Green preparation process of a water-based zinc ion battery positive electrode material

Abstract

The application relates to the technical field of aqueous zinc ion batteries, and discloses a green preparation process of a positive electrode material of an aqueous zinc ion battery. The process realizes resource utilization by recovering a manganese source from waste batteries and extracting a vanadium source from vanadium slag. The process realizes carbon-coated, pre-intercalation and nitrogen-doped synergistic optimization by adopting a green complexing agent to replace a toxic chelating agent, and by integrating in-situ doping, carbon compounding and gelation procedures under low-temperature water bath conditions, combining ultrasonic-assisted low-temperature aging and 400-420 DEG C low-temperature carbonization, so that the total energy consumption of the preparation process is significantly reduced compared with a traditional high-temperature process. Finally, the finished product is obtained through ball milling mechanical activation and centrifugal washing, so that the whole process is free of strong acid, strong alkali and toxic waste liquid, the yield is greatly increased, and the positive electrode material prepared through the process has a hierarchical porous structure, a high specific surface area and a nanoscale particle size.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion battery technology, specifically to a green preparation process for aqueous zinc-ion battery cathode materials. Background Technology

[0002] Aqueous zinc-ion batteries, due to their high safety, low cost, environmental friendliness, and high theoretical capacity, show broad application prospects in large-scale energy storage and wearable electronic devices. Cathode materials are one of the key factors determining battery performance. Currently, the most studied cathode materials include manganese-based oxides, vanadium-based oxides, and Prussian blue analogues. Among them, manganese-vanadium-based oxides have attracted much attention due to their high specific capacity and suitable operating voltage. However, existing cathode material preparation processes still have many shortcomings: First, the traditional sol-gel method often uses chelating agents such as EDTA and citric acid, some of which are toxic or poorly biodegradable, and uneven metal ion dispersion easily leads to the formation of impurity phases, affecting electrochemical performance; Second, high-temperature carbonization treatment usually requires 700~900℃, resulting in high energy consumption, uneven carbon distribution, and difficulty in controlling residual carbon content; Third, the preparation process often employs stepwise doping, coating, and pre-intercalation processes, which are lengthy, involve multiple intermediate purification steps, and generate large amounts of strong acid and alkali waste liquids, failing to meet the requirements of green chemistry; Fourth, the raw materials often use high-purity chemical reagents, resulting in high costs and failing to effectively utilize waste battery resources. Therefore, developing a green, low-temperature, short-process, and high-performance aqueous zinc-ion battery cathode material preparation process is of great practical significance. Summary of the Invention

[0003] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a green preparation process for aqueous zinc-ion battery cathode materials. This process is environmentally friendly throughout, energy-efficient at low temperatures, highly integrated and efficient, and produces products with excellent electrochemical performance. It solves the problems of uneven metal ion dispersion leading to impurities, high energy consumption and uneven carbon distribution during high-temperature carbonization, long preparation process with toxic waste liquid, and ineffective utilization of waste resources in existing processes.

[0004] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a green preparation process for aqueous zinc-ion battery cathode materials, comprising the following steps: Step 1: Raw materials and their weight parts: manganese source, vanadium source, bismuth source, green complexing agent, biomass carbon source, dopant, pre-intercalation agent, glycine and deionized water; Step 2, Green Complexing Sol: Dissolve manganese source, vanadium source and bismuth source in deionized water in sequence, stir at room temperature until completely dissolved, then add green complexing agent and glycine, continue stirring, and finally add pre-intercalating agent to adjust pH value to obtain green complexing sol; Step 3, Composite Gelization: Add dopants and biomass carbon sources sequentially to the green complex sol, and stir under normal pressure water bath conditions until the doped ions are uniformly embedded in the metal complex framework to form a composite wet gel; Step 4, Low-temperature structure control: The composite wet gel is transferred to a sealed container and aged under normal pressure water bath conditions, with intermittent ultrasonic treatment during the process. After aging, it is naturally cooled to room temperature to obtain the composite dry gel precursor. Step 5, Low-Temperature Curing: The composite dry gel precursor is placed in a tube furnace and heated to the target temperature under an inert atmosphere. In-situ carbonization is then performed at the target temperature, while the pre-intercalating agent decomposes and produces... The material is embedded between layers and then naturally cooled to room temperature to obtain crude cathode material. Step 6, Mechanical activation post-processing: Mix the crude positive electrode material with deionized water according to the set solid-liquid ratio, and then perform ball milling, centrifugal washing, vacuum drying and sieving to obtain the final aqueous zinc-ion battery positive electrode material.

[0005] Preferably, the raw materials and their weight parts in step one are as follows: 20-25 parts manganese source; 15-20 parts vanadium source; 5-8 parts bismuth source; 10-16 parts green complexing agent; 7-11 parts biomass carbon source; 1-3 parts dopant; 2-4 parts pre-intercalating agent; 0.5-1.2 parts glycine; and the remaining raw material is deionized water.

