Preparation and application of a composite cathode material and aqueous zinc-ion battery

Abstract

This invention discloses the preparation and application of a composite cathode material and its application in an aqueous zinc-ion battery. The preparation method of the composite cathode material is as follows: a manganese source, a nickel source, a vanadium source, and a surfactant are dissolved in a first solvent to obtain a first solution; the pH of the first solution is adjusted to acidic, and the reaction is heated; the reaction product is centrifuged to collect the precipitate, which is then washed and dried to obtain an intermediate product powder; the intermediate product powder, 2-methylimidazole, and a zinc source are dispersed in a second solvent to obtain a second solution; the second solution is stirred at room temperature to react; the reaction product is centrifuged to collect the precipitate, which is then washed and dried to obtain the composite cathode material. The composite cathode material prepared by this method is suitable for high-performance aqueous zinc-ion batteries. When the Ni-doped composite cathode material of this invention is applied to an aqueous zinc-ion battery, it exhibits high specific capacity, high stability, and excellent electrochemical performance, showing broad application prospects and industrialization value.

Description

Technical Field

[0001] This invention relates to a battery cathode material and its preparation method, and more particularly to the preparation and application of a Ni-doped MVO composite cathode material coated with a metal-organic framework material and an aqueous zinc-ion battery. Background Technology

[0002] Aqueous zinc-ion batteries (AZIBs) have attracted considerable attention due to their high safety, low cost, and moderate ionic radius. AZIBs, using neutral or near-neutral electrolytes as their primary raw material, are widely regarded as one of the most promising alternatives to lithium-ion batteries due to their pollution-free nature, abundant zinc resources, and safety and reliability. However, AZIBs are still some distance from practical application due to their relatively low energy density and cycle stability.

[0003] The energy density of aqueous zinc-ion batteries (AZIBs) depends primarily on two factors: capacity and operating voltage. While aqueous AZIBs with zinc anodes possess high theoretical capacities (up to 820 mAh / g), their actual capacity is often limited by the cathode material. Regarding operating voltage, although some materials (such as Prussian blue analogues) can provide high operating voltages, they suffer from severe capacity degradation, low capacity, or low rate performance. Therefore, exploring suitable cathode materials that simultaneously offer good storage capacity, cycle stability, and high operating voltage is crucial. Manganese-based oxides with high operating voltages and vanadium-based materials with excellent cycle stability and high capacity are attractive options for AZIBs. Among these, the use of manganese vanadate (MVO) as a cathode material for high-energy-density AZIBs has attracted significant attention.

[0004] However, conventional manganese vanadate cathodes are prone to structural collapse and capacity decay during cycling, mainly due to Mn dissolution, slow ion diffusion kinetics, and interfacial side reactions. In AZIBs, high charge carriers and Zn... 2+ The large ionic radius of MVO leads to strong electrostatic interactions with the crystal lattice of the compound, resulting in slow kinetics and structural collapse. Simultaneously, the poor conductivity of MVO causes capacity loss, increased polarization, and poor electrochemical performance during discharge and charge. Therefore, improving the electrochemical performance of MVO cathode materials has become an urgent technical problem to be solved. Summary of the Invention

[0005] Objectives of this invention: The objective of this invention is to provide a method for preparing composite cathode materials, solving the problem of how to prepare active cathode materials for aqueous zinc-ion batteries. A second objective is to propose the application of composite cathode materials in the preparation of battery cathodes, solving the problem of how to prepare battery cathodes. A third objective is to propose an aqueous zinc-ion battery that combines high specific capacity, high stability, and excellent electrochemical performance.

[0006] Technical solution: The present invention provides a method for preparing a composite cathode material, comprising the following steps: (1) The manganese source, nickel source, vanadium source and surfactant are mixed and dissolved in the first solvent to obtain the first solution; (2) After adjusting the pH of the first solution to acidic, heat the reaction, centrifuge the reaction product to collect the precipitate, wash the precipitate, dry it to obtain the intermediate product powder; (3) Disperse the intermediate product powder, 2-methylimidazole and zinc source into the second solvent to obtain the second solution. Stir the second solution at room temperature to react. Centrifuge the reaction product to collect the precipitate. Wash the precipitate and dry it to obtain the composite cathode material.

