Alginate-polyacrylamide gel-coated modified manganese-based positive electrode and its preparation method and application

Abstract

The present invention discloses an alginate-polyacrylamide gel-coated modified manganese-based positive electrode and its preparation and application. The present invention uses acrylamide, ammonium persulfate, N,N'-methylenebisacrylamide and sodium alginate to prepare a gel solution, and coats it on the surface of a layered manganese dioxide positive electrode plate to improve the cycle stability and other electrochemical properties of the positive electrode material. The positive electrode material substrate is a layered manganese dioxide positive electrode material prepared by a liquid phase alkaline etching method. The gel film is coated on the surface of the positive electrode material by coating and drying, and suppresses the dissolution of manganese and the occurrence of other side reactions without basically affecting the transfer of zinc ions during the charge and discharge process. The electrochemical test results show that the coating of the gel film improves the cycle performance and rate performance of the positive electrode plate. At a current density of 1A / g, a high specific capacity of 182.4mAh / g can be achieved after 500 cycles.

Description

Technical Field

[0001] The present invention relates to an alginate-polyacrylamide gel-coated manganese-based positive electrode and a preparation method thereof, as well as application of the alginate-polyacrylamide gel-coated manganese-based positive electrode as a positive electrode material for a zinc ion battery, belonging to the technical field of battery positive electrode materials and their preparation. Background Art

[0002] In recent years, with the continuous deepening of energy use, energy storage technology has played a vital role in energy storage and rational energy utilization. With the development of new energy technologies, ion batteries have been widely studied as excellent energy storage devices.

[0003] Among various ion battery energy storage devices, aqueous zinc-ion batteries are considered to be one of the new technologies most likely to replace lithium-ion batteries due to their advantages such as high operating voltage, high energy density, excellent rate performance, low pollution and high safety.

[0004] Layered manganese dioxide (δ-MnO2) is a promising cathode material for aqueous zinc-ion batteries. Its layered structure can effectively store charged particles. However, the manganese dissolution of manganese-based cathode materials during the charge and discharge process limits their further development. In the modification of zinc-ion battery systems, special gels as electrolytes or negative electrode coatings can effectively reduce the formation of zinc dendrites, but they have not been applied to positive electrode modification. Organic gel coatings can inhibit manganese dissolution and thus improve the electrochemical performance of the material. At the same time, the gel film provides a buffer area at the positive electrode electrolyte contact interface, ensuring the cyclic stability of the material. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the primary purpose of the present invention is to provide an alginate-polyacrylamide gel-coated modified manganese-based positive electrode, which has significantly improved cycle performance and rate performance.

[0006] The alginate-polyacrylamide gel-coated modified manganese-based positive electrode is a positive electrode sheet prepared from layered manganese dioxide nanomaterials and has an alginate-polyacrylamide gel coating layer on its surface.

[0007] The coating thickness of the gel coating layer is 0.1 to 1.0 mm, preferably 0.2 to 0.4 mm.

[0008] The second object of the present invention is to provide a method for preparing the alginate-polyacrylamide gel-coated modified manganese-based positive electrode, which has simple process, low cost, and potential for industrial production. The coating of the gel film can effectively improve the cycle performance of the positive electrode material.

[0009] Specifically, a certain proportion of acrylamide, ammonium persulfate and N,N'-methylenebisacrylamide are dissolved in deionized water, and then alginate is added and stirred until the solution becomes a gel. The solution is then coated on a dried layered manganese dioxide positive electrode sheet and in-situ polymerization is performed again at a certain temperature to obtain the product.

[0010] Further,

[0011] The concentration of acrylamide in the solution is 200-400 g / L, preferably 250-350 g / L, and the concentration of ammonium persulfate is 0.5-1.5 g / L, preferably 0.7-1.3 g / L;

[0012] The concentration of N,N'-methylenebisacrylamide is 0.05-0.3 g / L, preferably 0.1-0.2 g / L; the concentration of sodium alginate is 1-3 g / 100 mL, preferably 1.5-2 g / 100 mL.

[0013] Furthermore, the alginate includes sodium alginate or potassium alginate. After the alginate is added, the mixture is stirred vigorously until the viscosity of the solution increases and becomes a gel without significant change. The stirring time is preferably 10 to 15 minutes.