[0006] Preferably, the manganese source is selected from manganese sulfate extracted from the leachate of waste zinc-manganese batteries, and the extraction steps are as follows: S1.1 Crushing and sorting: Waste zinc-manganese batteries are mechanically crushed, magnetically separated and screened to obtain manganese-rich cathode powder, with the crushing particle size controlled between 100 and 200 mesh; S1.2 Green Reducing Leaching: The positive electrode powder is mixed with sulfuric acid solution and oxalic acid reducing agent. The sulfuric acid concentration is controlled between 1.0 and 3.0 mol / L, the liquid-solid ratio between 5:1 and 10:1, the leaching temperature between 60 and 90℃, and the leaching time between 1 and 4 hours. Restore to It dissolves, yielding a leachate containing manganese sulfate; S1.3 Post-treatment: The leachate is filtered to remove insoluble residues. The filtrate is adjusted to pH 5.0-5.5 to precipitate and remove iron and aluminum. It is then evaporated and concentrated at 90-95℃ and vacuum degree -0.09--0.095MPa to a solution density of 1.50-1.55g / cm³. It is then cooled to room temperature at a cooling rate of 6-8℃ / h to crystallize. It is then centrifuged at 4000-5000r / min. Finally, it is vacuum dried at 100-105℃ and vacuum degree -0.09--0.1MPa for 6-8h to obtain manganese sulfate crystals.

[0007] Preferably, the vanadium source is selected from either vanadium pentoxide extracted from vanadium slag or ammonium metavanadate, and the extraction steps are as follows: S2.1 Crushing and ball milling: Crush the vanadium slag to a particle size ≤0.074mm, control the ball-to-material ratio between 5:1 and 10:1, and the ball milling time between 2.5 and 3.0h; S2.2, Sodium carbonate roasting: Mix the ball-milled vanadium slag with sodium carbonate at a mass ratio of 100:15-25, control the roasting temperature between 650-700℃ and the roasting time between 1-2h, so that vanadium is converted into soluble sodium vanadate. S2.3 Water immersion: Mix the roasted clinker with water, control the liquid-solid ratio between 3:1 and 6:1, the water immersion temperature between 85 and 90°C, the water immersion time between 1 and 2 hours, and the pH value between 8 and 9, and filter to obtain a water immersion solution containing sodium vanadate. S2.4 Ammonium salt precipitation of vanadium: Add ammonium sulfate to the water leaching solution, control the amount of ammonium salt to be 1.0 to 1.5 times the theoretical amount, the pH value of vanadium precipitation to be between 8 and 9, the precipitation temperature to be between 40 and 50℃, stir the reaction for 45 to 55 minutes, and filter to obtain ammonium metavanadate precipitate. S2.5 Calcination and decomposition: Calcine ammonium metavanadate at 650-700℃ for 1-2 hours to decompose it into vanadium pentoxide; or use ammonium metavanadate directly as a vanadium source.

[0008] Preferably, the bismuth source is bismuth nitrate; the green complexing agent is selected from sodium citrate or tartaric acid; the biomass carbon source is selected from two of rice husk powder, sodium alginate or straw extract; the dopant is selected from one of cobalt acetate, cobalt acetate or nickel sulfate; and the pre-intercalating agent is selected from one of ammonium acetate, potassium acetate or ammonium oxalate.

[0009] Preferably, the preparation process of the green complexed sol in step two is as follows: S3.1 Dissolve the manganese source, vanadium source and bismuth source in deionized water in sequence, and stir at 400-500 r / min at room temperature until completely dissolved; S3.2, then add the green complexing agent and glycine, and continue stirring at 200-300 r / min for 30-60 min; S3.3 Finally, add the pre-intercalating agent and adjust the pH value to 4.5-6.0 to obtain a green complexed sol.

[0010] Preferably, the composite gelation conditions in step three are as follows: dopant and biomass carbon source are added sequentially to the green complex sol, and stirred at a speed of 100-200 r / min for 3-4 hours under normal pressure water bath conditions at 50-55℃.

[0011] Preferably, the low-temperature structure control conditions in step four are as follows: the composite wet gel is transferred to a sealed container and aged in a normal pressure water bath at 85-90°C for 6-12 hours, supplemented by intermittent ultrasonic treatment with a power of 200-400W for 15-20 minutes every 2 hours.

[0012] Preferably, the low-temperature curing conditions in step five are as follows: the composite dry gel precursor is placed in a tube furnace and cured at a concentration greater than 99.99%. Under an inert atmosphere, the temperature is increased to 400–420℃ at a rate of 3–5℃ / min, and held at this temperature for 2–3 hours for in-situ carbonization. The carbonization reaction formula for the biomass carbon source is as follows: ; In the formula, For glucose units, n represents the degree of polymerization of biomass polysaccharides.

