MOF-based polymer electrolyte capable of realizing in-situ polymerization, preparation method of MOF-based polymer electrolyte and application of MOF-based polymer electrolyte in solid-state lithium battery

Abstract

The invention discloses an MOF-based polymer electrolyte capable of in-situ polymerization, a preparation method of the MOF-based polymer electrolyte and application of the MOF-based polymer electrolyte in a solid-state lithium battery, and the preparation method comprises the following steps: introducing polymerizable unsaturated bond vinyl and fluorinated groups on an MOFs skeleton to synthesize UiO-66-FV; then, carrying out in-situ copolymerization on the UiO-66-FV and a monomer containing a carbonic ester group to obtain an MOF-based polymer electrolyte; wherein the monomer containing the carbonic ester group is vinylethylene carbonate. A new thought is provided for solving the problem of stability of the functional filler in the composite electrolyte, and a material foundation is laid for developing a solid-state lithium battery with high safety and high energy density.

Description

Technical Field

[0001] This invention belongs to the field of energy materials technology, specifically relating to a MOF-based polymer electrolyte that can be polymerized in situ, its preparation method, and its application in solid-state lithium batteries. Background Technology

[0002] Lithium metal anodes are characterized by their extremely high theoretical specific capacity (3860 mAh·g). -1 It has an extremely low redox potential (-3.04 V vs. SHE) and a low density (0.53 g·cm³). -3 Solid-state lithium electrolytes (SPEs) are considered an ideal choice for next-generation high-energy-density batteries. However, traditional liquid electrolytes suffer from safety hazards such as lithium dendrites piercing the separator, leading to short circuits and flammability. Solid-state polymer electrolytes (SPEs) have attracted much attention due to their good flexibility, intrinsic safety, and potential for suppressing dendrites. However, traditional SPEs still face problems such as low room-temperature ionic conductivity, insufficient mechanical strength, and poor interfacial stability with lithium metal and high-voltage cathodes. Composite polymer electrolytes, through a structural design that combines rigidity and flexibility, possess advantages such as high safety, excellent flexibility, wide electrochemical window, high room-temperature ionic conductivity, and good electrode interfacial stability, bringing hope for the large-scale application of solid-state lithium batteries. However, the heterogeneous interface bonding problem of composite polymer electrolytes is its core challenge, mainly including poor physical contact, poor chemical compatibility, thermomechanical mismatch, discontinuous ion transport, and low electrochemical stability, which seriously affect the overall performance of the electrolyte and the cycle life of the battery.

[0003] Metal-organic frameworks (MOFs) offer opportunities to address the aforementioned challenges due to their ease of modification, designable nanopores, and abundant open metal sites (OMS). When composited into polymer matrices, their pore confinement effect optimizes lithium-ion transport pathways and accelerates desolvation; OMS, as strong Lewis acid sites, efficiently catalyzes lithium salt dissociation, increasing the lithium-ion transference number (tLi⁺). Furthermore, the chemical tunability of MOFs allows for improved affinity with polymer matrices through ligand modification. However, in composite electrolytes prepared using traditional physical mixing or doping methods, MOF molecules / particles are prone to migration, aggregation, and even sedimentation within the polymer matrix. This instability of MOFs within the electrolyte not only disrupts the homogeneity of the composite, hindering the sustained and effective functioning of its confined pores and OMS, but can also become defect points during cycling, affecting the continuity of ion transport and the long-term structural stability of the composite electrolyte. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide an in-situ polymerizable MOF-based polymer electrolyte, its preparation method, and its application in solid-state lithium batteries.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing an in-situ polymerizable MOF-based polymer electrolyte, comprising, UiO-66-FV was synthesized by introducing polymerizable unsaturated vinyl groups and fluorinated groups onto the MOF backbone; subsequently, UiO-66-FV was copolymerized in situ with monomers containing carbonate groups to obtain MOF-based polymer electrolytes. Among them, the monomer containing carbonate groups is ethylene carbonate.

[0008] As a preferred embodiment of the preparation method described in this invention, the preparation method of UiO-66-FV includes dissolving ZrCl4 in a polytetrafluoroethylene reactor liner containing N,N-dimethylformamide, ultrasonically dissolving it, adding 2-vinyl terephthalic acid and 4-fluoroterephthalic acid, continuing ultrasonic treatment, adding glacial acetic acid for drying, cooling and centrifuging, washing with DMF and methanol respectively, and finally vacuum drying.

