Gel polymer electrolyte composition, gel polymer electrolyte and lithium metal battery
By using specific organic solvents and cross-linked acrylate monomers in the gel polymer electrolyte composition, a stable protective film is formed, which solves the problem of poor cycle performance of lithium metal batteries and improves the interface stability and cycle life of the battery.
Patent Information
- Application Number
- CN202510732074.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-03
- Publication Date
- 2025-09-05
AI Technical Summary
Existing lithium metal batteries have poor cycle performance, pose safety risks, and have a short cycle life.
A gel polymer electrolyte composition is used, which contains fluorophosphate, fluorine-free ether compounds and fluoroether compounds as organic solvents, combined with acrylate monomers and chain acrylate monomers with a network cross-linked structure to form a three-dimensional copolymer framework, which reduces the reaction activity of the electrolyte with the positive and negative electrodes and forms a stable protective film on the lithium metal surface.
It improves the interface stability and cycle stability of lithium metal batteries, enhances the long cycle performance and energy density of the battery, reduces the formation of lithium dendrites, and improves the lithium ion transmission efficiency and battery safety performance.
Smart Images
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Figure BDA0005432221030000161
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of batteries, and in particular to a gel polymer electrolyte composition, a gel polymer electrolyte and a lithium metal battery. Background Art
[0002] With the popularity of consumer electronic products such as laptops, mobile phones, handheld game consoles, tablets, mobile power supplies and drones, people have increasingly stringent requirements for the electrochemical devices (e.g., batteries) therein. For example, people require batteries not only to be lightweight, but also to have short charging times and long service lives. Among the many batteries, lithium metal batteries have attracted much attention in the research and development field due to their highest energy density. Currently, how to improve the cycle performance of lithium metal batteries has become a research and development focus in the field of lithium metal batteries.
[0003] The gram capacity of lithium metal as the negative electrode can reach 3860mAh / g, which is more than ten times higher than the current theoretical gram capacity of graphite of 372mAh / g. However, lithium metal has the lowest chemical potential (-3.04V) and very high reactivity. It will react with the electrolyte in the battery, and the side reactions will be more intense at high temperatures, eventually leading to cycle failure and even safety issues. Therefore, although the energy density of metal as the negative electrode material of the battery can be greatly improved, the cycle life will also be sharply shortened, and there will also be some safety hazards.
[0004] There are three important directions for improving the cycle performance of lithium metal batteries: 1. Forming a stable solid electrolyte film (SEI) on the surface of the lithium metal negative electrode. The uniform and stable SEI can reduce the reactivity of lithium metal with the electrolyte, and can also inhibit the formation of lithium dendrites, effectively improving the cycle performance of the battery. 2. Developing electrolytes with low reactivity with the lithium metal negative electrode. The electrolyte can be liquid, gel, or all-solid. After the reactivity of the electrolyte with lithium metal is reduced, the cycle coulomb efficiency and cycle life of the battery can be effectively improved. 3. Developing flame-retardant electrolytes. The electrolyte is non-flammable and can greatly improve the safety performance of lithium metal batteries. However, the existing technology still has limitations in improving the cycle performance of lithium metal batteries. Summary of the Invention
[0005] The main purpose of the present invention is to provide a gel polymer electrolyte composition, a gel polymer electrolyte and a lithium metal battery to solve the problem of poor cycle performance of lithium metal batteries in the prior art.
[0006] To achieve the above objectives, according to one aspect of the present invention, a gel polymer electrolyte composition is provided, comprising, by mass, 1-10% of a polymerizable monomer, 60-85% of an organic solvent, and the balance a lithium salt; wherein the organic solvent comprises at least a fluorophosphate, a fluorine-free ether compound, and a fluoroether compound; and the polymerizable monomer comprises at least a first acrylate monomer and a second acrylate monomer, wherein the first acrylate monomer is an acrylate monomer having a network cross-linked structure, and the second acrylate monomer is a chain acrylate monomer.
[0007] Furthermore, the organic solvent is a combination of fluorinated phosphate, fluorine-free ether compound and fluorinated ether compound, and the mass ratio of fluorinated phosphate, fluorine-free ether compound and fluorinated ether compound is (1-40):(1-40):(1-70).
[0008] Furthermore, the above-mentioned fluorophosphate is and / or wherein each R1 is independently selected from fluorine-substituted C1 to C 12 Any one of the alkylene groups, each R2 is independently selected from hydrogen, fluorine atoms, fluorine-substituted or unsubstituted C1 to C 12 Alkyl, fluorine-substituted or unsubstituted C3~C 12 Cycloalkyl, fluorine-substituted or unsubstituted C2~C 12 Alkenyl, and fluorine-substituted or unsubstituted C3~C 12 any one of heterocyclic groups; preferably, each R1 is independently selected from any one of fluorine-substituted C1~C6 alkylene groups, and each R2 is independently selected from any one of hydrogen, fluorine atom, fluorine-substituted or unsubstituted C1~C6 alkyl, fluorine-substituted or unsubstituted C3~C6 cycloalkyl, fluorine-substituted or unsubstituted C2~C6 alkenyl, and fluorine-substituted or unsubstituted C3~C6 heterocyclic groups; further preferably, each R1 is independently selected from any one of 1~2 fluorine-substituted C1~C3 alkylene groups, and each R2 is independently selected from hydrogen, fluorine atom, fluorine-substituted or unsubstituted C1~C3 alkyl; most preferably, the fluorinated phosphate is
[0009] Furthermore, the above-mentioned fluorine-free ether compound is Wherein, R3 and R4 are each independently selected from C1 to C 10 Alkyl, C2~C 10Preferably, R3 and R4 are each independently selected from any one of C1-C6 alkyl and C2-C6 alkoxyalkyl; further preferably, R3 and R4 are each independently selected from any one of C1-C3 alkyl and C2-C3 alkoxyalkyl; most preferably, R3 and R4 are each independently methyl.