[0013] Preferably, the mechanical activation post-treatment process in step six is ​​as follows: S4.1 Mix the crude positive electrode material with deionized water at a solid-liquid mass ratio of 1:1.5, and ball mill in a planetary ball mill at a speed of 400-500 r / min for 1-2 hours; S4.2 After ball milling, the slurry is centrifuged at 5000-6000 r / min for 10-15 min, then washed with deionized water 2-3 times, and then placed in a vacuum drying oven at 60-70℃ for 7-8 h. Finally, it is passed through a 200-400 mesh sieve to obtain the final aqueous zinc-ion battery cathode material.

[0014] Compared with existing technologies, this invention provides a green preparation process for aqueous zinc-ion battery cathode materials, which has the following beneficial effects: 1. This invention achieves high-value recycling of waste resources by sourcing manganese from leachate of waste zinc-manganese batteries and vanadium from industrial vanadium slag. It also eliminates pollution from strong acids, alkalis, and toxic waste liquids at the source by using sodium citrate / tartaric acid as a green chelating agent to replace toxic chelating agents, and by using rice husk powder, sodium alginate, and straw extract as biomass carbon sources to replace fossil-based carbon sources. The entire process is pollution-free with no secondary pollution and a yield of over 98%.

[0015] 2. This invention reduces energy consumption by more than 50% by using low-temperature in-situ carbonization at 400-420℃ instead of traditional high-temperature solid-state sintering at 700-900℃. The low-temperature conditions can effectively suppress grain growth during sintering, effectively preserve the hierarchical porous structure and high specific surface area, and simultaneously achieve synergistic modification through carbon coating, pre-intercalation, and nitrogen doping.

[0016] 3. This invention integrates in-situ doping, carbon composite and gelation into a single process, and simultaneously uses ultrasonic-assisted aging to enhance mass transfer and ball milling to mechanically activate and refine particles. This results in a short process flow and eliminates the need for intermediate separation and purification, significantly reducing equipment investment and production costs. The final grain size is refined to 2.0-3.0 μm and the carbon distribution is uniform. Attached Figure Description

[0017] Figure 1 This is a flow chart of the green preparation process of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1 A green preparation process for aqueous zinc-ion battery cathode material includes the following steps: Step 1: Raw materials and their weight parts: manganese source, vanadium source, bismuth source, green complexing agent, biomass carbon source, dopant, pre-intercalation agent, glycine and deionized water; Step 2, Green Complexing Sol: Manganese, vanadium, and bismuth sources are dissolved sequentially in deionized water and stirred at room temperature until completely dissolved. Then, a green complexing agent and glycine are added, and stirring continues to allow the metal ions to form a stable, soluble complex with the complexing agent. Finally, a pre-intercalating agent is added, and the pH value is adjusted to obtain a uniform and transparent green complexing sol. This step achieves uniform molecular-level dispersion of metal ions by replacing toxic chelating agents with green complexing agents, thus preventing the formation of impurity phases from the source. Step 3, Composite Gelization: Add dopants and biomass carbon sources sequentially to the green complex sol, and stir under normal pressure water bath conditions until the doped ions are uniformly embedded in the metal complex framework. At the same time, the biomass carbon source and the metal complex undergo cross-linking reaction to form a composite wet gel with a three-dimensional network structure. This step integrates in-situ doping, morphology control and carbon composite into a single process, shortening the process and avoiding intermediate purification steps. Step 4, Low-temperature structure control: The composite wet gel is transferred to a sealed container and aged under normal pressure water bath conditions. During the process, intermittent ultrasonic treatment is used to enhance mass transfer and promote uniform growth of crystal nuclei. After aging, the gel is naturally cooled to room temperature to obtain a composite dry gel precursor with a hierarchical porous structure. The ultrasonic-assisted external field can effectively enhance and compensate for the defects of insufficient reaction kinetics under low temperature and normal pressure, ultimately achieving grain refinement and specific surface area improvement. Step 5, Low-Temperature Curing: The composite dry gel precursor is placed in a tube furnace and slowly heated to the target temperature under an inert atmosphere. In-situ carbonization is then performed at the target temperature, transforming the biomass carbon source into a continuous conductive carbon network. Simultaneously, the pre-intercalating agent decomposes and produces... Intercalation between layers, glycine decomposes to provide nitrogen doping, and then it is naturally cooled to room temperature to obtain a crude cathode material with carbon coating, in-situ doping, and pre-intercalation synergistic optimization. Low-temperature carbonization replaces the traditional high-temperature treatment of 700-900℃, reducing energy consumption by more than 50%, and making the carbon distribution uniform and the residual carbon controllable. Step 6, Mechanical Activation Post-Processing: The crude positive electrode material is mixed with deionized water at a set solid-liquid ratio, and then ball-milled, centrifuged, washed, vacuum-dried and sieved to obtain the final aqueous zinc-ion battery positive electrode material. Ball milling mechanical activation further improves the conductivity and structural stability of the material. The entire process is free of strong acids and alkalis and toxic waste liquids, with a yield of over 98%.

