Preparation method of composite integrated membrane electrode based on NiFe-LDH and Fe-NC

Abstract

The invention relates to the technical field of electrochemical energy storage, and discloses a preparation method of a composite integrated membrane electrode based on N iFe-LDH and Fe-NC, and the preparation method comprises the following steps: A, sequentially generating N iFe-LDH and Fe-NC on a nickel net; b, adsorbing Fe-NC on the N iFe-LDH through Van der Waals' force; c, the nickel net and the waterproof breathable film are compounded to form an integrated structure; and D, the compounded nickel net is subjected to pressure treatment, Fe-NC and NiFe-LDH are tightly combined, so that the stability and conductivity of the electrode in the subsequent use process are ensured, in the step A, the size of the nickel net is 20 mm * 50-60 mm * 0.2-0.4 mm, and after ultrasonic washing is conducted for 20-40 min through methyl alcohol, ethyl alcohol and deionized water, vacuum drying is conducted for standby application, so that impurities and grease on the surface of the nickel net are removed. NiFe-LDH and Fe-NC are sequentially generated on a nickel net, Fe-NC is adsorbed on N iFe-LDH through Van der Waals force, and then the NiFe-LDH and the Fe-NC are tightly combined through pressure treatment, so that the integrated membrane electrode is formed. According to the structural design, the synergistic effect of NiFe-LDH and Fe-NC is fully utilized, and the catalytic activity and conductivity of the electrode are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to a method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC. Background Art

[0002] Zinc-air batteries, due to their high theoretical energy density (1350Wh / kg), environmental friendliness, and low cost, are considered an ideal candidate for next-generation energy storage technology. However, their commercialization has long been hampered by structural deficiencies in the air cathode. Traditional air cathodes utilize a multilayer stack design, typically comprising three to four separate components: a catalyst layer, a current collector, and a waterproof and breathable membrane. These layers are physically bonded together using adhesives. This discrete architecture presents multiple operational issues. First, interfacial impedance accumulation, with the presence of multi-layer solid-solid contact resistance, leads to significant energy loss during discharge. Second, the mass transfer path is lengthy, with oxygen having to sequentially penetrate the micropores of the waterproof and breathable layer, the pores of the current collector, and the interstices of the catalyst layer to reach the three-phase reaction interface. Furthermore, OH- ions must diffuse across hundreds of micrometers in the electrolyte, significantly reducing the efficiency of the oxygen reduction reaction. Third, the use of additives, such as binders and crosslinkers, not only blocks catalytic active sites (experiments have shown that this can result in a loss of active area by over 30%) but also reduces the overall conductivity of the electrode.

[0003] Existing improvement plans mostly focus on material optimization, such as the use of three-dimensional porous carbon-based composite electrodes to improve mass transfer efficiency. However, their preparation requires a complex template method and still relies on a multi-layer structure, but it still cannot eliminate the energy loss caused by physical contact between layers. Some studies have even tried to streamline the number of layers, such as integrating the current collector with the catalytic layer. However, the introduction of binders (usually accounting for 5-10wt%) causes the electrode porosity to drop by more than 30%, which in turn aggravates the mass transfer limitation. The root cause of the above technical bottleneck is that traditional designs are difficult to break through the dual shackles of "interlayer interface" and "additive dependence". Therefore, the development of an integrated membrane electrode with a streamlined structure, interface fusion, and no need for non-conductive additives has become a key breakthrough point for improving the performance of zinc-air batteries. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC, which solves the problems raised in the above background technology.

[0005] To achieve the above objectives, the present invention is implemented by the following technical solution: a preparation method based on NiFe-LDH and Fe-NC composite integrated membrane electrode, comprising the following steps:

[0006] A. Sequential generation of NiFe-LDH and Fe-NC on nickel mesh;

[0007] B. Fe-NC is adsorbed on NiFe-LDH via van der Waals forces;

[0008] C. Compound the nickel mesh with the waterproof and breathable membrane to form an integrated structure;

[0009] D. The composite nickel mesh is pressure treated to tightly bond the Fe-NC and NiFe-LDH to ensure the stability and conductivity of the electrode during subsequent use.

