A pda-zro2-coated zinc anode and a preparation method and battery thereof

Abstract

The application provides a PDA-ZrO2 coated zinc anode and a preparation method and a battery thereof, and belongs to the technical field of electrochemical energy storage materials. The zinc anode is provided with a polydopamine-zirconium dioxide composite protective layer on the surface of a zinc substrate. The composite layer is formed by first forming a polydopamine bottom layer through self-polymerization of dopamine on the surface of the zinc foil, and then introducing a zirconium dioxide layer on the polydopamine layer through an in-situ mineralization method. The main advantage of the application is that the PDA-ZrO2 composite layer ingeniously combines the strong adhesion, excellent flexibility and ion regulation capacity of polydopamine, and the high mechanical strength and chemical stability of zirconium dioxide. The synergistic effect of the'soft and hard combination' can effectively homogenize the zinc ion flow, inhibit the growth of dendrites, and block the side reactions caused by water molecules, thereby significantly improving the interface stability and cycle life of the zinc metal anode. The preparation method is simple in process, mild in conditions and easy to scale up.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage materials technology, specifically relating to a modified zinc metal anode for aqueous zinc-ion batteries, particularly a PDA-ZrO2 coated zinc anode, its preparation method, and the battery thereof. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] With the large-scale grid connection of renewable energy and the rapid popularization of portable electronic devices, the development of safe, low-cost, and environmentally friendly energy storage systems has become an urgent need. Among various candidate technologies, aqueous zinc-ion batteries stand out due to the abundance of zinc resources and their high theoretical volumetric capacity (5855 mAh cm⁻¹). -3 Zinc metal anodes are considered an ideal choice for next-generation large-scale energy storage due to their outstanding advantages such as inherent safety (using non-flammable aqueous electrolytes) and environmental friendliness. However, their commercial application is severely limited by the inherent defects of zinc metal anodes, including the easy occurrence of side reactions such as zinc dendrite growth, hydrogen evolution, and corrosion during repeated deposition / stripping during charging and discharging. These problems stem from the fact that the unstable electrode / electrolyte interface cannot effectively regulate the uniform deposition of zinc ions and prevent water molecule erosion. To solve these problems, on the one hand, it is necessary to design and develop electrode materials with high capacity and high operating voltage to improve the energy output of the battery. On the other hand, it is necessary to induce Zn... 2+ Uniform deposition is achieved to obtain a uniform morphology, thereby suppressing the formation of zinc dendrites.

[0004] To stabilize the zinc anode interface, existing technologies mainly focus on strategies such as electrolyte engineering, electrode structure design, and interface engineering. Among these, interface engineering methods for constructing artificial protective layers have attracted considerable attention due to their simplicity, economy, and direct effectiveness. Artificial protective layers primarily consist of inorganic layers (such as ZnSiO3, CaCO3, CeO2, ZrO2, and Al2O3) and organic polymer layers. While inorganic layers possess high mechanical strength and can effectively physically block dendrites, their rigidity leads to poor adhesion to the zinc substrate, making them prone to peeling and failure under cyclic stress. Organic polymer layers (such as polydopamine PDA), while exhibiting good flexibility, strong adhesion, and ion control capabilities, suffer from insufficient mechanical strength and are susceptible to degradation and cracking during long-term cycling. Therefore, it is difficult for a single-component protective layer to achieve an ideal balance between adhesion, mechanical strength, flexibility, and chemical stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to construct a composite protection solution that can significantly improve the stability of the zinc metal anode interface in aqueous zinc-ion batteries. It also provides a method with a simple preparation process, mild conditions, and easy scalability for constructing a composite protective layer that can significantly improve the stability of the zinc metal anode interface in aqueous zinc-ion batteries.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] As a first aspect of the present invention, a method for preparing a PDA-ZrO2-coated zinc anode is provided, comprising the following steps:

[0008] S1. Zinc foil pretreatment;

[0009] S2, Deposition of the polydopamine layer:

[0010] S201: Prepare solution A: a weakly alkaline buffer solution, and solution B: an acidic solution of dopamine hydrochloride; the weakly alkaline buffer solution is a Tris buffer solution with a concentration of 0.08~0.12 mol / L; the concentration of dopamine hydrochloride in the acidic solution of dopamine hydrochloride is 1-3 mg / mL;

[0011] S202: Mix solution A and solution B to form a reaction solution;

[0012] S203: The zinc foil pretreated in S1 is immersed in the reaction solution prepared in S202 to carry out a polymerization reaction, so that the polydopamine layer is deposited in situ on the surface of the zinc substrate.

