In-situ polymerized ionic liquid copolymer electrolyte with high safety and preparation method and application thereof

Abstract

The application belongs to the technical field of lithium battery electrolyte, and discloses an in-situ polymerized high-safety ionic liquid copolymer electrolyte and a preparation method and application thereof. The method comprises the following steps: 1) uniformly mixing a double bond imidazole-based ionic liquid, ethylene carbonate, a lithium salt, a crosslinking agent and an initiator to obtain a copolymer precursor solution; and 2) placing the copolymer precursor solution on a film carrier of a battery, and polymerizing at 60-75 DEG C to obtain the high-safety ionic liquid copolymer electrolyte. The electrolyte of the application can inhibit the growth of lithium dendrites, has good ionic conductivity, provides a fast lithium ion transmission path, and realizes high safety and high cycle stability of the battery. The electrolyte of the application is used in lithium ion batteries, asymmetric lithium metal batteries or symmetric batteries.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical lithium battery technology, specifically relating to an in-situ polymerized ionic liquid copolymer electrolyte with high safety, its preparation method, and its application. Background Technology

[0002] With the ever-increasing demand for high-energy-density batteries, lithium metal batteries are considered one of the most promising next-generation energy storage technologies due to their lowest reduction potential (-3.04V vs standard hydrogen electrode) and highest specific capacity (3860mAh g⁻¹). However, the volatility, flammability, and leakage of traditional organic liquid electrolytes, as well as the uncontrollable growth of lithium dendrites during charging and discharging in lithium metal batteries, have led to a series of serious safety hazards.

[0003] As an alternative to organic liquid electrolytes, solid-state electrolytes can effectively suppress the growth of lithium dendrites and improve battery safety. Currently, solid-state electrolytes are divided into inorganic solid-state electrolytes and polymer electrolytes. Among them, polymer electrolytes have attracted much attention due to their high flexibility, light weight, ease of processing, and low cost. However, the flame retardancy of traditional polymer matrices is also relatively poor, and their safety needs to be improved.

[0004] Polyionic liquids possess excellent thermal stability and flame retardancy, thus being considered as candidate materials for improving the safety performance of lithium-ion batteries. However, the repeating polar units in the polyionic liquid backbone generate numerous crystalline regions, resulting in low room-temperature ionic conductivity, which is insufficient to meet the requirements of high-performance batteries. Patent application CN 117543073 A discloses an ionic liquid-based cross-linked network structure polymer electrolyte with high ionic conductivity and mechanical properties, and its preparation. The prepared electrolyte membrane exhibits good ionic conductivity and a wide electrochemical stability window; however, the preparation of the polymer electrolyte requires the extensive use of high-purity organic solvents, posing significant safety risks. Patent application CN 117747933 A discloses a dual-ionic liquid-based gel polymer electrolyte membrane and its preparation method. Although this overcomes the problem of requiring large amounts of organic solvents in the preparation of ionic liquid-based gel polymer electrolyte membranes, the poor contact between the electrolyte and the electrode leads to low capacity and unstable cycling of the assembled solid-state battery.

[0005] In summary, current technologies for preparing polymer electrolytes are still imperfect. Therefore, how to enhance the compatibility between the electrolyte and the electrode while ensuring its high electrochemical performance is an urgent problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention aims to provide an in-situ polymerized ionic liquid copolymer electrolyte with high safety, its preparation method, and its applications. This invention directly copolymerizes a double-bonded imidazole ionic liquid and ethylene ethylene carbonate inside the battery to prepare a high-safety ionic liquid copolymer electrolyte in situ. This also yields a battery with good performance, ensuring high electrochemical performance while enhancing the tight contact between the electrolyte and the electrode, resulting in reduced interfacial impedance and improved solid-state lithium battery performance. The method of this invention is simple and efficient, simplifying battery assembly processes, and achieves solvent-free and low-cost operation, showing broad application prospects.

[0007] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0008] A method for preparing an in-situ polymerized ionic liquid copolymer electrolyte with high safety includes the following steps:

[0009] 1) Mix the double-bonded imidazole ionic liquid, ethylene carbonate, lithium salt, crosslinking agent and initiator to obtain a copolymer precursor solution;

[0010] 2) The copolymer precursor solution is placed on the membrane carrier of the battery and polymerized at 60-75°C to obtain an ionic liquid copolymer electrolyte with high safety.

