A high voltage electrolyte and lithium ion battery

Abstract

The application belongs to the technical field of lithium batteries, and discloses a high-voltage electrolyte and a lithium ion battery, wherein the electrolyte comprises a sulfonate compound, a lithium salt, a cosolvent, a polymer monomer and an initiator, the structural general formula of the sulfonate compound is as follows: in the structural general formula, R1 is an alkyl group comprising 1-5 carbon atoms and a halide of the alkyl group, and R2 is one of an oxygen alkyl group, a halide of the oxygen alkyl group, a cyano substituent and an unsaturated functional group substituent, which contains at least one oxygen atom. The high-voltage electrolyte prepared by using the sulfonate compound containing the oxygen alkyl group can adapt to various high-voltage window positive electrode materials, and the compatibility of the high-voltage electrolyte with a high-capacity negative electrode is improved. In the lithium ion battery, the electrolyte can form a stable fluorine-rich interface film, so that the high-temperature cycle and storage performance of the battery are improved while the room-temperature cycle performance of the battery is ensured.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a high-voltage electrolyte and a lithium-ion battery. Background Technology

[0002] With the rapid development of application demands, people have put forward higher requirements for the energy density of lithium-ion batteries. High specific capacity and high voltage cathode materials (such as lithium-rich manganese-based and high-nickel ternary materials) have become the key direction for achieving breakthroughs in energy density.

[0003] However, the operating voltage of these cathode materials is typically above 4.5V. Traditional electrolytes are prone to oxidative decomposition at this voltage, leading to interfacial side reactions, gas generation, transition metal dissolution, and irreversible phase transitions in the cathode structure. This results in rapid capacity decay, a continuous increase in interfacial impedance, and even thermal runaway. Meanwhile, researchers often focus excessively on the electrolyte oxidation window and less on the compatibility between the electrolyte and the lithium metal anode. Developing high-voltage electrolytes that are oxidation-resistant, highly compatible with lithium metal, and capable of constructing stable electrode-electrolyte interface films is crucial for improving the cycle performance and safety of high-voltage lithium-ion batteries using lithium-rich manganese-based and high-nickel ternary cathode materials.

[0004] Typically, constructing high-concentration electrolytes can improve the electrochemical window and film stability by adjusting ion-dipole interactions, but this faces challenges such as high cost, high viscosity, and slow interfacial transport kinetics. While weakly solvated electrolytes can generate inorganic-rich solid electrolyte interfacial films and lower the lithium-ion desolvation energy barrier, the free solvents in weakly solvated electrolytes exhibit a high oxidation tendency, easily leading to unstable cathode electrolyte interfaces, making it difficult to simultaneously achieve high operating voltage and high energy density. To improve the energy density and cycle stability of high-voltage lithium-ion batteries, Chinese patent CN120199904A discloses a sulfonate-based electrolyte. Although it improves the electrolyte's oxidation resistance and adapts to high-voltage cathodes, its sulfonate-based compounds lack targeted functional group modification, failing to balance high-voltage oxidation resistance with lithium metal anode compatibility. It also does not solve the problems of lithium dendrite growth and interfacial film instability, resulting in limited energy density improvement and still failing to meet the practical application requirements of high-energy-density lithium-ion batteries.

[0005] Therefore, developing a high-voltage electrolyte that combines high oxidation resistance, high lithium metal compatibility, and good interfacial film formation effect will help to build high-energy-density lithium-ion batteries. Summary of the Invention

[0006] This invention provides a high-voltage electrolyte and a lithium-ion battery. It uses an oxygen-containing alkyl sulfonate compound as a key component of the high-voltage electrolyte, which solves the problems of easy decomposition of traditional electrolytes under high operating voltage, incompatibility with lithium metal anodes, and unstable derived interface films. It can be matched with high-voltage, high-capacity cathode materials to construct high-energy-density lithium-ion batteries.

[0007] The technical solution adopted in this invention is: The first aspect of the present invention provides a high-voltage electrolyte comprising a sulfonate compound, a lithium salt, a cosolvent, a polymer monomer, and an initiator; wherein the mass ratio of the sulfonate compound, lithium salt, cosolvent, polymer monomer, and initiator is (1-20):1:(0.5-20):(0.1-15):(0.01-5).

[0008] Furthermore, the general chemical structural formula of the sulfonate compound is as follows: In the general structural formula, R1 is an alkyl group or alkyl halide containing 1-5 carbon atoms, and R2 is one of an oxoalkyl group or oxoalkyl halide containing at least one oxygen atom, a cyano-substituted product, or an unsaturated functional group substituted product.

[0009] Furthermore, the lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxalateborate, lithium difluorooxalateborate, lithium tetrafluoroborate, and lithium nitrate.

[0010] Furthermore, the co-solvent includes one or more of the following: carbonate co-solvents, phosphate co-solvents, ether co-solvents, carboxylic acid ester co-solvents, nitrile co-solvents, sulfone co-solvents, and alkane co-solvents.

