Gel polymer electrolyte and preparation method thereof, and lithium battery

Abstract

The present application relates to the technical field of battery, and particularly relates to a gel polymer electrolyte, a preparation method thereof and a lithium battery. The gel polymer electrolyte provided by the present application comprises a fluorine-containing polycation cross-linking network and a deep eutectic ion conduction phase; wherein the deep eutectic ion conduction phase comprises a deep eutectic solvent and a lithium salt, and the fluorine-containing polycation cross-linking network is formed by free radical polymerization of polymerizable ionic liquid monomers, fluorine-containing polymerizable monomers and a cross-linking agent under the action of an initiator, and the fluorine-containing polymerizable monomers comprise fluorine-containing acrylic ester monomers. Through the cooperation of the deep eutectic ion conduction phase and the fluorine-containing polycation cross-linking network, the lithium transference number is improved, the transmission resistance is reduced, the depletion of lithium ions at the lithium negative electrode interface is delayed, and a dense and stable interface rich in inorganic components is constructed.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a gel polymer electrolyte, its preparation method, and a lithium battery. Background Technology

[0002] Lithium metal batteries have a capacity of 3860mAh / g due to the metallic lithium. - The high theoretical specific capacity¹ and the low electrochemical potential of -3.04V (relative to the standard hydrogen electrode (SHE)) of lithium metal batteries make them an important direction for next-generation high-energy-density energy storage systems. However, lithium metal anodes are prone to problems such as uneven deposition, dendrite growth, dead lithium accumulation, and repeated rupture of the solid electrolyte interface film during cycling. These problems lead to reduced coulombic efficiency, increased interfacial impedance, and rapid capacity decay. In severe cases, they can even puncture the separator and cause short circuits and thermal runaway.

[0003] Traditional liquid electrolytes possess high room-temperature ionic conductivity and good electrode wettability. However, the solvent-dominated lithium solvation structure and highly mobile anions easily induce concentration polarization, leading to the formation of an unstable and mechanically weak SEI on the lithium metal surface. High-concentration electrolytes can increase the proportion of anions participating in lithium solvation and promote the formation of inorganic interfaces such as LiF-rich electrolytes. However, increased salt concentration usually results in increased viscosity, slower ion diffusion, and decreased rate performance. While conventional polymer electrolytes can improve safety and dimensional stability, the polar polymer segments often strongly coordinate with lithium ions, leading to insufficient room-temperature conductivity and interfacial desolvation kinetics. Gel polymer electrolytes combine the interfacial wettability of liquid electrolytes with the morphological stability of polymer electrolytes, representing an important approach for stabilizing lithium metal batteries. However, they often rely on conventional organic solvents, free ionic liquids, or high salt concentrations to provide ion conduction.

[0004] Although some gel polymer electrolytes have adopted fluorinated monomers, ionic liquids or in-situ gel networks, their ionic liquids are mostly present as free liquid phases or plasticizing conductive components, making it difficult to simultaneously achieve low-resistance lithium transport, anion migration restriction and the construction of a dense and stable inorganic component-rich stable interface.

[0005] Therefore, there is an urgent need in the field for a new gel polymer electrolyte that can simultaneously improve lithium transference number, reduce transport resistance, delay lithium ion depletion at the lithium anode interface, and construct a dense and stable inorganic component-rich interface without simply relying on high salt concentration or free ionic liquid. Summary of the Invention

[0006] To address the above problems, this invention provides a gel polymer electrolyte, its preparation method, and a lithium battery.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a gel polymer electrolyte comprising a fluorinated polycationic crosslinking network and a deep eutectic ion-conducting phase; wherein the deep eutectic ion-conducting phase comprises a deep eutectic solvent and a lithium salt, the fluorinated polycationic crosslinking network is formed by free radical polymerization of a polymerizable ionic liquid monomer, a fluorinated polymerizable monomer, and a crosslinking agent under the action of an initiator, and the fluorinated polymerizable monomer comprises a fluorinated acrylate monomer.

[0008] Preferably, the eutectic solvent includes at least one of succinic anion, glutaronitrile, adiponitrile, acetamide, N-methylacetamide, N,N-dimethylacetamide, sulfolane, ethylene carbonate, and tetraethylene glycol dimethyl ether.

[0009] Preferably, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, lithium bis(oxalateborate), and lithium tetrafluoroborate.

[0010] Preferably, the cationic monomer in the polymerizable ionic liquid includes at least one of imidazolium, pyrrolidineium, piperidinium, quaternary ammonium salt cations, and quaternary phosphonium structure monomers having unsaturated carbon-carbon double bonds; the anionic monomer in the polymerizable ionic liquid includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalateborate.

[0011] Preferably, the fluorinated acrylate monomers include hexafluorobutyl acrylate, trifluoroethyl acrylate, tetrafluoropropyl methacrylate, and perfluoroalkyl ethyl methacrylate.

[0012] Preferably, the crosslinking agent includes at least one of N,N-methylenebisacrylamide, polyethylene glycol diacrylate pentaerythritol tetraacrylate, or trimethylolpropane triacrylate; and the initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, and dicumyl peroxide.

[0013] Preferably, in the gel polymer electrolyte, the mass percentage of the deep eutectic solvent is 35%-65%, the mass percentage of the lithium salt is 15%-50%, the mass percentage of the polymerizable ionic liquid monomer is 3%-35%, the mass percentage of the fluorinated acrylate monomer is 1%-20%, the mass percentage of the crosslinking agent is 0.5%-3% of the total mass of the polymerizable ionic liquid monomer and the fluorinated acrylate monomer, and the mass percentage of the initiator is 0.1%-1% of the total mass of the polymerizable ionic liquid monomer and the fluorinated acrylate monomer.

[0014] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: a method for preparing a gel polymer electrolyte, used to prepare the gel polymer electrolyte as described in any of the preceding claims, comprising the following steps: mixing a deep eutectic solvent with a lithium salt in an inert atmosphere or dry environment and heating and stirring to form a uniform and transparent deep eutectic ion-conducting phase; adding a polymerizable ionic liquid monomer, a fluorinated acrylate monomer, a crosslinking agent, and an initiator to the deep eutectic ion-conducting phase and mixing to obtain a liquid precursor; injecting the liquid precursor into the separator, electrode channels, or battery cell of a battery; heating the liquid precursor injected into the battery to cause the polymerizable ionic liquid monomer, the fluorinated polymerizable monomer, and the crosslinking agent in the liquid precursor to undergo free radical polymerization under the action of an initiator, forming a fluorinated polycationic crosslinking network in situ inside the battery, and fixing the deep eutectic ion-conducting phase in the fluorinated polycationic crosslinking network to obtain a gel polymer electrolyte.

[0015] Preferably, the heating temperature for heating the liquid precursor is 50℃-80℃, and the heating time is 2-12h.

[0016] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: a lithium battery, the lithium battery comprising a positive electrode, a negative electrode, a separator and a gel polymer electrolyte as described in any of the above.

[0017] Compared with the prior art, the gel polymer electrolyte, its preparation method, and lithium battery provided by the present invention have the following beneficial effects: 1. The gel polymer electrolyte provided in the embodiments of the present invention includes a fluorinated polycationic crosslinking network and a deep eutectic ion-conducting phase, wherein the deep eutectic ion-conducting phase is composed of a deep eutectic solvent and a lithium salt, and the fluorinated polycationic crosslinking network is formed by free radical polymerization of polymerizable ionic liquid monomers, fluorinated monomers and crosslinking agents under the action of an initiator. The deep eutectic solvent forms a deep eutectic electrolyte phase with the lithium salt, providing a continuous ion conduction channel and a lithium salt dissolution environment. This reduces transport resistance and delays lithium-ion depletion at the lithium anode interface without relying on high salt concentrations or free ionic liquids. Polymerizable ionic liquid monomers participate in free radical copolymerization, allowing cationic structures to chemically bond into the polycationic backbone to form fixed cationic sites. These sites enrich and restrict long-range anion migration through electrostatic interactions, increasing the lithium transference number. Simultaneously, the enriched anions participate in the construction of anion-rich solvation structures, promoting preferential anion decomposition at the lithium metal interface. Fluorinated monomers provide fluorinated side chains that weaken excessive lithium-solvent coordination, lowering the ion transport barrier and promoting the formation of a solid electrolyte interface film rich in inorganic components at the lithium metal anode interface, based on the preferential anion decomposition. Therefore, the deep eutectic ion-conducting phase and the fluorinated polycationic crosslinking network work synergistically to simultaneously increase the lithium transference number, reduce transport resistance, delay lithium-ion depletion at the lithium anode interface, and construct a dense and stable interface rich in inorganic components.