[0011] The structure of the double-bonded imidazole ionic liquid is as follows:

[0012]

[0013] Wherein R is one of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl, and X is one of chlorine, bromine, iodine, bis(trifluoromethanesulfonyl)imide, and bis(trifluoromethanesulfonyl)imide. Preferably, R is butyl and X is bis(trifluoromethanesulfonyl)imide.

[0014] The molar ratio of the double-bonded imidazole ionic liquid to ethylene carbonate is 1:1 to 7. Preferably, the molar ratio is 1:(2 to 4).

[0015] The lithium salt comprises one or more of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalatoborate)borate (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), and lithium nitrate (LiNO3), preferably one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluorooxalatoborate (LiDFOB). The concentration of the lithium salt in the mixture of double-bonded imidazole ionic liquid and ethylene carbonate is 0.1–4 mol / L, preferably 0.5–2 mol / L.

[0016] The crosslinking agent includes one or more of polyethylene glycol diacrylate, pentaerythritol triacrylate, propylene glycol di(meth)acrylate, and trimethylolpropane triacrylate.

[0017] The crosslinking agent accounts for 5-20% of the total mass of the copolymer precursor solution.

[0018] The initiator is azobisisobutyronitrile (AIBN), and the amount added is 0.1-2% of the total mass of the double-bonded imidazole ionic liquid, ethylene ethylene carbonate, and crosslinking agent.

[0019] The polymerization time in step 2) is 4 to 8 hours.

[0020] The specific steps for step 2) are as follows:

[0021] The copolymer precursor solution is placed on the membrane carrier of the battery and polymerized at 60–75°C, and then the battery is assembled. Alternatively, the copolymer precursor solution is placed on the membrane carrier of the battery, the battery is assembled, and polymerized at 60–75°C to obtain an ionic liquid copolymer electrolyte with high safety.

[0022] Placing the copolymer precursor solution on the battery membrane carrier refers to a coating or impregnation method.

[0023] After the battery assembly is completed in step 2), let it stand at room temperature for 8–24 hours.

[0024] When the battery is a lithium-ion battery, the specific steps of step 2) are as follows: place the copolymer precursor solution on the membrane carrier of the battery, assemble the battery, polymerize at 60-75°C, and let it stand at room temperature.

[0025] When the battery is an asymmetric lithium metal battery or a symmetric battery, step 2) specifically involves placing the copolymer precursor solution on the battery membrane carrier, polymerizing it at 60-75°C, then assembling the battery and allowing it to stand at room temperature.

[0026] Step 1) involves mixing under a protective atmosphere.

[0027] The membrane carrier mentioned in step 2) is one of polyvinylidene fluoride-hexafluoropropylene porous membrane, glass fiber membrane, or polypropylene membrane (PP). The membrane porosity is 40-80%, and the pore size is 1-6 μm.

[0028] When the battery is a lithium-ion battery, the positive electrode includes any one of NCM ternary, lithium iron phosphate, and lithium cobalt oxide.

[0029] The highly safe ionic liquid copolymer electrolyte is obtained by the above method.

[0030] The highly safe ionic liquid copolymer electrolyte is used in lithium-ion batteries, asymmetric lithium metal batteries, or symmetric batteries.

[0031] The technical solution of this invention has the following beneficial effects:

[0032] (1) The use of double-bonded imidazole ionic liquids can effectively improve the thermal stability of electrolytes, increase the electrochemical stability of electrolytes, and effectively inhibit the growth of lithium dendrites.

[0033] (2) Introducing low-viscosity ethylene carbonate can reduce the crystallinity of the polymer, enhance ion mobility, and promote the dissociation of lithium salt, which can further increase the ionic conductivity of the copolymer; at the same time, the coordination of ethylene carbonate with lithium ions accelerates the ion migration rate.

[0034] (3) The mixture polymerizes to form a three-dimensional cross-linked network copolymer. This cross-linked network structure is beneficial to improving the flexibility and mechanical strength of the electrolyte, while providing a fast lithium-ion transport path.