[0020] Specifically, the raw materials and their weight parts in step one are as follows: 20-25 parts manganese source; 15-20 parts vanadium source; 5-8 parts bismuth source; 10-16 parts green complexing agent; 7-11 parts biomass carbon source; 1-3 parts dopant; 2-4 parts pre-intercalating agent; 0.5-1.2 parts glycine; and the remaining raw material is deionized water.

[0021] The function table of raw materials is as follows: Table 1 ; Specifically, the manganese source is manganese sulfate extracted from the leachate of waste zinc-manganese batteries, and the extraction steps are as follows: S1.1 Crushing and sorting: Waste zinc-manganese batteries are mechanically crushed, magnetically separated and screened to obtain manganese-rich cathode powder, with the crushing particle size controlled between 100 and 200 mesh; S1.2 Green Reducing Leaching: The positive electrode powder is mixed with sulfuric acid solution and oxalic acid reducing agent. The sulfuric acid concentration is controlled between 1.0 and 3.0 mol / L, the liquid-solid ratio between 5:1 and 10:1, the leaching temperature between 60 and 90℃, and the leaching time between 1 and 4 hours. Restore to It dissolves, yielding a leachate containing manganese sulfate; S1.3 Post-treatment: The leachate is filtered to remove insoluble residues. The filtrate is adjusted to pH 5.0-5.5 to precipitate and remove iron and aluminum. It is then evaporated and concentrated at 90-95℃ and vacuum degree -0.09--0.095MPa to a solution density of 1.50-1.55g / cm³. It is then slowly cooled to room temperature at a cooling rate of 6-8℃ / h to crystallize. It is then centrifuged at 4000-5000r / min. Finally, it is vacuum dried at 100-105℃ and vacuum degree -0.09--0.1MPa for 6-8h to obtain manganese sulfate crystals.

[0022] The advantages are: through the resource recycling of waste zinc-manganese batteries, green reduction leaching of oxalic acid, and gradient cooling crystallization purification process, low-cost enrichment of manganese source can be achieved, while also disposing of waste battery solid waste.

[0023] Specifically, the vanadium source is selected from either vanadium pentoxide extracted from vanadium slag or ammonium metavanadate, and the extraction steps are as follows: S2.1 Crushing and ball milling: Crush the vanadium slag to a particle size ≤0.074mm (200 mesh), control the ball-to-material ratio between 5:1 and 10:1, and the ball milling time between 2.5 and 3.0 hours; S2.2, Sodium carbonate roasting: Mix the ball-milled vanadium slag with sodium carbonate at a mass ratio of 100:15-25, control the roasting temperature between 650-700℃ and the roasting time between 1-2h, so that vanadium is converted into soluble sodium vanadate. S2.3 Water immersion: Mix the roasted clinker with water, control the liquid-solid ratio between 3:1 and 6:1, the water immersion temperature between 85 and 90°C, the water immersion time between 1 and 2 hours, and the pH value between 8 and 9, and filter to obtain a water immersion solution containing sodium vanadate. S2.4 Ammonium salt precipitation of vanadium: Add ammonium sulfate to the water leaching solution, control the amount of ammonium salt to be 1.0 to 1.5 times the theoretical amount, the pH value of vanadium precipitation to be between 8 and 9, the precipitation temperature to be between 40 and 50℃, stir the reaction for 45 to 55 minutes, and filter to obtain ammonium metavanadate precipitate. S2.5 Calcination and decomposition: Calcine ammonium metavanadate at 650-700℃ for 1-2 hours to decompose it into vanadium pentoxide; or use ammonium metavanadate directly as a vanadium source.

[0024] The advantages are: by combining low-temperature roasting of sodium carbonate, water leaching and ammonium salt precipitation of vanadium, the vanadium element in vanadium slag can be efficiently extracted and transformed. The process is highly adaptable and can flexibly produce vanadium pentoxide or ammonium metavanadate.

[0025] Specifically, the bismuth source is bismuth nitrate; the green complexing agent is selected from sodium citrate or tartaric acid; the biomass carbon source is selected from two of rice husk powder, sodium alginate, or straw extract; the dopant is selected from one of cobalt acetate, cobalt acetate, or nickel sulfate; and the pre-intercalating agent is selected from one of ammonium acetate, potassium acetate, or ammonium oxalate.

[0026] The advantages are: by selecting non-toxic or low-toxic bismuth nitrate, sodium citrate / tartaric acid, biomass carbon source, transition metal dopant and weak acid salt pre-intercalation agent, the use of heavy metals and organic toxic substances can be avoided from the source, thus reflecting the whole process green chemical design concept.

