Solid electrolyte membrane of bimetal MOFs composite lithium ion sieve as well as preparation method and application of solid electrolyte membrane

Abstract

The invention discloses a solid electrolyte membrane of a bimetal MOFs composite lithium ion sieve and a preparation method and application of the solid electrolyte membrane. The preparation method of the electrolyte membrane comprises the following steps: dispersing a bimetallic MOFs material, a phenylphosphinic acid modified lithium titanate molecular sieve and a lithium salt in a solvent, adding a polymer material, and mixing and stirring to obtain mixed slurry; and pouring the mixed slurry into a container paved with a polytetrafluoroethylene film, and volatilizing the solvent to obtain the coating. The composite solid-state electrolyte membrane has good ionic conductivity, good toughness and good mechanical properties, and can improve the cycle performance and rate capability of a battery when applied to the solid-state battery. The preparation method is simple, low in cost and suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to a solid electrolyte membrane, in particular to a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane, and also to a preparation method and application thereof, belonging to the technical field of solid electrolytes. Background Art

[0002] Currently, the world faces the challenges of fossil energy depletion and environmental pollution. The use of green and sustainable renewable energy and the development of new energy storage technologies have become key development strategies for countries around the world. Consequently, lithium-ion batteries have gradually become part of people's lives and are now widely used in mobile phones, electric vehicles, and other applications. However, traditional liquid batteries contain flammable organic electrolytes, which are easily exposed to external forces and can cause leakage, leading to frequent safety incidents such as fires and combustion. Furthermore, the theoretical capacity of traditional liquid batteries has reached its upper limit, making them unable to meet the growing demand for lithium-ion batteries. To enhance the future application of lithium-ion batteries, the replacement of traditional liquid electrolytes with all-solid-state electrolytes is being considered. These assembled all-solid-state lithium-ion batteries offer high theoretical energy density and are non-flammable, non-corrosive, non-volatile, and leak-proof, reducing the risk of spontaneous combustion and explosion, significantly improving safety performance. These batteries have attracted considerable attention from researchers and related companies. However, all-solid-state electrolytes still face numerous challenges, such as low ionic conductivity, a narrow electrochemical window, poor compatibility with electrode materials, and interfacial stability, hindering their commercial application and industrial production.

[0003] At present, solid electrolytes can be roughly divided into two types: inorganic ceramic electrolytes and polymer solid electrolytes. The ionic conductivity of inorganic ceramic electrolytes at room temperature is usually around 10 -4 -10 -3 S cm -1 range. However, the interface contact between the inorganic ceramic electrolyte and the electrode is poor, resulting in a large interface resistance. In contrast, the use of polymer solid electrolytes can solve the problem of interface resistance very well. Its electrode wettability is good and close interface contact can be achieved. However, the ionic conductivity of polymer solid electrolytes is low, which greatly limits its application in solid-state batteries. Adding metal-organic framework materials (MOFs) to existing polymer solid electrolytes to obtain composite solid electrolytes can improve lithium ion conductivity, but there are problems such as small specific surface area and poor compatibility with lithium salts. Therefore, the development of solid electrolytes with high ionic conductivity, good interface stability, wide electrochemical window and good compatibility is of great significance to the industrialization promotion of solid-state lithium-ion batteries. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the first object of the present invention is to provide a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane. The composite electrolyte membrane has high ionic conductivity, good mechanical properties, and excellent electrochemical performance.

[0005] The second object of the present invention is to provide a method for preparing a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane. The method is simple, easy to operate, low-cost, and suitable for industrial production.

[0006] The third object of the present invention is to provide an application of a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane. When used in a lithium battery, the electrolyte membrane can greatly improve the battery's rate performance and cycle stability.

[0007] In order to achieve the above technical objectives, the present invention provides a method for preparing a solid electrolyte membrane of a bimetallic MOFs composite lithium ion sieve, which comprises: dispersing a bimetallic MOFs material, a lithium titanate molecular sieve modified with phenylphosphinic acid, and a lithium salt in a solvent, then adding a polymer material and mixing and stirring to obtain a mixed slurry; pouring the mixed slurry into a container covered with a polytetrafluoroethylene membrane, and volatilizing the solvent to obtain the membrane.