[0035] (4) The double-bonded imidazole ionic liquid and ethylene carbonate are copolymerized in situ, which not only enhances the interfacial contact between the electrode and the electrolyte and reduces the internal resistance of the battery, but also greatly improves the flame retardant performance of the electrolyte, thereby achieving high safety and high cycle stability of lithium metal batteries. Attached Figure Description

[0036] Figure 1 The AC impedance spectra of the high-safety ionic liquid copolymer electrolyte of Example 3, which was polymerized in situ, at different temperatures;

[0037] Figure 2 Linear sweep voltammetry curves of the in-situ polymerized high-safety ionic liquid copolymer electrolyte of Example 3;

[0038] Figure 3 For the lithium symmetric battery based on the in-situ polymerized high-safety ionic liquid copolymer electrolyte of Example 3, at room temperature, 0.2 mA·cm 2 Long-cycle curves at current density;

[0039] Figure 4 The image shows the long cycle curve of a lithium iron phosphate battery based on the in-situ polymerized high-safety ionic liquid copolymer electrolyte of Example 3 at room temperature and 1C rate. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto. In the embodiments, the polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) porous membrane is prepared by phase transfer method, and the specific steps are as follows:

[0041] S1) Dissolve the PVDF-HFP polymer in acetone at a mass ratio of 1:(8-15) and stir continuously at 55-65°C for 2.5-4 hours to obtain a transparent and homogeneous solution;

[0042] S2) Under stirring conditions (stirring speed of 300-900 r / min), water is added dropwise as a pore-forming agent. The amount of water added is (5-7)% of the polymer mass, and the dropping speed is 1 drop / 1-2 s to obtain a suspension. The suspension is coated on the surface of a clean polytetrafluoroethylene plate and allowed to dry naturally for 6 hours to allow acetone to evaporate.

[0043] S3) After vacuum drying at 75-85℃ for 10-14h, a dried PVDF-HFP porous membrane with a thickness of 50-150μm is obtained.

[0044] Example 1

[0045] (1) Preparation of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) porous membrane: First, PVDF-HFP polymer was dissolved in acetone at a mass ratio of 1:10 and stirred continuously at 60°C for 3 hours to obtain a transparent and homogeneous solution. Then, under stirring at 600 rpm, deionized water was added dropwise as a pore-forming agent, with the amount of water added being 6% of the polymer mass, to obtain a suspension. The suspension was coated on the surface of a clean polytetrafluoroethylene plate and allowed to dry naturally for 6 hours to allow the acetone to evaporate. Finally, after vacuum drying at 80°C for 12 hours, a dry PVDF-HFP porous membrane with a thickness of 50–150 μm was obtained. The porosity was 75%, and the pore size was 5 μm.

[0046] (2) Preparation of copolymer precursor solution

[0047] In a glove box filled with high-purity argon, 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide salt and ethylene ethylene carbonate were mixed uniformly at a molar ratio of 1:1. Then, 1 mol / L of lithium bis(trifluoromethanesulfonyl)imide (the concentration of lithium salt in the mixture of double-bonded imidazolium ionic liquid and ethylene ethylene carbonate was 1 mol / L), 10% by mass of polyethylene glycol diacrylate crosslinking agent (the mass percentage of the crosslinking agent was 10% of the total mass of the copolymer precursor solution), and 0.5 wt% of AIBN initiator (the amount of initiator added was 0.5% of the sum of the mass of double-bonded imidazolium ionic liquid, ethylene ethylene carbonate, and crosslinking agent) were stirred to obtain a uniform copolymer precursor solution.

[0048] (3) Preparation of copolymer electrolytes

[0049] The copolymer precursor solution was injected into a PVDF-HFP porous membrane carrier for thorough wetting (20 minutes). The wetting carrier was then placed on a polytetrafluoroethylene (PTFE) plate and heated at 70°C for 5 hours to obtain a self-supporting, high-safety ionic liquid copolymer electrolyte (CPE). Stainless steel symmetric cells (SS / CPE / SS), lithium symmetric cells (Li / CPE / Li), and stainless steel / lithium coin cells (SS / CPE / Li) were assembled in a glove box. The cells were tested after standing for 12 hours.

