High-voltage-resistant fluorine-boron polymer solid electrolyte as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a high-voltage-resistant fluorine-boron polymer solid electrolyte as well as a preparation method and application thereof. According to the high-voltage-resistant fluorine-boron polymer solid electrolyte provided by the invention, the high-voltage-resistant fluorine-boron polymer solid electrolyte is designed and synthesized from the perspective of molecular design, so that the oxidation-resistant stability of an electrolyte matrix is effectively improved, the electrolyte can adapt to a high-voltage positive electrode material, and the stability of the electrolyte at a high working potential is improved. Meanwhile, a polymer-lithium salt coordinated regulation strategy is constructed by utilizing the lewis acid characteristic of sp2 hybrid B atoms in the high-voltage-resistant fluorine-boron polymer solid electrolyte, and aims to optimize an electrode-electrolyte interface and form a uniform and stable electrode-electrolyte interface, so that excellent interface stability and efficient ion transmission performance are realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a high-voltage-resistant fluoroboron polymer solid-state electrolyte and a preparation method and application thereof. BACKGROUND

[0002] With the development of portable electronic devices, electric vehicles and energy storage systems, there is an increasing demand for lithium ion batteries with high energy density, long cycle life and excellent safety. Metal lithium is considered as an ideal negative electrode material for the next generation of high-energy-density energy storage devices due to its ultra-high theoretical specific capacity and low redox potential. However, the core challenge of realizing high-energy-density lithium metal batteries lies in selecting a suitable high-voltage positive electrode material. Currently, nickel-cobalt-manganese ternary materials (such as LiNi x Co y Mn z O2, x+y+z=1, NCM) are widely concerned due to their high specific capacity (>200mAh·g -1 ) and working voltage (>4.2V). The high nickel content of NCM not only significantly improves the energy density, but also reduces the use amount of cobalt and the material cost. However, the oxidation decomposition of the electrolyte and the dissolution of the transition metals (Ni, Co, Mn) of the positive electrode material under high voltage conditions lead to an increase in interfacial impedance and rapid capacity decay, which seriously restricts the long cycle performance of the battery. Therefore, developing an electrolyte system and an interface stabilization strategy that can adapt to high voltage conditions is the key to improving the performance of lithium metal batteries. SUMMARY

[0003] The purpose of the present application is to provide a high-voltage-resistant fluoroboron polymer solid-state electrolyte and a preparation method and application thereof.

[0004] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions: The present application provides a high-voltage-resistant fluoroboron polymer solid-state electrolyte, comprising a fluoroboron cross-linked polymer and a lithium salt and a plasticizer filled in the fluoroboron cross-linked polymer; The structural formula of the fluoroboron cross-linked polymer is as follows: ; The R comprises at least one of 、 and ; wherein m=2~10, n=1~5, p=1~100, q=1~100, q=1~50; The R1 is at least one of 、 、 、 and ; wherein a=1~20000, b=1~10000.

[0005] Preferably, the lithium salt comprises at least one of lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate and lithium difluoro(oxalato)borate.

[0006] Preferably, the plasticizer comprises at least one of ethylene carbonate, dimethyl carbonate, propylene carbonate, sulfolane, fluoroethylene carbonate and dimethyl ether of ethylene glycol.

[0007] Preferably, the mass percentage of lithium salt in the high-pressure resistant fluoroboron polymer solid-state electrolyte is 15-25%.

[0008] Preferably, the mass percentage of plasticizer in the high-pressure resistant fluoroboron polymer solid-state electrolyte is 30-50%.

[0009] The application also provides a preparation method of the high-pressure resistant fluoroboron polymer solid-state electrolyte described above, comprising the following steps: Mixing fluoroboron monomers, allyl monomers, lithium salt and plasticizer to obtain a homogeneous solution; Mixing the homogeneous solution and a thermal initiator, and performing thermal polymerization reaction on the obtained precursor solution to obtain the high-pressure resistant fluoroboron polymer solid-state electrolyte; The structure of the fluoroboron monomer is as follows: ; The R comprises at least one of 、 and ; wherein m=2-10, n=1-5, p=1-100, q=1-100, q=1-50; The allyl monomer comprises at least one of ethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, isopentyldipentaerythritol tetraacrylate and N.N-methylenebisacrylamide.