[0008] The present invention adds bimetallic MOFs materials and lithium ion sieve materials into polymer solid electrolytes to effectively reduce the glass transition temperature of the polymer and increase the active area of ​​lithium ions. The synergistic effect of the two metals in bimetallic MOFs can improve the conductivity and catalytic activity of the material by adjusting the electronic structure. The microporous / mesoporous structure (0.5~2 nm) of the bimetallic is Li + It provides a three-dimensional ion diffusion channel, shortening the lithium ion migration path. At the same time, the phenylphosphinic acid-modified lithium titanate molecular sieve adopts a ternary structure design of spinel substrate-mesoporous channel-functionalized surface. The phenylphosphinic acid in the lithium ion sieve combines with the hydroxyl groups on the lithium titanate surface through a condensation reaction, forming a stable PO-Ti bond on the basis of the lithium titanate structure and forming a new pore structure. This pore structure is conducive to the adsorption of anions in the lithium salt in the pores, achieving efficient lithium ion transport. In the composite solid electrolyte, the macroscopic pore screening of MOFs is combined with the chemical recognition of the phosphinic acid group to form a dual-effect pathway of "pore screening + coordination transport", which significantly improves the lithium ion flux, increases the activity space of lithium ions and the concentration of free lithium ions in the system, thereby effectively improving the ionic conductivity of the solid electrolyte.

[0009] In addition, the electrolyte membrane in the present invention is cast on the polytetrafluoroethylene membrane, which is conducive to the separation and preservation of the electrolyte membrane and can prevent damage to the electrolyte membrane.

[0010] As a preferred solution, the mass ratio of the bimetallic MOFs material to the phenylphosphinic acid-modified lithium titanate molecular sieve is 1 to 10:1, and more preferably 1 to 5:1. Controlling the mass of the bimetallic MOFs material and the lithium ion sieve material within an appropriate range is beneficial to improving the overall performance of the electrolyte membrane. When the proportion of MOFs is too high, the porous structure of MOFs may occupy too much volume, resulting in the active sites of the lithium ion sieve being covered and the ion screening efficiency being reduced. When the proportion of MOFs is too low, a continuous electron conduction network cannot be formed, the interface polarization increases, and the high-rate performance of the electrolyte membrane is affected.

[0011] As a preferred embodiment, the bimetallic MOFs material includes at least one of Cu-Al bimetallic MOFs, Cu-Mg bimetallic MOFs, Cu-Zn bimetallic MOFs, Cu-Fe bimetallic MOFs, and Cu-Co bimetallic MOFs. Because bimetallic MOFs contain two metal active sites, this helps improve the stability of the material's skeleton structure. The diversity of metal centers can enhance the thermal and chemical stability of MOFs, enabling their application under a wider range of conditions. The diameter of the hollow tubes and pore size of the material can be precisely controlled. The prepared materials have a large specific surface area and high electrical conductivity, exhibiting excellent electrochemical performance.

[0012] As a preferred solution, the lithium ion sieve material is a lithium titanate ion sieve modified with phenylphosphinic acid.

[0013] As a preferred solution, the above-mentioned material includes at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2) and lithium bis(fluorosulfonyl)imide (LiFSI, LiN(SO2F)2).

[0014] As a preferred solution, the mass ratio of the lithium salt to the polymer material is 1:2~15. Controlling the mass ratio of the lithium salt to the polymer material within an appropriate range is beneficial to improving the comprehensive performance of the electrolyte membrane. Within a certain range, increasing the amount of lithium salt added can increase the amorphous region inside the polymer material (such as polyethylene oxide PEO), thereby improving the mobility and conductivity of lithium ions. For example, when the mass ratio of PEO to Li is 13:1, the ether oxygen unit in PEO has a polymer chain flexibility, which is conducive to the transmission of Li +. The addition of LiTFSI will reduce the internal crystalline area of ​​PEO and increase the amorphous area inside PEO, which helps to improve the hopping transmission of lithium ions on the polyether chain, thereby improving the conductivity. In addition, the mass ratio of polymer material to lithium salt will also affect the mechanical properties and flexibility of the composite electrolyte. A suitable mass ratio can obtain a uniform composite electrolyte film with good flexibility. When the mass ratio of the two is not appropriate, the flexibility of the membrane will deteriorate and cracks will appear. For example, excessive use of lithium salt may cause the aggregation of metal MOFs and lithium ion sieve materials in the composite solid electrolyte, and gaps will appear between the particles, which will affect the flexibility of the membrane.