[0010] Furthermore, the above-mentioned fluoroether compound is Wherein, R5 and R6 are each independently selected from C1 to C 10 Halogenated alkyl and C2~C 10 Preferably, R5 and R6 are each independently selected from any one of C1-C6 haloalkyl and C2-C6 haloalkenyl; More preferably, R5 and R6 are each independently selected from any one of C1-C3 haloalkyl; Most preferably, R5 and R6 are each independently
[0011] Furthermore, the above-mentioned polymerizable monomer is a combination of a first acrylate monomer and a second acrylate monomer, and the mass ratio of the first acrylate monomer to the second acrylate monomer is 1:(0.1-20); preferably, the first acrylate monomer is selected from ethoxylated trimethylolpropane triacrylate and / or trimethylolpropane triacrylate; and / or, the second acrylate monomer is selected from any one or more of acetoacetoxyethyl methacrylate, methyl methacrylate, ethyl acrylate and decaacrylate.
[0012] Furthermore, the gel polymer electrolyte composition further comprises 0.01 to 10% of an additive, preferably, the additive is selected from any one or more of fluorosulfone compounds, lithium-containing compounds, ester compounds, thiophene compounds, acid anhydride compounds, amide compounds, cyclic ether compounds, nitrile compounds and cyano compounds; further preferably, the fluorosulfone compound is wherein R7 is a halogen atom; and / or the lithium-containing compound is selected from any one or more of lithium dioxalatoborate, lithium difluorooxalatoborate, lithium tetrafluoroborate and lithium nitrate; and / or the ester compound is selected from any one or more of fluoroethylene carbonate, ethylene ethylene ester, methylene methanedisulfonate, 4-trifluoromethylethylene carbonate, fluoroethylene carbonate, ethylene sulfite, vinylene carbonate, propylene sulfite, propenyl-1,3-sultone and bis(trimethylsilyl)sulfate; and / or the thiophene compound is 1,3,2-dioxazolethiophene-2,2-dioxy and / or, the acid anhydride compound is succinic anhydride; and / or, the amide compound is N-methyl, butylpyrrolidine bis(trifluoromethanesulfonyl imide) salt and / or N-methyl, propylpiperidinium bis(trifluoromethanesulfonyl imide) salt; and / or, the cyclic ether compound is 1,3-dioxane and / or 1,4-dioxane; and / or, the nitrile compound is adiponitrile and / or fumaronitrile; and / or, the cyano-containing compound is selected from any one or more of 1,2-bis(cyanoethoxy)ethane, 1,3,5-pentanetricarbonitrile and 1,2,3-tris(2-cyanoethoxy)propane; most preferably, the additive is and fluoroethylene carbonate, and The mass ratio of fluoroethylene carbonate to fluoroethylene carbonate is (0.5-1):(1-2).
[0013] Furthermore, the lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium trifluoromethylsulfonate and lithium difluorophosphate.
[0014] According to another aspect of the present invention, a gel polymer electrolyte is provided. The gel polymer electrolyte is prepared by a polymerization reaction of the aforementioned gel polymer electrolyte composition. Preferably, the gel polymer electrolyte is prepared by mixing the gel polymer electrolyte composition with an initiator and subjecting the mixture to a thermal polymerization reaction. Further preferably, the mass of the initiator accounts for 0.5 to 1% of the polymerizable monomers in the gel polymer electrolyte composition, the initiator is azobisisobutyronitrile, and the thermal polymerization reaction temperature is 60 to 70° C. and the reaction time is 12 to 14 hours.
[0015] According to another aspect of the present invention, a lithium metal battery is provided, comprising a positive electrode sheet, a gel polymer electrolyte and a lithium metal negative electrode sheet, wherein the gel polymer electrolyte is the aforementioned gel polymer electrolyte.
[0016] By applying the technical solution of the present application, the acrylate monomers with a network cross-linked structure and the chain acrylate monomers in the polymerized monomers of the present application can form a three-dimensional copolymer framework. The copolymer framework will enclose the electrolyte within the framework, reducing the reactivity of the electrolyte with the positive and negative electrodes, thereby improving the interfacial stability of the positive and negative electrodes, and can also reduce the amount of electrolyte used, thereby improving the long-cycle performance and energy density of the battery. The acrylate monomers with a network cross-linked structure have strong rigidity, and the chain acrylate monomers have good flexibility. The combined use of the acrylate monomers with a network cross-linked structure and the chain acrylate monomers can simultaneously take into account the flexibility and rigidity of the copolymer framework. The flexible segments are used to transport lithium ions, and the rigid segments provide the hardness of the overall framework to prevent the passage of lithium dendrites. Fluorophosphates can improve the flame retardant properties of the electrolyte. In addition, fluorophosphates can also inhibit the corrosion and dissolution of lithium metal by reacting with the lithium metal surface to form a protective film. Moreover, fluorinated phosphates can form a more stable SEI / CEI film on the surface of the positive electrode material, inhibiting the continuous decomposition of the electrolyte, improving the compatibility of the electrolyte and electrode interface, and thus improving the cycle stability of the battery. Fluorine-free ether compounds have good stability for lithium metal negative electrodes and are difficult to react with active lithium metal. Fluorine-free ether compounds have very good solubility for lithium salts and can fully dissolve lithium salts. Fluoroether compounds have good stability for lithium metal negative electrodes and are difficult to react with active lithium metal. They can form a tight positive electrode protective film on the positive electrode. Fluoroether compounds have low viscosity and can act as diluents in the electrolyte, reducing the viscosity of the electrolyte, thereby helping to improve the transmission efficiency of lithium ions. The organic solvent of the present application contains fluorophosphate, fluorine-free ether compounds and fluoroether compounds, which helps to promote the synergistic effect between the three, improve the interface stability between the gel polymer electrolyte and the electrode, reduce the interface impedance, and thus help to improve the cycle stability performance of the lithium metal battery. The present application helps to further improve the stability of the gel polymer electrolyte finally formed by controlling the mass ratio of the polymerized monomer and the organic solvent in the gel polymer electrolyte composition within the above range, thereby helping to further improve the cycle stability performance of the lithium metal battery. DETAILED DESCRIPTION
[0017] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.