[0010] Preferably, the mass ratio of the fluoroboron monomer and the allyl monomer is 15-25:15-25.

[0011] Preferably, the thermal initiator comprises at least one of azobisisobutyronitrile, azobisisoheptyl nitrile, dimethyl azobisisobutyrate and benzoyl peroxide. The mass of the thermal initiator is 0.5-2% of the total mass of the fluoroboron monomer, the allyl monomer and the lithium salt.

[0012] Preferably, the temperature of the thermal polymerization reaction is 60-90°C, and the time is 8-15h.

[0013] The application also provides application of the high-pressure-resistant fluorine-boron polymer solid electrolyte in a lithium ion battery.

[0014] The high-pressure-resistant fluorine-boron polymer solid electrolyte provided by the application is designed and synthesized from the perspective of molecular design, effectively improves the oxidation stability of the electrolyte matrix itself, enables the electrolyte to adapt to high-voltage positive electrode materials, and improves the stability of the electrolyte at a high working potential. Meanwhile, the Lewis acid property of the sp 2 Hybrid B atom in the high-pressure-resistant fluorine-boron polymer solid electrolyte is used to construct a synergistic regulation strategy of polymer-lithium salt, which aims to optimize the electrode-electrolyte interface and form a uniform and stable electrode-electrolyte interface, so as to realize excellent interface stability and efficient ion transport performance. The results of the examples show that the lithium ion battery assembled by the high-pressure-resistant fluorine-boron polymer solid electrolyte provided by the application has a room temperature ionic conductivity of 0.39 mS·cm -1 , and a lithium ion transference number of 0.92, and can be stably cycled at 2.8-4.3 V.

[0015] The application also provides a preparation method of the high-pressure-resistant fluorine-boron polymer solid electrolyte. The method provided by the application has low cost, simple process and easy-to-control conditions. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a surface SEM diagram of the high-pressure-resistant fluorine-boron polymer solid electrolyte film of Example 1. Figure 2 It is a section SEM diagram of the NCM811 / Li battery obtained in Application Example 1. Figure 3 It is an infrared test diagram of the high-pressure-resistant fluorine-boron polymer solid electrolyte film of Example 1. Figure 4 It is a lithium ion transference number diagram of the lithium-lithium symmetric battery prepared by the precursor solution obtained in Example 1. Figure 5 It is a linear sweep voltammetry curve diagram of the lithium-steel battery prepared by the precursor solution obtained in Example 1. Figure 6 It is a cycle diagram of the lithium-lithium symmetric battery prepared by the precursor solution obtained in Example 1. Figure 7 It is a room temperature rate cycle test diagram of the NCM811 / Li button cell prepared by the precursor solution obtained in Example 1. DETAILED DESCRIPTION

[0017] The application provides a high-pressure-resistant fluorine-boron polymer solid electrolyte, comprising a fluorine-boron cross-linked polymer and a lithium salt and a plasticizer filled in the fluorine-boron cross-linked polymer. The structural formula of the fluorine-boron cross-linked polymer is as follows: ; The R comprises at least one of , and ; wherein m=2-10, n=1-5, p=1-100, q=1-100, q=1-50; The R1 is at least one of , , , and ; wherein a=1-20000, b=1-10000.

[0018] In the application, the lithium salt preferably comprises at least one of lithium bis(oxalato)borate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate and lithium difluoro(oxalato)borate. In the application, the mass percentage content of the lithium salt in the high-pressure-resistant fluorine-boron polymer solid electrolyte is preferably 15-25%, and specifically can be 15%, 18%, 20%, 22% or 25%.