[0010] Preferably, in step A, the size of the nickel mesh is 20 mm × 50-60 mm × 0.2-0.4 mm. After ultrasonic washing with methanol, ethanol and deionized water for 20-40 minutes, the nickel mesh is vacuum dried for standby use to remove impurities and grease on the surface of the nickel mesh to ensure good adhesion of subsequent materials.

[0011] Preferably, in step A, when NiFe-LDH is generated on a nickel mesh by a hydrothermal method, the reactants include 0.8-0.9 g of Ni(NO3)2·6H2O, 0.2-0.25 g of Fe(NO3)3·9H2O, 2.3-2.5 g of urea and 0.5-0.6 g of ammonium fluoride, which are dissolved in 70-90 ml of deionized water and ultrasonically treated until dissolved to ensure the uniformity of the solution and sufficient dispersion of the reactants.

[0012] Preferably, in step A, the treated nickel mesh and the prepared solution are transferred to an 80-120 ml autoclave, heated in an oven to 130-150° C. for 10-14 hours, and then cooled to room temperature, the nickel mesh with changed color is collected, and surface impurities are washed with deionized water to remove unreacted precursors and by-products.

[0013] Preferably, in step A, the preparation method of Fe-NC is: dissolving 6-7g 2-methylimidazole, 1.7-2.0g Fe(acac)3 and 2.8-3.2g Zn(NO3)2·6H2O in 90-110ml methanol and stirring, standing at room temperature for 20-28h, the resulting product is centrifuged and washed two to four times with methanol, and vacuum dried at 55-65°C for 10-14h, and the Fe-containing ZIF-8 precursor is placed in a tube furnace and carbonized at 900-1050°C in an argon atmosphere for 2-4h to obtain Fe-NC powder to ensure high activity and good conductivity of Fe-NC.

[0014] Preferably, in step B, 0.18-0.22 g of Fe-NC is dispersed in 70-90 ml of deionized water under ultrasonic action for 50-70 min, the nickel mesh containing NiFe-LDH and the prepared solution are transferred to an 80-120 ml autoclave, heated in an oven to 130-150 ° C and kept warm for 10-14 h, cooled to room temperature and then washed with deionized water to obtain NiFe-LDH and Fe-NC loaded on the nickel mesh, so as to ensure uniform distribution and tight bonding of Fe-NC on the NiFe-LDH.

[0015] Preferably, in step C, the waterproof breathable membrane and the nickel mesh are composited using a double-roll machine, which can provide at least 40-60 tons of pressure and the gap is adjusted to 0.2-0.4 mm to ensure close fit and good contact performance between the waterproof breathable membrane and the nickel mesh.

[0016] Preferably, in step C, the waterproof and breathable membrane is made of polytetrafluoroethylene or polyvinylidene fluoride, has a thickness of 15-55 μm, and a pore size of 0.08-0.55 μm, to ensure smooth passage of oxygen and isolation of the electrolyte.

[0017] Preferably, in step D, the pressure treatment is performed in a press at a pressure of 8-22 MPa and a holding time of 8-35 min to ensure the firm adhesion of Fe-NC and NiFe-LDH on the nickel mesh and good electrical conductivity.

[0018] Preferably, the integrated membrane electrode is used as the positive electrode of a rechargeable zinc-air battery, the negative electrode of the zinc-air battery is a zinc plate, the electrolyte is 5.5-6.5M KOH + 0.15-0.25M ZnCl2 solution, and the electrolyte is 4-6mAcm -2 The charge and discharge test was carried out at a current density of 1000 nm, and the energy efficiency reached more than 65%.

