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

Abstract

The invention belongs to the technical field of lithium battery electrolytes, and discloses an in-situ polymerized high-safety ionic liquid copolymer electrolyte as well as a preparation method and application thereof. The method comprises the following steps: 1) uniformly mixing a double-bond imidazolyl ionic liquid, vinylethylene carbonate, a lithium salt, a cross-linking agent and an initiator to obtain a copolymer precursor solution; and 2) placing the copolymer precursor solution on a membrane carrier of a battery, and polymerizing at 60-75 DEG C to obtain the high-safety ionic liquid copolymer electrolyte. The electrolyte disclosed by the invention can well inhibit the growth of lithium dendrites, has relatively good ionic conductivity, provides a rapid lithium ion transmission path, and realizes high safety and high cycle stability of the battery. The electrolyte is used for a lithium ion battery, an asymmetric lithium metal battery or a symmetric battery.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical lithium batteries, and in particular relates to an in-situ polymerized ionic liquid copolymer electrolyte with high safety and a preparation method and application thereof. Background Art

[0002] With the growing 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 (-3.04 V vs standard hydrogen electrode) and highest specific capacity (3860 mAh g 1). However, the volatility, flammability, and leakage of traditional organic liquid electrolytes and the uncontrollable growth of lithium dendrites during the charge and discharge process of lithium metal batteries have led to a series of serious safety hazards.

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

[0004] Polyionic liquids have good thermal stability and flame retardancy, so they are considered to be one of the candidate materials for improving the safety performance of lithium batteries. However, the repeated polar units in the main chain of polyionic liquids will produce a large number of crystalline regions, resulting in low room temperature ionic conductivity. It is difficult to meet the requirements of high-performance batteries. Invention 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 has good ionic conductivity and a wide electrochemical stability window, but a large amount of high-purity organic solvents are required in the preparation of polymer electrolytes, which poses a great safety hazard. Invention patent application CN 117747933 A discloses a diionic liquid-based gel polymer electrolyte membrane and its preparation method. Although it overcomes the problem of using a large amount of organic solvents in the preparation of ionic liquid-based gel polymer electrolyte membranes, the contact between the electrolyte and the electrode is poor, resulting in a low capacity of the assembled solid-state battery and unstable cycles.

[0005] In summary, the existing technology for the preparation of polymer electrolytes is still imperfect. Therefore, how to ensure the high electrochemical performance of the electrolyte while enhancing its compatibility with the electrode is an urgent problem to be solved. Summary of the invention

[0006] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide an in-situ polymerized ionic liquid copolymer polymer electrolyte with high safety, and a preparation method and application thereof. The present invention directly copolymerizes double-bond imidazole ionic liquid and vinyl ethylene carbonate inside the battery to prepare a high-safety ionic liquid copolymer electrolyte in situ, and also obtains a battery with good performance. While ensuring high electrochemical performance, it also enhances the close contact between the electrolyte and the pole piece, resulting in a reduction in the interfacial impedance of the battery, thereby achieving an improvement in the performance of the solid-state lithium battery. The method of the present invention is simple and efficient, which is conducive to simplifying the battery assembly process, and also achieves solvent-free and low-cost, and has broad application prospects.

[0007] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

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

[0009] 1) mixing a double-bond imidazole-based ionic liquid, vinyl ethylene carbonate, a lithium salt, a crosslinking agent and an initiator to obtain a copolymer precursor solution;

[0010] 2) placing the copolymer precursor solution on a membrane carrier of a battery and polymerizing it at 60-75° C. to obtain an ionic liquid copolymer electrolyte with high safety.

[0011] The structure of the double bond imidazolyl ionic liquid is:

[0012]

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

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

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

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

[0017] The mass proportion of the cross-linking agent is 5-20% of the total mass of the copolymer precursor solution.

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

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

[0020] Specific steps of step 2):

[0021] The copolymer precursor solution is placed on a membrane carrier of a battery, polymerized at 60-75°C, and then the battery is assembled; or the copolymer precursor solution is placed on a membrane carrier of a 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 membrane support of the battery refers to a method of coating or impregnation.

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

[0024] When the battery is a lithium ion battery, the specific steps of step 2) are: placing the copolymer precursor solution on the membrane carrier of the battery, assembling the battery, polymerizing at 60-75° C., and standing at room temperature.

