High-capacity stable manganese-iodine composite material, preparation method and application thereof, preparation method of positive electrode material, positive electrode plate and zinc ion battery

Abstract

The invention relates to the technical field of electrochemical energy storage, and particularly provides a high-capacity stable manganese-iodine composite material, a preparation method and application thereof, a preparation method of a positive electrode material, a positive plate and a zinc ion battery. The manganese-iodine composite material comprises manganese oxide, iodide and a conductive agent. In order to solve the problem of low intrinsic conductivity of manganese oxide, iodide with high conductivity is introduced, so that the electron conduction capability of the composite material is remarkably improved. The iodide constructs a three-dimensional permeable electron transport network through a rapid oxidation-reduction reaction, so that the electronic conductivity of the composite material is greatly improved. An accurately matched redox potential synergistic system is formed between the iodide and the manganese oxide, a potential relay type synergistic reaction mechanism can be realized by the iodide and the manganese oxide due to an almost overlapped electrochemical window, and the reaction activation energy barrier and the reaction kinetics of Mn < 4 + > / Mn < 3 + > can be effectively reduced. The characteristics jointly construct a high-performance and high-stability aqueous zinc-manganese battery system.

Description

Technical Field

[0001] The present application relates to the field of electrochemical energy storage technology, and in particular to a manganese-iodine composite material, a preparation method and use thereof, a preparation method of a positive electrode material, a positive electrode sheet, and a zinc ion battery. Background Art

[0002] Aqueous zinc-ion batteries have become a popular candidate for the next generation of energy storage technology due to their significant advantages such as high safety, low cost and environmental friendliness. However, traditional manganese dioxide (MnO2) cathode materials face many challenges in practical applications: their poor intrinsic conductivity, severe capacity decay caused by manganese dissolution during charge and discharge, and the generation of irreversible products (such as ZnMn2O4) by side reactions, which greatly limit their performance and commercial application prospects. Although manganese dioxide cathodes have a high theoretical capacity (based on the two-electron transfer reaction Mn 4+ / Mn 3+ , the theoretical capacity can reach 308mAh g -1 ) and suitable operating voltage, but their inherent defects, such as Jahn-Teller distortion, low conductivity, and slow ion diffusion kinetics, result in their actual capacity being far lower than the theoretical value, and their cycling stability and rate performance are poor.

[0003] In order to solve these problems, researchers began to explore improving the performance of manganese dioxide by introducing highly conductive materials. Iodide has shown great potential in the field of energy storage due to its excellent conductivity, chemical stability and ability to regulate ion transport pathways. Iodide can not only significantly improve the electronic conduction rate of manganese dioxide, but the introduction of iodide can also optimize the ion transport pathway in the electrolyte and promote the reversible insertion / extraction of ions, thereby effectively inhibiting the occurrence of side reactions. Although the synergistic mechanism of iodide and manganese dioxide has not yet been fully revealed, preliminary studies have shown that the addition of iodide can significantly improve the specific capacity, cycle stability and rate performance of the positive electrode material, providing new ideas for the development of high-performance aqueous zinc-ion batteries.

[0004] In order to solve the above problems, this application is proposed. Summary of the Invention

[0005] The present application provides a high-capacity and stable manganese-iodine composite material and its preparation method, a positive electrode sheet and a zinc ion battery, so as to improve the specific capacity and cycle stability of the manganese dioxide positive electrode of the aqueous zinc ion battery.

[0006] In a first aspect, the present application provides a manganese-iodine composite material, which comprises: iodide, a conductive agent, and manganese oxide.

[0007] Preferably, the mass ratio of the iodide to the manganese oxide is (0.2-0.5):1.

[0008] The manganese oxide is one or more of manganese dioxide, dimanganese trioxide or trimanganese tetraoxide.

[0009] Preferably, the manganese dioxide is tunnel-type α-manganese dioxide.

[0010] A second aspect of the present application provides a method for preparing a manganese-iodine composite material, the method comprising the following steps:

[0011] Place the predetermined ratio of iodide and conductive agent in a mortar and grind thoroughly until a fine powder is formed. Add an appropriate amount of solvent to the powder and stir to form a uniformly dispersed solution. Transfer the mixed solution to a sealed reactor, heat it to 120°C in an oven, and react for 2 hours.

[0012] After the reaction is completed, the reactor is cooled naturally to room temperature, and a predetermined amount of manganese oxide is added to the solution in the reactor, and the mixture is stirred and mixed thoroughly.

