A water-based zinc-ion battery anode with a copper oxalate coating and its preparation method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-17
- Publication Date
- 2026-08-14
AI Technical Summary
然而，电解液改性策略仍面临长效性不足的问题，添加剂在循环过程中易消耗分解，高浓度添加可能引发电导率下降和成本上升问题，且难以从根本上抑制电极结构的宏观形变
[0021]利用本发明的技术方案制作的一种具有草酸铜涂层的水系锌离子电池负极及其制备方法，引导锌均匀沉积：由于铜具备较高的导电性，有利于改善电极内部的电子传输效率；铜离子(Cu2+)还具有较强的亲锌性，能够增强对锌沉积行为的亲和调控能力；草酸铜的溶解度相对较低，这使得其在电极表面更易于形成稳定且均匀的涂层，抑制枝晶生长。
Smart Images
Figure CN122576128A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aqueous zinc-ion batteries, and in particular to an aqueous zinc-ion battery anode with a copper oxalate coating and its preparation method. Background Technology
[0002] With the continuous innovation of energy technology, battery energy has become an indispensable key component of modern society's production and daily life. However, traditional lithium batteries have significant safety hazards during use, such as the risk of fire and explosion due to thermal runaway, which restricts the expansion of their application scenarios. Therefore, developing new batteries with excellent safety performance has become an important issue that urgently needs to be addressed in the current energy field.
[0003] Aqueous zinc-ion batteries offer a new direction for addressing the safety concerns of traditional batteries due to their unique technological advantages: First, by using an aqueous electrolyte system, they fundamentally avoid the flammability and explosion risks associated with organic electrolytes, significantly improving safety. Second, zinc is abundant in nature and inexpensive to obtain, effectively reducing the cost of large-scale production and application. Based on these advantages, aqueous zinc-ion batteries possess broad development prospects and application potential, and are expected to achieve technological breakthroughs and large-scale applications in more fields in the future.
[0004] However, the development of aqueous zinc-ion batteries still faces key bottlenecks: During charging and discharging, zinc ions are unevenly deposited on the negative electrode surface, easily forming dendritic zinc dendrites. Dendrite growth may pierce the separator, leading to internal short circuits and battery failure. This results in irreversible loss of active material and capacity decay. The hydrogen evolution overpotential of the zinc negative electrode is low, especially in neutral or weakly acidic electrolytes, making it prone to hydrogen evolution side reactions that consume electrolyte and active material, generating gas that increases internal battery pressure, causes expansion, and may even lead to leakage and damage to electrode interface stability. Zinc is chemically reactive in aqueous electrolytes and spontaneously reacts with water to produce hydrogen gas. The generated Zn(OH)2 can also react with ZnSO4 in the electrolyte to produce Zn4(OH)6SO4 and other products that form a passivation layer on the electrode surface, increasing interfacial impedance and affecting the battery's rate performance and capacity release.
[0005] To address the aforementioned issues, researchers both domestically and internationally have proposed various solutions from the perspectives of electrolyte modification and the construction of artificial interface protective layers. For example, Shao et al. used hexafluoroacetylacetone (HFAT) as an electrolyte additive to form a stable [Zn(H2O)5HFAT]0. 2+ The solvated shell reduces the activity of interfacial water and promotes the desolvation of zinc ions. The assembled Zn||Zn symmetric cell operates at 1 mA cm⁻¹. −2 and 1 mAh cm −2Under certain conditions, it can maintain a service life of up to 1700 hours. Yu et al. used methacrylic acid (MAA) as an electrolyte additive, and MAA molecules formed a water-deficient internal Helmholtz plane on the zinc anode surface. This interface modification effectively suppressed side reactions and promoted the uniform directional deposition of zinc towards (002). However, electrolyte modification strategies still face the problem of insufficient long-term effectiveness. Additives are easily consumed and decomposed during cycling, and high-concentration addition may lead to a decrease in conductivity and an increase in cost. Moreover, it is difficult to fundamentally suppress the macroscopic deformation of the electrode structure. Therefore, the research focus has gradually shifted to the direction of anode interface modification with greater structural control capabilities, and to achieve more durable interface stability by constructing an artificial protective layer on the zinc surface.