[0018] 2. In this embodiment of the invention, at least one of the following is used as a deep eutectic solvent: succinate, glutaronitrile, adiponitrile, acetamide, N-methylacetamide, N,N-dimethylacetamide, sulfolane, ethylene carbonate, and tetraethylene glycol dimethyl ether. This allows the deep eutectic solvent to have polar functional groups such as nitrile, amide, sulfone, carbonate, or ether groups, which generate ion-dipole interactions with the anions and cations in the lithium salt. This allows the lithium salt to fully dissociate at a lower temperature and form a uniform and transparent deep eutectic electrolyte phase. This enables the deep eutectic ion-conducting phase to stably perform continuous lithium conduction function in the fluorinated polycationic crosslinking network. Thus, based on the increased lithium transference number of the polycationic skeleton and the fluorinated side chain regulating the interfacial film formation, the transport resistance is further reduced.

[0019] 3. In this embodiment of the invention, at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, lithium bis(oxalateborate), and lithium tetrafluoroborate is used as a lithium salt. It is dissolved and dissociated in a deep eutectic solvent to release fluorine-containing anions, which participate in the construction of anion-rich solvation structure. Under the enrichment effect of the polycationic backbone, the fluorine-containing anions preferentially participate in electrochemical decomposition at the lithium metal anode interface, promoting the formation of a solid electrolyte interface film rich in inorganic components. Thus, based on the reduction of transport resistance in the deep eutectic ion-conducting phase and the provision of interfacial fluorine source by the fluorine-containing side chain, the interface stability is further enhanced.

[0020] 4. In this embodiment of the invention, at least one of the following monomers with unsaturated carbon-carbon double bonds—imidazolium, pyrrolidineium, piperidinium, quaternary ammonium salt cations, and quaternary phosphonium—is used as the cationic monomer of the polymerizable ionic liquid, and at least one of the following lithium trifluoromethanesulfonylimide, lithium bisfluorosulfonylimide, and lithium difluorooxalateborate is used as the anion of the polymerizable ionic liquid. This allows the cationic monomer to directly participate in free radical copolymerization through unsaturated carbon-carbon double bonds, enabling the cationic structure to be chemically bonded into the polycationic framework to form fixed cationic sites. Compared to the physical embedding method of free ionic liquids, the polycationic framework in this embodiment can more stably restrict the directional migration of anions along the electric field direction. This further improves the lithium transference number by providing continuous ion conduction channels in the deep eutectic ion-conducting phase and reducing the transport energy barrier with fluorinated side chains.

[0021] 5. In this embodiment of the invention, one of hexafluorobutyl acrylate, trifluoroethyl acrylate, tetrafluoropropyl methacrylate, and perfluoroalkyl ethyl methacrylate is used as a fluorinated acrylate monomer. This allows the fluorinated side chain provided after polymerization to weaken the excessive lithium-solvent coordination through the electron-withdrawing effect and steric hindrance of fluorine atoms, thereby reducing the ion transport energy barrier. As a fluorine source for interfacial film formation, it synergistically promotes the formation of a solid electrolyte interfacial film rich in inorganic components on the surface of the lithium metal anode with the fluorinated anions enriched in the polycationic backbone. Thus, based on the reduction of transport resistance in the deep eutectic ion-conducting phase and the increase of lithium transference number in the polycationic backbone, the transport resistance is further reduced and the interfacial stability is enhanced.

[0022] 6. In this embodiment of the invention, at least one of N,N-methylenebisacrylamide, polyethylene glycol diacrylate pentaerythritol tetraacrylate, or trimethylolpropane triacrylate is used as a crosslinking agent, and at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, and dicumyl peroxide is used as an initiator. The crosslinking agent enables the polymerizable ionic liquid monomer and the fluorinated monomer to form a fluorinated polycationic crosslinking network through chemical crosslinking. The polymerization reaction is initiated by the initiator, so that the eutectic ion-conducting phase is fixed in the fluorinated polycationic crosslinking network, thereby ensuring the formation of a synergistic structure between the eutectic ion-conducting phase and the fluorinated polycationic crosslinking network.

[0023] 7. In the embodiments of the present invention, by limiting the mass percentages of eutectic solvent, lithium salt, polymerizable ionic liquid monomer, fluorinated acrylate monomer, crosslinking agent and initiator in the gel polymer electrolyte, the eutectic ion-conducting phase can provide sufficient continuous lithium conduction channels within the limited dosage range of different components. The polycationic backbone in the fluorinated polycationic crosslinking network has sufficient charge density to confine anions, and the fluorinated side chains regulate lithium-solvent coordination in an appropriate ratio and promote interfacial film formation, thereby taking into account ionic conductivity, lithium transference number and interfacial stability.

[0024] 8. This invention provides a method for preparing a gel polymer electrolyte. First, a deep eutectic solvent is mixed with a lithium salt in an inert atmosphere or dry environment and heated and stirred until a uniform and transparent deep eutectic electrolyte phase is formed. Then, a polymerizable ionic liquid monomer, a fluorinated acrylate monomer, a crosslinking agent, and an initiator are added to obtain a liquid precursor. The liquid precursor is injected into the battery separator, electrode channels, or battery cell. Free radical polymerization is initiated by heating, forming a fluorinated polycationic crosslinking network in situ inside the battery and fixing the deep eutectic ion-conducting phase within it. Thus, the stepwise process of premixing to form the deep eutectic ion-conducting phase and then preparing the liquid precursor ensures the full dissociation and uniform distribution of the lithium salt in the deep eutectic solvent. The liquid precursor has good fluidity before polymerization, fully wetting the separator and electrode channels. After polymerization, it forms a tight solid-solid interface contact, reducing interfacial impedance and improving the uniformity of lithium metal deposition.

[0025] 9. In the embodiments of the present invention, the heating temperature is 50-80℃ and the heating time is 2-12h. Under these conditions, the polymerizable ionic liquid monomer, fluorinated monomer and crosslinking agent can undergo free radical polymerization under the action of the initiator, forming a fluorinated polycationic crosslinking network in situ inside the battery, so that the deep eutectic ion-conducting phase is stably fixed in the crosslinking network.

[0026] 10. The present invention also provides a lithium battery that has the same beneficial effects as the gel polymer electrolyte described above, which will not be described in detail here. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a scanning electron microscope image of a gel polymer electrolyte provided in the first embodiment of the present invention at 5000x magnification.

[0029] Figure 2 This is a scanning electron microscope image of a gel polymer electrolyte provided in the first embodiment of the present invention at 200x magnification.

[0030] Figure 3 This is a schematic diagram illustrating the working principle of a gel polymer electrolyte provided in the first embodiment of the present invention. Figure 4 This is a flowchart of the preparation method of a gel polymer electrolyte provided in the second embodiment of the present invention.

[0031] Figure 5 This is a schematic diagram of the composition and in-situ polymerization preparation process of a gel polymer electrolyte provided in the second embodiment of the present invention.

[0032] Figure 6 The results provided in the second embodiment of the present invention are obtained by testing the ionic conductivity of electrolytes prepared in the experimental example and the comparative example under different temperature conditions and performing linear fitting based on the Arrhenius relation.

[0033] Figure 7 The results are linear scan voltammetry test results of the electrolytes prepared in the experimental examples and comparative examples provided in the second embodiment of the present invention.

[0034] Figure 8 The results are from the constant current lithium plating / stripping cycle tests of the lithium symmetric batteries assembled with electrolytes prepared in the experimental examples and comparative examples provided in the second embodiment of the present invention under the conditions of a current density of 0.5 mA / cm2 and a areal capacity of 0.5 mA / cm2.

[0035] Figure 9 The second embodiment of the present invention provides the cycle performance test results of a lithium / nickel cobalt manganese oxide battery assembled using the gel polymer electrolyte prepared in the experimental example in the voltage range of 2.8 to 4.5 V. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0037] Please see Figures 1-3 This embodiment provides a gel polymer electrolyte, comprising a fluorinated polycationic crosslinking network and a deep eutectic ion-conducting phase; wherein, the deep eutectic ion-conducting phase comprises a deep eutectic solvent and a lithium salt, and the fluorinated polycationic crosslinking network is formed by free radical polymerization of a polymerizable ionic liquid monomer, a fluorinated polymerizable monomer, and a crosslinking agent under the action of an initiator, wherein the fluorinated polymerizable monomer comprises a fluorinated acrylate monomer.

[0038] Specifically, a homogeneous and transparent eutectic electrolyte phase is formed by mixing a deep eutectic solvent with a lithium salt and heating and stirring. The deep eutectic solvent possesses strong polar functional groups, which generate effective ion-dipole interactions with the cations and anions in the lithium salt, promoting the complete dissociation of the lithium salt at a lower temperature. This deep eutectic electrolyte phase is the deep eutectic ion-conducting phase, providing a continuous ion conduction channel and a lithium salt dissolution environment for lithium ions. It undertakes the main ion conduction function without relying on high salt concentrations or free ionic liquids, reducing transport resistance and delaying lithium ion depletion at the lithium anode interface. The deep eutectic ion-conducting phase is immobilized within a fluorinated polycationic crosslinked network.