[0009] As a preferred embodiment of the preparation method described in this invention, the in-situ copolymerization of UiO-66-FV with a monomer containing a carbonate group includes mixing ethylene carbonate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, and UiO-66-FV activated at high temperature, adding the crosslinking agent ethoxylated trimethylolpropane triacrylate, stirring at room temperature, and then adding the initiator azobisisobutyronitrile.

[0010] In a preferred embodiment of the preparation method described in this invention, the mass fraction of the UiO-66-FV is 6-10% of the total mass of lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalateborate.

[0011] In a preferred embodiment of the preparation method described in this invention, the molar ratio of ZrCl4, 2-vinyl terephthalic acid, and 4-fluoroterephthalic acid is 2~4:1~2:1~2.

[0012] In a preferred embodiment of the preparation method described in this invention, the amount of ethylene carbonate added is 0.5-2 ml; the mass ratio of lithium bis(trifluoromethanesulfonyl)imide to lithium difluorooxalate borate is 10-11:1.

[0013] As a preferred embodiment of the preparation method described in this invention, the UiO-66-FV after high-temperature activation is obtained by activating UiO-66-FV in a vacuum at 120°C for 12 hours.

[0014] Another objective of this invention is to overcome the shortcomings of the prior art and provide a MOF-based polymer electrolyte prepared by a specific method.

[0015] As a preferred embodiment of the preparation method described in this invention, the MOF-based polymer electrolyte has a room temperature ionic conductivity of ~0.68 mS / cm. -1 The electrochemical stability window is as wide as 4.8 V.

[0016] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of MOF-based polymer electrolyte in solid-state lithium batteries: Li||Li symmetric cells at 0.2 mA / cm 2 It can withstand stable cycling for more than 1400 hours and has a polarization voltage of <30 mV.

[0017] Beneficial effects of this invention: This invention fundamentally solves the problems of MOF dispersion and long-term stability in polymer electrolytes through covalent bond anchoring. Simultaneously, the PVEM electrolyte achieves superior performance through a triple synergistic mechanism: (1) MOF pore-confined transport: The mesoporous structure (~6.3 nm) of UiO-66-FV provides ordered ion channels, optimizing Li... ＋ Transport pathways promote uniform lithium deposition. (2) OMS catalytic dissociation: Open Zr in MOF 4＋ The site effectively catalyzes the dissociation of LiTFSI, and the combination of fluorinated groups to regulate the solvation structure significantly improves the ionic conductivity (30℃: 6.78 × 10⁻⁶). -4 S cm -1 ) and lithium-ion transference number (tLi ＋=0.76). (3) Fluorine / boron synergistic interface engineering: The dynamic electrochemical reaction synergistic effect of MOF fluoride groups and LiDFOB salts constructs a composite SEI rich in high modulus LiF and flexible LiBOx / Li2BxFy in situ at the negative electrode; and a stable CEI rich in CF, LiF and BF in situ at the positive electrode. These interface layers effectively adapt to volume changes, inhibit lithium dendrite growth, prevent continuous electrolyte decomposition, and significantly broaden the electrochemical window (4.8 V). Thanks to this, PVEM exhibits excellent electrochemical performance: Li||Li symmetric cells at 0.2 mAcm -2 The battery achieved stable cycling for over 1400 hours (polarization <30 mV); the full cell matched with high-voltage LiCoO2 (4.3 V) maintained a capacity retention of 77.0% after 200 cycles at 0.5 C, with an average coulombic efficiency as high as 99.8%. Even with the cutoff voltage increased to 4.5 V, the full cell still operated stably. The "MOF giant monomer covalent anchoring" strategy proposed in this invention provides a new approach to solving the stability problem of functional fillers in composite electrolytes, laying a material foundation for the development of high-safety, high-energy-density solid-state lithium batteries. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is the PVEM electrolyte XRD pattern of an embodiment of the present invention.

[0019] Figure 2 This is the PVEM electrolyte infrared spectrum of an embodiment of the present invention.

[0020] Figure 3 The PVEM electrolyte XPS is an embodiment of the present invention.

[0021] Figure 4 The SEM elements of the PVEM electrolyte in this embodiment of the invention are shown.

