A MOF-filled polymer solid electrolyte membrane, its preparation method and application

Abstract

This invention discloses a MOF-filled polymer solid electrolyte membrane, its preparation method, and its application, belonging to the field of solid electrolyte technology. The composite solid electrolyte membrane comprises poly(vinylidene fluoride-hexafluoropropylene), lithium bis(trifluoromethanesulfonylimide), and Zn-ddmb metal-organic framework filler. The preparation method includes: preparing Zn-ddmb filler; dissolving the polymer and lithium salt to obtain a polymer electrolyte precursor solution; adding Zn-ddmb for dispersion, followed by solution casting and vacuum drying to obtain the composite solid electrolyte membrane. Zn-ddmb can improve the ion transport environment, increasing ionic conductivity, electrochemical stability, and lithium metal interface stability. Preferably, when the Zn-ddmb addition amount is 20% of the polymer mass, the resulting electrolyte membrane has an ionic conductivity of 0.000626 S / cm and an electrochemical stability window of 4.52 V, suitable for high-safety lithium metal batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte technology, specifically relating to a polymer-based metal-organic framework composite solid electrolyte membrane, its preparation method, and its application in lithium metal batteries. Background Technology

[0002] With the rapid development of new energy vehicles, portable electronic devices, wearable devices, and large-scale energy storage systems, the demand for high energy density, high safety, and long cycle life in lithium batteries is constantly increasing. Traditional lithium-ion batteries typically use liquid organic electrolytes as ion transport media. Although these electrolytes have high ionic conductivity and good electrode wettability, they also have problems such as easy leakage, volatility, flammability, and the potential for side reactions under high voltage or high temperature conditions. These issues can easily lead to battery capacity decay, interface failure, and even thermal runaway risks, limiting their further application in high-safety energy storage devices.

[0003] Replacing traditional liquid electrolytes with solid-state electrolytes is considered an important way to improve the safety and stability of lithium batteries. Solid-state electrolytes typically possess better thermal stability and mechanical strength, which can reduce the risk of electrolyte leakage and combustion to some extent, and help suppress lithium dendrite growth. Currently, solid-state electrolytes mainly include inorganic solid-state electrolytes, polymer solid-state electrolytes, and organic-inorganic composite solid-state electrolytes. Among them, polymer solid-state electrolytes have advantages such as good flexibility, ease of processing, ease of film formation, and good contact with the electrode interface, showing good application potential in flexible batteries and quasi-solid-state lithium metal batteries. However, polymer solid-state electrolytes generally suffer from insufficient room-temperature ion transport capacity, low lithium-ion transference number, and poor interface stability during long-term cycling, making it difficult to simultaneously meet the application requirements of high safety and high performance lithium metal batteries.

[0004] To improve the overall performance of polymer solid electrolytes, common methods include polymer copolymerization, crosslinking modification, introduction of plasticizers, and addition of inorganic or organic functional fillers. Among these, adding functional fillers to the polymer matrix is ​​a relatively effective modification strategy. The introduction of appropriate fillers can reduce the crystallinity of polymer segments, increase the proportion of amorphous regions, enhance the mechanical strength of the electrolyte membrane, and improve the lithium-ion migration environment. However, traditional inorganic fillers typically exist in the polymer matrix as discrete particles, which are prone to aggregation and have limited interfacial interactions with the polymer matrix and lithium salt, making it difficult to form continuous and effective lithium-ion transport channels. Excessive fillers may also cause membrane structure defects or increased interfacial impedance, thereby affecting the battery's cycle stability.

[0005] Metal-organic frameworks (MOFs) are a class of porous materials constructed from metal ions or metal clusters and organic ligands through coordination interactions. They typically possess high specific surface areas, tunable pore structures, abundant metal active sites, and good structural designability. When MOFs are used as fillers in polymer solid electrolytes, their porous structure provides auxiliary channels for lithium-ion migration, the rigid framework helps suppress polymer segment crystallization and enhances the mechanical strength of the electrolyte membrane, and the polar groups in the metal sites and organic ligands may interact with lithium salt anions or polymer segments, thereby promoting lithium salt dissociation, increasing the concentration of free lithium ions, and improving lithium-ion migration behavior.