[0013] S3, mineralization growth of the zirconium dioxide layer:

[0014] S301: Prepare an acidic mineralization solution containing a zirconium source, wherein the zirconium source is selected from zirconium sulfate and zirconium nitrate or their hydrates;

[0015] S302: The product obtained in S2 is immersed in the acidic mineralization solution containing zirconium source described in S301 to carry out a mineralization reaction, thereby obtaining a zinc metal anode with a polydopamine-zirconia composite protective layer.

[0016] Preferably, in step S1, zinc foil with a thickness of 0.05 mm to 0.2 mm is pretreated. The pretreatment method is as follows: after cutting the zinc foil, it is immersed in hydrochloric acid solution to remove the surface oxide layer, cleaned, and dried for later use. When the zinc foil thickness is small, its performance is limited by the total amount of zinc source and the increased side reactions caused by the increased specific surface area; when the thickness is large, the lifespan is reduced due to increased polarization and amplified volume effect.

[0017] Preferably, in S203, the polymerization reaction occurs at a pH of 7-9, a temperature of 30-50°C, and a reaction time of 1-4 hours. Incomplete polymerization can lead to incomplete substrate coverage, resulting in reduced cycle life.

[0018] Preferably, in S301, the zirconium source is zirconium sulfate tetrahydrate.

[0019] Preferably, in S301, the method for preparing the acidic mineralization solution containing zirconium source is to dissolve the zirconium source in hydrochloric acid solution.

[0020] Preferably, the mass ratio of dopamine hydrochloride and zirconium sulfate tetrahydrate used in S201 and S301 is 0.05~0.1:0.07~0.14. The concentration of zirconium has a significant impact on the morphology and mechanical strength of the mineralized ZrO2 layer, thereby affecting the uniformity and long-term stability of the protective effect.

[0021] Preferably, in S301, the pH of the acidic mineralization solution containing the zirconium source is 0.7-1.

[0022] Preferably, in S302, the mineralization reaction temperature is 25-45℃, and the mineralization reaction time is 2-6 hours. Excessive mineralization time leads to increased coating thickness, which, while more effectively suppressing dendrites, may increase overpotential, resulting in decreased long-cycle stability and reduced cycle life.

[0023] As a second aspect of the present invention, a PDA-ZrO2-coated zinc anode prepared by the preparation method of the first aspect is provided, the zinc anode comprising a zinc substrate and a polydopamine-zirconia composite protective layer formed on the surface of the zinc substrate; the composite protective layer is composed of a polydopamine flexible underlayer and zirconia nanoparticles distributed thereon.

[0024] Preferably, the zirconium dioxide nanoparticles are grown in situ through induction of functional groups in the polydopamine layer, forming an organic-inorganic hybrid structure with the polydopamine flexible substrate.

[0025] As a third aspect of the present invention, a battery is provided, comprising a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode is a zinc anode prepared by the preparation method of the first aspect or a zinc anode as described in the second aspect.

[0026] A key mechanism of this invention lies in the fact that the polydopamine layer formed first not only serves as a flexible underlayer with strong adhesion, but its abundant functional groups (such as catechols and amines) can also effectively adsorb Zr in the solution. 4+ This provides abundant active sites for the subsequent heterogeneous nucleation and growth of zirconium dioxide, thereby ensuring the uniform distribution of zirconium dioxide nanoparticles and their strong bond with the polydopamine layer, achieving a close composite of organic and inorganic phases.

[0027] The composite coating provided by this invention overcomes the shortcomings of existing single-component protective layers (pure inorganic or pure organic layers) in balancing adhesion, mechanical strength and flexibility. By constructing a composite protective layer that combines softness and hardness, the organic phase is used to buffer stress and uniform ion flow through its flexibility and strong adhesion, while the inorganic phase is used to suppress dendrite growth and side reactions through its high strength and stability. The two effects work together to solve the problem of interface stability, thereby promoting the practical application of aqueous zinc-ion battery technology.

[0028] Meanwhile, through experimental comparison, the preparation method provided by this invention can further improve the performance of batteries prepared with zinc anodes.

[0029] This invention provides a method for preparing a polydopamine-zirconium dioxide composite protective layer for the zinc metal anode of an aqueous zinc-ion battery, and the resulting PDA-ZrO2 composite layer. Compared with the prior art, it has the following advantages:

[0030] (1) Synergistic protection effect: The PDA-ZrO2 composite layer prepared in this invention combines the excellent adhesion, flexibility and ion conduction regulation ability of PDA with the high mechanical strength and chemical inertness of ZrO2, achieving synergistic protection of both soft and hard, and can effectively inhibit the growth of zinc dendrites and alleviate side reactions at the same time.

