Gel electrolyte composition, its injection method and lithium metal battery

Abstract

This application provides a gel electrolyte composition, its injection method, and a lithium metal battery. The gel electrolyte composition includes a first component, a second component, and a lithium salt. The first component includes a fluoroether compound, a fluorocarbonate, a fluorine-free ether compound, a siloxane additive, and optionally a film-forming additive. The second component includes a crosslinking agent monomer and a free radical initiator. Through the synergistic effect of the first component (including the fluoroether compound, fluorocarbonate, fluorine-free ether compound, siloxane additive, and optionally a film-forming additive) and the second component (including the crosslinking agent monomer and free radical initiator) and the lithium salt, the resulting gel electrolyte structure is more uniform and stable, effectively improving the lithium dendrite problem and interfacial side reaction problem in lithium metal batteries, and significantly enhancing the cycle stability and safety of lithium metal batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium metal battery technology, and more specifically, to a gel electrolyte composition, its injection method, and a lithium metal battery. Background Technology

[0002] With the rapid advancement of technology and the widespread adoption of electric vehicles, the market demand for rechargeable batteries with higher energy density is showing an increasing trend. Lithium metal batteries, as a cutting-edge energy storage technology, have become a research hotspot due to their high theoretical specific capacity (3860 mAh / g), high theoretical energy density, absence of memory effect, and low self-discharge rate, especially in fields pursuing high battery energy density. However, the high reactivity of lithium metal anodes and the formation of lithium dendrites have always been key obstacles hindering their commercial application. These problems not only affect battery performance but may also pose safety risks.

[0003] Electrolyte is a core component of battery systems, directly affecting battery capacity, internal resistance, cycle stability, and rate performance. To overcome the inherent challenges of lithium metal batteries, researchers have begun focusing on the development of in-situ gel electrolytes. These electrolytes can form a stable interface inside the battery, effectively reducing the number of free solvent molecules, thereby inhibiting lithium dendrite growth and enhancing battery safety. Simultaneously, they maintain high ionic conductivity comparable to traditional liquid electrolytes, significantly promoting improved cycle efficiency and safety performance of lithium metal batteries.

[0004] While existing lithium-ion battery technologies have made significant progress in energy density, power density, and cycle life, traditional lithium-ion batteries still have limitations for certain demanding applications, especially in electric vehicles and aerospace where higher energy density is required. Lithium metal, as an anode material, is considered key to breaking through the current energy density ceiling of lithium-ion batteries due to its excellent theoretical performance. However, the high reactivity of lithium metal makes it highly susceptible to side reactions when in contact with traditional electrolytes, leading to excessive electrolyte consumption, low coulombic efficiency, and the formation of lithium dendrites. These problems severely restrict the performance and safety of lithium metal batteries.

[0005] Therefore, developing gel electrolytes by combining in-situ solidification technology with liquid electrolytes has become an innovative solution for improving the performance of lithium metal batteries. In light of the above background, this invention aims to provide a gel electrolyte composition and a secondary electrolyte injection process, designed to improve the cycle stability and safety of lithium metal batteries and promote their widespread application in fields requiring high power and high energy density. To this end, this invention is proposed. Summary of the Invention

[0006] The main objective of this invention is to provide a gel electrolyte composition, its injection method, and a lithium metal battery to solve the problems of lithium dendrite formation, interfacial side reactions, and the resulting structural stability issues in traditional liquid electrolyte lithium metal batteries. The aim is to comprehensively improve the cycle stability and safety of lithium metal batteries and promote their widespread application in fields requiring high power and high energy density.

[0007] The gel electrolyte composition provided by this invention comprises a first component, a second component, and a lithium salt; wherein the first component includes a fluoroether compound, a fluorocarbonate, a fluorine-free ether compound, a siloxane additive, and optionally a film-forming additive; the second component includes a crosslinking agent monomer and a free radical initiator. Under the synergistic effect of the above components, the formed gel electrolyte is not only more uniform and stable, but also effectively improves the lithium dendrite problem and interfacial side reaction problem in lithium metal batteries, significantly enhancing the cycle stability and safety of lithium metal batteries.

[0008] Further, by weight percentage, the first component comprises: 1–60% fluoroether compound, 2–50% fluorocarbonate, 1–60% non-fluorinated ether compound; 0.01–10% siloxane additive, and 0–10% film-forming additive; in the second component, the crosslinking agent monomer is 1–10% of the weight of the first component; the free radical initiator is 0.01–5% of the weight of the crosslinking agent monomer; in the gel electrolyte composition, the concentration of lithium salt is 0.5–3 mol / L; preferably... The first component, by weight percentage, comprises: 20–60% fluoroether compounds, 20–40% fluorocarbonates, and 15–40% non-fluorinated ether compounds; 0.01–5% siloxane additives and 0.01–5% film-forming additives. In the second component, the crosslinking agent monomer accounts for 1–5% of the weight of the first component; the free radical initiator accounts for 0.01–2% of the weight of the crosslinking agent monomer. The concentration of lithium salt in the gel electrolyte composition is 0.5–3 mol / L. Controlling the content of each component in the gel electrolyte composition within the above ranges can better leverage the synergistic effect between the components, which is beneficial for further improving the electrochemical performance of the gel electrolyte and enhancing the cycle stability of lithium metal batteries.

[0009] Further, the fluorocarbonate is a cyclic fluorocarbonate and / or a chain fluorocarbonate; preferably, the fluorocarbonate is a blend of cyclic and chain fluorocarbonates; preferably, the weight ratio of cyclic to chain fluorocarbonates is 1:(0.5-5); more preferably, the weight ratio of cyclic to chain fluorocarbonates is 1:(1-3). When cyclic and chain fluorocarbonates are used in blend, and their weight ratio is controlled within the above-mentioned preferred range, the effect on improving the cycle stability of lithium metal batteries is also better.

[0010] Furthermore, cyclic fluorocarbonates have compounds with the structure shown in formula (Ⅰ):

[0011]

[0012] In equation (Ⅰ), R3, R4, R5, and R6 are each independently selected from H, F, C1 to C1. 10 Alkyl groups, C1-C 10 Fluoroalkyl, C2-C 10 alkenyl or C2-C 10 The fluoroalkenyl group, wherein at least one fluorine atom is present in R3, R4, R5, and R6; preferably, each of R3, R4, R5, and R6 is independently selected from H, F, C1-C5 alkyl or C1-C5 fluoroalkyl, and at least one fluorine atom is present in R3, R4, R5, and R6; more preferably, each of R3, R4, R5, and R6 is independently selected from H, F, methyl, ethyl, monofluoromethyl, difluoromethyl, or trifluoromethyl, and at least one fluorine atom is present in R3, R4, R5, and R6; most preferably, the cyclic fluorocarbonate has the structure shown in formula (A):

[0013]

[0014] And / or, chain fluorocarbonates having the structure shown in formula (II):

[0015]

[0016] In formula (II), R7 and R8 are each independently selected from H, F, C1 to C 10 Alkyl groups, C1-C 10 Fluoroalkyl, C2-C 10 alkenyl or C2-C 10 The fluoroalkenyl group, wherein R7 and R8 contain at least one fluorine atom; preferably, R7 and R8 are each independently selected from H, F, C1-C5 alkyl or C1-C5 fluoroalkyl, and R7 and R8 contain at least one fluorine atom; more preferably, R7 and R8 are each independently selected from H, F, methyl, ethyl, monofluoromethyl, difluoromethyl or trifluoromethyl, and R7 and R8 contain at least one fluorine atom; most preferably, the chain fluorocarbonate has the structure shown in formula (B):

[0017]

[0018] And / or, the fluoroether compound is a compound having the structure shown in formula (Ⅲ):

[0019]

[0020] In equation (Ⅲ), R1 and R2 are each independently selected from C1 to C2. 10 Alkyl groups, C1-C 10 Fluoroalkyl, C2-C 10 alkenyl or C2-C 10 The fluorinated alkenyl group, wherein R1 and R2 each contain at least one fluorine atom; preferably, R1 and R2 are each independently selected from C1 to C5 alkyl groups, and the alkyl group contains at least one fluorine atom; more preferably, R1 and R2 are each independently selected from methyl, ethyl, monofluoromethyl, difluoromethyl, trifluoromethyl, 1,1,2,2-tetrafluoroethyl, 1,1,2-trifluoroethyl, or trifluoromethylethyl; most preferably, the fluorinated ether compound has the structure shown in formula (C):