[0007] This invention introduces transition metal doping (such as Ni) into MVO. 2+ The construction of metal-organic framework materials and the doped MVO structure can effectively improve electron / ion transport channels, enhance electronic conductivity, adjust lattice structure, reduce diffusion resistance and inhibit electrolyte corrosion, thereby achieving high stability, high capacity and high rate output.

[0008] Preferably, in step (1), the manganese source includes at least one of manganese chloride, manganese acetate, manganese nitrate, manganese sulfate, and manganese carbonate; the nickel source includes at least one of nickel chloride, nickel acetate, nickel nitrate, nickel sulfate, and nickel carbonate; and the vanadium source includes at least one of ammonium metavanadate, vanadium pentoxide, and vanadium chloride.

[0009] Preferably, in step (1), the surfactant includes at least one of sodium dodecyl sulfate, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, and hexadecyltrimethylammonium chloride; the first solvent includes at least one of water, ethanol, propanol, and ethylene glycol.

[0010] Preferably, in step (1), the molar ratio of the manganese source, nickel source, vanadium source and surfactant is 1-2:0.01-0.1:1-3:0.01-0.1; and the concentration of manganese in the first solution is 0.01-5.0 mol / L.

[0011] Preferably, in step (2), the pH adjustment method is to adjust the pH value of the first solution to 1-7, preferably pH 3-6, using at least one of acetic acid, nitric acid, hydrochloric acid, and sulfuric acid; the heating reaction condition is to heat the first solution to 80-300℃ for 4-24 h; the precipitation washing method is to wash the precipitate using at least one of water and ethanol.

[0012] Preferably, in step (3), the zinc source includes at least one of zinc chloride, zinc acetate, zinc nitrate, zinc sulfate, and zinc carbonate, and the second solvent includes at least one of water, ethanol, and methanol; the precipitation cleaning uses at least one of water and ethanol as the cleaning agent.

[0013] Preferably, in step (3), the molar ratio of the intermediate product powder, 2-methylimidazole, and zinc source is 0.01-10.0:0.002-1.0:0.001-0.05, and the intermediate product is Mn. 1-x Ni x V2O6, 0.01 <x<0.15。

[0014] Preferably, in step (3), the stirring reaction is carried out by stirring at 100-2000 rpm for 0.5-12 hours and then allowing the mixture to stand for 0.5-24 hours. The second aspect of this invention discloses the application of the above-mentioned composite cathode material in the preparation of battery cathodes.

[0015] Specifically, the method for preparing the battery positive electrode sheet using the above-mentioned composite positive electrode material is as follows: Using the above-mentioned composite cathode material as the active material, conductive carbon black as the conductive agent, and PVDF as the binder, a uniform slurry was prepared by dissolving it in NMP at a ratio of 7:2:1 and grinding it. The slurry was then uniformly coated onto carbon paper, vacuum dried at 50-80℃ for 12-24 h, and then pressed into a sheet to obtain the battery cathode.

[0016] The third aspect of this invention discloses an aqueous zinc-ion battery, comprising a positive electrode, a separator, and a negative electrode immersed in an electrolyte, wherein the positive electrode contains the aforementioned composite positive electrode material.

[0017] In some embodiments, the positive electrode has a diameter of 12 mm, and a high-purity zinc foil (12 mm diameter disc) with a thickness of 20-50 micrometers is used as the negative electrode. The electrolyte is a mixed solution of ZnSO4 and MnSO4, with a ZnSO4 concentration of 2-3.5 mol / L and a MnSO4 concentration of 0.05-0.5 mol / L. A 14 mm diameter GF / A glass fiber membrane is used for better electrolyte wetting. The positive electrode shell, positive electrode sheet, electrolyte-wetting membrane, zinc negative electrode, gasket, and negative electrode shell are sequentially arranged, pressurized, and assembled into a 2016 type button-type aqueous zinc-ion battery.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: This invention significantly improves the problems of structural instability, low conductivity, and severe Mn dissolution in traditional MnV2O6 cathode materials during cycling by employing a synergistic strategy of Ni ion doping and ZIF-8 metal-organic framework coating. 2+ Replace part of Mn 2+ Entering the MnV₂O₆ lattice, the local electronic structure can be effectively modulated, enhancing the stability of the Mn–O bond, thereby significantly improving the lattice integrity and structure retention during cycling; simultaneously, the doped Ni… 2+It can reduce the electron transport barrier and improve the intrinsic conductivity of the material. The outer ZIF-8 coating layer, with its porous framework and good chemical stability, not only provides a continuous channel for the rapid diffusion of Zn² + ions, but also forms a stable interface between the electrode and the electrolyte, inhibits the dissolution of Mn and the occurrence of side reactions, and enables the electrode to maintain high reversibility and structural integrity during long-term cycling.