[0031] (2) Simple and mild process: The preparation process provided by the present invention is carried out at room temperature, without the need for complex equipment or high temperature and high pressure conditions. It is easy to operate, has low energy consumption, good compatibility with existing battery electrode production processes, and is easy to scale up and achieve large-scale application.

[0032] (3) Strong interface bonding: The present invention first forms the PDA bottom layer by stepping and then induces the growth of ZrO2, which realizes strong interaction and strong bonding between the two layers, avoids the problem of easy peeling of rigid inorganic layer, and significantly improves the long-term cycle stability of protective layer.

[0033] (4) Significantly improved performance: When the Zn-PDA@ZrO2 anode prepared in this invention is used in an aqueous zinc-ion battery, high coulombic efficiency, excellent rate performance and significantly extended cycle life can be expected.

[0034] Additional aspects and advantages of the invention will be set forth in part in the detailed description which follows, and in part will be obvious from the description or may be learned by practice of the invention. Attached Figure Description

[0035] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0036] Figure 1 The images shown are scanning electron microscope (SEM) images and mapping diagrams of the Zn-PDA@ZrO2 composite material (Zn-PDA@ZrO2) obtained in Example 1; where a is a scanning electron microscope SEM image, b is a distribution map of zinc, c is a distribution map of zirconium, d is a distribution map of oxygen, e is a distribution map of carbon, and f is a distribution map of nitrogen.

[0037] Figure 2 The X-ray photoelectron spectroscopy (XPS) spectra of Comparative Example 1 (bare zinc), Comparative Example 2 (Zn-PDA), and Example 1 (Zn-PDA@ZrO2) of this invention are shown.

[0038] Figure 3 Contact angle test photographs of zinc electrodes of Comparative Example 1 (bare zinc), Comparative Example 2 (Zn-PDA), and Example 1 (Zn-PDA@ZrO2) with 2 mol / L ZnSO4 electrolyte; wherein, a is bare zinc, b is Zn-PDA, and c is Zn-PDA@ZrO2.

[0039] Figure 4 Symmetrical cells assembled with zinc electrodes for Comparative Example 1 (bare zinc), Comparative Example 2 (Zn-PDA), and Example 1 (Zn-PDA@ZrO2) of this invention were used at 2 mA cm⁻¹. -2 and 1 mAh cm -2 Cyclic curves under certain conditions.

[0040] Figure 5 The full cells assembled with zinc electrodes of Comparative Example 1 (bare zinc), Comparative Example 2 (Zn-PDA), and Example 1 (Zn-PDA@ZrO2) of this invention are shown as galvanostatic cycling curves at a current density of 5 A / g.

[0041] Figure 6 The images show a comparison of scanning electron microscope (SEM) images of Comparative Example 1 (bare zinc), Comparative Example 2 (Zn-PDA), and Example 1 (Zn-PDA@ZrO2) after immersion in 2 M ZnSO4 electrolyte for 10 days; where a is bare zinc, b is Zn-PDA, and c is Zn-PDA@ZrO2. Detailed Implementation

[0042] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0043] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0044] In some embodiments of the present invention, a method for preparing a PDA-ZrO2-coated zinc anode is provided, comprising the following steps:

[0045] S1. Zinc foil pretreatment;

[0046] S2. Deposition of the polydopamine layer yields the intermediate product Zn-PDA with a polydopamine layer on its surface:

[0047] S201: Prepare solution A: a weakly alkaline buffer solution, and solution B: an acidic solution of dopamine hydrochloride; the weakly alkaline buffer solution is a Tris buffer solution with a concentration of 0.08-0.12 mol / L; the concentration of dopamine hydrochloride in the acidic solution of dopamine hydrochloride is 1-3 mg / mL;

[0048] S202: Mix solution A and solution B to form a reaction solution;

[0049] S203: The zinc foil pretreated in S1 is immersed in the reaction solution prepared in S202 to carry out a polymerization reaction, so that the polydopamine layer is deposited in situ on the surface of the zinc substrate.

