oxidation resistance, thermal stability, and flame retardant properties of the electrolyte solution, thereby improving the cycle life, high-temperature cycle performance, and high-temperature storage performance of the secondary battery, and also beneficial for improving the flame retardant properties of the secondary battery.

[0023] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these accompanying drawings.

[0025] Figure 1 The nuclear magnetic resonance F-spectrum of the compound of formula 1-1 prepared in Example 1;

[0026] Figure 2The nuclear magnetic resonance F-spectrum of the compound of formula 2-1 prepared in Example 2;

[0027] Figure 3 The nuclear magnetic resonance F-spectrum of the compound of formula 3-1 prepared in Example 3;

[0028] Figure 4 The nuclear magnetic resonance F-spectrum of the compounds of formula 1-2 prepared in Example 12. Detailed Implementation

[0029] The technical solutions of this application will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0030] A first aspect of this application provides an electrolyte comprising at least one of the compounds shown in Formula 1, Formula 2, or Formula 3:

[0031] , , ;

[0032] Among them, X, Y, and Z are alkali metal elements.

[0033] Research has found that the electrolyte structure provided in this application simultaneously contains a phosphate structure, a fluorinated phenyl structure, and a boron-containing structure. Firstly, this novel anionic structure can generate a stable and uniform negative electrode interface film containing phosphate, boron (BO), and boron (BF) on the negative electrode surface, effectively inhibiting electrolyte decomposition on the negative electrode surface and improving the cycle life of the secondary battery. Secondly, the perfluorophenyl structure can enhance the electrolyte's oxidation resistance and construct a high-voltage resistant interface protective film. The benzene ring provides chemical stability, and the strongly electron-withdrawing fluorine atoms can further reduce the electron cloud density of the benzene ring, greatly enhancing the oxidation resistance of the entire anionic portion, thereby increasing the electrolyte's oxidation potential and improving its thermal stability. Simultaneously, the fluorinated phenyl structure can oxidize and decompose on the positive electrode surface, forming a stable positive electrode interface film rich in LiF, protecting the positive electrode material, reducing transition metal ion dissolution and structural collapse, thereby improving the high-temperature storage performance and high-temperature cycle performance of the secondary battery. More importantly, the electrolyte provided in this application contains phosphoric acid, fluorinated phenyl, and boron-containing structures, which can improve the flame retardant performance of the secondary battery. The phosphoric acid structure has a strong flame retardant effect; when the internal temperature of the battery rises or an abnormality occurs, the phosphoric acid structure can capture hydrogen free radicals, interrupt the chain reaction, and effectively prevent the battery from igniting. Furthermore, the fluorinated phenyl structure has strong electron delocalization properties, which can bind to free radicals generated during electrolyte decomposition, reducing the reactivity of these free radicals and further improving the flame retardant performance of the secondary battery and enhancing battery safety. In this application, "high temperature" refers to a temperature greater than or equal to 45°C.

[0034] In some embodiments of this application, X, Y, and Z are selected from any one of Li, Na, K, Rb, and Cs.

[0035] In some embodiments of this application, the compound represented by Formula 1 is selected from at least one of the following compounds:

[0036] , ;

[0037] The compound shown in Formula 2 is selected from at least one of the following compounds:

[0038] , ;

[0039] The compound shown in Formula 3 is selected from at least one of the following compounds:

[0040] , .

[0041] By selecting electrolytes within the aforementioned range, it is beneficial to further improve the electrolyte's oxidation resistance, thermal stability, and flame retardancy, thereby enhancing the cycle life, high-temperature cycle performance, high-temperature storage performance, and flame retardancy of the secondary battery.

[0042] This application does not impose any particular limitation on the preparation methods of the compounds shown in Formula 1, Formula 2, and Formula 3. For example, the preparation methods of the compounds shown in Formula 1, Formula 2, and Formula 3 may include, but are not limited to, the following steps: adding an alkali metal-containing phosphate (e.g., Li3PO4) and tris(pentafluorophenyl)borane as reactants to an organic solvent (e.g., dimethyl carbonate), reacting at a reaction temperature of 5–80°C for 0.5–24 h, and after the reaction is completed, performing solid-liquid separation, drying, and recrystallization to obtain the product. Different structures of products can be prepared by controlling the molar ratio between the alkali metal-containing phosphate and tris(pentafluorophenyl)borane.

[0043] The second aspect of this application provides an electrolyte comprising a non-aqueous organic solvent, a solute, and the electrolyte provided in the first aspect of this application.

[0044] In some embodiments of this application, the mass percentage of the electrolyte is 0.01% to 10% based on the mass of the electrolyte; preferably 0.1% to 8%. For example, the mass percentage of the electrolyte in the electrolyte can be 0.01%, 0.05%, 0.08%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 3%, 5%, 8%, 10%, or a range of any two of these values. The electrolyte provided in this application contains a phosphate structure, a fluorinated phenyl structure, and a boron-containing structure. First, this novel anionic structure can generate a stable and uniform negative electrode interface film containing phosphate, BO, BF, and other components on the negative electrode surface, effectively inhibiting the decomposition of the electrolyte on the negative electrode surface and improving the cycle life of the secondary battery. In addition, the perfluorophenyl structure can enhance the oxidation resistance of the electrolyte and construct a high-voltage resistant interface protective film. The benzene ring provides chemical stability, and the strong electron-withdrawing fluorine atoms further reduce the electron cloud density of the benzene ring, greatly enhancing the oxidation resistance of the entire anionic portion. This, in turn, increases the oxidation potential of the electrolyte and improves its thermal stability. Simultaneously, the fluorinated phenyl structure can oxidize and decompose on the positive electrode surface, forming a stable LiF-rich interface film that protects the positive electrode material and reduces the dissolution of transition metal ions and structural collapse. This improves the high-temperature storage and cycling performance of the secondary battery. More importantly, the electrolyte provided in this application contains phosphoric acid, fluorinated phenyl, and boron-containing structures, which can enhance the flame retardant performance of the secondary battery. The phosphoric acid structure has a strong flame-retardant effect; when the internal temperature of the battery rises or an anomaly occurs, the phosphoric acid structure can capture hydrogen free radicals, interrupting the chain reaction and effectively preventing the battery from igniting. Furthermore, the fluorinated phenyl structure has strong electron delocalization properties, which can bind to free radicals generated during electrolyte decomposition, reducing the reactivity of these free radicals and further improving the flame retardant performance and safety of the secondary battery. The electrolyte of this application includes the electrolyte provided in the first aspect of this application, and by controlling the mass percentage content of the electrolyte within the aforementioned range, it is beneficial to improve the oxidation resistance, thermal stability, and flame retardant properties of the electrolyte, thereby improving the cycle life, high-temperature cycle performance, and high-temperature storage performance of the secondary battery, and also beneficial to improving the flame retardant performance of the secondary battery. When the mass percentage content of the electrolyte provided in this application in the electrolyte is too small, for example, less than 0.01%, it is not conducive to improving the flame retardant performance of the secondary battery; when the mass percentage content of the electrolyte provided in this application in the electrolyte is too large, for example, greater than 10%, it leads to a significant increase in electrolyte viscosity, which will worsen the wetting of the electrode materials and is not conducive to improving the electrochemical performance of the secondary battery.

