In-situ polymerized flame-retardant perfluorinated gel electrolyte, lithium metal battery and preparation method

Abstract

The present application relates to a kind of in-situ polymerized flame-retardant perfluorinated gel electrolyte, lithium metal battery and preparation method, in-situ polymerized flame-retardant perfluorinated gel electrolyte is prepared from fluorinated organic solvent, lithium salt, fluorine-containing polymer precursor and thermal initiator, the fluorine-containing polymer precursor also includes fluorine-containing polymer and crosslinking agent.Compared with prior art, the present application has high electrochemical window and excellent flame-retardant performance, can realize the matching of room temperature with high pressure high nickel positive electrode and the stable cycle of high pressure lithium metal battery;Preparation method is simple and interface performance is optimized, easy to realize large-scale preparation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gel polymer electrolyte, in particular to a kind of in-situ polymerization flame-retardant perfluoro gel electrolyte, lithium metal battery and preparation method. BACKGROUND

[0002] The liquid electrolyte commonly used in commercial lithium battery has safety hazards such as flammability and leakage, and the development of high-safety solid-state electrolyte is imminent. Inorganic solid-state electrolyte has high safety because it does not add any liquid component, but its large interface impedance and complex preparation process limit its large-scale production and application. The all-solid-state polymer electrolyte can greatly improve the interface contact between the electrode and the electrolyte while ensuring safety, but its low room temperature ionic conductivity cannot meet the demand of practical application, and the gel polymer electrolyte can effectively avoid the leakage of electrolyte and has high room temperature ionic conductivity and low interface impedance, and is considered as one of the most possible electrolyte systems to realize practical application.

[0003] Currently, the preparation of gel polymer electrolyte mainly has two routes of non-in-situ and in-situ. The non-in-situ route needs to first prepare a polymer skeleton that can absorb electrolyte, and then add electrolyte to realize gelation. The electrolyte obtained by this route is generally thick (50-200 μm), which is not conducive to the improvement of battery volume energy density. The in-situ preparation route realizes gelation by in-situ polymerization after liquid injection, which not only can obtain ultra-thin electrolyte (20-30 μm), but also can further reduce the interface impedance. More importantly, this route is compatible with the current liquid injection and formation process of industrialization, and thus can be quickly put into large-scale production.

[0004] However, most of the gel electrolytes still face problems such as electrolyte oxidation and decomposition, irreversible lattice oxygen release and structure transformation of the positive electrode when matched with high-voltage and high-energy-density nickel-rich positive electrode (LiNi x Co y Mn z O2,x+y+z=1,x≥0.6). The continuous side reactions between the gel electrolyte and the nickel-rich positive electrode will cause a significant increase in interface impedance and rapid capacity decay, so it cannot be used in practical application. The uneven deposition / detachment and continuous dendrite growth of lithium ions at the lithium metal negative electrode side will also cause serious safety hazards and performance degradation. SUMMARY

[0005] The purpose of the present application is to overcome the above-mentioned defects of the existing gel electrolyte and provide a kind of in-situ polymerization flame-retardant perfluoro gel electrolyte, lithium metal battery and preparation method.

[0006] The purpose of the present application can be realized by the following technical solutions:

[0007] One of the technical solutions of the present application is to provide a flame-retardant perfluorinated gel electrolyte prepared in situ, which is prepared from a fluorinated organic solvent, a lithium salt, a fluorine-containing polymer precursor and a thermal initiator, wherein the fluorine-containing polymer precursor further comprises a fluorine-containing polymer and a crosslinking agent; wherein the fluorinated organic solvent is selected from any one or more of fluoroethylene carbonate, 2,2,2-trifluoroethyl methyl carbonate, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 3,3,3-trifluoropropyl acetate, 2-fluoropropyl acetate, bis-fluoroethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate, and ethyl difluoroacetate; and the fluorine-containing polymer is selected from any one or more of 2,2,2-trifluoroethyl acrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, hexafluorobutyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, hexafluoropolyether triethoxysilane, and hexafluoropolyether trimethoxysilane.

[0008] In some embodiments, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethylsulfonylimide (LiTFSI), lithium tetrafluoroborate, and lithium difluoro(oxalato)borate.

[0009] In some embodiments, the crosslinking agent is selected from any one or more of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, pentaerythritol tetraacrylate, and tetra(ethylene glycol) diacrylate.

