Porous activated carbon confined growth high-capacity manganese dioxide nanorod as well as preparation method and application thereof

Abstract

The invention discloses a porous activated carbon confined growth high-capacity manganese dioxide nanorod as well as a preparation method and application thereof, and belongs to the technical field of energy and storage. Porous activated carbon (AC) is added as a structure limiting agent, and the high-capacity manganese dioxide nanorod is prepared by a hydrothermal synthesis method and is used as a positive electrode material of an aqueous zinc ion battery; the method disclosed by the invention is simple in preparation process, and the nanorod prepared by the method disclosed by the invention has excellent electrochemical performance, long cycle stability and relatively high rate capability.

Description

Technical Field

[0001] This invention relates to a method for confined growth of high-capacity manganese dioxide nanorods in porous activated carbon, its preparation method, and its applications, belonging to the field of energy and storage technology. Background Technology

[0002] Among currently used energy storage devices, aqueous zinc-ion batteries are considered one of the most promising alternatives to lithium-ion batteries due to their high theoretical capacity, high safety, and environmental friendliness. However, aqueous zinc-ion batteries suffer from numerous drawbacks, such as short cycle life and low energy density, preventing them from meeting the requirements for industrialization.

[0003] Therefore, researchers have explored many materials for the cathode of aqueous zinc-ion batteries, such as vanadium-based materials, manganese-based materials, and Prussian blue analogues. Among these materials, manganese-based materials are considered the most commercially viable cathode materials due to their wide operating voltage range, low cost, and environmental friendliness. Unfortunately, problems such as low conductivity, numerous side reactions, and manganese dissolution have hindered the further application of manganese-based materials.

[0004] Therefore, researchers have explored numerous methods to improve these issues, including: doping with metal and non-metal ions to increase lattice spacing and promote zinc ion insertion and extraction; adding carbon materials such as carbon nanotubes during manganese dioxide synthesis to enhance conductivity; and altering the morphology of manganese dioxide under different hydrothermal conditions to achieve better results. These methods have all played a positive role in improving the electrochemical performance of manganese dioxide as a cathode material in aqueous zinc-ion batteries to some extent, but its commercialization in aqueous zinc-ion batteries remains a long way off.

[0005] α-MnO2, β-MnO2, and δ-MnO2 are three common crystal forms of manganese dioxide materials. Among them, α-MnO2 with a nanowire morphology is used as the cathode material in aqueous zinc-ion batteries because its higher specific surface area allows for more thorough contact with the electrolyte. The layered structure of δ-MnO2 has been shown to have a more kinetically favorable transition from layered to layered structure during cycling compared to Zn. 2+ The storage of zinc ions has attracted widespread attention. However, research on β-MnO2 is relatively limited. β-MnO2 has a high theoretical capacity and thermodynamic stability, making it a promising cathode material for aqueous zinc-ion batteries. However, its tunnel structure is relatively narrow, which is theoretically unfavorable for the storage of Zn. 2+ Because of its embedding, it is not widely used in the field of aqueous zinc-ion batteries. Summary of the Invention

[0006] To address some shortcomings of the existing technologies, the present invention aims to provide a method for confining and growing high-capacity manganese dioxide nanorods using porous activated carbon (AC). This method involves adding different masses of high-capacity porous activated carbon as structural confinement agents to synthesize β-MnO2. The AC-MnO2 (β-MnO2) prepared by the method of the present invention exhibits excellent electrochemical performance, long-term cycling stability, and high rate performance.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: This invention first provides a method for preparing high-capacity manganese dioxide nanorods by confined growth of porous activated carbon (AC), the method comprising: KMnO4 and porous activated carbon (AC) were thoroughly mixed in deionized water and ultrasonically dispersed to obtain a mixture of KMnO4 and AC. The amounts of KMnO4, AC, and deionized water are 8 mmol: 0.01 g - 0.09 g: 35 mL; the thorough mixing is carried out by magnetic stirring, and the ultrasonic power is 50 W for 30 min.