[0006] Interface modification typically employs artificially constructed physical or chemical coatings to fundamentally isolate the zinc anode from direct contact with the electrolyte. Based on this, this invention provides an aqueous zinc-ion battery anode with a copper oxalate coating and its preparation method. Specifically, a 20 µm thick insoluble copper oxalate coating is constructed on the surface of the zinc anode using a roll forming process, resulting in a composite electrode denoted as Zn@CuC2O4-20. This coating effectively inhibits dendrite growth and hydrogen evolution reaction, and improves corrosion resistance, thereby significantly extending the cycle life of the zinc-ion battery. Summary of the Invention
[0007] The purpose of this invention is to solve the above-mentioned problems by designing an aqueous zinc-ion battery anode with a copper oxalate coating and its preparation method.
[0008] The technical solution of the present invention to achieve the above objectives is a water-based zinc-ion battery negative electrode with a copper oxalate coating and a method for preparing the same, comprising a zinc foil substrate;
[0009] And a copper oxalate-based composite coating disposed on the surface of the zinc foil substrate;
[0010] The thickness of the copper oxalate-based composite coating is 10-40 µm;
[0011] The copper oxalate-based composite coating comprises copper oxalate dihydrate (CuC2O4·2H2O), a conductive agent, and a binder.
[0012] Preferably, in the copper oxalate-based composite coating, the mass percentages of copper oxalate dihydrate, conductive agent, and binder are: 80% copper oxalate dihydrate, 10% conductive agent, and 10% binder.
[0013] Preferably, the zinc foil has a thickness of 10 µm, the copper oxalate-based composite coating has a thickness of 20 µm, the conductive agent is conductive carbon black, and the binder is PVDF.
[0014] This invention also provides a method for preparing an aqueous zinc-ion battery negative electrode with a copper oxalate coating, comprising the following steps:
[0015] Step 1: Weigh 6.0-7.0 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) powder using an analytical balance, dissolve it in 80 mL of deionized water, and stir continuously until completely dissolved to obtain a blue transparent copper nitrate solution;
[0016] Step 2: Weigh 3.13-3.65 g of oxalic acid dihydrate (H2C2O4·2H2O) powder using an analytical balance, dissolve it in 80 mL of deionized water, and stir continuously until completely dissolved to obtain a colorless and transparent oxalic acid solution.
[0017] Step 3: While continuously and slowly stirring the copper nitrate solution from Step 1, slowly add the oxalic acid solution from Step 2 to the copper nitrate solution. After the reaction is complete, a blue precipitate is obtained.
[0018] Step 4: Centrifuge the precipitate obtained in Step 3. Set the centrifuge speed to 4000-6000 rpm and the time to 8-10 minutes. After washing with ethanol and drying, copper oxalate dihydrate powder, namely CuC2O4·2H2O, is obtained.
[0019] Step 5: Mix CuC2O4·2H2O, conductive carbon black, and PVDF binder from Step 4 at a mass ratio of 8:1:1, using anhydrous ethanol as the dispersion medium, and grind thoroughly to form a uniform slurry;
[0020] Step 6: Apply the slurry from Step 5 evenly to the surface of the polished zinc foil, and roll it using a double roller press. Adjust the roller spacing of the double roller press to 60-90 µm to obtain a composite electrode Zn@CuC2O4-X with a copper oxalate coating thickness of 10-40 μm, where X=10, 20, 30, 40.
[0021] This invention discloses an aqueous zinc-ion battery anode with a copper oxalate coating and its preparation method, which guides uniform zinc deposition. Because copper has high conductivity, it is beneficial to improve the electron transport efficiency inside the electrode. 2+ It also has a strong affinity for zinc, which can enhance the affinity regulation of zinc deposition behavior; copper oxalate has relatively low solubility, which makes it easier to form a stable and uniform coating on the electrode surface and inhibit dendrite growth.
[0022] Suppressing side reactions: The protective layer formed by copper oxalate and its decomposition products is dense and insoluble in water, serving as an effective physical barrier. This barrier prevents water molecules and free SO4 from entering the electrolyte. 2-By having these substances directly contact the zinc anode, the corrosion of zinc and hydrogen evolution reaction are significantly reduced, thereby improving coulombic efficiency and cycle life.
[0023] Excellent cycling stability: This study constructed a Zn@CuC2O4-20||Zn@CuC2O4-20 symmetric cell. This cell exhibits excellent cycling stability at 1 mA cm⁻¹. -2 Current density and 1 mAh cm -2 Under the specified capacitance test conditions, it exhibited excellent cycle stability, capable of continuous stable operation for up to 2000 hours. Furthermore, a Zn@CuC2O4-20||MnO2 full cell was assembled using MnO2 as the positive electrode material and Zn@CuC2O4-20 as the negative electrode material. At 1 A g... -1 Long-term cycling tests were conducted at higher current densities. After 1,000 cycles, the coulombic efficiency of the full cell was still close to 95%, which indicates that the cycle stability and lifespan of the battery have been significantly improved.