[0006] Patent document CN121905942A discloses a metal-organic framework-polymer composite solid electrolyte and its preparation method. This method involves surface modification of UiO-66 with a modified coupling agent, followed by polymerization into a film after composite formation with a modified complex system. The film is then immersed in a lithium salt ethanol solution to obtain the metal-organic framework-polymer composite solid electrolyte membrane. This method improves the interfacial compatibility between the metal-organic framework material and the polymer matrix by modifying UiO-66, and enhances lithium-ion transport performance. However, this method requires modification of UiO-66 with a coupling agent and involves steps such as constructing the modified complex system, gel film polymerization, and subsequent lithium salt immersion, making the preparation process relatively complex. Furthermore, this method mainly focuses on the composite formation of modified UiO-66 with a specific polymer complex system and does not address the direct dispersion of zinc-based metal-organic framework fillers in a poly(vinylidene fluoride-hexafluoropropylene) / bis(trifluoromethanesulfonyl)imide lithium system or its effect on ion transport behavior and lithium metal interface stability.

[0007] Therefore, developing a metal-organic framework composite solid electrolyte membrane that is easy to prepare, can be well dispersed in a polymer matrix, and has the functions of regulating pore structure and metal active sites is of great significance for improving the ionic conductivity, electrochemical stability and lithium metal interface stability of polymer-based solid electrolytes. Summary of the Invention

[0008] Given the shortcomings of existing polymer solid electrolytes, such as insufficient room-temperature ion transport capacity, narrow electrochemical stability window, low lithium-ion transference number, and insufficient lithium metal interface stability, and considering the existing metal-organic framework-polymer composite solid electrolyte systems also suffer from insufficient filler dispersion, limited interfacial interactions, or complex preparation processes, the present invention aims to provide a MOF-filled polymer solid electrolyte membrane, its preparation method, and its applications. This composite solid electrolyte membrane incorporates a zinc-based metal-organic framework filler, Zn-ddmb, into a poly(vinylidene fluoride-hexafluoropropylene) / bis(trifluoromethanesulfonylimide) lithium system. The porous framework structure, metal active sites, and polar ligand groups of Zn-ddmb improve the ion transport environment in the polymer matrix, thereby enhancing the ionic conductivity, electrochemical stability, and lithium metal interface stability of the composite solid electrolyte membrane.

[0009] To achieve the above objectives, the present invention provides the following technical solutions.

[0010] A polymer-based metal-organic framework composite solid electrolyte membrane includes a polymer matrix, a lithium salt, and a metal-organic framework filler; the polymer matrix is ​​poly(vinylidene fluoride-hexafluoropropylene), the lithium salt is lithium bis(trifluoromethanesulfonylimide), and the metal-organic framework filler is Zn-ddmb, wherein the Zn-ddmb is dispersed in the polymer matrix.

[0011] In a further preferred embodiment, the Zn-ddmb is a metal-organic framework material formed by the coordination of zinc ions with 1,4-bis(5,6-dicarboxybenzimidazole-methyl)benzene.

[0012] In a further preferred embodiment, the amount of Zn-ddmb added is 1% to 30% of the mass of poly(vinylidene fluoride-hexafluoropropylene). More preferably, the amount of Zn-ddmb added is 10% to 30% of the mass of poly(vinylidene fluoride-hexafluoropropylene), and even more preferably 20%.

[0013] In a further preferred embodiment, the mass ratio of poly(vinylidene fluoride-hexafluoropropylene) to lithium bis(trifluoromethanesulfonylimide) is 3:1, and the thickness of the composite solid electrolyte membrane is 20~40 μm.