[0010] In some embodiments, the thermal initiator is selected from any one or more of azobisisobutyronitrile (AIBN), dimethyl azobisisobutyrate (AIBME), and dibenzoyl peroxide (BPO).

[0011] In some embodiments, the mass percentages of the fluorinated organic solvent, the lithium salt, the fluorine-containing polymer precursor, and the thermal initiator in the flame-retardant perfluorinated gel electrolyte are as follows: the fluorinated organic solvent is 20-85 wt%, the lithium salt is 5-30 wt%, the fluorine-containing polymer precursor is 5-50 wt%, and the thermal initiator is 0.5-2.5 wt%.

[0012] In some embodiments, the molar ratio of the crosslinking agent in the fluorine-containing polymer precursor is 1-10 mol%.

[0013] Another technical solution of the present application is to provide a lithium metal battery, which comprises a positive electrode, a negative electrode, and a flame-retardant perfluorinated gel electrolyte prepared in situ as described in one of the above technical solutions.

[0014] The third technical solution of the present application provides a preparation method of the lithium metal battery as described in the second technical solution, comprising the following steps:

[0015] S1, stirring the thermal initiator, lithium salt and fluorinated organic solvent uniformly in a protective gas atmosphere, then adding a fluoropolymer precursor, stirring and mixing to obtain a precursor solution;

[0016] S2, injecting the precursor solution obtained in the S2 step into the separator between the negative electrode and the positive electrode of the lithium metal battery in a protective gas atmosphere, and standing to allow the precursor solution to fully infiltrate into the lithium metal battery, and finally heating the lithium metal battery to initiate polymerization to form an in-situ polymerized flame-retardant perfluorogel electrolyte, thereby obtaining an in-situ polymerized flame-retardant perfluorogel electrolyte battery.

[0017] In some embodiments, the protective gas atmosphere in the S1 step and the S2 step is argon with an oxygen content and a water content of less than 1 ppm.

[0018] In some embodiments, the temperature for stirring and mixing in the S1 step is room temperature, and the stirring and mixing time is 5-12 h.

[0019] In some embodiments, the positive electrode material of the lithium metal battery in the S2 step is selected from any one of LiFePO4, LiCoO2, LiNi0.8Co0.1Mn0.1O2 (NCM811), LiNi0.6Co0.2Mn0.2O2 (NCM622) and LiNi0.8Co0.1Mn0.1O2 (NCM83). 0.8 0.1 0.1 0.6 0.2 0.2 0.83 0.12 0.05

[0020] In some embodiments, the separator in the S2 step is selected from any one of polyethylene (PE), polypropylene (PP) and cellulose.

[0021] In some embodiments, the standing temperature in the S2 step is room temperature, and the standing time is 0.5-2 h; the heating temperature is 60-80°C, and the heating time is 4-10 h.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] ​​​​​​​​​(1) The application provides a flame-retardant full-fluorinated gel electrolyte polymerized in situ. The electrolyte is composed of fluorinated components, which endows the electrolyte with good oxidation stability and a high electrochemical window (more than 4.5 V), and enables the electrolyte to match with high-voltage high-nickel positive electrodes at room temperature. In addition, the large amount of fluorinated components in the electrolyte promotes the formation of a high-fluorine interface layer, effectively alleviating the continuous side reactions of the electrolyte with high-activity nickel-rich positive electrodes and lithium metal negative electrodes, such as effectively inhibiting the oxidation of the electrolyte on the positive electrode side and the dissolution of transition metal ions and the uncontrollable growth of lithium dendrites on the negative electrode side, and enabling the stable cycling of high-voltage lithium metal batteries at room temperature.

[0024] (2) The preparation process of the in-situ polymerized flame-retardant full-fluorinated gel electrolyte provided by the application is simple and suitable for mass production. The cross-linked network obtained by in-situ polymerization can effectively prevent leakage of the electrolyte, and the full-fluorinated components endow the electrolyte with excellent flame-retardant properties, which can ensure the high safety of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A physical diagram of the gel electrolyte prepared in Example 1.

[0026] Figure 2 A conductivity diagram of the gel electrolyte prepared in Example 1.

[0027] Figure 3 Electrochemical window test results of Example 1 and commercial electrolyte.