[0024] This invention employs a copper oxalate composite electrode (Zn@CuC2O4-20) as the negative electrode material, leveraging its unique crystal structure to achieve precise control over zinc deposition behavior. Oxalate ions (C2O4...) 2- The bidentate coordination ability and delocalized π-electron structure of the zinc anode can selectively adsorb onto the high-energy crystal planes of the zinc surface, synergistically promoting the dense deposition of zinc along the (002) crystal plane direction both thermodynamically and kinetically. Simultaneously, the constructed triple synergistic protection mechanism of "crystal plane induction-interface stabilization-side reaction suppression" significantly improves the deposition reversibility and interface stability of the zinc anode.
[0025] Oxalate protective layers can be prepared using a simple coating process. This method is characterized by its ease of operation and controllable process parameters, enabling precise design and optimization of coating thickness gradients. This preparation strategy is not only simple and cost-effective, but also possesses good process compatibility and scalable production potential, providing a feasible technical path for future large-scale applications. Attached Figure Description
[0026] Figure 1 Material characterization diagrams for Example 1 and Comparative Example 1: Figure 1 (a) XRD pattern of Zn@CuC2O4-20 prepared in Example 1; (b) XPS pattern of Zn@CuC2O4-20 prepared in Example 1; (c) SEM image of the symmetrical battery assembled in Example 1 as the negative electrode after cycling; (d) SEM image of the symmetrical battery assembled in Comparative Example 1 as the negative electrode after cycling.
[0027] Figure 2 The cycling test diagrams are for symmetrical batteries assembled with negative electrodes in Examples 1, 4-6 and Comparative Example 1.
[0028] Figure 3 Cyclic test diagrams for two half-cells assembled as negative electrodes, Example 1 and Comparative Example 1;
[0029] Figure 4 The graphs show the charge-discharge cycle performance of two full-cell batteries assembled as negative electrodes, namely Example 1 and Comparative Example 1. Detailed Implementation
[0030] The present invention will now be described in detail with reference to the accompanying drawings, such as... Figure 1-4 As shown, an aqueous zinc-ion battery anode with a copper oxalate coating and its preparation method are disclosed.
[0031] Example 1:
[0032] (1) Weigh 6.72 g of Cu(NO3)2·3H2O powder using an analytical balance, dissolve it in 80 mL of deionized water, and stir continuously until completely dissolved to obtain a blue, transparent copper nitrate solution. Separately weigh 3.5 g of H2C2O4·2H2O powder, dissolve it in 80 mL of deionized water, and stir continuously until completely dissolved to obtain a colorless, transparent oxalic acid solution. Slowly add the oxalic acid solution dropwise to the copper nitrate solution, and after sufficient reaction, a blue precipitate is obtained. The precipitate is then centrifuged. The centrifuge speed is set to 5000 rpm and the time is set to 9 minutes. After washing with ethanol and drying, CuC2O4·2H2O powder is obtained.
[0033] (2) The CuC2O4·2H2O powder, conductive carbon black and binder PVDF obtained in step (1) are mixed in a mass ratio of 8:1:1, and anhydrous ethanol is used as the dispersion medium. The mixture is then thoroughly ground to form a slurry.
[0034] (3) The slurry obtained in step (2) is uniformly coated on the surface of the polished zinc foil with a thickness of 10 µm. Protective paper with a thickness of 20 µm is covered on both sides. The zinc foil is rolled using a double roller press. The roller spacing of the double roller press is adjusted to 70 µm to prepare a composite electrode with a copper oxalate coating with a thickness of 20 µm, denoted as Zn@CuC2O4-20.
[0035] Example 2:
[0036] The composite electrode with a copper oxalate coating was prepared according to the method of Example 1, except that:
[0037] In step (1), 6.0 g of Cu(NO3)2·3H2O and 3.13 g of H2C2O4·2H2O were weighed.
[0038] Example 3:
[0039] The composite electrode with a copper oxalate coating was prepared according to the method of Example 1, except that:
[0040] In step (1), 7.0 g of Cu(NO3)2·3H2O and 3.65 g of H2C2O4·2H2O were weighed.