[0050] The polymer electrolyte membrane in this embodiment has an ionic conductivity of 8.25 × 10⁻⁶ at room temperature. -4 S cm -1 .

[0051] Example 2

[0052] (1) Preparation of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) porous membrane: Same as in Example 1;

[0053] (2) Preparation of copolymer precursor solution: In a glove box filled with high-purity argon, 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide salt and ethylene ethylene carbonate were mixed uniformly at a molar ratio of 1:2; then 1 mol / L lithium bis(trifluoromethanesulfonyl)imide, 10% polyethylene glycol diacrylate crosslinking agent and 0.5 wt% AIBN initiator were added sequentially, and the mixture was stirred to obtain a uniform copolymer precursor solution;

[0054] (3) Preparation of copolymer electrolytes

[0055] The copolymer precursor solution was injected into a PVDF-HFP porous membrane carrier for full impregnation. The impregnated membrane carrier was then placed on a polytetrafluoroethylene plate and heated at 70°C for 5 hours to obtain a self-supporting, high-safety ionic liquid copolymer electrolyte (CPE). Stainless steel symmetric cells (SS / CPE / SS), lithium symmetric cells (Li / CPE / Li), and stainless steel / lithium button cells (SS / CPE / Li) were assembled in a glove box. The cells were then tested after standing for 12 hours.

[0056] The polymer electrolyte membrane in this embodiment has an ionic conductivity of 6.14 × 10⁻⁶ at room temperature. -4 S cm -1 .

[0057] Example 3

[0058] (1) Preparation of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) porous membrane: Same as in Example 1;

[0059] (2) Preparation of copolymer precursor solution

[0060] In a glove box filled with high-purity argon, 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide salt and ethylene ethylene carbonate were added to a glass bottle at a molar ratio of 1:3 and mixed thoroughly. Then, 1 mol / L lithium bis(trifluoromethanesulfonyl)imide, 10% polyethylene glycol diacrylate crosslinking agent, and 0.5 wt% AIBN initiator were added sequentially and stirred to obtain a homogeneous copolymer precursor solution.

[0061] (3) Preparation of copolymer electrolytes

[0062] The copolymer precursor solution was injected into a PVDF-HFP porous membrane carrier for full impregnation. The impregnated membrane carrier was then placed on a polytetrafluoroethylene plate and heated at 70°C for 5 hours to obtain a self-supporting high-safety ionic liquid copolymer electrolyte (CPE). Stainless steel symmetric cells (SS / CPE / SS), lithium symmetric cells (Li / CPE / Li), stainless steel / lithium button cells (SS / CPE / Li), and lithium iron phosphate cells (LFP / CPE / Li) were assembled in a glove box. The cells were then allowed to stand for 12 hours before testing.

[0063] The polymer electrolyte membrane in this embodiment has an ionic conductivity of 4.87 × 10⁻⁶ at room temperature. -4 S cm -1 .

[0064] Example 4

[0065] (1) Preparation of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) porous membrane: Same as in Example 1;

[0066] (2) Preparation of copolymer precursor solution

[0067] In a glove box filled with high-purity argon, 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide salt and ethylene ethylene carbonate were added to a glass bottle at a molar ratio of 1:4 and mixed thoroughly. Then, 1 mol / L lithium bis(trifluoromethanesulfonyl)imide, 10% polyethylene glycol diacrylate crosslinking agent, and 0.5 wt% AIBN initiator were added sequentially and stirred to obtain a homogeneous copolymer precursor solution.

[0068] (3) Preparation of copolymer electrolytes

[0069] The copolymer precursor solution was injected into the PVDF-HFP porous membrane carrier for full impregnation. The impregnated membrane carrier was then placed on a polytetrafluoroethylene plate and heated at 70°C for 5 hours to obtain a self-supporting high-safety ionic liquid copolymer electrolyte (CPE). Stainless steel symmetric cells (SS / CPE / SS), lithium symmetric cells (Li / CPE / Li), and stainless steel / lithium button cells (SS / CPE / Li) were assembled in a glove box. The cells were tested after standing for 12 hours.