[0022] Figure 5 This invention relates to lithium symmetric cycling of PVE electrolyte and PVEM electrolyte in embodiments of the present invention.

[0023] Figure 6 This is a digital photograph of a lithium plate after cycling according to an embodiment of the present invention, wherein, Figure 6 (a) A digital photograph of the lithium plate after PVE electrolyte circulation; Figure 6 (b) is a digital photograph of the lithium plate after PVEM electrolyte cycling.

[0024] Figure 7 This is a SEM image of a lithium sheet after electrolyte cycling according to an embodiment of the present invention, wherein, Figure 7 (a) is a SEM image of the lithium sheet after PVE electrolyte cycling; Figure 7 (b) is a SEM image of the lithium sheet after PVEM electrolyte cycling.

[0025] Figure 8 The cycling performance of LFP cells in PVE and PVEM electrolytes is shown in the embodiments of the present invention.

[0026] Figure 9 This is a cycling diagram of the lithium cobalt oxide cathode of the PVE electrolyte and PVEM electrolyte in an embodiment of the present invention.

[0027] Figure 10 The figures show the charge-discharge plateau curves of the PVEM electrolyte at different numbers of cycles in embodiments of the present invention.

[0028] Figure 11 This is a comparison chart of PVEM electrolyte ratios in embodiments of the present invention.

[0029] Figure 12 The PVEM rate test charge-discharge curves are shown in the embodiments of the present invention.

[0030] Figure 13 To demonstrate the excellent ion transport performance of the PVEM electrolyte in this embodiment of the invention, wherein, Figure 13 (a) Impedance diagrams of PVE electrolyte and PVEM electrolyte; Figure 13 (b) shows the comparison of electrical conductivity; Figure 13 (c) shows the comparison of activation energies; Figure 13 (d) represents the lithium-ion transference number in PVEM; Figure 13 (e) Comparison of lithium-ion transference numbers in PVE and PVEM electrolytes with different MOF monomer ratios; Figure 13 (f) shows the comparison of electrochemical windows. Detailed Implementation

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0032] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0033] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0034] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available. See Table 1 for details.

[0035] Table 1

[0036] Example 1 (1) Synthesis of fluorinated MOF monomers: Weigh 0.76 mmol (ZrCl4) (0.177 g) and dissolve it in a polytetrafluoroethylene reactor liner containing 30 mL of N,N-dimethylformamide (DMF). After complete sonication and dissolution, slowly add 0.38 mmol 2-vinyl terephthalic acid (73 mg) and 0.38 mmol 4-fluoroterephthalic acid (90 mg) while stirring. Continue sonication for 30 min to ensure thorough mixing. Then, add 1 mL of glacial acetic acid using a pipette to adjust the crystal structure of the MOFs, and then fill the reactor and seal it. Place the reactor in a forced-air drying oven at 120 °C for 24 h. After cooling, centrifuge and wash the MOFs three times each with DMF and methanol. Finally, place it in a vacuum drying oven at 60 °C and dry for 12 h. After removing the fluorinated MOF monomer UIO-66-F4-CH=CH2 (UIO-66-FV), store it in a desiccator or glove box.

[0037] (2) Preparation of polycarbonate-based polymer electrolytes: PVEM: First, a precursor solution was prepared by adding 1 mL of VEC, 0.287 g (1M LiTFSI), 0.028 g (0.2 M LiDFOB), and 25 mg of MOFs (UIO-66-FV) that had undergone high-temperature activation (vacuum activation at 120℃ for 12 h) and were thoroughly ground into a 5 mL glass vial and stirred in a glove box. Then, 100 μL (10% wt) of ETPTA was added as a crosslinking agent using a pipette, and the mixture was stirred overnight at room temperature. Finally, 2% wt of AIBN was added to the precursor solution as an initiator and dissolved completely. Using a glass fiber membrane as a substrate, 40 μL of the solution was added dropwise to each side to assemble a coin cell. After assembly, the cells were thermocured at 60 ℃ for 12 h to spontaneously form a polymer solid-state battery.

[0038] Example 2 The difference from Example 1 is that the amount of MOFs (UIO-66-FV) added is 20mg, while the rest is the same as Example 1.

[0039] Example 3 The difference from Example 1 is that the amount of MOFs (UIO-66-FV) added is 30mg, while the rest is the same as Example 1.