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

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

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

[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 ionic liquid copolymer electrolyte with high safety is obtained by the method.

[0030] The ionic liquid copolymer electrolyte with high safety is used in lithium ion batteries, asymmetric lithium metal batteries or symmetric batteries.

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

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

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

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

[0035] (4) The in-situ copolymerization of double-bond imidazolyl ionic liquid and vinyl ethylene carbonate not only enhances the interfacial contact between the electrode and the electrolyte and reduces the internal resistance of the battery, but also significantly improves the flame retardant properties of the electrolyte, thereby achieving high safety and high cycle stability of lithium metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0037] Figure 2 The linear sweep voltammetric curve of the in-situ polymerized high-safety ionic liquid copolymer electrolyte of Example 3;

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

[0039] Figure 4 This is a long cycle curve of a lithium iron phosphate battery using an in-situ polymerized high-safety ionic liquid copolymer electrolyte according to Example 3 at room temperature and a 1C rate. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with specific examples, but the embodiments of the present invention are not limited thereto. In the examples, the polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) porous membrane is prepared by a phase transfer method, specifically in the following steps:

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

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

[0043] S3) vacuum drying at 75-85° C. for 10-14 h to obtain a dry PVDF-HFP porous membrane with a thickness of 50-150 μm.

[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 at 60°C for 3 hours to obtain a transparent uniform solution; then, deionized water was added as a pore-forming agent at a stirring speed of 600 rpm to obtain a suspension; the suspension was coated on the surface of a clean polytetrafluoroethylene plate and dried naturally for 6 hours to allow acetone to evaporate; finally, a dry PVDF-HFP porous membrane with a thickness of 50 to 150 μm was obtained after vacuum drying at 80°C for 12 hours. 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-butylimidazole bistrifluoromethylsulfonyl imide salt and vinyl ethylene carbonate are mixed uniformly in a molar ratio of 1:1; then 1 mol / L of lithium bistrifluorosulfonyl imide (the concentration of lithium salt in the mixture of double-bonded imidazolyl ionic liquid and vinyl ethylene carbonate is 1 mol / L), 10% by weight of polyethylene glycol diacrylate crosslinker (the mass proportion of the crosslinker is 10% of the total mass of the copolymer precursor solution) and 0.5 wt% of AIBN initiator (the amount of the initiator added is 0.5% of the sum of the mass of the double-bonded imidazolyl ionic liquid, vinyl ethylene carbonate and the crosslinker) are added in sequence, and stirred to obtain a uniform copolymer precursor solution;

[0048] (3) Preparation of copolymer electrolyte

[0049] The copolymer precursor solution was injected into the PVDF-HFP porous membrane support for full infiltration (infiltration for 20 minutes), and then the infiltrated membrane support was 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 battery was tested after standing for 12 hours.

[0050] The ionic conductivity of the polymer electrolyte membrane of this embodiment at room temperature is 8.25×10 -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-butylimidazole bis(trifluoromethylsulfonyl)imide salt and vinyl ethylene carbonate were mixed in a molar ratio of 1:2; then 1 mol / L lithium bis(trifluorosulfonyl)imide, 10% by weight of polyethylene glycol diacrylate crosslinker and 0.5 wt% of AIBN initiator were added in sequence, and stirred to obtain a uniform copolymer precursor solution;

[0054] (3) Preparation of copolymer electrolyte

[0055] The copolymer precursor solution was injected into the PVDF-HFP porous membrane carrier to fully infiltrate it, and then the infiltrated membrane carrier was 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 batteries (SS / CPE / SS), lithium symmetric batteries (Li / CPE / Li) and stainless steel / lithium button batteries (SS / CPE / Li) were assembled in a glove box and the batteries were tested after standing for 12 hours.