[0018] As analyzed in the background technology of this application, lithium metal batteries in the prior art have the problem of poor cycle performance. In order to solve this problem, this application provides a gel polymer electrolyte composition, a gel polymer electrolyte and a lithium metal battery.
[0019] In a typical embodiment of the present application, a gel polymer electrolyte composition is provided, which comprises, by mass fraction, 1 to 10% of a polymerizable monomer, 60 to 85% of an organic solvent, and the remainder a lithium salt; wherein the organic solvent comprises at least a fluorophosphate, a fluorine-free ether compound, and a fluoroether compound; and the polymerizable monomer comprises at least a first acrylate monomer and a second acrylate monomer, wherein the first acrylate monomer is an acrylate monomer having a network cross-linked structure, and the second acrylate monomer is a chain acrylate monomer.
[0020] The acrylate monomers with a network cross-linked structure and the chain acrylate monomers in the polymer monomers of the present application can form a three-dimensional copolymer framework. The copolymer framework will enclose the electrolyte in the framework, reduce the reactivity of the electrolyte with the positive and negative electrodes, thereby improving the interfacial stability of the positive and negative electrodes, and can also reduce the amount of electrolyte used, thereby improving the long cycle performance and energy density of the battery. The acrylate monomers with a network cross-linked structure have strong rigidity, and the chain acrylate monomers have good flexibility. The joint use of the acrylate monomers with a network cross-linked structure and the chain acrylate monomers can simultaneously take into account the flexibility and rigidity of the copolymer framework. The flexible segment is used to transport lithium ions, and the rigid segment provides the hardness of the overall framework to prevent the passage of lithium dendrites. Fluorophosphates can improve the flame retardant properties of the electrolyte. In addition, fluorophosphates can also inhibit the corrosion and dissolution of lithium metal by reacting with the lithium metal surface to form a protective film. Moreover, fluorinated phosphates can form a more stable SEI / CEI film on the surface of the positive electrode material, inhibit the continuous decomposition of the electrolyte, improve the compatibility of the electrolyte and the electrode interface, thereby improving the cycle stability of the battery. Fluorine-free ether compounds have good stability for lithium metal negative electrodes and are difficult to react with active lithium metal. Fluorine-free ether compounds have very good solubility for lithium salts and can fully dissolve lithium salts. Fluoroether compounds have good stability for lithium metal negative electrodes and are difficult to react with active lithium metal. They can form a tight positive electrode protective film on the positive electrode. Fluoroether compounds have low viscosity and can act as diluents in the electrolyte, reducing the viscosity of the electrolyte, thereby helping to improve the transmission efficiency of lithium ions. The organic solvent of the present application contains fluorophosphate, fluorine-free ether compounds and fluoroether compounds, which helps to promote the synergistic effect between the three, improve the interface stability between the gel polymer electrolyte and the electrode, reduce the interface impedance, and thus help to improve the cycle stability performance of the lithium metal battery. The present application helps to further improve the stability of the gel polymer electrolyte finally formed by controlling the mass ratio of the polymerized monomer and the organic solvent in the gel polymer electrolyte composition within the above range, thereby helping to further improve the cycle stability performance of the lithium metal battery.
[0021] In one embodiment of the present application, the above-mentioned organic solvent is a combination of fluorophosphate, fluorine-free ether compound and fluoroether compound, and the mass ratio of fluorophosphate, fluorine-free ether compound and fluoroether compound is (1-40):(1-40):(1-70), preferably (10-20):(15-25):(34.5-54.5).
[0022] Controlling the mass ratio of the fluorophosphate, the fluorine-free ether compound and the fluoroether compound within the above range helps to further enhance the synergistic effect among the three, thereby helping to further enhance the interfacial stability between the gel polymer electrolyte and the electrode, reduce the interfacial impedance, and further help to enhance the cycle stability of the lithium metal battery.
[0023] In one embodiment of the present application, the above-mentioned fluorophosphate is and / or wherein each R1 is independently selected from fluorine-substituted C1 to C 12 Any one of the alkylene groups, each R2 is independently selected from hydrogen, fluorine atoms, fluorine-substituted or unsubstituted C1 to C 12 Alkyl, fluorine-substituted or unsubstituted C3~C 12 Cycloalkyl, fluorine-substituted or unsubstituted C2~C 12 Alkenyl, and fluorine-substituted or unsubstituted C3~C 12 any one of heterocyclic groups; preferably, each R1 is independently selected from any one of fluorine-substituted C1~C6 alkylene groups, and each R2 is independently selected from any one of hydrogen, fluorine atom, fluorine-substituted or unsubstituted C1~C6 alkyl, fluorine-substituted or unsubstituted C3~C6 cycloalkyl, fluorine-substituted or unsubstituted C2~C6 alkenyl, and fluorine-substituted or unsubstituted C3~C6 heterocyclic groups; further preferably, each R1 is independently selected from any one of 1~2 fluorine-substituted C1~C3 alkylene groups, and each R2 is independently selected from hydrogen, fluorine atom, fluorine-substituted or unsubstituted C1~C3 alkyl; most preferably, the fluorinated phosphate is
[0024] Increasing the degree of fluorination of fluorophosphates can reduce the boiling point and viscosity of phosphates, thereby helping to increase the migration speed of lithium ions. Fluorine substitution at different positions can also affect the ionic conductivity and redox stability of phosphates. This application controls the type of fluorophosphates within the above range, especially fluorophosphates of When the electrolyte is prepared, it is beneficial to balance the ionic conductivity and interface stability of the electrolyte, while taking into account the ionic conductivity performance of the electrolyte.
[0025] In order to further improve the stability of the lithium metal negative electrode and the solubility of the lithium salt, in one embodiment of the present application, the above-mentioned fluorine-free ether compound is Wherein, R3 and R4 are each independently selected from C1 to C 10 Alkyl, C2~C 10 Preferably, R3 and R4 are each independently selected from any one of C1-C6 alkyl and C2-C6 alkoxyalkyl; further preferably, R3 and R4 are each independently selected from any one of C1-C3 alkyl and C2-C3 alkoxyalkyl; most preferably, R3 and R4 are each independently methyl.