[0019] In addition, the synthesis process adopted in this invention is simple, mild in conditions, and highly controllable. The Ni doping ratio and the ZIF-8 coating thickness can be precisely regulated by adjusting the reactant concentration and reaction time, and it has good repeatability and the potential for large-scale production. The Ni-doped Mn 1-x Ni x When the V2O6@ZIF-8 (0.01 < x < 0.15) composite cathode material is applied to aqueous zinc-ion batteries, it has high specific capacity, high stability, and excellent electrochemical performance, and has broad application prospects and industrialization value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the X-ray diffraction (XRD) pattern of the pure sample and the doped samples; Figure 2 is the SEM image of the Mn 0.95 Ni 0.05 V2O6@ZIF-8 composite material prepared in Example 1; Figure 3 is the rate cycling performance graph of aqueous zinc-ion batteries prepared with different cathode active materials at different current densities; Figure 4 is the cycle stability performance graph of aqueous zinc-ion batteries prepared with different cathode active materials. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0022] Example 1: A preparation method of a Mn 0.95 Ni 0.05 V2O6@ZIF-8 composite cathode material is as follows: (1) Accurately weigh 0.188 g of manganese chloride, 0.234 g of ammonium metavanadate, 0.0065 g of nickel chloride, and 0.048 g of sodium dodecyl sulfate, and successively add them to 40 mL of deionized water. Magnetically stir at 500 rpm for 0.5 h to fully dissolve the solutes therein, obtaining a uniform first solution. Drop acetic acid into the first solution to adjust the pH value to 4.

[0023] (2) The first solution was transferred to a 75 mL polytetrafluoroethylene-lined reactor and placed in a microwave hydrothermal synthesizer at 180 °C for 18 h of continuous reaction. After the reaction was completed, the precipitate was collected by centrifugation. The precipitate was washed alternately by centrifugation with deionized water and ethanol. The washed precipitate was then vacuum dried at 60 °C for 12 h to obtain the intermediate product Mn. 0.95 Ni 0.05 V2O6 powder.

[0024] (3) Accurately weigh 0.1g Mn 0.95 Ni 0.05 V₂O₆ powder, 0.44 g zinc chloride, and 0.66 g 2-methylimidazole were added sequentially to 40 mL of deionized water. The mixture was magnetically stirred at 500 rpm for 1 h at room temperature, followed by standing for 0.5 h to obtain the reaction product. The product was centrifuged to collect the precipitate, which was then washed with deionized water and ethanol alternately by centrifugation, and finally dried under vacuum at 60 °C for 10 h to obtain Mn. 0.95 Ni 0.05 V2O6@ZIF-8 composite cathode material powder.

[0025] The Mn obtained by the above method 0.95 Ni 0.05 X-ray diffraction tests were performed on V2O6@ZIF-8 composite cathode material powder and undoped pure MnV2O6 material. The results are as follows: Figure 1 As shown. By Figure 1 It can be seen that Mn 0.95 Ni 0.05 V2O6@ZIF-8 exhibited characteristic peaks of MnV2O6, corresponding one-to-one with the standard card PDF#97-004-0850. Meanwhile, Mn... 0.95 Ni 0.05 V2O6@ZIF-8 also exhibited most of the characteristic peaks of ZIF-8, similar to pure ZIF-8 diffraction. Figure 1 There is a one-to-one correspondence, and no new diffraction peaks appear. This proves that the present invention has successfully achieved Mn 0.95 Ni 0.05 Composite of V2O6 and ZIF-8.

[0026] The Mn obtained by the above method 0.95 Ni 0.05 Microstructure (SEM) of V2O6@ZIF-8 material was measured, and the results are as follows: Figure 2 As shown, by Figure 2 It can be seen that the main body of the material has a nanosphere structure, the nanospheres are uniformly distributed, and the particle size is 5-10 nm. Figure 2 This indicates that the method of the present invention can achieve stable composite formation of Ni-doped MnV2O6 and ZIF-8, and obtain a homogeneous composite material with a complete structure.