[0021]

[0022]

[0023] And / or, fluorine-free ether compounds are compounds having the structure shown in formula (Ⅳ):

[0024]

[0025] In equation (Ⅳ), R9 and R 10 Each is independently selected from C1 to C2. 10 Alkyl or C2-C 10 Alkoxyalkyl; more preferably, in formula (Ⅳ), R9 and R 10 Each alkyl group is independently selected from C1 to C5; more preferably, R9 and R 10 Each ether is independently selected from methyl, ethyl, propyl, isopropyl, or butyl; most preferably, the fluorine-free ether compound has the structure shown in formula (D):

[0026]

[0027] Further, the lithium salt is one or more selected from lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxalate borate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium difluorophosphate; preferably, the siloxane additive is vinyltrimethoxysilane and / or propenyltrimethoxysilane; preferably, the film-forming additive is lithium dioxalate borate, lithium difluorooxalate borate, lithium tetrafluoroborate, methane disulfonate, 4-trifluoromethyl vinyl carbonate, 1,3,2-dioxazolthiophene-2,2-dioxide, ethylene sulfite, vinylene carbonate, succinic anhydride, propylene sulfite, propenyl-1,3-sulfonyl lactone, bis(trifluoromethanesulfonate)... The composition contains at least one of the following: siloxane sulfate, lithium nitrate, N-methyl,butylpyrrolidine bis(trifluoromethanesulfonyl)imide, N-methyl,propylpiperidine bis(trifluoromethanesulfonyl)imide, 1,3-dioxane, 1,4-dioxane, 1,2-bis(cyanoethoxy)ethane, adiponitrile, 1,3,5-pentanetricarbonyl, transbutenedionitrile, and 1,2,3-tris(2-cyanoethoxy)propane; preferably, the free radical initiator is at least one of azobisisobutyronitrile, cyclohexanone peroxide, azobisisoheptanenitrile, tert-butyl hydroperoxide, and dimethyl azobisisobutyrate; preferably, the crosslinking agent monomer is at least one of N,N-methylenebisacrylamide, methacrylamide, N-ethylacrylamide, and cyclic acrylamide. Using one or more of the above-mentioned types of siloxane additives, film-forming additives, free radical initiators, and crosslinking agent monomers as components of the gel electrolyte composition is more effective in improving the electrochemical performance of the gel electrolyte.

[0028] Further, the gel electrolyte composition comprises, by weight percentage, a first component comprising: 49.5% fluoroether compound, 10% cyclic fluorocarbonate, 20% chain fluorocarbonate, 19.5% non-fluorinated ether compound; 0.5% siloxane additive, 0.5% film-forming additive; in the second component, the crosslinking agent monomer is 3% by weight of the first component; the free radical initiator is 2% by weight of the crosslinking agent monomer; the concentration of lithium salt in the gel electrolyte composition is 1.5 mol / L; or, by weight percentage, the first component comprises: 54% fluoroether compound, 8% cyclic fluorocarbonate, 22% chain fluorocarbonate, 15% non-fluorinated ether compound; 0.5% siloxane additive, 0.5% film-forming additive; in the second component, the crosslinking agent monomer is 3% by weight of the first component; the free radical initiator is 2% by weight of the crosslinking agent monomer; in the second component, the concentration of lithium salt is 1.5 mol / L; or, by weight percentage, the first component comprises: 54% fluoroether compound, 8% cyclic fluorocarbonate, 22% chain fluorocarbonate, 15% non-fluorinated ether compound; 0.5% siloxane additive, 0.5% film-forming additive, ... The first component comprises: alkane additives and 0.5% film-forming additives; in the second component, the crosslinking agent monomer is 3% of the weight of the first component; the free radical initiator is 2% of the weight of the crosslinking agent monomer; the concentration of lithium salt in the gel electrolyte composition is 1.5 mol / L; or, by weight percentage, the first component comprises: 49.5% fluoroether compounds, 10% cyclic fluorocarbonates, 20% chain fluorocarbonates, 19.5% non-fluorinated ether compounds; 0.5% siloxane additives and 0.5% film-forming additives; in the second component, the crosslinking agent monomer is 5% of the weight of the first component; the free radical initiator is 2% of the weight of the crosslinking agent monomer; the concentration of lithium salt in the gel electrolyte composition is 1.5 mol / L. The above scheme is exemplary. Controlling the content of each component in the gel electrolyte composition within the above-mentioned proportion range is beneficial for improving the stability of the gel electrolyte, thereby further improving the cycle stability and safety of lithium metal batteries.

[0029] According to a second aspect of the present invention, a method for injecting a gel electrolyte composition is also provided, the method comprising the steps of: separating the gel electrolyte composition into a first solution and a second solution, wherein the first solution comprises 80-92% of a fluoroether compound, 80-90% of a fluorocarbonate, 80-90% of a fluorine-free ether compound, 100% of a siloxane additive, 0-90% of a film-forming additive, 100% of a crosslinking agent monomer, and 100% of a free radical initiator; and the concentration of lithium salt in the first solution is 0.2-3 mol. The first solution comprises: a fluorinated ether compound, a fluorinated carbonate, a fluorine-free ether compound, a film-forming additive, and a lithium salt, wherein the concentration of the lithium salt in the second solution is 0.5 mol / L to 3.5 mol / L. The injection method includes the following steps: injecting the first solution into the electrochemical device for the first injection; subjecting the electrochemical device after the first injection to in-situ solidification and formation to obtain a pretreated electrochemical device; injecting the second solution into the pretreated electrochemical device, and sealing it under vacuum to complete the injection operation. This two-stage injection operation is beneficial for further improving the ionic conductivity of the gel electrolyte, improving interfacial contact, and enhancing the interfacial stability of the lithium metal battery.

[0030] Further, the gel electrolyte composition is divided into a first solution and a second solution. The first solution comprises 85-92% of a fluoroether compound, 80-85% of a fluorocarbonate, 80-85% of a fluorine-free ether compound, 100% of a siloxane additive, 0-90% of a film-forming additive, 100% of a crosslinking agent monomer, and 100% of a free radical initiator; and the concentration of lithium salt in the first solution is 0.2-3 mol / L. The second solution comprises the remainder of the fluoroether compound, the remainder of the fluorocarbonate, the remainder of the fluorine-free ether compound, the remainder of the film-forming additive, and the remainder of the lithium salt, and the concentration of lithium salt in the second solution is 0.5 mol / L-3.5 mol / L. The gel electrolyte formed after curing using the above-described injection method can further improve interfacial contact, form a stable interface, and reduce the internal resistance of the lithium metal battery, thereby contributing to further improvement in the cycle performance of the lithium metal battery.

[0031] Furthermore, the in-situ solidification and formation steps include: after the electrochemical device has undergone the first liquid injection, it is allowed to stand, and then charged at a constant current to 50-70% of its full charge state to complete the in-situ solidification and formation; preferably, the standing time is 12-24 hours; preferably, the constant current charging is carried out under pressure P and temperature T conditions, wherein 0.4MPa≤P≤1.2MPa and 50≤T≤80℃; preferably, the constant current charging rate is 0.04C-0.2C. The above-mentioned in-situ solidification and formation conditions can further improve the interfacial stability of the gel electrolyte, and improve the battery capacity and cycle stability.

[0032] According to a third aspect of the present invention, a lithium metal battery is also provided, wherein the electrolyte of the lithium metal battery is made from the above-mentioned gel electrolyte composition; or, the electrolyte of the lithium metal battery is formed by an injection method of the above-mentioned gel electrolyte composition.