[0014] This invention also provides a method for preparing the above-mentioned polymer-based metal-organic framework composite solid electrolyte membrane, comprising the following steps: (1) Dissolve zinc salt and 1,4-bis(5,6-dicarboxybenzimidazole-methyl)benzene in an organic solvent, add an acid regulator and heat to react, then cool, wash, filter and dry to obtain Zn-ddmb metal-organic framework filler; (2) Poly(vinylidene fluoride-hexafluoropropylene) and lithium bis(trifluoromethanesulfonylimide) were added to an organic solvent and heated and stirred to obtain a polymer electrolyte precursor solution; (3) Add the Zn-ddmb metal-organic framework filler obtained in step (1) to the polymer electrolyte precursor solution obtained in step (2), and continue heating and stirring to disperse Zn-ddmb in the polymer electrolyte precursor solution to obtain the composite electrolyte precursor solution; (4) The composite electrolyte precursor solution obtained in step (3) is solution cast and dried under vacuum to obtain a polymer-based metal-organic framework filler composite solid electrolyte membrane.

[0015] In a further preferred embodiment, in step (1), the zinc salt is ZnCl2, the organic solvent is a mixture of N,N-dimethylacetamide and acetonitrile, the acidity regulator is nitric acid, the heating reaction temperature is 60~100 ℃, and the reaction time is 72~144 h.

[0016] In a further preferred embodiment, in steps (2) and (3), the organic solvent is N,N-dimethylformamide, the mass ratio of poly(vinylidene fluoride-hexafluoropropylene) to lithium bis(trifluoromethanesulfonylimide) is 3:1, and the amount of Zn-ddmb metal-organic framework filler added is 1% to 30% of the mass of poly(vinylidene fluoride-hexafluoropropylene).

[0017] In a further preferred embodiment, in step (4), the vacuum drying temperature is 60~100 ℃ and the drying time is 8~24 h.

[0018] This invention also provides the application of the above-mentioned polymer-based metal-organic framework composite solid electrolyte membrane in lithium batteries. Preferably, the composite solid electrolyte membrane is disposed between the positive and negative electrodes, serving as an ion transport medium and a separator; the lithium battery is a lithium metal battery.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) In this invention, Zn-ddmb is introduced into the poly(vinylidene fluoride-hexafluoropropylene) matrix. The porous structure, metal sites and polar ligand groups of Zn-ddmb can improve the lithium ion transport environment in the composite solid electrolyte membrane and increase the ionic conductivity.

[0020] (2) The introduction of Zn-ddmb in this invention is beneficial to promoting the dissociation of lithium salt and increasing the lithium ion transference number of the composite solid electrolyte membrane.

[0021] (3) The composite solid electrolyte membrane provided by the present invention has a wide electrochemical stability window, which is beneficial to improving its compatibility with cathode materials.

[0022] (4) The composite solid electrolyte membrane provided by the present invention can improve the stability of the lithium metal interface, help reduce polarization during cycling, and improve the cycling stability of lithium metal batteries.

[0023] (5) The present invention does not require complex coupling agent surface modification of MOF filler, nor does it require subsequent lithium salt soaking treatment. The composite solid electrolyte membrane can be obtained by mixing Zn-ddmb with polymer electrolyte precursor liquid, solution casting and vacuum drying. The preparation method is simple, and the resulting composite solid electrolyte membrane is uniform and has controllable thickness, which is suitable for lithium metal batteries. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the Zn-ddmb metal-organic framework filler prepared by the method described in Example 1 of the present invention.

[0025] Figure 2 The image shows a scanning electron microscope image of the Zn-ddmb metal-organic framework packing material prepared by the method described in Example 1 of this invention.

[0026] Figure 3 The powder X-ray diffraction pattern of the Zn-ddmb metal-organic framework filler prepared by the method described in Example 1 of this invention.

