Zinc negative electrode, method for preparing the same, and aqueous zinc-based electrochemical energy storage device

Abstract

The application discloses a zinc negative electrode, a preparation method thereof and a water-based zinc-based electrochemical energy storage device. The zinc negative electrode comprises a negative electrode substrate formed by metal zinc and a tungsten oxide protective layer; the tungsten oxide protective layer is formed by in-situ electrochemical reaction of metal zinc and tungsten acid root. The preparation method comprises the following steps: providing a negative electrode substrate; contacting with a reaction solution and generating in-situ electrochemical reaction to deposit a tungsten oxide protective layer, thereby obtaining a zinc negative electrode; wherein the reaction solution contains tungsten acid root. The zinc negative electrode provided by the application has excellent corrosion resistance, can significantly reduce the occurrence of water-induced side reactions in an acidic electrolyte, avoid additional zinc loss, improve the coulomb efficiency and utilization rate of the zinc negative electrode; and the polarization degree of the zinc negative electrode is low, and a strong interaction of chemical bond is formed between the protective layer and the metal zinc, so that the electrochemical energy storage device composed of the zinc negative electrode provided by the application has excellent electrochemical kinetic performance and cycle performance.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, and in particular to a zinc anode, its preparation method, and an aqueous zinc-based electrochemical energy storage device. Background Technology

[0002] The zinc anode has a high electrode potential (-0.76V vs SHE) and a high specific capacity (820mAh g). -1 The inherent safety and low cost of zinc make it a good and widely used material in the field of zinc-based energy storage in water systems. However, zinc anodes often have low cycle life and suffer from problems such as self-corrosion and hydrogen evolution, which seriously limit their practical application and further development.

[0003] To address these issues, it is necessary to understand the electrochemical behavior of the zinc anode itself. Studies have shown that zinc metal is thermodynamically unstable in mainstream weakly acidic aqueous electrolytes and spontaneously reacts with water, resulting in self-corrosion. The specific process is as follows:

[0004] Zn + 2H₂O → Zn(OH)₂ + H₂ (spontaneous reaction)

[0005] 3Zn(OH)2 + ZnSO4·xH2O → Zn4SO4(OH)6·xH2O (self-corrosion)

[0006] These basic salt byproducts accumulate on the surface, further hindering the reaction between the electrode and the electrolyte and leading to electrode deactivation. In practice, the uneven composition and structure of the zinc metal surface (impurities, crystal planes, and irregular morphology), as well as the uneven stress from machining, cause the formation of micro-cells, resulting in microscopic electrochemical corrosion, which often starts locally and gradually spreads to the whole. These side reactions cause additional zinc loss, reducing the coulombic efficiency and utilization of the zinc anode.

[0007] Furthermore, during the deposition of the zinc anode, the initial zinc ions tend to accumulate at the protrusions on the electrode surface, followed by initial nucleation. Under limited two-dimensional diffusion control, these ions continuously stack and grow, resulting in dendrites. This phenomenon is exacerbated during continuous charge-discharge cycles, leading to uncontrolled dendrite growth and ultimately causing battery short circuits and failures, significantly shortening the cycle life of the zinc anode.

[0008] To address these issues, current technologies primarily focus on the electrode-electrolyte interface, constructing a water-oxygen barrier to reduce water-induced side reactions. These artificial interfaces are mostly created on zinc metal surfaces through coating or spin-coating methods, often employing organic materials that strongly interact with water, including gel molecular chains (polyacrylonitrile, polyvinyl alcohol, ionic liquid gels, etc.), organic molecules with polar groups (gelatin, zinc oxalate, etc.), and hydrophobic coatings (polystyrene, perfluoropolyether, etc.). However, this strong interaction with water weakens ion transport efficiency, significantly restricts electrode kinetics, exhibits pronounced polarization, and in most cases, only supports long-term charge-discharge cycles with low currents (<1 mA cm⁻¹). -2 However, it is difficult to guarantee stable cycling under high current. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a zinc anode, its preparation method, and an aqueous zinc-based electrochemical energy storage device.

[0010] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0011] In a first aspect, the present invention provides a zinc negative electrode, comprising a negative electrode substrate formed of at least metallic zinc and a tungsten oxide protective layer disposed on the surface of the negative electrode substrate;

[0012] The tungsten oxide protective layer is formed by an in-situ electrochemical reaction between metallic zinc and tungstate in the negative electrode substrate.