[0039] Specifically, in combination Figure 3 , Figure 3 This is a schematic diagram illustrating the working principle of the gel polymer electrolyte provided in this embodiment. Figure 3 In this gel polymer electrolyte, polymerizable ionic liquid monomers and fluorinated polymerizable monomers participate in free radical polymerization under the action of an initiator, forming a fluorinated polycationic crosslinking network together with a crosslinking agent. This fluorinated polycationic crosslinking network, together with the deep eutectic electrolyte, constructs an efficient and continuous ion conduction channel, enabling rapid lithium-ion migration. Specifically, after polymerization, the polymerizable ionic liquid monomers allow cationic structures to enter the polymer backbone, forming fixed cationic sites, thus constituting a polycationic backbone. The polycationic backbone enriches and restricts the long-range migration of anions by fixing cationic sites, making it difficult for anions to move directionally under an electric field, thereby increasing the lithium transference number and reducing concentration polarization. Simultaneously, the polymerizable ionic liquid monomers themselves contain free anions. After polymerization, these anions, along with anions dissociated from the lithium salt, are enriched around the polycationic backbone, constructing anion-rich solvation structures. This promotes the preferential participation of anions in interfacial reactions at the lithium metal interface, enabling the gel polymer electrolyte in this embodiment to form a stable solid electrolyte interfacial film within the battery's internal energy. Furthermore, by introducing fluorinated side chains through fluorinated polymerizable monomers, the fluorinated side chains have electron-withdrawing and steric hindrance effects, which weaken the excessive lithium-solvent coordination, lower the ion transport energy barrier, and make the transport of lithium ions in the fluorinated polycationic crosslinked network smoother, thereby further reducing the transport resistance and achieving dense lithium deposition.

[0040] More specifically, the crosslinking agent copolymerizes with the polymerizable ionic liquid monomer and the fluorinated monomer during polymerization, forming chemical crosslinking points between polymer chains. This constructs a fluorinated polycationic crosslinking network, fixing the eutectic ion-conducting phase within it. This allows the gel polymer electrolyte to possess both the interfacial wettability of a liquid electrolyte and the morphological stability of a polymer electrolyte. The initiator initiates a free radical polymerization reaction between the polymerizable ionic liquid monomer, the fluorinated monomer, and the crosslinking agent under heating conditions.

[0041] Understandably, in this embodiment, the gel polymer electrolyte uses a deep eutectic solvent and lithium salt to form a deep eutectic ion-conducting phase, which is then fixed in a fluorinated polycationic crosslinking network by the action of crosslinking agents and initiators, thereby providing a continuous ion conduction channel and a lithium salt dissolution environment. A polycationic backbone is formed by polymerization of polymerizable ionic liquid monomers, thereby enriching and restricting the long-range migration of anions and increasing the lithium transference number. Fluorinated side chains are provided by fluorinated polymerizable monomers to weaken the excessive lithium-solvent coordination and promote the formation of an inorganic component-rich interface. Thus, through the synergistic cooperation between the deep eutectic ion-conducting phase and the fluorinated polycationic crosslinking network, the effects of increasing the lithium transference number, reducing transport resistance, and delaying lithium ion depletion at the lithium anode interface can be achieved simultaneously without simply relying on high salt concentrations or free ionic liquids, while also constructing a dense and stable inorganic component-rich interface.

[0042] Furthermore, the eutectic solvent includes at least one of succinic anion, glutaronitrile, adiponitrile, acetamide, N-methylacetamide, N,N-dimethylacetamide, sulfolane, ethylene carbonate, and tetraethylene glycol dimethyl ether.

[0043] Specifically, succinic anion, glutaronitrile, and adiponitrile belong to the nitrile class of compounds and contain a cyano group in their molecules; acetamide, N-methylacetamide, and N,N-dimethylacetamide belong to the amide class of compounds and contain an amide group in their molecules; sulfolane belongs to the sulfone class of compounds and contains a sulfone group in its molecules; ethylene carbonate belongs to the carbonate class of compounds and contains a carbonate group in its molecules; and tetraethylene glycol dimethyl ether belongs to the ether class of compounds and contains an ether group in its molecules. These substances belong to the nitrile, amide, sulfone, carbonate, and ether classes, respectively, and can all form a stable eutectic phase with lithium salts, providing a continuous ion conduction channel for lithium ions. Furthermore, the cyano, amide, sulfone, carbonate, or ether groups contained in these substances are all strongly polar functional groups, generating effective ion-dipole interactions with the cations and anions in lithium salts. This promotes the complete dissociation of lithium salts at lower temperatures, forming a homogeneous and transparent eutectic electrolyte phase, providing a stable and continuous conduction channel and a suitable dissolution environment for lithium salts without the need for volatile organic co-solvents.

[0044] Preferably, among the above-mentioned deep eutectic solvents, succinate SN is used as a representative of nitrile compounds. It has a moderate molecular chain length and high polarity. Its cyano group has a strong ion-dipole interaction with the anions and cations in the lithium salt. It can form a low-melting-point, uniform and transparent deep eutectic electrolyte phase with the lithium salt at a lower temperature. At the same time, it suppresses the crystallization of the deep eutectic solvent itself and provides a stable and continuous conduction channel for lithium ions.

[0045] Understandably, by selecting at least one of succinic anion, glutaronitrile, adiponitrile, acetamide, N-methylacetamide, N,N-dimethylacetamide, sulfolane, ethylene carbonate, and tetraethylene glycol dimethyl ether as a deep eutectic solvent, and utilizing the fact that these substances belong to nitrile, amide, sulfone, carbonate, and ether compounds respectively, the strongly polar functional groups such as cyano, amide, sulfone, carbonate, or ether groups contained in them generate effective ion-dipole interactions with the anions and cations in the lithium salt. This promotes the complete dissociation of the lithium salt and the formation of a uniform and transparent deep eutectic electrolyte phase, allowing the deep eutectic ion-conducting phase to stably perform continuous lithium conduction function in the fluorinated polycationic crosslinked network, thereby further reducing the transport resistance.

[0046] Furthermore, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, lithium bis(oxalateborate), and lithium tetrafluoroborate.

[0047] Specifically, lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide belong to the imine lithium salt class, lithium difluorooxalateborate and lithium bis(oxalateborate)borate belong to the borate lithium salt class, and lithium tetrafluoroborate belongs to the fluoroborate lithium salt class. These lithium salts, belonging to the imine, borate, and fluoroborate classes respectively, can all dissolve in deep eutectic solvents and dissociate into fluorine-containing anions, participating in the construction of anion-rich solvation structures. Under the enrichment effect of the polycationic framework, the fluorine-containing anions dissociated from these lithium salts preferentially participate in interfacial reactions at the lithium metal anode interface, promoting the formation of a solid electrolyte interfacial film rich in inorganic components.

[0048] Preferably, among the above lithium salts, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), as a representative of imine lithium salts, exhibits high solubility and dissociation in deep eutectic solvents, and its fluorine-containing anion TFSI... - It participates in the construction of anion-rich solvation structures, which is beneficial for the rapid transport of lithium ions.

[0049] Understandably, this embodiment selects at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, lithium bis(oxalateborate), and lithium tetrafluoroborate as lithium salts. These lithium salts belong to the imine, borate, and fluoroborate classes, respectively, and can dissolve and dissociate into fluorine-containing anions in deep eutectic solvents. These anions participate in the construction of anion-rich solvation structures. Under the enrichment effect of the polycationic framework, the fluorine-containing anions preferentially participate in interfacial reactions at the lithium metal anode interface, promoting the formation of a solid electrolyte interfacial film rich in inorganic components, thereby enhancing interfacial stability.

[0050] Furthermore, the cationic monomers in the polymerizable ionic liquid include at least one of imidazolium, pyrrolidineium, piperidinium, quaternary ammonium salt cations, and quaternary phosphonium structure monomers having unsaturated carbon-carbon double bonds; the anionic monomers in the polymerizable ionic liquid include at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalateborate.

[0051] Specifically, imidazolium, pyrrolidineium, and piperidinium are nitrogen-containing heterocyclic cations, quaternary ammonium salt cations are quaternary ammonium cations, and quaternary phosphonium monomers are quaternary phosphonium cations. All of these cationic monomers possess unsaturated carbon-carbon double bonds and can participate in free radical polymerization under the action of an initiator, allowing the cationic structure to chemically bond into the polymer backbone and form fixed cationic sites. Lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalateborate, as anions of polymerizable ionic liquids, exist as free anions in the fluorinated polycationic crosslinking network after polymerization.

[0052] More specifically, the aforementioned cationic monomers participate in free radical copolymerization through unsaturated carbon-carbon double bonds, allowing the cationic structure to be chemically embedded into the polymer backbone to form fixed cationic sites. Compared to the method of physically embedding ionic liquids as free liquid phases, the chemically bonded fixed cationic sites do not migrate with the direction of the electric field or gradually disappear with cycling. They can more stably and persistently restrict the long-range migration of anions through charge screening effects, thereby effectively suppressing concentration polarization and increasing the lithium transference number. At the same time, the anions confined around the polycationic backbone participate in the construction of anion-rich solvation structures, which is beneficial for the preferential participation of anions in film-forming reactions at the lithium metal interface.