[0027] Figure 4 An optical photograph of the composite electrolyte precursor solution obtained when preparing the composite solid electrolyte membrane using the method described in Example 3 of this invention.

[0028] Figure 5 This is a cross-sectional scanning electron microscope image of the composite solid electrolyte membrane prepared by the method described in Example 3 of the present invention.

[0029] Figure 6 The graph shows the ionic conductivity test results of SS / / SS batteries prepared by the method described in Examples 2-4 and Comparative Example 1 of this invention at different temperatures, where x in Zn-ddmb-x represents the percentage of Zn-ddmb added to the mass of poly(vinylidene fluoride-hexafluoropropylene).

[0030] Figure 7 The graph shows the electrochemical stability window test results of the SS / / Li batteries prepared by the method described in Examples 2-4 and Comparative Example 1 of this invention, where x in Zn-ddmb-x represents the percentage of Zn-ddmb added to the mass of poly(vinylidene fluoride-hexafluoropropylene).

[0031] Figure 8 The graph shows a comparison of the lithium-ion transference number test results of Li / / Li batteries prepared by the method described in Examples 2-4 and Comparative Example 1 of this invention.

[0032] Figure 9The graph shows the constant current charge-discharge cycle performance test results of the Li / / Li symmetric batteries prepared by the method described in Examples 2-4 and Comparative Example 1 of this invention, where x in Zn-ddmb-x represents the percentage of Zn-ddmb added to the mass of poly(vinylidene fluoride-hexafluoropropylene).

[0033] Figure 10 The graphs show the cycle performance test results of LFP / / Li batteries prepared by the method described in Examples 2-4 and Comparative Example 1 of this invention. Detailed Implementation

[0034] This invention introduces a zinc-based metal-organic framework material, Zn-ddmb, into a polymer solid electrolyte system composed of poly(vinylidene fluoride-hexafluoropropylene) and lithium bis(trifluoromethanesulfonylimide). The porous framework structure and exposed metal sites of Zn-ddmb improve the ion transport environment in the composite solid electrolyte membrane, thereby enhancing the ionic conductivity, electrochemical stability, lithium-ion transference number, and electrode / electrolyte interface stability of the composite solid electrolyte membrane.

[0035] Specifically, this invention provides a method for preparing a polymer-based metal-organic framework composite solid electrolyte membrane, comprising the following steps: first, preparing a Zn-ddmb metal-organic framework filler; then dissolving poly(vinylidene fluoride-hexafluoropropylene) and lithium bis(trifluoromethanesulfonylimide) in an organic solvent to obtain a polymer electrolyte precursor solution; then adding Zn-ddmb to the polymer electrolyte precursor solution and stirring to disperse it evenly to obtain a composite electrolyte precursor solution; finally, casting the composite electrolyte precursor solution into a solution and drying it under vacuum conditions to obtain a Zn-ddmb / PVDF-HFP / LiTFSI composite solid electrolyte membrane.

[0036] To facilitate understanding of the present invention, the following description, in conjunction with the accompanying drawings and preferred embodiments, further illustrates the invention. However, the scope of protection of the present invention is not limited to the specific embodiments described below. Unless otherwise specified, the raw materials, reagents, and equipment used in the present invention are all commercially available or prepared using conventional methods in the art.

[0037] Example 1: Preparation of Zn-ddmb metal-organic framework filler.

[0038] Weigh 0.09 g ZnCl2 and 0.03 g 1,4-bis(5,6-dicarboxybenzimidazole-methyl)benzene and dissolve them in a mixed solvent consisting of 12 mL N,N-dimethylacetamide and 4 mL acetonitrile. Stir the resulting mixture continuously for 3 h to ensure complete and uniform dispersion.

[0039] Distribute the mixed solution evenly into a 20 mL reagent bottle, and add 300 μL of 1 mol / L nitric acid to adjust the pH to 7.0 ± 0.1.