[0026] In order to further improve the interface stability between the electrolyte and the electrode and the transmission efficiency of lithium ions, in one embodiment of the present application, the above-mentioned fluoroether compound is Wherein, R5 and R6 are each independently selected from C1 to C 10 Halogenated alkyl and C2~C 10 Preferably, R5 and R6 are each independently selected from any one of C1-C6 haloalkyl and C2-C6 haloalkenyl; More preferably, R5 and R6 are each independently selected from any one of C1-C3 haloalkyl; Most preferably, R5 and R6 are each independently
[0027] In one embodiment of the present application, the above-mentioned polymerized monomer is a combination of a first acrylate monomer and a second acrylate monomer, and the mass ratio of the first acrylate monomer to the second acrylate monomer is 1:(0.1-20), preferably 1:(2-8), specifically 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 and a range value between any two ratios; preferably, the first acrylate monomer is selected from ethoxylated trimethylolpropane triacrylate and / or trimethylolpropane triacrylate; and / or, the second acrylate monomer is selected from any one or more of acetoacetoxyethyl methacrylate, methyl methacrylate, ethyl acrylate and decaacrylate.
[0028] Controlling the mass ratio of the first acrylate monomer to the second acrylate monomer within the aforementioned range helps further impart both good flexibility and rigidity to the gel polymer electrolyte, thereby improving both the hardness of the gel polymer electrolyte and the efficiency of lithium ion transmission. Controlling the types of the first acrylate monomer and the second acrylate monomer within the aforementioned range helps further enhance the synergistic effect between the two monomers, thereby further improving the flexibility and rigidity of the gel polymer electrolyte.
[0029] In one embodiment of the present application, the gel polymer electrolyte composition further comprises 0.01 to 10% of an additive, preferably, the additive is selected from any one or more of fluorosulfone compounds, lithium-containing compounds, ester compounds, thiophene compounds, acid anhydride compounds, amide compounds, cyclic ether compounds, nitrile compounds and cyano compounds; further preferably, the fluorosulfone compound is wherein R7 is a halogen atom, preferably a fluorine atom and / or a chlorine atom; and / or the lithium-containing compound is selected from any one or more of lithium dioxalatoborate, lithium difluorooxalatoborate, lithium tetrafluoroborate and lithium nitrate; and / or the ester compound is selected from any one or more of fluoroethylene carbonate, ethylene ethylene ester, methylene methanedisulfonate, 4-trifluoromethylethylene carbonate, fluoroethylene carbonate, ethylene sulfite, vinylene carbonate, propylene sulfite, propenyl-1,3-sultone and bis(trimethylsilyl)sulfate; and / or the thiophene compound is 1,3,2-dioxazolethiophene-2,2-dioxide; and / or , the acid anhydride compound is succinic anhydride; and / or, the amide compound is N-methyl, butylpyrrolidine bis(trifluoromethanesulfonyl imide) salt and / or N-methyl, propylpiperidinium bis(trifluoromethanesulfonyl imide) salt; and / or, the cyclic ether compound is 1,3-dioxane and / or 1,4-dioxane; and / or, the nitrile compound is adiponitrile and / or fumaronitrile; and / or, the cyano group-containing compound is selected from any one or more of 1,2-bis(cyanoethoxy)ethane, 1,3,5-pentanetricarbonitrile and 1,2,3-tris(2-cyanoethoxy)propane; preferably, the additive is a combination of a fluorosulfone compound and an ester compound; most preferably, the additive is and fluoroethylene carbonate, and The mass ratio of fluoroethylene carbonate to fluoroethylene carbonate is (0.5-1):(1-2).
[0030] The addition of additives helps to further improve the comprehensive performance of the gel polymer electrolyte, especially the addition of fluorinated sulfone compounds and ester compounds. Compared with non-fluorinated sulfone compounds, the reduction product of fluorinated sulfone compounds is mainly LiF, rather than Li2SO3, which has better cycle performance for the battery. Fluorinated sulfone compounds have a higher oxidative decomposition potential, which helps to improve their stability under high voltage conditions. Compared with non-fluorinated sulfone compounds, fluorinated sulfone compounds have lower viscosity and better wettability, which is beneficial to the penetration of electrolytes in electrodes and separators. The introduction of fluorine atoms improves its interfacial chemical properties and electrochemical stability. Ester compounds, especially fluorinated ethylene carbonate, whose fluorinated groups can promote the formation of a denser and more stable SEI film. The lithium carbonate and fluoride produced by the decomposition of fluorinated ethylene carbonate can enhance the mechanical strength and chemical stability of the membrane, further reduce the side reactions between lithium metal and the electrolyte, and improve the cycle life of the battery. Control The mass ratio of lithium ion battery to fluoroethylene carbonate is within the above range, which helps to enhance the synergistic effect between the two, helps to form a stable and dense SEI film on the lithium metal surface, and improves the cycle stability and voltage window of the battery.
[0031] In one embodiment of the present application, the lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium trifluoromethylsulfonate and lithium difluorophosphate, and preferably the lithium salt is lithium bis(fluorosulfonyl)imide.
[0032] Controlling the type of lithium salt within the above range helps to improve the solubility of lithium salt in organic solvents, especially lithium bis(fluorosulfonyl)imide, which has a high solubility in organic solvents, and has low charge transfer resistance and good SEI film formation ability, which helps to further improve the cycle stability of lithium metal batteries.
[0033] In one embodiment of the present application, the gel polymer electrolyte composition comprises 81.5% organic solvent, 13% lithium salt, 2.5% additives, 3% polymerization monomers, wherein the additives are and fluoroethylene carbonate, The mass ratio of fluoroethylene carbonate is 0.5:2, and the organic solvent is fluorophosphate Fluorine-free ether compounds and fluoroether compounds The composition comprises a fluorophosphate, a fluorine-free ether compound and a fluoroether compound in a mass ratio of 15:20:46.5, and the polymerization monomer is a network cross-linked structure of ethoxylated trimethylolpropane triacrylate and a chain of acetoacetoxyethyl methacrylate in a mass ratio of 1:5.
