Metal zinc negative electrode with PDMS (Polydimethylsiloxane)-coated MOF (Metal Organic Framework) composite coating and preparation method of metal zinc negative electrode

Abstract

The invention discloses a metal zinc negative electrode with a PDMS (at) MOF composite coating and a preparation method of the metal zinc negative electrode, and belongs to the technical field of aqueous zinc ion batteries. According to the technical scheme, the negative electrode comprises a metal zinc negative electrode and a PDMS (at) MOF composite coating arranged on the surface of the metal zinc negative electrode; the PDMS (at) MOF composite coating is of a composite structure formed by infiltrating and coating PDMS on the surface and pores of a metal organic framework (MOF). The negative electrode has the beneficial effects that the PDMS (at) MOF composite structure coating is constructed to synergistically inhibit zinc dendritic crystal growth and side reaction, so that the cycle life and the stability of the battery are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc-ion battery technology, specifically relating to a metallic zinc anode with a PDMS@MOF composite coating and its preparation method. Background Technology

[0002] With the widespread use of electronic devices, the performance requirements for rechargeable batteries are increasing. Currently, lithium-ion batteries are the most widely used in the world. However, their relatively low safety is a concern due to the potential for leakage of their organic electrolyte, which could lead to explosions. Lithium-ion batteries are currently the most commercially viable rechargeable battery and are widely used in various fields; however, they are expensive and pose certain risks. Aqueous zinc-ion batteries, on the other hand, are cheaper due to the high abundance of zinc in the Earth's crust, a more suitable redox potential (standard hydrogen electrode -0.76V vs.), and a higher theoretical capacity (820mAh g / g). -1 and 5855mAh cm -3 It has attracted researchers' attention due to its advantages such as [missing information - likely related to the characteristics of zinc-ion batteries]. Furthermore, the electrolyte in aqueous zinc-ion batteries (AZIBs) is generally a salt solution of water, thus offering high safety.

[0003] However, aqueous zinc-ion batteries also face several challenges. During deposition-stripping cycles, the growth of zinc dendrites can severely damage the battery; excessively long dendrites can puncture the separator, leading to short circuits. Hydrogen evolution also occurs during cycling, and the extra hydrogen gas produced can cause battery bulging. Zinc anode corrosion and the appearance of byproducts (basic zinc sulfate) also affect the overall battery performance and reduce coulombic efficiency. All these issues significantly impact the performance of zinc-ion batteries.

[0004] Researchers have proposed novel electrolyte development strategies, as well as optimization strategies such as negative electrode interface modification and membrane design. Introducing tranexamic acid (TXA) as an additive into the ZnSO4 electrolyte system optimizes the negative electrode / electrolyte interface (AEI) by preferentially adsorbing TXA molecules onto the zinc negative electrode interface. TXA molecules induce Zn... 2+ Preferential growth along the Zn(002) crystal plane restricts the growth of two-dimensional Zn 2+ This diffusion and mitigation of zinc dendrite formation; for example, Tao et al. constructed a hydrophobic protective coating by simply coating the zinc anode with hydrophobic perfluoropolyether (PFPE), which promoted the diffusion of Zn. 2+ The diffusion effectively prevents water molecules from directly contacting the zinc anode, suppressing side reactions. Furthermore, a ZnF2 layer is formed in situ on the zinc layer, improving cycle stability and reversibility.

[0005] However, the existing technologies still have limitations: while a single hydrophobic coating can block moisture to some extent, it may create an ion transport bottleneck, leading to increased polarization, and its ability to regulate zinc ion deposition behavior is limited, making it difficult to simultaneously suppress dendrites and side reactions. Therefore, in-depth research into the microscopic mechanisms of the zinc anode / electrolyte interface and the development of novel interface modification layers with tunable properties are of great significance for enhancing interface stability and improving the long-cycle performance of zinc-ion batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a zinc anode with a PDMS@MOF composite coating and its preparation method. This anode, by constructing a composite structure coating, synergistically suppresses zinc dendrite growth and side reactions, significantly improving the cycle life and stability of the battery.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a zinc metal anode with a PDMS@MOF composite coating, comprising a zinc metal anode and a PDMS@MOF composite coating disposed on the surface of the zinc metal anode; the PDMS@MOF composite coating is a composite structure formed by polydimethylsiloxane PDMS penetrating and coating the surface and pores of a metal-organic framework MOF.

