Zn-Fe bimetallic MOFs material modified diaphragm and preparation method thereof

Abstract

The present invention belongs to the technical field of lithium-sulfur batteries, and specifically relates to a Zn-Fe bimetallic MOFs material modified diaphragm and a preparation method thereof. The invention comprises the following steps: preparing a MOFs material by a solvent thermal method using FeCl2·4H2O, 2,2'-bipyridine-5,5'-dicarboxylic acid, tetrazole, tetrapropylammonium hydroxide and zinc salt; preparing the MOFs material into a slurry; and obtaining a modified diaphragm by scraping and drying. The present invention is suitable for use in high temperature or corrosive environments, has high purity of MOFs, low production cost and simple preparation process. The prepared diaphragm can effectively induce the transmission of lithium ions and can also adsorb LiPS. The high catalytic active sites accelerate the kinetics of the redox reaction and promote the reaction. The specific capacity of the first cycle can reach 1587.6 mAh·g at a rated capacitance of 0.1 C. ‑1 The specific capacity after 70 cycles is 695.3 mAh·g ‑1 , the Coulombic efficiency is still close to 100%.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-sulfur batteries, and in particular relates to a Zn-Fe bimetallic MOFs material modified diaphragm and a preparation method thereof. Background Art

[0002] Lithium-sulfur batteries, as a promising energy storage system, have attracted much attention due to their high theoretical energy density and low cost. However, lithium-sulfur batteries face some challenges in practical applications, especially when the batteries operate in high temperatures or corrosive environments, these problems become more prominent. Traditional lithium-sulfur batteries are prone to performance degradation under high temperature conditions, mainly due to the aggravated sulfide shuttle effect, as well as the instability and corrosion of internal components of the battery. In addition, the metal organic framework (MOFs) materials used in existing lithium-sulfur battery technology are often limited by purity and performance, which directly affects the cycle stability and overall performance of the battery. At the same time, the synthesis cost of some MOFs materials is high and the preparation process is complicated, making it difficult to meet the needs of large-scale production and commercial applications.

[0003] The document with application number "No. 202410329533.8" discloses "A MOFs-derived Zn-Fe oxide heterojunction nanocomposite material and its application". Aminoterephthalic acid and FeCl3·6H2O are dissolved in dimethylformamide solution; ethanol solution is added dropwise to the above solution, mixed and transferred into a reactor, heated for reaction, centrifuged and washed, and dried to obtain a Fe-MOF precursor; the precursor and PVP are dissolved in methanol solution, mixed and added with Zn(NO3)2·6H2O and stirred evenly to obtain a precursor solution; terephthalic acid is dissolved in a dimethylformamide / dimethyl sulfoxide mixed solution; added dropwise to the precursor solution, transferred into a reactor for heating for reaction, and the white product is collected, centrifuged, washed, dried and annealed to obtain a MOFs-derived Fe-Zn oxide gas-sensitive material. The problems are: 1. Using aminoterephthalic acid as a ligand for constructing bimetallic MOFs limits the complexity of the MOFs' pore structure and the space for performance optimization. In addition, aminoterephthalic acid's insufficient chemical and thermal stability under extreme conditions makes MOFs unsuitable for use in high-temperature or corrosive environments. 2. During the synthesis process, precise coordination between the ligand and the metal node is required. Improper synthesis conditions can easily lead to the formation of byproducts or structural defects, which in turn affect the purity and performance of MOFs. 3. Complex synthesis steps are required, including precise control of pyrolysis conditions, which increases production costs and difficulty. Summary of the Invention

[0004] The purpose of the present invention is to prepare a Zn-Fe bimetallic MOFs material modified diaphragm to solve the problems of the prior art, such as unsuitability for application in high temperature or corrosive environments, affecting the purity and performance of MOFs, and high production cost and difficulty.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm, comprising the following steps:

[0006] Step 1: FeCl2·4H2O, 2,2'-bipyridine-5,5'-dicarboxylic acid and deionized water were mixed and stirred, filtered and washed to obtain a powder;

[0007] Step 2: Weigh the powder and tetrazole and dissolve them in N,N-dimethylacetamide. Stir the solution until uniform at room temperature. Then add tetrapropylammonium hydroxide and zinc salt and continue stirring until dissolved. React in a reactor, cool to room temperature, wash with N,N-dimethylacetamide, and dry to obtain Zn-Fe bimetallic MOFs material.