[0041] Example 4:
[0042] The composite electrode with copper oxalate coating was prepared according to the method of Example 1, except that the roller spacing of the twin-roll press was adjusted to 60 µm in step (3) to prepare a composite electrode with a copper oxalate coating with a thickness of 10 µm, denoted as Zn@CuC2O4-10.
[0043] Example 5:
[0044] The composite electrode with copper oxalate coating was prepared according to the method of Example 1, except that the roller spacing of the twin-roll press was adjusted to 80 µm in step (3) to prepare a composite electrode with a copper oxalate coating with a thickness of 30 µm, denoted as Zn@CuC2O4-30.
[0045] Example 6:
[0046] The composite electrode with copper oxalate coating was prepared according to the method of Example 1, except that the roller spacing of the double roller press was adjusted to 90 µm in step (3) to prepare a composite electrode with copper oxalate coating with a thickness of 40 µm, denoted as Zn@CuC2O4-40.
[0047] Comparative Example 1:
[0048] The zinc foil (10 µm thick) after sanding in step (3) of Example 1 was used as a comparative example, i.e., bare zinc.
[0049] Application Example 1:
[0050] The electrodes obtained in Examples 1-6 and Comparative Example 1 were punched to obtain circular electrode sheets with a diameter of 12 mm, which were used as negative electrodes. The same material was used as the positive electrode. A glass fiber membrane (GF / A, Whatman) was used as the separator, and a 2 M ZnSO4 solution was used as the electrolyte. The components were then sequentially assembled into a CR2032 button cell casing to complete the assembly of the symmetrical cell.
[0051] The electrodes were subjected to constant current charge-discharge tests using the Xinwei BTS-4000 battery testing system to evaluate their cycle stability. The current density was set to 1 mA cm⁻¹. -2 Cut-off capacity 1 mAh cm -2 .
[0052] Application Example 2:
[0053] The electrodes obtained in Example 1 and Comparative Example 1 were punched to obtain circular electrode sheets with a diameter of 12 mm, which were used as negative electrodes. Copper foil (Cu) was used as the positive electrode, and a glass fiber membrane (GF / A, Whatman) was used as the separator. A 2M ZnSO4 solution was used as the electrolyte. The components were then sequentially assembled into a CR2032 button cell casing to complete the assembly of the half cell.
[0054] The battery was subjected to constant current charge-discharge tests using the Xinwei BTS-4000 battery testing system to evaluate its coulombic efficiency, with a current density of 1 mA cm⁻¹. -2 The cutoff voltage is 1 V.
[0055] Application Example 3:
[0056] The electrodes obtained in Example 1 and Comparative Example 1 were punched to obtain circular electrode sheets with a diameter of 12 mm, which were used as negative electrodes. MnO2 was used as the positive electrode, and a glass fiber membrane (GF / A, Whatman) was used as the separator. A 2 M ZnSO4 solution was used as the electrolyte. The components were then sequentially assembled into a CR2032 button cell casing to complete the assembly of the full cell.
[0057] The battery was subjected to constant current charge-discharge tests using the Xinwei BTS-4000 battery testing system to evaluate its coulombic efficiency and capacity decay characteristics. The current density was set to 1 A g. -1 .
[0058] In this implementation plan, such as Figure 1 As shown in (a), XRD phase analysis of the prepared Zn@CuC2O4-20 composite electrode shows that the diffraction pattern of the Zn@CuC2O4-20 composite electrode includes two sets of diffraction peaks: Zn (PDF#04-0831) and CuC2O4·2H2O (PDF#48-1054), proving that the Zn@CuC2O4-20 composite electrode was successfully prepared. Figure 1 (b) shows the XPS spectra of Zn@CuC2O4-20. In the C 1s spectrum, the binding energies at 284.40 eV, 285.90 eV, and 288.80 eV represent C-C bonds, CO bonds, and OC=O bonds, respectively, with OC=O having the highest proportion. This is due to the large number of OC=O bonds in the CuC2O4 interface layer, further demonstrating the successful fabrication of the Zn@CuC2O4-20 composite electrode. Figure 1 (c) The Zn@CuC2O4-20||Zn@CuC2O4-20 symmetric cell shown in the image still exhibits a dense and uniform surface with no obvious dendrite formation after 150 h of charge-discharge cycles. In contrast, [the following image shows a different image]. Figure 1(d) After 150 h of charge-discharge cycles, Zn||Zn exhibited a large number of irregular dendrites on its surface. This is due to the presence of oxalate ions (C2O4) in the Zn@CuC2O4-20 composite electrode. 2- This preferentially induces uniform horizontal growth of zinc along the (002) crystal plane. This not only promotes the compactness and smoothness of the zinc deposit, but also effectively inhibits the growth of zinc dendrites.