[0034] In one embodiment of the present application, the gel polymer electrolyte composition comprises 79.5% organic solvent, 13% lithium salt, 2.5% additives, 5% polymerization monomers, wherein the additives are and fluoroethylene carbonate, The mass ratio of fluoroethylene carbonate is 0.5:2, and the organic solvent is fluorophosphate Fluorine-free ether compounds and fluoroether compounds The composition comprises a fluorophosphate, a fluorine-free ether compound and a fluoroether compound in a mass ratio of 15:20:46.5, and the polymerization monomer is a network cross-linked structure of ethoxylated trimethylolpropane triacrylate and a chain of acetoacetoxyethyl methacrylate in a mass ratio of 1:5.
[0035] In another typical embodiment of the present application, a gel polymer electrolyte is provided. The gel polymer electrolyte is prepared by a polymerization reaction of the aforementioned gel polymer electrolyte composition. Preferably, the gel polymer electrolyte is prepared by mixing the gel polymer electrolyte composition with an initiator and subjecting the mixture to a thermal polymerization reaction. Further preferably, the mass of the initiator accounts for 0.5 to 1% of the polymerizable monomers in the gel polymer electrolyte composition, the initiator is azobisisobutyronitrile, and the thermal polymerization reaction temperature is 60 to 70° C. and the reaction time is 12 to 14 hours.
[0036] Since the above-mentioned gel polymer electrolyte is prepared by a polymerization reaction of the gel polymer electrolyte composition of the present application, the gel polymer electrolyte has good interfacial stability with the positive and negative electrodes. The gel polymer electrolyte can form a relatively stable protective film on the surface of the positive and negative electrodes, thereby improving the cycle stability of the lithium metal battery.
[0037] In another typical embodiment of the present application, a lithium metal battery is provided, comprising a positive electrode sheet, a gel polymer electrolyte and a lithium metal negative electrode sheet, wherein the gel polymer electrolyte is the aforementioned gel polymer electrolyte.
[0038] Since the lithium metal battery contains the gel polymer electrolyte prepared by polymerization of the gel polymer electrolyte composition of the present application, the lithium metal battery has excellent long cycle performance at room temperature and high temperature.
[0039] In another typical embodiment of the present application, a method for preparing a lithium metal battery is provided, comprising: stacking a positive electrode, a separator, and a lithium metal negative electrode in order, and then superimposing them; welding the tabs and placing them in an outer packaging aluminum-plastic film, mixing a gel polymer electrolyte composition with an initiator and adding them to the aluminum-plastic film, vacuum packaging, standing at room temperature for 24 hours, high-temperature polymerization, heating at 60°C for 12 hours to perform in-situ polymerization to obtain a gel polymer electrolyte, formation (charging at a constant current of 0.02C to 3.75V, then charging at a constant current of 0.1C to 4.3V), shaping, capacity testing, and other steps to obtain a lithium metal battery.
[0040] The beneficial effects of the present application will be further illustrated below with reference to examples.
[0041] Example 1
[0042] In a dry argon atmosphere, fluorophosphate Fluorine-free ether compounds and fluoroether compounds Mix evenly to obtain an organic solvent, and then add lithium salt to the organic solvent and additives The mixture is uniformly dissolved, and then a polymerization monomer is added thereto. The polymerization monomer is a network cross-linked structure of ethoxylated trimethylolpropane triacrylate and chain ethyl acetoacetate methacrylate in a weight ratio of 1:5. After stirring, a gel polymer electrolyte composition is obtained. The gel polymer electrolyte composition comprises 83.5% by weight of the organic solvent, 13% by weight of the lithium salt, 0.5% by weight of the additive, 3% by weight of the polymerization monomer, and a weight ratio of 15:20:48.5 of the fluorinated phosphate, the fluorine-free ether compound, and the fluorinated ether compound.
[0043] Example 2
[0044] The difference from Example 1 is that the mass proportion of the organic solvent in the gel polymer electrolyte composition is 83%, the mass ratio of the fluorophosphate, the fluorine-free ether compound and the fluoroether compound is 15:20:48, and the mass proportion of the additive is 1%.
[0045] Example 3
[0046] The difference from Example 1 is that the mass ratio of the organic solvent in the gel polymer electrolyte composition is 81.5%, the mass ratio of the fluorinated phosphate, the fluorine-free ether compound and the fluorinated ether compound is 15:20:46.5, the mass ratio of the additive is 2.5%, and the additive is and fluoroethylene carbonate, The mass ratio of ethylene carbonate to fluoroethylene carbonate is 0.5:2.
[0047] Example 4
[0048] The difference from Example 3 is that the mass proportion of the organic solvent in the gel polymer electrolyte composition is 79.5%, the mass ratio of the fluorophosphate, the fluorine-free ether compound and the fluoroether compound is 15:20:44.5, and the mass proportion of the polymerized monomer is 5%.
[0049] Example 5
[0050] The difference from Example 4 is that the mass ratio of the fluorinated phosphate, the fluorine-free ether compound and the fluorinated ether compound in the gel polymer electrolyte composition is 10:15:54.5.
[0051] Example 6
[0052] The difference from Example 4 is that the mass ratio of the fluorinated phosphate, the fluorine-free ether compound and the fluorinated ether compound in the gel polymer electrolyte composition is 20:25:34.5.
[0053] Example 7
[0054] The difference from Example 4 is that the mass ratio of the fluorinated phosphate, the fluorine-free ether compound and the fluorinated ether compound in the gel polymer electrolyte composition is 1:1:70.
[0055] Example 8
[0056] The difference from Example 4 is that the mass ratio of the fluorinated phosphate, the fluorine-free ether compound and the fluorinated ether compound in the gel polymer electrolyte composition is 40:40:1.
[0057] Example 9
[0058] The difference from Example 4 is that the mass ratio of the fluorinated phosphate, the fluorine-free ether compound and the fluorinated ether compound in the gel polymer electrolyte composition is 40:40:0.5.