[0008] Dissolve MnCl2·4H2O completely in deionized water, and add sulfuric acid solution dropwise while stirring to obtain an acidified MnCl2·4H2O solution. The ratio of MnCl2·4H2O to deionized water is 8 mmol: 35 mL; the mixing is performed using magnetic stirring; the concentration of sulfuric acid is 0.5 mol / L, and the amount added is 1 mL.

[0009] A mixture of KMnO4 and AC was added to an acidified MnCl2·4H2O solution. After stirring and mixing, the mixture was allowed to react completely and then cooled to room temperature. The precipitate was collected, washed, and dried to obtain high-capacity manganese dioxide nanorods grown in confined space by porous activated carbon (AC).

[0010] The reaction is carried out at 180°C for 6 hours.

[0011] The washing process involves washing with deionized water and ethanol, and the drying process involves drying at 70°C for 12 hours.

[0012] The present invention also provides high-capacity manganese dioxide nanorods prepared by the method in a confined environment using porous activated carbon (AC).

[0013] The present invention also provides the application of the porous activated carbon (AC) confined growth of high-capacity manganese dioxide nanorods in the cathode material of aqueous zinc-ion batteries.

[0014] Furthermore, the method for preparing the cathode material includes: The porous activated carbon (AC) confined growth of high-capacity manganese dioxide nanorods, conductive agent and binder are weighed in a certain proportion, and then N-methylpyrrolidone (dispersant) is added and stirred. The stirred mixture is evenly coated on carbon cloth and then placed in an oven to dry at 80°C. After about 30 minutes, it is taken out and cut into the same size as zinc sheets.

[0015] Furthermore, the conductive agent is carbon black, the binder is PVDF, and the porous activated carbon (AC) confines the growth of high-capacity manganese dioxide nanorods, the conductive agent and the binder are in a mass ratio of 7:2:1.

[0016] The present invention also provides an aqueous zinc-ion battery, wherein the aqueous zinc-ion battery uses the high-capacity manganese dioxide nanorod cathode material grown in the porous activated carbon (AC) as the cathode.

[0017] Furthermore, the aqueous zinc-ion battery uses a zinc sheet as the negative electrode and a mixture of ZnSO4 and MnSO4 as the electrolyte, wherein the concentration of ZnSO4 is 2 mol·L⁻¹. -1 The concentration of MnSO4 is 0.1 mol·L⁻¹ -1 .

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] This invention synthesizes β-MnO2, abbreviated as AC-MnO2, via a one-step hydrothermal method with the addition of acetic acid (AC) as a structure-limiting agent. α-MnO2 nanowires are then generated using the same hydrothermal synthesis method without AC. Compared to α-MnO2 without AC, the AC-MnO2 synthesized in this invention exhibits superior electrochemical performance, with the best results observed when 0.05 g of AC is added. The addition of AC allows the generated AC-MnO2 to serve as the positive electrode in an aqueous zinc-ion battery, ensuring a higher specific capacity at 0.5 A g. -1 At the energy density, after 200 cycles, the specific capacity of the battery with α-MnO2 as the positive electrode without AC is only 51% of the initial capacity, while the specific capacity of the battery with AC-MnO2 generated by this invention as the positive electrode can reach 96% of the initial capacity, an increase from 51% to 96%. This provides a way of thinking for the modification of β-MnO2 positive electrode materials and also provides a reference for changing the crystal form of materials. Attached Figure Description

[0020] Figure 1 XRD diffraction pattern of MnO2 without added AC prepared in Example 1 ( Figure 1 (above) and the XRD diffraction pattern of AC-MnO2 prepared in Example 4 ( Figure 1 (Down)).

[0021] Figure 2 SEM image of MnO2 without added AC prepared in Example 1 ( Figure 2 (above) and SEM images of AC-MnO2 prepared in Example 4 ( Figure 2 (Down)).

[0022] Figure 3 The specific capacity-voltage comparison graph shows the MnO2 without added AC prepared in Example 1, and the AC-MnO2 prepared in Examples 3 (0.03g AC-MnO2), 4 (AC-MnO2), and 6 (0.08g AC-MnO2).