[0040] The reagent bottle was heated at 80 °C in a forced-air drying oven for 5 days and then cooled to room temperature to obtain a colorless blocky Zn-ddmb.

[0041] The obtained product was thoroughly washed with a mother liquor consisting of 12 mL N,N-dimethylacetamide and 4 mL acetonitrile, filtered, and dried to finally obtain a white Zn-ddmb powder.

[0042] Example 2: Preparation of Zn-ddmb-10 composite solid electrolyte membrane.

[0043] Weigh 0.6 g of poly(vinylidene fluoride-hexafluoropropylene) and 0.2 g of lithium bis(trifluoromethanesulfonylimide) at a mass ratio of 3:1, add them to a 20 mL reagent bottle, add an appropriate amount of N,N-dimethylformamide as a solvent, and stir for 4 h to fully dissolve the poly(vinylidene fluoride-hexafluoropropylene) and lithium bis(trifluoromethanesulfonylimide) to obtain the polymer electrolyte precursor solution.

[0044] The Zn-ddmb metal-organic framework filler prepared in Example 1 was added to the polymer electrolyte precursor solution, wherein the mass of Zn-ddmb was 10% of the mass of poly(vinylidene fluoride-hexafluoropropylene). Stirring was continued at 60 °C for 8 h to ensure uniform dispersion of Zn-ddmb in the polymer electrolyte precursor solution, thus obtaining the composite electrolyte precursor solution.

[0045] The obtained composite electrolyte precursor solution was uniformly cast into a 90 mm diameter glass dish and dried in a vacuum drying oven at 80 ℃ for 12 h to remove N,N-dimethylformamide solvent, yielding a Zn-ddmb / PVDF-HFP / LiTFSI composite solid electrolyte membrane. The thickness of the obtained composite solid electrolyte membrane was 20–40 μm. The obtained composite solid electrolyte membrane was cut into circular pieces with a diameter of 16 mm and stored in an inert atmosphere for later use. This sample was designated Zn-ddmb-10.

[0046] Example 3: Preparation of Zn-ddmb-20 composite solid electrolyte membrane.

[0047] The difference between this embodiment and Example 2 is that the mass of Zn-ddmb is 20% of the mass of poly(vinylidene fluoride-hexafluoropropylene). The amounts of other raw materials, solvents, stirring conditions, casting conditions, and drying conditions are the same as in Example 2, resulting in a Zn-ddmb / PVDF-HFP / LiTFSI composite solid electrolyte membrane. The obtained sample is designated Zn-ddmb-20.

[0048] Example 4: Preparation of Zn-ddmb-30 composite solid electrolyte membrane.

[0049] The difference between this embodiment and Embodiment 2 is that the mass of Zn-ddmb is 30% of the mass of poly(vinylidene fluoride-hexafluoropropylene). The amounts of other raw materials, solvents, stirring conditions, casting conditions, and drying conditions are the same as in Embodiment 2, resulting in a Zn-ddmb / PVDF-HFP / LiTFSI composite solid electrolyte membrane. The obtained sample is designated Zn-ddmb-30.

[0050] Comparative Example 1: Preparation of polymer solid electrolyte membrane without Zn-ddmb.

[0051] Compared to Example 2, the only difference is that Zn-ddmb metal-organic framework filler was not added in this comparative example. The mass ratio of poly(vinylidene fluoride-hexafluoropropylene) to lithium bis(trifluoromethanesulfonylimide), the organic solvent, the stirring conditions, the casting conditions, and the vacuum drying conditions were all the same as in Example 2, resulting in a PVDF-HFP / LiTFSI polymer solid electrolyte membrane. The obtained sample was designated Zn-ddmb-0.