[0059] Example 10
[0060] The difference from Example 4 is that the fluorophosphate in the gel polymer electrolyte composition is Fluorine-free ether compounds are R3 is ethyl, R4 is methoxymethyl; fluoroether compounds are The lithium salt is lithium hexafluorophosphate; the additive is 1,3-dioxane; and the polymerized monomers are trimethylolpropane triacrylate with a network cross-linked structure and chain methyl methacrylate in a mass ratio of 1:5.
[0061] Example 11
[0062] The difference from Example 4 is that the fluorophosphate in the gel polymer electrolyte composition is Each R1 is -C2F4-, each R2 is cyclopropyl, and the ether compound containing no fluorine is R3 is n-butyl, R4 is ethoxyethyl; fluoroether compounds are The lithium salt is lithium nitrate; the additive is succinic anhydride; and the polymerized monomers are trimethylolpropane triacrylate with a network cross-linked structure and chain acrylate decaacrylate in a mass ratio of 1:5.
[0063] Example 12
[0064] The difference from Example 4 is that the mass ratio of the network-crosslinked ethoxylated trimethylolpropane triacrylate to the chain-like acetoacetoxyethyl methacrylate in the gel polymer electrolyte composition is 1:2.
[0065] Example 13
[0066] The difference from Example 4 is that the mass ratio of the network-crosslinked ethoxylated trimethylolpropane triacrylate to the chain-like acetoacetoxyethyl methacrylate in the gel polymer electrolyte composition is 1:8.
[0067] Example 14
[0068] The difference from Example 4 is that the mass ratio of the network-crosslinked ethoxylated trimethylolpropane triacrylate to the chain-like acetoacetoxyethyl methacrylate in the gel polymer electrolyte composition is 1:0.1.
[0069] Example 15
[0070] The difference from Example 4 is that the mass ratio of the network-crosslinked ethoxylated trimethylolpropane triacrylate to the chain-like acetoacetoxyethyl methacrylate in the gel polymer electrolyte composition is 1:20.
[0071] Example 16
[0072] The difference from Example 4 is that the mass ratio of the network-crosslinked ethoxylated trimethylolpropane triacrylate to the chain-like acetoacetoxyethyl methacrylate in the gel polymer electrolyte composition is 1:25.
[0073] Example 17
[0074] The difference from Example 4 is that the gel polymer electrolyte composition The mass ratio of ethylene carbonate to fluoroethylene carbonate is 1:1.
[0075] Comparative Example 1
[0076] The difference from Example 4 is that the addition of polymerization monomers is eliminated, and a gel polymer electrolyte composition is finally obtained.
[0077] Comparative Example 2
[0078] The difference from Example 4 is that, in the gel polymer electrolyte composition, the mass proportion of the organic solvent is 64.5%, the mass proportion of the lithium salt is 13%, the mass proportion of the additive is 2.5%, and the mass proportion of the polymerized monomer is 20%.
[0079] Comparative Example 3
[0080] The difference from Example 4 is that the addition of chain acetoacetoxyethyl methacrylate is eliminated, and a gel polymer electrolyte composition is finally obtained.
[0081] Comparative Example 4
[0082] The difference from Example 4 is that the addition of ethoxylated trimethylolpropane triacrylate with a network cross-linked structure is eliminated, and a gel polymer electrolyte composition is finally obtained.
[0083] Comparative Example 5
[0084] The difference from Example 4 is that the addition of fluorophosphate is omitted, and a gel polymer electrolyte composition is finally obtained.
[0085] Comparative Example 6
[0086] The difference from Example 4 is that the addition of the fluorine-free ether compound is eliminated, and a gel polymer electrolyte composition is finally obtained.
[0087] Comparative Example 7
[0088] The difference from Example 4 is that the addition of the fluoroether compound is eliminated, and a gel polymer electrolyte composition is finally obtained.
[0089] Battery preparation
[0090] By adopting the physical roller pressing method, metallic lithium is compounded onto the negative electrode current collector copper foil with a thickness of about 12μm. By adjusting the pressure of the roller, lithium is coated on one side of the copper current collector with a thickness of about 50μm. Then, the negative electrode sheet is obtained by cutting and slitting. Nickel cobalt manganese (NCM) positive electrode active material, conductive agent (SuperP conductive carbon), and binder polyvinylidene fluoride are mixed in a weight ratio of 97:1.4:1.6, and N-methylpyrrolidone (NMP) is added. The system is stirred under the action of a vacuum mixer until the system is uniform to obtain a positive electrode slurry with a solid content of 72wt%. The positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil; dried, and then after cold pressing, cutting, slitting, dried under vacuum conditions of about 85°C for about 4h to obtain a positive electrode sheet; polyethylene (PE) with a thickness of 15μm is used as an isolation membrane;
[0091] Azobisisobutyronitrile was added as an initiator to the gel polymer electrolyte composition prepared in the above examples and comparative examples, and the mass of azobisisobutyronitrile accounted for 0.5% of the mass of the polymerized monomer to obtain a mixed solution. The positive electrode sheet, the separator, and the lithium metal negative electrode sheet were stacked in order and then superimposed; after welding the tabs, they were placed in an outer packaging aluminum-plastic film, and the above mixed solution was injected into the aluminum-plastic film. After vacuum packaging, standing at room temperature for 24 hours, high-temperature polymerization was performed at 60°C for 12 hours for in-situ polymerization to obtain a gel polymer electrolyte, followed by formation (0.02C constant current charging to 3.75V, then 0.1C constant current charging to 4.3V), shaping, capacity testing, and other steps to obtain a soft-pack laminated lithium metal battery.