[0019] The present invention provides a method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC. It has the following beneficial effects:

[0020] 1. The present invention sequentially generates NiFe-LDH and Fe-NC on a nickel mesh, adsorbs Fe-NC on NiFe-LDH through van der Waals forces, and then tightly combines the two through pressure treatment to form an integrated membrane electrode. This structural design fully utilizes the synergistic effect of NiFe-LDH and Fe-NC, significantly improving the catalytic activity and conductivity of the electrode. NiFe-LDH, as an efficient catalyst for oxygen reduction reaction and oxygen evolution reaction, is combined with Fe-NC with high conductivity and catalytic activity, so that the electrode exhibits excellent electrochemical performance in rechargeable zinc-air batteries. At 4-6 mA / cm 2When the charge and discharge test was carried out at a current density of , the energy efficiency reached more than 65%, which effectively improved the overall performance and cycle stability of the zinc-air battery and extended the battery life.

[0021] 2. The preparation method provided by the present invention is simple to operate, easy to control, and has low equipment requirements, making it suitable for large-scale production. During the preparation process, by optimizing the process parameters of each step, such as the ratio of reactants, reaction temperature, time, etc., the uniform distribution and tight bonding of Fe-NC on NiFe-LDH are ensured. At the same time, the preparation method of Fe-NC is simple and efficient. By carbonizing the Fe-containing ZIF-8 precursor in an argon atmosphere, Fe-NC powder with high activity and good conductivity is obtained. The entire preparation process does not require complex equipment and expensive raw materials, which reduces production costs and improves production efficiency.

[0022] 3. The present invention innovatively combines a nickel mesh with a waterproof and breathable membrane to form an integrated structure. The waterproof and breathable membrane is made of polytetrafluoroethylene or polyvinylidene fluoride, which has excellent waterproof and breathable properties. It can effectively isolate the electrolyte and prevent it from penetrating into the interior of the electrode, while allowing oxygen to pass smoothly, ensuring the normal operation of the electrode in the battery. In addition, the Fe-NC and NiFe-LDH are firmly attached to the nickel mesh through pressure treatment, which enhances the mechanical strength and conductivity of the electrode. This unique structural design not only improves the stability and durability of the electrode, but also simplifies the battery assembly process, reduces the contact resistance inside the battery, and improves the overall performance of the battery. In practical applications, this integrated membrane electrode can significantly improve the energy density and cycle life of zinc-air batteries, showing broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of the preparation process of the present invention;

[0024] Figure 2 It is a production step diagram of the present invention;

[0025] Figure 3 Schematic diagrams of the macroscopic and microscopic views of the integrated membrane electrode based on the NiFe-LDH / Fe-NC composite structure according to Example 1 of the present invention; 3a and 3b are front and back views of the integrated membrane electrode based on the NiFe-LDH / Fe-NC composite structure; Figure 3 c is the SEM image of the nickel mesh surface;

[0026] Figure 4 The electrochemical characterization results of the NiFe-LDH / Fe-NC composite structure integrated membrane electrode according to Example 1 of the present invention are shown in FIG. Figure 4 a is the ORR-LSV curve; Figure 4 b is the OER-LSV curve;

[0027] Figure 5 This is a power density diagram of the integrated membrane electrode based on the NiFe-LDH / Fe-NC composite structure according to Example 1 of the present invention;

[0028] Figure 6 This is the charge and discharge diagram of the integrated membrane electrode based on the NiFe-LDH / Fe-NC composite structure according to Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] Example 1:

[0031] Please see the attached Figure 1 -Attached Figure 6 , the embodiment of the present invention provides the following steps:

[0032] Take 20*55*0.3mm 3 A nickel mesh was then ultrasonically cleaned for 30 minutes using methanol, ethanol, and deionized water, respectively, before being vacuum-dried for later use. 0.8724g of Ni(NO3)2·6H2O, 0.2424g of Fe(NO3)3·9H2O, 2.4g of urea, and 0.592g of ammonium fluoride were dissolved in 80ml of deionized water and ultrasonically treated to fully dissolve them. The nickel mesh and the prepared solution were transferred to a 100ml autoclave and heated to 140°C in an oven for 12 hours. The mesh was then cooled to room temperature. The nickel mesh that had changed color (yellow-green) was collected and washed with deionized water to remove impurities that easily fell off the surface.

[0033] Specifically, the nickel mesh is pretreated by ultrasonically cleaning it with methanol, ethanol, and deionized water to remove impurities and grease from its surface, ensuring its cleanliness. This is followed by vacuum drying to completely remove moisture from the mesh, providing optimal conditions for subsequent material attachment.

