Electrolytic anolyte coating for water electrolysis based on waste lithium batteries and its preparation method

Abstract

This invention relates to the field of solid waste resource utilization and electrocatalytic materials technology, and particularly to an anode catalytic coating for water electrolysis based on waste lithium batteries and its preparation method. The invention obtains pretreated cathode powder by pretreating waste lithium battery cathode materials, recovers Ni, Co, and Fe metal ions by acid leaching of the pretreated cathode powder and produces lithium carbonate as a byproduct, adds biomass carbon source to adjust the ratio and then prepares composite catalyst powder by hydrothermal carbonization, and coats it on the surface of a conductive substrate to form an anode catalytic coating. At the same time, it treats wastewater in an environmentally friendly manner, achieving low-cost resource utilization and high-performance catalysis.

Description

Technical Field

[0001] This invention relates to the fields of solid waste resource utilization and electrocatalytic materials technology, specifically to a method for preparing an anode catalytic coating for alkaline water electrolysis oxygen evolution reaction (OER) using waste positive electrode material from retired lithium-ion batteries as raw material, which can be applied to the electrode preparation of industrial alkaline water electrolysis hydrogen production equipment. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage industries, the amount of retired lithium-ion batteries being scrapped is increasing year by year. Currently, the mainstream recycling processes for waste lithium batteries are mainly pyrometallurgical and hydrometallurgical methods, which can mostly only recover basic metal salts. The added value of the products is low, and there are problems such as complex processes, high costs, and secondary pollution, making it difficult to achieve high-value utilization of solid waste.

[0003] Meanwhile, alkaline water electrolysis for hydrogen production is a core technology in green hydrogen production. The oxygen evolution reaction (OER) at the anolyte is the rate-limiting step in the entire reaction, requiring a highly efficient catalyst to reduce the reaction overpotential. Currently, commercially available OER catalysts are mostly precious metal materials such as IrO2 and RuO. Although they exhibit excellent catalytic performance, the scarcity and high cost of these precious metals significantly increase the cost of hydrogen production, limiting their large-scale industrial application. Among non-precious metal catalysts, NiFe-based catalysts have become a research hotspot due to their low cost and good activity. However, traditional NiFe-based catalysts suffer from problems such as high overpotential at high current densities, poor long-term operational stability, and rapid performance degradation, making it difficult to meet the requirements of 50-200 mA / cm² for industrial water electrolysis. 2 Long-term operation requirements under high current conditions.

[0004] In recent years, some studies have attempted to convert waste lithium-ion battery cathode materials into water electrolysis catalysts. However, most existing technologies suffer from cumbersome processes and insufficient catalyst performance. They either only achieve activity at low currents, failing to adapt to high-current industrial conditions, or exhibit severe degradation over long periods of operation, with potential decay exceeding 0.05 mV / h after 1000 hours of operation. Furthermore, most processes lack comprehensive environmental protection solutions, resulting in inadequate treatment of acid leaching wastewater and impurities, hindering truly green industrial production. Therefore, developing an industrial-grade water electrolysis catalytic coating preparation method that simultaneously achieves high-value utilization of waste lithium-ion batteries, low cost, high stability, and low degradation has become a pressing issue in this field. Summary of the Invention

[0005] To address the technical problems of low added value in existing waste lithium battery recycling, high cost of water electrolysis catalysts, poor stability under high current conditions, and difficulty in green and large-scale production, this invention provides a method for preparing an anode catalytic coating for water electrolysis based on waste lithium batteries. This method solves these problems in existing waste lithium battery recycling technologies and is equipped with environmentally friendly treatment processes to achieve green production throughout the entire process.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for preparing a catalytic coating for water electrolysis based on waste lithium batteries includes the following steps:

[0008] (1) Solid waste raw material pretreatment: Collect retired or discarded lithium battery cathode materials, remove aluminum foil current collectors and binders, and crush to 80-120 mesh to obtain pretreated cathode powder;

[0009] (2) Metal ion leaching and recovery: The pretreated cathode powder is mixed with a sulfuric acid solution with a concentration of 2~6 mol / L at a solid-liquid ratio of 1:8-1:15, and stirred at 50-80℃ for 2-4 hours to leach Ni. 2+ Co 2+ Fe 3+ After filtration, a Ni-containing product was obtained. 2+ Co 2+ Fe 3 + The leachate, while simultaneously recovering Li from the filtrate. + And prepare lithium carbonate byproduct;

[0010] (3) Preparation of catalytic precursor: Add biomass carbon source to leachate and adjust Ni 2+ Co 2+ Fe 3+ The molar ratio of the two components was 1:(0.6-1.0):(0.4-0.6), resulting in a catalytic precursor solution.

[0011] (4) Low-temperature hydrothermal-carbonization composite: The catalyst precursor solution is transferred to the reactor and hydrothermally reacted at 100-160℃ for 8-12h, followed by carbonization at 300-400℃ for 2-3h under nitrogen atmosphere to obtain Ni-Co-Fe oxide / carbon composite catalyst powder.