[0015] As a preferred embodiment, the polymer material includes at least one of polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF). More preferably, the polymer material is polyethylene oxide. The molecular weight of the polyethylene oxide is 100,000 to 1,000,000.

[0016] As a preferred solution, the mass ratio of the polymer material to the bimetallic MOFs material is 5-20:1. When too much MOFs is added, the polymer matrix cannot effectively encapsulate the filler, resulting in holes or uneven thickness in the electrolyte membrane. When too little MOFs is added, an effective transport network cannot be formed, resulting in limited performance improvement.

[0017] As a preferred embodiment, the mixing temperature is 30-60°C for 6-12 hours. Controlling the mixing temperature within a suitable range is beneficial to improving the interfacial stability of the composite solid electrolyte. During the mixing process, within a certain temperature range, the increase in temperature is conducive to sufficient interface contact between the polymer solid electrolyte and the lithium ion sieve and the bimetallic MOFs, thereby reducing the interfacial resistance.

[0018] The present invention also provides a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane, prepared by the above method. The prepared composite solid electrolyte membrane exhibits excellent electrochemical and mechanical properties, including a tensile strength of 6.5 MPa, a maximum strain of 1000%, and an electrochemical window of 4.95 V.

[0019] As a preferred solution, the mass content of the bimetallic MOFs material in the solid electrolyte membrane is 1-20 wt%.

[0020] As a preferred solution, the mass content of the lithium ion sieve material in the solid electrolyte membrane is 2-8 wt%.

[0021] As a preferred solution, the thickness of the solid electrolyte membrane is 2-300 μm.

[0022] The present invention also provides an application of a solid-state electrolyte membrane composed of a bimetallic MOF composite lithium ion sieve for use in preparing lithium batteries. The solid-state battery prepared using this electrolyte membrane exhibits excellent cycling and rate performance. The lithium ion sieve and bimetallic MOFs form a stable interface with the polymer matrix and electrode materials, reducing interfacial resistance and improving battery cycling stability. The lithium ion sieve helps inhibit lithium dendrite growth by providing a uniform lithium ion flux and a high lithium ion transference number, thereby improving battery safety.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) By introducing bimetallic MOFs materials and lithium ion sieve materials into polymer solid electrolytes, the glass transition temperature of the polymer is effectively reduced and the active area of ​​lithium ions is increased. At the same time, the synergistic effect of the bimetallic ion composite lithium ion sieve in the bimetallic MOFs material opens more active sites and increases the concentration of free lithium ions. Through the special interface formed by bimetallic MOFs, lithium ion sieve materials and polymers, the transmission efficiency of lithium ions is improved, thereby improving the ionic conductivity.

[0025] (2) The prepared electrolyte membrane has excellent electrochemical performance, high toughness, safety and stability. When used in solid-state lithium batteries, it greatly improves the battery's rate performance and cycle stability;

[0026] (3) The preparation method is simple, the cost is low, and it is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The ionic conductivity of the composite solid electrolyte membrane prepared in Example 1 at different temperatures.

[0028] Figure 2 This is a graph showing the charge and discharge stability of the solid-state battery prepared in Example 1 after 100 cycles at a current density of 1C. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the embodiments.

[0030] Example 1

[0031] (1) Preparation of bimetallic MOFs material Cu-Al-BTC

[0032] Put 6mmol of trimesic acid reagent and 30mL of anhydrous ethanol into a 100mL beaker, place the beaker on a magnetic stirrer and mix and stir until dissolved; put 9mmol of copper nitrate trihydrate (Cu(NO3)2·3H2O), 1.5mmol of aluminum nitrate nonahydrate (Al(NO3)2·9H2O) and 30mL of ultrapure water into a 100mL beaker and stir until dissolved; after mixing and stirring the above two solutions for a certain period of time, transfer them to the reactor, and then react at 120°C for 24 hours. After cooling, collect the sample by centrifugation and wash it with anhydrous ethanol and ultrapure water. After washing, place it in a vacuum drying oven at 100°C and dry it for 12 hours. The obtained Cu-Al-BTC bimetallic MOFs material was characterized, and the scanning electron microscope image is shown as follows. Figure 1 As shown, the Cu-Al-BTC is a material with an octahedral structure.