[0040] Comparative Example 1 The difference from Example 1 is that the polymer electrolyte (PVE) without MOFs (UIO-66-FV) was not added; otherwise, it was the same as Example 1. Specifically, a precursor solution was prepared by adding 1 mL of VEC, 0.287 g (1M LiTFSI), and 0.028 g (0.2M LiDFOB) to a 5 mL glass vial and stirring it in a glove box. Then, 100 μL (10% wt) of ETPTA was added as a crosslinking agent using a pipette, and the solution was stirred overnight at room temperature. Finally, 2% wt of AIBN was added to the precursor solution as an initiator and dissolved completely. Using a glass fiber membrane as a substrate, 40 μL of the solution was added dropwise to each side to assemble a coin cell. After assembly, the cell was thermocured at 60 °C for 12 h to spontaneously form a polymer solid-state battery.

[0041] Comparative Example 2 The difference from Example 1 is that the amount of MOFs (UIO-66-FV) added is 10mg, while the rest is the same as Example 1.

[0042] Comparative Example 3 The difference from Example 1 is that the amount of MOFs (UIO-66-FV) added is 40mg, otherwise it is the same as Example 1.

[0043] X-ray diffraction (XRD) confirmed the successful construction of the MOF framework. Figure 1 The diffraction peaks of the UiO-66-FV monomer highly match the standard spectrum of UiO-66, indicating that the cubic lattice structure of the MOF has been fully formed. Fourier transform infrared spectroscopy (FTIR) further confirms the evolution of its functional group composition. Figure 2 This confirms the completion of the crosslinking reaction and the successful introduction of the fluorinated group. The XPS spectrum of UiO-66-FV shows that Zr3d is in a relatively high binding energy state ( Figure 3 This indicates the presence of open metal sites. To observe the microstructure of the in-situ prepared PVEM electrolyte, the assembled battery was disassembled, and scanning electron microscopy images and elemental EDS-mapping tests were performed. Figure 4The uniform distribution of Zr (MOF metal nodes) and F (fluorinated groups) elements indicates that the MOF framework and polymer matrix form a chemically homogeneous composite structure. This homogeneity avoids local ion transport "hot spots," laying the foundation for the in-situ homogeneous construction of the lithium fluoride (LiF) SEI in subsequent cycling. These results demonstrate that the PVEM in-situ synthesis strategy, through structure-chemistry synergistic design, achieves the preparation of a highly homogeneous composite electrolyte, providing a key materials science basis for subsequent ion transport regulation and interface stabilization mechanisms.

[0044] The unique structural advantages and superior ionic properties of PVEM electrolytes contribute to their enhanced electrochemical performance. To further test the long-cycle stability of the composite electrolyte, the electrochemical performance of a Li / / Li symmetric battery was assembled and tested. Figure 5 As shown, at 0.2 mA cm -2 At current densities, the polarization potential exceeds 100 mV. The PVEM composite electrolyte exhibits better lithium stability, achieving an ultra-long cycling duration of over 1400 h under optimal grafting ratio conditions, with an average polarization potential as low as 30 mV. (Digital photograph of the lithium sheet after cycling is included.) Figure 6 The SEM comparison images show that the lithium foil after PVEM cycling is smoother than that after PVE cycling. Figure 7 This indicates that its negative electrode stability is superior.

[0045] To further demonstrate the excellent electrochemical performance of the PVEM composite electrolyte, Li / PVE / LFP and Li / PVEM / LFP full cells were assembled, and their long-term cycling stability was tested at 30 °C and 2.7–4 V. Figure 8 As shown, the Li / PVE / LFP battery exhibited rapid capacity decay after 120 cycles at 0.2 C, and its specific capacity dropped to 40.0 mAh g⁻¹ after 300 cycles. This indicates that as the battery continues to cycle, the PVE electrolyte is continuously oxidized and decomposed, leading to capacity decay. In contrast, the Li / PVEM / LFP full cell maintained a capacity retention of 90.0% even after nearly 300 stable cycles, demonstrating excellent long-term cycling stability.