[0028] Figure 4 Cycle performance of high-voltage lithium metal batteries assembled with Example 1 and commercial electrolyte.

[0029] Figure 5 Comparison of combustion tests of Example 1 and commercial electrolyte. DETAILED DESCRIPTION

[0030] The application will be described in detail below in conjunction with the drawings and specific examples. The present embodiment is implemented on the premise of the technical solution of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following examples.

[0031] In the following examples and comparative examples, if no special instructions are given for raw materials or processing techniques, it is indicated that they are all conventional commercially available raw material products or conventional processing techniques in the art.

[0032] 1. The commercial electrolyte is 1M LiPF6 dissolved in a volume ratio of 3:7 of ethylene carbonate / dimethyl carbonate (EC / DMC) organic solvent.

[0033] 2. Conductivity test: The CHI660E electrochemical workstation of Shanghai Chenhua Instrument Co., Ltd. was used to perform the alternating current impedance test, and the test conditions were as follows: the test voltage was 0 V, the test frequency range was 0.1 Hz-1 MHz, and the test amplitude was 5 mV; the ionic conductivity was calculated according to formula (1-1):

[0034]

[0035] wherein, δ is the ionic conductivity, L is the thickness of the electrolyte, R is the resistance obtained by testing, and S is the area of the working electrode.

[0036] 3. Electrochemical window test: The CHI660E electrochemical workstation of Shanghai Chenhua Instrument Co., Ltd. was used to perform the linear sweep voltammetry (LSV) test, and the test conditions were as follows: the voltage range was 0-6 V, and the scan rate was 0.1 mV / s.

[0037] 4. Electrochemical cycle test: The LAND battery test system of Wuhan Land Electronics Co., Ltd. was used to perform the charge-discharge cycle test on the battery, and the test conditions were as follows: the test temperature was 25℃, the charge-discharge voltage range was 3-4.3 V, and the cycle was performed at 0.5C.

[0038] 5. The batteries involved were assembled in an argon-filled glove box, wherein the oxygen and water content were less than 1 ppm.

[0039] Example 1:

[0040] (1) Preparation of NCM811 positive electrode sheet:

[0041] Polyvinylidene fluoride (PVDF) was dissolved in N-methyl pyrrolidone to obtain a PVDF binder solution with a mass fraction of 5wt%; NCM811, conductive carbon black and PVDF binder were uniformly ground in a mortar at a mass ratio of 8:1:1 to obtain a honey-like positive electrode slurry; the positive electrode slurry was uniformly coated on an aluminum foil with a doctor blade, and was placed in a vacuum drying oven at 110℃ for 24h; after drying, it was cut into a circular sheet with a diameter of 12mm, thereby obtaining the NCM811 positive electrode sheet.

[0042] (2) Preparation of precursor solution:

[0043] In an argon-filled glove box (oxygen and water content less than 1 ppm), 0.01 g of thermal initiator (AIBN) and 0.3 g of lithium salt (LiTFSI) were dissolved in 0.783 g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate), and 0.417 g of fluorine-containing polymer precursor (a mixture of 2,2,2-trifluoroethyl methacrylate and polyethylene glycol diacrylate, wherein the content of polyethylene glycol diacrylate is 5.8 mol% of the content of the fluorine-containing polymer precursor) was added after stirring uniformly. The precursor solution was obtained after stirring at room temperature for 12 h.

[0044] (3) Preparation of the perfluorinated gel electrolyte:

[0045] In an argon-filled glove box (oxygen and water content less than 1 ppm), 200 μL of the precursor solution was injected into the separator (PP separator) between the positive electrode (NCM811 positive electrode sheet) and the negative electrode (lithium metal) of the lithium metal battery, and a coin cell was assembled. After standing at room temperature for 2 h, the assembled battery was placed in a constant temperature oven and heated at 70 °C for 8 h to obtain a completely cured in-situ polymerized flame-retardant perfluorinated gel electrolyte and an in-situ polymerized flame-retardant perfluorinated gel electrolyte battery.

[0046] The flame-retardant perfluorinated gel electrolyte prepared in Example 1 was observed and tested as follows:

[0047] (1) Figure 1 The flame-retardant perfluorinated gel electrolyte obtained after curing of the precursor solution in step (2) was transparent, and the liquid component was well wrapped in the polymer matrix, with no obvious flowability.