[0033] (2) Preparation of phenylphosphinic acid modified Li2TiO3 lithium ion sieve

[0034] A tris (hydroxymethylaminomethane) (Tris) buffer solution was prepared and adjusted to pH 8.5. 1.5 g of phenylphosphinic acid (PA) was added to 100 mL of the Tris buffer solution, followed by the addition of 5 g of a lithium titanate (LTO) precursor to the PA solution. The mixture was slowly stirred at room temperature for 5 hours, filtered, and dried at 60°C for 24 hours to obtain the modified precursor material. Subsequently, the modified precursor was added to a 0.25 mol / L hydrochloric acid solution and shaken at 150 rpm at room temperature for 24 hours to partially release the lithium ions from the precursor, forming a structure with regular lithium vacancies. The product was filtered, washed with deionized water until neutral, and dried at 60°C for 24 hours to obtain a phenylphosphinic acid-modified lithium ion sieve.

[0035] (2) Preparation of composite solid electrolyte membrane

[0036] S1: In a glove box, 1.49 g of the Cu-Al-BTC material prepared above, 0.3 g of phenylphosphinic acid-modified Li2TiO3 lithium ion sieve, and 4 g of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) were dissolved in 200 mL of anhydrous acetonitrile and stirred for 2 h to obtain a first slurry.

[0037] S2: Add 9.2 g of polyethylene oxide (PEO) with a molecular weight of 600,000 to the first slurry and stir at 40° C. for 6 h until the PEO is completely dissolved and the slurry is uniform, thereby obtaining a second slurry;

[0038] S3: The second slurry is poured into a glass container lined with a polytetrafluoroethylene mold, allowed to stand at room temperature for 24 hours, and then dried in a vacuum drying oven at 50°C for 12 hours to obtain a Cu-Al-BTC bimetallic MOFs composite poly-12-crown ether-4-2-butenoic acid methyl ester lithium ion sieve modified composite solid electrolyte membrane. The content of Cu-Al-BTC in the composite solid electrolyte membrane is 10wt%, and the content of the lithium ion sieve material is 2wt%.

[0039] The solid electrolyte membrane was cut into 19 mm discs and assembled into a stainless steel symmetrical cell (blocked cell) to test the ionic conductivity of the solid electrolyte at different temperatures. The ionic conductivity at 30°C was 6.06×10 -5 S cm -1 The ionic conductivity at 60°C is 8.42×10 -4 S cm -1 ,like Figure 1 shown.

[0040] Assemble a solid-state battery with LiFePO4 as the positive electrode and lithium sheet as the negative electrode for charge and discharge cycle testing. The charge and discharge curves of 100 cycles are as follows: Figure 2 As shown, its first discharge capacity at 1C is 147.4 mAh g -1 The capacity retention rate after 100 cycles is as high as 91.9%, the coulombic efficiency is also maintained at around 99%, and the voltage of the charge and discharge curve remains stable, indicating that the lithium deposition and stripping performance in the battery is excellent, showing good cycle stability and capacity retention.

[0041] Example 2

[0042] A solid electrolyte membrane was prepared using the method of Example 1, except that the bimetallic MOFs material was a Cu-Co bimetallic MOFs material and the lithium salt was lithium bis(fluorosulfonyl)imide. The preparation process of the bimetallic MOFs material Cu-Co-BTC was as follows: 6 mmol of trimesic acid and 30 mL of anhydrous ethanol were placed in a 100 mL beaker and stirred on a magnetic stirrer until dissolved. 9 mmol of copper nitrate trihydrate (Cu(NO₃)₂·3H₂O), 1.5 mmol of aluminum nitrate nonahydrate (Co(NO₃)₂·6H₂O), and 30 mL of ultrapure water were placed in a 100 mL beaker and stirred until dissolved. The two solutions were mixed and stirred for a predetermined period of time, then transferred to a reactor and reacted at 120°C for 24 hours. After cooling, the sample was collected by centrifugation and rinsed with anhydrous ethanol and ultrapure water. After rinsing, the sample was dried in a vacuum drying oven at 100°C for 12 hours.