[0033] The gel electrolyte composition provided by this invention, in the first component comprising a fluoroether compound, a fluorocarbonate, a fluorine-free ether compound, a siloxane additive, and optionally a film-forming additive, and a second component comprising a crosslinking agent monomer and a free radical initiator, and the synergistic effect of a lithium salt, forms a gel electrolyte that not only has the advantages of being more uniform and stable, but also effectively improves the problem of lithium dendrite formation and interfacial side reactions in lithium metal batteries, and has a significant effect on improving the cycle stability and safety of lithium metal batteries. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0035] As described in the background section, while existing lithium-ion battery technologies have made significant progress in energy density, power density, and cycle life, traditional lithium-ion batteries still have limitations for certain demanding applications, especially in electric vehicles and aerospace where higher energy density is required. Lithium metal, as an anode material, is considered key to breaking through the current energy density ceiling of lithium-ion batteries due to its excellent theoretical performance. However, the high reactivity of lithium metal makes it prone to side reactions when in contact with traditional electrolytes, leading to excessive electrolyte consumption, low coulombic efficiency, and the formation of lithium dendrites. These problems severely restrict the performance and safety of lithium metal batteries.

[0036] To address the aforementioned problems, the present invention provides a gel electrolyte composition comprising a first component, a second component, and a lithium salt; wherein the first component comprises a fluoroether compound, a fluorocarbonate, a fluorine-free ether compound, a siloxane additive, and optionally a film-forming additive; and the second component comprises a crosslinking agent monomer and a free radical initiator.

[0037] The gel electrolyte composition provided by this invention uses fluoroether compounds, fluorocarbonates, fluorine-free ether compounds, siloxane additives, and optionally film-forming additives as the first component, and crosslinking agent monomers and free radical initiators as the second component. In addition, it also includes lithium salts. Through the synergistic effect of the above components, the formed gel electrolyte is not only more uniform and stable, but also effectively improves the lithium dendrite problem and interfacial side reaction problem in lithium metal batteries, significantly enhancing the cycle stability and safety of lithium metal batteries.

[0038] In this gel electrolyte composition, the fluoroether compound not only does not readily react with reactive lithium metal, but also forms a dense protective film at the positive electrode, improving the interfacial stability of the lithium metal battery. Simultaneously, the fluoroether compound contains groups with large dipole moments, which enhances the miscibility between the components in the gel electrolyte composition, facilitating the formation of a more uniform and stable gel electrolyte solution. Furthermore, the fluoroether compound in the gel electrolyte composition also acts as a "diluent," reducing the lithium salt concentration, decreasing free solvent molecules, suppressing side reactions, and improving lithium ion transport within the gel electrolyte.

[0039] Fluorinated carbonates in the gel electrolyte composition can enhance the oxidation resistance of the formed gel electrolyte on the positive electrode side. Furthermore, the presence of fluorinated carbonates in the gel electrolyte also forms an organic polymer solid electrolyte interphase (SEI) containing carbon and oxygen, and a fluorine-containing inorganic solid electrolyte interphase (SEI) on the surface of the lithium metal anode. The synergistic effect of these two types of SEI layers further enhances the stability and protection of the anode surface, effectively suppressing lithium dendrite growth and reducing interfacial side reactions. This significantly promotes the improvement of the interfacial stability between the gel electrolyte and the lithium metal battery anode.

[0040] The fluorine-free ether compounds in the gel electrolyte composition exhibit good miscibility with the other components and good stability to the lithium metal anode. Including them as a component allows for better interaction with the other components, resulting in a more uniform and stable gel electrolyte solution. Furthermore, the presence of fluorine-free ether compounds can further reduce the decomposition and side reactions of fluorinated carbonate solutions in lithium metal batteries, thus contributing to improved stability of the gel electrolyte.

[0041] Furthermore, the lithium salt in the gel electrolyte composition is thoroughly mixed with other components, providing lithium ions in the electrolyte. The synergistic effect between the components promotes electron migration during the operation of the lithium metal battery. In addition, the lithium salt can also form a negative electrode protective film on the negative electrode, thereby further improving the cycle performance of the lithium metal battery.

[0042] The gel electrolyte composition also includes siloxane additives and optionally film-forming additives. The siloxane additives can directionally remove harmful byproducts generated by the violent decomposition of lithium salts and other components during the in-situ solidification of the gel electrolyte composition solution, improving the stability of the system during the in-situ solidification and formation of the gel electrolyte composition, and better forming a uniform and stable gel electrolyte. Furthermore, the siloxane additives can form a silicon-containing inorganic positive electrode electrolyte interface (CEI) at the positive electrode of the lithium metal battery. This, combined with the synergistic effect of the organic polymer solid electrolyte interface layer (SEI) containing carbon and oxygen elements formed by fluorinated carbonates on the surface of the lithium metal negative electrode, further enhances the stability between the gel electrolyte and the lithium metal battery interface.

[0043] The crosslinking monomer and free radical initiator in the gel electrolyte composition are compatible with fluoroether compounds, fluorocarbonates, and non-fluorinated ether compounds, and can form a homogeneous mixed solution after thorough mixing. The mixed solution undergoes a polymerization reaction at high temperature to form a gel electrolyte with uniform composition. The presence of the crosslinking monomer and free radical initiator can further improve the stability of the positive and negative electrode interfaces and enhance the cycle performance of lithium metal batteries.

[0044] In summary, the fluoroether compounds, fluorocarbonates, fluorine-free ether compounds, siloxane additives, film-forming additives, crosslinking monomers, free radical initiators, and lithium salts in the gel electrolyte composition of the present invention have different properties. Under the synergistic effect of the various components in the above gel electrolyte composition, the formed gel electrolyte not only has the advantages of being more uniform and stable, but also effectively improves the lithium dendrite problem and interfacial side reaction problem in lithium metal batteries. The gel electrolyte composition of the above formulation has a good effect on improving the cycle stability and safety of lithium metal batteries.

[0045] In a preferred embodiment, the first component comprises, by weight percentage: 1-60% of a fluoroether compound, 2-50% of a fluorocarbonate, 1-60% of a fluorine-free ether compound; 0.01-10% of a siloxane additive, and 0-10% of a film-forming additive; in the second component, the crosslinking agent monomer is 1-10% of the weight of the first component; the free radical initiator is 0.01-5% of the weight of the crosslinking agent monomer; and in the gel electrolyte composition, the concentration of the lithium salt is 0.5-3 mol / L. In the gel electrolyte composition, fluoroether compounds facilitate the formation of a protective film, enhance miscibility and dilute lithium salts, and improve interfacial stability; fluorocarbonates improve oxidation resistance and synergistically form an SEI layer, inhibiting lithium dendrite formation and stabilizing the negative electrode interface; fluorine-free ether compounds improve lithium salt solubility, reduce side reactions, and enhance stability; siloxanes and film-forming additives remove curing byproducts and improve interfacial performance; lithium salts promote electron migration and form a negative electrode protective film; crosslinking agents and initiators ensure uniform and sufficient curing, collectively improving battery energy density and cycle safety. The effects of each component are complementary and work together to improve the cycle stability and safety of lithium metal batteries. Controlling the content of each component in the gel electrolyte composition within the above-mentioned range can better leverage the synergistic effects between components, which is beneficial for further improving the electrochemical performance of the gel electrolyte and enhancing the cycle stability of lithium metal batteries.

[0046] Preferably, by weight percentage, the first component comprises: 20-60% fluoroether compound, 20-50% fluorocarbonate, 10-60% fluorine-free ether compound; 0.01-10% siloxane additive, and 0-10% film-forming additive; in the second component, the crosslinking agent monomer is 1-10% of the weight of the first component; the free radical initiator is 0.01-5% of the weight of the crosslinking agent monomer; and in the gel electrolyte composition, the concentration of lithium salt is 0.5-3 mol / L. Controlling the content of each component in the gel electrolyte composition within the above-mentioned preferred ranges results in better synergistic effects between the components, which is beneficial for improving the electrochemical performance of the gel electrolyte and enhancing the cycle stability of the lithium metal battery.

[0047] More preferably, by weight percentage, the first component comprises: 20–60% of a fluoroether compound, 20–40% of a fluorocarbonate, and 15–40% of a fluorine-free ether compound; 0.01–5% of a siloxane additive and 0.01–5% of a film-forming additive; in the second component, the crosslinking agent monomer accounts for 1–5% of the weight of the first component; the free radical initiator accounts for 0.01–2% of the weight of the crosslinking agent monomer; and in the gel electrolyte composition, the concentration of lithium salt is 0.5–3 mol / L. Controlling the content of each component in the gel electrolyte composition within the above ranges results in a better overall improvement effect and better cycle stability of the lithium metal battery.