[0046] Given the excellent cycle stability exhibited by the Li / LFP full cell assembled with the composite electrolyte, the high-voltage stability of the composite electrolyte will be further verified by matching it with a higher-voltage LCO cathode material. Figure 9 and Figure 10As shown, within the charge-discharge voltage range of 3-4.3 V, the Li / PVE / LFP battery experienced rapid capacity decay at a high rate of 0.5 C. In contrast, the battery assembled using the PVEM composite electrolyte maintained long-term cycle stability. The initial discharge specific capacity of the Li / PVEM / LCO full cell was approximately 151.4 mAh g⁻¹. -1 After activation at 0.1 C for 2 cycles, it can stably cycle for over 200 cycles at 0.5 C, with a discharge specific capacity still as high as 118.5 mAh g⁻¹. -1 The average coulombic efficiency reaches 99.8%. Furthermore, when the PVEM composite electrolyte is matched with the LCO cathode material, it still exhibits excellent rate performance. Figure 11 (12). Within the charge-discharge voltage range of 3-4.2 V at 30 °C, the discharge specific capacities of the Li / PVEM / LCO full cell at different C rates of 0.1, 0.2, 0.5, 1, 1.5, and 2 C are 147.4, 140.4, 130.6, 127.4, 123.4, and 113.4 mAh g, respectively. -1 When the discharge rate rapidly recovers from 2 C to 0.2 C, the discharge specific capacity can also quickly increase to 140.4 mAh g. -1 .

[0047] To further demonstrate the excellent ion transport performance of the PVEM electrolyte, a steel symmetric (SS / / SS) cell was used to conduct relevant tests on ionic conductivity. The AC impedance spectra and calculations of the electrolyte (Figures 13a, b) show that at 30 °C, the ionic conductivity of the fluorinated MOF polycarbonate electrolyte increases from 2.48 × 10⁻⁶. -4 S cm -1 Increased to 6.78×10 -4 S cm -1 This is thanks to the porous structure of the MOF itself, which provides additional channels for lithium-ion transport. By measuring the impedance under different temperature conditions and combining it with the Arrhenius equation, the activation energy of PVE also decreased from 0.163 eV to 0.149 eV for PVEM. Figure 13 c). Furthermore, the lithium transference number (tLi) + It can also be used to evaluate the ion mobility of electrolytes. Lithium-symmetric tLi assembled using PVE, PVEM, and PVEM-n (n represents the mass of MOF monomer added) electrolytes were tested respectively. + The result is as follows Figure 13As shown in Figure e, the lowest lithium-ion migration number (LN) was observed at an addition amount of 25 mg, at only 0.43. This is because the rigid ester backbone in PVE electrolytes restricts the movement of molecular chains, thus affecting the lithium-ion migration rate. Simultaneously, the strong interaction between polycarbonate and ions also increases the resistance to ion migration. These factors all contribute to the low lithium-ion migration rate (tLi). + A key reason for the lower efficiency. In contrast, with the introduction of UiO-66-FV, the lithium-ion transference number of the composite electrolytes was improved to varying degrees. As shown in Figure 13d, the Li / PVEM / Li transference number increased by nearly double, reaching 0.76. This is because the introduction of MOF grafting first enhances the mobility of the polyester skeleton, and secondly, the presence of OMS in the channels effectively restricts the movement of anions, thus acting as an ion sieve and greatly improving the migration ability of lithium ions. In addition, the presence of strongly electronegative F side chain groups effectively regulates the electron cloud distribution along the porous channel direction, which not only promotes the dissociation of lithium salts but also enhances the capture behavior of TFSI- anions. To further evaluate the antioxidant capacity of PVEM electrolyte, Li / / SS batteries were assembled, and the electrochemical window of the electrolyte was tested, such as... Figure 13 As shown in f, the electrochemical window of the PVEM electrolyte is broadened to 4.8 V. Its significantly improved oxidation stability allows for matching with cathode materials at higher voltages.