[0050] S3, mineralization growth of the zirconium dioxide layer, yields a zinc metal anode Zn-PDA@ZrO2 with a polydopamine-zirconia composite protective layer:

[0051] S301: Prepare an acidic mineralization solution containing a zirconium source, wherein the zirconium source is selected from zirconium sulfate and zirconium nitrate or their hydrates;

[0052] S302: The intermediate product with a polydopamine layer on its surface obtained in S2 is immersed in the acidic mineralization solution containing zirconium source described in S301 to carry out a mineralization reaction, thereby obtaining a zinc metal anode Zn-PDA@ZrO2 with a polydopamine-zirconia composite protective layer.

[0053] During the mineralization reaction, the zirconium source is hydrolyzed under the induction of the polydopamine layer and uniformly deposited on the polydopamine layer to form the zirconium dioxide phase;

[0054] After the reaction was completed, the sample was removed, washed and dried to obtain a zinc metal anode Zn-PDA@ZrO2 with a polydopamine-zirconia composite protective layer.

[0055] In some embodiments, in S1, zinc foil with a thickness of 0.05 mm to 0.2 mm is pretreated. The pretreatment method is as follows: after cutting the zinc foil, it is immersed in hydrochloric acid solution to remove the surface oxide layer, cleaned, and dried for later use.

[0056] In some embodiments, in S203, the pH of the polymerization reaction is 7-9 (maintained by Tris-HCl buffer), the reaction temperature is 30-50°C, and the reaction time is 1-4 hours.

[0057] In some embodiments, in S301, the zirconium source is zirconium sulfate tetrahydrate. The method for preparing the acidic mineralization solution containing the zirconium source is as follows: the zirconium source is dissolved in hydrochloric acid solution.

[0058] In some embodiments, the mass ratio of dopamine hydrochloride and zirconium sulfate tetrahydrate used in S201 and S301 is 0.05~0.1:0.07~0.14.

[0059] In some embodiments, in S301, the pH of the acidic mineralization solution containing the zirconium source is 0.7-1.

[0060] In some embodiments, in S302, the temperature of the mineralization reaction is 25-45°C, and the mineralization reaction time is 2-6 hours.

[0061] In some embodiments of the present invention, a PDA-ZrO2-coated zinc anode is provided, the zinc anode comprising a zinc substrate and a polydopamine-zirconia composite protective layer formed on the surface of the zinc substrate; the composite protective layer is composed of a polydopamine flexible underlayer and zirconia nanoparticles distributed thereon.

[0062] In some embodiments of the present invention, a battery is provided, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is a zinc anode prepared by the preparation method described in the first aspect or a zinc anode described in the second aspect.

[0063] In some comparative examples, single PDA coatings were prepared. Compared with the composite coatings provided in the examples, it was found that although the single PDA coating can improve the interface performance, its mechanical strength is insufficient and its long-term cycle stability is limited, thus demonstrating the necessity of introducing ZrO2 for composite.

[0064] Example 1

[0065] This embodiment provides a method for preparing a zinc metal anode based on a polydopamine-zirconia composite coating, comprising the following steps:

[0066] S1, Zinc foil pretreatment

[0067] High-purity zinc foil with a thickness of 0.1 mm was cut into circular pieces with a diameter of 12 mm. The pieces were then soaked in 1 mol / L dilute hydrochloric acid for 10 seconds to remove the surface oxide layer. They were then ultrasonically cleaned with deionized water and anhydrous ethanol for 5 minutes each, and dried with high-purity nitrogen gas for later use.

[0068] Deposition of S2 and PDA layers

[0069] Preparation of solution A: Dissolve 0.606 g of tris(hydroxymethyl)aminomethane (Tris) in 50 mL of deionized water and sonicate until completely dissolved to obtain a Tris solution with a concentration of 0.1 mol / L.

[0070] Preparation of solution B: Dissolve 0.1 g of dopamine hydrochloride in 35 mL of deionized water, then mix it with the hydrochloric acid solution obtained by diluting 1.5 mL of 1 mol / L hydrochloric acid to 15 mL, and disperse it by ultrasonication to form a homogeneous solution.

[0071] Mix solutions A and B in a beaker and stir at 500 rpm using a magnetic stirrer. Immerse the pretreated zinc foil in the mixed solution and react at 25°C for 2 hours.

[0072] After the reaction was completed, the zinc foil was removed and washed three times each with deionized water and anhydrous ethanol, and then dried with high-purity nitrogen to obtain the Zn-PDA intermediate.