[0012] (5) Coating preparation and environmental protection treatment: The catalyst powder and binder are mixed to form a slurry, which is then coated onto the surface of the conductive substrate by electrochemical deposition or spraying. After drying, the anodic catalytic coating is obtained. At the same time, the acidic wastewater generated during the acid leaching process is neutralized and flocculated before being discharged in compliance with standards.

[0013] As a preferred technical solution, the retired or discarded lithium battery cathode material is selected from one of the following: (a) lithium nickel cobalt manganese oxide battery (NCM) + lithium iron phosphate battery (LFP); (b) lithium cobalt oxide battery (LiCoO2) + lithium iron phosphate battery (LFP) + nickel-containing waste; (c) lithium nickel cobalt aluminum oxide battery (NCA) + lithium iron phosphate battery (LFP); (d) mixed type of waste batteries, after testing, the ratio of each type of battery is adjusted to achieve the target molar ratio; the sources of Fe, Co, and Ni include, but are not limited to, waste battery cathode material, battery steel shell acid leaching solution, or industrial waste.

[0014] As a preferred technical solution, the biomass carbon source is one or more of glucose, sucrose, starch, straw charcoal, wood chip charcoal, or food waste, and the mass ratio of the biomass carbon source to the total mass of metal ions in the leachate is (0.8-1.2):1.

[0015] As a preferred technical solution, the total molar content of Mn, Al, and Li impurities in the catalytic coating does not exceed 10% of the total molar content of Fe-Co-Ni.

[0016] As a preferred technical solution, the conductive substrate is one of nickel mesh, nickel foam, titanium mesh, or conductive carbon cloth, and the specific surface area of ​​the substrate is ≥100 cm². 2 / g.

[0017] As a preferred technical solution, in step 2, Li + The recovery method is as follows: add sodium carbonate solution to the leachate filtrate, adjust the pH to 8-9, precipitate to obtain lithium carbonate precursor, filter, wash and dry to obtain industrial grade lithium carbonate; the treatment method for acidic wastewater in step 5 is as follows: add calcium hydroxide solution to the acidic wastewater to neutralize to pH=6-8, add polyacrylamide flocculant to precipitate impurities, filter and discharge the clear liquid after meeting the standards, and use the filter residue as a resource for building material raw materials.

[0018] As a preferred technical solution, the preparation method of the slurry in step 5 is as follows: the catalyst powder and polyvinylidene fluoride (PVDF) are mixed at a mass ratio of 9:1, and N-methylpyrrolidone (NMP) is added to prepare a slurry with a solid content of 20%-30%, which is then ultrasonically dispersed for 30-60 minutes; wherein, the process parameters for electrochemical deposition are: current density 10-30 mA / cm², deposition time 20-40 minutes, and deposition temperature at room temperature; the process parameters for spraying are: spraying pressure 0.3-0.5 MPa, spraying distance 15-25 cm, and 3-5 spraying times.

[0019] As a preferred technical solution, the Ni-Co-Fe oxide / carbon composite catalyst has a particle size of 40-220 nm, a specific surface area of ​​≥80 m² / g, and a pore volume of 0.2-0.4 cm³ / g.

[0020] The present invention also provides an electrolytic catalytic coating for water electrolysis based on waste lithium batteries, which is prepared by the above-described preparation method.

[0021] The beneficial effects of this invention are:

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. This invention uses retired and discarded lithium battery cathode waste as the main raw material and is compatible with various industrial wastes containing iron and nickel, transforming low-value solid waste into high-value industrial catalysts. Compared with commercial IrO2 catalysts, the cost is reduced by more than 60%, significantly lowering the material cost for hydrogen production through water electrolysis.

[0024] 2. The Ni-Co-Fe oxide / carbon composite catalyst prepared in this invention achieves an overpotential as low as below 280mV under industrial-grade high current density (50-200mA / cm²) and high-temperature conditions through the synergistic effect of the three metals and the composite modification of the carbon support. Simultaneously, its potential decay rate over long-term operation is ≤0.02mV / h, superior to traditional NiFe catalysts, and it can operate stably for over 1000h, perfectly meeting the long-term operational requirements of industrial water electrolysis.

[0025] 3. This invention employs a low-temperature hydrothermal-carbonization process, which features mild reaction conditions and low energy consumption. Simultaneously, it incorporates lithium recovery and wastewater treatment processes. The leached lithium can be recovered as industrial-grade lithium carbonate, and the acid leaching wastewater, after neutralization and flocculation, meets discharge standards. The filter residue can also be utilized as a resource, achieving green production throughout the entire process with no secondary pollution.

[0026] 4. Compared with the noble metal IrO2 catalyst, the catalytic coating of the present invention reduces the cost by more than 60%, and reduces the overpotential by 15%-25% compared with the traditional NiFe hydroxide catalyst.