[0070] The polymer electrolyte membrane in this embodiment has an ionic conductivity of 2.43 × 10⁻⁶ at room temperature. -4 S cm -1 .

[0071] Example 5

[0072] (1) Preparation of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) porous membrane: Same as in Example 1;

[0073] (2) Preparation of copolymer precursor solution

[0074] In a glove box filled with high-purity argon, 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide salt and ethylene ethylene carbonate were added to a glass bottle at a molar ratio of 1:6 and mixed thoroughly. Then, 1 mol / L lithium bis(trifluoromethanesulfonyl)imide, 10% polyethylene glycol diacrylate crosslinking agent, and 0.5 wt% AIBN initiator were added sequentially and stirred to obtain a homogeneous copolymer precursor solution.

[0075] (3) Preparation of copolymer electrolytes

[0076] The copolymer precursor solution was injected into a PVDF-HFP porous membrane carrier for full impregnation. The impregnated membrane carrier was then placed on a polytetrafluoroethylene plate and heated at 70°C for 5 hours to obtain a self-supporting, high-safety ionic liquid copolymer electrolyte (CPE). Stainless steel symmetric cells (SS / CPE / SS), lithium symmetric cells (Li / CPE / Li), and stainless steel / lithium button cells (SS / CPE / Li) were assembled in a glove box. The cells were then tested after standing for 12 hours.

[0077] The polymer electrolyte membrane in this embodiment has an ionic conductivity of 1.68 × 10⁻⁶ at room temperature. -4 S cm -1 .

[0078] Comparative Example 1

[0079] Without the addition of ethylene carbonate, and under the same conditions as in Example 1, the polymer electrolyte membrane exhibited an ionic conductivity of only 3.47 × 10⁻⁶ at room temperature. -4 S cm -1 .

[0080] Performance testing:

[0081] Electrochemical performance tests were performed on the in-situ polymerized high-safety ionic liquid copolymer electrolyte membrane prepared in Example 3: the ionic conductivity and LSV curves of the electrolyte prepared in Example 3 at different temperatures are shown below. Figure 1 and Figure 2As shown. A lithium-ion symmetric battery (Li / PE / Li) was tested on the Blue Battery testing system at room temperature and 0.2 mA·cm⁻¹. -2 The following long-loop test was performed, and the results are as follows: Figure 3 As shown. Long-cycle testing of lithium iron phosphate batteries (LFP / CPE / Li) at room temperature and 1C was conducted on the Blue Battery testing system, and the results are as follows. Figure 4 As shown.

[0082] Figure 1 The AC impedance spectra of the high-safety ionic liquid copolymer electrolyte of Example 3, which was polymerized in situ, at different temperatures;

[0083] Figure 2 Linear sweep voltammetry curves of the in-situ polymerized high-safety ionic liquid copolymer electrolyte of Example 3;

[0084] Figure 3 For the lithium symmetric battery based on the in-situ polymerized high-safety ionic liquid copolymer electrolyte of Example 3, at room temperature, 0.2 mA·cm 2 Long-cycle curves at current density;

[0085] Figure 4 The image shows the long cycle curve of a lithium iron phosphate battery based on the in-situ polymerized high-safety ionic liquid copolymer electrolyte of Example 3 at room temperature and 1C rate.

[0086] The cross-linked network structure electrolyte membrane of Example 3 exhibits an ionic conductivity of 4.87 × 10⁻⁶ at room temperature. -4 Scm -1 The electrochemical stability window is 5.4V, exhibiting a good lithium-ion transference number (0.435). This cross-linked network electrolyte membrane demonstrates strong suppression of lithium dendrites, maintaining stable cycling for over 780 hours with a polarization voltage less than 0.15V. The relatively flat peel-off electroplating curve indicates that the formation of a stable solid electrolyte interface layer on the lithium metal surface promotes uniform lithium deposition, effectively suppressing lithium dendrite growth. Furthermore, the assembled lithium iron phosphate battery underwent over 200 cycles at 1C at room temperature, exhibiting an average coulombic efficiency greater than 99.5% and a capacity retention of 91.8%, demonstrating the excellent cycling performance of this copolymer electrolyte and its broad application prospects in the field of high-safety flexible electronic devices.