[0034] Solution Preparation: Specific nitrates (Ni(NO3)2·6H2O and Fe(NO3)3·9H2O), urea, and ammonium fluoride are dissolved in deionized water to form a precursor solution for the hydrothermal reaction. These chemicals will react during the subsequent hydrothermal treatment to form NiFe-LDH.

[0035] Hydrothermal reaction: The pretreated nickel mesh and the prepared solution are placed in an autoclave. By controlling the temperature and time, NiFe-LDH grows on the nickel mesh. Hydrothermal reaction is a synthesis method carried out under high temperature and high pressure conditions, which helps to form materials with specific structures and properties.

[0036] Nickel mesh post-treatment: After the reaction is complete, cool to room temperature and collect the nickel mesh after the color change. The color change (yellow-green) may indicate the successful formation of NiFe-LDH. Rinse with deionized water to remove unreacted precursors and possible byproducts on the surface, thereby obtaining a relatively pure NiFe-LDH-coated nickel mesh.

[0037] 6.5g of 2-methylimidazole, 1.76g of Fe(acac)3, and 3g of Zn(NO3)2·6H2O were dissolved in 100ml of methanol, stirred, and allowed to stand at room temperature for 24 hours. The resulting product was washed three times with methanol by centrifugation and dried in vacuo at 60°C for 12 hours. The prepared Fe-containing ZIF-8 precursor was carbonized at 950°C in an argon atmosphere in a tube furnace for 3 hours to obtain Fe-NC powder. 0.2g of Fe-NC was dispersed in 80ml of deionized water under ultrasonication for 1 hour. The nickel mesh containing NiFe-LDH and the prepared solution were transferred to a 100ml autoclave. The mixture was heated to 140°C in an oven for 12 hours, then cooled to room temperature and rinsed with deionized water to obtain the NiFe-LDH and Fe-NC loaded on the nickel mesh.

[0038] Specifically, the solution is prepared and stirred: 2-methylimidazole, Fe(acac)3, and Zn(NO3)2·6H2O are dissolved in methanol and stirred. This step aims to thoroughly mix these compounds to form a homogeneous solution for synthesizing the Fe-containing ZIF-8 precursor. Once dissolved in methanol, 2-methylimidazole, Fe(acac)3, and Zn(NO3)2·6H2O interact to form the Fe-containing ZIF-8 precursor.

[0039] Standing and washing and drying: The solution was allowed to stand at room temperature for 24 hours to allow the precursor to fully form. Subsequently, unreacted impurities were removed by centrifugal washing with methanol and vacuum dried at 60°C for 12 hours to obtain a dry Fe-containing ZIF-8 precursor powder.

[0040] Carbonization: The resulting Fe-containing ZIF-8 precursor was placed in a tube furnace and heated to 950°C under argon for 3 hours. The carbonization process transforms the precursor into a highly active and conductive Fe-NC powder. High-temperature carbonization facilitates the formation of nitrogen-doped carbon materials with a porous structure and uniformly dispersed Fe active sites.

[0041] Dispersion and bonding of Fe-NC: Fe-NC powder is dispersed in deionized water under ultrasound to form a uniform dispersion. A nickel mesh containing NiFe-LDH is then mixed with this dispersion and heated to 140°C in an autoclave for 12 hours. This step allows the Fe-NC to adsorb to the NiFe-LDH surface via van der Waals forces, resulting in a tight bond between the Fe-NC and NiFe-LDH on the nickel mesh.

[0042] Post-treatment: Finally, the nickel mesh treated as above was cooled to room temperature and washed with deionized water to remove unbound Fe-NC and other impurities, thereby obtaining a composite material loaded with NiFe-LDH and Fe-NC on the nickel mesh.

[0043] The gap between the rollers, which can provide 50 tons of pressure, is adjusted to 0.3 mm, and the waterproof and breathable membrane and the nickel mesh are stacked together and passed through the rollers.