[0019] In the application, the plasticizer preferably comprises at least one of ethylene carbonate, dimethyl carbonate, propylene carbonate, sulfolane, fluoroethylene carbonate and ethylene glycol dimethyl ether. In the application, the mass percentage content of the plasticizer in the high-pressure-resistant fluorine-boron polymer solid electrolyte is preferably 30-50%, and specifically can be 30%, 35%, 40%, 45% or 50%.

[0020] The application further provides a preparation method of the high-pressure-resistant fluorine-boron polymer solid electrolyte. The fluorine-boron monomer, the allyl monomer, the lithium salt and the plasticizer are mixed to obtain a homogeneous solution; The homogeneous solution and a thermal initiator are mixed, a precursor solution obtained is subjected to a thermal polymerization reaction, and the high-pressure-resistant fluorine-boron polymer solid electrolyte is obtained.

[0021] The fluorine-boron monomer, the allyl monomer, the lithium salt and the plasticizer are mixed to obtain a homogeneous solution.

[0022] In the application, the structural formula of the fluorine-boron monomer is as follows: ; The R comprises at least one of , and at least one of ethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, isopentyldiethyleneglycol tetraacrylate, and N.N-methylene bisacrylamide; wherein m = 2-10, n = 1-5, p = 1-100, q = 1-100, and r = 1-50.

[0023] In the present application, the allyl monomer includes at least one of ethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, isopentyldiethyleneglycol tetraacrylate, and N.N-methylene bisacrylamide.

[0024] In the present application, the average molecular weight of the polyethylene glycol diacrylate is preferably 200-20000, and can be specifically 200, 400, 600, 1000, 2000, 4000, 6000, 10000, or 20000. In the present application, the average molecular weight of the polyethylene glycol dimethacrylate is preferably 550-10000, and can be specifically 550, 750, 1000, 2000, 4000, or 10000.

[0025] In the present application, the mass ratio of the fluoroboron monomer and the allyl monomer is preferably 15-25:15-25.

[0026] In the present application, the mixing is preferably performed under stirring, and the temperature of the stirring is preferably 25-30℃, and the time is preferably 12h.

[0027] After obtaining the homogeneous solution, the present application mixes the homogeneous solution and a thermal initiator, and performs a thermal polymerization reaction on the obtained precursor solution to obtain the high-pressure-resistant fluoroboron polymer solid-state electrolyte.

[0028] In the present application, the thermal initiator preferably includes at least one of azobisisobutyronitrile, azobisisoheptyl nitrile, dimethyl azobisisobutyrate, and benzoyl peroxide; and the mass of the thermal initiator is preferably 0.5-2% of the total mass of the fluoroboron monomer, the allyl monomer, and the lithium salt, and can be specifically 0.5%, 1.0%, 1.5%, or 2.0%.

[0029] In the present application, the mixing is preferably performed under stirring, and the temperature of the stirring is preferably 25-30℃, and the time is preferably 1h.

[0030] In the present application, the temperature of the thermal polymerization reaction is preferably 60-90℃, and can be specifically 60℃, 70℃, 80℃, or 90℃; and the time is preferably 8-15h, and can be specifically 8h, 9h, 10h, 11h, 12h, 13h, 14h, or 15h.

[0031] In the present application, the thermal polymerization reaction is preferably: after the obtained precursor solution is directly coated on the surface of a substrate, the thermal polymerization reaction is carried out to directly obtain a solid electrolyte film; or after the obtained precursor solution is directly assembled into a required battery, the thermal polymerization reaction is carried out to form a solid electrolyte film in the battery.

[0032] In the present application, the high-pressure-resistant fluoroboron polymer solid electrolyte is preferably used in the form of a thin film, and the thickness of the thin film is preferably 15-25 microns.

[0033] The present application also provides the use of the high-pressure-resistant fluoroboron polymer solid electrolyte described in the above technical solution or the high-pressure-resistant fluoroboron polymer solid electrolyte prepared by the preparation method described in the above technical solution in a lithium ion battery.