[0053] Optionally, in the above polymerizable ionic liquid, 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt VMIMTFSI or 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide salt VEIMTFSI is a preferred combination of cationic monomer and anionic compound. The cationic monomer contains vinyl and imidazolium rings, and after polymerization, the imidazolium rings act as fixed cationic sites within the polycationic backbone. The anionic compound TFSI... - As free anions, they are enriched around the polycationic backbone, exhibiting both good polymerization activity and ion conduction properties.

[0054] Understandably, by selecting at least one of the monomers with unsaturated carbon-carbon double bonds, such as imidazolium, pyrrolidium, piperidinium, quaternary ammonium salt cations, or quaternary phosphonium, as the cationic monomer of the polymerizable ionic liquid, and selecting at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, or lithium difluorooxalateborate as the anion of the polymerizable ionic liquid, the cationic monomer participates in polymerization through the unsaturated carbon-carbon double bonds and enters the polymer backbone to form fixed cationic sites. This makes the enrichment and confinement of anions by the polycationic backbone more stable and durable, thereby increasing the lithium transference number.

[0055] Furthermore, fluorinated acrylate monomers include hexafluorobutyl acrylate, trifluoroethyl acrylate, tetrafluoropropyl methacrylate, and perfluoroalkyl ethyl methacrylate.

[0056] Specifically, hexafluorobutyl acrylate, trifluoroethyl acrylate, tetrafluoropropyl methacrylate, and perfluoroalkyl ethyl methacrylate are all fluorinated acrylate monomers, containing acrylate groups and fluorinated alkyl segments in their molecules. After participating in free radical polymerization under the action of an initiator, the fluorinated alkyl segments of these fluorinated acrylate monomers form fluorinated side chains in the fluorinated polycationic crosslinking network.

[0057] More specifically, in the fluorinated side chains introduced after the polymerization of the aforementioned fluorinated acrylate monomers, the fluorine atoms possess strong electronegativity. Through the electron-withdrawing effect, they weaken the excessively strong coordination between lithium ions and polar functional groups in the eutectic solvent molecules, lowering the energy barrier for lithium ion transport in the fluorinated polycationic crosslinking network, thereby reducing transport resistance. Simultaneously, the fluorinated side chains, acting as a fluorine source for interfacial film formation, synergistically work with the fluorinated anions enriched in the polycationic backbone, facilitating the formation of a solid electrolyte interfacial film rich in inorganic components on the lithium metal surface, thus improving interfacial stability.

[0058] Preferably, among the above-mentioned fluorinated acrylate monomers, hexafluorobutyl acrylate (HFBA) has a suitable fluorine content and chain length. Its fluorinated side chain can effectively weaken the excessive lithium-solvent coordination and can also synergistically provide a fluorine source for interfacial film formation with the fluorinated anions enriched in the polycationic backbone, thus taking into account the dual functions of reducing transport resistance and promoting interfacial film formation.

[0059] Understandably, by selecting hexafluorobutyl acrylate, trifluoroethyl acrylate, tetrafluoropropyl methacrylate, and perfluoroalkyl ethyl methacrylate as fluorinated acrylate monomers, the fluorinated side chains introduced after polymerization of these monomers weaken the excessive lithium-solvent coordination, reduce the ion transport energy barrier, and synergistically promote the formation of a solid electrolyte interface film rich in inorganic components at the lithium metal interface with the fluorinated anions enriched in the polycationic backbone, thereby further reducing transport resistance and enhancing interface stability.

[0060] Furthermore, the crosslinking agent includes at least one of N,N-methylenebisacrylamide, polyethylene glycol diacrylate pentaerythritol tetraacrylate, or trimethylolpropane triacrylate; the initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, and dicumyl peroxide.

[0061] Specifically, N,N-methylenebisacrylamide contains two acrylamide groups, polyethylene glycol diacrylate contains two acrylate groups, pentaerythritol tetraacrylate contains four acrylate groups, and trimethylolpropane triacrylate contains three acrylate groups. All of the above crosslinking agents contain two or more polymerizable unsaturated bonds. During free radical polymerization, they can copolymerize with polymerizable ionic liquid monomers and fluorinated monomers, forming crosslinking points between polymer chains. This constructs a fluorinated polycationic crosslinking network, fixing the eutectic ion-conducting phase within the fluorinated polycationic crosslinking network. This allows the gel polymer electrolyte to possess both the interfacial wettability of liquid electrolytes and the morphological stability of polymer electrolytes.

[0062] Specifically, azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate belong to the azo initiator class, while benzoyl peroxide and diisopropylbenzene peroxide belong to the peroxide initiator class. These initiators decompose under thermal initiation to generate free radicals, which initiate free radical polymerization of polymerizable ionic liquid monomers, fluorinated monomers, and crosslinking agents, forming a fluorinated polycationic crosslinked network.

[0063] Understandably, by selecting at least one of N,N-methylenebisacrylamide, polyethylene glycol diacrylate, pentaerythritol tetraacrylate, or trimethylolpropane triacrylate as a crosslinking agent, and at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, or dicumyl peroxide as an initiator, the crosslinking agent forms crosslinking points during polymerization to construct a fluorinated polycationic crosslinking network. The eutectic ion-conducting phase is fixed in the fluorinated polycationic crosslinking network. The initiator decomposes under thermal initiation, photoinitiation, or thermal-photosynergistic initiation to generate free radicals, which initiate free radical polymerization of polymerizable ionic liquid monomers, fluorinated monomers, and crosslinking agents, thus ensuring the formation of a synergistic structure between the fluorinated polycationic crosslinking network and the eutectic ion-conducting phase.

[0064] Optionally, the initiator can also be photoinitiated, thermo-photosynthetic initiated, or other free radical polymerization initiation methods. In photoinitiation, the initiator decomposes to generate free radicals under light irradiation; in thermo-photosynthetic initiation, the initiator decomposes to generate free radicals under the combined action of heating and light irradiation. The appropriate initiation method can be selected according to the actual preparation conditions.

[0065] Furthermore, in the gel polymer electrolyte, the mass percentage of the eutectic solvent is 35%-75%, the mass percentage of the lithium salt is 15%-50%, the mass percentage of the polymerizable ionic liquid monomer is 3%-25%, the mass percentage of the fluorinated acrylate monomer is 1%-20%, the mass percentage of the crosslinking agent is 0.5%-3% of the total mass of the polymerizable ionic liquid monomer and the fluorinated acrylate monomer, and the mass percentage of the initiator is 0.1%-1% of the total mass of the polymerizable ionic liquid monomer and the fluorinated acrylate monomer.

[0066] Specifically, if the mass percentage of the eutectic solvent is too low, the volume of the eutectic ion-conducting phase is insufficient, resulting in discontinuous ion conduction channels and decreased ionic conductivity. If it is too high, the content of polymerizable monomers is relatively reduced, and the fluorinated polycationic crosslinking network backbone is insufficient, failing to effectively fix the eutectic ion-conducting phase and confine anions. If the mass percentage of lithium salt is too low, the carrier concentration is insufficient, resulting in low ionic conductivity. If it is too high, the lithium salt may exceed the solubility of the eutectic solvent and precipitate out. At the same time, the anions dissociated from the excess lithium salt exceed the confinement capacity of the polycationic backbone, leading to a decrease in lithium transference number. If the mass percentage of polymerizable ionic liquid monomers is too low, the charge density of the polycationic backbone is insufficient, weakening the enrichment and confinement effect on anions, and the increase in lithium transference number is not significant. If it is too high, the polycationic backbone is too dense, the porosity of the fluorinated polycationic crosslinking network decreases, the ion conduction channels of the eutectic ion-conducting phase are blocked, and the ionic conductivity decreases. If the mass percentage of fluorinated acrylate monomers is too low, the content of fluorinated side chains will be insufficient, resulting in an insignificant weakening effect on lithium-solvent coordination, limited reduction in transport resistance, and insufficient fluorine source for interfacial film formation. If the mass percentage is too high, there will be an excessive amount of fluorinated side chains, leading to over-dilution of the eutectic ion-conducting phase and obstruction of ion transport channels. If the amount of crosslinking agent is too low, the crosslinking density of the fluorinated polycationic crosslinking network will be insufficient, resulting in poor morphological stability and inadequate fixation of the eutectic ion-conducting phase. If the amount is too high, the crosslinking density will be too high, the fluorinated polycationic crosslinking network will be too rigid, restricting polymer chain movement and hindering lithium-ion transport within the network. If the amount of initiator is too low, the polymerization reaction will be incompletely initiated, resulting in low monomer conversion and excessive residual monomer. If the amount is too high, excessive initiator residue may adversely affect battery performance. Therefore, in the gel polymer electrolyte, the mass percentage of the eutectic solvent is 35%-65%, the mass percentage of the lithium salt is 15%-50%, the mass percentage of the polymerizable ionic liquid monomer is 3%-35%, the mass percentage of the fluorinated acrylate monomer is 1%-20%, the amount of the crosslinking agent is 0.5%-3% of the total mass of the polymerizable ionic liquid monomer and the fluorinated acrylate monomer, and the amount of the initiator is 0.1%-1% of the total mass of the polymerizable ionic liquid monomer and the fluorinated acrylate monomer.