[0011] The carbonate cosolvent includes one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and vinylene carbonate. The phosphate ester cosolvent includes one or more of trimethyl phosphate, triethyl phosphate, tributyl phosphate, triethyl fluorophosphate, and triethyl chlorophosphate. The ether cosolvents include one or more of the following: ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran, tetrahydropyran, 1,3-dioxopentane, 1,4-dioxane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, and 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether. The carboxylic acid ester cosolvents include one or more of the following: butyl formate, amyl formate, propyl acetate, butyl acetate, methyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, butyl fluoroformate, amyl fluoroformate, propyl fluoroacetate, butyl fluoroacetate, methyl fluoropropionate, propyl fluoropropionate, butyl fluoropropionate, methyl fluorobutyrate, and ethyl fluorobutyrate. The nitrile cosolvents include one or more of acetonitrile, propionitrile, valerate, glutaronitrile, adiponitrile, heptanonitrile, heptanonitrile, octanoic acid, and octanoic acid. The sulfone cosolvents include one or more of sulfolane, dimethyl sulfoxide and diethyl sulfoxide, and methyl ethyl sulfone; The alkane cosolvents include one or more of dichloromethane, hexafluorobenzene, difluorobenzene, o-fluorotoluene, m-fluorotoluene, and p-fluorotoluene.

[0012] Furthermore, the polymer monomer includes one or more of diallyl carbonate, ethylene carbonate, N,N-methylenebisacrylamide, pentaerythritol tetraacrylate, polyethylene glycol diacrylate, and butyl acrylate.

[0013] Furthermore, the initiator is an azo thermal initiator, which includes one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate.

[0014] The second aspect of the present invention provides a method for preparing the high-voltage electrolyte as follows: a sulfonate compound, a lithium salt and a co-solvent are mixed and stirred until a uniform and clear liquid is formed, then a polymer monomer and an initiator are added, and the mixture is stirred again until a uniform liquid is formed to obtain the high-voltage electrolyte.

[0015] A third aspect of the present invention is to provide a lithium-ion battery comprising the above-described high-voltage electrolyte, positive electrode, negative electrode and separator.

[0016] Furthermore, the active material of the positive electrode includes one or more of the following positive electrode materials: lithium-rich manganese-based (LRMO), lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium manganese oxide (LMO), lithium cobalt oxide (LCO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), and lithium nickel cobalt aluminum oxide (NCA).

[0017] Furthermore, the negative electrode includes one or more of the following: lithium metal, graphite, silicon negative electrode, silicon-carbon negative electrode, silicon suboxide, lithium titanate, and non-negative electrode materials.

[0018] Furthermore, the diaphragm includes one or more of the following: polyethylene diaphragm, polypropylene diaphragm, PP / PE / PP three-layer composite diaphragm, ceramic / PE composite diaphragm, GF / A glass fiber diaphragm, GF / D glass fiber diaphragm, and GF / F glass fiber diaphragm.

[0019] A fourth aspect of the present invention is to provide an application of the above-mentioned high-voltage electrolyte in the preparation of lithium-ion batteries.

[0020] Compared with the prior art, the advantages and beneficial effects of the present invention are: (1) The present invention uses sulfonate compounds containing alkyl groups as the core component of high-voltage electrolytes. Compared with sulfonate compounds without alkyl groups, the sulfonate compounds of the present invention have excellent lithium metal compatibility by introducing alkyl groups at the R2 position, reducing the side reactions between the electrolyte and high-capacity negative electrodes (e.g., lithium metal negative electrodes, self-generated negative electrodes / no negative electrodes), which helps to uniformly deposit lithium ions, reduce the growth of lithium dendrites, improve the coulombic efficiency of the electrolyte, and improve the safety and cycle life of lithium metal batteries.

[0021] (2) The high-voltage electrolyte prepared by the present invention using sulfonate compounds containing alkyl groups as the main solvent has an electrochemical window >5 V and exhibits good compatibility with high-voltage cathode materials (lithium-rich manganese-based cathode materials or high-nickel ternary cathode materials). It can be used to assemble solid-state batteries with a wide electrochemical window, good thermal stability, long stable cycle and high capacity retention, with an energy density of over 500 Wh / kg.

[0022] (3) By controlling the types and proportions of sulfonate compounds containing alkyl groups, cosolvents and polymer monomers, this invention optimizes the electrolyte solvation shell, enables rapid film formation on the electrode surface, and forms a stable electrode-electrolyte interface film containing F inorganic components, which significantly suppresses side reactions between the electrolyte and the electrode and battery capacity decay.