[0034] In the present application, the lithium ion battery preferably comprises a positive electrode, a negative electrode and an electrolyte between the positive electrode and the negative electrode. In the present application, the positive electrode preferably comprises a current collector and a positive electrode coating layer on the surface of the current collector, and the positive electrode coating layer preferably comprises a positive electrode active material, a conductive agent and a binder; the positive electrode active material preferably comprises one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium nickel cobalt oxide, lithium nickel cobalt manganese oxide and lithium iron manganese phosphate, and specifically LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811); the current collector is preferably an aluminum foil; the conductive agent preferably comprises one or more of acetylene black, ketjen black and carbon nanotubes; the binder preferably comprises one or more of polytetrafluoroethylene, polyurethane and polyvinylidene fluoride; and the mass ratio of the positive electrode active material, the conductive agent and the binder is 6-8:1-2:1-2, and specifically 8:1:1. In the present application, the negative electrode is preferably a lithium metal sheet.

[0035] The lithium ion battery provided by the present application can be stably cycled at 2.8-4.3 V with the high-pressure-resistant fluoroboron polymer solid electrolyte as the electrolyte, and has excellent rate performance at room temperature.

[0036] Unless otherwise specified, the materials and equipment used in the present application are commercially available in the art.

[0037] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0038] Example 1 In this embodiment, the structural formula of the fluorine-boron monomer used is as follows:

[0039] The reaction formula for the thermal polymerization of fluoroboron monomer and ethylene glycol diacrylate is as follows:

[0040] Inside a glove box, 0.5 g of ethylene glycol diacrylate, 0.5 g of fluoroboron monomer, 0.58 g of LiTFSI and 0.06 g of LiBOB were placed in a 5 mL transparent vial, and then 0.5 mL of EC and 0.5 mL of DMC were added as solvents. The vial was placed in a magnetic stir bar and stirred at room temperature for 12 hours to obtain a homogeneous solution. 1 wt% azobisisobutyronitrile (AIBN, calculated based on total mass) was added to the homogeneous solution as a thermal initiator, and stirring was continued for 1 hour to obtain a stable precursor solution. The obtained precursor solution was coated onto the substrate surface and transferred to a 70°C vacuum oven for curing for 12 hours to complete the thermal polymerization reaction, resulting in a high-pressure resistant fluoroboron polymer solid electrolyte membrane with a thickness of 20 micrometers.

[0041] Example 2 A high-voltage resistant fluoroboron polymer solid electrolyte membrane was prepared according to Example 1, wherein ethylene glycol diacrylate was replaced with ethylene glycol dimethacrylate.

[0042] Example 3 A high-voltage resistant fluoroboron polymer solid electrolyte membrane was prepared according to Example 1, wherein ethylene glycol diacrylate was replaced with ethoxylated trimethylolpropane triacrylate.

[0043] Example 4 A high-voltage resistant fluoroboron polymer solid electrolyte membrane was prepared according to Example 1, wherein ethylene glycol diacrylate was replaced with isoprene tetraacrylate.

[0044] Example 5 A high-voltage resistant fluoroboron polymer solid electrolyte membrane was prepared according to Example 1, wherein ethylene glycol diacrylate was replaced with NN-methylenebisacrylamide.

[0045] Comparative Example 1 A high-voltage resistant fluoroboron polymer solid electrolyte membrane was prepared according to Example 1, wherein 1g of fluoroboron monomer and 1g of ethylene glycol diacrylate were used.

[0046] Comparative Example 2 A high-voltage resistant fluoroboron polymer solid electrolyte membrane was prepared according to Example 1, wherein 2g of fluoroboron monomer and 2g of ethylene glycol diacrylate were used.

[0047] The ionic conductivity of the solid electrolyte membranes obtained in the examples and comparative examples was tested, and the test results are shown in Table 1. Table 1. Room temperature ionic conductivity of electrolytes prepared at different ratios

[0048] As shown in Table 1, the highest lithium-ion conductivity can be achieved using a high-voltage resistant fluoroboron polymer solid electrolyte membrane formed with 0.5 g of ethylene glycol diacrylate and 0.5 g of fluoroboron monomer. The ionic conductivity decreases with increasing amounts of ethylene glycol diacrylate and fluoroboron monomer.