[0013] Secondly, the present invention also provides a method for preparing a zinc negative electrode, comprising:

[0014] A negative electrode substrate is provided, said negative electrode substrate being formed of at least metallic zinc;

[0015] The negative electrode substrate is brought into contact with the reaction solution and an in-situ electrochemical reaction occurs, and a tungsten oxide protective layer is deposited on the surface of the negative electrode substrate to obtain a zinc negative electrode;

[0016] The reaction solution contains tungstate ions.

[0017] Thirdly, the present invention also provides an aqueous zinc-based electrochemical energy storage device, comprising a positive electrode, an electrolyte, and a negative electrode in sequential contact, wherein the negative electrode is selected from the aforementioned zinc negative electrode.

[0018] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least the following:

[0019] The zinc anode provided by this invention has excellent corrosion resistance, can significantly reduce water-induced side reactions in acidic electrolytes, avoid additional zinc loss, and improve the coulombic efficiency and utilization rate of the zinc anode. Moreover, the zinc anode has low polarization, and the interaction between the protective layer and metallic zinc is a strong chemical bond. Therefore, the electrochemical energy storage device composed of the zinc anode provided by this invention has excellent electrochemical kinetic performance and cycle performance.

[0020] The above description is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described below in conjunction with detailed drawings. Attached Figure Description

[0021] Figure 1 This is a schematic flowchart of a zinc anode preparation method provided in a typical embodiment of the present invention;

[0022] Figure 2a These are surface optical photographs of a pure zinc sheet and a zinc negative electrode provided in a typical embodiment and a blank example of the present invention;

[0023] Figure 2b These are surface Raman signal characterization diagrams of a pure zinc sheet and a zinc negative electrode provided in a typical embodiment and a blank example of the present invention;

[0024] Figure 2c This is an electron microscope image of the surface morphology of a zinc anode provided in a typical embodiment of the present invention;

[0025] Figure 2d This is a cross-sectional electron microscope image and cross-sectional elemental distribution test diagram of a zinc anode provided in a typical embodiment of the present invention;

[0026] Figure 2e This is a surface electron microscope image of a magnetron sputtered zinc anode provided in a typical comparative application case of the present invention;

[0027] Figure 3a This is a typical embodiment of the present invention, showing the test results of the zinc anode cycling performance under different current densities and different areal capacities.

[0028] Figure 3b This is a cycle performance test diagram of the zinc anode provided in a typical comparative case of the present invention;

[0029] Figure 3c This is a cycle performance test chart of the zinc anode provided in another typical comparative case of the present invention.

[0030] Figure 4 These are optical characterization images of the cross-sectional deposition process of pure zinc sheet and zinc anode provided in a typical embodiment and blank case of the present invention;

[0031] Figure 5a These are SEM images of the surface morphology of pure zinc sheet and zinc negative electrode after corrosion, provided in a typical embodiment and a blank example of the present invention.

[0032] Figure 5b These are XRD diffraction patterns of pure zinc sheet and zinc anode before and after corrosion, provided in a typical embodiment and blank case of this invention.

[0033] Figure 5c These are polarization curves of a pure zinc sheet and a zinc negative electrode provided in a typical embodiment and a blank example of the present invention;

[0034] Figure 5d These are hydrogen evolution curves of pure zinc sheet and zinc negative electrode provided in a typical embodiment and blank case of the present invention. Detailed Implementation

[0035] Some existing zinc anode protection interfaces use hydrophobic polymer or organic coatings to protect the zinc anode. However, the inventors of this invention have found in practice that the above-mentioned technical solutions generally have the following technical defects:

[0036] 1) Dendrite problems can only be alleviated at relatively low currents. In high current applications (>1mA cm⁻¹),... -2 ), large capacity applications (>4mAh cm⁻¹) -2 Even so, the cycle life will still be greatly reduced.

[0037] 2) Existing coating technologies often sacrifice kinetic performance while inhibiting corrosion. At the same time, the strong barrier effect on solvent water reduces the conduction of zinc ions and sacrifices the electrochemical activity of the electrode.

[0038] 3) Coatings prepared by methods such as coating and spin coating are generally constrained on the zinc anode surface by van der Waals forces and hydrogen bonds, which are weak interactions. They are difficult to adapt to the deformation caused by the deposition / dissolution of zinc with high areal capacity, and are prone to peeling or deformation of the protective layer, which in turn affects the performance and life of the battery.