[0052] Battery assembly and performance testing

[0053] The solid electrolyte membranes prepared in Examples 2-4 and Comparative Example 1 were assembled into test batteries according to the following method: In a glove box under an inert protective atmosphere, the solid electrolyte membranes were assembled with stainless steel sheets, lithium metal sheets, and lithium iron phosphate electrodes, respectively, to obtain SS / / SS batteries, SS / / Li batteries, Li / / Li symmetric batteries, and LFP / / Li coin cells. The lithium iron phosphate electrodes were prepared from lithium iron phosphate, a conductive agent, and a binder in a mass ratio of 8:1:1, with an active material loading of 1.36~1.42 mg / cm³. 2 The diameter of the lithium metal sheet is 16 mm. After the assembled battery was left to stand for 8 hours, its electrochemical performance was tested.

[0054] The Zn-ddmb composite solid electrolyte membranes and their assembled batteries prepared in the above examples and comparative examples were characterized structurally and tested for electrochemical performance. The results are as follows.

[0055] like Figure 1 As shown, Zn-ddmb is constructed by coordination between Zn metal nodes and organic ligand ddmb, and has a periodic porous framework structure. Figure 2 The image shows a scanning electron microscope image of the prepared Zn-ddmb, which indicates that Zn-ddmb has a relatively regular blocky morphology. Figure 3The powder X-ray diffraction pattern of Zn-ddmb is shown. The results indicate that the positions of the main diffraction peaks in the experimental pattern are consistent with those in the simulated pattern, suggesting that the prepared Zn-ddmb has good phase purity. Figure 4 As shown, the composite electrolyte precursor solution obtained after adding Zn-ddmb is in a uniform slurry state, indicating that Zn-ddmb can be well dispersed in the polymer electrolyte precursor solution. Figure 5 The image shown is a cross-sectional scanning electron microscope image, which shows a uniform thickness of approximately 20 μm for the test sample.

[0056] like Figure 6 As shown in the test results of the assembled SS / / SS battery, the ionic conductivity gradually increases with increasing temperature. Higher temperatures lead to more vigorous movement of polymer molecular chains, an increased proportion of amorphous regions, and more unobstructed ion migration channels, thus promoting lithium-ion migration. The composite solid electrolyte membrane containing Zn-ddmb exhibits higher ionic conductivity at all temperatures; specifically, at 35 °C, Zn-ddmb-20 exhibits a high conductivity of 0.000626 S / cm, while Zn-ddmb-0, Zn-ddmb-10, and Zn-ddmb-30 exhibit ionic conductivity of 0.0000829 S / cm, 0.000372 S / cm, and 0.0000276 S / cm, respectively.

[0057] like Figure 7 As shown, in the electrochemical stability window test, Zn-ddmb-20 exhibits a high electrochemical window of 4.52 V, indicating its potential as a high-voltage cathode material. The electrochemical windows of Zn-ddmb-0, Zn-ddmb-10, and Zn-ddmb-30 are 4.04 V, 4.13 V, and 4.38 V, respectively, all lower than those of Zn-ddmb-20. Figure 8 As shown, the lithium-ion transference number test results of Li / / Li symmetric cells show that the lithium-ion transference number of Zn-ddmb-20 is 0.67, which is higher than that of Zn-ddmb-0, Zn-ddmb-10 and Zn-ddmb-30, indicating that the introduction of an appropriate amount of Zn-ddmb helps to optimize the lithium-ion transport behavior in the composite solid electrolyte.

[0058] like Figure 9 As shown, the charge-discharge cycle results of the Li / / Li symmetric cell indicate that the battery using the Zn-ddmb-20 composite solid electrolyte membrane exhibits stable cycling for over 4000 h and maintains a low overpotential of approximately 0.04 V, demonstrating that the composite solid electrolyte membrane possesses good electrode / electrolyte interface stability.