[0048] In a preferred embodiment, the fluorocarbonate is a cyclic fluorocarbonate and / or a chain fluorocarbonate; more preferably, it is a blend of cyclic and chain fluorocarbonates. The cyclic or chain fluorocarbonates in the fluorocarbonate can form an organic polymer SEI layer containing carbon and oxygen elements and a fluorine-containing inorganic SEI layer on the surface of the lithium metal anode, inhibiting lithium dendrite growth and reducing side reactions. The combined use of cyclic and chain fluorocarbonates, with their synergistic effect, can improve the kinetic performance of the gel electrolyte, thereby further enhancing the cycle stability of the lithium metal battery. Preferably, the weight ratio of cyclic fluorocarbonate to chain fluorocarbonate is 1:(0.5-5), specifically, for example: 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or any weight ratio between any of the above ratios. Controlling the compounding ratio of cyclic fluorocarbonate and chain fluorocarbonate within the above range is beneficial to further improve the kinetic performance in the gel electrolyte. More preferably, the weight ratio of cyclic fluorocarbonate to chain fluorocarbonate is 1:(1-3), specifically, for example: 1:1, 1:1.3, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3, or any weight ratio between any of the above ratios. When the weight ratio of cyclic fluorocarbonate to chain fluorocarbonate is within the above-mentioned preferred range, the above effects are even better, and the effect on improving the cycle stability of lithium metal batteries is also better.

[0049] In a preferred embodiment, the cyclic fluorocarbonate has a compound with the structure shown in formula (Ⅰ):

[0050]

[0051] In equation (Ⅰ), R3, R4, R5, and R6 are each independently selected from H, F, C1 to C1. 10 Alkyl groups, C1-C 10 Fluoroalkyl, C2-C 10 alkenyl or C2-C 10The cyclic fluorocarbonate has a fluorinated alkenyl group, and at least one fluorine atom is present in R3, R4, R5, and R6. Cyclic fluorocarbonates with the above structure exhibit better compatibility with lithium salts in the gel electrolyte composition, enabling better formation of an organic polymer solid electrolyte interphase (SEI) containing carbon and oxygen elements and a fluorine-containing inorganic solid electrolyte interphase (SEI) on the surface of the lithium metal anode, thereby improving the interfacial stability between the gel electrolyte and the lithium metal battery anode. Preferably, R3, R4, R5, and R6 are each independently selected from H, F, C1-C5 alkyl groups or C1-C5 fluoroalkyl groups, and at least one fluorine atom is present in R3, R4, R5, and R6; more preferably, R3, R4, R5, and R6 are each independently selected from H, F, methyl, ethyl, monofluoromethyl, difluoromethyl, or trifluoromethyl groups, and at least one fluorine atom is present in R3, R4, R5, and R6. Cyclic fluorocarbonate structures within the preferred range provide even better results. Most preferably, the cyclic fluorocarbonate has the structure shown in formula (A):

[0052]

[0053] And / or, chain fluorocarbonates having the structure shown in formula (II):

[0054]

[0055] In formula (II), R7 and R8 are each independently selected from H, F, C1 to C 10 Alkyl groups, C1-C 10 Fluoroalkyl, C2-C 10 alkenyl or C2-C 10 The fluorocarbonate has a fluoroalkenyl group, and R7 and R8 contain at least one fluorine atom. The chain fluorocarbonate with the above structure has a lower viscosity and can synergistically act with cyclic fluorocarbonates to improve the kinetic performance of the gel electrolyte and enhance the cycle stability of the lithium metal battery. Preferably, R7 and R8 are each independently selected from H, F, C1-C5 alkyl groups or C1-C5 fluoroalkyl groups, and R7 and R8 contain at least one fluorine atom; more preferably, R7 and R8 are each independently selected from H, F, methyl, ethyl, monofluoromethyl, difluoromethyl or trifluoromethyl groups, and R7 and R8 contain at least one fluorine atom; the chain fluorocarbonate structure within the preferred range provides even better results. Most preferably, the chain fluorocarbonate has the structure shown in formula (B):

[0056]

[0057] And / or, the fluoroether compound is a compound having the structure shown in formula (Ⅲ):

[0058]

[0059] In equation (Ⅲ), R1 and R2 are each independently selected from C1 to C2. 10 Alkyl groups, C1-C 10 Fluoroalkyl, C2-C 10 alkenyl or C2-C 10 The fluorinated alkenyl group, wherein R1 and R2 contain at least one fluorine atom; the fluorinated ether compound having the above structure has better miscibility with the composition and can better form a dense protective film on the positive electrode, effectively improving the interfacial stability of lithium metal batteries and the transport of lithium ions in gel electrolytes. Preferably, R1 and R2 are each independently selected from C1 to C5 alkyl groups, and the alkyl group contains at least one fluorine atom; more preferably, R1 and R2 are each independently selected from methyl, ethyl, monofluoromethyl, difluoromethyl, trifluoromethyl, 1,1,2,2-tetrafluoroethyl, 1,1,2-trifluoroethyl, or trifluoromethylethyl; the above effects are better with fluorinated ether compound structures within the preferred range. Most preferably, the fluorinated ether compound has the structure shown in formula (C):

[0060]

[0061] And / or, fluorine-free ether compounds are compounds having the structure shown in formula (Ⅳ):

[0062]

[0063] In equation (Ⅳ), R9 and R 10 Each is independently selected from C1 to C2. 10 Alkyl or C2-C 10 Alkoxyalkyl; more preferably, in formula (Ⅳ), R9 and R 10 Each alkyl group is independently selected from C1 to C5. Fluorine-free ether compounds having the above structure can better dissolve lithium salts, improve the decomposition and side reactions of fluorocarbonate solutions in lithium metal batteries, and further enhance the stability of the gel electrolyte. More preferably, R9 and R... 10 Each ether is independently selected from methyl, ethyl, propyl, isopropyl, or butyl; fluorine-free ether structures within the preferred range are more advantageous. Most preferably, the fluorine-free ether compound has the structure shown in formula (D):

[0064]

[0065] For example, but not limitingly, the lithium salt is one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxalateborate, lithium difluorooxalateborate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium difluorophosphate. This application does not impose strict limitations on the type of lithium salt, but the use of the above-mentioned lithium salts is more effective in improving the electrochemical performance of the gel electrolyte and is more suitable for use in the gel electrolyte system of this application. Preferably, the siloxane additive is vinyltrimethoxysilane and / or propenyltrimethoxysilane; preferably, the film-forming additive is lithium dioxalatoborate, lithium difluorooxalatoborate, lithium tetrafluoroborate, methylene disulfonate, 4-trifluoromethyl vinyl carbonate, 1,3,2-dioxazolthiophene-2,2-dioxide, ethylene sulfite, vinylene carbonate, succinic anhydride, propylene sulfite, propenyl-1,3-sulfonyl lactone, bis(trimethylsilyl)sulfate, lithium nitrate, N-methyl,butylpyrrolidine bis(trifluoromethanesulfonyl)imide, N-methyl,propylpiperidine bis(trifluoromethanesulfonyl)imide. The composition contains at least one of the following: fluoromethanesulfonylimide salt, 1,3-dioxane, 1,4-dioxane, 1,2-bis(cyanoethoxy)ethane, adiponitrile, 1,3,5-pentanetricarbonyl nitrile, transbutenedionitrile, and 1,2,3-tris(2-cyanoethoxy)propane; preferably, the free radical initiator is at least one of azobisisobutyronitrile, cyclohexanone peroxide, azobisisoheptanenitrile, tert-butyl hydroperoxide, and dimethyl azobisisobutyrate; preferably, the crosslinking agent monomer is at least one of N,N-methylenebisacrylamide, methacrylamide, N-ethylacrylamide, and cyclic acrylamide. Using one or more of the above-mentioned types of siloxane additives, film-forming additives, free radical initiators, and crosslinking agent monomers as components of the gel electrolyte composition is more effective in improving the electrochemical performance of the gel electrolyte.

