Manganese dioxide positive electrode and conductive protective coating of aqueous zinc ion battery and preparation method of manganese dioxide positive electrode and conductive protective coating

Abstract

The invention relates to the technical field of new energy materials, and particularly discloses a conductive protective coating of a manganese dioxide positive electrode of an aqueous zinc ion battery, which comprises the following components in percentage by weight: 60%-90% of a conductive agent, 0.01%-1% of a dispersing agent, 9.99%-39% of a binder and 0.2%-1% of a water repellent agent. Compared with the prior art, the thickness of the prepared conductive protective coating is only 0.1-2 microns, on one hand, the coating has relatively high tensile strength and elastic modulus, the swelling behavior of the manganese dioxide positive plate can be relieved, and structural damage caused by separation of an active material from a current collector is prevented; impedance in the electrochemical reaction process can be reduced, deposition of manganese ions in the reaction process is facilitated, battery capacity fading is delayed, and the cycle life of the water-based zinc ion battery is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials, and particularly relates to a conductive protective coating for a manganese dioxide positive electrode of an aqueous zinc-ion battery and a preparation method thereof. Background Art

[0002] Aqueous zinc-ion secondary batteries (ZIBs) have received increasing attention in recent years due to their high safety, abundant and inexpensive resources, and environmental friendliness, and are considered to be one of the strong competitors for the next generation of new energy batteries.

[0003] Aqueous zinc-ion batteries usually use metallic zinc as the negative electrode and an aqueous solution containing Zn 2+ as the electrolyte. There are various positive electrode materials, such as manganese-based compounds, vanadium-based compounds, Prussian blue analogs, etc. Among them, manganese-based oxides have the advantages of rich resources, high working potential, and high theoretical capacity, and are one of the most promising positive electrode materials for aqueous zinc-ion batteries and are widely used in the positive electrode materials of zinc-ion batteries. However, during the charge and discharge process of the battery, the manganese-based positive electrode material is limited by manganese dissolution and crystal structure collapse caused by the Jahn-Teller effect, resulting in problems such as capacity decay. For example, during the battery cycle, due to the repeated deintercalation and intercalation of H + / Zn 2+ in the manganese-based compound, its structure changes, resulting in serious structural damage and large volume changes, leading to problems such as the dissolution of active Mn in the manganese dioxide positive electrode into the electrolyte and irreversible phase transformation; in addition, the characteristic of low conductivity of the manganese dioxide positive electrode as a semiconductor material also hinders the further development of the manganese dioxide positive electrode material in aqueous zinc-ion batteries.

[0004] In view of this, the present invention aims to provide a conductive protective coating for a manganese dioxide positive electrode of an aqueous zinc-ion battery and a preparation method thereof. Based on the research on the surface modification mechanism of the manganese dioxide positive electrode, an ultrathin conductive protective coating is constructed on the surface of the manganese dioxide positive electrode. This coating endows the manganese dioxide positive electrode with better conductive performance to a certain extent, can reduce the impedance during the reaction process, and enables Zn 2+ to deintercalate and intercalate faster in the manganese structure, indirectly improving the charge and discharge specific capacity of the battery. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, a conductive protective coating for a manganese dioxide positive electrode of an aqueous zinc-ion battery and a preparation method thereof are provided. Based on the research on the surface modification mechanism of the manganese dioxide positive electrode, an ultrathin conductive protective coating is constructed on the surface of the manganese dioxide positive electrode. This coating endows the manganese dioxide positive electrode with better conductive performance to a certain extent, can reduce the impedance during the reaction process, and enables Zn 2+It can be deintercalated and intercalated faster in the manganese structure, indirectly improving the charge-discharge specific capacity of the battery.

[0006] To solve the above problems, the technical solution of the present invention is as follows:

[0007] A conductive protective coating for a manganese dioxide positive electrode of an aqueous zinc-ion battery. By weight percentage, the protective coating includes 60% - 90% of a conductive agent, 0.01% - 1% of a dispersant, 9.99% - 39% of a binder, and 0.2% - 1% of a water repellent.