[0013] The resulting mixed slurry is centrifuged to collect a solid product. The solid product is repeatedly washed with deionized water (3-5 times) to remove impurities. The washed solid product is freeze-dried to obtain the highly conductive manganese-iodine composite material.

[0014] Preferably, the mass ratio of the iodide to the manganese oxide is (0.1-0.5):1.

[0015] The mass ratio of the conductive agent to the iodide is (0.1-2.0):2.

[0016] Preferably, the solvent is selected from: one or more of deionized water, acetonitrile, and ethanol.

[0017] Preferably, the stirring time is 2 to 12 hours.

[0018] The third aspect of the present application provides the use of the manganese-iodine composite material described in the first aspect as a positive electrode material for zinc ion batteries.

[0019] The fourth aspect of the present application provides a method for preparing a positive electrode material, which comprises the following steps: adding a solvent to the manganese-iodine composite material of the first aspect: a conductive agent: a binder in a mass ratio of (7-8): (2-1): 1, grinding and mixing, coating or rolling it onto a current collector, and drying to obtain a positive electrode material.

[0020] Preferably, the conductive agent includes one or more of graphene, acetylene black, activated carbon, carbon nanotubes, and YP-80F.

[0021] Preferably, the solvent is water, ethanol, or N-methylpyrrolidone.

[0022] Preferably, the loading amount of the manganese-iodine composite material on the current collector is 1.0 to 30.0 mg cm -2 .

[0023] Preferably, the current collector is selected from: carbon cloth, titanium foil or stainless steel mesh.

[0024] The drying condition was 60° C. for 12 hours.

[0025] Preferably, the binder is selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and carboxymethyl cellulose (CMC).

[0026] The finally obtained positive electrode material of the present application contains the manganese-iodine composite material of the first aspect.

[0027] In a fifth aspect, the present application provides a positive electrode sheet, comprising: a positive electrode material layer; the positive electrode material layer comprises the manganese-iodine composite material described in any one of the first aspects or the positive electrode material prepared by the preparation method described in any one of claims 5 to 9.

[0028] A sixth aspect of the present application provides a zinc ion battery, which includes the positive electrode sheet described in the fifth aspect.

[0029] Preferably, the electrolyte of the battery comprises manganese sulfate and zinc sulfate.

[0030] Preferably, the molar concentration of manganese sulfate is 0.05 to 0.6 M, and the molar concentration of zinc sulfate is 0.05 to 3 M. The negative electrode of the battery is a metal zinc foil. The thickness of the metal zinc foil is 30 to 100 microns, and the battery is sealed and assembled into a CR2032 battery at a pressure of 50 to 70 MPa for electrochemical performance testing.

[0031] Compared with the prior art, the technical solution of this application has the following advantages:

[0032] 1. This application proposes a manganese-iodine composite material based on the synergistic effect of activated carbon, manganese dioxide (MnO2) and iodine. Iodide and a conductive agent are first treated with solvent heat, and then manganese oxide is added. This can effectively avoid the adverse reaction of the oxide at high temperature, and accurately regulate the interaction and spatial distribution of the three components (manganese, iodine, and conductive agent), ensuring the close combination of the conductive agent and the active substance, which is the core of achieving the "high conductivity" of the material. In this process, the positive charge characteristics of the manganese dioxide surface and the adsorption capacity of activated carbon synergize to promote the close combination of iodide, manganese dioxide and the conductive agent to form a composite structure with a continuous conductive network and a stable interface. This structure not only improves the electronic conduction efficiency of the material, but also suppresses the loss of active substances through the dual mechanisms of chemical bonding and physical adsorption, significantly enhancing the electrochemical stability of the material.