[0014] The preparation method of the layered manganese dioxide material is a liquid phase alkaline etching method. First, a manganese salt solution and a silicate solution are mixed and stirred to obtain a manganese silicate precipitate. Then, the manganese silicate is etched with a sodium hydroxide solution to obtain a layered manganese dioxide nanomaterial.

[0015] The layered manganese dioxide positive electrode sheet is prepared by uniformly mixing layered manganese dioxide nanomaterials, acetylene black and polyvinylidene fluoride in proportion, preparing a paste with N-methylpyrrolidone, and then uniformly coating the paste on a titanium foil; and drying the mixture in a vacuum oven.

[0016] Furthermore, the concentration of the silicate is 70 mmoL / L. The concentration of the manganese salt is 70 mmoL / L. The concentration of sodium hydroxide in the alkaline etching solution is 2 mol / L. The volume ratio range of the silicate:manganese salt solution is: 1:1. The liquid-to-solid ratio of the alkaline etching solution to the manganese silicate precursor is: 100 mL / 0.2 g. The mixing temperature during the preparation of the precursor is 20°C and the mixing time is 1.5 hours. The temperature of the alkaline etching treatment is 90°C and the time is 12 hours.

[0017] Further,

[0018] After the precursor is treated by alkali etching, the product is obtained by washing, filtering and drying.

[0019] The drying is vacuum drying, the drying temperature is 60-100° C., and the drying time is 12-24 hours.

[0020] Furthermore, the layered manganese dioxide nanomaterial, acetylene black and polyvinylidene fluoride were evenly mixed in a ratio of 7:2:1, prepared into a paste with N-methylpyrrolidone and evenly coated on the titanium foil; and dried in a vacuum oven at 100°C for 12 hours.

[0021] After the gel is coated, the in-situ polymerization temperature is 50-70° C. and the time is 7-9 hours.

[0022] The present invention also provides the use of a modified manganese-based cathode coated with an alginate-polyacrylamide gel as a cathode material for zinc-ion batteries. This material exhibits excellent reversible specific capacity, reaching a high specific capacity of 182.4 mAh / g after 500 cycles at a current density of 1.0 A / g.

[0023] The present invention also provides a zinc ion battery, which uses the alginate-polyacrylamide gel to coat a modified manganese-based positive electrode. The electrochemical performance of the electrode material is tested as follows:

[0024] 1) The simulated battery used a CR2025 button cell system, the electrolyte was a mixed aqueous solution of 1M zinc sulfate and 0.2M manganese sulfate, the negative electrode was a round zinc sheet, and the battery separator was glass fiber;

[0025] 2) The reversible capacity and cycle performance of the electrode material are tested and analyzed using a constant current charge-discharge test method. The charge-discharge regime is: voltage range: 0.8-1.8V; the number of cycles is generally 1-500 times.

[0026] Compared with the existing technology, the technical solution of the present invention brings the following beneficial technical effects:

[0027] 1) The alginate-polyacrylamide gel-coated modified manganese-based positive electrode provided by the present invention is formed by coating a gel layer on the surface of the positive electrode sheet prepared from manganese dioxide nanomaterials. While ensuring the normal transfer of zinc ions and hydrogen ions, it reduces the problem of reversible capacity reduction caused by manganese dissolution, thereby improving the electrochemical performance of the material.

[0028] 2) Due to the presence of the coating film, the original growth sites of the by-product basic zinc sulfate in the cycle are greatly reduced, which alleviates the situation where basic zinc sulfate covers the positive electrode surface, thereby improving the electrochemical performance of the material.

[0029] 3) When the alginate-polyacrylamide gel-coated modified manganese-based positive electrode provided by the present invention is used in zinc-ion batteries, severe manganese dissolution is suppressed. Electrochemical test results also show that the coated material has good reversible specific capacity. At a current density of 1 A / g, the specific capacity can reach up to 182.4 mAh / g after 500 cycles. It is at the leading level among the currently reported manganese-based positive electrode materials for aqueous zinc-ion batteries.

[0030] 4) The preparation method of the present invention is highly operable, low-cost, and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the electrochemical performance diagram of the alginate-polyacrylamide gel-coated modified manganese-based positive electrode prepared in Example 1.

[0032] Figure 2 This is the XRD pattern of the alginate-polyacrylamide gel-coated modified manganese-based positive electrode prepared in Example 1.