[0045] In some embodiments of this application, the solute is selected from lithium salts or sodium salts, wherein the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, lithium bis(pentafluoroethyl)sulfonyl)imide, lithium bis(oxalato)borate, lithium difluorobis(oxalato)borate, lithium difluorobis(oxalato)phosphate, lithium tetrafluorooxalatophosphate, and lithium 4,5-dicyano-2-trifluoromethyl-imidazolium; and the sodium salt is selected from sodium hexafluorophosphate, sodium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, and lithium 4,5-dicyano-2-trifluoromethyl-imidazolium. The electrolyte contains at least one of sodium amine salt, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(oxalato)borate, sodium difluorobis(oxalato)borate, sodium difluorobis(oxalato)phosphate, sodium tetrafluoro(oxalato)phosphate, and sodium 4,5-dicyano-2-trifluoromethyl-imidazolium; the mass percentage of the solute is 5% to 20% based on the mass of the electrolyte; for example, the mass percentage of the solute in the electrolyte can be 5%, 8%, 10%, 12%, 15%, 18%, 20%, or a range of any two of these values. By selecting a solute within the scope of this application and using it in combination with the electrolyte provided in this application, it is beneficial to further improve the oxidation resistance and thermal stability of the electrolyte, thereby improving the cycle life, high-temperature cycle performance, and high-temperature storage performance of the secondary battery, and also beneficial to improving the flame retardant performance of the secondary battery.

[0046] In some embodiments of this application, the electrolyte comprises a non-aqueous organic solvent, a solute, and an electrolyte. The solute comprises lithium hexafluorophosphate (LiPF6), and the mass percentage of lithium hexafluorophosphate is 5% to 20% based on the mass of the electrolyte. The electrolyte comprises at least one of the compounds shown in Formula 1, Formula 2, or Formula 3, preferably at least one of Formula 1-1, Formula 2-1, or Formula 3-1. For example, the mass percentage of lithium hexafluorophosphate in the electrolyte can be 5%, 8%, 10%, 12%, 15%, 18%, 20%, or a range consisting of any two of these values. LiPF6 has poor thermal stability and is easily decomposed by heat. Under high temperature conditions, it decomposes to produce PF5 and O=PF3. Both PF5 and O=PF3 are Lewis strong acids, while the lithium salt anion of the electrolyte provided in this application is a Lewis strong base. It will interact very strongly with PF5 and O=PF3, forming coordination complexes with PF5 and O=PF3, thereby reducing the chemical reactivity of PF5 and O=PF3 and inhibiting the catalytic decomposition of the solvent by PF5 and O=PF3. by For example, PF5 and O=PF3 will form coordination compounds with this anion, respectively. and This reduces the chemical reactivity of PF5 and O=PF3, inhibiting the catalytic decomposition of the solvent by PF5 and O=PF3. The electrolyte, including the electrolyte provided in this application, is beneficial for further improving the thermal stability of the electrolyte, thereby improving the high-temperature storage performance and high-temperature cycling performance of the secondary battery.

[0047] In some embodiments of this application, the electrolyte comprises a non-aqueous organic solvent, a solute, and an electrolyte. The solute comprises sodium hexafluorophosphate (NaPF6), and the mass percentage of lithium hexafluorophosphate is 5% to 20% based on the mass of the electrolyte. The electrolyte comprises at least one of the compounds shown in Formula 1, Formula 2, or Formula 3, preferably at least one of Formula 1-2, Formula 2-2, or Formula 3-2. For example, the mass percentage of sodium hexafluorophosphate in the electrolyte can be 5%, 8%, 10%, 12%, 15%, 18%, 20%, or a range consisting of any two of these values. NaPF6 has poor thermal stability and is easily decomposed by heat. Under high-temperature conditions, it decomposes to produce PF5 and O=PF3. Both PF5 and O=PF3 are Lewis strong acids, while the anion of the electrolyte provided in this application is a Lewis strong base. This anion will interact strongly with PF5 and O=PF3, forming coordination complexes with PF5 and O=PF3, thereby reducing the chemical reactivity of PF5 and O=PF3 and inhibiting the catalytic decomposition of the solvent by PF5 and O=PF3. The electrolyte, including the electrolyte provided in this application, is beneficial to further improve the thermal stability of the electrolyte, thereby improving the high-temperature storage performance and high-temperature cycling performance of the secondary battery of the electrochemical device.

[0048] In some embodiments of this application, the non-aqueous organic solvent is selected from at least one of carbonate solvents and carboxylic acid ester solvents. The carbonate solvent is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate, bis(2,2,2)-trifluoroethyl carbonate, 2,2,3,3-tetrafluoropropyl methyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and 3,3,3-trifluoropropylene carbonate. The carboxylic acid ester solvent is selected from methyl formate, ethyl formate, butyl formate, ... The first of the following: methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, methyl valerate, ethyl valerate, propyl valerate, butyl valerate, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, β-propiolactone, β-butyrolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, 2-fluoro-1,4-butyrolactone, 3-fluoro-1,4-butyrolactone, and 4-fluoro-1,4-butyrolactone. This application does not specifically limit the mass percentage of non-aqueous organic solvents, as long as the purpose of this application is achieved. For example, based on the mass of the electrolyte, the mass percentage of non-aqueous organic solvents can be 70% to 94%; for example, the mass percentage of solute in the electrolyte can be 70%, 75%, 80%, 85%, 90%, 94%, or a range consisting of any two of these values. Including non-aqueous organic solvents within the above range in the electrolyte can give the electrolyte higher ionic conductivity and better electrochemical stability, further improving the electrolyte's oxidation resistance and thermal stability, thereby improving the cycle life, high-temperature cycle performance, and high-temperature storage performance of the secondary battery.