[0008] As an improvement to the conductive protective coating for the manganese dioxide positive electrode of the aqueous zinc-ion battery of the present invention, the binder is at least one of polyvinylidene fluoride, styrene-butadiene rubber, and polyacrylate;

[0009] The conductive agent is at least one of carbon nanotubes, carbon black, SuperP, acetylene black, graphene, and graphene oxide;

[0010] The dispersant is at least one of polyvinylpyrrolidone and polyacrylate;

[0011] The water repellent is at least one of silane coupling agent and silicone resin.

[0012] As an improvement to the conductive protective coating for the manganese dioxide positive electrode of the aqueous zinc-ion battery of the present invention, the thickness of the conductive protective coating is 0.1 - 2 μm.

[0013] The present invention also provides a preparation method for a conductive protective coating of a manganese dioxide positive electrode of an aqueous zinc-ion battery. The preparation method includes the following steps:

[0014] S1. Weigh the conductive agent, dispersant, binder, and water repellent according to the ratio;

[0015] S2. After mixing the weighed conductive agent, dispersant, and solvent evenly, add the binder and mix evenly, and then add the water repellent and mix evenly to obtain a protective coating slurry; wherein, the solvent is at least one of N-methylpyrrolidone, dimethylformamide, and deionized water;

[0016] S3. Build the protective coating slurry obtained in step S2 onto the surface of the manganese dioxide positive electrode sheet, dry it, and then cut it to obtain a manganese dioxide positive electrode with a conductive protective coating.

[0017] As an improvement to the preparation method for the conductive protective coating of the manganese dioxide positive electrode of the aqueous zinc-ion battery of the present invention, the addition amount of the solvent in step S2 accounts for 70% - 95% of the total mass of the materials.

[0018] As an improvement to the preparation method of the conductive protection coating for the manganese dioxide positive electrode of the aqueous zinc-ion battery of the present invention, the construction method in step S3 is spraying, brushing or roll coating.

[0019] As an improvement to the preparation method of the conductive protection coating for the manganese dioxide positive electrode of the aqueous zinc-ion battery of the present invention, when the construction method in step S3 is spraying, the spraying amount of the spray gun is 10-200 mL / min.

[0020] As an improvement to the preparation method of the conductive protection coating for the manganese dioxide positive electrode of the aqueous zinc-ion battery of the present invention, the drying method in step S3 is air drying or infrared drying, the drying temperature is 80-150 °C, the drying time is 0.1-10 min, and the thickness of the conductive protection coating is 0.1-2 μm.

[0021] The present invention also provides a manganese dioxide positive electrode for an aqueous zinc-ion battery, including a manganese dioxide positive electrode sheet and a conductive protection coating provided on the surface of the manganese dioxide positive electrode, and the conductive protection coating is the coating of the present invention.

[0022] The present invention improves the cycle stability of the manganese-based positive electrode by constructing an ultra-thin interfacial conductive protection coating on the surface of the manganese dioxide positive electrode, which can not only reduce the direct contact between the manganese dioxide positive electrode and the active water in the electrolyte, but also promote the zinc ion transport kinetics on the surface of the positive electrode. In addition, the coating can block the dissolved manganese dioxide and enable the dissolved manganese dioxide to redeposit between the positive electrode and the coating. The combination of the two can effectively solve the problems of poor conductivity, large volume change and high dissolution rate of the manganese dioxide positive electrode material in the aqueous zinc-ion battery.

[0023] By using the prepared manganese dioxide positive electrode, the rechargeable aqueous zinc-ion battery can be made into structures such as button type, column type, sheet type and soft package.

[0024] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are:

[0025] 1. Based on the research on the surface improvement mechanism of the manganese dioxide positive electrode, the present invention constructs an ultra-thin conductive protection coating on the surface of the manganese dioxide positive electrode. This coating endows the manganese dioxide positive electrode with better conductivity to a certain extent, can reduce the impedance during the reaction, and enables Zn 2+ to be deintercalated and intercalated faster in the manganese structure, indirectly improving the charge-discharge specific capacity of the battery.

[0026] 2. In the present invention, the ultra-thin conductive protective coating covering the surface of the manganese dioxide cathode of the aqueous zinc-ion battery has a high tensile strength and elastic modulus, enabling the manganese dioxide cathode material to effectively inhibit the structural damage of the manganese-based compound during charge and discharge, reducing the volume change of the cathode material. At the same time, the coating can block the dissolved manganese dioxide, allowing the dissolved manganese dioxide to redeposit between the cathode and the coating, thereby extending the cycle life of the battery. Meanwhile, the added hydrophobic agent component improves the hydrophobicity of manganese dioxide, reducing the contact between manganese dioxide and water and enhancing the stability of the manganese dioxide material.