[0008] Step 3: Add the Zn-Fe bimetallic MOFs material, conductive carbon black, and binder into a glass bottle, mix well, and then add an appropriate amount of N-methyl-2-pyrrolidone solution and stir to form a uniform viscous slurry;

[0009] Step 4: Use anhydrous ethanol to clean the cut PP diaphragm, and use a scraping method to evenly apply the slurry obtained in step 3 on the PP diaphragm with a scraper. Vacuum dry the coated diaphragm to obtain a uniform modified diaphragm.

[0010] Furthermore, in the above step 1, the molar ratio of FeCl2·4H2O and 2,2'-bipyridine-5,5'-dicarboxylic acid is 1:1, and the stirring time is 24h to 60h.

[0011] Furthermore, in the above step 2, the zinc salt is zinc acetate, zinc nitrate or zinc chloride.

[0012] Furthermore, in the above step 2, the molar ratio of the powder, tetrazole, tetrapropylammonium hydroxide and zinc salt is 1:1:1:1,

[0013] Furthermore, in the above step 2, the reaction temperature is 100-140° C., and the reaction time is 48-72 h.

[0014] Furthermore, in the above step 3, the mass ratio of the Zn-Fe bimetallic MOFs material, the conductive carbon black and the binder is 50-90:5-25:5-25, and the stirring time is 9-15 hours.

[0015] Furthermore, the conductive carbon black in the above step 3 is Super P, Ketjen black or acetylene black; and the binder is carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE).

[0016] Furthermore, the vacuum drying in step 4 is carried out at a temperature of 40° C. to 70° C. and for a time of 5 to 8 hours.

[0017] Furthermore, the Zn-Fe bimetallic MOFs material modified diaphragm prepared by the above preparation method.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) Zn-Fe bimetallic MOFs material has a one-dimensional tubular columnar crystal structure: The present invention uses Zn-Fe bimetallic MOFs material to prepare a modified diaphragm. Zn-Fe bimetallic MOFs has a regular triangle and regular hexagonal double-channel nanoflower structure. The two independent channels can optimize the transmission paths of electrons and ions respectively, promote faster charge transfer and diffusion of lithium ions, avoid the formation of lithium dendrites, and improve the rate performance and charge and discharge speed of the battery. In addition, the double-channel structure provides more surface and internal sites, which can more effectively adsorb and fix polysulfides, reduce their dissolution and migration in the electrolyte, thereby greatly reducing the shuttle effect and improving the cycle stability and energy efficiency of the battery; its crystal skeleton has high porosity and large double channels, which is Li + The transport of lithium ions provides a uniform and orderly channel, which can effectively induce the transport of lithium ions and avoid Li + Agglomeration occurs to prevent the growth of negative electrode lithium dendrites.

[0020] (2) Zn-Fe bimetallic MOFs material has a double-channel crystal structure: Since the bipyridine structure can provide an additional conjugated π electron system, which helps to stabilize the entire molecular structure, the present invention selects 2,2'-bipyridine-5,5'-dicarboxylic acid and tetrazole to coordinate with metal ions to form a one-dimensional ordered double-channel nanoflower-shaped Zn-Fe bimetallic MOFs material. On the one hand, the larger pores can allow Li + On the other hand, the smaller pores can effectively block the shuttle of LiPS, especially medium to high-order LiPS (such as Li2S4-Li2S8), which can easily shuttle in traditional separators and cause battery capacity attenuation.

[0021] (3) Zn-Fe bimetallic MOFs materials have catalytic conversion function: by 2+ By precisely anchoring on 2,2'-bipyridine-5,5'-dicarboxylic acid, we successfully achieved Fe 2+ Precise positioning of Fe in Zn-Fe bimetallic MOFs materials 2+ and Zn 2+ Constitute bimetallic MOFs with abundant catalytic active sites, in which Fe 2+It has a strong catalytic effect on the conversion of LiPS and effectively captures and converts dissolved LiPS through physical adsorption, inhibiting the dissolution of LiPS and slowing down the shuttle effect. 2+ The introduction of further regulates the catalytic center and synergistically enhances the catalytic effect. It prevents LiPS from shuttling to the negative electrode, thereby protecting the lithium metal negative electrode, reducing capacity decay, and improving the cycle stability and efficiency of the battery.