[0027] Specifically, the preparation process of the green complexed sol in step two is as follows: S3.1 Dissolve the manganese source, vanadium source and bismuth source in deionized water in sequence, and stir at 400-500 r / min at room temperature until completely dissolved; S3.2 Add the green complexing agent and glycine, and continue stirring at 200-300 r / min for 30-60 min to allow the metal ions to form a stable soluble complex with the complexing agent. S3.3 Finally, add a pre-intercalating agent and adjust the pH value to 4.5-6.0 to obtain a uniform and transparent green complexed sol. This step uses a green complexing agent to replace a toxic chelating agent, thereby achieving uniform molecular-level dispersion of metal ions and avoiding the formation of impurity phases from the source.

[0028] The advantages are: through the above-mentioned stepwise dissolution and step-speed stirring, the full dissolution of multi-metal ions is effectively guaranteed; by utilizing the synergistic complexation of sodium citrate / tartaric acid and glycine dual ligands, molecular-level stable dispersion of metal ions can be achieved at near-neutral pH, without the need for high temperature or strong acid conditions.

[0029] Specifically, the composite gelation conditions in step three are as follows: dopant and biomass carbon source are added sequentially to the green complex sol, and stirred at a speed of 100-200 r / min for 3-4 hours under normal pressure water bath conditions at 50-55℃.

[0030] The advantages are: by using a low-temperature water bath (50-55℃) and low-speed stirring (100-200r / min), the three steps of doping, carbon composite and gelation are combined into one, which can effectively avoid the precipitation of impurity phases induced by high temperature, thereby ensuring that the carbon source and metal complex are uniformly cross-linked to form a three-dimensional network structure.

[0031] Specifically, in step four, the low-temperature structure control conditions are as follows: the composite wet gel is transferred to a sealed container and aged in a normal pressure water bath at 85-90℃ for 6-12 hours, supplemented by intermittent ultrasonic treatment every 2 hours for 15-20 minutes at a power of 200-400W.

[0032] The advantages are: by aging at 85-90℃ and normal pressure, and then simultaneously combining intermittent ultrasonic treatment, the mass transfer and uniform growth of crystal nuclei are enhanced by utilizing the ultrasonic cavitation effect, which compensates for the insufficient reaction kinetics under low temperature and normal pressure, thereby achieving the controllable construction of grain refinement and hierarchical porous structure.

[0033] Specifically, the low-temperature curing conditions in step five are as follows: the composite dry gel precursor is placed in a tube furnace at a concentration greater than 99.99%. In-situ carbonization is carried out by heating to 400–420°C at a rate of 3–5°C / min under an inert atmosphere and holding at that temperature for 2–3 hours. The chemical reaction formulas involved in this process are as follows: (1) Carbonization of biomass carbon sources: ; In the formula, The basic structural formula of glucose unit (such as cellulose and starch) is n, which represents the degree of polymerization of biomass polysaccharide (i.e. the number of repeating monosaccharide units). Under low temperature conditions (400-420℃), carbonization is incomplete, generating amorphous carbon instead of graphite, which is conducive to the formation of conductive carbon network. (2) Decomposition of the pre-intercalating agent (ammonium acetate): , (Embedded between layers); In the formula, It is ammonium acetate. These refer to protons or hydrated hydrogen ions existing between layers of layered materials (such as manganese vanadium bismuth oxide). Ammonium acetate decomposes into a gaseous state upon heating. and (Acetic acid), both escape from the system, forming The size is suitable, and it can be embedded in the interlayer in situ, thus avoiding the cumbersome steps of adding ammonium salts; (3) Glycine pyrolysis nitrogen doping: →Nitrogen-containing gas + nitrogen-doped carbon; In the formula, It is glycine.

[0034] The advantages are: by replacing the traditional high-temperature treatment of 700-900℃ with the low-temperature carbonization of 400-420℃, energy consumption is reduced by more than 50%; at the same time, the in-situ decomposition pre-intercalation of ammonium acetate and nitrogen doping of glycine are coupled, thereby achieving carbon coating, pre-intercalation and doping triple modification in one step, so that the carbon distribution is uniform and the residual carbon content is controllable.

[0035] Specifically, the mechanical activation post-treatment process in step six: S4.1 Mix the crude positive electrode material with deionized water at a solid-liquid mass ratio of 1:1.5, and ball mill it in a planetary ball mill at a speed of 400-500 r / min for 1-2 hours to achieve mechanical activation, particle refinement and carbon distribution homogenization. S4.2 After ball milling, the slurry is centrifuged at 5000-6000 r / min for 10-15 min, then washed with deionized water 2-3 times (with repeated centrifugation after each wash), and then placed in a vacuum drying oven at 60-70℃ for 7-8 h. Finally, it is passed through a 200-400 mesh sieve to obtain the final aqueous zinc-ion battery cathode material. Ball milling mechanical activation further improves the conductivity and structural stability of the material. The entire process is free of strong acids and alkalis and toxic waste liquids, with a yield of over 98%.

[0036] The advantages are: through the ball mill mechanical activation with optimized solid-liquid ratio, the particles can be further refined and the carbon distribution can be homogenized; by combining centrifugal washing and vacuum drying, the entire process is free of strong acids and alkalis and toxic waste liquids, and the product has high purity and a yield of over 98%.