[0056] The ionic conductivity of the polymer electrolyte membrane of this embodiment at room temperature is 6.14×10 -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-butylimidazole bistrifluoromethylsulfonyl imide salt and vinyl ethylene carbonate were added into a glass bottle at a molar ratio of 1:3 and mixed evenly; then 1 mol / L of lithium bistrifluorosulfonyl imide, 10% by weight of polyethylene glycol diacrylate crosslinker and 0.5 wt% of AIBN initiator were added in sequence and stirred to obtain a uniform copolymer precursor solution;

[0061] (3) Preparation of copolymer electrolyte

[0062] The copolymer precursor solution was injected into the PVDF-HFP porous membrane carrier to fully infiltrate it, and then the infiltrated membrane carrier was 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 batteries (SS / CPE / SS), lithium symmetric batteries (Li / CPE / Li), stainless steel / lithium button batteries (SS / CPE / Li) and lithium iron phosphate batteries (LFP / CPE / Li) were assembled in a glove box and the batteries were tested after standing for 12 hours.

[0063] The ionic conductivity of the polymer electrolyte membrane of this embodiment at room temperature is 4.87×10 -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-butylimidazole bistrifluoromethylsulfonyl imide salt and vinyl ethylene carbonate were added into a glass bottle at a molar ratio of 1:4 and mixed evenly; then 1 mol / L of lithium bistrifluorosulfonyl imide, 10% by weight of polyethylene glycol diacrylate crosslinker and 0.5 wt% of AIBN initiator were added in sequence and stirred to obtain a uniform copolymer precursor solution;

[0068] (3) Preparation of copolymer electrolyte

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

[0070] The ionic conductivity of the polymer electrolyte membrane of this embodiment at room temperature is 2.43×10 -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-butylimidazole bistrifluoromethylsulfonyl imide salt and vinyl ethylene carbonate were added into a glass bottle at a molar ratio of 1:6 and mixed evenly; then 1 mol / L of lithium bistrifluorosulfonyl imide, 10% by weight of polyethylene glycol diacrylate crosslinker and 0.5 wt% of AIBN initiator were added in sequence and stirred to obtain a uniform copolymer precursor solution;

[0075] (3) Preparation of copolymer electrolyte

[0076] The copolymer precursor solution was injected into the PVDF-HFP porous membrane carrier to fully infiltrate it, and then the infiltrated membrane carrier was 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 batteries (SS / CPE / SS), lithium symmetric batteries (Li / CPE / Li) and stainless steel / lithium button batteries (SS / CPE / Li) were assembled in a glove box and the batteries were tested after standing for 12 hours.

[0077] The ionic conductivity of the polymer electrolyte membrane of this embodiment at room temperature is 1.68×10 -4 S cm -1 .

[0078] Comparative Example 1

[0079] No ethylene carbonate was added, and other conditions were the same as in Example 1. The ionic conductivity of the polymer electrolyte membrane at room temperature was only 3.47×10 -4 S cm -1 .

[0080] Performance Testing:

[0081] The electrochemical performance of the in-situ polymerized high-safety ionic liquid copolymer electrolyte membrane prepared in Example 3 was tested: the ionic conductivity and LSV curve of the electrolyte prepared in Example 3 at different temperatures are as follows: Figure 1 and Figure 2As shown. The Lithium symmetric battery (Li / PE / Li) was tested on the Blue Battery Test System at room temperature and 0.2 mA cm -2 The long cycle test was carried out under Figure 3 The long cycle test of lithium iron phosphate battery (LFP / CPE / Li) was carried out at room temperature and 1C on the Blue Power Battery Test System. The results are shown in Figure 4 shown.

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

[0083] Figure 2 The linear sweep voltammetric curve of the in-situ polymerized high-safety ionic liquid copolymer electrolyte of Example 3;

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

[0085] Figure 4 This is a long cycle curve of a lithium iron phosphate battery using an in-situ polymerized high-safety ionic liquid copolymer electrolyte according to Example 3 at room temperature and a 1C rate.