[0022] (4) Due to its ordered dual-pore structure, the Zn-Fe bimetallic MOFs material can withstand a certain degree of thermal expansion without losing its integrity. The bimetallic combination of zinc and iron can optimize electron distribution, which helps to reduce local corrosion inside the battery. Therefore, the present invention is suitable for application in high-temperature or corrosive environments. Due to the use of higher-purity metal salts and ligands, the introduction of impurities can be reduced by optimizing the chemical structure and synthesis conditions, making the MOFs have higher purity, thereby significantly improving the purity of the material and enhancing the overall performance of the battery.

[0023] (5) The Zn-Fe bimetallic MOFs material provided by the present invention is prepared by a solvothermal method, which features mild reaction conditions, a simple preparation process, low production costs, and suitability for large-scale production. These characteristics make the material a potential candidate for significantly improving the applicability and economic efficiency of lithium-sulfur batteries in high-temperature and corrosive environments, opening up new avenues for the development of high-performance lithium-sulfur batteries in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a preparation flow chart of Example 1;

[0025] Figure 2 This is a morphology of the Zn-Fe bimetallic MOFs material prepared in Example 1 under an optical microscope;

[0026] Figure 3 This is a characterization diagram of the flexibility of the Zn-Fe bimetallic MOFs material modified diaphragm prepared in Example 1;

[0027] Figure 4 is a graph showing the relationship between current density and potential (CV) of the lithium-sulfur battery prepared in Example 1;

[0028] Figure 5 is the electrochemical impedance spectroscopy (EIS) of the lithium-sulfur battery prepared in Example 1;

[0029] Figure 6 1 is a rate performance diagram of the lithium-sulfur battery prepared in Example 1 at different currents;

[0030] Figure 7This is a graph showing the relationship between efficiency and specific capacity of the lithium-sulfur battery prepared in Example 1 after 70 cycles at a rated capacitance of 0.1C;

[0031] like Figure 8 It is the electrical conductivity of the lithium-sulfur battery prepared in Implementation Case 1-5 at room temperature. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to specific embodiments.

[0033] Example 1: See Figure 1 The preparation method of the Zn-Fe bimetallic MOFs material modified diaphragm comprises the following steps:

[0034] Step 1: Weigh 0.61 g of FeCl2·4H2O, 0.5 g of 2,2'-bipyridine-5,5'-dicarboxylic acid, and 50 mL of deionized water into a beaker and stir for 24 h. Filter the solution and wash with deionized water to obtain a pink powder.

[0035] Step 2: Weigh 0.172 g of powder and 0.04 g of tetrazole and dissolve them in 9 mL of N,N-dimethylacetamide. In a polytetrafluoroethylene reactor, stir the solution at room temperature until uniform. Then add 0.12 g of tetrapropylammonium hydroxide and 0.076 g of zinc acetate and continue stirring until dissolved. React in the reactor at 120°C for 2 days, cool to room temperature, wash three times with N,N-dimethylacetamide, and dry to obtain Zn-Fe bimetallic MOFs material;

[0036] Step 3: Weigh 0.07 g, 0.02 g, and 0.01 g of the Zn-Fe bimetallic MOFs material, conductive carbon black (SuperP), and binder (PVDF) obtained in step 2, respectively, and add them to a glass bottle, mix them evenly, and then add 1 mL of N-methyl-2-pyrrolidone solution and stir for 9 h to form a uniform viscous black slurry;

[0037] Step 4: Use anhydrous ethanol to clean the cut PP diaphragm, and use the scraping method to evenly scrape the black slurry obtained in step 3 on the surface of the PP diaphragm with a thickness of 75 μm. Transfer the coated diaphragm to a vacuum drying oven and dry it at 60°C for 12 hours to obtain a uniform black modified diaphragm.