[0023] (4) The electrolyte of the present invention has excellent thermal stability, which improves the storage and cycling performance of the battery at high temperature and effectively prevents the occurrence of battery thermal runaway. Attached Figure Description

[0024] Figure 1 The graph shows the test results of the electrochemical window of the lithium-ion battery using the electrolyte of Example 1. Figure 2 The charge-discharge curves of a lithium-rich manganese-based cathode lithium-ion battery using the electrolyte of Example 1 are shown. Figure 3 The charge-discharge curves of a nickel-cobalt-manganese cathode lithium-ion battery using the electrolyte of Example 2 are shown. Figure 4The charge-discharge curves of the lithium-rich manganese-based cathode lithium-ion battery using the electrolyte of Comparative Example 1 are shown. Figure 5 The charge-discharge curves of the nickel-cobalt-manganese cathode lithium-ion battery using the electrolyte of Comparative Example 2 are shown. Figure 6 SEM image of lithium deposition on the negative electrode of a lithium-ion battery using the electrolyte of Example 1; Figure 7 SEM image of lithium deposition on the negative electrode of a lithium-ion battery using the electrolyte of Comparative Example 3. Figure 8 SEM image of lithium deposition on the negative electrode of a lithium-ion battery using the electrolyte of Comparative Example 5. Figure 9 SEM image of the NCM cathode material after cycling in a lithium-ion battery using the electrolyte of Example 2; Figure 10 SEM images of the NCM cathode material after cycling in the lithium-ion battery using the electrolyte of Comparative Example 4. Figure 11 SEM images of the NCM cathode material after cycling in the lithium-ion battery using the electrolyte of Comparative Example 6. Figure 12 To apply the electrolytes of Example 1, Comparative Example 3, and Comparative Example 5 Battery coulomb efficiency diagram; Figure 13 For the application of the electrolyte in Example 1 Battery cycle diagram; Figure 14 The F / C ratio diagrams of the positive electrode interface film of the electrolytes in Example 2 and Comparative Example 4 are shown. Figure 15 This is a capacity diagram of the soft-pack battery in Application Example 2. Detailed Implementation

[0025] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0026] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0027] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0028] Unless otherwise specified, in this article, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of”. For example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a”.

[0029] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0030] The present invention provides a high-voltage electrolyte, characterized in that it comprises a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator; wherein the mass ratio of the sulfonate compound, lithium salt, co-solvent, polymer monomer, and initiator is (1-20):1:(0.5-20):(0.1-15):(0.01-5).

[0031] Preferably, the general chemical structural formula of the sulfonate compound is as follows: In the general formula, R1 is an alkyl group or alkyl halide containing 1-5 carbon atoms, and R2 is one of an oxoalkyl group or oxoalkyl halide containing at least one oxygen atom, a cyano-substituted product, or an unsaturated functional group substituted product.

[0032] Preferably, the lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxalateborate, lithium difluorooxalateborate, lithium tetrafluoroborate, and lithium nitrate.

[0033] Preferably, the cosolvent includes one or more of the following: carbonate cosolvents, phosphate cosolvents, ether cosolvents, carboxylic acid ester cosolvents, nitrile cosolvents, sulfone cosolvents, and alkane cosolvents.

[0034] Among them, carbonate cosolvents include one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and vinylene carbonate. Phosphate ester cosolvents include one or more of trimethyl phosphate, triethyl phosphate, tributyl phosphate, triethyl fluorophosphate, and triethyl chlorophosphate. Ether cosolvents include one or more of the following: ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran, tetrahydropyran, 1,3-dioxopentane, 1,4-dioxane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, and 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether. Carboxylic acid ester cosolvents include one or more of the following: butyl formate, amyl formate, propyl acetate, butyl acetate, methyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, butyl fluoroformate, amyl fluoroformate, propyl fluoroacetate, butyl fluoroacetate, methyl fluoropropionate, propyl fluoropropionate, butyl fluoropropionate, methyl fluorobutyrate, and ethyl fluorobutyrate. Nitrile cosolvents include one or more of acetonitrile, propionitrile, valerium pentonitrile, glutaronitrile, adiponitrile, heptanonitrile, heptanonitrile, octonitrile, and octonitrile; The sulfone cosolvent is one or more of sulfolane, dimethyl sulfoxide and diethyl sulfoxide, and methyl ethyl sulfone; Alkane cosolvents include one or more of dichloromethane, hexafluorobenzene, difluorobenzene, o-fluorotoluene, m-fluorotoluene, and p-fluorotoluene.

[0035] Preferably, the polymer monomer includes one or more of diallyl carbonate, ethylene carbonate, N,N-methylenebisacrylamide, pentaerythritol tetraacrylate, polyethylene glycol diacrylate, and butyl acrylate.

[0036] Preferably, the initiator includes an azo thermal initiator. The azo thermal initiator includes one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate.

[0037] The present invention also provides a method for preparing the above-mentioned high-voltage electrolyte, comprising the following steps: mixing a sulfonate compound, a lithium salt and a co-solvent and stirring until a uniform and clear liquid is formed; then adding a polymer monomer and an initiator and stirring again until a uniform liquid is formed, thereby obtaining the high-voltage electrolyte.

[0038] The present invention also provides a lithium-ion battery, which applies the above-mentioned high-voltage electrolyte to the lithium-ion battery, and includes a positive electrode, a negative electrode, and a separator in addition to the above-mentioned high-voltage electrolyte.