[0039] 4) Some coating raw materials have complicated synthesis steps and high costs, making them difficult to promote and use; the raw materials contain toxic substances (such as benzene, ethers, fluorides, etc.), which contradicts the green and environmentally friendly concept of water system energy storage and runs counter to the concept of sustainable development.

[0040] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0041] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0042] The first aspect of the present invention provides a zinc anode, comprising an anode substrate formed at least of metallic zinc and a tungsten oxide protective layer disposed on the surface of the anode substrate; wherein the tungsten oxide protective layer is formed by an in-situ electrochemical reaction between metallic zinc and tungstate in the anode substrate.

[0043] In some embodiments, the thickness of the tungsten oxide protective layer is <100 nm. Because the tungsten oxide film provided by this invention is extremely thin, traditional XRD characterization failed to reveal relevant crystal structure information. Considering the nanometer-scale thickness, it is presumed that it does not possess a complete crystal structure and should be in an amorphous state. Meanwhile, SEM images show that the surface of the tungsten oxide layer is generally dense and smooth, but a small number of defects and cracks still exist. Furthermore, cross-sectional mapping results show that the zinc element distribution in this layer is low, indicating a small amount of zinc doping. Although this level of doping is low, it still promotes zinc ion conduction, and its electrochemical reaction characteristics differ from those of a pure tungsten oxide film without zinc ion doping.

[0044] Furthermore, the interface mapping diagram shows that the zinc ion doping concentration gradually decreases from the substrate to the surface, which is a typical characteristic of the film formed by the in-situ electrochemical reaction method used in this invention.

[0045] Based on the above protective layer structure, in the electrochemical reaction, 2) the polarization degree of tungsten oxide-zinc does not increase significantly, thus improving the kinetic performance. This protective layer weakens the surface energy of the electrolyte-electrode interface, realizing uniform zinc ion diffusion and nucleation processes, ultimately leading to a uniform and flat zinc deposition morphology, further improving the reversibility of the zinc anode cycle, and exhibiting a high hydrogen evolution potential and the generation of a hydrogen adsorption platform. This allows the protective layer to suppress the generation of hydrogen evolution side reactions. In addition, a corrosion-resistant tungsten oxide layer is constructed on the zinc sheet surface using an in-situ redox method. This protective layer forms chemical bonds with zinc metal, exhibiting strong interactions, and can adapt to the deformation caused by the high areal capacity of zinc deposition / dissolution.

[0046] Therefore, in some implementations, the zinc anode exhibits corrosion resistance in weakly acidic concentrated electrolytes (electrolyte concentration > 0.5 M) for more than 40 days. Related information on hydrogen evolution parameters can be found in... Figure 5c In d, the weak acid concentrated electrolyte includes 10 -1 mAcm -2 Corrosion current density, compared with bare zinc (101 mA cm -2 Compared to the bare zinc electrode, it is an order of magnitude lower, and the hydrogen evolution potential is also lower (the difference is 57mV).

[0047] See Figure 1 As shown, a second aspect of the present invention also provides a method for preparing a zinc negative electrode, comprising the following steps:

[0048] A negative electrode substrate is provided, said negative electrode substrate being formed of at least metallic zinc.

[0049] The negative electrode substrate is brought into contact with the reaction solution to undergo an in-situ electrochemical reaction, and a tungsten oxide protective layer is deposited on the surface of the negative electrode substrate to obtain a zinc negative electrode.

[0050] The reaction solution contains tungstate ions.

[0051] In the preparation scheme provided by this invention, in-situ electrochemical reaction is particularly preferred to deposit and form a tungsten oxide protective layer. This is because, compared with the deposition method of simply depositing tungsten oxide such as physical deposition, on the one hand, the morphology of the formed tungsten oxide layer is more suitable for the electrochemical reaction of the zinc anode; on the other hand, in the in-situ electrochemical deposition, zinc oxidation occurs on the surface of the zinc anode, forming zinc ions. This not only makes the contact between the tungsten oxide protective layer and the zinc anode substrate better, but also allows the free zinc ions formed by oxidation to be doped into the tungsten oxide, forming a composite metal oxide. Experiments have shown that the protective layer structure formed in this way has a more superior performance.

[0052] Specifically, this in-situ chemical method relies on the redox differences of the material itself and does not involve external energy supply (compared to traditional energy-intensive processes such as electroplating, hot-dip galvanizing, and electrostatic spraying). It is green, energy-saving, and simple in process.