[0049] Application Examples 1-5 The precursor solutions obtained in Examples 1-5 were directly assembled with positive and negative electrodes into coin cells. The cells were then cured in a vacuum oven at 70°C for 12 hours to complete the thermal polymerization reaction. The positive electrode consists of a current collector (aluminum foil) and a positive electrode coating covering the surface of the current collector. The positive electrode active material in the positive electrode coating is LiNi. 0.8 Co 0.1 Mn 0.1 O2 (NCM811), the conductive agent is acetylene black, and the binder is polyvinylidene fluoride; the mass ratio of the positive electrode active material, conductive agent and binder is 8:1:1; the negative electrode is a lithium metal sheet.

[0050] Performance testing Test Example 1 (1) The surface of the high-voltage resistant fluoroboron polymer solid electrolyte membrane of Example 1 was tested by scanning electron microscopy, and the obtained SEM image is shown below. Figure 1 As shown; by Figure 1 As can be seen, the surface of the high-pressure resistant fluoroboron polymer solid electrolyte membrane prepared by the present invention exhibits a uniformly wrinkled polymer membrane structure without any pores, indicating that it has good structural stability.

[0051] (2) Figure 2 This is a cross-sectional SEM image of the NCM811 / Li battery obtained in Application Example 1; from Figure 2 As can be seen, the high-voltage resistant fluoroboron polymer solid electrolyte membrane prepared in this application example has a thickness of 18.3µm, and the electrolyte membrane is in close contact with the electrode, indicating that the precursor has achieved a complete thermal polymerization reaction, thereby ensuring the interfacial stability between the electrolyte and the electrode.

[0052] (3) The high-voltage resistant fluoroboron polymer solid electrolyte membrane obtained in Example 1 was subjected to infrared testing, and the results are as follows: Figure 3 As shown; by Figure 3 As can be seen, the high-pressure resistant fluoroboron polymer solid electrolyte prepared in this invention, after thermal polymerization, is located at 1638 cm⁻¹. -1The C=C double bond characteristic peak at the point completely disappeared, indicating that the fluoroboron monomer and the propylene monomer had successfully undergone polymerization reaction inside the electrolyte to form a stable cross-linked network structure.

[0053] Test Example 2 (1) The precursor solution obtained in Example 1 was directly assembled into a lithium-lithium symmetric battery. The lithium-ion transference number of the obtained lithium-lithium symmetric battery was tested, and the test results are shown in the figure below. Figure 4 As shown; the inset shows the lithium-ion transference number calculated from the chronoamperometry curve and AC impedance spectroscopy; by Figure 4 It can be seen that the lithium-ion transference number of the obtained lithium-lithium symmetric battery can reach 0.92.

[0054] (2) The precursor solution obtained in Example 1 was directly assembled into a lithium steel battery (i.e. a battery assembled from lithium sheets and steel sheets). Figure 5 The curve of the linear sweep voltammetry for the obtained lithium steel battery is shown.

[0055] Depend on Figure 5 It can be seen that the high-voltage resistant fluoroboron polymer solid electrolyte prepared in Example 1 exhibits an electrochemical window as high as 5.34V. This result shows that the high-voltage resistant fluoroboron polymer solid electrolyte can remain stable under high voltage conditions, has excellent oxidation resistance and interfacial stability, and has good compatibility with high-voltage cathode materials.

[0056] (3) Figure 6 Cyclic diagram of a lithium-lithium symmetric battery prepared using the precursor solution obtained in Example 1.

[0057] from Figure 6 As can be seen from this, the obtained lithium-lithium symmetric battery has a current of 0.1 mA·cm⁻¹. -2 It exhibits an initial polarization voltage of approximately 100 mV at current density and can cycle stably for over 1600 hours without showing a significant increase in polarization voltage, demonstrating excellent interface stability.