[0059] like Figure 10As shown, under conditions of 25 °C and 1 C, the LFP / / Li battery assembled with a Zn-ddmb-20 composite solid electrolyte membrane can stably cycle 100 times, still maintaining a specific capacity of 143 mAh / g, with a capacity retention of 99.63% and a coulombic efficiency of 99.45%. In contrast, when the Zn-ddmb addition is too low, its effect on improving the lithium-ion transport environment is limited; when the Zn-ddmb addition is too high, the filler may accumulate locally, leading to an increase in interfacial impedance, thereby affecting the battery's cycle performance.

[0060] 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 claims of the present invention.

Claims

1. A polymer-based metal-organic framework composite solid electrolyte membrane, characterized in that, The invention comprises a polymer matrix, a lithium salt, and a metal-organic framework filler; the polymer matrix is ​​poly(vinylidene fluoride-hexafluoropropylene), the lithium salt is lithium bis(trifluoromethanesulfonylimide), and the metal-organic framework filler is Zn-ddmb, wherein the Zn-ddmb is dispersed in the polymer matrix; the Zn-ddmb is a metal-organic framework material formed by the coordination of zinc ions with 1,4-bis(5,6-dicarboxybenzimidazole-methyl)benzene.

2. The polymer-based metal-organic framework composite solid electrolyte membrane according to claim 1, characterized in that, The amount of Zn-ddmb added is 1% to 30% of the mass of poly(vinylidene fluoride-hexafluoropropylene).

3. The polymer-based metal-organic framework composite solid electrolyte membrane according to claim 2, characterized in that, The amount of Zn-ddmb added is 10% to 30% of the mass of poly(vinylidene fluoride-hexafluoropropylene), preferably 20%.

4. The polymer-based metal-organic framework composite solid electrolyte membrane according to claim 1, characterized in that, The mass ratio of poly(vinylidene fluoride-hexafluoropropylene) to lithium bis(trifluoromethanesulfonylimide) is 3:1, and the thickness of the composite solid electrolyte membrane is 20~40 μm.

5. A method for preparing a polymer-based metal-organic framework composite solid electrolyte membrane according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Dissolve zinc salt and 1,4-bis(5,6-dicarboxybenzimidazole-methyl)benzene in an organic solvent, add an acid regulator and heat to react, then cool, wash, filter and dry to obtain Zn-ddmb metal-organic framework filler; (2) Poly(vinylidene fluoride-hexafluoropropylene) and lithium bis(trifluoromethanesulfonylimide) were added to an organic solvent and heated and stirred to obtain a polymer electrolyte precursor solution; (3) Add the Zn-ddmb metal-organic framework filler obtained in step (1) to the polymer electrolyte precursor solution obtained in step (2), and continue heating and stirring to obtain the composite electrolyte precursor solution; (4) The composite electrolyte precursor solution obtained in step (3) is solution cast and dried under vacuum to obtain a polymer-based metal-organic framework filler composite solid electrolyte membrane.

6. The preparation method according to claim 5, characterized in that, In step (1), the zinc salt is ZnCl2, the organic solvent is a mixture of N,N-dimethylacetamide and acetonitrile, the acidity regulator is nitric acid, the heating reaction temperature is 60~100 ℃, and the reaction time is 72~144 h.

7. The preparation method according to claim 5, characterized in that, In steps (2) and (3), the organic solvent is N,N-dimethylformamide, the mass ratio of poly(vinylidene fluoride-hexafluoropropylene) to lithium bis(trifluoromethanesulfonylimide) is 3:1, and the amount of Zn-ddmb metal-organic framework filler added is 1% to 30% of the mass of poly(vinylidene fluoride-hexafluoropropylene).

8. The preparation method according to claim 5, characterized in that, In step (4), the vacuum drying temperature is 60~100 ℃ and the drying time is 8~24 h.

9. The application of the polymer-based metal-organic framework composite solid electrolyte membrane according to any one of claims 1 to 4 in a lithium battery, characterized in that, The composite solid electrolyte membrane is disposed between the positive and negative electrodes, serving as an ion transport medium and a separator; the lithium battery is a lithium metal battery.

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