[0053] The protective layer prepared by this in-situ chemical method has a thickness of nanometers, which greatly reduces the complexity of operation compared to commonly used micro-nano fabrication processes such as magnetron sputtering, electron beam evaporation, and thermal evaporation.

[0054] In the in-situ chemical reaction method, the zinc substrate and the protective layer will form a strong bond, and the tungsten oxide protective layer will have better contact with the zinc anode substrate. At the same time, a small amount of free zinc ions formed by oxidation can be doped into the tungsten oxide to form a composite metal oxide. In the experiment, it was found that the protective layer structure formed in this way has better electrochemical performance (the control group is the tungsten oxide layer sputtered by magnetron sputtering, with a thickness of 100 nanometers).

[0055] In some embodiments, the concentration of tungstate in the reaction solution is preferably 0.5-10 mmol / L. The inventors have found that higher concentrations result in faster reactions, thicker passivation layers, and surface cracking, leading to poorer electrochemical performance. Therefore, this invention preferably uses a low-concentration reaction solution to control the morphology of the formed tungsten oxide protective layer.

[0056] In some embodiments, the solute in the reaction solution includes any one or a combination of two or more of sodium tungstate, potassium tungstate, and phosphotungstic acid.

[0057] In some embodiments, the in-situ electrochemical reaction is preferably carried out at a temperature of 25-60°C and for a time of 10 min-12 h. The inventors have also found that higher temperatures and longer times accelerate the reaction rate and amount, leading to an increased passivation layer thickness but also resulting in a cracked morphology and poor electrochemical performance. Therefore, the reaction conditions are also controlled in preferred embodiments.

[0058] However, it should be noted that in practice, due to the large number of variables, the above reaction process is not limited to the scope of the example above. If other conditions are used to form a tungsten oxide film of equal thickness through in-situ electrochemical reaction, the same film structure can be achieved. Theoretically, it has a considerable electrochemical protection effect and battery dynamic performance. However, for the sake of controllability, this invention preferably controls the process at near room temperature and maintains a low concentration for a long time, so that a denser and more uniform passivation layer can be obtained more easily, thus achieving both electrochemical performance and corrosion resistance.

[0059] Of course, if those skilled in the art use higher temperatures or concentrations, but can accurately control the reaction time to obtain a film with the same film structure, it still falls within the scope of protection of this invention.

[0060] In some implementations, the process specifically includes: immersing the negative electrode substrate in a reaction solution, allowing it to stand to undergo the in-situ electrochemical reaction, and forming the tungsten oxide protective layer.

[0061] In some embodiments, the negative electrode substrate is polished and cleaned before being immersed in the reaction solution.

[0062] In some embodiments, the zinc anode surface is cleaned and dried after the in-situ electrochemical reaction.

[0063] As some typical application examples of the above technical solutions, the preparation method provided in the embodiments of the present invention can be implemented by the following steps:

[0064] 1) Zinc sheet preparation: Cut the zinc sheet to a size that can be placed in a container, polish the surface with sandpaper (1000 grit or higher) to remove the oxide scale, and then wash it clean with water and alcohol to serve as the negative electrode substrate.

[0065] 2) Prepare an aqueous solution of tungstate: Take a certain mass of tungstate salts with high solubility (including sodium tungstate, potassium tungstate, phosphotungstic acid, etc.) and prepare an aqueous solution of a certain concentration.

[0066] 3)Reference Figure 1 The zinc sheet prepared in step 1) is immersed in the solution prepared in step 2), and allowed to react for a period of time at a certain temperature. During this time, the solution changes color, which is the color of the reduced tungsten oxide.

[0067] 4) Once the reaction in step 3) is complete, remove the zinc sheet after the reaction, wash it with water and alcohol, and dry it to obtain a zinc negative electrode, denoted as tungsten oxide-zinc. See [link to relevant documentation]. Figure 2a .

[0068] A third aspect of the present invention provides an aqueous zinc-based electrochemical energy storage device, comprising a positive electrode, an electrolyte, and a negative electrode in sequential contact, wherein the negative electrode is selected from those provided in any of the above embodiments, or a zinc negative electrode prepared by the provided preparation method.

[0069] In some implementations, as shown in Figure 3, the aqueous zinc-based electrochemical energy storage device operates at 2 mA / cm². 2 The cycle life at current density is over 1000 cycles, at 10 mA / cm². 2 The cycle life at current density is over 450 cycles.