[0048] (2) The room temperature ionic conductivity was calculated from the impedance of the flame-retardant perfluorinated gel electrolyte, and the room temperature impedance of the flame-retardant perfluorinated gel electrolyte was Figure 2 Therefore, the impedance of the flame-retardant perfluorinated gel electrolyte was 9.05 Ω, and the thickness of the flame-retardant perfluorinated gel electrolyte was equivalent to the thickness of the PP diaphragm (25 μm). According to formula (1-1), the room temperature ionic conductivity of the flame-retardant perfluorinated gel electrolyte was calculated to be 1.45 × 10 -4 S cm -1 , which is more than 10 -4 S cm -1 , indicating that it meets the conditions for cycling at room temperature.

[0049] (3) The electrochemical window test results of the flame-retardant perfluorinated gel electrolyte prepared in Example 1 and the commercial electrolyte are shown in Figure 3 Therefore, the electrochemical window of the flame-retardant perfluorinated gel electrolyte reached 5.21 V, with good oxidation resistance stability, and could be matched with high-voltage positive electrodes, while the commercial electrolyte began to decompose at 4.49 V.

[0050] (4) The charge-discharge cycle test of the battery with the flame-retardant perfluoro-gel electrolyte prepared in this embodiment 1 and the commercial electrolyte is shown in Table 2. Figure 4 The capacity retention rate of the high-voltage lithium metal battery assembled with the flame-retardant perfluoro-gel electrolyte is as high as 97.7% after 200 cycles at 0.5C, and there is almost no capacity decay, while the capacity of the battery assembled with the commercial electrolyte decays rapidly, and the capacity retention rate is only 84.5% after 200 cycles.

[0051] (5) The flame-retardant performance of the flame-retardant perfluoro-gel electrolyte prepared in this embodiment 1 is verified by using a flame gun ignition test as a control with the commercial electrolyte, and the test results are shown in Table 3. Figure 5 The commercial electrolyte is quickly burned out after the flame gun is ignited for 0.5s, while the flame-retardant perfluoro-gel electrolyte is quickly self-extinguished after the flame gun is ignited for 10s, showing excellent flame-retardant performance.

[0052] Embodiment 2:

[0053] Most of them are the same as in embodiment 1, the difference is that in step (2), 0.783g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate) is changed to 0.654g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate); 0.417g of polymer precursor is changed to 0.546g.

[0054] Embodiment 3:

[0055] Most of them are the same as in embodiment 1, the difference is that in step (2), 0.783g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate) is changed to 0.712g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate); 0.417g of polymer precursor is changed to 0.488g.

[0056] Embodiment 4:

[0057] Most of them are the same as in embodiment 1, the difference is that in step (2), 0.783g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate) is changed to 0.805g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate); 0.417g of polymer precursor is changed to 0.395g.

[0058] Embodiment 5:

[0059] Most of them are the same as in embodiment 1, the difference is that in step (2), 0.783g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate) is changed to 0.889g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate); 0.417g of polymer precursor is changed to 0.311g.

[0060] Example 6:

[0061] Most of them are the same as Example 1, the difference is that in step (2), 0.783g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate) is changed to the same mass of a mixture of 3,3,3-trifluoropropyl acetate and fluoroethylene carbonate, and the content of fluoroethylene carbonate is 5wt% of the total content of the precursor solution.

[0062] Example 7:

[0063] Most of them are the same as Example 1, the difference is that in step (2), 0.783g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate) is changed to the same mass of a mixture of 3,3,3-trifluoropropyl acetate and fluoroethylene carbonate, and the content of fluoroethylene carbonate is 5wt% of the total content of the precursor solution.

[0064] Example 8:

[0065] Most of them are the same as Example 1, the difference is that in step (2), 0.783g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate) is changed to the same mass of a mixture of 3,3,3-trifluoropropyl acetate and fluoroethylene carbonate, and the content of fluoroethylene carbonate is 10wt% of the total content of the precursor solution.

[0066] Example 9:

[0067] Most of them are the same as Example 1, the difference is that in step (2), 0.783g of fluorinated organic solvent (3,3,3-trifluoropropyl acetate) is changed to the same mass of a mixture of 3,3,3-trifluoropropyl acetate and fluoroethylene carbonate, and the content of fluoroethylene carbonate is 20wt% of the total content of the precursor solution.