[0037] Three cathode material samples with different ratios and raw material combinations were prepared using the preparation process of this invention, as detailed below: Example 1 Manganese source (manganese sulfate recycled from waste batteries) 22 parts, vanadium source (vanadium pentoxide) 18 parts, bismuth source (bismuth nitrate) 6 parts, green complexing agent (sodium citrate) 13 parts, biomass carbon source (rice husk powder + sodium alginate, mass ratio 1:1) 9 parts, dopant (cobalt acetate) 2 parts, pre-intercalating agent (ammonium acetate) 3 parts, glycine 0.8 parts, deionized water balance.

[0038] Preparation steps: Step 1: Raw material preparation: Weigh each raw material according to the above weight proportions and set aside.

[0039] Step 2: Preparation of green complexed sol: Manganese source, vanadium source, and bismuth source were dissolved in deionized water in sequence and stirred at 450 r / min at room temperature until completely dissolved (20 min); then, green complexing agents sodium citrate and glycine were added, and stirring was continued at 250 r / min for 45 min to allow the metal ions to form stable soluble complexes with the complexing agents; finally, pre-intercalating agent ammonium acetate was added, and the pH was adjusted to 5.2 using dilute acetic acid or dilute ammonia to obtain a uniform and transparent green complexed sol; Step 3, In-situ doping-biomass carbon composite gelation: Cobalt acetate dopant and biomass carbon source are added sequentially to the green complex sol. The mixture is stirred at 150 r / min for 3.5 h under normal pressure water bath conditions at 53 °C. This allows the dopant ions to be uniformly embedded into the metal complex framework. At the same time, the biomass carbon source and the metal complex undergo a cross-linking reaction to form a composite wet gel with a three-dimensional network structure. Step 4, Low-Temperature Structure Control (Ultrasonic-Assisted Aging): The composite wet gel was transferred to a sealed container and aged for 9 hours at 88°C under normal pressure, supplemented by intermittent ultrasonic treatment: 18 minutes of ultrasonic treatment every 2 hours, with an ultrasonic power of 300W. After aging, it was naturally cooled to room temperature to obtain a composite dry gel precursor with a hierarchical porous structure. Step 5, Low-Temperature Curing: Place the composite dry gel precursor in a tube furnace and cure it at a concentration greater than 99.99%. Under an inert atmosphere (flow rate 100 mL / min), the temperature was increased to 410℃ at a rate of 4℃ / min and held for 2.5 h for in-situ carbonization, converting the biomass carbon source into a continuous conductive carbon network. Simultaneously, the pre-intercalating agent (ammonium acetate) decomposed to produce… Intercalation between layers, glycine decomposes to provide nitrogen doping, and then it is naturally cooled to room temperature to obtain a crude cathode material with carbon coating, in-situ doping, and pre-intercalation synergistic optimization. Step Six: Mechanical Activation Post-treatment: The crude positive electrode material is mixed with deionized water at a solid-liquid mass ratio of 1:1.5 and ball-milled in a planetary ball mill at 450 r / min for 1.5 h to achieve mechanical activation, particle refinement, and carbon distribution homogenization. The ball-milled slurry is centrifuged at 5500 r / min for 12 min, then washed three times with deionized water (centrifuged again after each wash), and then placed in a vacuum drying oven at 65℃ for 7.5 h. Finally, it is passed through a 300-mesh sieve to obtain the final aqueous zinc-ion battery positive electrode material, numbered ZIB-1.

[0040] Example 2 25 parts manganese source (recovered manganese sulfate), 15 parts vanadium source (ammonium metavanadate), 8 parts bismuth source (bismuth nitrate), 10 parts green complexing agent (tartaric acid), 11 parts biomass carbon source (straw extract + sodium alginate, mass ratio 2:1), 1 part dopant (nickel sulfate), 4 parts pre-intercalating agent (potassium acetate), 1.2 parts glycine, and the remainder deionized water.

[0041] The product ZIB-2 was prepared using the same steps as in Example 1.

[0042] Example 3 20 parts manganese source (recovered manganese sulfate), 20 parts vanadium source (vanadium pentoxide), 5 parts bismuth source (bismuth nitrate), 16 parts green complexing agent (sodium citrate), 7 parts biomass carbon source (rice husk powder + straw extract, mass ratio 1:2), 3 parts dopant (cobalt acetate), 2 parts pre-intercalating agent (ammonium oxalate), 0.5 parts glycine, and the remainder deionized water.

[0043] The product ZIB-3 was prepared using the same steps as in Example 1.