[0092] Performance Testing
[0093] The soft-pack laminated lithium metal battery prepared above was subjected to cycle tests at 25°C and 45°C, respectively. 25°C cycle test: The lithium metal battery was placed in a 25°C constant temperature box and allowed to stand for 30 minutes to allow the lithium metal battery to reach a constant temperature. The lithium metal battery that reached a constant temperature was charged at a constant current of 0.2C to 4.3V, then at a constant voltage of 0.5V, and then discharged at a constant current of 1C to a voltage of 3V. This was a charge and discharge cycle. The capacity of the first discharge was 100%, and the charge and discharge cycle was repeated until the discharge capacity decayed to 80%. The test was stopped and the number of cycles was recorded as an indicator for evaluating the cycle performance of the lithium metal battery. 45°C cycle test: The lithium metal battery was placed in a 45°C constant temperature box and allowed to stand for 30 minutes to allow the lithium metal battery to reach a constant temperature. The lithium metal battery that reached a constant temperature was charged at a constant current of 0.2C to 4.3V, then at a constant voltage of 0.5V, and then discharged at a constant current of 1C to a voltage of 3V. This was a charge and discharge cycle. The charge and discharge cycle is repeated with the initial discharge capacity as 100%. When the discharge capacity decays to 80%, the test is stopped and the number of cycles is recorded as an indicator for evaluating the cycle performance of the lithium metal battery.
[0094] The results of the cycle tests of the above lithium metal batteries at 25°C and 45°C are shown in Table 1.
[0095] Table 1
[0096]
[0097]
[0098] As can be seen from Table 1, the use of the gel polymer electrolyte of the present application in lithium metal batteries is beneficial for improving both the room-temperature and high-temperature cycling performance of lithium metal batteries. Comparing Example 3 with Examples 1 and 2, it can be seen that the addition of the additive slightly improves the cycling performance of the lithium metal battery, and the additive facilitates lithium deposition by forming a film at the negative electrode.
[0099] From the cycle test results of Comparative Example 1 and Example 4, it can be seen that if the polymerized monomer is not added and the gel polymer electrolyte is not formed, the cycle performance of the battery, especially the high-temperature cycle performance, will be greatly affected, because the copolymer framework will enclose the electrolyte within the framework, reducing the reaction activity of the electrolyte with the positive and negative electrodes, thereby improving the interface stability of the positive and negative electrodes, and further improving the long-cycle performance of the battery.
[0100] From the cycle test results of Comparative Example 2 and Example 4, it can be seen that if too much polymerized monomer is added and the degree of electrolyte solidification is too high, the dynamic performance of the battery will decrease, which will greatly affect the room temperature cycle performance of the battery.
[0101] From the circulation test results of Comparative Examples 3 and 4 and Example 4, it can be seen that a better circulation effect can be achieved only when the acrylate monomer with a network cross-linked structure and the chain acrylate monomer are added simultaneously.
[0102] From the cycle test results of Comparative Examples 5, 6, 7 and Example 4, it can be seen that fluorophosphates, fluorine-free ether compounds and fluoroether compounds need to be used in combination to achieve a relatively good cycle effect, which is compatible with the interface stability and appropriate ionic conductivity of the electrolyte and has certain flame retardant properties, which is beneficial to the long cycle performance of lithium metal batteries.
[0103] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:
[0104] The acrylate monomers with a network cross-linked structure and the chain acrylate monomers in the polymer monomers of the present application can form a three-dimensional copolymer framework. The copolymer framework will enclose the electrolyte in the framework, reduce the reactivity of the electrolyte with the positive and negative electrodes, thereby improving the interfacial stability of the positive and negative electrodes, and can also reduce the amount of electrolyte used, thereby improving the long cycle performance and energy density of the battery. The acrylate monomers with a network cross-linked structure have strong rigidity, and the chain acrylate monomers have good flexibility. The joint use of the acrylate monomers with a network cross-linked structure and the chain acrylate monomers can simultaneously take into account the flexibility and rigidity of the copolymer framework. The flexible segment is used to transport lithium ions, and the rigid segment provides the hardness of the overall framework to prevent the passage of lithium dendrites. Fluorophosphates can improve the flame retardant properties of the electrolyte. In addition, fluorophosphates can also inhibit the corrosion and dissolution of lithium metal by reacting with the lithium metal surface to form a protective film. Moreover, fluorinated phosphates can form a more stable SEI / CEI film on the surface of the positive electrode material, inhibit the continuous decomposition of the electrolyte, improve the compatibility of the electrolyte and the electrode interface, thereby improving the cycle stability of the battery. Fluorine-free ether compounds have good stability for lithium metal negative electrodes and are difficult to react with active lithium metal. Fluorine-free ether compounds have very good solubility for lithium salts and can fully dissolve lithium salts. Fluoroether compounds have good stability for lithium metal negative electrodes and are difficult to react with active lithium metal. They can form a tight positive electrode protective film on the positive electrode. Fluoroether compounds have low viscosity and can act as diluents in the electrolyte, reducing the viscosity of the electrolyte, thereby helping to improve the transmission efficiency of lithium ions. The organic solvent of the present application contains fluorophosphate, fluorine-free ether compounds and fluoroether compounds, which helps to promote the synergistic effect between the three, improve the interface stability between the gel polymer electrolyte and the electrode, reduce the interface impedance, and thus help to improve the cycle stability performance of the lithium metal battery. The present application helps to further improve the stability of the gel polymer electrolyte finally formed by controlling the mass ratio of the polymerized monomer and the organic solvent in the gel polymer electrolyte composition within the above range, thereby helping to further improve the cycle stability performance of the lithium metal battery.
[0105] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.
Claims
1. A gel polymer electrolyte composition, characterized in that Measured by mass fraction, the gel polymer electrolyte composition comprises: 1-10% of polymerized monomers; 60-85% organic solvent; and The balance of lithium salt; The organic solvent includes at least fluorophosphate, fluorine-free ether compound and fluoroether compound, and the polymerizable monomer includes at least a first acrylate monomer and a second acrylate monomer, the first acrylate monomer is an acrylate monomer having a network cross-linked structure, and the second acrylate monomer is a chain acrylate monomer.
2. The gel polymer electrolyte composition according to claim 1, characterized in that The organic solvent is a combination of the fluorinated phosphate, the fluorine-free ether compound and the fluorinated ether compound, and the mass ratio of the fluorinated phosphate, the fluorine-free ether compound and the fluorinated ether compound is (1-40):(1-40):(1-70).