[0033] 2. The manganese-iodine composite material provided in this application significantly improves the specific capacity and cycle stability of the manganese oxide positive electrode of aqueous zinc ion batteries, as shown in the following: Figure 3 , 4, there is an obvious iodine (I - / I 0 ) redox platform, indicating that the introduction of iodine provides additional electrochemical active sites, significantly improving the specific capacity of the material. Compared with the unmodified manganese dioxide positive electrode, its specific capacity is significantly increased, showing a higher energy density. Figure 8 As shown, at 1.0Ag -1 At a current density of 1.5 volts, after 2000 charge-discharge cycles, the capacity retention rate of the positive electrode material of Example 1 was almost perfectly maintained at 100%, and its specific capacity was still as high as 318 mAh g -1 , showing excellent cycle stability. This excellent performance is mainly due to the dual synergistic effect of ions and electrons generated by the introduction of iodine, which effectively suppresses the influence of by-products during the discharge process and significantly improves the reversibility of the reaction; at the same time, the stable conductive network formed by the three components of manganese, iodine and conductive agent further enhances the overall structural stability of the material. Figure X As shown, the positive electrode material of Example 9 is 0.5, 1.0, 1.5, 2.0, 3.0, 5.0 and 10.0Ag -1 At current densities of 1, 2, 3, 4, 5, 7, 8, 11, 12, 15, 16, and 133.2 mAh g -1 Its high capacity output and stable performance with current density change are significantly better than the unmodified manganese dioxide positive electrode (Comparative Example 1), fully demonstrating the excellent performance of manganese-iodine composite materials at high rates. Figure 10 , 11, at 5000mAg -1 At a high current density of , the cathode material of Example 1 exhibited amazing long-cycle stability. After 60,000 charge and discharge cycles, its capacity retention rate was still as high as 64%, and its specific capacity remained at a good level. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The scanning electron microscope image and EDS of the manganese-iodine composite material provided in Example 1 of the present application;

[0035] Figure 2 The I3d XPS spectrum of the positive electrode material provided in Example 1 and Comparative Example 1 of the present application;

[0036] Figure 3 Cyclic voltammetry curves of the positive electrode materials provided in Example 1 and Comparative Example 1 of the present application;

[0037] Figure 4 In Example 1 of this application, the positive electrode material provided in Comparative Example 1 is 0.5Ag -1 Charge and discharge curves under current density;

[0038] Figure 5 This is the electrochemical impedance spectrum of the positive electrode material provided in Example 1 and Comparative Example 1 of the present application in the fully discharged state.

[0039] Figure 6 This is a constant current intermittent titration technique (GITT) curve of the positive electrode material provided in Example 1 and Comparative Example 1 of the present application.

[0040] Figure 7 The ion diffusion coefficients of the positive electrode materials provided in Example 1 and Comparative Example 1 of the present application at different potentials.

[0041] Figure 8 The positive electrode material provided in Example 1 and Comparative Example 1 of the present application is used as the positive electrode of a zinc ion battery at a current density of 1000 mA per gram (abbreviated as @1.0Ag -1 ) under long charge and discharge cycle diagram (the arrow on the left corresponds to the specific capacity under different cycle numbers, and the arrow on the right corresponds to the coulomb efficiency under different cycle numbers);

[0042] Figure 9 The electrochemical rate performance diagram of the positive electrode materials provided in Example 1 and Comparative Example 1 of the present application as the positive electrode of the zinc ion battery, the current density is 0.5, 1, 1.5, 2, 3, 5, 10A respectively -1 ;

[0043] Figure 10 The positive electrode materials provided in Example 1 and Comparative Example 1 of the present application were respectively used as positive electrodes of zinc ion batteries at a current density of 5000 mA per gram (abbreviated as @5.0Ag -1 )’s charge and discharge long cycle comparison chart;

[0044] Figure 11 The positive electrode materials provided in Example 1 and Comparative Example 1 of the present application are respectively used as the positive electrode of the zinc ion battery at a current density of 5000 mA per gram (abbreviated as @5.0Ag -1 ) is a long-cycle charge-discharge comparison diagram (the two curves near the arrow on the left are the specific capacities of MnO2-I and MnO2 positive electrodes at different numbers of cycles, and the arrow on the right is the coulombic efficiency of MnO2-I and MnO2 positive electrodes at different numbers of cycles). DETAILED DESCRIPTION

[0045] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0046] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this application can be purchased commercially or prepared by existing methods. Experimental methods in the following examples, where specific conditions are not specified, are generally measured in accordance with national standards. Where no corresponding national standards are available, the methods were performed in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[0047] The manganese dioxide used in the examples and comparative examples was purchased and characterized to show that it was tunnel-type manganese dioxide with nanowires of 50 to 500 nanometers in length.

[0048] Example 1

[0049] A method for preparing a positive electrode material, the method comprising:

[0050] S1. Place zinc iodide and activated carbon in a mortar at a ratio of 2:1 and grind thoroughly until a fine powder is formed. Add an appropriate amount of solvent to the powder and stir to form a uniformly dispersed solution. Transfer the mixed solution to a sealed reactor, heat it in an oven to 120°C, and react for 2 hours.