[0073] Mineralization growth of S3 and ZrO2 layers

[0074] Preparation of the zirconium precursor solution: Dissolve 0.14 g of zirconium sulfate tetrahydrate (Zr(SO4)2·4H2O) in an acidic solution (pH≈1.0) diluted to 100 mL with 1 mL of 1 mol / L hydrochloric acid, and stir magnetically (300 rpm) for 30 minutes until completely dissolved. Immerse the above Zn-PDA intermediate in the zirconium precursor solution and allow it to stand at 25 °C for 4 hours for mineralization. After the mineralization reaction is complete, remove the sample, wash it three times each with deionized water and anhydrous ethanol, and dry it with high-purity nitrogen gas to finally obtain a Zn-PDA@ZrO2 zinc metal anode with a polydopamine-zirconia composite protective layer.

[0075] Comparative Example 1

[0076] The clean zinc foil pretreated in step 1 of Example 1 was used directly as the bare zinc electrode in the comparative example.

[0077] Comparative Example 2

[0078] This comparative example is exactly the same as steps S1 and S2 in Example 1, but does not include step S3.

[0079] Example 2: The Influence of PDA Aggregation Time

[0080] This embodiment is basically the same as Embodiment 1, except that the PDA polymerization reaction time in step S2 is shortened from 2 hours to 1 hour.

[0081] Example 3: Effect of dopamine hydrochloride concentration

[0082] This embodiment is basically the same as that of Embodiment 1, except that the amount of dopamine hydrochloride in step S2 is reduced from 0.1 g to 0.05 g.

[0083] Example 4: Effect of ZrO2 mineralization time

[0084] This embodiment is basically the same as Embodiment 1, except that the ZrO2 mineralization reaction time in step S3 is extended from 4 hours to 6 hours.

[0085] Example 5: Effect of Zirconium Sulfate Tetrahydrate Concentration

[0086] This embodiment is basically the same as Embodiment 1, except that the amount of zirconium sulfate tetrahydrate used in step S3 is reduced from 0.14 g to 0.07 g.

[0087] Example 6: The Influence of Zirconium Source Type

[0088] This embodiment is basically the same as that of embodiment 1, except that in step 3, zirconium sulfate tetrahydrate is replaced with zirconium nitrate pentahydrate, with a mass of 0.17 g, which is the same as the number of moles of zirconium sulfate tetrahydrate in S3 of embodiment 1.

[0089] Example 7: Effect of pH value on mineralization solution

[0090] This embodiment is basically the same as Example 1, except that in step S3, when preparing the zirconium precursor solution, 1 mL of 1 mol / L hydrochloric acid is used to dilute it to 50 mL so that the pH of the resulting mineralization solution is about 0.7.

[0091] Example 8: The effect of zinc foil thickness (1)

[0092] This embodiment is basically the same as Embodiment 1, except that in step S1, the zinc foil thickness is 0.05 mm, and the other preparation parameters are exactly the same as in Embodiment 1.

[0093] Example 9: The effect of zinc foil thickness (2)

[0094] This embodiment is basically the same as Embodiment 1, except that in step S1, the zinc foil thickness is 0.2 mm, and the other preparation parameters are exactly the same as in Embodiment 1.

[0095] Application Example 1

[0096] Using commercially available CR2030 electrode shells, 12 mm diameter commercial zinc foil (for negative or symmetrical cell electrodes), 16 mm diameter glass fiber separators, and 120 μL of the modified electrolyte obtained in Example 1, Zn||Zn symmetrical cells, Zn||Cu half-cells, and Zn||NVO full cells were assembled, respectively. In the Zn||Zn symmetrical cells, both the positive and negative electrodes were zinc foil; in the Zn||Cu half-cells, the positive electrode was copper foil, and the negative electrode was zinc foil; in the Zn||NVO full cells, the positive electrode was titanium foil coated with ammonium vanadate, and the negative electrode was zinc foil. Each cell structure was assembled in the following order: negative electrode shell - zinc foil - separator - electrolyte - gasket - spring contact - positive electrode shell, and then pressurized and sealed.

[0097] Figure 1 Scanning electron microscope (SEM) images and corresponding elemental mappings of the Zn-PDA@ZrO2 composite material prepared in Example 1 are presented. Figure 1 In the figure, 'a' represents the overall morphology of the composite material as determined by scanning electron microscopy. Figure 1 In the diagram, b represents the distribution of zinc in the corresponding region; Figure 1 In the figure, c represents the distribution of zirconium. Figure 1 In the diagram, d represents the distribution of oxygen. Figure 1 In the figure, 'e' represents the distribution of carbon. Figure 1 In the figure, f represents the distribution of nitrogen. The results show that the material surface morphology is uniform, and elements such as C, N, O, and Zr are clearly visible and uniformly distributed in the selected area. This confirms that PDA and ZrO2 have been successfully composited on the zinc foil surface, forming a well-covered protective layer.