[0059] Figure 2 The figures show the cycle test results of symmetrical cells assembled with Examples 1, 4-6, and Comparative Example 1 as negative electrodes. The cycle stability of the system was assessed by monitoring the voltage-time curves to observe the voltage variation trend. The Zn||Zn symmetrical cell began to exhibit short-circuit phenomena after 150 hours of cycling; while the symmetrical cells assembled with Examples 4-6 as negative electrodes all showed better cycle performance, especially the Zn@CuC2O4-20||Zn@CuC2O4-20 symmetrical cell, which exhibited the best cycle performance, reaching a cycle life of up to 2000 hours. This is because the thickness of the copper oxalate (CuC2O4) coating layer has a significant impact on the deposition behavior of the zinc negative electrode and the cycle stability of the battery. When the coating layer is too thin, it is difficult to form a continuous and uniform coverage on the electrode surface, easily resulting in localized exposed or incomplete areas, thereby inducing uneven zinc deposition and exacerbating the risk of dendrite growth. Conversely, when the coating layer is too thick, agglomeration, coagulation, or even cracking easily occurs within the coating, leading to direct contact between the zinc electrode and the electrolyte, resulting in side reactions and ultimately affecting the cycle life of the battery. Therefore, Zn@CuC2O4-20 is the composite electrode with the best overall performance.
[0060] Figure 3 The figures show the cycle test results of two half-cells assembled as negative electrodes in Example 1 and Comparative Example 1. After 100 cycles, the Zn||Cu half-cell exhibited significant performance degradation, with its coulombic efficiency dropping sharply to near zero. The Zn@CuC2O4-20||Cu half-cell, however, maintained a coulombic efficiency above 95% after 700 cycles under the same conditions, demonstrating excellent electrochemical reversibility and cycle stability. This is because oxalate ions effectively stabilize zinc deposition behavior during charge and discharge, significantly improving the deposition reversibility of the zinc negative electrode. Therefore, the coulombic efficiency of the electrode remained stable throughout the cycle. The fact that the Zn@CuC2O4-20||Cu half-cell maintained a coulombic efficiency above 95% after 700 charge-discharge cycles fully demonstrates the excellent cycle stability and electrochemical reversibility of this composite electrode.
[0061] Figure 4 Two full cells assembled using Example 1 and Comparative Example 1 as negative electrodes were tested at 1 A g. -1The graph shows the charge-discharge cycle performance test results at the specified current density. The initial discharge capacities of the two batteries are essentially the same, indicating that the copper oxalate protective coating did not significantly affect the capacity. However, the Zn||MnO2 full cell failed rapidly after approximately 200 cycles, while the Zn@CuC2O4-20||MnO2 full cell exhibited excellent cycle stability, maintaining no significant capacity decay even after more than 1000 cycles. This fully demonstrates the significant role of the Zn@CuC2O4-20 composite electrode in improving the overall cycle life of the battery.
[0062] Electrochemical tests using symmetrical cells and half-cells revealed that the copper oxalate protective layer effectively induces uniform zinc deposition on the electrode surface. Specifically, it thermodynamically suppresses the exposure of high-energy crystal planes and kinetically guides zinc nucleation and lateral growth along low-energy crystal planes (preferably the (002) plane), achieving precise control over the orientation of the zinc deposition crystals. Simultaneously, the protective layer exhibits high density, physically isolating the zinc anode from direct contact with the electrolyte, thereby significantly suppressing hydrogen evolution side reactions and corrosion. Through the synergistic effect of physical isolation and crystal orientation control, the composite electrode of this invention exhibits both excellent capacity retention and stable electrochemical reversibility during long-term cycling, effectively extending the cycle life of aqueous zinc-ion batteries.
[0063] In this embodiment, copper oxalate dihydrate (CuC2O4·2H2O) is used as the main active component of the composite electrode coating. In the electrode coating material system, the components are composed of the following by mass percentage: copper oxalate dihydrate (CuC2O4·2H2O) accounts for 80%, serving as the core functional material; conductive carbon black is selected as the conductive agent, accounting for 10%, used to construct a high-efficiency electron transport network; and PVDF is used as the binder, accounting for 10%, ensuring a strong bond and structural integrity between the coating and the current collector.