[0038] Example 2: A method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm, comprising the following steps:

[0039] Step 1: Weigh 0.61 g of FeCl2·4H2O, 0.5 g of 2,2'-bipyridine-5,5'-dicarboxylic acid, and 50 mL of deionized water into a beaker and stir for 30 h. Filter the solution and wash with deionized water to obtain a pink powder.

[0040] Step 2: Weigh 0.172 g of powder and 0.04 g of tetrazole and dissolve them in 12 mL of N,N-dimethylacetamide. In a polytetrafluoroethylene reactor, stir the solution at room temperature until uniform. Then add 0.12 g of tetrapropylammonium hydroxide and 0.076 g of zinc acetate and continue stirring until dissolved. React in the reactor at 120°C for 2 days, cool to room temperature, wash three times with N,N-dimethylacetamide, and dry to obtain Zn-Fe bimetallic MOFs material;

[0041] Step 3: Weigh 0.08 g, 0.01 g, and 0.01 g of the Zn-Fe bimetallic MOFs material, conductive carbon black (SuperP), and binder (PVDF) obtained in step 2, respectively, and add them to a glass bottle, mix them evenly, and then add 1 mL of N-methyl-2-pyrrolidone solution and stir for 10 h to form a uniform viscous black slurry;

[0042] Step 4: Use anhydrous ethanol to clean the cut PP diaphragm, and use the scraping method to evenly scrape the black slurry obtained in step 3 on the surface of the PP diaphragm with a thickness of 75 μm. Transfer the coated diaphragm to a vacuum drying oven and dry it at 50°C for 12 hours to obtain a uniform black modified diaphragm.

[0043] Example 3: A method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm, comprising the following steps:

[0044] Step 1: Weigh 0.61 g of FeCl2·4H2O, 0.5 g of 2,2'-bipyridine-5,5'-dicarboxylic acid, and 50 mL of deionized water into a beaker and stir for 35 h. Filter the solution and wash with deionized water to obtain a pink powder.

[0045] Step 2: 0.172 g of powder and 0.04 g of tetrazole were dissolved in 9 mL of N,N-dimethylformamide. The solution was stirred at room temperature in a polytetrafluoroethylene reactor until uniform. 0.12 g of tetrapropylammonium hydroxide and 0.076 g of zinc acetate were added and continued to stir until dissolved. The mixture was reacted at 120°C in the reactor for 2 days, cooled to room temperature, washed three times with N,N-dimethylformamide, and dried to obtain a Zn-Fe bimetallic MOFs material.

[0046] Step 3: Weigh 0.07 g, 0.02 g, and 0.01 g of the Zn-Fe bimetallic MOFs material, conductive carbon black (Ketjen black), and binder (PVDF) obtained in step 2, respectively, and add them to a glass bottle, mix them evenly, and then add 1 mL of N-methyl-2-pyrrolidone solution and stir for 11 hours to form a uniform viscous black slurry;

[0047] Step 4: Use anhydrous ethanol to clean the cut PP diaphragm, and use the scraping method to evenly scrape the black slurry obtained in step 3 on the surface of the PP diaphragm with a thickness of 75 μm. Transfer the coated diaphragm to a vacuum drying oven and dry it at 60°C for 10 hours to obtain a uniform black modified diaphragm.

[0048] Example 4: A method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm, comprising the following steps:

[0049] Step 1: Weigh 0.61 g of FeCl2·4H2O, 0.5 g of 2,2'-bipyridine-5,5'-dicarboxylic acid, and 50 mL of deionized water into a beaker and stir for 24 h. Filter the solution and wash with deionized water to obtain a pink powder.

[0050] Step 2: Weigh 0.172 g of powder and 0.04 g of tetrazole and dissolve them in 9 mL of N,N-dimethylacetamide. In a polytetrafluoroethylene reactor, stir the solution at room temperature until uniform. Then add 0.12 g of tetrapropylammonium hydroxide and 0.076 g of zinc acetate and continue stirring until dissolved. React in the reactor at 120°C for 3 days, cool to room temperature, wash three times with N,N-dimethylacetamide, and dry to obtain Zn-Fe bimetallic MOFs material;

[0051] Step 3: Weigh 0.07 g, 0.02 g, and 0.01 g of the Zn-Fe bimetallic MOFs material, conductive carbon black (SuperP), and carboxymethyl cellulose (CMC) obtained in step 2, respectively, and add them to a glass bottle, mix them evenly, and then add 1 mL of N-methyl-2-pyrrolidone solution and stir for 9 h to form a uniform viscous black slurry;

[0052] Step 4: Use anhydrous ethanol to clean the cut PP diaphragm, and use the scraping method to evenly scrape the black slurry obtained in step 3 on the surface of the PP diaphragm with a thickness of 100 μm. Transfer the coated diaphragm to a vacuum drying oven and dry it at 70°C for 12 hours to obtain a uniform black modified diaphragm.