[0043] Among them, the content of Cu-Al-BTC in the composite solid electrolyte membrane is 10wt%, and the content of lithium ion sieve is 2wt%.

[0044] The composite solid electrolyte membrane was assembled into a blocking cell and a half-cell according to the method described in Example 1, and its ionic conductivity was tested. See Table 1 for details.

[0045] Example 3

[0046] A solid electrolyte membrane was prepared using the method of Example 1, except that the bimetallic MOFs material was a Cu-Zn bimetallic MOFs material. The bimetallic MOFs material, Cu-Zn-BTC, was prepared as follows: 6 mmol of trimesic acid and 30 mL of anhydrous ethanol were placed in a 100 mL beaker and stirred on a magnetic stirrer until dissolved. 9 mmol of copper nitrate trihydrate (Cu(NO3)2·3H2O), 1.5 mmol of aluminum nitrate nonahydrate (Zn(NO3)2·6H2O), and 30 mL of ultrapure water were placed in a 100 mL beaker and stirred until dissolved. The two solutions were mixed and stirred for a predetermined period of time, then transferred to a reactor, reacted at 120°C for 24 hours, cooled, centrifuged, and washed with anhydrous ethanol and ultrapure water. After washing, the sample was dried in a vacuum drying oven at 100°C for 12 hours.

[0047] Among them, the content of Cu-Al-BTC in the composite solid electrolyte membrane is 10wt%, and the content of lithium ion sieve is 2wt%.

[0048] The solid electrolyte membrane was assembled into a blocking cell and a half-cell according to the method described in Example 1, and its ionic conductivity was tested. See Table 1 for details.

[0049] Example 4

[0050] A solid electrolyte membrane was prepared using the method of Example 1, except that the mass ratio of Cu-Al-BTC to phenylphosphinic acid-modified Li2TiO3 lithium ion sieve was controlled at 1:1, and the addition amount of both was 1.1 g. The Cu-Al-BTC content in the composite solid electrolyte membrane was 7 wt%, and the lithium ion sieve content was 7 wt%. This solid electrolyte membrane was assembled into a blocked cell and a half-cell according to the method of Example 1, and the ionic conductivity was measured, as shown in Table 1.

[0051] Example 5

[0052] A solid electrolyte membrane was prepared using the method of Example 1, except that the mass ratio of Cu-Al-BTC to phenylphosphinic acid-modified Li2TiO3 lithium ion sieve was controlled at 3:1 (Cu-Al-BTC weighed 1.52 g and the lithium ion sieve weighed 0.5 g). The Cu-Al-BTC content in the composite solid electrolyte membrane was 10 wt%, and the lithium ion sieve content was 3 wt%. This solid electrolyte membrane was assembled into a blocked cell and a half-cell according to the method of Example 1, and the ionic conductivity was measured. See Table 1 for details.

[0053] Comparative Example 1

[0054] The solid electrolyte membrane was prepared by the method of Example 1, except that the bimetallic MOFs material was changed to a Cu-based monometallic MOFs material (HKUST-1).

[0055] The Cu-based single-metallic MOFs material (HKUST-1) was prepared by dissolving 3.93 g of Cu(NO₃)₂·3H₂O and 2.00 g of polyvinylpyrrolidone (PVP K30) in 250 ml of methanol to obtain solution A. Then, 2.15 g of 1,3,5-trihexanoic acid (H₃BTC) was dissolved in 250 ml of methanol to obtain solution B. Solution B was added dropwise to solution A and stored at room temperature for 24 hours. The resulting blue HKUST-1 product was collected by centrifugation, washed three times with methanol, and dried at 60°C to obtain the Cu-based single-metallic MOFs material (HKUST-1).

[0056] In this comparative example, the Cu-Al-BTC content in the composite solid electrolyte membrane was 10 wt %, and the lithium ion sieve content was 2 wt %. This solid electrolyte membrane was assembled into a blocked cell and a half-cell according to the method described in Example 1, and the ionic conductivity thereof was measured, as shown in Table 1.