[0049] The third aspect of this application provides a secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte provided in the second aspect of this application.

[0050] In this application, the positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The phrase "positive electrode material layer disposed on at least one surface of the positive current collector" means that the positive electrode material layer can be disposed on one surface of the positive current collector along its thickness direction, or on two surfaces of the positive current collector along its thickness direction. It should be noted that "surface" here can refer to the entire surface of the positive current collector or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved. This application does not impose any particular limitation on the positive current collector, as long as the purpose of this application is achieved. For example, the positive current collector can be aluminum foil, aluminum alloy foil, or a composite positive current collector. The aforementioned composite positive current collector can be a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The material of the aforementioned polymer material base layer can be, but is not limited to, at least one of polypropylene (PP), polyethylene terephthalate (PET), or polybutylene terephthalate (PBT), and the material of the aforementioned metal layer can be, but is not limited to, at least one of aluminum, aluminum alloy, nickel, or nickel alloy. This application does not impose any particular limitation on the thickness of the positive electrode material layer and the positive electrode current collector, as long as the purpose of this application can be achieved. For example, the thickness of the single-sided positive electrode material layer is 35 μm to 150 μm, and the thickness of the positive electrode current collector is 5 μm to 20 μm.

[0051] The positive electrode material layer includes a positive electrode active material. This application does not impose any particular limitation on the positive electrode active material, as long as it achieves the purpose of this application. For example, in some embodiments of this application, the secondary battery is a lithium-ion battery, and the positive electrode active material may include, but is not limited to, at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, and lithium manganese iron phosphate. For example, the positive electrode active material may include, but is not limited to, LiCoO2, LiFePO4, LiFeMnPO4, and LiNi. 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.6 Co 0.1 Mn 0.3 O2 (NCM613), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.8 Co 0.1 Mn 0.1O2 (NCM811), etc. In other embodiments of this application, the secondary battery is a sodium-ion battery, and the positive electrode active material may include at least one of polyanionic materials, layered oxide materials, and Prussian blue materials. For example, polyanionic materials may include, but are not limited to, NaFePO4, Na2FeP2O7, Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, and Na2Fe(SO4)2; layered oxide materials may include, but are not limited to, NaMnO2 and NaNi. 1 / 3 Mn 2 / 3 O2, NaFe 0.5 Ni 0.5 O2, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2; Prussian blue materials may include, but are not limited to, Na2Fe[Fe(CN)6] and Na2Mn[Mn(CN)6].

[0052] In some embodiments of this application, the secondary battery is a lithium-ion battery, and the electrolyte comprises a non-aqueous organic solvent, a lithium salt, and an electrolyte. The electrolyte comprises at least one of the compounds shown in Formula 1, Formula 2, or Formula 3, preferably at least one of Formula 1-1, Formula 2-1, or Formula 3-1. In some embodiments of this application, the secondary battery is a sodium-ion battery, and the electrolyte comprises a non-aqueous organic solvent, a sodium salt, and an electrolyte. The electrolyte comprises at least one of the compounds shown in Formula 1, Formula 2, or Formula 3, preferably at least one of Formula 1-2, Formula 2-2, or Formula 3-2.

[0053] The positive electrode material layer may further include a positive electrode conductive agent and a positive electrode binder. This application does not impose any particular limitation on the types of positive electrode conductive agents and positive electrode binders, as long as they achieve the purpose of this application. For example, the positive electrode conductive agent may include, but is not limited to, at least one of superconducting carbon black (Super P), acetylene black, Ketjen black, carbon nanotubes, graphene, or carbon fiber. For example, the positive electrode binder may include, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorinated acrylate resin. This application does not impose any particular limitation on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0054] In this application, there are no particular limitations on the preparation method of the positive electrode sheet, as long as it achieves the purpose of this application. For example, it can be prepared by the following method: mixing positive electrode active material, positive electrode conductive agent, and positive electrode binder, adding N-methylpyrrolidone (NMP) and stirring evenly to obtain a positive electrode slurry with a solid content of 50wt% to 85wt%. The positive electrode slurry is uniformly coated on one surface of the positive electrode current collector, and after drying, a positive electrode sheet with a single-sided coating of positive electrode material layer is obtained. Then, the above coating steps are repeated on the other surface of the positive electrode current collector, and after drying, a positive electrode sheet with a double-sided coating of positive electrode material layer is obtained. After coating, the positive electrode sheet is obtained by cold pressing and cutting.

[0055] In this application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The phrase "the negative electrode material layer is disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its thickness direction, or on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the negative electrode current collector, or only a portion of the surface area; this application has no particular limitation, as long as the purpose of this application is achieved. This application has no particular limitation on the negative electrode current collector, as long as the purpose of this application is achieved; for example, the negative electrode current collector can be copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel or foamed copper, aluminum foil, or a composite negative electrode current collector. The aforementioned composite negative electrode current collector can be a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The material of the polymer material base layer can be, but is not limited to, at least one of polypropylene (PP), polyethylene terephthalate (PET), or polybutylene terephthalate (PBT). The material of the metal layer can be, but is not limited to, at least one of copper, copper alloy, nickel, or nickel alloy. This application does not impose any particular limitation on the thickness of the negative electrode material layer and the negative electrode current collector, as long as the purpose of this application can be achieved. For example, the thickness of the single-sided negative electrode material layer can be from 20 μm to 150 μm, and the thickness of the negative electrode current collector can be from 3 μm to 11 μm.

[0056] The negative electrode material layer includes a negative electrode active material. This application does not have any particular restrictions on the type of negative electrode active material, as long as it can achieve the purpose of this application. For example, the negative electrode active material may include, but is not limited to, at least one of graphite, soft carbon, hard carbon, silicon, silicon oxide, silicon-carbon composite and lithium titanate.