[0027] Example 2: A Mn 0.95 Ni 0.05 The preparation method of V2O6@ZIF-8 composite cathode material is as follows: (1) Accurately weigh 0.233 g manganese acetate, 0.234 g ammonium metavanadate, 0.0088 g nickel acetate and 0.052 g polyvinylpyrrolidone, and add them to 40 mL of deionized water in sequence. Stir magnetically at 500 rpm for 0.5 h to obtain the first solution. Add nitric acid dropwise to adjust the pH value to 4.

[0028] (2) The first solution was transferred to a 75 mL polytetrafluoroethylene-lined reactor and placed in a microwave hydrothermal synthesizer at 190 °C for 18 h of continuous reaction. The reaction product was centrifuged to collect the precipitate, which was then washed with deionized water and ethanol by alternating centrifugation. The precipitate was then vacuum dried at 60 °C for 12 h to obtain Mn. 0.95 Ni 0.05 V2O6 powder.

[0029] (3) Accurately weigh 0.1g Mn 0.95 Ni 0.05 V₂O₆ powder, 0.367 g zinc acetate, and 0.66 g 2-methylimidazole were added sequentially to 40 mL of deionized water. The mixture was magnetically stirred at 500 rpm for 0.5 h at room temperature, followed by standing for 12 h. The resulting product was centrifuged to collect the precipitate, which was then washed with deionized water and ethanol alternately by centrifugation. The precipitate was then vacuum dried at 60 °C for 10 h to obtain Mn. 0.95 Ni 0.05 V2O6@ZIF-8 composite powder.

[0030] Example 3: A Mn 0.95 Ni 0.05 The preparation method of V2O6@ZIF-8 composite cathode material is as follows: (1) Accurately weigh 0.251 g manganese nitrate, 0.234 g ammonium metavanadate, 0.0091 g nickel nitrate, and 0.052 g polyethylene glycol 20000, and add them sequentially to 40 mL of deionized water. Stir magnetically at 600 rpm for 0.5 h to fully dissolve the solutes and obtain the first solution. Add hydrochloric acid dropwise to adjust the pH value to 4.

[0031] (2) The first solution was transferred to a 75 mL polytetrafluoroethylene-lined reactor and placed in a microwave hydrothermal synthesizer at 200 °C for continuous reaction for 20 h. The reaction product was centrifuged to collect the precipitate, which was washed with deionized water and ethanol alternately by centrifugation and then dried under vacuum at 60 °C for 12 h to obtain Mn. 0.95 Ni0.05 V2O6 powder.

[0032] (3) Accurately weigh 0.1 g Mn 0.95 Ni 0.05 V₂O₆ powder, 0.379 g zinc nitrate, and 0.66 g 2-methylimidazole were added sequentially to 40 mL of deionized water. The mixture was magnetically stirred at 100 rpm for 12 h at room temperature, followed by standing for 24 h. The resulting product was centrifuged to collect the precipitate, which was then washed with deionized water and ethanol alternately by centrifugation. The precipitate was then vacuum dried at 60 °C for 10 h to obtain Mn. 0.95 Ni 0.05 V2O6@ZIF-8 composite powder.

[0033] Example 4: A Mn 0.95 Ni 0.05 The preparation method of V2O6@ZIF-8 composite cathode material is as follows: (1) Accurately weigh 0.151 g manganese sulfate, 0.364 g vanadium pentoxide, 0.0077 g nickel sulfate and 0.058 g polyvinyl alcohol, and add them to 40 mL of deionized water. Stir magnetically at 700 rpm for 0.5 h to fully dissolve the solutes and obtain the first solution. Add hydrochloric acid dropwise to adjust the pH value to 3.

[0034] (2) The first solution was transferred to a 75 mL polytetrafluoroethylene-lined reactor and placed in a microwave hydrothermal synthesizer at 300 °C for 20 h of continuous reaction. The reaction product was centrifuged to collect the precipitate, which was washed with deionized water and ethanol by alternating centrifugation and then dried under vacuum at 60 °C for 12 h to obtain Mn. 0.95 Ni 0.05 V2O6 powder.

[0035] (3) Accurately weigh 0.1 g Mn 0.95 Ni 0.05 V₂O₆ powder, 0.323 g zinc sulfate, and 0.66 g 2-methylimidazole were added sequentially to 40 mL of deionized water. The mixture was magnetically stirred at 2000 rpm for 0.5 h at room temperature, followed by standing for 1 h. The resulting product was centrifuged to collect the precipitate, which was then washed with deionized water and ethanol alternately by centrifugation. The precipitate was then vacuum dried at 60 °C for 10 h to obtain Mn. 0.95 Ni 0.05 V2O6@ZIF-8 composite powder.