[0023] Figure 4 A comparison chart of the rate performance of MnO2 without added AC prepared in Example 1 and AC-MnO2 prepared in Example 4.

[0024] Figure 5 The MnO2 without added AC prepared in Example 1 and the AC-MnO2 prepared in Example 4 were compared at 0.5A g. -1 Cyclic comparison graph under current density. Detailed Implementation

[0025] The technical solutions of the present invention will be further described below through specific embodiments. It should be understood that these embodiments are preferred solutions of the present invention and are intended to aid in understanding the technical content of the present invention, rather than limiting the scope of protection of the present invention. Without departing from the basic concept of the present invention, various substitutions, equivalent improvements, or combinations can be made by those skilled in the art, and all such substitutions, equivalent improvements, or combinations should be considered to fall within the scope of protection of the present invention.

[0026] 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 those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0027] Example 1: A method for preparing α-MnO2 material Weigh 8 mmol of KMnO4 and place it in a beaker containing 35 mL of deionized water. Stir with a magnetic stirrer for 10 minutes, and then sonicate for about 30 minutes to disperse it evenly.

[0028] While performing the ultrasound, weigh 8 mmol of MnCl2·4H2O and dissolve it in 35 mL of deionized water. Place the solution directly on a magnetic stirrer and stir for 30 minutes to ensure complete dissolution.

[0029] Prepare a 0.5 mol / L sulfuric acid solution in advance: Take 1 mL of 95% sulfuric acid and add it dropwise to 34.6 mL of deionized water, then stir thoroughly for about 20 minutes.

[0030] 1 mL of the prepared 0.5 mol / L sulfuric acid was added dropwise to the stirred MnCl2·4H2O to obtain an acidified MnCl2·4H2O solution.

[0031] The ultrasonically mixed KMnO4 solution was then poured into the acidified MnCl2·4H2O solution, and the mixture was stirred continuously until fully homogenized. The homogenized reaction solution was then poured into a 100 mL reactor and reacted at 180 °C for 6 h. After the reaction was complete, the mixture was cooled to room temperature, washed with deionized water and ethanol, and finally dried at 70 °C for 12 h to obtain the α-MnO2 material.

[0032] Finally, the obtained material was mixed with α-MnO2 material, conductive agent, and binder at a mass ratio of 7g:2g:1g, and an appropriate amount of N-methylpyrrolidone (1mL) was added and stirred. After thorough stirring, the mixture was coated onto carbon cloth and then dried at 80℃. After complete drying, it was cut into pieces of the same size as the zinc sheet, 14mm × 14mm.

[0033] The α-MnO2 material loaded on carbon cloth obtained in this embodiment was used as the positive electrode of an aqueous zinc-ion battery. Example 2: A method for preparing high-capacity manganese dioxide nanorods by confined growth of porous activated carbon (AC).

[0034] Weigh 8 mmol of KMnO4 and place it in a beaker containing 35 mL of deionized water. Add 0.01 g of porous activated carbon (AC, Aladdin, catalog number: C196580-5) and stir with a magnetic stirrer for 10 minutes to mix the two thoroughly. Then sonicate for about 30 minutes to disperse the mixture evenly, thus obtaining a KMnO4 and AC mixture.

[0035] During the ultrasound process described above, weigh out 8 mmol of MnCl2·4H2O and dissolve it in 35 mL of deionized water. Place the solution directly on a magnetic stirrer and stir for 30 minutes to ensure complete dissolution.

[0036] Prepare a 0.5 mol / L sulfuric acid solution in advance: Take 1 mL of 95% sulfuric acid and add it dropwise to 34.6 mL of deionized water, then stir thoroughly for about 20 minutes.

[0037] Take 1 mL of the prepared 0.5 mol / L sulfuric acid and add it dropwise to the MnCl2·4H2O solution that is being stirred. After stirring is complete, the acidified MnCl2·4H2O solution is obtained.