[0057] The negative electrode material layer also includes a negative electrode conductive agent and a negative electrode binder. This application does not particularly limit the types of negative electrode conductive agents and negative electrode binders, as long as they can achieve the purpose of this application. For example, the negative electrode conductive agent may include, but is not limited to, at least one of superconducting carbon black (Super P), acetylene black, Ketjen black, carbon nanotubes, graphene, or carbon fibers. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. For example, the negative electrode binder may include, but is not limited to, at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethyl methacrylate (PMAA), or carboxymethyl chitosan (CMCS). In some embodiments of this application, the negative electrode material layer may also optionally include other additives, such as thickeners, which may include, but are not limited to, sodium carboxymethyl cellulose (CMC-Na). This application does not impose any particular restrictions on the mass ratio of negative electrode active material, conductive agent, binder, and thickener in the negative electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application can be achieved.

[0058] This application does not impose any particular limitation on the preparation method of the negative electrode sheet, as long as it achieves the purpose of this application. For example, the negative electrode active material, conductive agent, thickener, and binder can be mixed in a certain proportion, and deionized water can be added and stirred evenly to obtain a negative electrode slurry with a solid content of 45wt% to 70wt%. The negative electrode slurry is uniformly coated on one surface of the negative electrode current collector, and after drying, a negative electrode sheet with a single-sided negative electrode material layer is obtained. Then, the above coating steps are repeated on the other surface of the negative electrode current collector, and after drying, a negative electrode sheet with a double-sided negative electrode material layer is obtained. After coating, the negative electrode sheet is obtained by rolling and cutting.

[0059] This application does not impose any particular limitation on the diaphragm, as long as it achieves the purpose of this application. For example, the diaphragm material may include, but is not limited to, at least one of polyethylene (PE), polypropylene (PP), polytetrafluoroethylene, polyethersulfone, glass fiber, polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), and polyamide (PA). The type of diaphragm may include at least one of woven membrane, nonwoven fabric, microporous membrane, composite membrane, rolled membrane, or spun membrane. In this application, the thickness of the diaphragm is not particularly limited, as long as it achieves the purpose of this application; for example, the thickness of the diaphragm may be from 4 μm to 20 μm.

[0060] In this application, the secondary battery also includes a casing for housing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of secondary batteries. This application does not limit the scope of these other components. This application does not impose any particular limitation on the casing; it can be a casing known in the art, as long as it achieves the purpose of this application. For example, the casing can be a rigid casing or a flexible casing. The material of the rigid casing can be metal; this application does not limit the type of metal and can use known metal rigid casings, as long as they achieve the purpose of this application. The flexible casing can be a metal plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0061] There are no particular limitations on the secondary battery in this application. For example, the secondary battery may include, but is not limited to, lithium-ion secondary batteries (lithium-ion batteries), sodium-ion secondary batteries (sodium-ion batteries), etc.

[0062] The fabrication process of the secondary battery described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, the fabrication process of the secondary battery may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. Alternatively, stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the secondary battery.

[0063] Example

[0064] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0065] Test methods and equipment:

[0066] Determination of electrolyte self-extinguishing time (SET):

[0067] Test Principle: This test simulates the behavior of electrolyte after being ignited by an external ignition source (such as a spark generated by a short circuit inside the battery). The test steps are: ignition, observation, and timing. 1. Briefly ignite a measured amount of electrolyte using a standard ignition source (such as a propane torch); 2. After removing the ignition source, observe whether the electrolyte can extinguish itself; 3. If the flame extinguishes, accurately record the time elapsed from removing the ignition source to the flame completely disappearing. If it continues to burn, record it as "not extinguished" or the time exceeds a certain threshold (such as 60 seconds).

[0068] Test standards and methods: The test shall be conducted in accordance with UL94 H standard.

[0069] The detailed steps are as follows:

[0070] 1. Testing equipment and materials

[0071] Test apparatus: A drying oven containing a desiccant (such as anhydrous calcium chloride) to maintain an anhydrous environment;

[0072] Fuel source: standard propane torch, with the inner flame height typically calibrated to 20 mm;

[0073] Sample substrate: standard fiber strips, usually 125 mm long and 13 mm wide glass fiber cloth or cotton thread;

[0074] Electrolyte sample: Electrolyte sample to be tested;

[0075] Precision balance: stopwatch, tweezers, gloves, and protective mask.

[0076] 2. Test Procedure

[0077] A. Preparations

[0078] Seal the drying chamber and ensure the internal environment is thoroughly dry;

[0079] Place the fiber strip on the balance and record its initial weight (W1).

[0080] Use a dropper to draw a certain amount of electrolyte and evenly drip it onto the fiber strip to fully wet it;

[0081] Quickly weigh the total weight of the impregnated fiber strip (W2).

[0082] The impregnated fiber strips are horizontally fixed to the clamps inside the drying oven.

[0083] B. Ignition and Testing

[0084] Pre-ignition: Ignite the propane torch and adjust the flame height to the standard requirement (inner flame height 20mm);

[0085] Ignition: Apply the torch flame horizontally to one end of the fiber strip, and ignite for 15 seconds;

[0086] Remove the heat source: After 15 seconds, immediately remove the blowtorch;

[0087] Timing and observation: Start the stopwatch and observe the combustion of the electrolyte on the fiber strip; record the time it takes for the flame on the fiber strip to extinguish itself after the fire source is removed, which is the self-extinguishing time (SET) of the electrolyte.

[0088] C. Repeatability:

[0089] Three samples were tested with the same electrolyte, and the average value was taken as the SET value of the electrolyte to ensure the reliability of the results.

[0090] 3. Interpretation of Results

[0091] SET < 10 s: Electrolytes are generally considered to have excellent flame retardant properties;

[0092] 10 s < SET < 30 s: Has some flame retardancy, but performance is moderate;

[0093] If the flame fails to extinguish after 30 seconds or fails to self-extinguish, the flame is highly flammable and poses a high safety risk.

[0094] Cyclic performance test at 25°C:

[0095] The lithium-ion battery was placed in a 25°C constant temperature chamber and left to stand for 2 hours to allow it to reach a constant temperature. It was then charged at a constant current of 2.0C to the upper limit voltage of 4.35V, followed by constant voltage charging at 4.35V until the cutoff current reached 0.05C. Finally, it was discharged at a constant current of 2.0C until the cutoff voltage reached 3.0V. The initial discharge capacity was recorded as C1. This constituted one charge-discharge cycle. This process was repeated 500 times, and the discharge capacity after the 500th cycle was recorded as C2.

