PDA-ZrO2 coated zinc anode, preparation method thereof and battery

Abstract

The invention provides a PDA-ZrO2 coated zinc anode, a preparation method thereof and a battery, and belongs to the technical field of electrochemical energy storage materials. According to the zinc anode, a polydopamine-zirconium dioxide composite protective layer is constructed on the surface of a zinc substrate. According to the composite layer, a polydopamine bottom layer is formed through self-polymerization of dopamine on the surface of the zinc foil, and then a zirconium dioxide layer is introduced on the polydopamine bottom layer through an in-situ mineralization method. The PDA-ZrO2 composite layer disclosed by the invention has the main advantages that the PDA-ZrO2 composite layer ingeniously combines the strong adhesive force, excellent flexibility and ion regulation and control capability of polydopamine and the high mechanical strength and chemical stability of zirconium dioxide. The synergistic effect of'soft and hard combination 'can effectively homogenize zinc ion flow, inhibit dendritic crystal growth and block side reaction caused by water molecules, so that the interface stability of the zinc metal anode is remarkably improved, and the cycle life of the zinc metal anode is remarkably prolonged. The preparation method is simple in process, mild in condition and easy for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical energy storage materials, and particularly relates to a modified zinc metal anode for a water-based zinc ion battery, in particular to a PDA-ZrO2 coated zinc anode and a preparation method thereof and a battery. BACKGROUND

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

[0003] With large-scale renewable energy grid connection and rapid popularization of portable electronic devices, it is an urgent need to develop safe, low-cost and environmentally friendly energy storage systems. Among various candidate technologies, water-based zinc ion batteries are considered as one of the ideal choices for the next generation of large-scale energy storage due to their outstanding advantages such as abundant zinc resources, high theoretical volume capacity (5855 mAh cm -3 ), intrinsic safety (use of non-flammable aqueous electrolyte) and environmental friendliness. However, its commercial application is severely limited by the inherent defects of zinc metal anode, including zinc dendrite growth, hydrogen evolution and corrosion during repeated deposition / detachment during charging and discharging. The root cause of these problems lies in the unstable electrode / electrolyte interface, which cannot effectively regulate the uniform deposition of zinc ions and block the invasion of water molecules. In order to solve these problems, on the one hand, high-capacity and high-working-voltage electrode materials need to be designed and developed to improve the energy output of the battery. On the other hand, Zn 2+ uniform deposition is induced to obtain uniform morphology to achieve the purpose of inhibiting the formation of zinc dendrites.

[0004] To stabilize the zinc anode interface, the existing technology mainly focuses on electrolyte engineering, electrode structure design and interface engineering strategies. Among them, the interface engineering method of constructing an artificial protective layer is of great concern due to its simplicity, economy and direct effect. The artificial protective layer mainly includes inorganic layers (ZnSiO3, CaCO3, CeO2, ZrO2 and Al2O3, etc.) and organic polymer layers. Although the inorganic layer has high mechanical strength and can effectively physically block dendrites, its rigidity leads to poor adhesion to the zinc substrate, which is easy to peel off under cyclic stress; the organic polymer layer (such as polydopamine PDA) has good flexibility, strong adhesion and ion regulation ability, but its mechanical strength is insufficient and it is easy to degrade and rupture during long-term cycling. It can be seen that a single component protective layer is difficult to achieve an ideal balance between adhesion, mechanical strength, flexibility and chemical stability. SUMMARY

[0005] The present application aims to overcome the deficiencies of the prior art, and construct a composite protection technical scheme which can significantly improve the interface stability of zinc metal anode of aqueous zinc ion battery, and also provides a simple preparation process, mild conditions and easy to scale up method for constructing a composite protection layer which can significantly improve the interface stability of zinc metal anode of aqueous zinc ion battery.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical scheme: As a first aspect of the present application, a preparation method of PDA-ZrO2 coated zinc anode is provided, comprising the following steps: S1, zinc foil pretreatment; S2, deposition of polydopamine layer: S201: preparing solution A: weak alkaline buffer solution, and solution B: acidic solution of dopamine hydrochloride; the weak alkaline buffer solution is Tris buffer solution, and the concentration is 0.08-0.12 mol / L; the concentration of dopamine hydrochloride in the acidic solution of dopamine hydrochloride is 1-3 mg / mL; S202: mixing solution A and solution B to form a reaction solution; S203: immersing the zinc foil pretreated in S1 into the reaction solution prepared in S202 to carry out polymerization reaction, so that the polydopamine layer is deposited in situ on the surface of zinc substrate; S3, mineralization growth of zirconium dioxide layer: S301: preparing an acidic mineralization solution containing zirconium source, and the zirconium source is selected from zirconium sulfate and zirconium nitrate or its hydrate; S302: immersing the product obtained in S2 into the acidic mineralization solution containing zirconium source in S301 to carry out mineralization reaction, so as to prepare a zinc metal anode with polydopamine-zirconium dioxide composite protection layer.