Claims

1. A method for preparing an in-situ polymerized ionic liquid copolymer electrolyte with high safety, characterized in that: Includes the following steps: 1) Mix the double-bonded imidazole ionic liquid, ethylene carbonate, lithium salt, crosslinking agent and initiator to obtain a copolymer precursor solution; 2) The copolymer precursor solution is placed on the membrane carrier of the battery and polymerized at 60-75°C to obtain an ionic liquid copolymer electrolyte with high safety. The structure of the double-bonded imidazole ionic liquid is as follows: Where R is one of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl, and X is one of chlorine, bromine, iodine, bis(trifluoromethanesulfonyl)imide, and bis(trifluoromethanesulfonyl)imide; The molar ratio of the double-bonded imidazole ionic liquid to ethylene carbonate is 1:2 to 3; The lithium salt is one of lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalateborate; The crosslinking agent includes one or more of polyethylene glycol diacrylate, pentaerythritol triacrylate, propylene glycol di(meth)acrylate, and trimethylolpropane triacrylate; The initiator is azobisisobutyronitrile; The concentration of the lithium salt in the mixture of double-bonded imidazole ionic liquid and ethylene ethylene carbonate is 0.5–2 mol / L; the mass percentage of the crosslinking agent is 5–20% of the total mass of the copolymer precursor solution; and the amount of the initiator added is 0.1–2% of the sum of the mass of the double-bonded imidazole ionic liquid, ethylene ethylene carbonate, and crosslinking agent. The polymerization time in step 2) is 4–8 hours; The membrane carrier mentioned in step 2) is one of polyvinylidene fluoride-hexafluoropropylene porous membrane, glass fiber membrane, or polypropylene separator.

2. The method for preparing the in-situ polymerized ionic liquid copolymer electrolyte with high safety according to claim 1, characterized in that: In the structure of the double-bonded imidazole ionic liquid, R is butyl and X is bis(trifluoromethanesulfonyl)imide.

3. The method for preparing the highly safe ionic liquid copolymer electrolyte by in-situ polymerization according to claim 1, characterized in that: The mixing described in step 1) is carried out under a protective atmosphere.

4. The method for preparing the in-situ polymerized ionic liquid copolymer electrolyte with high safety according to claim 1, characterized in that: The specific steps for step 2) are as follows: The copolymer precursor solution is placed on the membrane carrier of the battery and polymerized at 60-75℃, and then the battery is assembled. Alternatively, the copolymer precursor solution is placed on the membrane carrier of the battery, the battery is assembled, and polymerized at 60-75℃ to obtain an ionic liquid copolymer electrolyte with high safety. Placing the copolymer precursor solution on the battery membrane carrier refers to a coating or impregnation method. After the battery assembly is completed in step 2), let it stand at room temperature for 8 to 24 hours.

5. The method for preparing the in-situ polymerized ionic liquid copolymer electrolyte with high safety according to claim 4, characterized in that: When the battery is a lithium-ion battery, the specific steps of step 2) are as follows: place the copolymer precursor solution on the membrane carrier of the battery, assemble the battery, polymerize at 60-75°C, and let it stand at room temperature. When the battery is an asymmetric lithium metal battery or a symmetric battery, step 2) specifically involves placing the copolymer precursor solution on the battery membrane carrier, polymerizing it at 60-75°C, then assembling the battery and allowing it to stand at room temperature.

6. The method for preparing the in-situ polymerized ionic liquid copolymer electrolyte with high safety according to claim 1, characterized in that: Step 1) involves mixing under a protective atmosphere; When the battery is a lithium-ion battery, the positive electrode in the assembled battery includes any one of NCM ternary, lithium iron phosphate, and lithium cobalt oxide.

7. A highly safe ionic liquid copolymer electrolyte obtained by the preparation method according to any one of claims 1 to 6.

8. The application of the highly safe ionic liquid copolymer electrolyte according to claim 7, characterized in that: The highly safe ionic liquid copolymer electrolyte is used in lithium-ion batteries, asymmetric lithium metal batteries, or symmetric batteries.

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