[0096] Capacity retention rate at 25℃ (%) = C2 / C1 × 100%; The capacity retention rate at 25℃ is used to evaluate the room temperature cycle performance of lithium-ion batteries. The higher the capacity retention rate, the better the room temperature cycle performance of lithium-ion batteries.

[0097] The 25°C room temperature cycle performance test for sodium-ion batteries is the same as that for lithium-ion batteries, except that the upper limit charging voltage and constant voltage charging voltage are adjusted to 4.05V.

[0098] 45℃ High Temperature Cyclic Performance Test:

[0099] The lithium-ion battery was placed in a 45°C constant temperature chamber and left to stand for 2 hours to allow it to reach a constant temperature. It was then charged at a constant current of 2.0C to the upper limit voltage of 4.35V, followed by constant voltage charging at 4.35V until the cutoff current reached 0.05C. Finally, it was discharged at a constant current of 2.0C until the cutoff voltage reached 3.0V. The initial discharge capacity was recorded as C3. This constituted one charge-discharge cycle. This process was repeated 500 times, and the discharge capacity after the 500th cycle was recorded as C4.

[0100] 45℃ capacity retention rate (%) = C4 / C3 × 100%; The 45℃ capacity retention rate is used to evaluate the high-temperature cycle performance of lithium-ion batteries. The higher the capacity retention rate, the better the high-temperature cycle performance of lithium-ion batteries.

[0101] The 45℃ high-temperature cycle performance test for sodium-ion batteries is the same as that for lithium-ion batteries, except that the upper limit charging voltage and constant voltage charging voltage are adjusted to 4.05V.

[0102] 60℃ High Temperature Storage Performance Test:

[0103] The lithium-ion battery was placed in a 25°C constant temperature chamber and left to stand for 2 hours to allow it to reach a constant temperature. It was then charged at a constant current of 1.0C to the upper limit voltage of 4.35V, followed by constant voltage charging at 4.35V to the cutoff current of 0.05C. Afterward, it was discharged at a constant current of 1.0C to the cutoff voltage of 3.0V. This cycle was repeated 5 times. Then, the battery was charged at a constant current of 1.0C to the upper limit voltage of 4.35V, followed by constant voltage charging at 4.35V to the cutoff current of 0.05C. The charging capacity at this point was recorded as C5. The fully charged battery was then placed in a 60°C constant temperature chamber for 30 days. After storage, the lithium-ion battery was left to stand in a 25°C constant temperature chamber for 2 hours. After this period, it was discharged at a constant current of 1C to the cutoff voltage of 3.0V. The discharge capacity at this point was recorded as C6.

[0104] Storage capacity retention rate (%) after 30 days of storage at 60℃ = C6 / C5×100%. The higher the storage capacity retention rate, the better the high-temperature storage performance of the lithium-ion battery.

[0105] The sodium-ion battery's 60℃ high-temperature storage performance test was the same as that of the lithium-ion battery, except that the upper limit charging voltage and constant voltage charging voltage were adjusted to 4.05V.

[0106] Example 1

[0107] <Preparation of the compound shown in Formula 1-1>

[0108] In a drying room with a dew point of -30 °C, 0.1 mol of lithium phosphate (99% purity, provided by Aladdin Reagent) and 50 mL of dimethyl carbonate (99.9% purity, provided by Guangzhou Tinci Materials Co., Ltd.) were added to the reaction flask as solvents. Stirring was then initiated to ensure homogeneous mixing. Next, 0.1 mol of tris(pentafluorophenyl)borane (99% purity, provided by Aladdin Reagent) was slowly added to the reaction flask in batches. Specifically, after each batch of 0.033 mol of tris(pentafluorophenyl)borane was added, a half-hour interval was observed before adding the next batch of 0.033 mol of tris(pentafluorophenyl)borane. A total of three additions of 0.033 mol of tris(pentafluorophenyl)borane were made, resulting in a total addition of 0.1 mol of tris(pentafluorophenyl)borane. The reaction was carried out at 50 °C for 12 hours. After the reaction was complete, the filtrate was filtered, and the dimethyl carbonate was evaporated to dryness to obtain a white solid. The white solid was dissolved in ethanol at 60°C, and then toluene was added to allow the white solid to crystallize from the solution. The white solid was recrystallized three times to finally obtain the product.

[0109] The product was analyzed by nuclear magnetic resonance (NMR) spectroscopy (400 MHz, Acetone-d6, XJ001-P1), confirming that the obtained product was compound 1-1. Its NMR F-spectrum is shown below. Figure 1 As shown, the nuclear magnetic displacement is:

[0110] δ = -142.7 ppm (s, 6F); δ = -152.6 ppm (s, 3F); δ = -158.9 ppm (s, 6F);

[0111] <Preparation of Electrolyte>

[0112] In an argon-atmospheric glove box (water content <1ppm, oxygen content <1ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) are mixed uniformly at a mass ratio of 30:55:15 to obtain a non-aqueous organic solvent. Lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and the electrolyte compound shown in formula 1-1 are then added to the non-aqueous organic solvent, dissolved, and mixed uniformly to obtain an electrolyte. Based on the mass of the electrolyte, the mass percentage of lithium bis(fluorosulfonyl)imide is 3%, the mass percentage of lithium hexafluorophosphate (LiPF6) is 12%, the mass percentage of the electrolyte compound shown in formula 1-1 is 1%, and the remainder is the non-aqueous organic solvent.

[0113] <Preparation of the positive electrode>

[0114] Lithium nickel cobalt manganese oxide (LiNi) is used as the positive electrode active material. 0.6 Co 0.1 Mn 0.3O2), conductive agent superconducting carbon black (Super P), carbon nanotubes (CNTs), and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 95:3:0.5:1.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred evenly under vacuum to obtain a positive electrode slurry with a solid content of 65 wt%. The positive electrode slurry was uniformly coated onto one surface of a 16 μm thick aluminum foil for positive electrode current collectors. After drying at 85°C, a positive electrode sheet with a single-sided coating of positive electrode material layer with a coating thickness of 37 μm was obtained. The above steps were repeated on the other surface of the aluminum foil for positive electrode current collectors to obtain a positive electrode sheet with a double-sided coating of positive electrode material layer. After drying at 85°C, the sheet was rolled, trimmed, cut, and slit. After slitting, the sheet was dried at 85°C under vacuum for 5 hours, and electrode tabs were welded to obtain a positive electrode sheet with a specification of 70 mm × 54 mm. The areal density of the positive electrode active material was 25 mg / cm³. 2 .