3. The gel polymer electrolyte composition according to claim 1 or 2, characterized in that: The fluorophosphate is wherein each R1 is independently selected from fluorine-substituted C1 to C 12 Any one of the alkylene groups, each R2 is independently selected from hydrogen, fluorine atoms, fluorine-substituted or unsubstituted C1 to C 12 Alkyl, fluorine-substituted or unsubstituted C3~C 12 Cycloalkyl, fluorine-substituted or unsubstituted C2~C 12 Alkenyl, and fluorine-substituted or unsubstituted C3~C 12 Any of the heterocyclic groups; Preferably, each of the R1 is independently selected from any one of fluorine-substituted C1-C6 alkylene groups, and each of the R2 is independently selected from any one of hydrogen, a fluorine atom, a fluorine-substituted or unsubstituted C1-C6 alkyl group, a fluorine-substituted or unsubstituted C3-C6 cycloalkyl group, a fluorine-substituted or unsubstituted C2-C6 alkenyl group, and a fluorine-substituted or unsubstituted C3-C6 heterocyclic group; Further preferably, each of the R1 is independently selected from any one of 1 to 2 fluorine-substituted C1 to C3 alkylene groups, and each of the R2 is independently selected from hydrogen, a fluorine atom, or a fluorine-substituted or unsubstituted C1 to C3 alkyl group; Most preferably, the fluorophosphate is 4. The gel polymer electrolyte composition according to any one of claims 1 to 3, characterized in that The fluorine-free ether compound is Wherein, R3 and R4 are each independently selected from C1 to C 10 Alkyl, C2~C 10 Any of alkoxyalkyl; Preferably, the R3 and R4 are each independently selected from any one of C1-C6 alkyl and C2-C6 alkoxyalkyl; Further preferably, the R3 and the R4 are each independently selected from any one of a C1-C3 alkyl group and a C2-C3 alkoxyalkyl group; Most preferably, said R3 and said R4 are each independently methyl.
5. The gel polymer electrolyte composition according to any one of claims 1 to 4, characterized in that The fluoroether compound is Wherein, R5 and R6 are each independently selected from C1 to C 10 Halogenated alkyl and C2~C 10 Any of the haloalkenyl groups; Preferably, the R5 and R6 are each independently selected from any one of C1-C6 haloalkyl and C2-C6 haloalkenyl; Further preferably, the R5 and the R6 are each independently selected from any one of C1 to C3 haloalkyl groups; Most preferably, said R5 and said R6 are each independently 6. The gel polymer electrolyte composition according to any one of claims 1 to 5, characterized in that The polymerizable monomer is a combination of the first acrylate monomer and the second acrylate monomer, and the mass ratio of the first acrylate monomer to the second acrylate monomer is 1:(0.1-20); Preferably, the first acrylate monomer is selected from ethoxylated trimethylolpropane triacrylate and / or trimethylolpropane triacrylate; And / or, the second acrylate monomer is selected from any one or more of acetoacetoxyethyl methacrylate, methyl methacrylate, ethyl acrylate and decaacrylate.
7. The gel polymer electrolyte composition according to any one of claims 1 to 6, characterized in that The gel polymer electrolyte composition further comprises 0.01 to 10% of an additive, Preferably, the additive is selected from any one or more of fluorosulfone compounds, lithium-containing compounds, ester compounds, thiophene compounds, acid anhydride compounds, amide compounds, cyclic ether compounds, nitrile compounds and cyano-containing compounds; Further preferably, the fluorosulfone compound is Wherein, R7 is a halogen atom; And / or, the lithium-containing compound is selected from any one or more of lithium dioxalatoborate, lithium difluorooxalatoborate, lithium tetrafluoroborate and lithium nitrate; and / or, the ester compound is selected from any one or more of fluoroethylene carbonate, ethylene ethylene, methylene methanedisulfonate, 4-trifluoromethylethylene carbonate, fluoroethylene carbonate, ethylene sulfite, vinylene carbonate, propylene sulfite, propenyl-1,3-sultone and bis(trimethylsilyl) sulfate; and / or, the thiophene compound is 1,3,2-dioxazolethiophene-2,2-dioxide; And / or, the acid anhydride compound is succinic anhydride; And / or, the amide compound is N-methyl, butyl pyrrolidine bis trifluoromethanesulfonyl imide salt and / or N-methyl, propyl piperidine bis trifluoromethanesulfonyl imide salt; And / or, the cyclic ether compound is 1,3-dioxane and / or 1,4-dioxane; and / or, the nitrile compound is adiponitrile and / or fumaronitrile; and / or, the cyano-containing compound is selected from any one or more of 1,2-bis(cyanoethoxy)ethane, 1,3,5-pentanetricarboxylic acid nitrile and 1,2,3-tris(2-cyanoethoxy)propane; Most preferably, the additive is and the combination of the fluoroethylene carbonate, and the The mass ratio of the fluoroethylene carbonate to the fluoroethylene carbonate is (0.5-1):(1-2).
8. The gel polymer electrolyte composition according to any one of claims 1 to 7, characterized in that The lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium trifluoromethylsulfonate and lithium difluorophosphate.
9. A gel polymer electrolyte, characterized in that The gel polymer electrolyte is prepared by a polymerization reaction of the gel polymer electrolyte composition according to any one of claims 1 to 8. Preferably, the gel polymer electrolyte is prepared by mixing the gel polymer electrolyte composition with an initiator and subjecting the mixture to a thermal polymerization reaction. Further preferably, the mass of the initiator accounts for 0.5 to 1% of the polymerizable monomers in the gel polymer electrolyte composition, the initiator is azobisisobutyronitrile, and the temperature of the thermal polymerization reaction is 60 to 70° C., and the time is 12 to 14 hours.
10. A lithium metal battery comprising a positive electrode, a gel polymer electrolyte and a lithium metal negative electrode, characterized in that: The gel polymer electrolyte is the gel polymer electrolyte according to claim 9.