[0066] In a preferred embodiment, the gel electrolyte composition comprises, by weight percentage, a first component comprising: 49.5% of a fluoroether compound, 10% of a cyclic fluorocarbonate, 20% of a chain fluorocarbonate, and 19.5% of a non-fluorinated ether compound; 0.5% of a siloxane additive and 0.5% of a film-forming additive; in the second component, a crosslinking agent monomer comprises 3% of the weight of the first component; a free radical initiator comprises 2% of the weight of the crosslinking agent monomer; and the concentration of the lithium salt in the gel electrolyte composition is 1.5 mol / L; or, by weight percentage, the first component comprises: 54% of a fluoroether compound, 8% of a cyclic fluorocarbonate, 22% of a chain fluorocarbonate, and 15% of a non-fluorinated ether compound; 0.5% of a siloxane additive and 0.5% of a film-forming additive; The first component comprises 49.5% fluoroether compounds, 10% cyclic fluorocarbons, 20% chain fluorocarbons, and 19.5% non-fluorinated ether compounds; 0.5% siloxane additives and 0.5% film-forming additives; the second component comprises 3% crosslinking agent monomers and 2% free radical initiators; the lithium salt concentration in the gel electrolyte composition is 1.5 mol / L. Alternatively, by weight percentage, the first component comprises: 49.5% fluoroether compounds, 10% cyclic fluorocarbons, 20% chain fluorocarbons, and 19.5% non-fluorinated ether compounds; 0.5% siloxane additives and 0.5% film-forming additives; the second component comprises 5% crosslinking agent monomers and 2% free radical initiators; the lithium salt concentration in the gel electrolyte composition is 1.5 mol / L. The above scheme is exemplary. Controlling the content of each component in the gel electrolyte composition within the above-mentioned proportion range is beneficial for improving the stability of the gel electrolyte, thereby further improving the cycle stability and safety of lithium metal batteries.

[0067] According to another aspect of the present invention, a method for injecting the above-mentioned gel electrolyte composition is also provided, wherein the gel electrolyte composition is divided into a first solution and a second solution, wherein the first solution comprises 80-92% of a fluoroether compound, 80-90% of a fluorocarbonate, 80-90% of a fluorine-free ether compound, 100% of a siloxane additive, 0-90% of a film-forming additive, 100% of a crosslinking agent monomer, and 100% of a free radical initiator in the gel electrolyte composition; and the concentration of lithium salt in the first solution is 0.2-3 mol / L. L; the second solution comprises: the remainder of fluoroether compound, the remainder of fluorocarbonate, the remainder of fluorine-free ether compound, the remainder of film-forming additive, and the remainder of lithium salt, wherein the concentration of lithium salt in the second solution is 0.5 mol / L to 3.5 mol / L; the injection method comprises the following steps: injecting the first solution into the electrochemical device for the first injection; solidifying and forming the electrochemical device after the first injection in situ to obtain a pretreated electrochemical device; injecting the second solution into the pretreated electrochemical device and sealing it under vacuum to complete the injection operation.

[0068] The gel electrolyte composition injection method provided by the present invention involves two injection operations. First, the gel electrolyte composition provided by the present invention is distributed in the specific manner described above to obtain a first solution and a second solution. Then, the first solution is injected into an electrochemical device, and after in-situ solidification and formation, a second injection is performed. After the two injections are completed, the solution is vacuum sealed to complete the injection operation.

[0069] The first solution in the injection method proposed in this application comprises a gel electrolyte composition containing: 80-92% fluoroether compound, 80-90% fluorocarbonate, 80-90% non-fluorinated ether compound, 100% siloxane additive, 0-90% film-forming additive, 100% crosslinking agent monomer, and 100% free radical initiator; and the concentration of lithium salt in the first solution is 0.2-3 mol / L. The above components can undergo crosslinking polymerization, followed by in-situ curing and formation processes to form a gel electrolyte layer. The second solution in the injection method proposed in this application comprises: the remainder of fluoroether compound, the remainder of fluorocarbonate, the remainder of non-fluorinated ether compound, the remainder of film-forming additive, and the remainder of lithium salt, and the concentration of lithium salt in the second solution is 0.5 mol / L to 3.5 mol / L. After in-situ curing and formation of the first solution, the components in the first solution undergo polymerization to form a crosslinked semi-solid gel electrolyte, upon which the second solution is injected. The second liquid injection exists in the electrolyte region of lithium metal in liquid form, which further fills the interfacial voids and improves interfacial contact.

[0070] Specifically, the first solution contains a relatively high proportion of fluorinated ether compounds, etc. Under the synergistic effect of these compounds, the first solution exhibits low viscosity. The gel electrolyte formed from this first solution has better wettability for the separator, positive electrode, and negative electrode in the lithium metal battery. The resulting gel electrolyte has a smoother and more stable interface, which helps reduce the internal resistance of the gel electrolyte. Furthermore, the presence of siloxane additives in the first solution can absorb byproducts generated during the curing process of the electrolyte, such as solvents and lithium salts, reducing damage to the positive and negative electrode sheets during gel electrolyte curing and formation, further improving the cycle stability and safety performance of the battery. Furthermore, the second solution contains the remainder of fluorinated ether compounds, fluorinated carbonates, non-fluorinated ether compounds, film-forming additives, and lithium salts. Under the synergistic effect of these compounds, not only can the oxidation resistance of the electrolyte on the positive electrode side be guaranteed and the presence of free solvent be reduced, but the interfacial stability between the gel electrolyte and the lithium metal negative electrode can also be further improved. The presence of film-forming additives in the second solution can further stabilize the electrolyte interface.

[0071] The two injection operations described above involve adding a second solution to the gel electrolyte formed by the in-situ solidification and formation of the first solution. This second solution fills interfacial gaps, improves interfacial contact, and avoids the problem of excessively high local current density caused by uneven contact during the solidification process. This, in turn, enhances ion transport pathways, reduces polarization, and improves the cycle stability of the lithium metal battery. Simultaneously, after being injected into the electrochemical device, the second solution can also fill in unreacted areas in the cross-linked network through wetting, further improving the interfacial uniformity of the electrolyte and enhancing battery cycle performance. Controlling the content of each component in the first and second solutions within the aforementioned ranges is beneficial for achieving better internal resistance and interfacial states in the lithium metal battery. It also avoids damage to the gel structure caused by excessive liquid electrolyte. Furthermore, controlling the concentrations of the first and second solutions within the aforementioned ranges during the injection process further improves their conductivity and wettability. This two-stage injection operation further enhances the ionic conductivity of the gel electrolyte, improves interfacial contact, and increases the interfacial stability of the lithium metal battery.

[0072] Preferably, the lithium salt concentration in the first solution is lower than the lithium salt concentration in the second solution. Controlling the lithium salt concentration ratio in the first and second solutions within the above-mentioned preferred range and controlling their relative concentrations allows both solutions to have good conductivity and wettability. Furthermore, it avoids the adverse effects of excessive free solvent in the second solution on the interfacial stability of the gel electrolyte formed in the first solution, thus improving the interfacial uniformity of the gel electrolyte and ultimately enhancing the cycle performance of the lithium metal battery.

[0073] In a preferred embodiment, the gel electrolyte composition is divided into a first solution and a second solution. The first solution comprises 85-92% of a fluoroether compound, 80-85% of a fluorocarbonate, 80-85% of a non-fluorinated ether compound, 100% of a siloxane additive, 0-90% of a film-forming additive, 100% of a crosslinking agent monomer, and 100% of a free radical initiator in the gel electrolyte composition. The concentration of lithium salt in the first solution is 0.2-3 mol / L. The second solution comprises the remainder of the fluoroether compound, the remainder of the fluorocarbonate, the remainder of the non-fluorinated ether compound, the remainder of the film-forming additive, and the remainder of the lithium salt. The concentration of lithium salt in the second solution is 0.5 mol / L to 3.5 mol / L.

[0074] Through extensive experimentation, the inventors creatively discovered that increasing the proportion of fluorinated ether compounds in the first solution and correspondingly decreasing the proportion of fluorinated carbonates or fluorine-free ether compounds in the first solution improves the electrolyte injection effect. This is likely because the first solution under the aforementioned ratio conditions exhibits better wettability for the separator, positive electrode, and negative electrode in the lithium metal battery. The gel electrolyte formed after solidification can further improve interfacial contact, form a stable interface, and reduce the internal resistance of the lithium metal battery, thereby contributing to further improvements in the cycle performance of the lithium metal battery.