[0115] <Preparation of Negative Electrode Sheets>

[0116] A negative electrode active material (graphite), a conductive agent (superconducting carbon black, Super P), a binder (styrene-butadiene rubber, SBR), and a thickener (sodium carboxymethyl cellulose, CMC) were mixed in a mass ratio of 95:1.5:2:1.5. Deionized water was added, and the mixture was stirred evenly under vacuum to obtain a negative electrode slurry with a solid content of 49 wt%. The negative electrode slurry was uniformly coated onto one surface of a 9 μm thick copper foil current collector. After drying at 85°C, a negative electrode sheet with a single-sided coating of negative electrode material layer with a coating thickness of 48.5 μm was obtained. The above steps were repeated on the other surface of the copper foil current collector to obtain a negative electrode sheet with a double-sided coating of negative electrode material layer. After drying at 85°C, the sheet was rolled, trimmed, cut, and slit. After slitting, the sheet was dried at 85°C under vacuum for 5 hours, and tabs were welded to obtain a negative electrode sheet with a specification of 74 mm × 58 mm. The areal density of the negative electrode active material was 15 mg / cm³. 2 .

[0117] <Preparation of the diaphragm>

[0118] A 12µm thick polyethylene (PE) ceramic diaphragm (provided by Shenzhen Xingyuan Material Technology Co., Ltd.) is used.

[0119] <Preparation of Lithium-ion Batteries>

[0120] The prepared positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes to act as a separator. The stacked battery is assembled, with the positive tab connected to the positive electrode and the negative tab connected to the negative electrode, forming an electrode assembly. The electrode assembly is placed in an aluminum foil packaging bag, with the positive and negative tabs extended from the inside to the outside of the bag. It is then vacuum-dried at 85°C for 48 hours, and the electrolyte prepared above is injected at an injection rate of 3.0 g / Ah. After vacuum sealing, formation, aging, and capacity testing, a lithium-ion battery is obtained. The formation upper limit voltage is 3.9V, the formation temperature is 45°C, and the formation resting time is 2 hours. The aging temperature is 45°C, and the aging resting time is 24 hours. Capacity testing involves charging to 4.35V at 0.1C, resting for 5 minutes, and then discharging to 3.0V at 0.1C. This process is repeated three times to obtain the lithium-ion battery.

[0121] Example 2

[0122] <Preparation of the compound shown in Formula 2-1>

[0123] In a dry room with a dew point of -30 °C, 0.1 mol of lithium phosphate (99% purity, provided by Aladdin Reagent) and 50 mL of dimethyl carbonate (99.9% purity, provided by Guangzhou Tinci Materials Co., Ltd.) were added to the reaction flask as solvents. Stirring was then initiated to ensure homogeneous mixing. Next, 0.2 mol of tris(pentafluorophenyl)borane (99% purity, provided by Aladdin Reagent) was slowly added to the reaction flask in batches. Specifically, after each batch of 0.067 mol of tris(pentafluorophenyl)borane was added, a half-hour interval was observed before adding the next batch of 0.067 mol of tris(pentafluorophenyl)borane. A total of three additions of 0.067 mol of tris(pentafluorophenyl)borane were made, resulting in a total addition of 0.2 mol of tris(pentafluorophenyl)borane. The reaction was carried out at 50 °C for 12 hours. After the reaction was complete, the filtrate was filtered, and the dimethyl carbonate was evaporated to dryness to obtain a white solid. The white solid was dissolved in ethanol at 60°C, and then toluene was added to allow the white solid to crystallize from the solution. This recrystallization process was repeated three times to obtain the final product. Nuclear magnetic resonance (NMR) spectroscopy (400 MHz, Acetone-d6, XJ001-P1) confirmed that the product was compound 2-1. Its NMR F-spectrum is shown below. Figure 2 As shown, the nuclear magnetic displacement is:

[0124] δ = -141.78 ppm (s, 12F); δ = -151.49 ppm (s, 6F); δ = -157.64 ppm (s, 12F);

[0125] Except for replacing the electrolytes with the compounds shown in Formula 2-1 according to Table 1, the rest is the same as in Example 1.

[0126] Example 3

[0127] <Preparation of the compound shown in Formula 3-1>

[0128] In a dry room with a dew point of -30 °C, 0.1 mol of lithium phosphate (99% purity, provided by Aladdin Reagent) and 50 mL of dimethyl carbonate (99.9% purity, provided by Guangzhou Tinci Materials Co., Ltd.) were added to the reaction flask as solvents. Stirring was then initiated to ensure homogeneous mixing. Next, 0.3 mol of tris(pentafluorophenyl)borane (99% purity, provided by Aladdin Reagent) was slowly added to the reaction flask in batches. Specifically, after each batch of 0.1 mol of tris(pentafluorophenyl)borane was added, a half-hour interval was observed before adding the next batch of 0.1 mol of tris(pentafluorophenyl)borane. The reaction was carried out at 50 °C for 12 hours. After the reaction was complete, the filtrate was filtered, and the dimethyl carbonate was evaporated to dryness to obtain a white solid. The white solid was dissolved in ethanol at 60°C, and then toluene was added to allow the white solid to crystallize out of the solution. The white solid was recrystallized three times to finally obtain the product.

[0129] The product was analyzed by nuclear magnetic resonance (NMR) spectroscopy (400 MHz, Acetone-d6, XJ001-P1), confirming that the obtained product was compound 3-1. Its NMR F-spectrum is shown below. Figure 3 As shown, the nuclear magnetic displacement is:

[0130] δ = -141.09 ppm (s, 18F); δ = -150.27 ppm (s, 9F); δ = -156.15 ppm (s, 18F).

[0131] Except for replacing the electrolyte with the compound shown in Formula 3-1 according to Table 1, the rest is the same as in Example 1.

[0132] Example 4

[0133] Except for replacing the electrolytes with the compounds shown in Formula 1-1 and Formula 2-1 according to Table 1, the rest is the same as in Example 1.