[0070] The technical solution of the present invention will be further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only for illustrating the present invention and do not limit the scope of the present invention.

[0071] Unless otherwise specified, the reagents, raw materials and testing equipment used in the following examples are all commercially available.

[0072] Example 1

[0073] This embodiment illustrates the preparation process of a zinc negative electrode, as detailed below:

[0074] 1) Zinc sheet preparation: Cut the zinc sheet to a size that can be placed in a container, polish the surface with sandpaper (1000 grit or higher) to remove the oxide scale, and then wash it clean with water and alcohol.

[0075] 2) Preparation of tungstate aqueous solution: Sodium tungstate, which has high solubility, is used as the tungstate. A certain mass of sodium tungstate is weighed and prepared into an aqueous solution of a certain concentration, wherein the concentration of tungstate is 5 mmol / L.

[0076] 3)Reference Figure 1 The zinc sheet prepared in step 1) is immersed in the solution prepared in step 2), and allowed to react at 45°C for 1 hour. During this time, a color change can be observed in the solution, which is the color of the reduced tungsten oxide. The protective layer formed is on the thickness of hundreds of nanometers.

[0077] 4) Once the reaction in step 3) is complete, remove the zinc sheet after the reaction, wash it with water and alcohol, and dry it to obtain a zinc negative electrode, denoted as tungsten oxide-zinc.

[0078] Optical photographs of the zinc sheet before and after preparation and the finished zinc anode are shown below. Figure 2a As shown, the surface Raman signal is as follows Figure 2b This demonstrates that tungsten oxide is fully bonded to the surface of the zinc sheet, forming a continuous protective layer.

[0079] The surface electron microscopy morphology of the zinc anode is as follows: Figure 2c As shown, its surface is smooth and uniform, with a small amount of crack-like structure; its cross-section was characterized by electron microscopy and elemental mapping, as shown in the figure. Figure 2d As shown, the film has a thickness on the order of hundreds of micrometers and is mainly composed of WO3, but it is also obviously doped with a small amount of zinc. This film structure is unique to the embodiments of the present invention.

[0080] Compare with Example 1

[0081] In this comparative example 1, a pure zinc sheet of the same size and thickness as in example 1 was used as the zinc negative electrode.

[0082] Example 2

[0083] This embodiment illustrates the application of the zinc negative electrode prepared in Example 1 above in an aqueous zinc-based electrochemical energy storage device and the electrode performance testing process, as detailed below:

[0084] An electrochemical battery is constructed with a positive electrode, an electrolyte, and a negative electrode. The positive electrode can be manganese oxide-based (high voltage), vanadium oxide-based (high capacity), or Prussian blue-based (high rate). The electrolyte is an aqueous electrolyte with components and concentrations (concentration > 1M) of simple zinc salts, including zinc sulfate, zinc chloride, and zinc acetate, or organic anionic zinc salts, including zinc trifluoromethanesulfonate. In this embodiment, a combination of manganese dioxide positive electrode and zinc sulfate electrolyte is used. The negative electrode is the zinc negative electrode prepared in Example 1 above, and the tungsten oxide protective layer of the negative electrode is in contact with the electrolyte.

[0085] Using pure zinc sheets as a blank control, batteries of different capacities were prepared and subjected to cyclic charge-discharge tests at different current densities, as detailed below. Figure 3a As shown, from Figure 3a As can be seen, the charge-discharge cycle life of the pure zinc sheet electrode without tungsten oxide protective layer is significantly weaker than that of the tungsten oxide-zinc electrode under small capacity and low current density. Furthermore, under the condition of increased capacity and current density, the pure zinc sheet electrode without tungsten oxide protective layer exhibits a more obvious cycle life degradation phenomenon, achieving dendrite-free stable cycling under different current densities and different areal capacities, and greatly extending the cycle life compared with the unprotected zinc sheet.

[0086] In the electrochemical reaction, the cross-section of the zinc anode was optically characterized at different times, and the characterization results are as follows: Figure 4 As shown, when zinc is deposited on the surface of the tungsten oxide-zinc electrode, the protective layer weakens the surface energy of the electrolyte-electrode interface, enabling uniform zinc ion diffusion and nucleation processes, ultimately resulting in a uniform and flat zinc deposition morphology, which further improves the reversibility of the zinc anode cycle.