[0051] S2. After the reaction is completed, the reactor is cooled naturally to room temperature, and a certain amount of manganese dioxide is added to the solution in the reactor and stirred thoroughly.

[0052] S3. The resulting mixed slurry is centrifuged to collect a solid product. The solid product is repeatedly washed with deionized water to remove impurities. The washed solid product is freeze-dried to obtain the highly conductive manganese-iodine composite material.

[0053] S4. Mix the highly conductive manganese-iodine composite material: conductive agent (carbon nanotubes): binder (polyvinylidene fluoride, PVDF) in a mass ratio of 8:1:1, add N-methylpyrrolidone (NMP), grind and mix evenly, coat it on the carbon cloth current collector, and dry it at 60°C for 12 hours to obtain a manganese-iodine positive electrode material (MnO2-I).

[0054] Example 2

[0055] S1. Place ammonium iodide and activated carbon in a mortar at a ratio of 1:1 and grind thoroughly until a fine powder is formed. Add an appropriate amount of solvent to the powder and stir to form a uniformly dispersed solution. Transfer the mixed solution to a sealed reactor, heat it in an oven to 120°C, and react for 4 hours.

[0056] S2. After the reaction is completed, the reactor is cooled naturally to room temperature, and a certain amount of manganese dioxide is added to the solution in the reactor and stirred thoroughly.

[0057] S3. The resulting mixed slurry is centrifuged to collect a solid product. The solid product is repeatedly washed with deionized water to remove impurities. The washed solid product is freeze-dried to obtain the highly conductive manganese-iodine composite material.

[0058] S4. Mix the highly conductive manganese-iodine composite material: conductive agent (carbon nanotubes): binder (carboxymethyl cellulose, CMC) in a mass ratio of 8:1:1, add N-methylpyrrolidone (NMP), grind and mix evenly, then coat it on a carbon cloth current collector and dry it at 60°C for 12 hours to obtain a manganese-iodine positive electrode material (MnO2-I).

[0059] Example 3

[0060] S1. Place iodine and activated carbon in a mortar at a ratio of 1:1 and grind thoroughly until a fine powder is formed. Add an appropriate amount of solvent to the powder and stir to form a uniformly dispersed solution. Transfer the mixed solution to a sealed reactor, heat it in an oven to 120°C, and react for 4 hours.

[0061] S2. After the reaction is completed, the reactor is cooled naturally to room temperature, and a certain amount of manganese dioxide is added to the solution in the reactor and stirred thoroughly.

[0062] S3. The resulting mixed slurry is centrifuged to collect a solid product. The solid product is repeatedly washed with deionized water to remove impurities. The washed solid product is freeze-dried to obtain the highly conductive manganese-iodine composite material.

[0063] S4. Mix the highly conductive manganese-iodine composite material: conductive agent (YP-80F): binder (carboxymethyl cellulose, CMC) in a mass ratio of 8:1:1, add N-methylpyrrolidone (NMP), grind and mix well, then coat it on a carbon cloth current collector and dry it at 60°C for 12 hours to obtain a manganese-iodine positive electrode material (MnO2-I).

[0064] Example 4

[0065] S1. Place iodine and activated carbon in a mortar at a ratio of 1:1 and grind thoroughly until a fine powder is formed. Add an appropriate amount of solvent to the powder and stir to form a uniformly dispersed solution. Transfer the mixed solution to a sealed reactor, heat it in an oven to 120°C, and react for 4 hours.

[0066] S2. After the reaction is completed, the reactor is cooled naturally to room temperature, and a certain amount of manganese trioxide is added to the solution in the reactor and stirred thoroughly.

[0067] S3. The resulting mixed slurry is centrifuged to collect a solid product. The solid product is repeatedly washed with deionized water to remove impurities. The washed solid product is freeze-dried to obtain the highly conductive manganese-iodine composite material.

[0068] S4. Mix the highly conductive manganese-iodine composite material: conductive agent (acetylene black): binder (polytetrafluoroethylene, PTFE) in a mass ratio of 8:1:1, add N-methylpyrrolidone (NMP), grind and mix evenly, coat it on the carbon cloth current collector, and dry it at 60°C for 12 hours to obtain a manganese-iodine positive electrode material (MnO2-I).

[0069] Comparative Example 1

[0070] Manganese dioxide: conductive agent: binder (polyvinylidene fluoride, PVDF) were added to NMP in a mass ratio of 7:2:1, ground and mixed, coated on carbon cloth, and dried at 80°C for 24 hours to obtain a manganese dioxide positive electrode material.