[0038] The ultrasonically mixed KMnO4 and AC mixture was poured into an acidified MnCl2·4H2O solution and stirred continuously until fully mixed. The mixed solution was then poured into a 100 mL reactor and reacted at 180 °C for 6 h. After the reaction was complete, the mixture was cooled to room temperature, washed with deionized water and ethanol, and finally dried at 70 °C for 12 h to obtain high-capacity manganese dioxide nanorods confined within porous activated carbon (AC). Based on the amount of porous activated carbon (AC) used, this was recorded as 0.01 g AC-MnO2.

[0039] Finally, the obtained material was mixed with 0.01g AC-MnO2 material, conductive agent, and binder in a mass ratio of 7g:2g:1g, and an appropriate amount of N-methylpyrrolidone (1mL) was added and stirred. After thorough stirring, the mixture was coated onto carbon cloth and then dried at 80℃. After complete drying, it was cut into pieces of the same size as the zinc sheet, 14mm × 14mm.

[0040] The 0.01g AC-MnO2 loaded on carbon cloth obtained in this embodiment was used as the positive electrode of an aqueous zinc-ion battery. Example 3: A method for preparing high-capacity manganese dioxide nanorods by confined growth of porous activated carbon (AC).

[0041] Weigh 8 mmol of KMnO4 and place it in a beaker containing 35 mL of deionized water. Add 0.03 g of AC and stir with a magnetic stirrer for 10 minutes to mix the two thoroughly. Then sonicate for about 30 minutes to disperse the mixture evenly, thus obtaining a KMnO4 and AC mixture.

[0042] During the ultrasound process, 8 mmol of MnCl2·4H2O was weighed and dissolved in 35 mL of deionized water. The solution was then placed directly on a magnetic stirrer and stirred for 30 minutes to ensure complete dissolution.

[0043] Prepare a 0.5 mol / L sulfuric acid solution in advance: Take 1 mL of 95% sulfuric acid and add it dropwise to 34.6 mL of deionized water, then stir thoroughly for about 20 minutes.

[0044] Take 1 mL of the prepared 0.5 mol / L sulfuric acid and add it dropwise to the MnCl2·4H2O solution that is being stirred. After stirring is completed, the acidified MnCl2·4H2O solution is obtained.

[0045] Pour the ultrasonicated KMnO4 and AC mixture into the acidified MnCl2·4H2O solution and continue mixing and stirring until it is fully mixed.

[0046] The mixed solution was poured into a 100 mL reactor and reacted at 180 °C for 6 h. After the reaction was complete, it was cooled to room temperature, washed with deionized water and ethanol, and finally dried at 70 °C for 12 h to obtain high-capacity manganese dioxide nanorods confined in porous activated carbon (AC). Based on the amount of porous activated carbon (AC) used, it was recorded as 0.03 g AC-MnO2.

[0047] Finally, the obtained material was mixed with 0.03g AC-MnO2 material, conductive agent, and binder in a mass ratio of 7g:2g:1g, and an appropriate amount of N-methylpyrrolidone (1mL) was added and stirred. After thorough stirring, the mixture was coated onto carbon cloth and then dried at 80℃. After complete drying, it was cut into pieces of the same size as the zinc sheet, 14mm × 14mm.

[0048] The 0.03g AC-MnO2 material loaded on carbon cloth obtained in this embodiment was used as the positive electrode of an aqueous zinc-ion battery.

[0049] Weigh 8 mmol of KMnO4 and place it in a beaker containing 35 mL of deionized water. Add 0.05 g of AC and stir with a magnetic stirrer for 10 minutes to mix the two thoroughly. Then sonicate for about 30 minutes to disperse the mixture evenly, thus obtaining a KMnO4 and AC mixture.

[0050] During the ultrasound process, 8 mmol of MnCl2·4H2O was weighed and dissolved in 35 mL of deionized water. The solution was then placed directly on a magnetic stirrer and stirred for 30 minutes to ensure complete dissolution.

[0051] Prepare a 0.5 mol / L sulfuric acid solution in advance: Take 1 mL of 95% sulfuric acid and add it dropwise to 34.6 mL of deionized water, then stir thoroughly for about 20 minutes.