[0007] Preferably, in S1, the zinc foil with a thickness of 0.05 mm-0.2 mm is pretreated, and the pretreatment method is: after cutting, the zinc foil is soaked in a hydrochloric acid solution to remove the surface oxide layer, washed, dried and ready for use. When the thickness of the zinc foil is small, its performance is limited by the total amount of zinc source and the intensified side reaction caused by the increased specific surface area; when the thickness is large, the service life is reduced due to the intensified polarization and the amplification of volume effect.

[0008] Preferably, in S203, the pH of the polymerization reaction is 7-9, the reaction temperature is 30-50 DEG C, and the reaction time is 1-4 hours. Incomplete polymerization reaction will lead to incomplete coverage of the bottom layer, resulting in reduced cycle life.

[0009] Preferably, in S301, the zirconium source is zirconium sulfate tetrahydrate.

[0010] Preferably, in S301, the acid mineralization solution containing the zirconium source is prepared by dissolving the zirconium source in a hydrochloric acid solution.

[0011] Preferably, the mass ratio of dopamine hydrochloride to zirconium sulfate tetrahydrate used in S201 and S301 is 0.05-0.1:0.07-0.14. The concentration of zirconium has a significant influence on the morphology and mechanical strength of the ZrO2 layer formed by mineralization, thereby affecting the uniformity and long-term stability of the protective effect.

[0012] Preferably, in S301, the pH of the acid mineralization solution containing the zirconium source is 0.7-1.

[0013] Preferably, in S302, the temperature of the mineralization reaction is 25-45℃, and the mineralization reaction time is 2-6 hours. Too long a mineralization time will cause the coating to increase, although it can more effectively inhibit dendrites, but may increase the overpotential, leading to a decrease in long cycle stability and cycle life.

[0014] As a second aspect of the present application, 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-zirconium dioxide composite protective layer formed on the surface of the zinc substrate; the composite protective layer is composed of a polydopamine flexible bottom layer and zirconium dioxide nanoparticles distributed thereon.

[0015] Preferably, the zirconium dioxide nanoparticles are in-situ mineralized and grown by the inducing effect of functional groups in the polydopamine layer, forming an organic-inorganic hybrid structure with the polydopamine flexible bottom layer.

[0016] As a third aspect of the present application, a battery is provided, comprising a positive electrode, a negative electrode and an electrolyte, the negative electrode being the zinc anode prepared by the preparation method of the first aspect or the zinc anode of the second aspect.

[0017] A key mechanism of the present application is that the first-formed polydopamine layer not only serves as a flexible bottom layer with strong adhesion, but its abundant functional groups (such as catechol and amine groups) can effectively adsorb Zr 4+ , thereby providing abundant active sites for the heterogeneous nucleation and growth of zirconium dioxide, ensuring the uniform distribution of zirconium dioxide nanoparticles and the firm combination with the polydopamine layer, and realizing the close compounding of the organic phase and the inorganic phase.

[0018] The composite coating provided by the application overcomes the defects in the prior art that a single-component protective layer (pure inorganic layer or pure organic layer) is difficult to balance between adhesion, mechanical strength and flexibility, a soft and hard combined composite protective layer is constructed, the flexibility and strong adhesion of the organic phase are used to buffer stress and uniform ion flow, and the high strength and stability of the inorganic phase are used to inhibit dendrite growth and side reactions, the two effects are used to solve the interface stability problem, thereby promoting the practical application of aqueous zinc ion battery technology.

[0019] Meanwhile, the preparation method provided by the application can further improve the battery performance of the zinc anode prepared by experiment comparison.