[0036] Example 5: A Mn 0.95 Ni 0.05 The preparation method of V2O6@ZIF-8 composite cathode material is as follows: (1) Accurately weigh 0.115 g manganese carbonate, 0.315 g vanadium chloride, 0.0063 g nickel carbonate, and 0.058 g cetyltrimethylammonium chloride, and add them sequentially to 40 mL of deionized water. Stir magnetically at 500 rpm for 0.5 h to fully dissolve the solutes and obtain the first solution. Add acetic acid dropwise to adjust the pH to 5.

[0037] (2) The first solution was transferred to a 75 mL polytetrafluoroethylene-lined reactor and placed in a microwave hydrothermal synthesizer at 80 °C for continuous reaction for 24 h. The reaction product was centrifuged to collect the precipitate, which was washed with deionized water and ethanol alternately by centrifugation and then dried under vacuum at 60 °C for 12 h to obtain Mn. 0.95 Ni 0.05 V2O6 powder.

[0038] (3) Accurately weigh 0.1g Mn 0.95 Ni 0.05 V₂O₆ powder, 0.251 g zinc carbonate, and 0.66 g 2-methylimidazole were added sequentially to 40 mL of deionized water. The mixture was magnetically stirred at 1000 rpm for 1 h at room temperature, followed by standing for 12 h. The resulting product was centrifuged to collect the precipitate, which was then washed with deionized water and ethanol alternately by centrifugation. The precipitate was then vacuum dried at 60 °C for 10 h to obtain Mn. 0.95 Ni 0.05 V2O6@ZIF-8 composite powder.

[0039] Example 6: A Mn 0.9 Ni 0.1 The preparation method of V2O6@ZIF-8 composite material includes the following steps: (1) Accurately weigh 0.178 g manganese chloride, 0.234 g ammonium metavanadate, 0.013 g nickel chloride, and 0.047 g sodium dodecyl sulfate, and add them sequentially to 40 mL of deionized water. Stir magnetically at 500 rpm for 0.5 h to fully dissolve the solutes and obtain the first solution. Add acetic acid dropwise to adjust the pH to 4.

[0040] (2) The first solution was transferred to a 75 mL polytetrafluoroethylene-lined reactor and placed in a microwave hydrothermal synthesizer at 180 °C for 18 h of continuous reaction. The reaction product was centrifuged to collect the precipitate, which was washed with deionized water and ethanol by alternating centrifugation and then dried under vacuum at 60 °C for 12 h to obtain Mn. 0.9 Ni 0.1 V2O6 powder.

[0041] (3) Accurately weigh 0.1 g Mn 0.9 Ni 0.1V₂O₆ powder, 0.44 g zinc chloride, and 0.66 g 2-methylimidazole were added sequentially to 40 mL of deionized water. The mixture was magnetically stirred at 500 rpm for 1 h at room temperature, followed by standing for 15 h. The resulting product was centrifuged to collect the precipitate, which was then washed with deionized water and ethanol alternately by centrifugation. The precipitate was then vacuum dried at 60 °C for 10 h to obtain Mn. 0.9 Ni 0.1 V2O6@ZIF-8 composite powder.

[0042] Example 7: Everything else is the same as in Example 1, except that: In step (3), weigh 0.1 g of Mn 0.95 Ni 0.05 V₂O₆ powder, 0.88 g zinc chloride, and 1.32 g 2-methylimidazole were reacted to finally obtain ZIF-8 thick-coated Mn. 0.95 Ni 0.05 V2O6@2ZIF-8 composite powder.

[0043] Comparative Example 1: Everything else is the same as in Example 1, except that: In step (1), nickel chloride is not added, and step (3) is not performed.

[0044] Undoped MnV2O6 material was finally obtained.

[0045] Comparative Example 2: Everything else is the same as in Example 1, except that: Step (3) is skipped; only the Mn obtained in step (2) is processed. 0.95 Ni 0.05 V2O6 powder was used as the final product for subsequent testing.

[0046] Comparative Example 3: Everything else is the same as in Example 1, except that: Nickel chloride is not added in step (1).