[0033] Figure 3 This is the SEM image of the alginate-polyacrylamide gel-coated modified manganese-based positive electrode prepared in Example 1. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and specific examples, but the examples do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0035] Unless otherwise specified, the reagents and materials used in the following examples were commercially available.

[0036] Example 1

[0037] A method for preparing an alginate-polyacrylamide gel-coated modified manganese-based positive electrode comprises the following steps:

[0038] 1) Dissolve 3 mmol of sodium silicate and manganese chloride in 100 mL of deionized water, stir for 1.5 h to obtain a brown-yellow solution, centrifuge, wash with water, and dry at 60° C. for 24 h to obtain a manganese silicate precursor;

[0039] 2) 0.2 g of the precursor was added to 100 mL of 2 mol / L alkaline sodium hydroxide and etched at 90° C. for 12 h, followed by washing and drying to obtain a layered manganese dioxide nanomaterial.

[0040] 3) The prepared layered manganese dioxide nanomaterial, binder polyvinylidene fluoride, and conductive agent acetylene black were dissolved in N-methylpyrrolidone at a ratio of 7:2:1 to prepare a slurry, which was coated on a titanium foil and dried under vacuum at 100°C for 12 hours to obtain a positive electrode sheet to be gel-coated.

[0041] 4) Dissolve 3 g acrylamide, 10 mg ammonium persulfate, and 1.5 mg N,N'-methylenebisacrylamide in 10 mL deionized water, then add 0.18 g sodium alginate and stir vigorously for 10 minutes until the gel solution becomes transparent.

[0042] 5) The gel was coated on the dried positive electrode sheet with a coating thickness of 0.5 mm. After coating, the electrode sheet was subjected to in-situ polymerization at 60° C. for 8 h to obtain an alginate-polyacrylamide gel coating layer modified layered manganese dioxide positive electrode sheet.

[0043] In order to verify the electrochemical performance of the layered manganese dioxide cathode modified with alginate-polyacrylamide gel coating layer, and further apply it as the cathode material of zinc ion batteries:

[0044] The electrolyte is a mixed aqueous solution of 1M zinc sulfate and 0.2M manganese sulfate, the negative electrode is a circular zinc sheet, and the battery separator is glass fiber; the electrochemical performance is analyzed by constant current charge and discharge test, with a voltage range of 0.8 to 1.8V. The results of the electrochemical performance test are shown in the figure. Figure 1 It can be observed that at a current density of 1A / g, it can reach a high specific capacity of 182.4mAh / g after 500 cycles, with a capacity retention rate of 88.2%, which is at the leading level among zinc-ion battery positive electrode materials.

[0045] Figure 2 It can be observed that the structure of the manganese dioxide nanomaterial prepared in this example is δ-MnO2. The layered structure enables zinc ions to be more efficiently inserted and removed, and the structure of the manganese dioxide is not damaged by the coating layer.

[0046] Figure 3 The surface morphology of the solidified gel of the alginate-polyacrylamide gel coating layer prepared in this example is clearly shown.

[0047] Example 2

[0048] A method for preparing an alginate-polyacrylamide gel-coated modified manganese-based positive electrode comprises the following steps:

[0049] 1) Dissolve 3 mmol of sodium silicate and manganese chloride in 100 mL of deionized water, stir for 1.5 h to obtain a brown-yellow solution, centrifuge, wash with water, and dry at 60° C. for 24 h to obtain a manganese silicate precursor;

[0050] 2) 0.2 g of the precursor was added to 100 mL of 2 mol / L alkaline sodium hydroxide and etched at 90° C. for 12 h, followed by washing and drying to obtain a layered manganese dioxide nanomaterial.

[0051] 3) The prepared layered manganese dioxide nanomaterial, binder polyvinylidene fluoride, and conductive agent acetylene black were dissolved in N-methylpyrrolidone at a ratio of 7:2:1 to prepare a slurry, which was coated on a titanium foil and dried under vacuum at 100°C for 12 hours to obtain a positive electrode sheet to be gel-coated.

[0052] 4) Dissolve 3.2 g acrylamide, 11 mg ammonium persulfate, and 1.6 mg N,N'-methylenebisacrylamide in 10 mL deionized water, then add 0.20 g sodium alginate and stir vigorously for 10 minutes until the gel solution becomes transparent.