[0008] Furthermore, the zinc negative electrode is zinc foil; the thickness of the PDMS@MOF composite coating is 10μm to 20μm.

[0009] A method for preparing the zinc metal anode with the above-mentioned PDMS@MOF composite coating includes the following steps:

[0010] (1) The metal salt and the organic ligand were dissolved in methanol to obtain two solutions. The two solutions were mixed and stirred, allowed to stand, centrifuged to collect the precipitate, and then washed and dried to obtain the metal-organic framework (MOF) material.

[0011] (2) Dissolve the MOF material obtained in step (1) and the binder in N-methylpyrrolidone in a mass ratio to form a slurry. Coat the slurry onto the treated zinc foil and dry it to obtain a metallic zinc anode with MOF coating.

[0012] (3) Dissolve polydimethylsiloxane (PDMS) in tetrahydrofuran to form a solution, spray the solution onto the zinc metal anode with MOF coating obtained in step (2), and after drying, a zinc metal anode with PDMS@MOF composite coating is obtained.

[0013] Further, in step (1), the metal salt is zinc nitrate hexahydrate or cobalt nitrate hexahydrate; the organic ligand is 2-methylimidazole or 2-nitroimidazole.

[0014] Furthermore, the molar ratio of the metal salt to the organic ligand is 2 to 5:1.

[0015] Further, in step (1), the washing is performed by alternating centrifugation washing with deionized water and ethanol 3 to 5 times; the drying is performed by vacuum drying at 60℃ to 80℃ for 12 hours.

[0016] Further, in step (2), the mass ratio of the MOF material to the binder is 9:1, and the binder is polyvinylidene fluoride.

[0017] Further, in step (2), a four-sided coater is used for coating, and the wet film thickness is 30-50 μm; the drying is vacuum drying at 110°C for 12 h.

[0018] Further, in step (3), the volume ratio of PDMS to tetrahydrofuran is 1:2; the spraying is done using a spray gun, the spraying distance is 5-15cm, and the time is 5-10s; the drying is vacuum drying at 110℃ for 18h.

[0019] An aqueous zinc-ion battery includes the aforementioned zinc anode with a PDMS@MOF composite coating.

[0020] Invention concept:

[0021] This invention constructs a PDMS@MOF composite coating by infiltrating PDMS into the pores of MOF and covering its surface. The MOF, with its porous structure, regulates zinc ion transport and guides its uniform deposition. The hydrophobicity of PDMS isolates the electrolyte from the zinc sheet, significantly reducing hydrogen evolution side reactions and electrode corrosion. Simultaneously, the viscoelastic properties of PDMS buffer the volume changes during zinc deposition / dissolution, working in conjunction with the structural support of the MOF to inhibit zinc dendrite growth and extend electrode cycle life.

[0022] Furthermore, by scraping, the MOF adheres tightly to the zinc sheet substrate. The PDMS sprayed subsequently can penetrate into the pores of the MOF and cover the surface, acting as an "adhesive" to fix the MOF particles, preventing MOF from agglomerating or falling off during the cycle. At the same time, it fills in the minor defects of the scraped MOF, forming a dense composite coating without obvious flaws.

[0023] This invention overcomes the problem of compromise in the function of single composite coatings by first scraping MOF and then spraying PDMS in a step-by-step process. The step-by-step process achieves layered division of labor, with MOF responsible for ion transport regulation and PDMS responsible for interface protection and structural buffering, forming a functional gradient structure of "ion regulation-interface protection". This solves the problem that traditional hybrid coatings cannot simultaneously take into account ion conduction efficiency and interface stability.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) The spraying and scraping methods used in this invention are simple, mild, and easy to implement.