[0020] The application provides a preparation method of a polydopamine-zirconium dioxide composite protective layer for a zinc metal anode of an aqueous zinc ion battery and the prepared PDA-ZrO2 composite layer, and has the following beneficial effects compared with the prior art: (1) synergistic protection effect: the prepared PDA-ZrO2 composite layer combines the excellent adhesion, flexibility and ion conduction regulation capacity of PDA and the high mechanical strength and chemical inertness of ZrO2, realizes the synergistic protection of "soft and hard", and can effectively inhibit zinc dendrite growth and relieve side reactions at the same time; (2) simple and mild process: the preparation process provided by the application is carried out at room temperature, does not require complex equipment or high temperature and high pressure conditions, is simple to operate, has low energy consumption, has good compatibility with the existing battery electrode production process, is easy to scale up and realize large-scale application; (3) firm interface combination: the application realizes strong interaction and firm combination between the two layers by forming a PDA bottom layer and then inducing the growth of ZrO2 in a step-by-step manner, avoids the problem that the rigid inorganic layer is easy to peel off, and significantly improves the long-term cycle stability of the protective layer; (4) significant performance improvement: the Zn-PDA@ZrO2 anode prepared by the application is used in an aqueous zinc ion battery, and high coulomb efficiency, excellent rate performance and significantly prolonged cycle life can be expected.

[0021] Additional aspects and advantages of the application will be in part apparent and in part pointed out hereinafter in the specific embodiments of the application, some of which will be given in the following description. BRIEF DESCRIPTION OF DRAWINGS

[0022] The drawings accompanying the specification of the application form part hereof, serve to provide a further understanding of the application, and together with the description given below, explain the illustrative embodiments of the application and do not limit the application.

[0023] Figure 1The 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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

[0029] 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.

[0030] 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.

[0031] In some embodiments of the present invention, a method for preparing a PDA-ZrO2-coated zinc anode is provided, comprising the following steps: S1. Zinc foil pretreatment; S2. Deposition of the polydopamine layer yields the intermediate product Zn-PDA with a polydopamine layer on its surface: 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; 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, yields a zinc metal anode Zn-PDA@ZrO2 with a polydopamine-zirconia composite protective layer: 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; 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.

[0032] 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; 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] In some embodiments, in S301, the pH of the acidic mineralization solution containing the zirconium source is 0.7-1.

[0038] In some embodiments, in S302, the temperature of the mineralization reaction is 25-45°C, and the mineralization reaction time is 2-6 hours.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Example 1 This embodiment provides a method for preparing a zinc metal anode based on a polydopamine-zirconia composite coating, comprising the following steps: S1, Zinc foil pretreatment 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.

[0043] Deposition of S2 and PDA layers 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] Mineralization growth of S3 and ZrO2 layers 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.

[0048] Comparative Example 1 The clean zinc foil pretreated in step 1 of Example 1 was used directly as the bare zinc electrode in the comparative example.

[0049] Comparative Example 2 This comparative example is exactly the same as steps S1 and S2 in Example 1, but does not include step S3.

[0050] Example 2: The Influence of PDA Aggregation Time 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.

[0051] Example 3: Effect of dopamine hydrochloride concentration 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.

[0052] Example 4: Effect of ZrO2 mineralization time 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.

[0053] Example 5: Effect of Zirconium Sulfate Tetrahydrate Concentration 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.

[0054] Example 6: The Influence of Zirconium Source Type 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.

[0055] Example 7: Effect of pH value on mineralization solution 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.

[0056] Example 8: The effect of zinc foil thickness (1) 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.

[0057] Example 9: The effect of zinc foil thickness (2) 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.

[0058] Application Example 1 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.

[0059] 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.

[0060] Figure 2 X-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.

[0061] 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 3As 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.

[0062] 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.

[0063] Figure 4 The 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.

[0064] Figure 5The 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.

[0065] 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.

[0066] Table 1. Long-cycle test results of symmetric cells

[0067] 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.

[0068] 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 6As 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 selected from zirconium sulfate and zirconium nitrate or their hydrates; 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.

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 zirconium source is zirconium sulfate tetrahydrate.

5. 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.

6. The method for preparing the PDA-ZrO2-coated zinc anode according to claim 1, characterized in that, The mass ratio of dopamine hydrochloride and zirconium sulfate tetrahydrate used in S201 and S301 is 0.05~0.1:0.07~0.

14.

7. 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.

8. The method for preparing the PDA-ZrO2-coated zinc anode according to claim 1, characterized in that, In S302, the mineralization reaction temperature is 25-45℃, and the mineralization reaction time is 2-6 hours.

9. 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 8, 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.

10. 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 8 or a zinc anode according to claim 9.

Images