[0053] 5) The gel was coated on the dried positive electrode sheet with a coating thickness of 0.5 mm. After coating, the electrode sheet was subjected to in-situ polymerization at 60° C. for 8 h to obtain an alginate-polyacrylamide gel coating layer modified layered manganese dioxide positive electrode sheet.

[0054] In order to verify the electrochemical performance of the layered manganese dioxide cathode modified with alginate-polyacrylamide gel coating layer, and further apply it as the cathode material of zinc ion batteries:

[0055] The electrolyte used was a mixed aqueous solution of 1M zinc sulfate and 0.2M manganese sulfate. The negative electrode was a circular zinc sheet, and the battery separator was a glass fiber. Constant current charge-discharge tests were used to analyze its electrochemical performance over a voltage range of 0.8 to 1.8 V. Testing of its electrochemical performance revealed a high specific capacity of 181.2 mAh / g after 500 cycles at a current density of 1 A / g, with a capacity retention rate of 82.5%.

[0056] Example 3

[0057] A method for preparing an alginate-polyacrylamide gel-coated modified manganese-based positive electrode comprises the following steps:

[0058] 1) Dissolve 3 mmol of sodium silicate and manganese chloride in 100 mL of deionized water, stir for 1.5 h to obtain a brown-yellow solution, centrifuge, wash with water, and dry at 60° C. for 24 h to obtain a manganese silicate precursor;

[0059] 2) 0.2 g of the precursor was added to 100 mL of 2 mol / L alkaline sodium hydroxide and etched at 90° C. for 12 h, followed by washing and drying to obtain a layered manganese dioxide nanomaterial.

[0060] 3) The prepared layered manganese dioxide nanomaterial, binder polyvinylidene fluoride, and conductive agent acetylene black were dissolved in N-methylpyrrolidone at a ratio of 7:2:1 to prepare a slurry, which was coated on a titanium foil and dried under vacuum at 100°C for 12 hours to obtain a positive electrode sheet to be gel-coated.

[0061] 4) Dissolve 3 g acrylamide, 10 mg ammonium persulfate, and 1.5 mg N,N'-methylenebisacrylamide in 10 mL deionized water, then add 0.18 g sodium alginate and stir vigorously for 10 minutes until the gel solution becomes transparent.

[0062] 5) The gel was coated on the dried positive electrode sheet with a coating thickness of 0.6 mm. After coating, the electrode sheet was subjected to in-situ polymerization at 65° C. for 9 h to obtain an alginate-polyacrylamide gel coating layer modified layered manganese dioxide positive electrode sheet.

[0063] In order to verify the electrochemical performance of the layered manganese dioxide cathode modified with alginate-polyacrylamide gel coating layer, and further apply it as the cathode material of zinc ion batteries:

[0064] The electrolyte used was a mixed aqueous solution of 1M zinc sulfate and 0.2M manganese sulfate. The negative electrode was a circular zinc sheet, and the battery separator was a glass fiber. Constant current charge-discharge tests were used to analyze its electrochemical performance over a voltage range of 0.8 to 1.8 V. Testing of its electrochemical performance revealed a high specific capacity of 178.4 mAh / g after 500 cycles at a current density of 1 A / g, with a capacity retention rate of 73.3%.

[0065] Comparative Example 1

[0066] A method for preparing an uncoated layered manganese dioxide positive electrode sheet comprises the following steps:

[0067] 1) Dissolve 3 mmol of sodium silicate and manganese chloride in 100 mL of deionized water, stir for 1.5 h to obtain a brown-yellow solution, centrifuge, wash with water, and dry at 60° C. for 24 h to obtain a manganese silicate precursor;

[0068] 2) 0.2 g of the precursor was added to 100 mL of 2 mol / L alkaline sodium hydroxide and etched at 90° C. for 12 h, followed by washing and drying to obtain a layered manganese dioxide nanomaterial.

[0069] 3) The prepared layered manganese dioxide nanomaterial, binder polyvinylidene fluoride, and conductive agent acetylene black were dissolved in N-methylpyrrolidone at a ratio of 7:2:1 to prepare a slurry, which was coated on a titanium foil and dried under vacuum at 100°C for 12 hours to obtain an unmodified layered manganese dioxide positive electrode sheet.