[0134] Examples 5 to 10

[0135] Except for adjusting the mass percentage of the electrolyte according to Table 1, and changing the mass percentage of the non-aqueous organic solvent accordingly, everything else is the same as in Example 1.

[0136] Example 11

[0137] Except for adjusting the type of solute according to Table 1, everything else is the same as in Example 1.

[0138] Example 12

[0139] <Preparation of the compounds shown in Formula 1-2>

[0140] In a dry room with a dew point of -30 °C, 0.1 mol of sodium phosphate (99% purity, provided by Aladdin Reagent) and 50 mL of dimethyl carbonate (99.9% purity, provided by Guangzhou Tinci Materials Co., Ltd.) were added to the reaction flask as solvents. Stirring was then initiated to ensure homogeneous mixing. Next, 0.1 mol of tris(pentafluorophenyl)borane (99% purity, provided by Aladdin Reagent) was slowly added to the reaction flask in batches. Specifically, after each batch of 0.033 mol of tris(pentafluorophenyl)borane was added, a half-hour interval was observed before adding the next batch of 0.033 mol of tris(pentafluorophenyl)borane. A total of three additions of 0.033 mol of tris(pentafluorophenyl)borane were made, resulting in a total addition of 0.1 mol of tris(pentafluorophenyl)borane. The reaction was carried out at 50 °C for 12 hours. After the reaction was complete, the filtrate was filtered, and the dimethyl carbonate was evaporated to dryness to obtain a white solid. The white solid was dissolved in ethanol at 60°C, and then toluene was added to allow the white solid to crystallize from the solution. This recrystallization process was repeated three times to obtain the final product. Nuclear magnetic resonance (NMR) spectroscopy (400 MHz, Acetone-d6, XJ001-P1) confirmed that the product was the compound of formula 1-2. Its NMR F-spectrum is shown below. Figure 4 As shown, the nuclear magnetic displacement is:

[0141] δ = -143.15 ppm (s, 6F); δ = -152.98 ppm (s, 3F); δ = -159.42 ppm (s, 6F).

[0142] <Preparation of Electrolyte>

[0143] In an argon-atmospheric glove box (water content <1ppm, oxygen content <1ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) are mixed uniformly at a mass ratio of 30:55:15 to obtain a non-aqueous organic solvent. Solutes sodium hexafluorophosphate (NaPF6), sodium bis(fluorosulfonyl)imide (NaFSI), and the electrolyte compound shown in formula 1-2 are then added to the non-aqueous organic solvent, dissolved, and mixed uniformly to obtain an electrolyte. Based on the mass of the electrolyte, the mass percentage of sodium bis(fluorosulfonyl)imide is 3%, the mass percentage of sodium hexafluorophosphate (NaPF6) is 12%, the mass percentage of the electrolyte compound shown in formula 1-2 is 1%, and the remainder is the non-aqueous organic solvent.

[0144] <Preparation of the positive electrode>

[0145] NaNi, the positive electrode active material 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 (NFM), superconducting carbon black (Super P), carbon nanotubes (CNTs), and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 95:2:0.5:2.5, and N-methylpyrrolidone (NMP) was added. The mixture was stirred evenly under vacuum to obtain a positive electrode slurry with a solid content of 65 wt%. The positive electrode slurry was uniformly coated onto one surface of a 16 μm thick aluminum foil current collector and dried at 85°C to obtain a single-sided positive electrode sheet with a coating thickness of 37 μm. The above steps were repeated on the other surface of the aluminum foil current collector to obtain a double-sided positive electrode sheet. After drying at 85°C, the sheet was rolled, trimmed, cut, and slit. After slitting, the sheet was dried at 85°C under vacuum for 5 hours and then the tabs were welded to obtain a positive electrode sheet with a specification of 70 mm × 54 mm. The areal density of the positive electrode active material was 33 mg / cm³. 2 .

[0146] <Preparation of Negative Electrode Sheets>

[0147] Hard carbon (HC) as the negative electrode active material, superconducting carbon black (Super P) as the conductive agent, styrene-butadiene rubber (SBR) as the binder, and sodium carboxymethyl cellulose (CMC) as the thickener were mixed in a mass ratio of 95:2:2:1. Deionized water was added, and the mixture was stirred evenly under vacuum to obtain a negative electrode slurry with a solid content of 49 wt%. The negative electrode slurry was uniformly coated onto one surface of a copper foil with a negative electrode current collector thickness of 9 μm. After drying at 85°C, a negative electrode sheet with a single-sided coating of negative electrode material layer with a coating thickness of 48.5 μm was obtained. The above steps were repeated on the other surface of the copper foil with a negative electrode current collector layer to obtain a negative electrode sheet with a double-sided coating of negative electrode material layer. After drying at 85°C, the sheet was rolled, trimmed, cut, and slit. After slitting, the sheet was dried at 85°C under vacuum for 5 hours, and electrode tabs were welded to obtain a negative electrode sheet with a specification of 74 mm × 58 mm. The areal density of the negative electrode active material was 22 mg / cm³. 2 .

[0148] <Preparation of the diaphragm>

[0149] A 12µm thick polyethylene (PE) ceramic diaphragm (provided by Shenzhen Xingyuan Material Technology Co., Ltd.) is used.

[0150] <Preparation of Sodium-ion Batteries>

[0151] The prepared positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes to act as a separator. The stacked battery is assembled, with the positive tab connected to the positive electrode and the negative tab connected to the negative electrode, forming an electrode assembly. The electrode assembly is placed in an aluminum foil packaging bag, with the positive and negative tabs extended from the inside to the outside of the bag. It is then vacuum-dried at 85°C for 48 hours, and the electrolyte prepared above is injected at an injection rate of 3.0 g / Ah. After vacuum sealing, formation, aging, and capacity testing, a sodium-ion battery is obtained. The formation upper limit voltage is 3.7V, the formation temperature is 45°C, and the formation resting time is 2 hours. The aging temperature is 45°C, and the aging resting time is 24 hours. Capacity testing involves charging to 4.05V at 0.1C, resting for 5 minutes, and then discharging to 3.0V at 0.1C. This process is repeated three times to obtain the sodium-ion battery.

[0152] Comparative Example 1

[0153] Except that the electrolyte compound of formula 1-1 is not added to the electrolyte, the mass percentage of the solute remains unchanged, and the mass percentage of the non-aqueous organic solvent changes accordingly, everything else is the same as in Example 1.