[0075] In a preferred embodiment, the in-situ solidification and formation steps include: after the electrochemical device has undergone the first electrolyte injection, it is allowed to stand, then charged at a constant current to 50-70% of its full charge state, thus completing the in-situ solidification and formation. Due to its high reactivity and low density, the lithium metal anode undergoes significant volume expansion under high temperature and high-rate charge / discharge conditions, leading to repeated formation and rupture of the SEI at the anode interface, and resulting in the formation of lithium dendrites, threatening the battery's safety performance. In the above-mentioned in-situ solidification and formation operation, the solidification of the gel electrolyte and the formation of the battery are carried out simultaneously, which helps to improve the smoothness and uniformity of the in-situ solidification and form a more stable and uniform lithium metal deposition.

[0076] Preferably, the settling time is 12–24 hours. Preferably, constant current charging is performed under pressure P and temperature T conditions, where 0.4 MPa ≤ P ≤ 1.2 MPa and 50 ≤ T ≤ 80 °C. Controlling the pressure during constant current charging within the above range during in-situ curing and formation operations can further improve the wettability of the gel electrolyte and reduce its internal resistance. It can also effectively shorten the contact distance between the gel electrolyte and the positive and negative electrodes, forming a more uniform interface contact. Furthermore, controlling the pressure during constant current charging within the above range during in-situ curing and formation operations can further avoid the volume expansion of lithium metal during formation due to insufficient pressure, which could affect the battery's safety performance; and the damage to the battery structure caused by excessive pressure, making it difficult to form a uniform electrolyte interface. Furthermore, controlling the temperature during constant current charging within the above range can further improve the curing effect of the gel electrolyte, facilitating full curing of the electrolyte and resulting in a more stable interface. Simultaneously, it also helps avoid the decomposition of substances easily caused by excessively high temperatures, further preventing the generation of corrosive byproducts and large amounts of gas that could lead to battery capacity decay. Preferably, the constant current charging rate is 0.04C to 0.2C. During the above-mentioned in-situ solidification and formation process, lithium metal is deposited on the negative electrode. Controlling the constant current charging rate within the above range can further improve the lithium dendrite phenomenon, which is conducive to the formation of a uniform lithium metal deposition layer, further improves the interfacial stability of the gel electrolyte, and also increases the battery capacity.

[0077] According to a fourth aspect of the present invention, a lithium metal battery is also provided, wherein the electrolyte of the lithium metal battery is made from the above-described gel electrolyte composition; or, the electrolyte of the lithium metal battery is formed by an injection method of the above-described gel electrolyte composition.

[0078] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0079] It should be further noted that in the embodiments and comparative examples described in this application, the fluoroether compounds used have the structure shown in formula (C); the cyclic fluorocarbonates have the structure shown in formula (A); the chain fluorocarbonates have the structure shown in formula (B); the fluorine-free ether compounds have the structure shown in formula (D); the lithium salts have the structure shown in formula (E); the siloxane additive is vinyltrimethoxysilane; the film-forming additive is LiNO3; the crosslinking agent monomer is N,N-methylenebisacrylamide; and the free radical initiator is azobisisobutyronitrile. The specific structures are as follows:

[0080]

[0081] Example 1

[0082] (I) Solution Preparation

[0083] The gel electrolyte composition comprises: a fluoroether compound, a cyclic fluorocarbonate, a chain fluorocarbonate, a fluorine-free ether compound, a siloxane additive, and a film-forming additive as the first component, wherein, by weight percentage, the cyclic fluorocarbonate accounts for 10%, the chain fluorocarbonate accounts for 20%, the fluorocarbonate accounts for 49.5%, the fluorine-free ether compound accounts for 19.5%, the siloxane additive accounts for 0.5%, and the film-forming additive accounts for 0.5%; the crosslinking agent monomer accounts for 3% of the weight of the first component; the free radical initiator accounts for 2% of the weight of the crosslinking agent monomer; and the concentration of lithium salt in the gel electrolyte composition is 1.5 mol / L.

[0084] The gel electrolyte composition of the above components is designated as gel electrolyte composition one, and is dispensed into a first solution and a second solution. The first solution and the second solution are dispensed using a first injection method, specifically:

[0085] The first solution comprises 88% of a fluoroether compound, 80% of a cyclic fluorocarbonate, 80% of a chain fluorocarbonate, 85% of a fluorine-free ether compound, 100% of a siloxane additive, 100% of a crosslinking agent monomer, and 100% of a free radical initiator in the gel electrolyte composition; and the concentration of lithium salt in the first solution is 1.3 mol / L.

[0086] The second solution comprises: the remainder of fluoroether compounds, the remainder of cyclic fluorocarbonates, the remainder of chain fluorocarbonates, the remainder of fluorine-free ether compounds, the remainder of film-forming additives, and the remainder of lithium salts; the concentration of lithium salts in the second solution is 2 mol / L.

[0087] (II) Preparation of Lithium Metal Batteries

[0088] Preparation of positive electrode: The positive electrode active material is single-crystal lithium nickel cobalt manganese oxide (LiNiO2). 0.88 Co 0.07 Mn 0.05 O2), conductive agent (Super P conductive carbon), and binder (polyvinylidene fluoride) were mixed in a weight ratio of approximately 97.9:1.1:1. NMP (N-methylpyrrolidone) was added, and the mixture was stirred in a vacuum mixer until the system was homogeneous, resulting in a positive electrode slurry with a solid content of 73%. The positive electrode slurry was uniformly coated onto a positive electrode current collector aluminum foil (aluminum foil thickness of 15μm) with a thickness of 56μm, dried, and then cold-pressed, cut, and slit. Finally, it was dried under vacuum at 90℃ for about 6 hours to obtain the positive electrode sheet.

[0089] Preparation of the negative electrode sheet: Lithium metal is bonded to an 8μm thick copper foil negative electrode current collector using a physical rolling process. By adjusting the roller pressure, lithium is coated on one side of the copper current collector, controlling the lithium layer thickness to 50μm. After cutting and slitting, the negative electrode sheet is obtained and stored in a dry argon atmosphere glove box for later use.

[0090] Lithium metal separator: Polyethylene (PE) with a thickness of 25μm is used as the separator.

[0091] Inject in stages:

[0092] The above-obtained positive electrode, lithium metal separator, and negative electrode are stacked in sequence, and after welding the tabs, they are placed in the outer packaging aluminum-plastic film and sealed on the top side to obtain an electrochemical device for liquid injection.

[0093] The first solution is injected into the electrochemical device for the first injection.

[0094] The electrochemical device after the first liquid injection is then subjected to in-situ curing and formation to obtain a pretreated electrochemical device. The in-situ curing and formation operation is performed using the following method, which is designated as In-situ Curing and Formation Method One. Specifically, the operation of In-situ Curing and Formation Method One includes: allowing the electrochemical device after the first liquid injection to stand for 12 hours, then charging it at a constant current to 50% of its full charge under pressure P and temperature T conditions to complete the in-situ curing and formation; wherein P is 1 MPa, T is 70°C, and the constant current charging rate is 0.1C.

[0095] The second solution is injected into the pretreatment electrochemical device and sealed under vacuum to complete the injection operation. After aging and capacity testing, the resulting electrochemical device yields a lithium metal battery.

[0096] It should be noted that the differences between the embodiments and comparative examples in this application and Example 1 in the preparation of lithium metal batteries lie in the gel electrolyte composition, the liquid injection method, and the in-situ curing and formation method. To more clearly compare their effects, the differences in the lithium metal battery preparation process compared with Example 1 are listed in Table 4. Specifically, the composition of each component in gel electrolyte composition 1, gel electrolyte composition 2, gel electrolyte composition 3, gel electrolyte composition 4, gel electrolyte composition 5, gel electrolyte composition 6, gel electrolyte composition 7, gel electrolyte composition 8, gel electrolyte composition 9, gel electrolyte composition 10, gel electrolyte composition 11, gel electrolyte composition 12, and gel electrolyte composition 13 in Table 4 is shown in Table 1; the specific liquid injection methods 1, 2, and 3 in Table 4 are shown in Table 2; and the specific operation methods of in-situ curing and formation methods 1, 2, and 3 in Table 4 are shown in Table 3.