[0071] Material characterization and performance testing:

[0072] Scanning electron microscopy tests were performed on the positive electrode materials provided in Examples 1 to 4 and Comparative Example 1. Since the results are similar, only the test results of Example 1 are used as an example below.

[0073] Figure 1 SEM and EDS images of the manganese-iodine cathode material provided in Example 1. This cathode material consists of a unique nanoflower-like manganese dioxide, massive activated carbon, and linear carbon nanotubes that synergistically form a conductive network supporting the overall structure. EDS analysis confirms the uniform distribution of manganese dioxide, iodine, and carbon.

[0074] Figure 2 The comparison of the I3d XPS spectra of the positive electrode materials of Example 1 and Comparative Example 1 is shown, in which the MnO2-I composite material shows obvious I3d5 / 2 and I3d3 / 2 characteristic double peaks at binding energies of 620.5eV and 632.5eV, respectively. This characteristic signal confirms that the iodine element has been successfully introduced into the material system.

[0075] Figure 3The cyclic voltammetry curves of the positive electrode materials provided for Example 1 and Comparative Example 1 show that the redox peak potential difference of the sample with iodine introduced is significantly reduced, indicating that the incorporation of iodine effectively reduces the overpotential of the electrode reaction and promotes the electrochemical conversion kinetics.

[0076] Figure 4 In Example 1 of this application, the positive electrode material provided in Comparative Example 1 is 0.5Ag -1 The charge-discharge curves under different current densities show that the MnO2-I cathode material has obvious charging platforms at 1.4V and 1.75V, and the specific capacity is significantly increased to 330mAh g -1 , confirming that the introduction of iodine effectively promoted the electrochemical conversion of the material and improved the reaction reversibility.

[0077] Figure 6 This is a constant current intermittent titration technique (GITT) curve of the positive electrode material provided in Example 1 and Comparative Example 1 of the present application.

[0078] Figure 7 The ion diffusion coefficients of the positive electrode materials provided in Example 1 and Comparative Example 1 of the present application at different potentials.

[0079] Figure 5 The electrochemical impedance spectrum of the positive electrode material provided in Example 1 and Comparative Example 1 of the present application under full discharge state shows that the charge transfer resistance of MnO2-I is significantly reduced to 20 ohms, which is much lower than the 1000 ohms of MnO2, indicating that the introduction of iodine not only greatly improves the electronic conductivity of the material, but also effectively reduces the charge transfer impedance at the electrode interface, significantly improves the reaction kinetics and inhibits the occurrence of side reactions.

[0080] Figure 6 Comparison of the galvanostatic intermittent titration technique (GITT) curves for the cathode materials provided in Example 1 and Comparative Example 1 of this application. The results show that MnO2-I exhibits a stable relaxation time, which confirms that the material has excellent capacity retention and can effectively suppress rapid self-discharge in a short period of time, demonstrating the stability of the material. Figure 7 The ion diffusion coefficients of the positive electrode materials provided in Example 1 and Comparative Example 1 of the present application at different potentials are shown. It is found that MnO2-I exhibits a higher ion diffusion rate in all test potential ranges, wherein the diffusion coefficient reaches 1.0×10 -9 cm 2 / s, compared with MnO2 material (1.0×10 -11 cm 2 / s) increased by nearly two orders of magnitude, which is consistent with Figure 6 The excellent electrochemical properties observed in the experiments confirm each other, fully demonstrating the significant effect of iodine modification on improving the ion transport kinetics of the material.

[0081] The positive electrode materials provided in Examples 1 to 4 were subjected to long-term charge and discharge cycle tests. Since the results are similar, only the test results of Example 1 are used as an example below. Figure 8 The positive electrode material provided in Example 1 and Comparative Example 1 is used as the positive electrode of the zinc ion battery at 500mAg -1 The long charge and discharge cycle conditions under current density. Figure 8 It can be seen that at a current density of 1.0Ag -1 Under the conditions of 1000 charge and discharge cycles, it can be clearly observed that the modified MnO2-I cathode material exhibits nearly perfect electrochemical stability, with its capacity retention rate always maintained at 100% of the initial level and the discharge specific capacity maintained at 318 mAh g -1 This excellent performance fully demonstrates the material's excellent structural stability and cycle durability. The performance of the unmodified MnO2 cathode material under the same test conditions was significantly inferior. After 2000 cycles, its capacity retention rate had decayed to 60% of the initial value, and the discharge capacity was significantly reduced to 90 mAh g -1 .