[0027] 3. In the present invention, the preparation process of the conductive protective coating is simple, fast, environmentally friendly, and low-cost, facilitating the development of high-performance zinc-ion batteries.

[0028] 4. The thickness of the conductive protective coating prepared in the present invention is only 0.1 - 2 μm. On the one hand, this coating has a high tensile strength and elastic modulus, which can alleviate the swelling behavior of the manganese dioxide cathode sheet and prevent structural damage caused by the detachment of the active material from the current collector. On the other hand, this coating has conductive properties, which can reduce the impedance during the electrochemical reaction process, facilitate the deposition of manganese ions during the reaction process, delay the attenuation of battery capacity, and extend the cycle life of the aqueous zinc-ion battery. Description of the Drawings

[0029] Figure 1a It is a physical diagram of the manganese dioxide cathode prepared in Comparative Example 1 of the present invention.

[0030] Figure 1b It is a physical diagram of the trimmed manganese dioxide cathode prepared in Comparative Example 1 of the present invention.

[0031] Figure 1c It is a magnified physical diagram of the manganese dioxide cathode prepared in Comparative Example 1 of the present invention.

[0032] Figure 2a It is a physical diagram of the manganese dioxide cathode prepared in Example 1 of the present invention.

[0033] Figure 2b It is a physical diagram of the trimmed manganese dioxide cathode prepared in Example 1 of the present invention.

[0034] Figure 2c It is a magnified physical diagram of the manganese dioxide cathode prepared in Example 1 of the present invention.

[0035] Figure 3a It is a physical diagram of the manganese dioxide cathode prepared in Example 2 of the present invention.

[0036] Figure 3b It is a physical diagram of the trimmed manganese dioxide cathode prepared in Example 2 of the present invention.

[0037] Figure 3c This is a magnified physical image of the manganese dioxide positive electrode prepared in Example 2 of the present invention.

[0038] Figure 4 This is a comparison chart of the cycling performance of the full cells prepared in Examples 1-2 and Comparative Example 1 at a current density of 0.1 A·g-1.

[0039] Figure 5 This is a rate performance chart of the full cells prepared in Examples 1-2 and Comparative Example 1. Detailed implementation manners

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are some but not all of the embodiments of this application. Therefore, the detailed descriptions of the embodiments of the present invention provided in the drawings are not intended to limit the scope of the claimed invention, but merely represent selected embodiments of the present invention. Thus, all other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts fall within the scope of protection of this application.

[0041] Example 1

[0042] For the protective layer of the manganese dioxide positive electrode of the aqueous zinc ion battery provided in this embodiment, expressed in weight percentage, the component composition of the protective layer is 88.8% carbon nanotubes, 0.2% polyvinylpyrrolidone, 10% polyvinylidene fluoride, and 1% silane coupling agent.

[0043] The detailed steps of the preparation method of this embodiment are as follows:

[0044] a. Weigh carbon nanotubes, polyvinylpyrrolidone, polyvinylidene fluoride, silane coupling agent, and N-methylpyrrolidone accounting for 90% of the total material weight according to the component ratio of the protective layer;

[0045] b. After mixing the weighed carbon nanotubes and polyvinylpyrrolidone evenly, add two-thirds of the N-methylpyrrolidone, and stir evenly to obtain a dispersion;

[0046] c. Add the weighed polyvinylidene fluoride to the remaining one-third of the N-methylpyrrolidone, and mix evenly to obtain a mixed solution;

[0047] d. Slowly add the mixed solution in step c to the dispersion in step b and disperse evenly, then add the silane coupling agent, and stir evenly with ultrasonic assistance to obtain a protective coating slurry;

[0048] e. Spray the protective coating slurry obtained in step d onto the surface of the manganese dioxide positive electrode sheet at a rate of 50 ml / min using a spray gun, spray 3 times, and then dry it in a forced-air drying oven at 80 °C for 2 min. Cut it to obtain a manganese dioxide positive electrode with a conductive protective coating.