[0052] Take 1 mL of the prepared 0.5 mol / L sulfuric acid and add it dropwise to the stirred MnCl2·4H2O. After stirring is completed, the acidified MnCl2·4H2O solution is obtained.

[0053] The ultrasonicated KMnO4 and AC mixture was poured into an acidified MnCl2·4H2O solution and stirred continuously until fully mixed. The mixed solution was then poured into a 100mL reactor and reacted at 180℃ for 6 hours. After the reaction was complete, the mixture was cooled to room temperature, washed with deionized water and ethanol, and finally dried at 70℃ for 12 hours to obtain high-capacity manganese dioxide nanorods confined in porous activated carbon (AC). Based on the amount of porous activated carbon (AC) used, this was recorded as 0.05g of AC-MnO2 material.

[0054] Finally, the obtained material was mixed with 0.05g of AC-MnO2 material, conductive agent, and binder in a mass ratio of 7g:2g:1g, and an appropriate amount of N-methylpyrrolidone (1mL) was added and stirred. After thorough stirring, the mixture was coated onto carbon cloth and then dried at 80℃. After complete drying, it was cut into pieces of the same size as the zinc sheet, 14mm × 14mm.

[0055] The 0.05g AC-MnO2 loaded on carbon cloth obtained in this embodiment was used as the positive electrode of an aqueous zinc-ion battery. Example 5: A method for preparing high-capacity manganese dioxide nanorods by confined growth of porous activated carbon (AC).

[0056] Weigh 8 mmol of KMnO4 and place it in a beaker containing 35 mL of deionized water. Add 0.07 g of AC and stir with a magnetic stirrer for 10 minutes to mix the two thoroughly. Then sonicate for about 30 minutes to disperse the mixture evenly, thus obtaining a KMnO4 and AC mixture.

[0057] During the ultrasound process, simultaneously weigh 8 mmol of MnCl2·4H2O and dissolve it in 35 mL of deionized water. Place the solution directly on a magnetic stirrer and stir for 30 minutes to ensure complete dissolution.

[0058] Prepare a 0.5 mol / L sulfuric acid solution in advance: Take 1 mL of 95% sulfuric acid and add it dropwise to 34.6 mL of deionized water, then stir thoroughly for about 20 minutes.

[0059] Take 1 mL of the prepared 0.5 mol / L sulfuric acid and add it dropwise to the stirred MnCl2·4H2O. After stirring is completed, the acidified MnCl2·4H2O solution is obtained.

[0060] The ultrasonicated KMnO4 and AC mixture was poured into an acidified MnCl2·4H2O solution and stirred continuously until fully mixed. The mixed solution was then poured into a 100mL reactor and reacted at 180℃ for 6 hours. After the reaction was complete, the mixture was cooled to room temperature, washed with deionized water and ethanol, and finally dried at 70℃ for 12 hours to obtain high-capacity manganese dioxide nanorods confined within porous activated carbon (AC). Based on the amount of porous activated carbon (AC) used, this was recorded as 0.07g AC-MnO2.

[0061] Finally, the obtained material was mixed with 0.07g AC-MnO2 material, conductive agent, and binder in a mass ratio of 7g:2g:1g, and an appropriate amount of N-methylpyrrolidone (1mL) was added and stirred. After thorough stirring, the mixture was coated onto carbon cloth and then dried at 80℃. After complete drying, it was cut into pieces of the same size as the zinc sheet, 14mm × 14mm.

[0062] The 0.07g AC-MnO2 material loaded on carbon cloth obtained in this embodiment was used as the positive electrode of an aqueous zinc-ion battery. Example 6: A method for preparing high-capacity manganese dioxide nanorods by confined growth of porous activated carbon (AC).

[0063] Weigh 8 mmol of KMnO4 and place it in a beaker containing 35 mL of deionized water. Add 0.08 g of AC and stir with a magnetic stirrer for 10 minutes to mix the two thoroughly. Then sonicate for about 30 minutes to disperse the mixture evenly, thus obtaining a KMnO4 and AC mixture.