[0087] Furthermore, this embodiment also tested the corrosion resistance of the zinc anode itself to the battery environment. All tests used 2M ZnSO4 as a generally representative weakly acidic aqueous electrolyte. Other details, such as temperature, can be adjusted according to the battery's operating environment. Figures 5a-5b As shown, in a 40-day weak acid electrolyte corrosion test, no obvious corrosion products were found on the surface of the modified zinc sheet, and its XRD test pattern did not show any significant changes, demonstrating excellent corrosion resistance.

[0088] For electrode polarization testing ( Figure 5c This also shows that the polarization degree of tungsten oxide-zinc oxide did not increase significantly, which improved the kinetic performance of the battery; in addition, in the hydrogen evolution experiment (such as... Figure 5d As shown in the figure, tungsten oxide-zinc oxide also exhibits a high hydrogen evolution potential and the formation of a hydrogen adsorption platform, which enables the protective layer to suppress the generation of hydrogen evolution side reactions.

[0089] In addition, the above embodiments use in-situ oxidation-reduction to construct a corrosion-resistant tungsten oxide layer on the zinc sheet surface. This protective layer forms chemical bonds with zinc metal, which is a strong interaction and can adapt to the deformation caused by the deposition / dissolution of zinc with high areal capacity. This is another favorable factor for improving battery life.

[0090] Furthermore, the above-mentioned main liquid-phase reaction processes are simple to operate, have few variables, and are highly controllable, making them suitable for mass production; all reagents used in the preparation process are low-toxicity and non-toxic, and the aqueous solutions also meet the policy requirements of green environmental protection and low energy consumption.

[0091] Compare with Example 2

[0092] This comparative example illustrates an implementation scheme in the prior art that uses a polymer coating for zinc anode protection, as detailed below:

[0093] Similar to Example 1, a polystyrene coating with a thickness of micrometers is formed on the same zinc anode substrate surface by spin coating, and the coating is combined to form a zinc anode.

[0094] The zinc anode prepared in this comparative example exhibits the same level of resistance to self-corrosion as the zinc anode provided in Example 1. However, the polystyrene coating significantly affects the electrochemical dynamics of the electrode. The PS coating makes it difficult to transfer zinc ions, increasing the internal resistance, specifically manifested in:

[0095] 1. Under high current density conditions, the cycle life of the negative electrode provided in this comparative example showed a significant decrease, at 1 mAh / cm². 2 Capacity and 2mA / cm 2 At current density, the maximum number of cycles decreased to 50; at 10 mAh / cm³ 2 Capacity and 10mA / cm 2 At the current density, achieving stable cycling is extremely difficult. Its cycling performance testing is as follows: Figure 3b As shown.

[0096] Compare with Example 3

[0097] This comparative example demonstrates an implementation scheme for forming a tungsten oxide protective layer using a physical deposition method, as shown below:

[0098] Zinc sheets of the same size and thickness were processed using the same method as in Example 1, and then placed in a sputtering apparatus to physically deposit a tungsten oxide film approximately 100 nanometers thick, forming a zinc anode. Macroscopically, it also appears blue; microscopically, it is relatively smooth and exhibits an amorphous tungsten oxide layer. Electron micrographs are shown below. Figure 2e As shown.

[0099] The zinc anode prepared by this method has a tungsten oxide protective layer that is not formed by in-situ electrochemical reaction deposition. Therefore, the interface between the protective layer and the zinc sheet, as well as the microstructure in the protective layer, are somewhat different from those in Example 1.

[0100] However, when using the zinc anode provided in this comparative example, and preparing an aqueous zinc-based electrochemical energy storage device using the same method as in Example 2, its kinetic performance is weaker than that of Example 1. Specifically, at 1 mAh / cm², the kinetic performance is: 2 Capacity and 2mA / cm 2 At current density, the maximum number of cycles decreased to 64; at 10 mAh / cm³ 2 Capacity and 10mA / cm 2At current densities, stable cycling is difficult to achieve. Its cycling performance testing is as follows: Figure 3c As shown.

[0101] Example 3

[0102] The preparation process of the zinc negative electrode in Example 1 of this embodiment is largely the same as that in Example 1, with the main difference being:

[0103] In step 2), the solute of the prepared solution is phosphotungstic acid, and the equivalent concentration of tungstate in the solution is 5 mmol / L.

[0104] In step 3), the temperature of the in-situ electrochemical reaction was adjusted to 25°C and the time was adjusted to 10 min, resulting in a final film thickness of 88 nm.