[0047] Comparative Example 4: Everything else is the same as in Example 1, except that: In step (3), replace 0.44 g zinc chloride with 0.42 g cobalt chloride, stir for 10 min and let stand for 24 h.

[0048] Comparative Example 5: Everything else is the same as in Example 1, except that: Ammonium metavanadate is not added in step (1).

[0049] Comparative Example 6: Everything else is the same as in Example 1, except that: In step (1), nickel chloride is replaced with cobalt chloride.

[0050] Comparative Example 7: Everything else is the same as in Example 1, except that: In step (1), nickel chloride is replaced with ferric chloride.

[0051] Comparative Example 8: Everything else is the same as in Example 1, except that: In step (1), nickel chloride is replaced with zinc chloride.

[0052] Comparative Example 9: Composite cathode material was prepared according to the following method: (1) Accurately weigh 0.188 g manganese chloride, 0.234 g ammonium metavanadate and 0.048 g sodium dodecyl sulfate, and add them to 40 mL of deionized water in sequence. Stir magnetically at 500 rpm for 0.5 h to fully dissolve the solutes and obtain a homogeneous first solution. Add acetic acid dropwise to the first solution to adjust the pH value to 4.

[0053] (2) The first solution was transferred to a 75 mL polytetrafluoroethylene-lined reactor and placed in a microwave hydrothermal synthesizer at 180 °C for 18 h of continuous reaction. After the reaction was completed, the precipitate was collected by centrifugation. The precipitate was washed by alternating centrifugation with deionized water and ethanol. The washed precipitate was then vacuum dried at 60 °C for 12 h to obtain MnV2O6 powder.

[0054] (3) Accurately weigh 0.1 g MnV2O6 powder, 0.44 g zinc chloride, 0.0065 g nickel chloride, and 0.66 g 2-methylimidazole, and add them sequentially to 40 mL of deionized water. Stir magnetically at 500 rpm for 1 h at room temperature, and let stand for 0.5 h to obtain the reaction product. Centrifuge the reaction product to obtain the precipitate. Wash the precipitate with deionized water and ethanol by alternating centrifugation, and then vacuum dry at 60 °C for 10 h to obtain the composite cathode material powder sample.

[0055] The positive electrode material samples obtained in Examples 1-7 and Comparative Examples 1-9 were respectively made into positive electrode sheets. The positive electrode material sample, conductive carbon black and PVDF were dissolved in NMP in a ratio of 7:2:1 and ground to obtain a uniform slurry. The slurry was uniformly coated on carbon paper, vacuum dried at 65°C for 18 h and then pressed into sheets. The sheets were cut into 12 mm diameter discs as positive electrode sheets. 35 μm thick high-purity zinc foil (12 mm diameter discs) was used as the negative electrode sheet. The electrolyte was a mixed solution of ZnSO4 and MnSO4, with a ZnSO4 concentration of 2.5 mol / L and a MnSO4 concentration of 0.25 mol / L. The separator was a 14 mm diameter GF / A glass fiber separator to better wet the electrolyte. The positive electrode shell, positive electrode sheet, electrolyte-soaked separator, zinc negative electrode sheet, gasket, and negative electrode shell are arranged in sequence, pressurized and sealed to assemble a 2016-type button-type aqueous zinc-ion battery, and then placed in the Blue Electric test system to test the battery performance.

[0056] The assembled aqueous zinc-ion battery was subjected to charge-discharge tests at different rates, and the results are as follows: Figure 3 As shown, the Mn prepared in Example 1 0.95 Ni 0.05 When used as a cathode material in an aqueous zinc-ion battery, the V2O6@ZIF-8 composite material achieved a specific capacity of 451.3 mAh / g during the first discharge at 100 mA / g, and also exhibited a specific capacity of approximately 347.2 mAh / g under a high current of 5.0 A / g. In contrast, the MnV2O6 material prepared in Comparative Example 1 showed a discharge specific capacity of approximately 201.3 mAh / g at 100 mA / g and approximately 57.2 mAh / g at 5.0 A / g. It can be seen that under the same testing conditions, the performance of Comparative Example 1 is significantly lower than that of Example 1. The MnV2O6 material prepared in Comparative Example 2... 0.95 Ni 0.05 When used as an aqueous zinc-ion cathode material, the V2O6 composite material achieved a specific capacity of 379.5 mAh / g during the first discharge at 100 mA / g, and also exhibited a specific capacity of approximately 290.8 mAh / g at a high current of 5.0 A / g. Although the rate performance of the composite material prepared in Comparative Example 2 was not as good as that of the composite material prepared in Example 1, it was still a significant improvement over the undoped MnV2O6 material prepared in Comparative Example 1. The thick-coated MnV2O6 material prepared in Example 7... 0.95 Ni 0.05 When V2O6@2ZIF-8 composite material is used as an aqueous zinc ion cathode material, it achieves a specific capacity of 350.7 mAh / g during the first discharge at 100 mA / g, and can also release a specific capacity of about 235.5 mAh / g at a high current of 5.0 A / g.