[0068] According to the test method of Example 1, the in-situ polymerization of the full fluorinated gel electrolyte of Examples 1 to 9 is tested respectively, and the test results are shown in Table 1 below:

[0069] Table 1 Performance statistics of flame-retardant full fluorinated gel electrolyte

[0070]

[0071] As can be seen from the above table, by adjusting the types and contents of fluorinated organic solvents and polymer precursors, gels can be formed after heating at 70°C for 8h.

[0072] Comparative Examples 1-6, the results show that with the increase of the content of fluorinated organic solvent 3,3,3-trifluoropropyl acetate and the decrease of the content of fluorinated polymer precursor, the room temperature ionic conductivity of the flame-retardant full fluorinated gel polymer electrolyte gradually increases, and the electrochemical window gradually decreases.

[0073] Compared with Comparative Examples 1, 7-9, it can be seen that the addition of fluoroethylene carbonate in the fluorinated organic solvent can significantly improve the room temperature ionic conductivity of the flame-retardant perfluorinated gel electrolyte, but as the content of fluoroethylene carbonate increases, the electrochemical window decreases slightly.

[0074] The voltage window of the flame-retardant perfluorinated gel polymer electrolyte prepared in Examples 1-9 is higher than that of the commercial electrolyte, and all of them show good cycle stability when matched with the high-nickel ternary positive electrode. The capacity retention rate of the lithium metal battery assembled by the commercial electrolyte is only 84.5% after 200 cycles at 0.5C, which is due to the continuous oxidative decomposition of EC on the positive electrode surface, generating a large amount of by-products, resulting in the continuous increase of interfacial impedance, and thus it is difficult to achieve stable cycling. The capacity retention rate of the battery assembled by the flame-retardant perfluorinated gel electrolyte is all above 96%, which shows that the flame-retardant perfluorinated gel electrolyte can form a stable interfacial layer on the surface of the NCM811 positive electrode, preventing the continuous side reaction between the electrolyte and the positive electrode.

[0075] The flame-retardant perfluorinated gel electrolytes prepared in Examples 1-9 all have good flame-retardant effect, and can self-extinguish after 10s of spray gun ignition, which shows that the flame-retardant perfluorinated gel electrolyte has superior safety.

[0076] Comparative Example 1:

[0077] Most of them are the same as Example 1, except that the fluorinated organic solvent is replaced by the same mass percentage of conventional organic solvent, which is ethyl propionate.

[0078] Comparative Example 2:

[0079] Most of them are the same as Example 1, except that the fluorinated polymer precursor is replaced by the same mass percentage of conventional polymer precursor, which is ethyl methacrylate.

[0080] According to the test method of Reference Example 1, the in-situ polymerization gel electrolyte prepared from Comparative Example 1 and Comparative Example 2 is tested, and the test results are shown in Table 2 below:

[0081] Table 2 Performance statistics of gel electrolyte

[0082]

[0083] Comparing Comparative Example 1 and Comparative Example 1, it can be seen that whether the organic solvent contains fluorine has little effect on the ionic conductivity, but after replacing the fluorinated organic solvent with a conventional organic solvent, the electrochemical window of the electrolyte is significantly reduced, and it cannot be self-extinguished after 10s of spray gun ignition, and the capacity attenuation of the battery during the cycle process is intensified.

[0084] Comparative Example 1 and Comparative Example 2, it can be seen that whether the polymer precursor contains fluorine has little effect on the ionic conductivity, but after the fluorine-containing polymer precursor is replaced by a conventional polymer precursor, the electrochemical window of the electrolyte is significantly reduced, and the capacity attenuation of the battery during the cycle process is intensified.

[0085] The results of the comparative examples show that the introduction of fluorine atoms in the electrolyte system can significantly improve the electrochemical window, and the highest electrochemical window can be obtained when the fluorinated organic solvent and the fluorine-containing polymer precursor are used together, and the fluorinated organic solvent is the key to determine the flame retardant performance of the electrolyte. In addition, both the fluorinated organic solvent and the fluorine-containing polymer precursor play an important role in the construction of the weakly solvated structure electrolyte, and the weakly solvated structure can dominate the formation of the stable interfacial layer. The fluorine in the organic solvent and the polymer precursor can also directly participate in the formation of LiF in the interfacial layer. Therefore, the use of fluorinated organic solvent and fluorine-containing polymer precursor together can obtain the most stable cycle performance.