[0044] The integrated membrane electrode and zinc plate form a rechargeable zinc-air battery in 6MKOH+0.2MZnCl2 solution.

[0045] The macroscopic image of the integrated membrane electrode based on NiFe-LDH / Fe-NC composite structure prepared in this embodiment is shown in FIG. Figure 3 As shown in Figures 3a and 3b, it can be seen from the figure that the integrated membrane electrode is composed of a waterproof and breathable membrane and a nickel mesh loaded with catalyst.

[0046] The SEM image of the nickel mesh surface is as follows Figure 3 As shown in c, the flake-shaped NiFe-LDH and the regular dodecahedron-shaped Fe-NC (in the red circle) can be seen in the figure, which proves that this method can successfully load NiFe-LDH and Fe-NC on the nickel mesh.

[0047] ORR-LSV test was conducted on the integrated membrane electrode based on NiFe-LDH / Fe-NC composite structure. Figure 4 As shown in a, it can be seen from the figure that the half-wave potential of the integrated membrane electrode reaches 0.92V in 0.1MKOH solution, which is much higher than 0.84V of commercial Pt / C, proving that the membrane electrode has excellent ORR performance.

[0048] In the OER-LSV test of the integrated membrane electrode Figure 4 As shown in b, it can be seen from the figure that when the current density is 10mA / cm 2 The overpotential of the integrated membrane electrode in 0.1M KOH solution is 250mV, which is lower than the 360mV of commercial ruthenium dioxide. The integrated membrane electrode has an OER performance far higher than that of commercial catalysts.

[0049] The integrated membrane electrode was assembled into a rechargeable zinc-air battery for power density testing. Figure 5As shown, the power density of the integrated membrane electrode reaches 450mWcm -2 , which is much higher than the 150mWcm of commercial RuO2+Pt / C catalyst. -2 .

[0050] The integrated membrane electrode prepared in this example was assembled into a rechargeable zinc-air battery for testing. Figure 6 Shown in 6MKOH+0.2MZnCl2 solution and 5mAcm -2 In the charge-discharge cycle test at a current density of , the performance of the integrated membrane electrode did not show a significant decline within 100 hours. Calculations show that the energy efficiency of the integrated membrane electrode reached 68%, which is much higher than the energy efficiency of zinc-air batteries reported in other literature.

[0051] Example 2

[0052] Nickel mesh pretreatment: A nickel mesh with a size of 20 mm × 50 mm × 0.2 mm was ultrasonically cleaned with methanol, ethanol, and deionized water for 25 min, respectively, and then vacuum-dried for later use.

[0053] Preparation of NiFe-LDH: Weigh 0.8 g of Ni(NO₃)₂·6H₂O, 0.2 g of Fe(NO₃)₃·9H₂O, 2.3 g of urea, and 0.5 g of ammonium fluoride and dissolve in 70 ml of deionized water. Ultrasonicate until dissolved. Transfer the pretreated nickel mesh and solution to an 80 ml autoclave and heat in an oven to 130°C for 10 h. After cooling, collect the nickel mesh and wash it.

[0054] Preparation of Fe-NC: 6g of 2-methylimidazole, 1.7g of Fe(acac)3, and 2.8g of Zn(NO3)2·6H2O were dissolved in 90ml of methanol, stirred, and allowed to stand at room temperature for 20 hours. The product was washed twice by centrifugation with methanol and dried under vacuum at 55°C for 10 hours. The Fe-containing ZIF-8 precursor was carbonized at 900°C in an argon atmosphere for 2 hours to obtain Fe-NC powder.

[0055] Adsorption of Fe-NC: 0.18 g of Fe-NC was dispersed in 70 ml of deionized water for 50 min, mixed with the nickel mesh containing NiFe-LDH, and transferred to an 80 ml autoclave, heated to 130 °C and kept warm for 10 h, and then cooled and washed to obtain a composite nickel mesh.

[0056] Lamination and pressure treatment: The waterproof and breathable membrane and nickel mesh are laminated using a double-roller mill, applying 40 tons of pressure and adjusting the gap to 0.2 mm. The laminated nickel mesh is then pressurized in a press at 8 MPa for 8 minutes to form an integrated membrane electrode.