[0105] The zinc anode prepared in this example was used to prepare a battery using the same preparation method as in Example 2, and the same electrode corrosion resistance, polarization and hydrogen evolution performance tests were performed. It was found that the zinc anode prepared in Example 3 had the same level of performance as in Example 1.

[0106] Example 4

[0107] The preparation process of the zinc negative electrode in Example 1 of this embodiment is largely the same as that in Example 1, with the main difference being:

[0108] In step 2), the solute of the prepared solution is potassium tungstate, and the equivalent concentration of tungstate ions in the solution is 0.5 mmol / L.

[0109] In step 3), the temperature of the in-situ electrochemical reaction was adjusted to 60°C and the time was adjusted to 12 hours, resulting in a final film thickness of 90 nm.

[0110] The zinc anode prepared in Example 4 was used to prepare a battery using the same preparation method as in Example 2, and the same electrode corrosion resistance, polarization and hydrogen evolution performance tests were performed. It was found that the zinc anode prepared in Example 4 had the same level of performance as in Example 1.

[0111] Based on the above embodiments and comparative examples, it is clear that the zinc anode provided by the present invention has excellent corrosion resistance, can significantly reduce the occurrence of water-induced side reactions in acidic electrolytes, avoid additional zinc loss, and improve the coulombic efficiency and utilization rate of the zinc anode; moreover, the zinc anode has low polarization, and the protective layer and metallic zinc form a strong chemical bond interaction. Therefore, the electrochemical energy storage device composed of the zinc anode provided by the present invention has excellent electrochemical kinetic performance and cycle performance.

[0112] Specifically, this manifests as follows:

[0113] 1) Based on the reducing properties of zinc metal (easily loses electrons) and the precursor of zinc oxide (easily gains electrons), this invention proposes an in-situ protective layer construction method.

[0114] 2) The embodiments of the present invention significantly improve the corrosion resistance of the zinc anode and also suppress the generation of side reactions.

[0115] 3) This protective layer enables a uniform zinc deposition process, thereby solving the dendrite problem and supporting stable cycling with high current density and large area capacity.

[0116] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A zinc negative electrode characterized in that, The negative electrode substrate is formed at least by metal zinc, and a tungsten oxide protective layer is arranged on the surface of the negative electrode substrate. The tungsten oxide protective layer is formed by in-situ electrochemical reaction of metal zinc in the negative electrode substrate and tungstate ions.

2. The zinc negative electrode of claim 1, wherein, The tungsten oxide protective layer is doped with zinc ions and has a thickness less than 100 nm.

3. The zinc negative electrode of claim 1, wherein, The corrosion resistance time of the zinc negative electrode in weak acid electrolyte is more than 40 days, and the zinc negative electrode has a corrosion current density of 10 -1 mA cm -2 The following corrosion current density.

4. A method for producing a zinc negative electrode, characterized by, The method comprises: providing a negative electrode substrate formed at least by metal zinc; contacting the negative electrode substrate with a reaction solution to form an in-situ electrochemical reaction and deposit a tungsten oxide protective layer on the surface of the negative electrode substrate to obtain a zinc negative electrode; The reaction solution contains tungstate ions.

5. The preparation method according to claim 4, characterized in that, The concentration of tungstate ions in the reaction solution is 0.5-10 mmol / L. The solutes in the reaction solution include any one or a combination of two or more of sodium tungstate, potassium tungstate and phosphotungstic acid.

6. The preparation method according to claim 4, characterized in that, The in-situ electrochemical reaction is carried out at a temperature of 25-60°C for 10 min-12 h.

7. The production method according to claim 4, characterized by, The method specifically comprises: immersing the negative electrode substrate in the reaction solution and allowing the in-situ electrochemical reaction to occur to form the tungsten oxide protective layer.

8. The preparation method according to claim 7, characterized in that, The negative electrode substrate is polished and cleaned before being immersed in the reaction solution. The surface of the zinc negative electrode is cleaned and dried after the in-situ electrochemical reaction.

9. An aqueous zinc-based electrochemical energy storage device comprising, in sequence, a positive electrode, an electrolyte and the zinc negative electrode according to any one of claims 1-3.

10. The aqueous zinc-based electrochemical energy storage device of claim 9, wherein, The aqueous zinc-based electrochemical energy storage device has a cycle life of over 1000 times at 2 mA / cm 2 2 mA / cm 2 450 times at 10 mA / cm

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