[0067] More specifically, within the aforementioned dosage range, the deep eutectic ion-conducting phase occupies the bulk volume proportion, providing ample continuous lithium-ion conduction channels and a lithium salt dissolution environment; polymerizable ionic liquid monomers are polymerized in an appropriate proportion to form a polycationic backbone with sufficient charge density, effectively enriching and confining anions and increasing lithium transference number; fluorinated acrylate monomers are introduced with fluorinated side chains in an appropriate proportion to weaken excessive lithium-solvent coordination, thereby lowering the transport energy barrier, and synergistically promoting interfacial film formation with the anions enriched in the polycationic backbone; the amount of crosslinking agent ensures that the fluorinated polycationic crosslinking network has a moderate crosslinking density, balancing morphological stability and ion conductivity; the amount of initiator ensures that the polymerization reaction proceeds fully. The synergistic effect of each component within the aforementioned dosage range enables the gel polymer electrolyte to balance ionic conductivity, lithium transference number, and interfacial stability.

[0068] Optionally, the mass percentage of the deep eutectic solvent may be at least one range from 35%-45%, 45%-55%, and 55%-65%, or a combination of continuous ranges, or any value from 35%, 40%, 45%, 50%, 55%, 60%, and 65%; the mass percentage of the lithium salt may be at least one range from 15%-25%, 25%-35%, 35%-45%, and 45%-50%, or a combination of continuous ranges, or 15%, 20%, 25%, and 30%. The mass percentage of the polymerizable ionic liquid monomer may also be any value from 35%, 40%, 45%, and 50%; the mass percentage of the monomer may also be at least one range from 3%-8%, 8%-15%, 15%-20%, 20%-25%, 25%-30%, and 30-35%, or a combination of continuous ranges, or any value from 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 30%, and 35%; the mass percentage of the fluorinated acrylate monomer may also be 1%-5%. The crosslinking agent can be at least one of the following ranges: 5%-10%, 10%-15%, 15%-20%, or a combination of continuous ranges; it can also be any value among 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, and 20%. The amount of crosslinking agent can also be at least one of the following ranges: 0.5%-1%, 1%-2%, 2%-3% of the total mass of the polymerizable ionic liquid monomer and the fluorinated acrylate monomer, or a combination of continuous ranges; it can also be 0.5%, 1%, 1.5%, 2%, and 2.5%. The amount of initiator can be any value among 0.1%-0.3%, 0.3%-0.5%, 0.5%-0.8%, and 0.8%-1% of the total mass of the polymerizable ionic liquid monomer and the fluorinated acrylate monomer, or a combination of continuous ranges. It can also be any value among 0.1%, 0.2%, 0.3%, 0.5%, 0.8%, and 1%, as long as the gel polymer electrolyte can take into account ionic conductivity, lithium transference number, and interfacial stability. This embodiment does not impose any restrictions on this.

[0069] Please see Figure 4 and Figure 5 The second embodiment of the present invention provides a method for preparing a gel polymer electrolyte, used to prepare the gel polymer electrolyte described in the first embodiment, comprising the following steps: S10: In an inert atmosphere or dry environment, a deep eutectic solvent is mixed with a lithium salt and heated and stirred to form a uniform and transparent deep eutectic ion-conducting phase; S20: Add polymerizable ionic liquid monomers, fluorinated acrylate monomers, crosslinking agents and initiators to the deep eutectic ion-conducting phase and mix them to obtain a liquid precursor; S30: Inject the liquid precursor into the battery separator, electrode channels, or battery cell; S40: The liquid precursor injected into the battery is heated to allow the polymerizable ionic liquid monomer, fluorinated polymerizable monomer and crosslinking agent in the liquid precursor to undergo free radical polymerization under the action of an initiator, forming a fluorinated polycationic crosslinking network in situ inside the battery, and fixing the deep eutectic ion-conducting phase in the fluorinated polycationic crosslinking network to obtain a gel polymer electrolyte.

[0070] Specifically, in step S10, the eutectic solvent and lithium salt are placed in a clean glass bottle in an inert atmosphere glove box with both moisture and oxygen content below 0.1 ppm. The eutectic solvent has strongly polar functional groups, which, under heating conditions, generate effective ion-dipole interactions with the cations and anions in the lithium salt. This causes the lattice energy of the lithium salt to decrease and gradually dissociate. Lithium ions in the lithium salt coordinate with the polar functional groups in the eutectic solvent molecules, while anions disperse in the eutectic solvent, ultimately forming a uniform and transparent eutectic electrolyte phase. This eutectic electrolyte phase is the eutectic ion-conducting phase. The heating temperature reduces the viscosity of the eutectic solvent and accelerates molecular motion, which is beneficial for the complete dissociation and uniform dispersion of the lithium salt. Step S10 is carried out in an inert atmosphere or a dry environment to prevent side reactions between moisture or oxygen and the lithium salt, ensuring the purity and stability of the eutectic ion-conducting phase.

[0071] Specifically, in step S20, after the polymerizable ionic liquid monomer dissolves in the eutectic ion-conducting phase, its cationic and anionic portions are uniformly dispersed in the eutectic ion-conducting phase; after the fluorinated acrylate monomer dissolves in the eutectic ion-conducting phase, its fluorinated segments are uniformly dispersed; after the crosslinking agent dissolves, its multifunctional polymerizable groups are uniformly distributed in the system; and after the initiator dissolves, it is uniformly dispersed, providing a source of free radicals for subsequent polymerization reactions. Step S20 adopts a stepwise process of completing step S10 first and then adding the polymerizable component, ensuring that the lithium salt is fully dissociated in the eutectic solvent and forms a uniform eutectic ion-conducting phase before being mixed with the polymerizable component. This avoids the problem of insufficient lithium salt dissociation or uneven local concentration caused by mutual interference between the lithium salt and the polymerizable component when all components are mixed at once.

[0072] Specifically, in step S30, the liquid precursor exhibits good fluidity before polymerization. Relying on its low viscosity and good wettability, it permeates and spreads along the submicron pores of the membrane and the porous electrode channels of the positive and negative electrodes, gradually filling the pores inside the membrane and the voids between the electrode active material particles, thus expelling residual gas from the pores. The thorough wetting of the liquid precursor allows the eutectic ion-conducting phase and polymerizable components to form sufficient microscale contact with the surface of the electrode active material, laying the foundation for a tight solid-solid interface contact after subsequent polymerization.

[0073] Specifically, in step S40, under heating conditions, the initiator molecules decompose to generate primary free radicals. These primary free radicals attack the unsaturated carbon-carbon double bonds of the polymerizable ionic liquid monomers, causing them to open and form monomer free radicals. These monomer free radicals then undergo continuous addition reactions with the unsaturated carbon-carbon double bonds of other polymerizable ionic liquid monomers, fluorinated acrylate monomers, or crosslinking agent molecules, resulting in continuous polymer chain growth. The crosslinking agent molecules contain two or more polymerizable unsaturated bonds and can simultaneously participate in the growth reactions of multiple polymer chains, forming chemical crosslinking points between different polymer chains. As the polymerization reaction proceeds, the polymer chains connect to each other through these crosslinking points, gradually constructing a three-dimensional framework structure of a fluorinated polycationic crosslinking network. The cationic structures of the polymerizable ionic liquid monomers enter the polymer framework through chemical bonding, becoming cationic sites fixed on the network, thus forming the polycationic framework. The fluorinated segments of the fluorinated acrylate monomers are suspended in the fluorinated polycationic crosslinking network, forming fluorinated side chains. During the gradual formation of the fluorinated polycationic crosslinking network, the eutectic ion-conducting phase is encapsulated and fixed within the pores of the fluorinated polycationic crosslinking network. The polymerization reaction occurs simultaneously at the electrode interface, and the resulting fluorinated polycationic crosslinked network forms a tight solid-solid interface with the surface of the electrode active material.

[0074] Understandably, through steps S10-S40, a uniform eutectic ion-conducting phase is first formed, followed by the preparation of a liquid precursor containing polymerizable components. After injection into the battery, in-situ polymerization forms a fluorinated polycationic crosslinking network, fixing the eutectic ion-conducting phase within it. The liquid precursor fully wets the separator and electrode channels before polymerization, and after polymerization, it forms a tight solid-solid interface, reducing interfacial impedance and improving the uniformity of lithium metal deposition. Simultaneously, the polymerizable ionic liquid monomers, after polymerization, introduce cationic structures into the polymer backbone, forming fixed cationic sites and constituting a polycationic backbone. This enriches and restricts the long-range migration of anions, increasing the lithium transference number. Fluorinated acrylate monomers, after polymerization, introduce fluorinated side chains, weakening excessively strong lithium-solvent coordination, reducing ion transport resistance, and promoting the formation of a solid electrolyte interfacial film rich in inorganic components at the lithium metal interface. Thus, through the above steps S10-S40, the synergistic construction of the deep eutectic ion-conducting phase and the fluorinated polycation crosslinking network is achieved. Without simply relying on high salt concentration or free ionic liquid, it simultaneously increases the lithium transference number, reduces transport resistance, delays lithium ion depletion at the lithium anode interface, and constructs a dense and stable inorganic component-rich interface, thereby improving the cycle stability of lithium metal batteries under high current density and high voltage conditions.