[0039] Preferably, the active material of the positive electrode includes one or more of lithium-rich manganese (LRMO), lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium manganese oxide (LMO), lithium cobalt oxide (LCO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), and lithium nickel cobalt aluminum oxide (NCA).

[0040] Preferably, the negative electrode includes one or more of lithium metal, graphite, silicon negative electrode, silicon-carbon negative electrode, silicon suboxide, lithium titanate, and non-negative electrode materials.

[0041] Preferably, the separator includes one or more of the following: polyethylene separator, polypropylene separator, PP / PE / PP three-layer composite separator, ceramic / PE composite separator, GF / A glass fiber separator, GF / D glass fiber separator, and GF / F glass fiber separator.

[0042] Preferably, the above-mentioned high-voltage electrolyte is added to the lithium-ion battery and polymerized at 60-85°C for 20-120 minutes, thereby transforming the liquid high-voltage electrolyte into a solid high-voltage electrolyte, thus obtaining a solid-state lithium-ion battery.

[0043] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0044] Example 1 This embodiment provides a high-voltage electrolyte comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.1:0.01. The general structural formula of the sulfonate compound is as follows: In the general formula, R1 is methyl and R2 is (2-methoxy)ethyl. The lithium salt is lithium bis(trifluoromethanesulfonyl)imide, the cosolvent is ethyl methyl carbonate, the polymer monomer is pentaerythritol tetraacrylate, and the initiator is azobisisobutyronitrile.

[0045] The preparation method of high-voltage electrolyte is as follows: sulfonate compound, lithium salt and co-solvent are mixed and stirred until a uniform and clear liquid is formed. Then, polymer monomer and initiator are added and stirred again until a uniform liquid is formed, thus obtaining high-voltage electrolyte.

[0046] Solid-state lithium-ion batteries were prepared using the aforementioned high-voltage electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery and then polymerized in an 80 °C oven for 60 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium-rich manganese-based (LRMO), the negative electrode was metallic lithium, and the separator was a polypropylene separator.

[0047] Example 2 This embodiment provides a high-voltage electrolyte comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.1:0.01, wherein the sulfonate compound, lithium salt, co-solvent, polymer monomer, and initiator are the same as in Example 1.

[0048] The preparation method of the high-voltage electrolyte is the same as that in Example 1.

[0049] Solid-state lithium-ion batteries were prepared using the aforementioned high-voltage electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, which was then polymerized in an 80 °C oven for 60 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium nickel cobalt manganese oxide (NCM), the negative electrode was metallic lithium, and the separator was a polypropylene separator.

[0050] Example 3 This embodiment provides a high-voltage electrolyte comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1.5:0.1:0.01, wherein the sulfonate compound, polymer monomer, and initiator are the same as in Example 1.

[0051] The lithium salt is a combination of lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalate borate in a mass ratio of 5:1, and the co-solvent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0052] The preparation method of the high-voltage electrolyte is the same as that in Example 1.

[0053] Solid-state lithium-ion batteries were prepared using the aforementioned high-voltage electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, which was then polymerized in an 80 °C oven for 60 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium-rich manganese-based (LRMO), the negative electrode was metallic lithium, and the separator was a polypropylene membrane.

[0054] Example 4 This embodiment provides a high-voltage electrolyte comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.1:0.01, wherein the sulfonate compound, lithium salt, co-solvent, polymer monomer, and initiator are the same as in Example 3.

[0055] The preparation method of the high-voltage electrolyte is the same as that in Example 1.

[0056] Solid-state lithium-ion batteries were prepared using the aforementioned high-voltage electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, which was then polymerized in an 80 °C oven for 60 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium nickel cobalt manganese oxide (NCM), the negative electrode was metallic lithium, and the separator was a polypropylene separator.

[0057] Example 5 This embodiment provides a high-voltage electrolyte comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.5:0.01, wherein the general structural formula of the sulfonate compound is as follows: In this context, R1 is methyl and R2 is 2-(2-methoxyethoxy)ethyl.

[0058] The lithium salt is a combination of lithium bis(trifluoromethanesulfonyl)imide and lithium tetrafluoroborate in a mass ratio of 4:1. The co-solvent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. The polymer monomers are polyethylene glycol diacrylate and butyl acrylate in a mass ratio of 1:9. The initiator is azobisisobutyronitrile.

[0059] The preparation method of the high-voltage electrolyte is the same as that in Example 1.

[0060] Solid-state lithium-ion batteries were prepared using the aforementioned high-voltage electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, which was then polymerized in an 85°C oven for 100 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium-rich manganese-based (LRMO), the negative electrode was metallic lithium, and the separator was a polypropylene membrane.

[0061] Example 6 This embodiment discloses a high-voltage electrolyte comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.5:0.01, wherein the sulfonate compound, lithium salt, co-solvent, polymer monomer, and initiator are the same as in Example 5.

[0062] The preparation method of the high-voltage electrolyte is the same as that in Example 1.