[0070] In order to verify the electrochemical performance of the unmodified layered manganese dioxide cathode material and further apply it as a cathode material for zinc ion batteries:

[0071] The electrolyte used was a mixed aqueous solution of 1M zinc sulfate and 0.2M manganese sulfate. The negative electrode was a circular zinc sheet, and the battery separator was a glass fiber. Constant current charge-discharge tests were used to analyze its electrochemical performance over a voltage range of 0.8 to 1.8 V. Testing revealed that at a current density of 1 A / g, it achieved a maximum specific capacity of 153.1 mAh / g after 500 cycles, with a capacity retention rate of 68.9%.

[0072] Comparative Example 2

[0073] A method for preparing a layered manganese dioxide positive electrode sheet modified with an alginate-polyacrylamide gel coating layer comprises the following steps:

[0074] 1) Dissolve 3 mmol of sodium silicate and manganese chloride in 100 mL of deionized water, stir for 1.5 h to obtain a brown-yellow solution, centrifuge, wash with water, and dry at 60° C. for 24 h to obtain a manganese silicate precursor;

[0075] 2) 0.2 g of the precursor was added to 100 mL of 2 mol / L alkaline sodium hydroxide and etched at 90° C. for 12 h, followed by washing and drying to obtain a layered manganese dioxide nanomaterial.

[0076] 3) The prepared layered manganese dioxide nanomaterial, binder polyvinylidene fluoride, and conductive agent acetylene black were dissolved in N-methylpyrrolidone at a ratio of 7:2:1 to prepare a slurry, which was coated on a titanium foil and dried under vacuum at 100°C for 12 hours to obtain a positive electrode sheet to be gel-coated.

[0077] 4) Dissolve 3 g acrylamide, 10 mg ammonium persulfate, and 1.5 mg N,N'-methylenebisacrylamide in 10 mL deionized water, then add 0.18 g sodium alginate and stir vigorously for 10 minutes until the gel solution becomes transparent.

[0078] 5) The gel was coated on the dried positive electrode sheet with a coating thickness of 2.0 mm. After coating, the electrode sheet was subjected to in-situ polymerization at 80° C. for 15 h to obtain an alginate-polyacrylamide gel coating layer modified layered manganese dioxide positive electrode sheet.

[0079] In order to verify the electrochemical performance of the layered manganese dioxide cathode modified with alginate-polyacrylamide gel coating layer, and further apply it as the cathode material of zinc ion batteries:

[0080] The electrolyte used was a mixed aqueous solution of 1M zinc sulfate and 0.2M manganese sulfate, the negative electrode was a circular zinc sheet, and the battery separator was a glass fiber. Constant current charge-discharge tests were used to analyze the electrochemical performance over a voltage range of 0.8 to 1.8V. Testing of the electrochemical performance revealed that at a current density of 1A / g, the device achieved a maximum specific capacity of 94.1mAh / g after 500 cycles, with a capacity retention rate of 60.1%. The low capacity may be due to the high polymerization temperature and prolonged curing time, which denatured the organogel membrane and reduced the material's ion permeability.

[0081] Comparative Example 3

[0082] A method for preparing a layered manganese dioxide positive electrode sheet modified with a phenylboronic acid grafted conductive organic gel coating layer comprises the following steps:

[0083] 1) Dissolve 3 mmol of sodium silicate and manganese chloride in 100 mL of deionized water, stir for 1.5 h to obtain a brown-yellow solution, centrifuge, wash with water, and dry at 60° C. for 24 h to obtain a manganese silicate precursor;

[0084] 2) 0.2 g of the precursor was added to 100 mL of 2 mol / L alkaline sodium hydroxide and etched at 90° C. for 12 h, followed by washing and drying to obtain a layered manganese dioxide nanomaterial.

[0085] 3) The prepared layered manganese dioxide nanomaterial, binder polyvinylidene fluoride, and conductive agent acetylene black were dissolved in N-methylpyrrolidone at a ratio of 7:2:1 to prepare a slurry, which was coated on a titanium foil and dried under vacuum at 100°C for 12 hours to obtain a positive electrode sheet to be gel-coated.

[0086] 4) 5 mg of reduced graphene oxide powder was evenly dispersed in a mixed solution of 1.8 g of water and 1.8 g of ethanol, and then 0.8 g of acrylamide, 8.1 mg of ammonium persulfate, and 2.5 mg of N,N'-methylenebisacrylamide were added and stirred until completely dissolved. Then, 0.12 g of phenylboronic acid-grafted sodium alginate powder was added and stirred thoroughly to obtain a pregel.