[0075] Furthermore, the heating temperature for heating the liquid precursor is 50℃-80℃, and the heating time is 2-12h.

[0076] Specifically, the heating temperature determines the decomposition rate of the initiator and the rate of free radical generation. Below 50°C, the initiator decomposes too slowly, resulting in insufficient free radical generation and incomplete polymerization initiation. The carbon-carbon double bonds of the polymerizable ionic liquid monomers and fluorinated acrylate monomers do not open completely, leading to slow polymer chain growth. Sufficient monomer conversion cannot be achieved within the set time, resulting in an incomplete fluorinated polycationic crosslinking network structure and the inability to effectively fix the eutectic ion-conducting phase within the network. Above 80°C, the initiator decomposes too quickly, generating a large number of free radicals in a short time. The polymerization rate is too high, and polymer chains grow too rapidly in localized areas, potentially leading to uneven crosslinking density distribution in the fluorinated polycationic crosslinking network. Some areas may be over-crosslinked while others are under-crosslinked, affecting the overall performance of the gel polymer electrolyte. Furthermore, excessively high temperatures may have potential thermal effects on the eutectic solvent and lithium salt. When the heating time is less than 2 hours, the initiator has not fully decomposed, resulting in low monomer conversion and a large amount of unreacted monomer remaining in the system, leading to an incomplete fluorinated polycationic crosslinking network structure. When the heating time exceeds 12 hours, the polymerization reaction is essentially complete. Excessive heating time offers limited improvement in monomer conversion but may expose the eutectic solvent and lithium salt to high temperatures for extended periods, increasing the risk of potential thermal effects. Therefore, in this embodiment, the heating temperature is 50-80°C, and the heating time is 2-12 hours. Within this temperature and time range, the initiator continuously decomposes at a suitable rate to generate free radicals, initiating the gradual opening of carbon-carbon double bonds in the polymerizable ionic liquid monomer and fluorinated acrylate monomers, leading to continuous addition reactions. The polymerization reaction proceeds smoothly, monomer conversion is sufficient, the fluorinated polycationic crosslinking network structure is complete and uniform, and the eutectic ion-conducting phase is fully immobilized within the fluorinated polycationic crosslinking network.

[0077] More specifically, within the aforementioned heating temperature and time range, the heating temperature causes the initiator to decompose at a suitable rate, allowing free radicals to continuously and steadily initiate the polymerization reaction. After polymerization, the polymerizable ionic liquid monomers allow cationic structures to enter the polymer backbone, forming fixed cationic sites and constituting a polycationic backbone. Fluorinated acrylate monomers introduce fluorinated side chains after polymerization. Crosslinking agents form crosslinking points between polymer chains, constructing a fluorinated polycationic crosslinked network. The eutectic ion-conducting phase is fixed within this network, simultaneously forming a tight solid-solid interface at the electrode interface. The polymerization reaction is thorough, with minimal monomer residue, and the fluorinated polycationic crosslinked network structure is uniform and complete, thus ensuring batch-to-batch consistency and repeatability of the resulting gel polymer electrolyte in terms of ionic conductivity, lithium transference number, and interfacial film-forming ability.

[0078] Optionally, the heating temperature may be at least one range from 50-55°C, 55-60°C, 60-65°C, 65-70°C, 70-75°C, and 75-80°C, or a combination of at least two ranges, or any value from 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, and 80°C; the heating time may be at least one range from 2-4h, 4-6h, 6-8h, 8-10h, and 10-12h, or a combination of at least two ranges, or a combination of continuous ranges, or any value from 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, and 12h, as long as the polymerization reaction is fully carried out and the fluorinated polycationic crosslinked network structure is complete and uniform. This embodiment does not impose any restrictions on this.

[0079] To further verify the synergistic effect of each component in the gel polymer electrolyte of the present invention, test batteries with different electrolyte systems were prepared using lithium metal as the negative electrode and NCM811 as the positive electrode, and four tests were performed on ionic conductivity, lithium ion transport number, oxidation stability window and critical current density.

[0080] Experimental Example 1: Preparation of Gel Polymer Electrolytes I. Construction of Gel Polymer Electrolyte Precursor System Step 1: Preparation of deep eutectic ion-conducting phase: In an inert atmosphere glove box with moisture and oxygen content both below 0.1 ppm, weigh 1.00 g of succinate and 0.60 g of lithium bis(trifluoromethanesulfonyl)imide, place them in a clean glass bottle, and stir at 40°C until a clear and transparent deep eutectic electrolyte phase is formed.

[0081] Step 2: Preparation of the gel precursor: Add 0.80 g of 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 0.20 g of hexafluorobutyl acrylate, 10.0 mg of N,N-methylenebisacrylamide, and 3.0 mg of azobisisobutyronitrile to the above eutectic electrolyte phase, and continue stirring until homogeneous to obtain a liquid precursor. In the above formulation, the mass ratio of succinate to lithium bis(trifluoromethanesulfonyl)imide is 1.67:1, the mass ratio of 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt to hexafluorobutyl acrylate is 4:1, and the crosslinking agent and initiator are approximately 1% and 0.3% of the total mass of polymerizable monomers, respectively.

[0082] II. Battery Assembly and In-situ Polymerization Step 3: Drop or inject the above liquid precursor between the separator, positive electrode channels, and negative electrode interface to ensure full wetting. For CR2032 coin cells, the liquid precursor injection volume can be 40 μL; for pouch or stacked cells, the injection volume can be calculated based on the cell capacity. After assembly, allow to stand for 2 hours, then heat at 65°C for 6 hours to allow the polymerizable cationic monomer, fluorinated acrylate monomer, and crosslinking agent to undergo free radical polymerization, forming a gel polymer electrolyte in situ inside the battery.

[0083] III. Performance Testing Step 4: The obtained gel polymer electrolyte was used for electrochemical performance testing, including ionic conductivity, lithium-ion transference number, linear sweep voltammetry, critical current density, and full-cell cycle performance. The test results are as follows: at 30°C, the ionic conductivity was 1.61 mS / cm, the lithium-ion transference number was 0.76, the oxidation stability window was 5.08 V, the critical current density was 2.7 mA / cm², and the Li / NCM811 battery retained 72.1% of its capacity after 200 cycles at 2.8–4.5 V.

[0084] Experimental Example 2: Adjustment of Polymerizable Monomer Ratio The only difference from Example 1 is the adjustment of the mass ratio of 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt to hexafluorobutyl acrylate; all other components and preparation conditions remain unchanged. Specifically, the mass ratio can be set to 1:1, 2:1, and 5:1, respectively. Correspondingly, when the total mass of polymerizable monomers remains at 1.00 g, the content of each component is 0.50 g in the 1:1 formulation, 0.67 g and 0.33 g in the 2:1 formulation, and 0.83 g and 0.17 g in the 5:1 formulation.

[0085] In-situ polymerization and battery assembly were performed according to the method in Example 1, and the effect of different monomer ratios on electrochemical performance was tested. The test results are recorded in the table below.

[0086] Experimental Example 3: Structural Regulation of Polymerizable Cationic Monomers The only difference from Example 1 is that 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is replaced with an equal mass of 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide salt, while the other components and preparation conditions remain unchanged.

[0087] Experiment Example 4: Adjustment of Deep Eutectic Solvent The only difference from Example 1 is that succinic anion is replaced with an equal mass of N-methylacetamide, while the other components and preparation conditions remain unchanged.

[0088] Experiment Example 5: Temperature Regulation The only difference from Example 1 is that the heating temperature is set to 80°C, while the other components and preparation conditions remain unchanged.

[0089] Comparative Example 1: Gel system without added fluorinated acrylate monomers Except for the omission of hexafluorobutyl acrylate and the adjustment of the amount of 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt to 1.00 g, the remaining steps were the same as in Example 1. This comparative example is used to illustrate the role of the fluorinated side chain in lithium-ion coordination regulation and interfacial film stability.

[0090] Comparative Example 2: Gel system without polymerizable cationic monomer Except for the omission of 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and the adjustment of the hexafluorobutyl acrylate dosage to 1.00 g, the remaining steps were the same as in Example 1. This comparative example is used to illustrate the effect of the polycationic backbone on anion enrichment and anion migration restriction.

[0091] Comparative Example 3: Liquid system without in-situ polymerization The difference from Example 1 is that the initiator azobisisobutyronitrile (AIBN) is not added, and the battery is not heated and cured after assembly. The remaining components and proportions remain unchanged, resulting in an unpolymerized liquid electrolyte system. This comparative example illustrates the role of the fluorinated polycationic crosslinking network formed by in-situ polymerization in fixing the deep eutectic liquid phase, limiting long-range anion migration, improving electrode / electrolyte interface stability, and enhancing battery cycle performance.