[0048] This invention prepares a bifunctional (fluorinated, vinyl) MOF material (UiO-66-FV). It was used as a "giant monomer" and copolymerized in situ with vinylene carbonate (VEC) monomer to successfully construct a high-performance MOF-based dual-salt polymer electrolyte (PVEM). The core advantage of this design is that it fundamentally solves the problems of MOF dispersion and long-term stability in polymer electrolytes through covalent bond anchoring. At the same time, the PVEM electrolyte achieves excellent performance through a triple synergistic mechanism: (1) MOF pore confinement transport: The mesoporous structure (~6.3 nm) of UiO-66-FV provides ordered ion channels, optimizing Li ＋ Transport path, promoting uniform lithium deposition. (2) OMS catalytic dissociation: open Zr in MOF 4＋ The site effectively catalyzes the dissociation of LiTFSI, and the combination of fluorinated groups to regulate the solvation structure significantly improves the ionic conductivity (30℃: 6.78 × 10⁻⁶). -4 S cm -1 ) and lithium-ion transference number (tLi ＋=0.76). (3) Fluorine / boron synergistic interface engineering: The dynamic electrochemical reaction synergistic effect of MOF fluoride groups and LiDFOB salts constructs high-modulus LiF and flexible LiBO in situ at the negative electrode. x / Li2B x F y A composite SEI was constructed; a stable CEI rich in CF, LiF, and BF was built in situ at the cathode. These interfacial layers effectively adapted to volume changes, suppressed lithium dendrite growth, prevented continuous electrolyte decomposition, and significantly broadened the electrochemical window (4.8V). Thanks to this, PVEM exhibited excellent electrochemical performance: the Li||Li symmetric cell achieved a voltage drop of 0.2 mA cm⁻¹. -2 The battery achieved stable cycling for over 1400 hours (polarization <30 mV); the full cell matched with high-voltage LiCoO2 (4.3 V) maintained a capacity retention of 77.0% after 200 cycles at 0.5 C, with an average coulombic efficiency as high as 99.8%. Even with the cutoff voltage increased to 4.5 V, the full cell still operated stably. The "MOF giant monomer covalent anchoring" strategy proposed in this invention provides a new approach to solving the stability problem of functional fillers in composite electrolytes, laying a material foundation for the development of high-safety, high-energy-density solid-state lithium batteries.

[0049] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing an in-situ polymerizable MOF-based polymer electrolyte, characterized in that: include, UiO-66-FV was synthesized by introducing polymerizable unsaturated vinyl groups and fluorinated groups onto the MOF backbone; subsequently, UiO-66-FV was copolymerized in situ with monomers containing carbonate groups to obtain MOF-based polymer electrolytes. Among them, the monomer containing carbonate groups is ethylene carbonate.

2. The preparation method according to claim 1, characterized in that: The preparation method of the UiO-66-FV includes dissolving ZrCl4 in a polytetrafluoroethylene reactor liner containing N,N-dimethylformamide, ultrasonically dissolving it, adding 2-vinyl terephthalic acid and 4-fluoroterephthalic acid, continuing ultrasonic treatment, adding glacial acetic acid for drying, cooling and centrifuging, washing with DMF and methanol respectively, and finally vacuum drying.

3. The preparation method according to claim 1, characterized in that: The in-situ copolymerization of UiO-66-FV with monomers containing carbonate groups includes mixing ethylene carbonate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate and UiO-66-FV activated at high temperature, adding the crosslinking agent ethoxylated trimethylolpropane triacrylate, stirring at room temperature, and then adding the initiator azobisisobutyronitrile.

4. The preparation method according to claim 3, characterized in that: The mass fraction of the UiO-66-FV is 6-10% of the total of lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalateborate.

5. The preparation method according to claim 2, characterized in that: The molar ratio of ZrCl4, 2-vinyl terephthalic acid, and 4-fluoroterephthalic acid is 2~4:1~2:1~2.

6. The preparation method according to claim 3, characterized in that: The amount of ethylene carbonate added is 0.5~2 ml; the mass ratio of lithium bis(trifluoromethanesulfonyl)imide to lithium difluorooxalate borate is 10~11:

1.

7. The preparation method according to claim 3, characterized in that: The UiO-66-FV that has been activated at high temperature is obtained by placing UiO-66-FV in a vacuum at 120°C for 12 hours.

8. The MOF-based polymer electrolyte prepared by the preparation method according to claims 1 to 7.

9. The MOF-based polymer electrolyte as described in claim 8, characterized in that: Room temperature ionic conductivity ~0.68 mS / cm -1 The electrochemical stability window is as wide as 4.8 V.

10. The application of the MOF-based polymer electrolyte as described in claim 9 in solid-state lithium batteries, characterized in that: The Li||Li symmetric cell at 0.2 mA / cm 2 It can withstand stable cycling for more than 1400 hours and has a polarization voltage of <30 mV.

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