[0057] Comparative Example 2

[0058] A solid electrolyte membrane was prepared using the method of Example 1, except that no lithium ion sieve was added. The Cu-Al-BTC content in the composite solid electrolyte membrane was 10 wt%, and the lithium ion sieve content was 0. This solid electrolyte membrane was assembled into a blocked cell and a half-cell according to the method described in Example 1, and its ionic conductivity was measured. See Table 1 for details.

[0059] Comparative Example 3

[0060] The solid electrolyte membrane was prepared by the method of Example 1, except that the lithium ion sieve was Li 1.6 Mn 1.6O4. The Cu-Al-BTC content in the composite solid electrolyte membrane was 10 wt%, and the lithium ion sieve content was 2 wt%. The resulting solid electrolyte membranes with different lithium ion sieves were assembled into blocked cells and half-cells according to the method described in Example 1. Their ionic conductivity and cycling performance with a LiFePO4 positive electrode were tested. The conductivity data are detailed in Table 1.

[0061] Comparative Example 4

[0062] A solid electrolyte membrane was prepared using the method of Example 1, except that the lithium ion sieve was Li2TiO3. The Cu-Al-BTC content in the composite solid electrolyte membrane was 10 wt%, and the lithium ion sieve content was 2 wt%. The resulting solid electrolyte membranes with different lithium ion sieves were assembled into blocked cells and half-cells according to the method described in Example 1. Their ionic conductivity and cycling performance with a LiFePO4 positive electrode were tested. The conductivity data are detailed in Table 1.

[0063]

[0064] As can be seen from the table, compared with the comparative example, the lithium titanate molecular sieve modified with bimetallic MOFs composite phenylphosphinic acid in the present invention can significantly improve the ionic conductivity of the electrolyte membrane and increase the lithium ion migration rate.

Claims

1. A method for preparing a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane, characterized in that: The bimetallic MOFs material, phenylphosphinic acid-modified lithium titanate molecular sieve and lithium salt are dispersed in a solvent, and then a polymer material is added and mixed to obtain a mixed slurry; the mixed slurry is poured into a container covered with a polytetrafluoroethylene film, and the solvent is evaporated to obtain the product.

2. The method for preparing a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane according to claim 1, characterized in that: The mass ratio of the bimetallic MOFs material to the lithium titanate molecular sieve modified with phenylphosphinic acid is 1 to 10:

1.

3. The method for preparing a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane according to claim 2, characterized in that: The mass ratio of the bimetallic MOFs material to the lithium titanate molecular sieve modified with phenylphosphinic acid is 1 to 5:

1.

4. The method for preparing a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane according to claim 1 or 2, characterized in that: The bimetallic MOFs material includes at least one of Cu-Al bimetallic MOFs, Cu-Mg bimetallic MOFs, Cu-Zn bimetallic MOFs, Cu-Fe bimetallic MOFs, and Cu-Co bimetallic MOFs.

5. The method for preparing a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane according to claim 1, characterized in that: The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide; The mass ratio of the lithium salt to the polymer material is 1:2-15.

6. The method for preparing a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane according to claim 1 or 5, characterized in that: The polymer material includes at least one of polyethylene oxide, polyvinyl alcohol, polyacrylonitrile, and polyvinylidene fluoride; The mass ratio of the polymer material to the bimetallic MOFs material is 5-20:

1.

7. The method for preparing a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane according to claim 1, characterized in that: The mixing temperature is 30-60°C and the time is 6-12 hours.

8. A bimetallic MOFs composite lithium ion sieve solid electrolyte membrane, characterized by: Prepared by the method according to any one of claims 1 to 7.

9. The bimetallic MOFs composite lithium ion sieve solid electrolyte membrane according to claim 8, characterized in that: The mass content of the bimetallic MOFs material in the solid electrolyte membrane is 1-20 wt %; the mass content of the lithium ion sieve material in the solid electrolyte membrane is 2-8 wt %.

10. The use of a bimetallic MOFs composite lithium ion sieve solid electrolyte membrane according to claim 8 or 9, characterized in that: Used to prepare lithium batteries.

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