[0026] (2) A PDMS@MOF composite coating was constructed by a stepwise process. MOF guides the uniform transport of zinc ions and inhibits dendrites. PDMS provides hydrophobic protection, isolates moisture, and inhibits side reactions. Its viscoelasticity can also buffer volume changes and enhance the durability of the coating.

[0027] (3) The composite coating can significantly extend the cycle life of the zinc anode under different current densities. Attached Figure Description

[0028] Figure 1 A flowchart of the preparation method provided by the present invention;

[0029] Figure 2 This is a SEM image of PDMS@ZIF-8@Zn prepared in Example 1 of the present invention;

[0030] Figure 3 This is a cross-sectional SEM image of PDMS@ZIF-8@Zn prepared in Example 1 of the present invention;

[0031] Figure 4 XPS image of PDMS@ZIF-8@Zn prepared in Example 1 of this invention;

[0032] Figure 5 The XRD pattern of PDMS@ZIF-8@Zn prepared in Example 1 of this invention;

[0033] Figure 6 The FTIR image of PDMS@ZIF-67@Zn prepared in Example 2 of this invention;

[0034] Figure 7 The symmetrical battery assembled with a zinc anode with a PDMS@ZIF-67@Zn coating in Example 2 of this invention and the symmetrical battery assembled with an unmodified zinc anode in Comparative Example 1 have a discharge current / area capacity of 2 mA / cm². -2 / 1mAh cm -2 Cyclic stability plot at time;

[0035] Figure 8 The assembled full cell of the zinc anode with PDMS@ZIF-8@Zn coating and VO2 cathode of Example 1 and the assembled full cell of the unmodified zinc anode and VO2 cathode of Comparative Example 2 were compared at 3Ag. -1 Long-cycle plot at current density;

[0036] Figure 9Optical microscope images of a symmetrical battery assembled with a zinc anode with a PDMS@ZIF-8 coating in Example 1 of the present invention and a symmetrical battery assembled with an unmodified zinc anode in Comparative Example 1, taken at different discharge times. Detailed Implementation

[0037] The following section describes the specific implementation methods of this plan.

[0038] The abbreviations used in this invention are all fixed abbreviations in the field, and some of the letters are explained as follows: SEM image: Scanning Electron Imaging; XRD: X-ray Diffraction Pattern; XPS: X-ray Photoelectron Spectroscopy; FTIR: Fourier Transform Infrared Spectroscopy.

[0039] Example 1

[0040] The zinc anode with PDMS@MOF composite coating in this embodiment is prepared by the following steps:

[0041] (1) Preparation of ZIF-8: 2.025 g of zinc nitrate hexahydrate and 1.135 g of 2-methylimidazole were dissolved in 50 mL of methanol solution respectively, stirred for 30 min respectively, and then the two solutions were mixed and stirred for 6 h. After standing for 2 h, the white precipitate was collected by centrifugation, washed and dried to obtain ZIF-8; washing was performed by washing with ethanol and centrifugation 3 times respectively, and drying was performed by drying in an oven at 60 ℃ for 12 h;

[0042] (2) Preparation of ZIF-8@Zn negative electrode: ZIF-8 obtained in step (1) and polyvinylidene fluoride (PVDF) were added dropwise at a mass ratio of 9:1 and N-methylpyrrolidone (NMP) was ground to form a slurry. The slurry was coated onto the polished and cleaned zinc foil using a four-sided coater. The wet film thickness was 50 μm. After drying at 110℃ for 12 hours, it was cut into round pieces with a diameter of 12 mm to obtain ZIF-8@Zn negative electrode.

[0043] (3) Preparation of PDMS@ZIF-8@Zn negative electrode: Dissolve 5 mL of PDMS in 10 mL of tetrahydrofuran and stir for 12 h to form a solution. Spray the solution onto the ZIF-8@Zn negative electrode disc obtained in step (2) using a spray gun. After drying, the PDMS@ZIF-8@Zn negative electrode is obtained. Dry at 110 °C for 18 h. The spraying distance is 10 cm and the time is 10 s.