[0057] Different aqueous zinc-ion battery cathode materials were tested for cycle stability at 5.0 A / g, and the results are as follows: Figure 4 As shown, by Figure 4 As can be seen, after 1000 long cycles at a high current of 5.0 A / g, the Mn prepared in Example 1 showed [significant improvement]. 0.95 Ni 0.05 The discharge specific capacity of the V2O6@ZIF-8 composite material increased from a peak of 350 mAh / g to 369 mAh / g, with a capacity retention of approximately 105.4%. The Mn prepared in Comparative Example 2... 0.95 Ni 0.05 The discharge specific capacity of the V2O6@2ZIF-8 composite material decreased from a peak of 290 mAh / g to 260 mAh / g, with a capacity retention of approximately 89.6%. In contrast, the MnV2O6 material prepared in Comparative Example 1 exhibited an initial discharge specific capacity of 91 mAh / g under the same conditions, which decreased to 52 mAh / g after 700 cycles, with a capacity retention of approximately 57.1%. It is evident that Example 1 demonstrates significantly higher initial and final specific capacities than Comparative Example 1, and the cycling curve of Example 1 is smoother than that of Comparative Example 1, indicating stronger material structural stability during cycling. Meanwhile, the MnV2O6 material prepared in Comparative Example 2... 0.95 Ni 0.05 The discharge specific capacity of the V2O6 composite material was higher than that of the comparative example 1 after 1000 cycles, indicating that nickel doping can improve the electrochemical performance of MnV2O6 material.

[0058] comprehensive Figure 3 and Figure 4 The test results are as follows: The overall electrical performance of Example 7 is significantly worse than that of Comparative Example 2, indicating that excessive ZIF-8 coating will lead to a significant decrease in the electrical performance of the cathode material, making it difficult to synergistically improve the electrical performance of Ni-doped MnV2O6 material.

[0059] In Comparative Example 3, when ZIF-8 was coated with undoped MnV2O6 material, the overall electrical properties of the composite material could not be improved, indicating that the improvement of the electrical properties of the composite material also depends on the nickel doping of MnV2O6 material.

[0060] In Comparative Example 4, when Mn is coated with ZIF-67... 0.95 Ni 0.05 When using V2O6, the overall electrical properties of the composite material are lower than those of Comparative Example 2, indicating that the coating of Co-based organometallic framework materials can actually inhibit the electrical properties of Ni-doped MnV2O6 materials and have a negative impact on the overall performance of the composite material.

[0061] In Comparative Example 5, the lack of V element resulted in a significantly lower overall electrical performance of the composite material compared to Comparative Example 1. The improvement in electrical performance depended on the nickel-doped MVO material. When only nickel and manganese oxides were used as active materials, the electrical performance was poor.

[0062] In Comparative Examples 6-8, the MnV2O6 material was doped with other metal elements such as Co, Fe, and Zn. The overall electrical performance of the composite material was significantly reduced, which was similar to the test results of Comparative Example 1. This indicates that the excellent electrical performance of the composite material depends on the doping of specific transition metal elements, and the doping of other metal elements cannot improve the overall electrical performance of the composite material.

[0063] In Comparative Example 9, nickel doping was performed simultaneously with ZIF-8 coating of MnV₂O₆ material, without pre-doping the MnV₂O₆ material with nickel. This also resulted in a significant decrease in the overall electrochemical performance of the composite material. The timing of nickel doping also has a crucial impact on the overall electrochemical performance of the composite material. Therefore, to obtain excellent electrochemical performance, Ni-doped MnV₂O₆ material must be prepared beforehand, followed by ZIF-8 coating.