[0064] During the ultrasound process, simultaneously weigh 8 mmol of MnCl2·4H2O and dissolve it in 35 mL of deionized water. Place the solution directly on a magnetic stirrer and stir for 30 minutes to ensure complete dissolution.

[0065] Prepare a 0.5 mol / L sulfuric acid solution in advance: Take 1 mL of 95% sulfuric acid and add it dropwise to 34.6 mL of deionized water, then stir thoroughly for about 20 minutes.

[0066] Take 1 mL of the prepared 0.5 mol / L sulfuric acid and add it dropwise to the stirred MnCl2·4H2O. After the stirring is completed, the acidified MnCl2·4H2O solution is obtained.

[0067] The ultrasonicated KMnO4 and AC mixture was poured into an acidified MnCl2·4H2O solution and stirred continuously until fully mixed. The resulting solution was then poured into a 100mL reactor and reacted at 180℃ for 6 hours. After the reaction was complete, the mixture was cooled to room temperature, washed with deionized water and ethanol, and finally dried at 70℃ for 12 hours to obtain high-capacity manganese dioxide nanorods confined within porous activated carbon (AC). This 0.08g AC-MnO2 material is suitable for use in aqueous zinc-ion batteries.

[0068] Finally, the obtained material was mixed with 0.08g of AC-MnO2 material, conductive agent, and binder in a mass ratio of 7g:2g:1g, and an appropriate amount of N-methylpyrrolidone (1mL) was added and stirred. After thorough stirring, the mixture was coated onto carbon cloth and then dried at 80℃. After complete drying, it was cut into pieces of the same size as the zinc sheet, 14mm × 14mm.

[0069] The 0.08g AC-MnO2 material loaded on carbon cloth obtained in this embodiment was used as the positive electrode of an aqueous zinc-ion battery.

[0070] The properties of the materials prepared in this invention are tested as follows: Phase analysis: The results are as follows Figure 1 As shown, Figure 1 (Above) is the XRD diffraction pattern of the AC-free MnO2 material prepared in Example 1. In the figure, JCPDS PDF: 44-0141 represents α-MnO2. Figure 1 (Below) is the XRD diffraction pattern of the AC-MnO2 material prepared in Example 4. In the figure, JCPDS PDF: 24-0735 represents β-MnO2. This indicates that the crystal form of manganese dioxide changed after the addition of AC.

[0071] like Figure 2 As shown, Figure 2 (Above) is a SEM image of the AC-free MnO2 material prepared in Example 1. It can be seen from the image that its morphology is nanowires. Figure 2 (Below) is a SEM image of the AC-MnO2 material prepared in Example 4. It can be seen from the image that its morphology has been transformed into nanorods.

[0072] Electrochemical performance testing: Electrochemical tests were performed on the materials obtained in Examples 1-6. All electrochemical performance test results were obtained using the Xinwei Battery Test Cabinet (Shenzhen Xinwei Electronics Co., Ltd., CT8002S-5V100mA-124). The voltage window for all tests was 0.2-2V. The number of performance test cycles was 10,000, and the current values ​​were set to 0.1, 0.3, 0.5, 1.0, 2.0, and 3.0A.

[0073] The button cell battery is assembled in the following order: positive electrode shell → positive electrode material → separator → electrolyte → zinc sheet → gasket → spring contact → negative electrode shell. The electrolyte used in the assembly of the button cell battery is 2 mol·L⁻¹. -1 ZnSO4 solution and 0.1 mol·L -1 The mixture of MnSO4 and the positive electrode shell, separator, zinc sheet, gasket, spring sheet and negative electrode shell used are all commonly used materials for assembling batteries and are available commercially.

[0074] After testing, the best-performing AC-MnO2 was the 0.05 AC-MnO2 prepared in Example 4, meaning that the AC-MnO2 prepared with an addition amount of 0.05 g had the best performance.