[0044] An aqueous zinc-ion symmetric battery was assembled using the PDMS@ZIF-8@Zn negative electrode from Example 1. The battery consisted of an electrode, a separator, and an electrolyte. The electrode was PDMS@ZIF-8@Zn, the electrolyte was 2 mol / L ZnSO4, and the separator was glass fiber filter paper. The battery was assembled in the following order: negative electrode shell, PDMS@ZIF-8@Zn negative electrode, separator, electrolyte, PDMS@ZIF-8@Zn negative electrode, gasket, spring, and positive electrode shell. Then, a coin cell was obtained by pressing the positive electrode shell with a sealing machine.

[0045] An aqueous zinc-ion battery was assembled using the PDMS@ZIF-8@Zn negative electrode from Example 1. This aqueous zinc-ion battery is a PDMS@ZIF-8@Zn / / VO2 coin cell, comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode is VO2, the negative electrode is the PDMS@ZIF-8@Zn negative electrode, the electrolyte is 2 mol / L ZnSO4, and the separator is glass fiber filter paper. The preparation method of this aqueous zinc-ion battery includes the following steps:

[0046] (1) Preparation of VO2: First, 1.2 g of V2O5 powder and 1.8 g of oxalic acid were dispersed in 40 mL of deionized water, and the solution was stirred at 75 °C until it turned deep blue. Then, the solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene and heated at 180 °C for 8 h. After the reactor cooled to room temperature, the black precipitate was collected by centrifugation and washed three times each with deionized water and ethanol. Then, the obtained black product was dried in a vacuum oven at 60 °C for 12 h.

[0047] (2) The VO2, Super P, and polyvinylidene fluoride (PVDF) obtained in step (1) were added to N-methylpyrrolidone (NMP) at a mass ratio of 7:2:1, ground to form a slurry, and then coated onto stainless steel foil and dried at 110°C for 12 hours. To prevent the positive electrode material from breaking and cracking, the material thickness was compressed using an electric roller mill. It was then cut into small circular pieces with a diameter of 10 mm. The battery was assembled with other materials in the following order: negative electrode shell, PDMS@ZIF-8@Zn negative electrode, separator, electrolyte, VO2 positive electrode, gasket, spring, and positive electrode shell were assembled in that order, and then pressed with a sealing machine to obtain a coin cell.

[0048] Example 2

[0049] The zinc anode with PDMS@MOF composite coating in this embodiment is prepared by the following steps:

[0050] (1) Preparation of ZIF-67: 1.75 g of cobalt nitrate hexahydrate and 1.96 g of 2-methylimidazole were added to 60 mL of methanol solution respectively, stirred for 30 min respectively, and then the two solutions were mixed and stirred for 6 h. After standing for 2 h, the precipitate was collected by centrifugation, washed and dried to obtain ZIF-67; washing was performed by washing with ethanol and centrifugation 3 times respectively; drying was performed by drying in an oven at 60 ℃ for 12 h.

[0051] (2) Preparation of ZIF-67@Zn negative electrode: ZIF-67 obtained in step (1) and polyvinylidene fluoride (PVDF) were added dropwise with N-methylpyrrolidone (NMP) at a mass ratio of 9:1 and ground to form a slurry. The slurry was coated onto the polished and cleaned zinc foil using a four-sided coater. The wet film thickness was 50 μm. After drying at 110 °C for 12 hours, it was cut into round pieces with a diameter of 12 mm to obtain ZIF-67@Zn negative electrode.

[0052] (3) Preparation of PDMS@ZIF-67@Zn negative electrode: Dissolve 5 mL of PDMS in 10 mL of tetrahydrofuran and stir for 12 h to form a solution. Spray the solution onto the ZIF-67@Zn negative electrode disc obtained in step (2) using a spray gun. After drying, the PDMS@ZIF-67@Zn negative electrode is obtained. The drying is carried out at 110 °C for 18 h. The spraying distance is 10 cm and the time is 10 s.