[0098] Figure 2X-ray photoelectron spectroscopy (XPS) analyses of the bare zinc electrode, Zn@PDA electrode, and Zn@PDA-ZrO2 electrode prepared in Examples 1, 1, and 2 are presented. The results confirm the successful introduction of Zr, with characteristic peaks including a Zr 3d peak and a Zr 3p peak at 182 eV. Other characteristic peaks in the spectra correspond to: a C 1s peak at 284 eV (mainly originating from the aromatic skeleton of PDA), an N 1s peak at 400 eV (corresponding to the amino group in PDA), and an O 1s peak at 531 eV (attributed to the oxygen in the ZrO2 lattice and the hydroxyl group in PDA). These results indicate that PDA and ZrO2 form a stable molecular composite structure through chemical bonding. This structure is beneficial for improving interfacial stability and inhibiting coating peeling, providing direct evidence for the synergistic mechanism of the composite coating.

[0099] Figure 3 Contact angle analysis of the bare zinc electrode, Zn-PDA electrode, and Zn-PDA@ZrO2 electrode prepared in Example 1, Comparative Example 1, and Comparative Example 2 is presented. Figure 3 As shown in Figure a, the contact angle between the bare zinc foil and the electrolyte is 89.7°, indicating that its surface has electrolyte-repellent properties. This phenomenon is mainly attributed to the oxide layer on the zinc surface and its smooth microstructure, which together result in poor wetting performance of the electrolyte on the zinc foil surface. After modification with polyPDA, as shown in Figure a... Figure 3 As shown in Figure b, the contact angle decreased to 82.8°, thanks to the strong adhesion between the polar functional groups such as hydroxyl and amino groups in the PDA molecule and the zinc surface. Simultaneously, these polar groups can interact with water molecules through hydrogen bonds, thus significantly enhancing the hydrophilicity of the material surface. Further introduction of ZrO2 to construct a composite coating, as shown... Figure 3 As shown in Figure c, the contact angle further decreased to 63.4%. This is due, on the one hand, to the increased surface roughness resulting from the introduction of ZrO2 nanoparticles, and on the other hand, to the fact that the abundant hydroxyl groups on the ZrO2 surface provide more hydrogen bonding sites for the electrolyte, which, in synergy with the polar groups in the PDA, enhance the wetting properties of the interface.

[0100] The contact angles exhibit a gradually decreasing trend, fully validating the positive effect of the PDA-ZrO2 composite coating in improving the wettability of zinc foil surfaces. Lower contact angles facilitate more uniform electrolyte spreading on the electrode surface, thereby mitigating the problem of uneven local electrolyte concentration distribution, inhibiting uneven growth of zinc dendrites, and promoting Zn... 2+ The efficient transport of these substances. These effects collectively provide strong support for improving the cycle stability and overall electrochemical performance of zinc-based batteries.

[0101] Figure 4The results of long-term cycling tests on the symmetric cell assembled according to Application Example 1 are presented. Long-term cycling stability tests show that the cycling performance of the three electrode materials differs significantly at different current densities. At 2 mA / cm²... 2 and 1 mAh / cm 2 Under the specified conditions, the bare zinc foil electrode experienced a short-circuit failure after approximately 145 hours of cycling; the Zn-PDA electrode's cycle life was extended to approximately 650 hours before short-circuiting; while the Zn-PDA@ZrO2 electrode maintained a stable charge-discharge plateau throughout the entire 1000-hour test, without experiencing short-circuiting. Compared to the bare zinc electrode, both surface-modified electrodes exhibited superior cycle stability, indicating that surface modification effectively suppresses zinc dendrite growth and related side reactions, thereby significantly improving the cycle durability of the zinc anode at high current densities. Among them, the Zn-PDA@ZrO2 electrode demonstrated the best electrochemical stability.

[0102] Figure 5 The results of long-term cycling tests on the full cell assembled according to Application Example 1 are presented. The current density is 5.0 A / g. The Zn-PDA@ZrO2 full cell still exhibits excellent cycle stability after 1000 cycles. The initial discharge capacities of the three cells are relatively similar, at 188.80 mAh / g (bare zinc), 195.98 mAh / g (Zn-PDA), and 198.52 mAh / g (Zn-PDA@ZrO2). The bare zinc cell rapidly decays to 135.55 mAh / g in the first 106 cycles, which may be attributed to increased interfacial impedance due to zinc dendrite puncture of the separator or accumulation of by-reaction products. In contrast, the Zn-PDA cell exhibits a slower decline in capacity in the first 106 cycles and then enters a stable cycling phase, with a capacity of 185 mAh / g at the 106th cycle and maintaining a discharge capacity of 149.83 mAh / g after 799 cycles, significantly outperforming the bare zinc cell. The Zn-PDA@ZrO2 battery exhibits the best performance, maintaining a capacity of 177.99 mAh / g after 1000 cycles, with a capacity retention of 89.66%. Furthermore, the Zn-PDA@ZrO2 battery demonstrates a stable coulombic efficiency close to 100%, while the coulombic efficiency of bare zinc batteries fluctuates significantly and is considerably lower than that of the modified full cell.