[0063] Solid-state lithium-ion batteries were prepared using the aforementioned high-voltage electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, which was then polymerized in an 85°C oven for 100 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium nickel cobalt manganese oxide (NCM), the negative electrode was metallic lithium, and the separator was a polypropylene membrane.

[0064] Example 7 This embodiment discloses a high-voltage electrolyte comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.5:0.01, wherein the general structural formula of the sulfonate compound is as follows: In this mixture, R1 is trifluoromethyl, and R2 is 2-(2-methoxyethoxy)ethyl. The lithium salt is lithium bis(trifluoromethanesulfonyl)imide, the co-solvent is 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, the polymer monomers are polyethylene glycol diacrylate and butyl acrylate in a mass ratio of 1:9, and the initiator is azobisisobutyronitrile.

[0065] The preparation method of the high-voltage electrolyte is the same as that in Example 1.

[0066] Solid-state lithium-ion batteries were prepared using the aforementioned high-voltage electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, which was then polymerized in an 85°C oven for 100 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium-rich manganese-based (LRMO), the negative electrode was metallic lithium, and the separator was a polypropylene membrane.

[0067] Example 8 This embodiment discloses a high-voltage electrolyte comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.5:0.01, wherein the sulfonate compound, lithium salt, co-solvent, polymer monomer, and initiator are the same as in Example 7.

[0068] The preparation method of the high-voltage electrolyte is the same as that in Example 1.

[0069] Solid-state lithium-ion batteries were prepared using the aforementioned high-voltage electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, which was then polymerized in an 85°C oven for 100 minutes to obtain the solid-state lithium-ion battery. The positive electrode active material was lithium nickel cobalt manganese oxide (NCM), the negative electrode was metallic lithium, and the separator was a polypropylene separator.

[0070] Comparative Example 1 This embodiment provides a liquid electrolyte comprising a sulfonate compound, a lithium salt, and a co-solvent in a mass ratio of 5:1:1. The general structural formula of the sulfonate compound is as follows: In the general formula, R1 is methyl and R2 is (2-methoxy)ethyl. The lithium salt is lithium bis(trifluoromethanesulfonyl)imide, and the co-solvent is ethyl methyl carbonate.

[0071] The electrolyte is prepared by mixing the sulfonate compound, lithium salt and co-solvent in the above proportion and stirring until a uniform and clear liquid is formed, thus obtaining the electrolyte.

[0072] A lithium-ion battery is prepared using the above-mentioned electrolyte. The positive electrode, negative electrode, separator, and the above-mentioned high-voltage electrolyte are assembled into a lithium-ion battery. The active material of the positive electrode is lithium-rich manganese-based (LRMO), the negative electrode is metallic lithium, and the separator is a polypropylene separator.

[0073] Comparative Example 2 This embodiment provides a liquid electrolyte comprising a sulfonate compound, a lithium salt, and a co-solvent in a mass ratio of 5:1:1. The sulfonate compound, lithium salt, and co-solvent are the same as in Example 1.

[0074] The preparation method of the electrolyte is the same as that of Comparative Example 1.

[0075] A lithium-ion battery is prepared using the above-mentioned electrolyte, comprising a positive electrode, a negative electrode, a separator, and a high-voltage electrolyte. The active material of the positive electrode is lithium nickel cobalt manganese oxide (NCM), the negative electrode is metallic lithium, and the separator is a polypropylene separator.

[0076] Comparative Example 3 This comparative example provides a sulfonate electrolyte without alkyl groups, comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.1:0.01. The general structural formula of the sulfonate compound is as follows: In the general formula, R1 is methyl and R2 is ethyl. The lithium salt is lithium bis(trifluoromethanesulfonyl)imide, the cosolvent is ethyl methyl carbonate, the polymer monomer is pentaerythritol tetraacrylate, and the initiator is azobisisobutyronitrile.

[0077] The preparation method of the electrolyte is the same as in Example 1.

[0078] Solid-state lithium-ion batteries were prepared using the above-mentioned electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, and then polymerized in an 80 °C oven for 60 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium-rich manganese-based (LRMO), the negative electrode was metallic lithium, and the separator was a polypropylene separator.

[0079] Comparative Example 4 This comparative example provides a sulfonate electrolyte without alkyl groups, comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.1:0.01. The sulfonate compound, lithium salt, and co-solvent are the same as in Comparative Example 3. The polymer monomer is pentaerythritol tetraacrylate, and the initiator is azobisisobutyronitrile.

[0080] The preparation method of the electrolyte is the same as in Example 1.

[0081] Solid-state lithium-ion batteries were prepared using the above-mentioned electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, and then polymerized in an 80 °C oven for 60 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium nickel cobalt manganese oxide (NCM), the negative electrode was metallic lithium, and the separator was a polypropylene separator.

[0082] Comparative Example 5 This comparative example provides a cyclic sulfonate electrolyte, comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.1:0.01. The general structural formula of the sulfonate compound is as follows: The lithium salt is lithium bis(trifluoromethanesulfonyl)imide, the cosolvent is ethyl methyl carbonate, the polymer monomer is pentaerythritol tetraacrylate, and the initiator is azobisisobutyronitrile.