[0053] An aqueous zinc-ion symmetric battery was assembled using the PDMS@ZIF-67@Zn negative electrode of Example 2. The battery consisted of an electrode, a separator, and an electrolyte. The electrode was PDMS@ZIF-67@Zn, the electrolyte was 2 mol / L ZnSO4, and the separator was glass fiber filter paper. The battery was assembled in the following order: negative electrode shell, PDMS@ZIF-67@Zn negative electrode, separator, electrolyte, PDMS@ZIF-67@Zn negative electrode, gasket, spring, and positive electrode shell. Then, a coin cell was obtained by pressing the positive electrode shell with a sealing machine.

[0054] An aqueous zinc-ion battery was assembled using the PDMS@ZIF-67@Zn negative electrode from Example 2. The aqueous zinc-ion battery is a PDMS@ZIF-67@Zn / / VO2 coin cell, comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode is VO2, the negative electrode is PDMS@ZIF-67@Zn, the electrolyte is 2 mol / L ZnSO4, and the separator is glass fiber filter paper. The preparation method of this aqueous zinc-ion battery includes the following steps:

[0055] (1) Preparation of VO2: First, 1.2 g of V2O5 powder and 1.8 g of oxalic acid were dispersed in 40 mL of deionized water, and the solution was stirred at 75 °C until it turned deep blue. Then, the solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene and heated at 180 °C for 8 h. After the reactor cooled to room temperature, the black precipitate was collected by centrifugation and washed three times each with deionized water and ethanol. Then, the obtained black product was dried in a vacuum oven at 60 °C for 12 h.

[0056] (2) The VO2, Super P, and polyvinylidene fluoride (PVDF) obtained in step (1) were added to N-methylpyrrolidone (NMP) at a mass ratio of 7:2:1, ground to form a slurry, and then coated onto stainless steel foil and dried at 110°C for 12 hours. To prevent the positive electrode material from breaking and cracking, the material thickness was compressed using an electric roller mill. It was then cut into small circular pieces with a diameter of 10 mm. The battery was assembled with other materials in the following order: negative electrode shell, PDMS@ZIF-67@Zn negative electrode, separator, electrolyte, VO2 positive electrode, gasket, spring, and positive electrode shell were assembled in that order, and then pressed with a sealing machine to obtain a coin cell.

[0057] Comparative Example 1

[0058] This comparative example uses unmodified Zn to assemble an aqueous zinc-ion battery, which is a coin-type symmetrical battery. It is prepared by the following steps: using unmodified zinc foil as the symmetrical electrode, glass fiber as the separator, and 2 mol / L ZnSO4 as the electrolyte, a symmetrical battery is assembled. The specific steps are: assembling the negative electrode shell, zinc foil, separator, electrolyte, zinc foil again, gasket, spring, and positive electrode shell in that order.

[0059] Comparative Example 2

[0060] This comparative example uses unmodified Zn to assemble an aqueous zinc-ion battery. The aqueous zinc-ion battery is a Zn / / VO2 coin cell, including a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode is VO2, the negative electrode is Zn, the electrolyte is 2 mol / L ZnSO4, and the separator is glass fiber filter paper. The preparation method of this aqueous zinc-ion battery includes the following steps:

[0061] (1) Preparation of VO2: First, 1.2 g of V2O5 powder and 1.8 g of oxalic acid were dispersed in 40 mL of deionized water, and the solution was stirred at 75 °C until it turned deep blue. Then, the solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene and heated at 180 °C for 8 h. After the reactor cooled to room temperature, the black precipitate was collected by centrifugation and washed three times with deionized water and ethanol, respectively. Then, the obtained black product was dried in a vacuum oven at 60 °C for 12 h.