[0092] Comparative Example 4: The only difference from Experimental Example 1 is that the amount of succinic acid was adjusted to 0.10 g.

[0093] After the test batteries for Experiments 1-5 and Comparative Examples 1-4 were assembled, their performance was tested. 1. Ionic conductivity test The ionic conductivity of the prepared electrolyte was tested under different temperature conditions (30~80℃), and the ionic conductivity and ion transport activation energy were obtained by linear fitting according to the Arrhenius relation.

[0094] 2. Lithium-ion transference number test The lithium-ion transference number was determined using a combination of DC polarization and AC impedance.

[0095] 3. Linear sweep voltammetry test The oxidation stability window of the electrolyte was determined by taking the potential corresponding to a current of 20 μA as the oxidation stability potential.

[0096] 4. Critical current density test Assemble a lithium-ion symmetric cell at 0.5 mA / cm². 2 Current density and 0.5 mAh / cm 2Constant current lithium plating / stripping cycle tests were conducted under areal capacity conditions to determine the critical current density.

[0097] The test results of Experimental Examples 1-5 and Comparative Examples 1-4 are summarized in Table 1: Table 1 shows the performance comparison between the experimental examples and the comparative examples.

[0098] Combination Figure 6 , Figure 6The ionic conductivity of the electrolytes prepared in Example 1 and Comparative Example 1 of this invention was tested under different temperature conditions (30~80℃), and the results were linearly fitted according to the Arrhenius relation. As shown in the figure, the ionic conductivity of both electrolytes increases with increasing temperature, and Example 1 exhibits higher ionic conductivity than Comparative Example 1 throughout the entire test temperature range. At 30℃, the ionic conductivity of Example 1 was 1.61 mS / cm, and that of Comparative Example 1 was 0.83 mS / cm. The fitted ionic transport activation energies of Example 1 and Comparative Example 1 were 0.146 eV and 0.168 eV, respectively, indicating that the fluorinated polycationic network constructed with the participation of fluorinated comonomers can reduce the ion migration energy barrier and promote the rapid transport of lithium ions in the gel polymer electrolyte. Corresponding to Table 1, the ionic conductivity of Example 1 was 1.61 mS / cm, higher than that of Comparative Example 1 (0.83 mS / cm) and Comparative Example 2 (0.88 mS / cm). In Example 2, when the mass ratio of the polymerizable ionic liquid monomer to the fluorinated acrylate monomer was 1:1, the ionic conductivity was 0.77 mS / cm. This increased to 1.03 mS / cm at a mass ratio of 2:1 and 1.44 mS / cm at a mass ratio of 5:1, all lower than the 1.61 mS / cm observed in Example 1 at a mass ratio of 4:1. In Example 3, 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide salt was used to replace the polymerizable cationic monomer in Example 1, and the ionic conductivity was 1.22 mS / cm, indicating that replacing the alkyl substituent of the imidazolium cation still resulted in a gel polymer electrolyte with high ionic conductivity. In Example 4, N-methylacetamide was used to replace succinate, and the ionic conductivity was 1.33 mS / cm, indicating that amide-based deep eutectic solvents can also form deep eutectic electrolyte phases with lithium salts and provide effective lithium-ion conduction channels. In Experiment 5, the heating temperature was set to 80℃, and the ionic conductivity was 1.44 mS / cm, indicating that the polymerization reaction could still proceed smoothly at 80℃. Comparative Example 3, which did not undergo in-situ polymerization, had an ionic conductivity of 2.08 mS / cm, indicating that the unpolymerized liquid system had a high apparent ionic conductivity due to its high fluidity; however, this result does not reflect its ionic selectivity and interfacial stability. In Comparative Example 4, the amount of succinic anion was adjusted to 0.10 g, and the ionic conductivity was only 0.27 mS / cm, indicating that when the amount of eutectic solvent was too low, the volume of the eutectic ion-conducting phase was insufficient, the lithium-ion conduction channels were discontinuous, and the ionic conductivity decreased significantly.

[0099] In the lithium-ion transport number test, the lithium-ion transport number of Example 1 was 0.76, Comparative Example 1 was 0.51, and Comparative Example 2 was 0.43. In Example 2, the lithium-ion transport number was 0.74 at a mass ratio of 5:1, 0.71 at a mass ratio of 2:1, and decreased to 0.60 at a mass ratio of 1:1. Comparative Example 2, without the addition of a polymerizable cationic monomer, had a lithium-ion transport number of only 0.43, which differed from Example 1 by 0.33. This indicates that the fixed cationic sites in the polycationic backbone play a key role in increasing the lithium transport number, and the lithium transport number decreases as the proportion of polymerizable ionic liquid monomer decreases. The lithium-ion transport number of Experimental Example 3 was 0.73, close to 0.76 in Experimental Example 1, indicating that after replacing 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt with 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide salt, the polycationic backbone can still effectively enrich and restrict the long-range migration of anions. The lithium-ion transference number (LTL) of Example 4 was 0.67, indicating that the gel polymer electrolyte still exhibited a high LTL when N-methylacetamide was used as the eutectic solvent. The LTL of Example 5 was 0.62, indicating that the gel polymer electrolyte formed at 80°C could effectively confine anions. Although Comparative Example 3 had a high ionic conductivity, its LTL was only 0.50, significantly lower than Examples 1-5, indicating that the unpolymerized cationic monomer was in a migratory state and could not effectively restrict anion migration. These results demonstrate that the polycationic backbone formed by in-situ polymerization is the key structure for increasing the LTL; the LTL of Comparative Example 4 was 0.44, indicating that when the amount of eutectic solvent was too low, the lithium-ion solvation structure was disrupted, and the LTL also decreased.

[0100] Combination Figure 7 , Figure 7The results of linear sweep voltammetry tests on the electrolytes prepared in Example 1 and Comparative Example 1 of this invention are shown. The potential corresponding to a current of 20 μA is taken as the oxidation stability potential. The oxidation stability window of the electrolyte in Example 1 reaches 5.08 V, higher than that of Comparative Example 1 (4.75 V), indicating that the gel polymer network constructed with fluorinated monomers can suppress the oxidative decomposition of the electrolyte at high potentials. According to Table 1, the oxidation stability windows in Example 2 with monomer mass ratios of 1:1, 2:1, and 5:1 are 5.11 V, 5.03 V, and 4.96 V, respectively, generally showing a decreasing trend with decreasing proportions of fluorinated monomers. The oxidation stability window of Example 3 is 5.11 V, indicating that the gel polymer electrolyte still has good high-voltage resistance after changing the alkyl substituent of the imidazolium cation. The oxidation stability window of Example 4 is 4.98 V, indicating that the gel polymer electrolyte still has good oxidation stability when N-methylacetamide is used as the deep eutectic solvent. The oxidation stability window of Example 5 was 5.04 V, indicating that the gel polymer electrolyte formed at a heating temperature of 80 °C still exhibited good high-voltage resistance. The oxidation stability window of Comparative Example 2 was 5.13 V, further demonstrating that fluorinated monomers are beneficial for improving oxidation stability; however, its lithium-ion transference number and critical current density were lower, and its overall performance was still weaker than that of Example 1. Comparative Example 3 did not form a polymer network, and its oxidation stability window was only 4.57 V, indicating that in-situ polymerization can reduce the free migration of active components and interfacial side reactions at high potentials, thereby improving the oxidation stability of the electrolyte. The oxidation stability window of Comparative Example 4 was 4.78 V, indicating that the oxidation stability of the electrolyte decreased when the amount of eutectic solvent was too low.

[0101] Combination Figure 8 , Figure 8 The lithium symmetric battery assembled using the electrolytes prepared in Example 1 and Comparative Example 1 was tested at 0.5 mA / cm. 2 Current density and 0.5 mA / cm 2 Results of constant current lithium plating / stripping cycle tests under areal capacity conditions. The battery in Example 1 maintained a low and stable polarization voltage throughout the approximately 1500 h cycling process, without significant voltage spikes. The polarization voltage of the battery in Comparative Example 1 gradually increased with cycling, exhibiting significant fluctuations and a rapid increase after approximately 220 h. These results indicate that the fluorinated polycationic network can promote the formation of a stable solid electrolyte interface film on the lithium metal surface, improve lithium-ion interfacial transport, and promote uniform lithium deposition, thereby suppressing interfacial side reactions and lithium dendrite growth. Corresponding to Table 1, the critical current density for Example 1 is 2.7 mA / cm². In Example 2, the critical current densities for monomer mass ratios of 1:1, 2:1, and 5:1 are 2.1 mA / cm², respectively. 2 2.5 mA / cm 2 and 2.2 mA / cm2 This indicates that a suitable ratio needs to be maintained between the polycation confinement effect and the fluorinated interface regulation effect. The critical current density of Example 3 was 2.4 mA / cm², showing that using 1-vinyl-3-ethylimidazolium monomers can also improve the current withstand capability of the lithium metal interface. The critical current density of Example 4 was 2.2 mA / cm², showing that when N-methylacetamide is used as a deep eutectic solvent, the gel polymer electrolyte can still effectively improve interface stability. The critical current density of Example 5 was 2.5 mA / cm², showing that the gel polymer electrolyte formed at a heating temperature of 80°C still has good interfacial film-forming ability. The critical current densities of Comparative Examples 1, 2, and 3 were 1.8 mA / cm², respectively. 2 1.6 mA / cm 2 and 1.2 mA / cm 2 Among them, Comparative Example 3 had the lowest value, indicating that without in-situ polymerization, the liquid system could not form a stable polycation network and mechanical constraints, and could not effectively suppress interfacial side reactions, uneven lithium deposition, and lithium dendrite growth. The critical current density of Comparative Example 4 was only 0.6 mA / cm², indicating that the amount of deep eutectic solvent was too low, resulting in a serious deficiency of the deep eutectic ion-conducting phase, discontinuous lithium-ion transport channels, and a significant decrease in interfacial stability.