[0083] The preparation method of the electrolyte is the same as in Example 1.

[0084] Solid-state lithium-ion batteries were prepared using the above-mentioned electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, and then polymerized in an 80 °C oven for 60 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium-rich manganese-based (LRMO), the negative electrode was metallic lithium, and the separator was a polypropylene membrane.

[0085] Comparative Example 6 This comparative example provides a cyclic sulfonate electrolyte comprising a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.1:0.01. The sulfonate compound, lithium salt, co-solvent, polymer monomer, and initiator are the same as in Comparative Example 5.

[0086] The preparation method of the electrolyte is the same as in Example 1.

[0087] Solid-state lithium-ion batteries were prepared using the above-mentioned electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, and then polymerized in an 80 °C oven for 60 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium nickel cobalt manganese oxide (NCM), the negative electrode was metallic lithium, and the separator was a polypropylene separator.

[0088] Comparative Example 7 The difference between this comparative example and Example 1 is that a cyclic carbonate electrolyte is provided instead of a sulfonate compound, comprising a carbonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.1:0.01. The general structural formula of the carbonate compound is [insert structural formula here]. The lithium salt is lithium bis(trifluoromethanesulfonyl)imide, the cosolvent is ethyl methyl carbonate, the polymer monomer is pentaerythritol tetraacrylate, and the initiator is azobisisobutyronitrile.

[0089] The preparation method of the electrolyte is the same as in Example 1.

[0090] Solid-state lithium-ion batteries were prepared using the above-mentioned electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, and then polymerized in an 80 °C oven for 60 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium-rich manganese-based (LRMO), the negative electrode was metallic lithium, and the separator was a polypropylene membrane.

[0091] Comparative Example 8 The difference between this comparative example and Example 1 is that it does not use a sulfonate compound, but provides a chain-like carbonate electrolyte comprising a carbonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator in a mass ratio of 5:1:1:0.1:0.01. The general structural formula of the carbonate compound is... The lithium salt is lithium bis(trifluoromethanesulfonyl)imide, the cosolvent is ethyl methyl carbonate, the polymer monomer is pentaerythritol tetraacrylate, and the initiator is azobisisobutyronitrile.

[0092] The preparation method of the electrolyte is the same as in Example 1.

[0093] Solid-state lithium-ion batteries were prepared using the above-mentioned electrolyte. The positive electrode, negative electrode, separator, and electrolyte were assembled into a lithium-ion battery, and then polymerized in an 80 °C oven for 60 minutes to obtain the solid-state lithium-ion battery. The active material of the positive electrode was lithium-rich manganese-based (LRMO), the negative electrode was metallic lithium, and the separator was a polypropylene membrane.

[0094] Testing and Analysis The lithium-ion batteries of the examples and comparative examples were tested, including room temperature cycling test, high temperature cycling test, high temperature storage test and metal compatibility test. The results are shown in Table 1 and Table 2.

[0095] Room temperature cycling test: The lithium-ion battery was placed in a constant temperature chamber at 25 ℃ and charged at a rate of 0.1 C to 4.8 V (lithium-rich manganese-based cathode) or 4.6 V (lithium nickel cobalt manganese oxide cathode), and then discharged at a constant current of 0.33 C to 2.0 V (lithium-rich manganese-based cathode) or 2.8 V (lithium nickel cobalt manganese oxide cathode). After 300 cycles, the capacity retention rate of the lithium-ion battery was measured.

[0096] High-temperature cycling performance: The lithium-ion battery was placed in a constant temperature chamber at 60 °C and charged at a rate of 0.1 C to 4.8 V (lithium-rich manganese-based cathode) or 4.6 V (lithium nickel cobalt manganese oxide cathode), and then discharged at a constant current of 0.33 C to 2.0 V (lithium-rich manganese-based cathode) or 2.8 V (lithium nickel cobalt manganese oxide cathode). After 200 cycles, the capacity retention of the lithium-ion battery was measured.

[0097] High-temperature storage test: The lithium-ion battery was placed in a constant temperature chamber at 60 ℃ and charged at a rate of 0.1 C to 4.8 V (lithium-rich manganese-based cathode) or 4.6 V (lithium nickel cobalt manganese oxide cathode) at room temperature, and the initial capacity of the battery was measured; then, after being stored in a 60 ℃ environment for 30 days, it was discharged at 0.1 C to 2.0 V (lithium-rich manganese-based cathode) or 2.8 V (lithium nickel cobalt manganese oxide cathode), and then charged to 4.8 V (lithium-rich manganese-based cathode) or 4.6 V (lithium nickel cobalt manganese oxide cathode), and the capacity of the lithium-ion battery was measured and the capacity retention rate was calculated.

[0098] Metal compatibility testing: At room temperature, the lithium-ion battery was charged to 4.8 V (lithium-rich manganese-based cathode) at a rate of 0.1 C. The battery was then disassembled, and the lithium metal deposited on the negative electrode was tested by scanning electron microscopy (SEM).