[0064] from Figure 3 and Figure 4 The results show that the overall electrical performance improvement of the composite cathode material in this invention depends on the nickel-doped MnV2O6 material and the coating of the material by ZIF-8. The two are interdependent and indispensable. This invention involves multiple optimizations during the preparation process to produce a composite material with uniform structure, regular morphology, and high purity. When the material prepared by this method is used as the positive electrode material in an aqueous zinc-ion battery, it exhibits high rate performance and stable cycle performance. This invention is based on MnV₂O₆, addressing its poor electronic conductivity and the limitations of Zn... 2+ To address issues such as diffusion limitation and insufficient cycle stability, a synergistic optimization strategy combining Ni doping and ZIF-8 coating is proposed. This strategy utilizes Ni... 2+ Partially replaces Mn 2+ This design effectively modulates the crystal structure, enhances electronic conductivity, and stabilizes the framework to suppress Mn dissolution. Simultaneously, the outer ZIF-8 porous coating not only provides a rapid ion migration channel but also buffers volume changes and reduces side reactions, thereby significantly improving cycle stability and rate performance. This design achieves multi-dimensional synergy between structural stability, ion diffusion rate, and interfacial reactivity, providing a new approach for the construction of high-performance aqueous zinc-ion battery cathode materials.

Claims

1. A method for preparing a composite cathode material, characterized in that, Includes the following steps: (1) The manganese source, nickel source, vanadium source and surfactant are mixed and dissolved in the first solvent to obtain the first solution; (2) After adjusting the pH of the first solution to acidic, heat the reaction, centrifuge the reaction product to collect the precipitate, wash the precipitate, dry it to obtain the intermediate product powder; (3) Disperse the intermediate product powder, 2-methylimidazole and zinc source into the second solvent to obtain the second solution. Stir the second solution at room temperature to react. Centrifuge the reaction product to collect the precipitate. Wash the precipitate and dry it to obtain the composite cathode material.

2. The method for preparing the composite cathode material according to claim 1, characterized in that, In step (1), the manganese source includes at least one of manganese chloride, manganese acetate, manganese nitrate, manganese sulfate, and manganese carbonate; the nickel source includes at least one of nickel chloride, nickel acetate, nickel nitrate, nickel sulfate, and nickel carbonate; and the vanadium source includes at least one of ammonium metavanadate, vanadium pentoxide, and vanadium chloride.

3. The method for preparing the composite cathode material according to claim 1, characterized in that, In step (1), the surfactant includes at least one of sodium dodecyl sulfate, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, and hexadecyltrimethylammonium chloride; the first solvent includes at least one of water, ethanol, propanol, and ethylene glycol.

4. The method for preparing the composite cathode material according to claim 1, characterized in that, In step (1), the molar ratio of the manganese source, nickel source, vanadium source and surfactant is 1-2:0.01-0.1:1-3:0.01-0.1; the concentration of manganese in the first solution is 0.01-5.0 mol / L.

5. The method for preparing the composite cathode material according to claim 1, characterized in that, In step (2), the pH adjustment method is to adjust the pH value of the first solution to 1-7 using at least one of acetic acid, nitric acid, hydrochloric acid, and sulfuric acid; the heating reaction condition is to heat the first solution to 80-300℃ and react for 4-24 h; the precipitation washing method is to wash the precipitate using at least one of water and ethanol.

6. The method for preparing the composite cathode material according to claim 1, characterized in that, In step (3), the zinc source includes at least one of zinc chloride, zinc acetate, zinc nitrate, zinc sulfate, and zinc carbonate, and the second solvent includes at least one of water, ethanol, and methanol; the precipitation cleaning uses at least one of water and ethanol as the cleaning agent.

7. The method for preparing the composite cathode material according to claim 1, characterized in that, In step (3), the molar ratio of the intermediate product powder, 2-methylimidazole, and zinc source is 0.01-10.0:0.002-1.0:0.001-0.05, and the intermediate product is Mn. 1-x Ni x V2O6, 0.01 <x<0.15。 8. The method for preparing the composite cathode material according to claim 1, characterized in that, In step (3), the reaction is carried out by stirring at 100-2000 rpm for 0.5-12 hours and then allowing the mixture to stand for 0.5-24 hours.

9. The application of the composite cathode material according to any one of claims 1-8 in the preparation of battery cathodes.

10. An aqueous zinc-ion battery, comprising a positive electrode, a separator, and a negative electrode immersed in an electrolyte, characterized in that, The positive electrode comprises the composite positive electrode material according to any one of claims 1-8.

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