[0057] Example 3

[0058] Nickel mesh pretreatment: A nickel mesh with a size of 20 mm × 60 mm × 0.4 mm was ultrasonically cleaned with methanol, ethanol, and deionized water for 40 min, respectively, and then vacuum-dried for later use.

[0059] Preparation of NiFe-LDH: Weigh 0.9 g of Ni(NO₃)₂·6H₂O, 0.25 g of Fe(NO₃)₃·9H₂O, 2.5 g of urea, and 0.6 g of ammonium fluoride in 90 ml of deionized water and sonicate until dissolved. Transfer the pretreated nickel mesh and solution to a 120 ml autoclave and heat in an oven to 150°C for 14 h. After cooling, collect the nickel mesh and wash it.

[0060] Preparation of Fe-NC: 7g of 2-methylimidazole, 2.0g of Fe(acac)3, and 3.2g of Zn(NO3)2·6H2O were dissolved in 110ml of methanol, stirred, and allowed to stand at room temperature for 28 hours. The product was washed four times by centrifugation with methanol and dried under vacuum at 65°C for 14 hours. The Fe-containing ZIF-8 precursor was carbonized at 1050°C in an argon atmosphere for 4 hours to obtain Fe-NC powder.

[0061] Adsorption of Fe-NC: 0.22 g of Fe-NC was dispersed in 90 ml of deionized water for 70 min, mixed with the nickel mesh containing NiFe-LDH, and transferred to a 120 ml autoclave, heated to 150°C and kept warm for 14 h. After cooling and cleaning, the composite nickel mesh was obtained.

[0062] Lamination and pressure treatment: The waterproof and breathable membrane and nickel mesh are laminated using a double-roller mill, applying 60 tons of pressure and adjusting the gap to 0.4 mm. The laminated nickel mesh is then pressure-treated in a press at 22 MPa for 35 minutes to produce an integrated membrane electrode.

[0063] Test Case

[0064] ORR and OER performance testing

[0065] The NiFe-LDH and Fe-NC composite integrated membrane electrodes of Examples 1-3 were subjected to ultrasonication, and the powder removed by ultrasonication was collected and dried. Thereafter, ORR and OER activity tests were conducted in 0.1M KOH. The results are shown in Table 1 below:

[0066] Test items Half-wave potential (V) Overpotential (mV) Example 1 0.92 250 Example 2 0.89 260 Example 3 0.90 255

[0067] Table 1

[0068] Zinc-air battery performance test

[0069] The integrated membrane electrode of Examples 1-3 was assembled into an aluminum-air battery. The electrolyte used was 6MKOH+0.2MZnCl2. The current density was 5 mA cm-1 using a blue electric test system.-2 The charge and discharge test was carried out, and the results are shown in Table 2 below:

[0070]

[0071]

[0072] Table 2

[0073] Conclusion: By comparing the test data of Examples 1-3, it can be seen that the NiFe-LDH and Fe-NC composite integrated membrane electrode exhibits excellent performance under different process parameters. In the oxygen reduction reaction (ORR), the half-wave potential of Example 1 reaches 0.92V, showing the highest activity; in the oxygen evolution reaction (OER), the overpotential of Example 1 is only 250mV, showing good catalytic efficiency. In the zinc-air battery performance test, Example 1 performs well in power density, charge and discharge cycle time and energy efficiency, with a power density of 450mWcm -2 , the charge-discharge cycle time is up to 100 hours, and the energy efficiency is as high as 68%. In addition, Examples 2 and 3 also show relatively high performance indicators, indicating that the preparation method of the present invention has good stability and applicability, and can provide an efficient and stable membrane electrode for the positive electrode of rechargeable zinc-air batteries.

[0074] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC, characterized in that: The following steps are involved: A. Sequential generation of NiFe-LDH and Fe-NC on nickel mesh; B. Fe-NC is adsorbed on NiFe-LDH via van der Waals forces; C. Compound the nickel mesh with the waterproof and breathable membrane to form an integrated structure; D. The composite nickel mesh is pressure treated to tightly bond the Fe-NC and NiFe-LDH to ensure the stability and conductivity of the electrode during subsequent use.