[0064] composition:
[0065] The Zn@CuC2O4-20 composite electrode provided by this invention uses zinc foil as a substrate, on which a 20 µm thick coating is constructed. This protective layer is a copper oxalate-based composite coating. The main component of this coating is copper oxalate dihydrate (CuC2O4·2H2O), accounting for 80% of the total content, serving as the main functional component of the interface protective layer. To further improve the charge transport efficiency at the electrode interface, conductive carbon black, accounting for 10% of the total content, is added. Simultaneously, to ensure the strong bond between the coating and the zinc foil substrate and its long-term cycling stability, polyvinylidene fluoride (PVDF), accounting for 10% of the total content, is added as a binder. All the above components together constitute a coating that combines protective and conductive functions.
[0066] Copper oxalate consists of a copper ion (Cu) 2+) and an oxalate ion (C2O4) 2- Copper oxalate is commonly found as a dihydrate (CuC2O4·2H2O), where one copper oxalate molecule binds to two water molecules. The crystal structure of copper oxalate is central to its function, especially in aqueous zinc-ion batteries, where its structure influences ion transport and induced deposition behavior.
[0067] Oxalate ion (C2O4) 2- As a bridging ligand, it coordinates with multiple copper ions simultaneously through its four oxygen atoms, forming an extended two-dimensional layered or one-dimensional chain-like coordination polymer structure. Copper ions (Cu...) 2+ It is located in an octahedral coordination environment of oxygen atoms. Layers or chains are stacked together by van der Waals forces or hydrogen bonds, forming molecular channels. It is typically a light blue or blue-green fine crystalline powder. Its poor solubility in water is key to its ability to serve as a protective layer in aqueous batteries. Its solubility product constant is extremely low: K0 sp (CuC2O4) ≈ 2.9 × 10 -8 .
[0068] The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.
Claims
1. A negative electrode for an aqueous zinc-ion battery with a copper oxalate coating, characterized in that, Including zinc foil substrate; And a copper oxalate-based composite coating disposed on the surface of the zinc foil substrate; The thickness of the copper oxalate-based composite coating is 10-40 µm; The copper oxalate-based composite coating comprises copper oxalate dihydrate (CuC2O4·2H2O), a conductive agent, and a binder.
2. The aqueous zinc-ion battery negative electrode with copper oxalate coating according to claim 1, characterized in that, In the copper oxalate-based composite coating, the mass percentages of copper oxalate dihydrate, conductive agent, and binder are: 80% copper oxalate dihydrate, 10% conductive agent, and 10% binder.
3. The aqueous zinc-ion battery negative electrode with copper oxalate coating according to claim 1, characterized in that, The zinc foil substrate has a thickness of 10 µm, the copper oxalate-based composite coating has a thickness of 20 µm, the conductive agent is conductive carbon black, and the binder is PVDF.
4. The method for preparing the aqueous zinc-ion battery negative electrode with a copper oxalate coating according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Weigh 6.0-7.0 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) powder using an analytical balance, dissolve it in 80 mL of deionized water, and stir continuously until completely dissolved to obtain a blue transparent copper nitrate solution; Step 2: Weigh 3.13-3.65 g of oxalic acid dihydrate (H2C2O4·2H2O) powder using an analytical balance, dissolve it in 80 mL of deionized water, and stir continuously until completely dissolved to obtain a colorless and transparent oxalic acid solution. Step 3: While continuously and slowly stirring the copper nitrate solution from Step 1, slowly add the oxalic acid solution from Step 2 to the copper nitrate solution. After the reaction is complete, a blue precipitate is obtained. Step 4: Centrifuge the precipitate obtained in Step 3. Set the centrifuge speed to 4000-6000 rpm and the time to 8-10 minutes. After washing with ethanol and drying, copper oxalate dihydrate powder, namely CuC2O4·2H2O, is obtained. Step 5: Mix CuC2O4·2H2O, conductive carbon black, and PVDF binder from Step 4 at a mass ratio of 8:1:1, using anhydrous ethanol as the dispersion medium, and grind thoroughly to form a uniform slurry; Step 6: Apply the slurry from Step 5 evenly to the surface of the polished zinc foil, and roll it using a two-roll press. Adjust the gap between the rollers of the two-roll press to 60-90 µm to obtain a composite electrode Zn@CuC2O4-X with a copper oxalate coating thickness of 10-40 µm, where X=10, 20, 30, 40.