[0102] Combination Figure 9 , Figure 9 The results show the cycle performance of the lithium / nickel-cobalt-manganese oxide battery assembled using the gel polymer electrolyte prepared in Example 1 within a voltage range of 2.8–4.5 V, where the areal loading of the positive electrode active material is 3.0 mg / cm², and the charge / discharge rate is 1 C. The initial discharge specific capacity of this battery is approximately 175 mAh / g, and the capacity retention after 200 cycles is 72.1%. Except for the initial activation stage, the overall coulombic efficiency is close to 100%. The results indicate that the gel polymer electrolyte of this invention can maintain a stable positive and negative electrode interface and reversible lithium-ion transport at a relatively high cutoff voltage, exhibiting good high-voltage full-cell cycle stability. Corresponding to Table 1, the Li / NCM811 battery of Example 1 retains a capacity retention of 72.1% after 200 cycles at 2.8–4.5 V.

[0103] In summary, the synergistic effect of the eutectic ion-conducting phase and the fluorinated polycationic crosslinking network simultaneously improves lithium transference number, reduces transport resistance, delays lithium-ion depletion at the lithium anode interface, and constructs a dense and stable inorganic-rich interface, enhancing the cycle stability of lithium metal batteries under high current density and high voltage conditions, without simply relying on high salt concentrations or free ionic liquids. The adjustment of alkyl substituents in polymerizable cationic monomers, the substitution of amide-based eutectic solvents, and the adoption of a heating temperature of 80°C did not disrupt the aforementioned synergistic mechanism, and the resulting gel polymer electrolyte maintained good overall performance. In contrast, the liquid system without in-situ polymerization and the system with excessively low eutectic solvent content showed significant deterioration in key performance aspects such as lithium transference number, oxidation stability window, and critical current density, further confirming that the fluorinated polycationic crosslinking network formed by in-situ polymerization and a sufficient eutectic ion-conducting phase are necessary conditions for achieving the aforementioned synergistic effects.

[0104] The third embodiment of the present invention provides a lithium battery, the lithium battery comprising a positive electrode, a negative electrode, a separator, and a gel polymer electrolyte as described in any one of the first embodiments.

[0105] Specifically, the negative electrode can be lithium metal, lithium alloy, graphite, silicon carbide, or a pre-lithiated negative electrode, preferably a lithium metal negative electrode. The positive electrode can be lithium iron phosphate, lithium cobalt oxide, nickel-cobalt-manganese ternary materials, high-nickel NCM811, nickel-cobalt-aluminum materials, or other positive electrode materials. A separator is disposed between the positive and negative electrodes, and a gel polymer electrolyte fills the pores between the positive electrode, the negative electrode, and the separator.

[0106] More specifically, during battery charging and discharging, the eutectic ion-conducting phase in the gel polymer electrolyte provides a continuous conduction channel and lithium salt dissolution environment for lithium ions, reducing transport resistance and delaying lithium ion depletion at the lithium anode interface without relying on high salt concentrations or free ionic liquids. The polycationic backbone in the fluorinated polycationic crosslinking network increases the lithium transference number and reduces concentration polarization by fixing cation sites, enriching them, and restricting long-range anion migration. Simultaneously, the enriched anions construct an anion-rich solvation structure, promoting preferential participation of anions in interfacial reactions at the lithium metal interface. The fluorinated side chains weaken excessively strong lithium-solvent coordination, lower the ion transport barrier, and synergistically promote the formation of a solid electrolyte interfacial film rich in inorganic components at the lithium metal anode interface with the anions enriched in the polycationic backbone. This interfacial film can suppress lithium dendrite growth and interfacial side reactions.

[0107] Therefore, the lithium battery provided in this embodiment utilizes the synergistic effect of the deep eutectic ion-conducting phase and the fluorinated polycation crosslinking network in the gel polymer electrolyte to form a dense and stable inorganic-rich solid electrolyte interface film at the lithium metal anode interface, effectively suppressing lithium dendrite growth and interface side reactions, thereby improving cycle stability under high current density and high voltage conditions.

[0108] The foregoing has provided a detailed description of a gel polymer electrolyte and its preparation method, as well as a lithium battery, disclosed in the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention. Any modifications, equivalent substitutions, and improvements made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A gel polymer electrolyte, characterized in that: It includes a fluorinated polycationic crosslinking network and a deep eutectic ion-conducting phase; wherein the deep eutectic ion-conducting phase includes a deep eutectic solvent and a lithium salt, and the fluorinated polycationic crosslinking network is formed by free radical polymerization of a polymerizable ionic liquid monomer, a fluorinated polymerizable monomer, and a crosslinking agent under the action of an initiator, wherein the fluorinated polymerizable monomer includes fluorinated acrylate monomers.

2. The gel polymer electrolyte as described in claim 1, characterized in that: The deep eutectic solvent includes at least one of succinic anion, glutaronitrile, adiponitrile, acetamide, N-methylacetamide, N,N-dimethylacetamide, sulfolane, ethylene carbonate, and tetraethylene glycol dimethyl ether.

3. The gel polymer electrolyte as described in claim 1, characterized in that: The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, lithium bis(oxalateborate), and lithium tetrafluoroborate.

4. The gel polymer electrolyte as described in claim 1, characterized in that: The cationic monomer in the polymerizable ionic liquid includes at least one of imidazolium, pyrrolidineium, piperidinium, quaternary ammonium salt cations, and quaternary phosphonium structure monomers having unsaturated carbon-carbon double bonds; the anionic monomer in the polymerizable ionic liquid includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalateborate.

5. The gel polymer electrolyte as described in claim 1, characterized in that: The fluorinated acrylate monomers include hexafluorobutyl acrylate, trifluoroethyl acrylate, tetrafluoropropyl methacrylate, and perfluoroalkyl ethyl methacrylate.

6. The gel polymer electrolyte as described in claim 1, characterized in that: The crosslinking agent includes at least one of N,N-methylenebisacrylamide, polyethylene glycol diacrylate pentaerythritol tetraacrylate, or trimethylolpropane triacrylate; the initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, and dicumyl peroxide.

7. The gel polymer electrolyte as described in claim 1, characterized in that: In the gel polymer electrolyte, the mass percentage of the deep eutectic solvent is 35%-65%, the mass percentage of the lithium salt is 15%-50%, the mass percentage of the polymerizable ionic liquid monomer is 3%-35%, the mass percentage of the fluorinated acrylate monomer is 1%-20%, the mass percentage of the crosslinking agent is 0.5%-3% of the total mass of the polymerizable ionic liquid monomer and the fluorinated acrylate monomer, and the mass percentage of the initiator is 0.1%-1% of the total mass of the polymerizable ionic liquid monomer and the fluorinated acrylate monomer.

8. A method for preparing a gel polymer electrolyte, characterized in that: The preparation of the gel polymer electrolyte as described in any one of claims 1-7 comprises the following steps: In an inert atmosphere or dry environment, a deep eutectic solvent is mixed with a lithium salt and heated and stirred to form a homogeneous and transparent deep eutectic ion-conducting phase. A polymerizable ionic liquid monomer, a fluorinated acrylate monomer, a crosslinking agent, and an initiator are added to the deep eutectic ion-conducting phase and mixed to obtain a liquid precursor. The liquid precursor is injected into the separator, electrode channels, or cell of the battery. The liquid precursor injected into the battery is heated, causing the polymerizable ionic liquid monomer, fluorinated polymerizable monomer, and crosslinking agent in the liquid precursor to undergo free radical polymerization under the action of an initiator, forming a fluorinated polycationic crosslinking network in situ inside the battery, and fixing the deep eutectic ion-conducting phase in the fluorinated polycationic crosslinking network to obtain a gel polymer electrolyte.

9. The method for preparing the gel polymer electrolyte as described in claim 8, characterized in that: The heating temperature for heating the liquid precursor is 50°C-80°C, and the heating time is 2-12 hours.

10. A lithium battery, characterized in that, The lithium battery includes a positive electrode, a negative electrode, a separator, and a gel polymer electrolyte as described in any one of claims 1-7.

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