[0062] (2) The VO2, Super P and polyvinylidene fluoride (PVDF) obtained in step (1) were added to N-methylpyrrolidone (NMP) at a mass ratio of 7:2:1, ground to form a slurry, and then coated on stainless steel foil and dried at 110°C for 12 hours. To prevent the positive electrode material from breaking and cracking, the material thickness was compressed using an electric roller mill; it was cut into small round pieces with a diameter of 10 mm; and assembled into a battery with other materials in the following steps: the negative electrode shell, unmodified zinc foil negative electrode, separator, electrolyte, VO2 positive electrode, gasket, spring, and positive electrode shell were assembled in sequence, and then pressed with a sealing machine to obtain a button cell.

[0063] Comparative Example 3

[0064] This comparative example provides a ZIF-8@Zn anode, the preparation method of which differs from that of Example 1 only in that step (3) is omitted. Using the ZIF-8@Zn anode, a symmetrical cell was assembled according to the method of Example 1.

[0065] Electrochemical performance and characterization tests were performed on Examples 1-2 and Comparative Examples 1-3, and the results are shown in the figure. Figures 1-9 According to Table 1, the test methods include:

[0066] Cyclic stability testing: The battery testing system is used to perform charge-discharge cycles at specific current densities and areal capacities, and the voltage-time curves and cycle life are recorded.

[0067] Characterization tests: Surface morphology and cross-sectional structure were observed by scanning electron microscopy (SEM); crystal structure was analyzed by X-ray diffraction (XRD); elemental composition of the surface was analyzed by X-ray photoelectron spectroscopy (XPS); chemical structure was verified by Fourier transform infrared spectroscopy (FTIR); and zinc deposition morphology was observed by optical microscopy.

[0068] Figure 1 The flowchart of the preparation method provided by the present invention is as follows: MOF synthesis → MOF coating → PDMS spraying.

[0069] Figure 2 The image shows a SEM image of PDMS@ZIF-8@Zn prepared in Example 1 of this invention. The PDMS particles are solidified on the surface and are formed by the removal of THF solvent at high temperature after spraying.

[0070] Figure 3 The image shows a cross-sectional SEM image of PDMS@ZIF-8@Zn prepared in Example 1 of this invention. The coating thickness is uniform, approximately 16.1 μm, and the MOF and PDMS are tightly bonded.

[0071] Figure 4The XPS image shows the PDMS@ZIF-8@Zn prepared in Example 1 of this invention, proving that PDMS@ZIF-8 is well coated on the zinc anode.

[0072] Figure 5 The image shows the XRD pattern of PDMS@ZIF-8@Zn prepared in Example 1 of this invention. The positions of the characteristic diffraction peaks correspond well, indicating that the zinc base and the crystal structure of ZIF-8 were not damaged during the modification process.

[0073] Figure 6 The figure shows the FTIR spectrum of PDMS@ZIF-67@Zn prepared in Example 2 of this invention, at 1581 cm⁻¹. -1 and 421cm -1 C=N bonds and Zn-N bonds appeared at all locations of ZIF-8, and the PDMS@ZIF-67@Zn anode was at 1260 cm⁻¹. -1 and 799cm -1 Si-O bonds and Si-C bonds appeared.

[0074] Figure 7 The symmetrical battery assembled with a zinc anode with a PDMS@ZIF-67 coating in Example 2 of this invention and the symmetrical battery assembled with an unmodified zinc anode in Comparative Example 1 have a discharge current / area capacity of 2 mA / cm². -2 / 1mAh cm -2 The cyclic stability diagram shows that bare zinc and MOF@Zn both experienced short circuits after 80 and 250 cycles, respectively, while PDMS@MOF@Zn could cycle for more than 1000 cycles.

[0075] Figure 8 The full cell assembled from the zinc anode with PDMS@ZIF-8 coating and the VO2 cathode of Example 1 of the present invention, and the full cell assembled from the unmodified zinc anode and the VO2 cathode of Comparative Example 2, were tested at 3Ag. -1 Long-term cycling curves at current density show that the PDMS@ZIF-8@Zn / / VO2 full cell exhibits excellent cycling stability after 870 cycles, with a capacity retention of 78.3%, and maintains a capacity of 3Ag. -1 It has a current density of 83.4 mAh g. -1 The Zn / / VO2 full cell exhibits high capacity. However, it demonstrates poor cycle stability, with a capacity of only 38.1 mAh g after 870 cycles. -1 .