[0086] The ionic conductivity of the cross-linked network structure electrolyte membrane of Example 3 at room temperature can reach 4.87×10 -4 Scm -1 , the electrochemical stability window is 5.4V, and it has a good lithium ion migration number (0.435). The cross-linked network structure electrolyte membrane has the ability to inhibit lithium dendrites. It can stably cycle for more than 780 hours, the polarization voltage is less than 0.15V, and the stripping electroplating curve is relatively flat, indicating that it forms a stable solid electrolyte interface layer on the lithium metal surface, which can promote the uniform precipitation of lithium, thereby effectively inhibiting the growth of lithium dendrites. In addition, the assembled lithium iron phosphate battery was measured at room temperature and 1C for more than 200 long cycles, with an average coulombic efficiency of more than 99.5% and a capacity retention rate of 91.8%, indicating that the copolymer electrolyte has excellent cycle performance and shows 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: The following steps are involved: 1) mixing a double-bond imidazole-based ionic liquid, vinyl ethylene carbonate, a lithium salt, a crosslinking agent and an initiator to obtain a copolymer precursor solution; 2) placing the copolymer precursor solution on a membrane carrier of a battery and polymerizing it at 60-75° C. to obtain an ionic liquid copolymer electrolyte with high safety; The structure of the double bond imidazolyl ionic liquid is: wherein R is one of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl, and X is one of chlorine, bromine, iodine, bistrifluoromethanesulfonimide and bisfluoromethanesulfonimide; The molar ratio of the double-bond imidazolyl ionic liquid to vinyl ethylene carbonate is 1:1-7; The lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium perchlorate, lithium tetrafluoroborate, and lithium nitrate.

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-bond imidazolyl ionic liquid, R is butyl, and X is bistrifluoromethanesulfonimide; The molar ratio of the double-bond imidazolyl ionic liquid to vinyl ethylene carbonate is 1:(2-4); The lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalatoborate.

3. The method for preparing the in-situ polymerized ionic liquid copolymer electrolyte with high safety according to claim 1, characterized in that: The cross-linking agent includes one or more of polyethylene glycol diacrylate, pentaerythritol triacrylate, propylene glycol di(meth)acrylate, and trimethylolpropane triacrylate; The initiator is azobisisobutyronitrile; The mixing in step 1) is performed 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 concentration of the lithium salt in the mixture of double-bond imidazolyl ionic liquid and vinyl ethylene carbonate is 0.1-4 mol / L; the mass proportion of the cross-linking agent is 5-20% of the total mass of the copolymer precursor solution; the added amount of the initiator is 0.1-2% of the sum of the mass of the double-bond imidazolyl ionic liquid, vinyl ethylene carbonate and the cross-linking agent; The polymerization time in step 2) is 4 to 8 hours.

5. The method for preparing the in-situ polymerized ionic liquid copolymer electrolyte with high safety according to claim 4, characterized in that: The concentration of the lithium salt in the mixture of double-bond imidazole ionic liquid and vinyl ethylene carbonate is 0.5-2 mol / L.

6. The method for preparing the in-situ polymerized ionic liquid copolymer electrolyte with high safety according to claim 1, characterized in that: Specific steps of step 2): Placing the copolymer precursor solution on a membrane carrier of a battery, polymerizing at 60-75° C., and then assembling the battery; or placing the copolymer precursor solution on a membrane carrier of a battery, assembling the battery, and polymerizing at 60-75° C. to obtain an ionic liquid copolymer electrolyte with high safety; Placing the copolymer precursor solution on the membrane carrier of the battery refers to coating or impregnation; After the battery is assembled in step 2), it is allowed to stand at room temperature for 8 to 24 hours.

7. The method for preparing the in-situ polymerized ionic liquid copolymer electrolyte with high safety according to claim 6, characterized in that: When the battery is a lithium ion battery, the specific steps of step 2) are: placing the copolymer precursor solution on a membrane carrier of the battery, assembling the battery, polymerizing at 60-75° C., and standing at room temperature; When the battery is an asymmetric lithium metal battery or a symmetric battery, step 2) specifically includes placing the copolymer precursor solution on a membrane carrier of the battery, polymerizing at 60-75° C., then assembling the battery and standing at room temperature.

8. The method for preparing the in-situ polymerized ionic liquid copolymer electrolyte with high safety according to claim 1, characterized in that: Step 1) is mixing under a protective atmosphere; The membrane carrier in step 2) is one of a polyvinylidene fluoride-hexafluoropropylene porous membrane, a glass fiber membrane, and a polypropylene diaphragm; 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.

9. An ionic liquid copolymer electrolyte with high safety obtained by the preparation method according to any one of claims 1 to 8.

10. The use of the highly safe ionic liquid copolymer electrolyte according to claim 9, characterized in that: The ionic liquid copolymer electrolyte with high safety is used in lithium ion batteries, asymmetric lithium metal batteries or symmetric batteries.

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