[0103] The symmetrical cells of each embodiment were tested at 2 mA / cm². 2 and 1 mAh / cm 2 Long-cycle performance tests were conducted at the specified current density, and the results are shown in Table 1.

[0104] Table 1. Long-cycle test results of symmetric cells

[0105]

[0106] Based on the symmetric cell cycle test results of the comparative examples and embodiments, the influence of various preparation parameters on the electrochemical performance of the zinc metal anode was clearly revealed. Among them, Comparative Example 1 (bare zinc electrode) could only maintain a cycle life of about 145 hours, which fully exposed the severe dendrite growth and side reaction problems faced by the unmodified zinc metal anode; the cycle life of Comparative Example 2 (single PDA layer) was improved to about 650 hours, which proved the positive role of the PDA layer in improving the uniformity of zinc deposition, but its limited mechanical strength still could not meet the requirements of long-term cycling.

[0107] from Figure 6 A comparison of scanning electron microscope (SEM) images of Examples 1, 1, and 2 after immersion in 2 M ZnSO4 electrolyte for 10 days shows that the composite protective layer of the present invention provides significant protection for the zinc metal anode. Specifically, as... Figure 6 As shown in Figure a, Comparative Example 1 (bare zinc) exhibited numerous porous corrosion products and obvious cracks on its surface, indicating that the unprotected zinc foil underwent severe corrosion and side reactions in the electrolyte. Figure 6 As shown in Figure b, the surface morphology of Comparative Example 2 (Zn-PDA) is improved compared to bare zinc, and the degree of corrosion is reduced. However, localized non-uniform corrosion and a small amount of deposits are still visible, indicating that although a single PDA layer can provide some protection, its protective effect is not complete. In contrast, as... Figure 6 As shown in Figure c, the surface of Example 1 (Zn-PDA@ZrO2) maintained a relatively flat and dense morphology, with only uniform and minor surface changes observed. No obvious corrosion pits or large accumulation of by-products were observed, which fully demonstrates that the PDA-ZrO2 composite protective layer can effectively block the direct contact between the electrolyte and the zinc substrate, and significantly inhibit the corrosion reaction and the generation of by-products.

[0108] In the composite protective layer system, the influence of each parameter is more significant: In Example 2, insufficient PDA polymerization time led to incomplete bottom layer coverage, resulting in a significantly lower cycle life (534 hours) compared to Example 1 (1000 hours). In Example 3, reducing the concentration of dopamine hydrochloride caused the polydopamine (PDA) bottom layer to become thinner and unevenly covered. This not only weakened its own interfacial protection for the zinc anode, but more importantly, reduced the nucleation sites required for subsequent zirconium dioxide (ZrO2) mineralization. As a result, the density of the final PDA@ZrO2 composite protective layer decreased, failing to effectively suppress zinc dendrite penetration and side reactions, thus severely impairing the long-cycle stability of the symmetric cell, with a cycle life of only 630 hours. In Example 4, excessively long mineralization time led to an excessively thick ZrO2 layer, resulting in increased interfacial impedance and Zn 2+Deposition / dissolution requires penetration through a thicker ceramic layer. While a thicker coating more effectively suppresses dendrites, it can increase overpotential, leading to decreased long-cycle stability and a reduced cycle life of 950 hours. Similarly, in Example 5, reducing the zirconium sulfate concentration meant reducing the "skeleton" material for constructing the inorganic protective layer, resulting in a sparse, thin, and discontinuous ZrO2 layer formed by mineralization. This structural defect resulted in insufficient mechanical strength of the composite coating, making it difficult to resist dendrite growth during zinc deposition and ineffective in preventing electrolyte corrosion of the zinc anode, ultimately causing rapid performance degradation of the battery during long-term cycling, with a cycle life of only 735 hours. In Example 6, due to the change of zirconium source, possibly due to nitrate (NO3) - Compared to sulfate (SO4) 2- Different coordination abilities may lead to changes in the hydrolysis rate, particle size, and morphology of ZrO2. The resulting ZrO2 layer may have weaker bonding strength with the PDA or lower density than the zirconium sulfate system, thus affecting the uniformity and long-term stability of the protective effect, reducing the cycle life to approximately 800 hours. In Example 7, the excessively acidic mineralizing solution etched the PDA substrate, further reducing the cycle life to approximately 550 hours.