[0087] 5) The gel was coated on the dried positive electrode sheet with a coating thickness of 0.5 mm. After coating, the electrode sheet was subjected to in-situ polymerization at 60° C. for 8 h in a vacuum to obtain a phenylboronic acid grafted conductive organic gel coating layer modified layered manganese dioxide positive electrode sheet.

[0088] In order to verify the electrochemical performance of the layered manganese dioxide cathode modified with phenylboronic acid grafted conductive organic gel coating layer, and further apply it as the cathode material of zinc ion battery:

[0089] The electrolyte used was a mixed aqueous solution of 1M zinc sulfate and 0.2M manganese sulfate. The negative electrode was a circular zinc sheet, and the battery separator was a glass fiber. Constant current charge-discharge tests were used to analyze its electrochemical performance over a voltage range of 0.8 to 1.8 V. Testing of its electrochemical performance revealed that at a current density of 1 A / g, it achieved a maximum specific capacity of 74.4 mAh / g after 500 cycles, with a capacity retention rate of 47.2%.

Claims

1. Alginate-polyacrylamide gel-coated modified manganese-based positive electrode, characterized by: The surface of the positive electrode sheet prepared from layered manganese dioxide nanomaterials is coated with an alginate-polyacrylamide gel.

2. The alginate-polyacrylamide gel-coated modified manganese-based positive electrode according to claim 1, characterized in that: Coating thickness 0.1~1.0mm.

3. The alginate-polyacrylamide gel-coated modified manganese-based positive electrode according to claim 2, characterized in that: Coating thickness 0.2~0.4mm.

4. The method for preparing the alginate-polyacrylamide gel-coated modified manganese-based positive electrode according to claim 1, 2 or 3, characterized in that: A certain proportion of acrylamide, ammonium persulfate and N,N'-methylenebisacrylamide are dissolved in deionized water, and then alginate is added and stirred until the solution becomes a gel. The solution is then coated on a dried layered manganese dioxide positive electrode sheet and in-situ polymerization is performed again at a certain temperature to obtain the obtained product.

5. The preparation method according to claim 4, characterized in that The concentration of acrylamide in the solution is 200-400 g / L, and the concentration of ammonium persulfate is 0.5-1.5 g / L; The concentration of N,N'-methylenebisacrylamide is 0.05~0.3g / L, and the concentration of sodium alginate is 1~3g / 100mL.

6. The preparation method according to claim 5, characterized in that The concentration of acrylamide in the solution is 250-350 g / L, and the concentration of ammonium persulfate is 0.7-1.3 g / L; The concentration of N,N'-methylenebisacrylamide is 0.1~0.2g / L; the concentration of sodium alginate is 1.5~2 g / 100mL.

7. The preparation method according to claim 4, characterized in that The alginate includes sodium alginate or potassium alginate. After adding the alginate, stir vigorously until the viscosity of the solution increases and becomes a gel and then there is no obvious change.

8. The preparation method according to claim 4, characterized in that: The preparation method of the layered manganese dioxide material is a liquid phase alkaline etching method. First, a manganese salt solution and a silicate solution are mixed and stirred to obtain a manganese silicate precipitate. Then, the manganese silicate is etched with a sodium hydroxide solution to obtain a layered manganese dioxide nanomaterial. The layered manganese dioxide positive electrode sheet is prepared by uniformly mixing layered manganese dioxide nanomaterials, acetylene black and polyvinylidene fluoride in proportion, preparing a paste with N-methylpyrrolidone, and then uniformly coating the paste on a titanium foil; and drying the mixture in a vacuum oven.

9. The preparation method according to claim 4, characterized in that: After coating, the in-situ polymerization temperature is 30~90℃ and the time is 5~12h.

10. The preparation method according to claim 9, characterized in that: After coating, the in-situ polymerization temperature is 50~70℃ and the time is 7~9h.

11. The use of the alginate-polyacrylamide gel coating modified manganese-based positive electrode according to claim 1, 2 or 3, characterized in that: Used as positive electrode material in zinc-ion batteries.

12. A zinc ion battery, characterized in that: The alginate-polyacrylamide gel according to any one of claims 1 to 3 is used to coat the modified manganese-based positive electrode.

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