[0082] Charge and discharge tests were performed on the positive electrode materials provided in Examples 1 to 4. Since the results are similar, only the test results of Example 4 are used as an example below. Figure 9 The rate performance test results of the positive electrode material provided in Example 4 at different current densities are shown in Figure 4. The current densities used for constant current charge and discharge are 0.5, 1, 1.5, 2, 3, 5, and 10A respectively. -1 The positive electrode material of Example 1 (MnO2-I in the figure) is 0.5, 1, 1.5, 2, 3, 5, 10Ag -1 The average discharge capacities were 310.5, 271.9, 242.0, 231.6, 195.7, 165.5 and 133.2 mAh g -1 It is worth noting that even at 10Ag -1 At an ultra-high current density of 133.2 mAh g -1 The impressive capacity of the MnO2-I material demonstrates excellent high current tolerance and stable capacity retention characteristics. In contrast, the unmodified MnO2 positive electrode material exhibits obvious performance disadvantages under the same test conditions, especially under high current density conditions, where its capacity shows a trend of rapid attenuation. This significant performance difference is mainly attributed to the byproducts produced by MnO2 during the discharge process, which leads to an increase in the electrode interface impedance, thereby causing severe polarization and irreversible capacity loss. The excellent rate performance of the MnO2-I material fully demonstrates the significant effect of the iodine modification strategy in inhibiting side reactions and reducing interfacial impedance.

[0083] Figure 10 , 11 is the positive electrode material of Example 1-4 as the zinc ion positive electrode material in 5000mAg -1 The charge and discharge cycle diagram under high current density and the charge and discharge curves of different cycles. -1 Under ultra-high current density test conditions, the MnO2-I series materials showed amazing cycle stability: its initial discharge capacity was 150 mAh g -1 , after 60,000 ultra-long cycles, it can still maintain 80mAh g -1 This excellent performance is significantly better than that of the unmodified MnO2 material (initial capacity 100mAh g -1 After the cycle, only 25 mAh g -1 The introduction of iodine significantly improves material performance through multiple synergistic mechanisms. On the one hand, the stable chemical bonds formed between iodine and manganese dioxide construct a three-dimensional conductive network, significantly improving electron transfer efficiency. On the other hand, the synergistic reaction mechanism of iodine and manganese dioxide not only promotes the reversible insertion / extraction of ions, but also effectively suppresses the occurrence of side reactions by regulating the interfacial electrochemical environment. This unique synergistic mechanism achieves the simultaneous optimization of electron conduction and ion transport, reduces the reaction activation energy barrier, and thus significantly improves the electrode reaction kinetics.

Claims

1. A manganese-iodine composite material, characterized in that The manganese-iodine composite material comprises iodide, a conductive agent and manganese oxide.

2. The manganese-iodine composite material according to claim 1, characterized in that The mass ratio of the iodide to the manganese oxide is (0.1-0.5):

1.

3. The manganese-iodine composite material according to claim 1, characterized in that The manganese oxide is one or more of manganese dioxide, dimanganese trioxide or trimanganese tetraoxide.

4. The manganese-iodine composite material according to claim 1, characterized in that The iodide is one or more of zinc iodide, potassium iodide, elemental iodine, and ammonium iodide.

5. A method for preparing a manganese-iodine composite material, characterized in that: The method comprises the following steps: Grind the iodide and conductive agent evenly and add them to the solvent. After sufficient stirring, transfer them to a reactor and heat to 120°C for two hours. After cooling, add manganese oxide to the solution and stir thoroughly; After the reaction is completed, the solid and liquid are separated and freeze-dried to obtain the manganese-iodine composite material.

6. Use of the manganese-iodine composite material according to claims 1 to 5 as a positive electrode material for zinc ion batteries.

7. A method for preparing a positive electrode material, characterized in that: The preparation method comprises the following steps: adding the manganese-iodine composite material according to any one of claims 1 to 5: a conductive agent: a binder in a mass ratio of (7-8): (2-1): 1 to a solvent, grinding and mixing, coating the mixture on a current collector, and drying to obtain a positive electrode material.

8. A positive electrode sheet, characterized in that: The positive electrode sheet comprises: a positive electrode material layer; the positive electrode material layer comprises the manganese-iodine composite material according to any one of claims 1 to 4 or the positive electrode material prepared by the preparation method according to any one of claims 5 to 9.

9. A zinc ion battery, characterized in that: The battery comprises the positive electrode sheet according to claim 8.

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