[0076] Figure 9The images show optical microscope images of a symmetrical battery assembled with a zinc anode with a PDMS@ZIF-8 coating in Example 1 and a symmetrical battery assembled with an unmodified zinc anode in Comparative Example 1 at different discharge times. It can be seen that bare zinc showed obvious dendrite growth and bubble generation after 10 min, while fine dendrites only appeared after 40 min.

[0077] Table 1 Comparison of Cycle Counts of Symmetric Cells at Different Current Densities

[0078]

[0079] As shown in Table 1, the PDMS@MOF@Zn anode operates at 1 mA cm⁻¹. -2 and 2mAcm -2 Under the same conditions, both exhibited optimal cycling stability, achieving 1250 and 1150 cycles respectively, significantly higher than Comparative Example 1 (bare zinc, 80 cycles) and Comparative Example 3 (MOF@Zn, 400 and 250 cycles). This indicates that the PDMS@MOF composite coating significantly improves the durability of the zinc anode through synergistic effects. MOF guides uniform zinc ion deposition and suppresses dendrite formation; PDMS provides hydrophobic protection and reduces side reactions. The functionally graded coating constructed using a stepwise process effectively solves the problems of dendrite growth and corrosion, extending battery life.

Claims

1. A zinc metal anode with a PDMS@MOF composite coating, characterized in that, It includes a zinc anode and a PDMS@MOF composite coating disposed on the surface of the zinc anode; the PDMS@MOF composite coating is a composite structure formed by polydimethylsiloxane PDMS penetrating and coating the surface and pores of a metal-organic framework MOF.

2. The zinc anode according to claim 1, characterized in that, The zinc negative electrode is zinc foil; the thickness of the PDMS@MOF composite coating is 10μm to 20μm.

3. A method for preparing a zinc metal anode with a PDMS@MOF composite coating as described in any one of claims 1 to 2, characterized in that, Includes the following steps: (1) The metal salt and the organic ligand were dissolved in methanol to obtain two solutions. The two solutions were mixed and stirred, allowed to stand, centrifuged to collect the precipitate, and then washed and dried to obtain the metal-organic framework (MOF) material. (2) Dissolve the MOF material obtained in step (1) and the binder in N-methylpyrrolidone in a mass ratio to form a slurry. Coat the slurry onto the treated zinc foil and dry it to obtain a metallic zinc anode with MOF coating. (3) Dissolve polydimethylsiloxane (PDMS) in tetrahydrofuran to form a solution, spray the solution onto the zinc metal anode with MOF coating obtained in step (2), and after drying, a zinc metal anode with PDMS@MOF composite coating is obtained.

4. The preparation method according to claim 3, characterized in that, In step (1), the metal salt is zinc nitrate hexahydrate or cobalt nitrate hexahydrate; the organic ligand is 2-methylimidazole or 2-nitroimidazole.

5. The preparation method according to claim 4, characterized in that, The molar ratio of the metal salt to the organic ligand is 2 to 5:

1.

6. The preparation method according to claim 3, characterized in that, In step (1), the washing is performed by alternating centrifugation washing with deionized water and ethanol 3 to 5 times; the drying is performed by vacuum drying at 60℃ to 80℃ for 12 hours.

7. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of the MOF material to the binder is 9:1, and the binder is polyvinylidene fluoride.

8. The preparation method according to claim 3, characterized in that, In step (2), a four-sided coater is used for coating, and the wet film thickness is 30-50 μm; the drying is vacuum drying at 110°C for 12 h.

9. The preparation method according to claim 3, characterized in that, In step (3), the volume ratio of PDMS to tetrahydrofuran is 1:2; the spraying is done using a spray gun, the spraying distance is 5-15cm, and the time is 5-10s; the drying is vacuum drying at 110℃ for 18h.

10. An aqueous zinc-ion battery, characterized in that, Including the zinc anode with a PDMS@MOF composite coating as described in any one of claims 1-2.

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