[0109] Of particular note is the effect of substrate thickness: Example 8 achieved a cycle life of approximately 900 hours using a 0.05 mm thin zinc foil, demonstrating the advantages of thin substrates in promoting ion transport and mitigating volume changes. However, its performance is still limited by the total amount of zinc source and the increased side reactions caused by the increased specific surface area. In contrast, when Example 9 used a 0.2 mm thick zinc foil, the cycle life dropped to approximately 850 hours due to increased polarization and amplified volume effects.

[0110] These results collectively demonstrate that the composite protective layer of the present invention can effectively improve interface stability, but its final performance still requires finding the optimal balance between zinc source retention, kinetic characteristics, and interface stability. The parameter combination represented by Example 1 achieves optimal comprehensive performance under these multiple requirements. The above results fully demonstrate that the performance of the composite protective layer of the present invention is highly sensitive to various preparation parameters, and the process window represented by Example 1 can achieve the best synergistic protection effect of "both hard and soft" protection while comprehensively considering performance and cost.

[0111] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a PDA-ZrO2-coated zinc anode, characterized in that, Includes the following steps: S1. Zinc foil pretreatment; S2, Deposition of the polydopamine layer: S201: Prepare solution A: a weakly alkaline buffer solution, and solution B: an acidic solution of dopamine hydrochloride; The weakly alkaline buffer solution is a Tris buffer solution with a concentration of 0.08-0.12 mol / L; the concentration of dopamine hydrochloride in the acidic solution is 1-3 mg / mL. S202: Mix solution A and solution B to form a reaction solution; S203: The zinc foil pretreated in S1 is immersed in the reaction solution prepared in S202 to carry out a polymerization reaction, so that the polydopamine layer is deposited in situ on the surface of the zinc substrate. S3, mineralization growth of the zirconium dioxide layer: S301: Prepare an acidic mineralization solution containing a zirconium source, wherein the zirconium source is zirconium sulfate tetrahydrate; The mass ratio of dopamine hydrochloride to zirconium sulfate tetrahydrate is 0.05~0.1:0.07~0.14; S302: Immerse the product obtained in S2 into the acidic mineralization solution containing zirconium source described in S301 to carry out a mineralization reaction and obtain a zinc metal anode with a polydopamine-zirconia composite protective layer. The mineralization reaction time is 2-6 hours.

2. The method for preparing the PDA-ZrO2-coated zinc anode according to claim 1, characterized in that, In S1, zinc foil with a thickness of 0.05~0.2 mm is pretreated. The pretreatment method is as follows: cut the zinc foil, soak it in hydrochloric acid solution to remove the surface oxide layer, clean it, and dry it for later use.

3. The method for preparing the PDA-ZrO2-coated zinc anode according to claim 1, characterized in that, In S203, the pH of the polymerization reaction is 7-9, the reaction temperature is 30-50℃, and the reaction time is 1-4 hours.

4. The method for preparing the PDA-ZrO2-coated zinc anode according to claim 1, characterized in that, In S301, the method for preparing the acidic mineralization solution containing zirconium source is as follows: the zirconium source is dissolved in hydrochloric acid solution.

5. The method for preparing the PDA-ZrO2-coated zinc anode according to claim 1, characterized in that, In S301, the pH of the acidic mineralization solution containing the zirconium source is 0.7-1.

6. The method for preparing the PDA-ZrO2-coated zinc anode according to claim 1, characterized in that, In S302, the temperature of the mineralization reaction is 25-45℃.

7. The PDA-ZrO2-coated zinc anode prepared by the method for preparing the PDA-ZrO2-coated zinc anode according to any one of claims 1 to 6, characterized in that, The zinc anode comprises a zinc substrate and a polydopamine-zirconia composite protective layer formed on the surface of the zinc substrate; the composite protective layer consists of a polydopamine flexible underlayer and zirconia nanoparticles distributed thereon.

8. A battery, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is a zinc anode prepared by the method for preparing a PDA-ZrO2-coated zinc anode according to any one of claims 1 to 6 or a zinc anode according to claim 7.

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