[0099] Positive electrode morphology test after cycling: At room temperature, the lithium-ion battery was charged and discharged at a rate of 0.1 C for 20 cycles. Then the battery was disassembled and the positive electrode particles were tested by scanning electron microscopy (SEM).

[0100] Coulomb efficiency test: assembly The battery was tested at room temperature with a current of 0.5 mA·cm⁻¹. 2 .

[0101] Symmetrical battery testing: assembly The battery was subjected to cycle testing at room temperature under conditions of 0.5 mA·cm⁻¹. 2 0.5 mAh·cm 2 .

[0102] Soft-pack battery assembly and testing: In the drying room, lithium copper composite strip, separator, and nickel cobalt manganese positive electrode sheet are stacked in a "Z" shape. After welding the tabs and sealing and filling with liquid, the battery is left to stand for 24 hours, fixed with a pressure mold, and placed in an explosion-proof box for performance testing.

[0103] Table 1

[0104] Table 2

[0105] Table 1 shows the test results of examples and comparative examples matched with lithium-rich manganese-based cathode materials; Table 2 shows the test results of examples and comparative examples matched with lithium nickel cobalt manganese oxide cathode materials. As can be seen from Tables 1 and 2, the lithium-ion battery using an oxyalkyl sulfonate solid high-voltage electrolyte exhibits significantly improved capacity retention after room temperature cycling, high temperature cycling, and high temperature storage tests compared to liquid electrolytes containing oxyalkyl sulfonates, electrolytes without oxyalkyl sulfonates, cyclic sulfonate electrolytes, and carbonate electrolytes. The oxyalkyl sulfonate solid high-voltage electrolyte prepared by in-situ polymerization eliminates the risk of combustion or even explosion caused by leakage or physical damage of liquid electrolytes, further improving the thermal stability and safety of the battery. In this invention, the oxyalkyl sulfonate solid electrolyte, while compatible with high-voltage window cathode materials, improves compatibility with lithium metal anodes. Furthermore, after decomposition, it can form a stable electrode-electrolyte interface film on the electrode surface of the lithium-ion battery, significantly suppressing side reactions between the electrolyte and the electrode, and improving the battery's cycle capacity retention.

[0106] Depend on Figure 1 It is known that the electrochemical window of the oxygen-containing alkyl sulfonate high-voltage solid electrolyte in this invention is higher than 5 V, due to... Figure 2 , Figure 3It is known that alkyl-containing sulfonate high-voltage solid electrolytes are well-suited for lithium-rich manganese-based cathodes and lithium nickel cobalt manganese oxide cathodes, exhibiting specific capacities of approximately 300 mAh / g and 220 mAh / g, respectively; Figure 4 , 5 It is known that the alkyl-containing sulfonate liquid electrolyte, when matched with lithium-rich manganese-based cathodes and lithium nickel cobalt manganese oxide cathodes, achieves specific capacities of approximately 270 mAh / g and 215 mAh / g, respectively; by in-situ polymerizing the electrolyte into a solid electrolyte, the battery's coulombic efficiency and discharge specific capacity are improved. Figure 6 , Figure 7 , Figure 8 As can be seen, in Example 1 of the present invention, the introduction of alkyl oxo groups into the sulfonate compound improved the compatibility between the sulfonate and the lithium metal anode, and the lithium metal deposition exhibited a compact, flat block structure. Figure 6 Comparative Example 3, without the introduction of alkyl groups, exhibits a porous dendritic lithium dendrite deposition morphology. Figure 7 Comparative Example 5, using cyclic sulfonate compounds, exhibited a cracked dendritic lithium dendrite deposition morphology. Figure 8 ). Figure 9 , Figure 10 , Figure 11 The image shows the SEM characterization of the NCM cathode material after 20 cycles at 0.1C. In Example 2, the introduction of alkyl oxometalates into the sulfonate compound enhanced the stability of the cathode material during cycling, and the cathode material remained intact without cracking. Figure 9 Comparative Example 4 (using sulfonate compounds without introduced oxygen alkyl groups) Figure 10 ) and Comparative Example 6 (using cyclic sulfonate compounds) Figure 11 The cathode material cracks after cycling, resulting in battery capacity loss and decreased cycle stability.

[0107] Figure 12 To apply the electrolytes of Example 1, Comparative Example 3, and Comparative Example 5 The coulombic efficiency graph of the batteries shows that the coulombic efficiency of Example 1 is 97.4%, that of Comparative Example 3 is 96.8%, and that of Comparative Example 5 is 93.6%. Compared with Comparative Examples 3 and 5, the electrolyte of Example 1 has a higher coulombic efficiency, indicating that the sulfonate solid electrolyte with introduced oxygen alkyl groups has higher compatibility with lithium metal, fewer side reactions, and increased battery cycle stability and capacity retention.