[0044] Performance Tests and Results The positive electrode material products obtained through the preparation processes of Examples 1-3 above were assembled into CR2032 coin-type aqueous zinc-ion batteries (the negative electrode is zinc foil, and the electrolyte is...). (Aqueous solution), followed by electrochemical performance testing, yielded the following results: Table 2 Electrochemical performance of cathode materials in different embodiments ; Table 2 shows that Example 3 (ZIB-3) has the highest initial discharge specific capacity (341.3 mAh / g) and the best rate performance (85.1%). Furthermore, after 500 cycles, its capacity retention rate is as high as 96.5%. It also has the smallest average particle size (2.5 μm) and the largest specific surface area (52.6 m² / g). This indicates that using the formulation combination of sodium citrate as a complexing agent, rice husk powder + straw extract as a composite carbon source, cobalt acetate as a dopant, and ammonium oxalate as a pre-intercalating agent, combined with the process of this invention, can achieve superior electrochemical performance. In addition, Examples 1 and 2 also exhibit good overall performance, verifying the wide adaptability of the process of this invention to different raw material ratios.

[0045] In summary, this invention achieves resource utilization by recovering manganese from waste batteries and extracting vanadium from vanadium slag. It replaces toxic chelating agents with green complexing agents such as sodium citrate or tartaric acid, completing in-situ doping, carbon composite, and gelation integration processes under low-temperature water bath conditions. Following ultrasonic-assisted low-temperature aging and low-temperature carbonization at 400–420°C, it achieves synergistic optimization of carbon coating, pre-intercalation, and nitrogen doping, reducing total energy consumption by more than 50% compared to traditional high-temperature processes. Finally, the finished product is obtained through ball milling mechanical activation and centrifugal washing. The entire process is free of strong acids, alkalis, and toxic waste liquids, achieving a yield of over 98%. The prepared cathode material possesses a hierarchical porous structure, high specific surface area, and nanoscale particle size, exhibiting excellent electrochemical performance. This provides a green and large-scale production method for the resource utilization of waste batteries and the production of high-performance aqueous zinc-ion battery cathode materials.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A green preparation process for aqueous zinc-ion battery cathode material, characterized in that, Includes the following steps: Step 1: Raw materials and their weight parts: manganese source, vanadium source, bismuth source, green complexing agent, biomass carbon source, dopant, pre-intercalation agent, glycine and deionized water; Step 2, Green Complexing Sol: Dissolve manganese source, vanadium source and bismuth source in deionized water in sequence, stir at room temperature until completely dissolved, then add green complexing agent and glycine, continue stirring, and finally add pre-intercalating agent to adjust pH value to obtain green complexing sol; Step 3, Composite Gelization: Add dopants and biomass carbon sources sequentially to the green complex sol, and stir under normal pressure water bath conditions until the doped ions are uniformly embedded in the metal complex framework to form a composite wet gel; Step 4, Low-temperature structure control: The composite wet gel is transferred to a sealed container and aged under normal pressure water bath conditions, with intermittent ultrasonic treatment during the process. After aging, it is naturally cooled to room temperature to obtain the composite dry gel precursor. Step 5, Low-Temperature Curing: The composite dry gel precursor is placed in a tube furnace and heated to the target temperature under an inert atmosphere. In-situ carbonization is then performed at the target temperature, while the pre-intercalating agent decomposes and produces... The material is embedded between layers and then naturally cooled to room temperature to obtain crude cathode material. Step 6, Mechanical activation post-processing: Mix the crude positive electrode material with deionized water according to the set solid-liquid ratio, and then perform ball milling, centrifugal washing, vacuum drying and sieving to obtain the final aqueous zinc-ion battery positive electrode material.

2. The green preparation process for an aqueous zinc-ion battery cathode material according to claim 1, characterized in that, The raw materials and their weight parts in step one are as follows: 20-25 parts manganese source; 15-20 parts vanadium source; 5-8 parts bismuth source; 10-16 parts green complexing agent; 7-11 parts biomass carbon source; 1-3 parts dopant; 2-4 parts pre-intercalating agent; 0.5-1.2 parts glycine; and the remaining raw material is deionized water.

3. The green preparation process for an aqueous zinc-ion battery cathode material according to claim 1, characterized in that, The manganese source is selected from manganese sulfate extracted from the leachate of waste zinc-manganese batteries, and the extraction steps are as follows: S1.1 Crushing and sorting: Waste zinc-manganese batteries are mechanically crushed, magnetically separated and screened to obtain manganese-rich cathode powder, with the crushing particle size controlled between 100 and 200 mesh; S1.2 Green Reducing Leaching: The positive electrode powder is mixed with sulfuric acid solution and oxalic acid reducing agent. The sulfuric acid concentration is controlled between 1.0 and 3.0 mol / L, the liquid-solid ratio between 5:1 and 10:1, the leaching temperature between 60 and 90℃, and the leaching time between 1 and 4 hours. Restore to It dissolves, yielding a leachate containing manganese sulfate; S1.3 Post-treatment: The leachate is filtered to remove insoluble residues. The filtrate is adjusted to pH 5.0-5.5 to precipitate and remove iron and aluminum. It is then evaporated and concentrated at 90-95℃ and vacuum degree -0.09--0.095MPa to a solution density of 1.50-1.55g / cm³. It is then cooled to room temperature at a cooling rate of 6-8℃ / h to crystallize. It is then centrifuged at 4000-5000r / min. Finally, it is vacuum dried at 100-105℃ and vacuum degree -0.09--0.1MPa for 6-8h to obtain manganese sulfate crystals.