[0049] Using the prepared manganese dioxide positive electrode, negative electrode sheet, 2M ZnSO 4 The electrolyte and separator are assembled into a button-type full cell for charge-discharge testing. At a current density of 0.1 A·g, the discharge specific capacity can be maintained at 152.4 mAh·g after 100 cycles. -1 。

[0050] Example 2

[0051] For the protective layer of the manganese dioxide positive electrode of the aqueous zinc-ion battery provided in this example, expressed in weight percentage, the composition of the protective layer is 78.8% graphene oxide, 0.2% polyacrylate, 20% polyacrylate, and 1% silicone resin.

[0052] The detailed steps of the preparation method in this example are as follows:

[0053] a. Weigh graphene oxide, polyacrylate, polyacrylate, silicone resin, and deionized water accounting for 80% of the total material weight according to the composition ratio of the protective layer;

[0054] b. Mix the weighed graphene oxide and polyacrylate evenly, then add deionized water, stir evenly, and then ultrasonically disperse for 0.5 h to obtain a dispersion;

[0055] c. Add polyacrylate to the dispersion in step b, mix evenly, and then add silicone resin and mix evenly to obtain a protective coating slurry;

[0056] d. Spray the protective coating slurry obtained in step c onto the surface of the manganese dioxide positive electrode sheet at a rate of 50 ml / min using a spray gun, spray 3 times, and then dry it in a forced-air drying oven at 80 °C for 2 min. Cut it to obtain a manganese dioxide positive electrode with a conductive protective coating.

[0057] Using the prepared manganese dioxide positive electrode, negative electrode sheet, 2M ZnSO 4 The electrolyte and separator are assembled into a button-type full cell for charge-discharge testing. At a current density of 0.1 A·g, the discharge specific capacity can be maintained at 160.2 mAh·g after 100 cycles. -1 。

[0058] Comparative Example 1

[0059] The preparation method of this example includes the following steps:

[0060] 1) Cut the manganese dioxide positive electrode sheets prepared in the laboratory into positive electrode sheets for coin cells;

[0061] 2) Prepare 2M ZnSO 4 electrolyte;

[0062] 3) Assemble the positive electrode sheet, negative electrode sheet, ZnSO 4 electrolyte and separator into a coin-type full cell for charge and discharge tests.

[0063] Among them, the physical diagrams of the manganese dioxide positive electrodes prepared in Comparative Example 1 are as shown in Figure 1a , and its physical diagram after cutting is as shown in Figure 1b , and its physical diagram after optical magnification is as shown in Figure 1c . The physical diagrams of the manganese dioxide positive electrodes prepared in Example 1 are as shown in Figure 2a , and its physical diagram after cutting is as shown in Figure 2b , and its physical diagram after optical magnification is as shown in Figure 2c . The physical diagrams of the manganese dioxide positive electrodes prepared in Example 2 are as shown in Figure 3a , and its physical diagram after cutting is as shown in Figure 3b , and its physical diagram after optical magnification is as shown in Figure 3c .

[0064] As can be seen from Figures 1-3, the manganese dioxide positive electrodes of Example 1 and Example 2 with protective coatings are relatively similar to the manganese dioxide positive electrode of the comparative example without a protective coating in terms of macroscopic surface morphology, but it can be clearly seen that a protective coating has been formed on the microscopic surface morphology of Example 1 and Example 2.

[0065] Figure 4 Figure [X] is a comparison diagram of the cycling performance of the full cells prepared in Examples 1-2 and Comparative Example 1 at a current density of 0.1 A / g -1 . Figure 5 Figure [X] is the rate performance diagram of the full cells prepared in Examples 1-2 and Comparative Example 1. As can be seen from Figure 4 and Figure 5 , under the same conditions, after 200 cycles of the full cell of the comparative example, the discharge specific capacity curve drops rapidly, while the decline trends of the full cells of Example 1 and Example 2 with protective coatings are relatively stable, indicating that the protective coating can reduce the dissolution of the manganese dioxide positive electrode and improve the cycling stability of the battery; at the same time, at a rate from 0.1C to 2C, the reversible discharge capacities of the full cells of Example 1 and Example 2 with protective coatings are slightly better than those of the full cell of the comparative example without a protective coating.