[0058] (4) Figure 7 The room temperature rate cycling test results for the NCM811 / Li coin cells prepared using the precursor solution obtained in Example 1 were obtained by testing at room temperature (25°C) and 2.8–4.3 V.

[0059] from Figure 7 It can be seen that at room temperature (25℃), the values ​​at 0.1C, 0.2C, 0.5C, and 1C are 193.8, 170.4, 145.0, and 128.8 mAh·g, respectively. -1 When the battery rate returns to 0.1C, the battery's discharge specific capacity can recover to 172.1 mAh·g. -1This phenomenon indicates that the high-voltage resistant fluoroboron polymer solid electrolyte still exhibits good ion conductivity and interfacial stability under high current density conditions, demonstrating excellent rate performance.

[0060] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A high-pressure resistant fluoroboron polymer solid-state electrolyte, characterized by, The fluorine-boron cross-linked polymer and a lithium salt and a plasticizer filled in the fluorine-boron cross-linked polymer; The structural formula of the fluorine-boron cross-linked polymer is as follows: ； The R includes , and at least one; wherein m = 2 ~ 10, n = 1 ~ 5, p = 1 ~ 100, q = 1 ~ 100, q = 1 ~ 50; The R1 is at least one of , , , and ; wherein a = 1 ~ 20000, b = 1 ~ 10000.

2. The high-pressure resistant fluoroboron polymer solid-state electrolyte according to claim 1, characterized in that, The lithium salt includes at least one of lithium bis(oxalato)borate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate and lithium difluoro(oxalato)borate.

3. The high-pressure resistant fluoroboron polymer solid-state electrolyte of claim 1, wherein, The plasticizer includes at least one of ethylene carbonate, dimethyl carbonate, propylene carbonate, sulfolane, fluoroethylene carbonate and dimethyl ether of ethylene glycol.

4. The high-pressure resistant fluoroborate polymer solid-state electrolyte according to claim 1 or 2, characterized in that, The mass percentage of the lithium salt in the high-pressure-resistant fluorine-boron polymer solid-state electrolyte is 15-25%.

5. The high-pressure resistant fluoroboron polymer solid-state electrolyte according to claim 1 or 3, characterized in that, The mass percentage of the plasticizer in the high-pressure-resistant fluorine-boron polymer solid-state electrolyte is 30-50%.

6. The method of producing a high-pressure resistant fluoroboron polymer solid-state electrolyte according to any one of claims 1 to 5, characterized by, The method comprises the following steps: Mixing a fluorine-boron monomer, an allyl monomer, a lithium salt and a plasticizer to obtain a homogeneous solution; Mixing the homogeneous solution and a thermal initiator, and performing a thermal polymerization reaction on the obtained precursor solution to obtain the high-pressure-resistant fluorine-boron polymer solid-state electrolyte; The structural formula of the fluorine-boron monomer is as follows: ； The R includes , and at least one of; wherein m = 2 ~ 10, n = 1 ~ 5, p = 1 ~ 100, q = 1 ~ 100, q = 1 ~ 50; The allyl monomer includes at least one of ethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, isopentyldipentaerythritol tetraacrylate and N.N-methylenebisacrylamide.

7. The production method according to claim 6, characterized by, The mass ratio of the fluorine-boron monomer and the allyl monomer is 15-25:15-25.

8. The preparation method according to claim 6, characterized in that, The thermal initiator includes at least one of azobisisobutyronitrile, azobisisoheptyl nitrile, dimethyl azobisisobutyrate and benzoyl peroxide; The mass of the thermal initiator is 0.5-2% of the total mass of the fluorine-boron monomer, the allyl monomer and the lithium salt.

9. The preparation method according to claim 6, characterized in that, The temperature of the thermal polymerization reaction is 60-90°C, and the time is 8-15h.

10. The high-pressure-resistant fluorine-boron polymer solid-state electrolyte of any one of claims 1-5 or the high-pressure-resistant fluorine-boron polymer solid-state electrolyte prepared by the preparation method of any one of claims 6-9 is applied in a lithium ion battery.

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