[0053] Example 5: A method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm, comprising the following steps:

[0054] Step 1: Weigh 0.61 g of FeCl2·4H2O, 0.5 g of 2,2'-bipyridine-5,5'-dicarboxylic acid, and 50 mL of deionized water into a beaker and stir for 50 h. Filter the solution and wash with deionized water to obtain a pink powder.

[0055] Step 2: Weigh 0.172 g of powder and 0.04 g of tetrazole and dissolve them in 9 mL of N,N-dimethylformamide. In a polytetrafluoroethylene reactor, stir the solution at room temperature until uniform. Then add 0.12 g of tetrapropylammonium hydroxide and 0.076 g of zinc acetate and continue stirring until dissolved. React in the reactor at 100 ° C for 3 days, cool to room temperature, wash three times with N,N-dimethylformamide, and dry to obtain Zn-Fe bimetallic MOFs material;

[0056] Step 3: Weigh 0.07 g, 0.02 g, and 0.01 g of the Zn-Fe bimetallic MOFs material, conductive carbon black (SuperP), and binder (PTFE) obtained in step 2, respectively, and add them to a glass bottle, mix them evenly, and then add 1 mL of N-methyl-2-pyrrolidone solution and stir for 15 h to form a uniform viscous black slurry;

[0057] Step 4: Use anhydrous ethanol to clean the cut PP diaphragm, and use the scraping method to evenly scrape the black slurry obtained in step 3 on the surface of the PP diaphragm with a thickness of 75 μm. Transfer the coated diaphragm to a vacuum drying oven and dry it at 40°C for 12 hours to obtain a uniform black modified diaphragm.

[0058] The modified diaphragm obtained in Examples 1-5 above was taken out and cut into a circle with a diameter of 18 mm with a punch to obtain a modified battery separator; the battery separator E was assembled with a sulfur-loaded graphene composite positive electrode material and a lithium sheet of negative electrode material in an argon-filled glove box with a shrapnel and a gasket to form a lithium-sulfur battery, and the rate performance (0.1C, 0.3C, 0.5C, 1C, 2C, 3C current), impedance (frequency 0.01-1000000 Hz), CV (1.6V-2.8V, scan rate 0.0005V / s), and conductivity were tested at different currents.

[0059] See also Figure 2 The morphology of the Zn-Fe bimetallic MOFs membrane material obtained in Example 1 is dumbbell-shaped.

[0060] See also Figure 3 By folding the membrane twice and then restoring it, it was found that no slurry fell off the surface of the membrane, indicating that the Zn-Fe bimetallic MOFs material membrane obtained in Example 1 has good flexibility.

[0061] like Figure 4As shown in the figure, the relationship between current density and potential of the lithium-sulfur battery assembled with the modified diaphragm of Zn-Fe bimetallic MOFs material at a scan rate of 0.0005V / s. It can be seen from the figure that it has obvious redox peaks (I, II and III), showing the redox reaction of sulfur during the charge and discharge process of the material. Peak I shows that S8 is reduced to Li2S6, peak II shows that Li2S6 is reduced to generate Li2S2 / Li2S, and peak III shows that Li2S2 / Li2S is oxidized to S8, indicating that the material has excellent catalytic performance and can accelerate the catalytic conversion of LiPS

[0062] like Figure 5 Figure 2 shows the electrochemical impedance spectroscopy (EI) of a lithium-sulfur battery assembled with a Zn-Fe bimetallic MOFs material-modified separator. The impedance curve consists primarily of two components. In the high-frequency region, the impedance curve corresponding to this high-frequency region on the complex plane is a semicircle. The smaller radius of the semicircle indicates lower electrode polarization impedance, allowing for rapid electron / ion transfer to achieve interfacial LiPS conversion.