[0086] The above description of the examples is for the purpose of enabling and using the invention for those of ordinary skill in the art. Those skilled in the art can easily make various modifications to these examples, and apply the general principles described herein to other examples without creative labor. Therefore, the present application is not limited to the above examples, and the improvements and modifications made by those skilled in the art according to the disclosure of the present application without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. An in-situ polymerized, flame-retardant perfluorogelled electrolyte, characterized in that, Prepared from a fluorinated organic solvent, a lithium salt, a fluorine-containing polymer precursor, and a thermal initiator, the fluorine-containing polymer precursor further comprising a fluorine-containing polymer and a crosslinking agent; wherein the fluorinated organic solvent is selected from any one or more of fluorinated ethylene carbonate, 2,2,2-trifluoroethyl methyl carbonate, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 3,3,3-trifluoropropyl ethyl carbonate, 2-fluoropropyl ethyl carbonate, bis-fluorinated ethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate, ethyl difluoroacetate; the fluorine-containing polymer is selected from any one or more of 2,2,2-trifluoroethyl acrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, hexafluorobutyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate.

2. An in-situ polymerized flame-retardant perfluorinated gel electrolyte according to claim 1, wherein, The lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium difluoro(oxalato)borate.

3. An in-situ polymerized flame-retardant perfluorinated gel electrolyte according to claim 1, wherein, The crosslinking agent is selected from any one or more of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, pentaerythritol tetraacrylate, tetra(ethylene glycol) diacrylate.

4. An in-situ polymerized flame-retardant perfluorinated gel electrolyte according to claim 1, wherein, The thermal initiator is selected from any one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate, dibenzoyl peroxide.

5. An in-situ polymerized flame-retardant perfluorinated gel electrolyte according to claim 1, wherein, The fluorinated organic solvent, the lithium salt, the fluorine-containing polymer precursor, and the thermal initiator have mass percentages in the flame-retardant perfluorogel electrolyte of 20-85 wt% for the fluorinated organic solvent, 5-30 wt% for the lithium salt, 5-50 wt% for the fluorine-containing polymer precursor, and 0.5-2.5 wt% for the thermal initiator.

6. An in-situ polymerized, flame-retardant, perfluorinated gel electrolyte according to claim 1, wherein, The crosslinking agent has a molar ratio of 1-10 mol% in the fluorine-containing polymer precursor.

7. A lithium metal battery, characterized in that, A lithium metal battery comprising a positive electrode, a negative electrode, and an in-situ polymerized flame-retardant perfluorogel electrolyte as claimed in any one of claims 1-6 between the positive electrode and the negative electrode.

8. A method of producing a lithium metal battery as claimed in claim 7, characterized in that, The method comprises the following steps: S1. In a protective gas atmosphere, stirring the thermal initiator, the lithium salt, and the fluorinated organic solvent until uniform, then adding the fluorine-containing polymer precursor, stirring and mixing to obtain a precursor solution; S2. In a protective gas atmosphere, injecting the precursor solution obtained in step S2 between the negative electrode and the positive electrode of a lithium metal battery, and allowing the precursor solution to fully infiltrate into the lithium metal battery by standing, and finally heating the lithium metal battery to initiate polymerization to form an in-situ polymerized flame-retardant perfluorogel electrolyte, thereby obtaining an in-situ polymerized flame-retardant perfluorogel electrolyte battery.

9. The preparation method according to claim 8, characterized in that, In step S1, the temperature for stirring and mixing is room temperature, and the time for stirring and mixing is 5-12 h. In step S2, the temperature for standing is room temperature, the time for standing is 0.5-2 h, the temperature for heating is 60-80℃, and the time for heating is 4-10 h. In steps S1 and S2, the protective gas atmosphere is argon with oxygen and water contents both less than 1 ppm.

10. The preparation method according to claim 8, characterized in that, At S2, the positive material of the lithium metal battery is selected from any one of LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2 and LiNi 0.83 Co 0.12 Mn 0.05 O2; the separator is selected from any one of polyethylene, polypropylene, cellulose.

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