[0075] The results are as follows Figure 3 At a current density of 0.1 A g -1 The specific capacity-voltage plot shows that the AC-MnO2 prepared in Example 4 has the best performance, while the MnO2 without added AC has the worst performance. Furthermore, rate performance tests were conducted on Examples 4 and 1, and the results are as follows... Figure 4As shown, the rate performance of AC-MnO2 in Example 4 was also superior to that of α-MnO2 in Example 1 without added AC. Finally, Figure 5 Cyclic tests also showed that the AC-MnO2 in Example 4 had better cycle stability than the α-MnO2 in Example 1 without added AC. After 200 cycles, the battery prepared with AC-MnO2 as the positive electrode in Example 4 still had 96% of its initial capacity, while the battery prepared with α-MnO2 as the positive electrode in Example 1 only had 51% of its initial capacity retention after 200 cycles.

[0076] The activated carbon used in this invention is a high-capacity, multi-porous activated carbon that provides a good adsorption environment for the precursors KMnO4 and MnCl2·4H2O. Meanwhile, ordinary activated carbon was also tested and its morphology was scanned, revealing that it did not alter the crystal structure or improve performance. Therefore, the selection of activated carbon involved a creative screening process.

[0077] The above embodiments describe the basic principles, main features, and advantages of the present invention. The present invention is not limited to the details of the above embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the invention. The embodiments described are exemplary and not restrictive.

Claims

1. A method for preparing high-capacity manganese dioxide nanorods by confined growth in porous activated carbon, characterized in that, The method includes: KMnO4 and AC were thoroughly mixed in deionized water and ultrasonically dispersed to obtain a mixture of KMnO4 and AC. Dissolve MnCl2·4H2O completely in deionized water, and add sulfuric acid solution dropwise while stirring to obtain an acidified MnCl2·4H2O solution. A mixture of KMnO4 and AC was added to an acidified MnCl2·4H2O solution. After stirring and mixing, the mixture was allowed to react completely and then cooled to room temperature. The precipitate was collected, washed, and dried to obtain high-capacity manganese dioxide nanorods grown in a confined environment on porous activated carbon.

2. The preparation method according to claim 2, characterized in that, The amounts of KMnO4, AC, and deionized water used are 8 mmol: 0.01 g - 0.08 g: 35 mL.

3. The preparation method according to claim 2, characterized in that, The thorough mixing is achieved by magnetic stirring; the ultrasonic power is 50W and the time is 30min.

4. The preparation method according to claim 2, characterized in that, The ratio of MnCl2·4H2O to deionized water is 8 mmol:35 mL; the concentration of the sulfuric acid solution is 0.5 mol / L, and the amount of sulfuric acid solution added is 1 mL.

5. The preparation method according to claim 2, characterized in that, The mixture of KMnO4 and AC was added to an acidified MnCl2·4H2O solution and reacted at 180°C for 6 hours.

6. High-capacity manganese dioxide nanorods prepared by the method according to any one of claims 1-6.

7. The application of porous activated carbon with confined growth of high-capacity manganese dioxide nanorods prepared by the method of any one of claims 1-6, or the porous activated carbon with confined growth of high-capacity manganese dioxide nanorods as described in claim 7, in the cathode material of aqueous zinc-ion batteries.

8. The application according to claim 7, characterized in that, The method for preparing the cathode material includes: Weigh out the porous activated carbon confinement growth of high-capacity manganese dioxide nanorods, conductive agent and binder as described in claim 7, then add N-methylpyrrolidone and stir. Spread the stirred mixture evenly on the carbon cloth, then put it in an oven to dry, take it out and cut it.

9. An aqueous zinc-ion battery, characterized in that, The aqueous zinc-ion battery uses the high-capacity manganese dioxide nanorod cathode material grown in the confined space of porous activated carbon as described in claim 7 as the cathode.

10. The battery according to claim 9, characterized in that, The aqueous zinc-ion battery uses a zinc sheet as the negative electrode and a mixture of ZnSO4 and MnSO4 as the electrolyte, wherein the concentration of ZnSO4 is 2 mol·L⁻¹. -1 The concentration of MnSO4 is 0.1 mol·L⁻¹ -1 .

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