[0097] Table 1

[0098]

[0099]

[0100] Regarding the data in Table 1: Taking the gel electrolyte composition 1 in Table 1 as an example, the first component consists of fluoroether compounds, cyclic fluorocarbonates, chain fluorocarbonates, non-fluorinated ether compounds, siloxane additives, and film-forming additives. By weight percentage, the first component comprises 10% cyclic fluorocarbonates, 20% chain fluorocarbonates, 49.5% fluorocarbonates, 19.5% non-fluorinated ether compounds, 0.5% siloxane additives, and 0.5% film-forming additives. In the second component, the crosslinking agent monomer accounts for 3% of the weight of the first component; the free radical initiator accounts for 2% of the weight of the crosslinking agent monomer. The concentration of lithium salt in the gel electrolyte composition is 1.5 mol / L.

[0101] Table 2

[0102]

[0103]

[0104] Regarding the data in Table 2, taking the injection method in Table 2 as an example: the first solution includes 88% of fluoroether compounds, 80% of cyclic fluorocarbonates, 80% of chain fluorocarbonates, 85% of fluorine-free ether compounds, 100% of siloxane additives, 100% of crosslinking agent monomers, and 100% of free radical initiators in the gel electrolyte composition; and the concentration of lithium salt in the first solution is 1.3 mol / L.

[0105] The second solution comprises: the remainder of fluoroether compounds, the remainder of cyclic fluorocarbonates, the remainder of chain fluorocarbonates, the remainder of fluorine-free ether compounds, the remainder of film-forming additives, and the remainder of lithium salts; the concentration of lithium salts in the second solution is 2 mol / L.

[0106] Table 3

[0107]

[0108] Table 4

[0109]

[0110]

[0111] The lithium metal batteries prepared in the above examples and comparative examples were tested for their cycle performance at room temperature (25°C) and at high temperature (45°C), respectively. The results are shown in Table 5. The specific test methods are as follows.

[0112] Test method for cycle performance at room temperature (25℃): Place the lithium metal battery in a 25℃ constant temperature chamber and let it stand for 30 minutes to allow it to reach a constant temperature. Charge the battery at a constant current and constant voltage of 0.2C, with a cutoff voltage of 4.3V and a cutoff current of 0.04C. Then discharge at a constant current of 1C until the voltage reaches 3V; this constitutes one charge-discharge cycle. Using the initial discharge capacity as 100%, repeat the charge-discharge cycles until the discharge capacity decays to 80%. Stop the test and record the number of cycles. This parameter can be used as an indicator to evaluate the cycle stability performance of the lithium metal battery.

[0113] Test method for high-temperature (45℃) cycle performance: Place the lithium metal battery in a 45℃ constant temperature chamber and let it stand for 30 minutes to allow it to reach a constant temperature. Charge the battery at a constant current and constant voltage of 0.2C, with a cutoff voltage of 4.3V and a cutoff current of 0.04C. Then discharge at a constant current of 1C until the voltage reaches 3V; this constitutes one charge-discharge cycle. Using the initial discharge capacity as 100%, repeat the charge-discharge cycles until the discharge capacity decays to 80%. Stop the test and record the number of cycles. This parameter can be used as an indicator to evaluate the cycle stability of lithium metal batteries at higher temperatures, and also reflects the safety performance of the lithium metal battery.

[0114] Table 5

[0115]

[0116]

[0117] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0118] The lithium metal batteries prepared in the examples and comparative examples were cycled at 25°C and 45°C until their discharge capacity decayed to 80%, respectively, and the number of cycles was tested. Examples 1 to 12 were lithium metal batteries prepared using the gel electrolyte composition provided in this application and the liquid injection and curing / formation methods provided in this application. As shown in Table 5, the cycle stability of the corresponding lithium metal batteries was within a good range. In particular, the proportions of each component in the gel electrolyte composition and the liquid injection and curing / formation methods in Examples 1 to 8 and Examples 11 to 12 were all within the preferred range, resulting in better cycle stability and safety for the lithium metal batteries prepared in these examples. Example 13 used the gel electrolyte composition provided in this application, although the liquid injection method was not used, the effect was still acceptable.

[0119] In contrast, Comparative Examples 1 to 3, although using the same injection and curing / formation methods as Examples 1 to 10, exhibit significantly different cycle stability and safety compared to Examples 1 to 10 because the components of the gel electrolyte composition are not within the scope of the technical solutions provided in this application. In Comparative Example 4, the gel electrolyte composition, injection method, and curing / formation method are all outside the scope of this application, resulting in significantly different cycle stability and safety compared to the technical effects achievable with the solutions provided in this application.

[0120] In summary, the gel electrolyte composition provided in this application has a good effect on improving the cycle stability and safety of lithium metal batteries. It is evident that the synergistic effect of the components in the gel electrolyte composition formulation not only results in a uniform and stable gel electrolyte, but also effectively improves the lithium dendrite problem and interfacial side reactions in lithium metal batteries. Furthermore, by combining the gel electrolyte composition provided in this application with the liquid injection method and curing / formation method provided in this application, the cycle stability and safety of the prepared lithium metal battery can be further and effectively improved.

[0121] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gel electrolyte composition, characterized in that, The gel electrolyte composition comprises a first component, a second component, and a lithium salt; wherein, The first component includes fluoroether compounds, fluorocarbonates, non-fluorinated ether compounds, siloxane additives, and optionally film-forming additives; The second component includes a crosslinking agent monomer and a free radical initiator; By weight percentage, the first component comprises: 1-60% of the fluoroether compound, 2-50% of the fluorocarbonate, 1-60% of the fluorine-free ether compound; 0.01-10% of the siloxane additive, and 0-10% of the film-forming additive. In the second component, the crosslinking agent monomer accounts for 1 to 10% of the weight of the first component; the free radical initiator accounts for 0.01 to 5% of the weight of the crosslinking agent monomer. In the gel electrolyte composition, the concentration of the lithium salt is 0.5~3 mol / L.

2. The gel electrolyte composition according to claim 1, characterized in that, By weight percentage, the first component comprises: 20-60% of the fluoroether compound, 20-40% of the fluorocarbonate, 15-40% of the fluorine-free ether compound; 0.01-5% of the siloxane additive, and 0.01-5% of the film-forming additive. In the second component, the crosslinking agent monomer accounts for 1-5% of the weight of the first component; the free radical initiator accounts for 0.01-2% of the weight of the crosslinking agent monomer. In the gel electrolyte composition, the concentration of the lithium salt is 0.5~3 mol / L.

3. The gel electrolyte composition according to claim 1, characterized in that, The fluorocarbonate is a cyclic fluorocarbonate and / or a chain fluorocarbonate.

4. The gel electrolyte composition according to claim 3, characterized in that, The fluorocarbonate is a blend of the cyclic fluorocarbonate and the chain fluorocarbonate.

5. The gel electrolyte composition according to claim 4, characterized in that, The weight ratio of the cyclic fluorocarbonate to the chain fluorocarbonate is 1:(0.5~5).

6. The gel electrolyte composition according to claim 4, characterized in that, The weight ratio of the cyclic fluorocarbonate to the chain fluorocarbonate is 1:(1~3).

7. The gel electrolyte composition according to claim 3, characterized in that, The cyclic fluorocarbonate has the structure shown in formula (Ⅰ): Equation (I) In equation (Ⅰ), R3, R4, R5, and R6 are each independently selected from H, F, C1~C 10 Alkyl, C1~C 10 Fluoroalkyl, C2~C 10 alkenyl or C2~C 10 The fluoroalkenyl group, wherein at least one fluorine atom is present in R3, R4, R5 and R6; And / or, the chain fluorocarbonate has a compound with the structure shown in formula (II): Formula (II) In formula (II), R7 and R8 are each independently selected from H, F, C1~C 10 Alkyl, C1~C 10 Fluoroalkyl, C2~C 10 alkenyl or C2~C 10 The fluoroalkenyl group, and at least one fluorine atom in R7 and R8; And / or, the fluoroether compound is a compound having the structure shown in formula (Ⅲ): Formula (III) In equation (Ⅲ), R1 and R2 are each independently selected from C1 to C2. 10 Alkyl, C1~C 10 Fluoroalkyl, C2~C 10 alkenyl or C2~C 10 The fluoroalkenyl group, wherein R1 and R2 contain at least one fluorine atom; And / or, the fluorine-free ether compound is a compound having the structure shown in formula (Ⅳ): Equation (Ⅳ) In formula (Ⅳ), R9 and R 10 Each is independently selected from C1 to C2. 10 Alkyl or C2~C 10 Alkoxyalkyl.