[0066] Example 3

[0067] The protective layer of the manganese dioxide positive electrode of the aqueous zinc-ion battery provided in this embodiment, expressed in weight percentage, the composition of the protective layer is 79% carbon black, 0.5% polypropylene salt, 20% styrene-butadiene rubber, and 0.5% silicone resin.

[0068] The detailed steps of the preparation method of this embodiment are as follows:

[0069] a. Weigh carbon black, polypropylene salt, styrene-butadiene rubber, silicone resin, and 80% of the total material weight of dimethylformamide according to the composition ratio of the protective layer;

[0070] b. After mixing the weighed carbon black and polypropylene salt evenly, add two-thirds of the dimethylformamide, and stir evenly to obtain a dispersion;

[0071] c. Add the weighed styrene-butadiene rubber to the remaining one-third of the dimethylformamide, and mix evenly to obtain a mixed solution;

[0072] d. Slowly add the mixed solution in step c to the dispersion in step b and disperse evenly, then add silicone resin, and stir evenly with ultrasonic assistance to obtain a protective coating slurry;

[0073] e. Spray the protective coating slurry obtained in step d onto the surface of the manganese dioxide positive electrode sheet with a spray gun at 80 ml / min, spray 2 times, and then dry it in a forced-air drying oven at 100 °C for 2.5 min, and cut it to obtain a manganese dioxide positive electrode with a conductive protective coating.

[0074] Example 4

[0075] The protective layer of the manganese dioxide positive electrode of the aqueous zinc-ion battery provided in this embodiment, expressed in weight percentage, the composition of the protective layer is 84% SuperP, 0.4% polyvinylpyrrolidone, 15% polyacrylate, and 0.6% silane coupling agent.

[0076] The detailed steps of the preparation method of this embodiment are as follows:

[0077] a. Weigh SuperP, polyvinylpyrrolidone, polyacrylate, silane coupling agent, and 85% of the total material weight of N-methylpyrrolidone according to the composition ratio of the protective layer;

[0078] b. After mixing the weighed SuperP and polyvinylpyrrolidone evenly, add one-third of the N-methylpyrrolidone, and stir evenly to obtain a dispersion,

[0079] c. Add the weighed polyacrylate to the remaining two-thirds of the N-methylpyrrolidone, and mix evenly to obtain a mixed solution;

[0080] d. Slowly add the mixed solution in step c to the dispersion in step b and disperse evenly. Then add the silane coupling agent and stir evenly with ultrasonic assistance to obtain the protective coating slurry.

[0081] e. Brush the protective coating slurry obtained in step d onto the surface of the manganese dioxide positive electrode sheet, then dry it in a forced-air drying oven at 90 °C for 5 minutes, and cut it to obtain the manganese dioxide positive electrode with a conductive protective coating.

[0082] Example 5

[0083] For the protective layer of the manganese dioxide positive electrode of the aqueous zinc-ion battery provided in this example, expressed in weight percentage, the component composition of the protective layer is 86.8% acetylene black, 0.5% polyvinylpyrrolidone, 12% styrene-butadiene rubber, and 0.7% silicone resin.

[0084] The detailed steps of the preparation method of this example are as follows:

[0085] a. Weigh acetylene black, polyvinylpyrrolidone, styrene-butadiene rubber, silicone resin, and deionized water accounting for 75% of the total material weight according to the component ratio of the protective layer.

[0086] b. After mixing the weighed acetylene black and polyvinylpyrrolidone evenly, add two-thirds of the deionized water and stir evenly to obtain a dispersion.

[0087] c. Add the weighed styrene-butadiene rubber to the remaining one-third of the deionized water and mix evenly to obtain a mixed solution.

[0088] d. Slowly add the mixed solution in step c to the dispersion in step b and disperse evenly. Then add the silicone resin and stir evenly with ultrasonic assistance to obtain the protective coating slurry.

[0089] e. Roll-coat the protective coating slurry obtained in step d onto the surface of the manganese dioxide positive electrode sheet, then dry it in a forced-air drying oven at 85 °C for 6 minutes, and cut it to obtain the manganese dioxide positive electrode with a conductive protective coating.

[0090] Example 6

[0091] For the protective layer of the manganese dioxide positive electrode of the aqueous zinc-ion battery provided in this example, expressed in weight percentage, the component composition of the protective layer is 88.8% graphene, 0.2% polyvinylpyrrolidone, 10% polyvinylidene fluoride, and 1% silane coupling agent.