[0063] like Figure 6 The figure shows the rate of the lithium-sulfur battery assembled with the Zn-Fe bimetallic MOFs material modified diaphragm of the present invention. The rate diagram can be used to obtain the battery specific capacity of the lithium-sulfur battery at different currents. The specific capacities at 0.1C, 0.3C, 0.5C, 1C, and 3C are 1166.1 mAh g -1 、751.1mAh g -1 、649.5mAh g -1 , 509.2mAh g -1 、397.9mAh g -1 , 321.6mAh g -1 .

[0064] like Figure 7 As shown in the figure, the specific capacity long cycle diagram of the lithium-sulfur battery assembled with the Zn-Fe bimetallic MOFs material modified diaphragm of the present invention, the first cycle specific capacity can reach 1587.6 mAh g at 0.1C -1 After 70 cycles, the specific capacity is 695.3 mAh g -1 , the Coulombic efficiency is still close to 100%.

[0065] like Figure 8 The following table shows the room temperature conductivity of lithium-sulfur batteries assembled with Zn-Fe bimetallic MOFs modified diaphragms under different examples of the present invention. The conductivity of Example 1 is 2.304 mS·cm -1 The conductivity of Example 2 is 1.414 mS·cm -1 The conductivity of Example 3 is 1.387 mS·cm -1The conductivity of Example 4 is 0.955 mS·cm -1 The conductivity of Example 5 is 0.662 mS·cm -1 .

[0066] In summary, embodiment 1 is the best embodiment.

[0067] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm, characterized in that: The following steps are involved: Step 1: FeCl2·4H2O, 2,2'-bipyridine-5,5'-dicarboxylic acid and deionized water were mixed and stirred, filtered and washed to obtain a powder; Step 2: Weigh the powder and tetrazole and dissolve them in N,N-dimethylacetamide. Stir the solution until uniform at room temperature. Then add tetrapropylammonium hydroxide and zinc salt and continue stirring until dissolved. React in a reactor, cool to room temperature, wash with N,N-dimethylacetamide, and dry to obtain Zn-Fe bimetallic MOFs material. Step 3: Add the Zn-Fe bimetallic MOFs material, conductive carbon black, and binder into a glass bottle, mix well, and then add an appropriate amount of N-methyl-2-pyrrolidone solution and stir to form a uniform viscous slurry; Step 4: Use anhydrous ethanol to clean the cut PP diaphragm, and use a scraping method to evenly apply the slurry obtained in step 3 on the PP diaphragm with a scraper. Vacuum dry the coated diaphragm to obtain a uniform modified diaphragm.

2. The method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm according to claim 1, characterized in that: In the step 1, the molar ratio of FeCl2·4H2O to 2,2'-bipyridine-5,5'-dicarboxylic acid is 1:1, and the stirring time is 24 h to 60 h.

3. The method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm according to claim 2, characterized in that: In the step 2, the zinc salt is zinc acetate, zinc nitrate or zinc chloride.

4. The method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm according to claim 3, characterized in that: In the step 2, the molar ratio of the powder, tetrazole, tetrapropylammonium hydroxide and zinc salt is 1:1:1:

1.

5. The method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm according to claim 4, characterized in that: In the step 2, the reaction temperature is 100-140° C., and the reaction time is 48-72 hours.

6. The method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm according to claim 5, characterized in that: In the step 3, the mass ratio of the Zn-Fe bimetallic MOFs material, the conductive carbon black and the binder is 50-90:5-25:5-25, and the stirring time is 9-15 hours.

7. The method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm according to claim 6, characterized in that: The conductive carbon black in step 3 is Super P, Ketjen black or acetylene black; the binder is carboxymethyl cellulose, polyvinylidene fluoride or polytetrafluoroethylene.

8. The method for preparing a Zn-Fe bimetallic MOFs material modified diaphragm according to claim 7, characterized in that: The vacuum drying in step 4 is performed at a temperature of 40° C. to 70° C. and for a time of 5 to 8 hours.

9. A Zn-Fe bimetallic MOFs material modified diaphragm prepared according to the preparation method of claim 1.

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