[0154] Comparative Example 2

[0155] Except for the absence of the electrolyte compound shown in Formula 1-1 in the electrolyte, the mass percentage of LiPF6 in the solute changes accordingly, while the mass percentages of LiFSI and the non-aqueous organic solvent remain unchanged; otherwise, it is the same as in Example 1.

[0156] Comparative Example 3

[0157] Except for not adding the electrolyte compounds shown in Formulas 1-2 to the electrolyte, keeping the mass percentage of the solute unchanged, and changing the mass percentage of the non-aqueous organic solvent accordingly, everything else is the same as in Example 12.

[0158] Comparative Example 4

[0159] Except for the absence of the electrolyte compound shown in Formula 1-2 in the electrolyte, the mass percentage of NaPF6 in the solute changes accordingly, while the mass percentages of NaFSI and the non-aqueous organic solvent remain unchanged. Otherwise, it is the same as in Example 12.

[0160] Comparative Example 5

[0161] Except for replacing the electrolyte with LiB(C6F5)3(PO2F2) according to Table 1, everything else is the same as in Example 1. The structural formula of LiB(C6F5)3(PO2F2) is as follows:

[0162]

[0163] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Table 1.

[0164] Table 1

[0165]

[0166] Note: In Table 1, " / " indicates that there are no relevant preparation parameters.

[0167] As can be seen from Examples 1 to 12 and Comparative Examples 1 to 5, the electrolytes in the embodiments of this application include the electrolyte provided in this application. The resulting electrolytes have a shorter self-extinguishing time, and the resulting secondary batteries have higher capacity retention rates at 25°C, 45°C, and 60°C. This indicates that the secondary batteries have good flame retardant properties, as well as long cycle life, good high-temperature cycling performance, and high-temperature storage performance. In contrast, the electrolytes in Comparative Examples 1 to 4 do not include the electrolyte provided in this application. The resulting electrolytes have a longer self-extinguishing time, and the resulting secondary batteries have lower capacity retention rates at 25°C, 45°C, and 60°C. This indicates that the secondary batteries in Comparative Examples 1 to 4 have poorer flame retardant properties, shorter cycle life, poorer high-temperature cycling performance, and poorer high-temperature storage performance. The electrolyte of Comparative Example 5 includes LiB(C6F5)3(PO2F2), but does not include the electrolyte provided in this application. The self-extinguishing time of the obtained electrolyte is relatively long, at 23s, indicating that its flame retardant performance is poor.

[0168] The mass percentage of the electrolyte affects the flame retardant performance, cycle life, high-temperature cycling performance, and high-temperature storage performance of a secondary battery. As can be seen from Examples 1, 5 to 10, and Comparative Examples 1 to 2, by adding an electrolyte within the scope of this application to the electrolyte and controlling the mass percentage of the electrolyte within the range of 0.01% to 10%, the resulting electrolyte has a shorter self-extinguishing time. Simultaneously, the resulting secondary battery exhibits higher capacity retention at 25°C, higher capacity retention at 45°C, and higher storage capacity retention at 60°C. This indicates that the secondary battery possesses good flame retardant performance, as well as a long cycle life, good high-temperature cycling performance, and high-temperature storage performance.

[0169] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrolyte, characterized in that, The electrolyte comprises a non-aqueous organic solvent, a solute, and an electrolyte, wherein the electrolyte comprises at least one of the compounds shown in Formula 1, Formula 2, or Formula 3. 、 、 ； Among them, X, Y, and Z are alkali metal elements; Based on the mass of the electrolyte, the mass percentage of the electrolyte is from 0.01% to 10%; and The solute is selected from lithium salts or sodium salts. The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, lithium bis(pentafluoroethyl)sulfonyl)imide, lithium bis(oxalate)borate, lithium difluorobis(oxalate)borate, lithium difluorobis(oxalate)phosphate, lithium tetrafluorooxalate phosphate, and lithium 4,5-dicyano-2-trifluoromethyl-imidazolium. The sodium salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethyl)sulfonyl)imide, sodium bis(oxalate)borate, sodium difluorobis(oxalate)borate, sodium difluorobis(oxalate)phosphate, sodium tetrafluorooxalate phosphate, and sodium 4,5-dicyano-2-trifluoromethyl-imidazolium.

2. The electrolyte according to claim 1, characterized in that, X, Y, and Z are selected from any one of Li, Na, K, Rb, and Cs.

3. The electrolyte according to claim 1, characterized in that, The compound represented by Formula 1 is selected from at least one of the following compounds: 、 ； The compound represented by Formula 2 is selected from at least one of the following compounds: 、 ； The compound represented by Formula 3 is selected from at least one of the following compounds: 、 。 4. The electrolyte according to any one of claims 1 to 3, characterized in that, Based on the mass of the electrolyte, the mass percentage of the electrolyte is 0.1% to 8%.

5. The electrolyte according to any one of claims 1 to 3, characterized in that, Based on the mass of the electrolyte, the mass percentage of the solute is 5% to 20%.

6. The electrolyte according to any one of claims 1 to 3, characterized in that, The solute includes lithium hexafluorophosphate, and the mass percentage of lithium hexafluorophosphate is 5% to 20% based on the mass of the electrolyte; or, the solute includes sodium hexafluorophosphate, and the mass percentage of sodium hexafluorophosphate is 5% to 20% based on the mass of the electrolyte.

7. The electrolyte according to any one of claims 1 to 3, characterized in that, The non-aqueous organic solvent is selected from at least one of carbonate solvents and carboxylic acid ester solvents. The carbonate solvent is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate, bis(2,2,2)-trifluoroethyl carbonate, 2,2,3,3-tetrafluoropropyl methyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and 3,3,3-trifluoropropylene carbonate. The carboxylic acid ester solvent is selected from methyl formate, ethyl formate, butyl formate, methyl acetate, and... Ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, methyl valerate, ethyl valerate, propyl valerate, butyl valerate, pentyl valerate, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, β-propiolactone, β-butyrolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, 2-fluoro-1,4-butyrolactone, 3-fluoro-1,4-butyrolactone, and 4-fluoro-1,4-butyrolactone.

8. A secondary battery, characterized in that, The secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte according to any one of claims 1 to 7.

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