[0092] The detailed steps of the preparation method of this example are as follows:

[0093] a. Weigh graphene, polyvinylpyrrolidone, polyvinylidene fluoride, silane coupling agent and N-methylpyrrolidone accounting for 92% of the total material weight according to the component ratio of the protective layer;

[0094] b. After mixing the weighed graphene and polyvinylpyrrolidone evenly, add two-thirds of N-methylpyrrolidone, and stir evenly to obtain a dispersion;

[0095] c. Add the weighed polyvinylidene fluoride to the remaining one-third of N-methylpyrrolidone, and mix evenly to obtain a mixed solution;

[0096] d. Slowly add the mixed solution in step c to the dispersion in step b and disperse evenly, then add the silane coupling agent, and stir evenly with ultrasonic assistance to obtain a protective coating slurry;

[0097] e. Spray the protective coating slurry obtained in step d onto the surface of the manganese dioxide positive electrode sheet with a spray gun at 50 ml / min for 5 times, then dry it in a forced-air drying oven at 88 °C for 4 min, and cut it to obtain a manganese dioxide positive electrode with a conductive protective coating.

[0098] Based on the disclosure and teachings of the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A conductive protective coating for a manganese dioxide positive electrode of an aqueous zinc ion battery, characterized in that: Calculated by weight percentage, the protective coating includes 60% to 90% of a conductive agent, 0.01% to 1% of a dispersant, 9.99% to 39% of a binder and 0.2% to 1% of a hydrophobic agent.

2. The conductive protective coating for the manganese dioxide positive electrode of an aqueous zinc ion battery according to claim 1, characterized in that: The binder is at least one of polyvinylidene fluoride, styrene-butadiene rubber and polyacrylate; The conductive agent is at least one of carbon nanotubes, carbon black, SuperP, acetylene black, graphene and graphene oxide; The dispersant is at least one of polyvinyl pyrrolidone and polyacrylate; The hydrophobic agent is at least one of a silane coupling agent and an organic silicone resin.

3. The conductive protective coating for the manganese dioxide positive electrode of an aqueous zinc ion battery according to claim 1, characterized in that: The thickness of the conductive protective coating is 0.1 to 2 μm.

4. A method for preparing a conductive protective coating for an aqueous zinc ion battery manganese dioxide positive electrode according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: S1. Weigh the conductive agent, dispersant, binder and hydrophobic agent in proportion; S2. After the weighed conductive agent, dispersant and solvent are mixed evenly, a binder is added and mixed evenly, and then a hydrophobic agent is added and mixed evenly to obtain a protective coating slurry; wherein the solvent is at least one of N-methylpyrrolidone, dimethylformamide and deionized water; S3, constructing the protective coating slurry obtained in step S2 onto the surface of the manganese dioxide positive electrode sheet, and cutting it after drying to obtain a manganese dioxide positive electrode with a conductive protective coating.

5. The method for preparing the conductive protective coating of manganese dioxide positive electrode of aqueous zinc ion battery according to claim 4, characterized in that: The amount of the solvent added in step S2 accounts for 70% to 95% of the total mass of the material.

6. The method for preparing the conductive protective coating for manganese dioxide positive electrode of aqueous zinc ion battery according to claim 4, characterized in that: The construction method in step S3 is spraying, brushing or roller coating.

7. The method for preparing the conductive protective coating for the manganese dioxide positive electrode of an aqueous zinc ion battery according to claim 6, characterized in that: When the construction method in step S3 is spraying, the spraying amount of the spray gun is 10 to 200 mL / min.

8. The method for preparing the conductive protective coating for the manganese dioxide positive electrode of an aqueous zinc ion battery according to claim 4, characterized in that: In step S3, the drying method is air drying or infrared drying, the drying temperature is 80-150° C., the drying time is 0.1-10 min, and the thickness of the conductive protective coating is 0.1-2 μm.

9. A manganese dioxide positive electrode for an aqueous zinc ion battery, characterized in that: It comprises a manganese dioxide positive electrode sheet and a conductive protective coating arranged on the surface of the manganese dioxide positive electrode, wherein the conductive protective coating is the coating according to any one of claims 1 to 3.

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