4. The green preparation process for an aqueous zinc-ion battery cathode material according to claim 1, characterized in that, The vanadium source is selected from either vanadium pentoxide extracted from vanadium slag or ammonium metavanadate, and the extraction steps are as follows: S2.1 Crushing and ball milling: Crush the vanadium slag to a particle size ≤0.074mm, control the ball-to-material ratio between 5:1 and 10:1, and the ball milling time between 2.5 and 3.0h; S2.2, Sodium carbonate roasting: Mix the ball-milled vanadium slag with sodium carbonate at a mass ratio of 100:15-25, control the roasting temperature between 650-700℃ and the roasting time between 1-2h, so that vanadium is converted into soluble sodium vanadate. S2.3 Water immersion: Mix the roasted clinker with water, control the liquid-solid ratio between 3:1 and 6:1, the water immersion temperature between 85 and 90°C, the water immersion time between 1 and 2 hours, and the pH value between 8 and 9, and filter to obtain a water immersion solution containing sodium vanadate. S2.4 Ammonium salt precipitation of vanadium: Add ammonium sulfate to the water leaching solution, control the amount of ammonium salt to be 1.0 to 1.5 times the theoretical amount, the pH value of vanadium precipitation to be between 8 and 9, the precipitation temperature to be between 40 and 50℃, stir the reaction for 45 to 55 minutes, and filter to obtain ammonium metavanadate precipitate. S2.5 Calcination and decomposition: Calcine ammonium metavanadate at 650-700℃ for 1-2 hours to decompose it into vanadium pentoxide; or use ammonium metavanadate directly as a vanadium source.

5. The green preparation process for an aqueous zinc-ion battery cathode material according to claim 1, characterized in that, The bismuth source is bismuth nitrate; the green complexing agent is selected from sodium citrate or tartaric acid; the biomass carbon source is selected from two of rice husk powder, sodium alginate or straw extract; the dopant is selected from one of cobalt acetate, cobalt acetate or nickel sulfate; and the pre-intercalating agent is selected from one of ammonium acetate, potassium acetate or ammonium oxalate.

6. The green preparation process for an aqueous zinc-ion battery cathode material according to claim 1, characterized in that, The preparation process of the green complexed sol in step two is as follows: S3.1 Dissolve the manganese source, vanadium source and bismuth source in deionized water in sequence, and stir at 400-500 r / min at room temperature until completely dissolved; S3.2, then add the green complexing agent and glycine, and continue stirring at 200-300 r / min for 30-60 min; S3.3 Finally, add the pre-intercalating agent and adjust the pH value to 4.5-6.0 to obtain a green complexed sol.

7. The green preparation process for an aqueous zinc-ion battery cathode material according to claim 1, characterized in that, The composite gelation conditions in step three are as follows: dopant and biomass carbon source are added sequentially to the green complex sol, and the mixture is stirred at a speed of 100-200 r / min for 3-4 hours under normal pressure water bath conditions at 50-55℃.

8. The green preparation process for an aqueous zinc-ion battery cathode material according to claim 1, characterized in that, The low-temperature structure control conditions in step four are as follows: the composite wet gel is transferred to a sealed container and aged in a normal pressure water bath at 85-90℃ for 6-12 hours, supplemented by intermittent ultrasonic treatment every 2 hours for 15-20 minutes at a power of 200-400W.

9. The green preparation process for an aqueous zinc-ion battery cathode material according to claim 1, characterized in that, The low-temperature curing conditions in step five are as follows: the composite dry gel precursor is placed in a tube furnace at a concentration greater than 99.99%. Under an inert atmosphere, the temperature is increased to 400–420℃ at a rate of 3–5℃ / min, and held at this temperature for 2–3 hours for in-situ carbonization. The carbonization reaction formula for the biomass carbon source is as follows: In the formula, For glucose units, n represents the degree of polymerization of biomass polysaccharides.

10. The green preparation process for an aqueous zinc-ion battery cathode material according to claim 1, characterized in that, The mechanical activation post-treatment process in step six: S4.1 Mix the crude positive electrode material with deionized water at a solid-liquid mass ratio of 1:1.5, and ball mill in a planetary ball mill at a speed of 400-500 r / min for 1-2 hours; S4.2 After ball milling, the slurry is centrifuged at 5000-6000 r / min for 10-15 min, then washed with deionized water 2-3 times, and then placed in a vacuum drying oven at 60-70℃ for 7-8 h. Finally, it is passed through a 200-400 mesh sieve to obtain the final aqueous zinc-ion battery cathode material.

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