8. The gel electrolyte composition according to claim 7, characterized in that, R3, R4, R5 and R6 are each independently selected from H, F, C1-C5 alkyl or C1-C5 fluoroalkyl, and each of R3, R4, R5 and R6 contains at least one fluorine atom; And / or, R7 and R8 are each independently selected from H, F, C1-C5 alkyl or C1-C5 fluoroalkyl, and R7 and R8 contain at least one fluorine atom; And / or, R1 and R2 are each independently selected from C1 to C5 alkyl groups, and the alkyl group contains at least one fluorine atom; And / or, in equation (Ⅳ), R9 and R 10 Each alkyl group is independently selected from C1 to C5.

9. The gel electrolyte composition according to claim 7, characterized in that, R3, R4, R5 and R6 are each independently selected from H, F, methyl, ethyl, monofluoromethyl, difluoromethyl or trifluoromethyl, and each of R3, R4, R5 and R6 contains at least one fluorine atom; And / or, R7 and R8 are each independently selected from H, F, methyl, ethyl, monofluoromethyl, difluoromethyl or trifluoromethyl, and R7 and R8 contain at least one fluorine atom; And / or, R1 and R2 are each independently selected from methyl, ethyl, monofluoromethyl, difluoromethyl, trifluoromethyl, 1,1,2,2-tetrafluoroethyl, 1,1,2-trifluoroethyl or trifluoromethylethyl; And / or, the R9 and the R 10 Each is independently selected from methyl, ethyl, propyl, isopropyl, or butyl.

10. The gel electrolyte composition according to claim 7, characterized in that, The cyclic fluorocarbonate has the structure shown in formula (A): Formula (A) And / or, the chain fluorocarbonate has the structure shown in formula (B): Formula (B) And / or, the fluoroether compound has the structure shown in formula (C): Formula (C) And / or, the fluorine-free ether compound has the structure shown in formula (D): Formula (D).

11. The gel electrolyte composition according to any one of claims 1 to 10, characterized in that, The lithium salt is one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxolaneborate, lithium difluorooxolaneborate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium difluorophosphate. And / or, the siloxane additive is vinyltrimethoxysilane and / or propenyltrimethoxysilane; And / or, the film-forming additive is at least one selected from lithium dioxolane borate, lithium difluorooxolane borate, lithium tetrafluoroborate, methane disulfonate, 4-trifluoromethyl vinyl carbonate, 1,3,2-dioxazothiophene-2,2-dioxide, ethylene sulfite, vinyl carbonate, succinic anhydride, propylene sulfite, propylene-1,3-sulfonyl lactone, bis(trimethylsilyl)sulfate, lithium nitrate, N-methyl,butylpyrrolidone bis(trifluoromethanesulfonyl)imide, N-methyl,propylpiperidine bis(trifluoromethanesulfonyl)imide, 1,3-dioxane, 1,4-dioxane, 1,2-bis(cyanoethoxy)ethane, adiponitrile, 1,3,5-pentanetricarbonyl, transbutenedionitrile, and 1,2,3-tris(2-cyanoethoxy)propane. And / or, the free radical initiator is at least one of azobisisobutyronitrile, cyclohexanone peroxide, azobisisoheptanenitrile, tert-butyl hydroperoxide and dimethyl azobisisobutyrate; And / or, the crosslinking agent monomer is at least one of N,N-methylenebisacrylamide, methacrylamide, N-ethylacrylamide, and cyclic acrylamide.

12. The gel electrolyte composition according to any one of claims 3 to 10, characterized in that, The gel electrolyte composition comprises: By weight percentage, the first component comprises: 49.5% of the fluoroether compound, 10% of the cyclic fluorocarbonate, 20% of the chain fluorocarbonate, and 19.5% of the non-fluorinated ether compound; 0.5% of the siloxane additive, and 0.5% of the film-forming additive; in the second component, the crosslinking agent monomer is 3% of the weight of the first component; the free radical initiator is 2% of the weight of the crosslinking agent monomer; in the gel electrolyte composition, the concentration of the lithium salt is 1.5 mol / L; or, By weight percentage, the first component comprises: 54% of the fluoroether compound, 8% of the cyclic fluorocarbonate, 22% of the chain fluorocarbonate, and 15% of the fluorine-free ether compound; 0.5% of the siloxane additive, and 0.5% of the film-forming additive; in the second component, the crosslinking agent monomer is 3% of the weight of the first component; the free radical initiator is 2% of the weight of the crosslinking agent monomer; in the gel electrolyte composition, the concentration of the lithium salt is 1.5 mol / L; or, By weight percentage, the first component comprises: 49.5% of the fluoroether compound, 10% of the cyclic fluorocarbonate, 20% of the chain fluorocarbonate, 19.5% of the fluorine-free ether compound; 0.5% of the siloxane additive, and 0.5% of the film-forming additive; in the second component, the crosslinking agent monomer is 5% of the weight of the first component; the free radical initiator is 2% of the weight of the crosslinking agent monomer; and in the gel electrolyte composition, the concentration of the lithium salt is 1.5 mol / L.

13. The method for injecting the gel electrolyte composition according to any one of claims 1 to 12, characterized in that, The gel electrolyte composition is divided into a first solution and a second solution, wherein... The first solution comprises 80-92% of the fluoroether compound, 80-90% of the fluorocarbonate, 80-90% of the non-fluorinated ether compound, 100% of the siloxane additive, 0-90% of the film-forming additive, 100% of the crosslinking agent monomer, and 100% of the free radical initiator; and the concentration of lithium salt in the first solution is 0.2-3 mol / L. The second solution comprises: the remainder of the fluoroether compound, the remainder of the fluorocarbonate, the remainder of the fluorine-free ether compound, the remainder of the film-forming additive, and the remainder of the lithium salt, wherein the concentration of the lithium salt in the second solution is 0.5 mol / L to 3.5 mol / L; The injection method includes the following steps: The first solution is injected into the electrochemical device for the first injection. The electrochemical device after the first liquid injection is then solidified and formed in situ to obtain a pretreated electrochemical device. The second solution is injected into the pretreatment electrochemical device and then sealed under vacuum to complete the injection operation.

14. The method for injecting the gel electrolyte composition according to claim 13, characterized in that, The gel electrolyte composition is divided into a first solution and a second solution, wherein... The first solution comprises 85-92% of the fluoroether compound, 80-85% of the fluorocarbonate, 80-85% of the fluorine-free ether compound, 100% of the siloxane additive, 0-90% of the film-forming additive, 100% of the crosslinking agent monomer, and 100% of the free radical initiator in the gel electrolyte composition; and the concentration of the lithium salt in the first solution is 0.2-3 mol / L. The second solution comprises: the remainder of the fluoroether compound, the remainder of the fluorocarbonate, the remainder of the fluorine-free ether compound, the remainder of the film-forming additive, and the remainder of the lithium salt, wherein the concentration of the lithium salt in the second solution is 0.5 mol / L to 3.5 mol / L.

15. The injection method according to claim 13 or 14, characterized in that, The in-situ solidification and formation steps include: after the electrochemical device has been injected with liquid for the first time, it is left to stand, and then charged with constant current to 50-70% of its full charge state to complete the in-situ solidification and formation.

16. The injection method according to claim 15, characterized in that, The settling time is 12-24 hours.

17. The injection method according to claim 15, characterized in that, The constant current charging is carried out under pressure P and temperature T conditions, wherein 0.4MPa≤P≤1.2MPa and 50≤T≤80℃.

18. The injection method according to claim 15, characterized in that, The constant current charging rate is 0.04C~0.2C.

19. A lithium metal battery, characterized in that, The electrolyte of the lithium metal battery is made from the gel electrolyte composition according to any one of claims 1 to 12; or, the electrolyte of the lithium metal battery is formed by the injection method of the gel electrolyte composition according to any one of claims 13 to 18.

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