2. The method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC according to claim 1, characterized in that: In step A, the size of the nickel mesh is 20 mm × 50-60 mm × 0.2-0.4 mm. After ultrasonic washing with methanol, ethanol and deionized water for 20-40 minutes, the mesh is vacuum dried for later use to remove impurities and grease on the surface of the nickel mesh to ensure good adhesion of subsequent materials.

3. The method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC according to claim 1, characterized in that: In step A, when NiFe-LDH is generated on a nickel mesh by a hydrothermal method, the reactants include 0.8-0.9 g of Ni(NO3)2·6H2O, 0.2-0.25 g of Fe(NO3)3·9H2O, 2.3-2.5 g of urea and 0.5-0.6 g of ammonium fluoride, which are dissolved in 70-90 ml of deionized water and ultrasonically treated until dissolved to ensure the uniformity of the solution and sufficient dispersion of the reactants.

4. The method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC according to claim 1, characterized in that: In step A, the treated nickel mesh and the prepared solution are transferred to an 80-120 ml autoclave, heated in an oven to 130-150° C. for 10-14 hours, and then cooled to room temperature before collecting the nickel mesh after color change. Surface impurities are washed with deionized water to remove unreacted precursors and by-products.

5. The method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC according to claim 1, characterized in that: In step A, the preparation method of Fe-NC is as follows: 6-7g 2-methylimidazole, 1.7-2.0g Fe(acac)3 and 2.8-3.2g Zn(NO3)2·6H2O are dissolved in 90-110ml methanol and stirred, and the mixture is allowed to stand at room temperature for 20-28h. The resulting product is centrifuged and washed two to four times with methanol, and vacuum dried at 55-65°C for 10-14h. The Fe-containing ZIF-8 precursor is placed in a tube furnace and carbonized at 900-1050°C in an argon atmosphere for 2-4h to obtain Fe-NC powder to ensure high activity and good conductivity of Fe-NC.

6. The method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC according to claim 1, characterized in that: In step B, 0.18-0.22 g of Fe-NC is dispersed in 70-90 ml of deionized water under ultrasonication for 50-70 minutes. The nickel mesh containing NiFe-LDH and the prepared solution are transferred to an 80-120 ml autoclave, heated in an oven to 130-150° C. for 10-14 hours, cooled to room temperature, and then rinsed with deionized water to obtain a nickel mesh loaded with NiFe-LDH and Fe-NC, thereby ensuring uniform distribution and tight bonding of the Fe-NC on the NiFe-LDH.

7. The method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC according to claim 1, characterized in that: In step C, the waterproof breathable membrane and the nickel mesh are laminated using a double-roller machine, which can provide at least 40-60 tons of pressure and adjust the gap to 0.2-0.4 mm to ensure close fit and good contact performance between the waterproof breathable membrane and the nickel mesh.

8. The method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC according to claim 1, characterized in that: In step C, the waterproof and breathable membrane is made of polytetrafluoroethylene or polyvinylidene fluoride, has a thickness of 15-55 μm, and a pore size of 0.08-0.55 μm, to ensure smooth passage of oxygen and isolation of the electrolyte.

9. The method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC according to claim 1, characterized in that: In the step D, the pressure treatment is performed in a press at a pressure of 8-22 MPa for a holding time of 8-35 min to ensure the strong adhesion of Fe-NC and NiFe-LDH on the nickel mesh and good electrical conductivity.

10. The method for preparing a composite integrated membrane electrode based on NiFe-LDH and Fe-NC according to claim 1, characterized in that: The integrated membrane electrode is used for the positive electrode of the rechargeable zinc-air battery, the negative electrode of the zinc-air battery is a zinc plate, the electrolyte is 5.5-6.5M KOH + 0.15-0.25M ZnCl2 solution, at 4-6mAcm -2 The charge and discharge test was carried out at a current density of 1000 nm, and the energy efficiency reached more than 65%.

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