[0108] Figure 13 For the application of the electrolyte in Example 1 Symmetrical batteries can cycle stably for nearly 1800 hours. Figure 14To obtain the F / C ratio of the positive electrode interface film of the electrolytes in Example 2 and Comparative Example 4, XPS was used to characterize the positive electrode after 20 cycles. The test results showed that the positive electrode interface film of the electrolyte in Example 2 had a higher F / C ratio, proving that a more robust inorganic-rich interface film was formed, which helps to reduce the occurrence of side reactions at the electrolyte and positive electrode interface.

[0109] Figure 15 The diagram shows the capacity of the soft-pack battery in Application Example 2. The battery discharge capacity is 5.36 Ah, the discharge energy is 20.43 Wh, and the battery weight is 40.26 g. Substituting the above data into the energy density calculation formula (energy density = discharge energy / battery weight), we can obtain that the battery energy density is 507.5 Wh / kg.

[0110] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A high-voltage electrolyte, characterized in that, The mixture comprises a sulfonate compound, a lithium salt, a co-solvent, a polymer monomer, and an initiator; the mass ratio of the sulfonate compound, lithium salt, co-solvent, polymer monomer, and initiator is (1-20):1:(0.5-20):(0.1-15):(0.01-5), and the general chemical formula of the sulfonate compound is [insert formula here]. In the general structural formula, R1 is an alkyl group or alkyl halide containing 1-5 carbon atoms, and R2 is one of an oxoalkyl group or oxoalkyl halide containing at least one oxygen atom, a cyano-substituted product, or an unsaturated functional group substituted product.

2. The high-voltage electrolyte according to claim 1, characterized in that, The lithium salt is one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxalateborate, lithium difluorooxalateborate, lithium tetrafluoroborate, and lithium nitrate.

3. The high-voltage electrolyte according to claim 1, characterized in that, The co-solvent is one or more of the following: carbonate co-solvent, phosphate co-solvent, ether co-solvent, carboxylic acid ester co-solvent, nitrile co-solvent, sulfone co-solvent, and alkane co-solvent; The carbonate cosolvent includes one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and vinylene carbonate. The phosphate ester cosolvent includes one or more of trimethyl phosphate, triethyl phosphate, tributyl phosphate, triethyl fluorophosphate, and triethyl chlorophosphate. The ether cosolvents include one or more of the following: ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran, tetrahydropyran, 1,3-dioxopentane, 1,4-dioxane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, and 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether. The carboxylic acid ester cosolvents include one or more of the following: butyl formate, amyl formate, propyl acetate, butyl acetate, methyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, butyl fluoroformate, amyl fluoroformate, propyl fluoroacetate, butyl fluoroacetate, methyl fluoropropionate, propyl fluoropropionate, butyl fluoropropionate, methyl fluorobutyrate, and ethyl fluorobutyrate. The nitrile cosolvents include one or more of acetonitrile, propionitrile, valerate, glutaronitrile, adiponitrile, heptanonitrile, heptanonitrile, octanoic acid, and octanoic acid. The sulfone cosolvents include one or more of sulfolane, dimethyl sulfoxide and diethyl sulfoxide, and methyl ethyl sulfone; The alkane cosolvents include one or more of dichloromethane, hexafluorobenzene, difluorobenzene, o-fluorotoluene, m-fluorotoluene, and p-fluorotoluene.

4. The high-voltage electrolyte according to claim 1, characterized in that, The polymer monomers include one or more of diallyl carbonate, ethylene carbonate, N,N-methylenebisacrylamide, pentaerythritol tetraacrylate, polyethylene glycol diacrylate, and butyl acrylate; the initiator is an azo thermal initiator.

5. The method for preparing a high-voltage electrolyte according to any one of claims 1-4, characterized in that, The process includes the following steps: mixing a sulfonate compound, a lithium salt, and a co-solvent and stirring until a homogeneous and clear liquid is formed; then adding a polymer monomer and an initiator and stirring again until a homogeneous liquid is formed to obtain a high-voltage electrolyte.

6. A lithium-ion battery, comprising an electrolyte, a positive electrode, a negative electrode, and a separator, characterized in that, The electrolyte is the high-voltage electrolyte according to any one of claims 1-4.

7. The lithium-ion battery according to claim 6, characterized in that, The active material of the positive electrode includes one or more of the following: lithium-rich manganese-based, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

8. The lithium-ion battery according to claim 6, characterized in that, The negative electrode includes one or more of the following: lithium metal, graphite, silicon negative electrode, silicon-carbon negative electrode, silicon suboxide, lithium titanate, and materials without negative electrodes.

9. The lithium-ion battery according to claim 6, characterized in that, The diaphragm includes one or more of the following: polyethylene diaphragm, polypropylene diaphragm, PP / PE / PP three-layer composite diaphragm, ceramic / PE composite diaphragm, GF / A glass fiber diaphragm, GF / D glass fiber diaphragm, and GF / F glass fiber diaphragm.

10. The application of a high-voltage electrolyte as described in any one of claims 1-4 in the preparation of lithium-ion batteries.

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