[0027] 5. The coating process of this invention is compatible with both electrochemical deposition and spraying methods, both of which allow for precise control of catalyst loading, ensuring a tight bond between the coating and the substrate. Both processes are mature and stable, easy to scale up, and suitable for large-scale industrial electrode production, possessing strong industrialization potential. Attached Figure Description

[0028] Figure 1 This is a process flow diagram of the preparation process of the alkaline water electrolysis anode catalytic coating of the present invention.

[0029] Figure 2 This is a photograph of a blank conductive substrate without an anodic catalyst coating.

[0030] Figure 3 This is a physical image of the finished alkaline water electrolysis anode electrode loaded with the anodic catalytic coating of this invention.

[0031] Figure 4 This is a high-magnification scanning electron microscope (SEM) image of the Ni-Co-Fe oxide / carbon composite catalyst powder prepared in Example 1.

[0032] Figure 5 This is a general SEM image of the Ni-Co-Fe oxide / carbon composite catalyst powder prepared in Example 1. Detailed Implementation

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0034] Example 1

[0035] Solid waste pretreatment: Collect the cathode waste of retired NCM ternary lithium batteries and LFP lithium iron phosphate batteries, manually peel off the aluminum foil current collector, remove the surface adhesive, and crush the mixed powder to 100 mesh to obtain pretreated cathode powder.

[0036] Metal ion leaching and recovery: The pretreated powder was mixed with a 4 mol / L sulfuric acid solution at a solid-liquid ratio of 1:10 and stirred at 65°C for 3 hours to leach Ni. 2+ Co 2+ Fe 3+ The leachate was obtained by filtration, and the molar ratio of Ni, Co and Fe was found to be 1:0.8:0.5, which met the target ratio. Subsequently, sodium carbonate solution was added to the leachate to adjust the pH to 8.5, and lithium carbonate precursor was precipitated. After filtration, washing and drying, industrial-grade lithium carbonate was obtained with a lithium recovery rate of 92.3%.

[0037] Preparation of catalytic precursor: Glucose was added to the leachate as a biomass carbon source, with a total mass ratio of carbon source to metal ions of 1:1. The mixture was stirred until homogeneous to obtain a catalytic precursor solution.

[0038] Low-temperature hydrothermal-carbonization composite: The precursor solution was transferred to a hydrothermal reactor and hydrothermally reacted at 140℃ for 10 h. The product was then removed, dried, and carbonized at 350℃ for 2.5 h under a nitrogen atmosphere to obtain Ni-Co-Fe oxide / carbon composite catalyst powder. The powder particle size was 80-150 nm, the specific surface area was 92 m² / g, the pore volume was 0.31 cm³ / g, and the total content of impurities such as Mn and Al in the catalyst layer was 7.8%, which is lower than the limit of 10%.

[0039] Coating preparation: The catalyst powder and PVDF were mixed at a mass ratio of 9:1, and NMP was added to make a slurry with a solid content of 25%. The slurry was ultrasonically dispersed for 45 min. Then, using nickel foam (specific surface area 150 cm² / g) as the substrate, the anodic catalytic coating was coated by electrochemical deposition at a current density of 20 mA / cm² and a deposition time of 30 min at room temperature. After drying, the anodic catalytic coating was obtained.

[0040] Wastewater treatment: Acidic wastewater generated during the acid leaching process is neutralized to pH 7.0 with calcium hydroxide, and impurities are precipitated by adding PAM. After filtration, the clear liquid meets the discharge standards, and the filter residue is recycled as a building material raw material.

[0041] Morphology characterization: The microstructure of the Ni-Co-Fe oxide / carbon composite catalyst powder prepared in this embodiment was characterized using scanning electron microscopy. The results are as follows: Figure 4 , Figure 5 As shown, the catalyst powder consists of uniform spherical aggregates formed by the agglomeration of nanoparticles with a particle size of 80-150 nm. The diameter of a single aggregate is 5-10 μm, and the specific surface area of ​​the powder reaches 92 m². 2 / g, pore volume 0.31cm 3 / g.

[0042] Performance testing: Under the conditions of 6M KOH electrolyte, 80℃, and 100mA / cm², the OER overpotential of the coating is 265mV; after 1000h constant current stability testing, the final potential decay rate is 0.018mV / h, and there is no significant performance degradation after 1000h operation, indicating stable operation.

[0043] Example 2

[0044] Solid waste raw material pretreatment: Same as in Example 1, crushed to 80 mesh.

[0045] Metal ion leaching and recovery: The pretreated powder was mixed with a 2 mol / L sulfuric acid solution at a solid-liquid ratio of 1:8 and stirred at 50°C for 2 hours to leach metal ions. The leachate was obtained by filtration, and the molar ratio of Ni, Co, and Fe was adjusted to 1:0.6:0.4. Subsequently, sodium carbonate solution was added to the leachate to adjust the pH to 8.5, and lithium carbonate precursor was precipitated. After filtration, washing, and drying, industrial-grade lithium carbonate was obtained, with a lithium recovery rate of 88.6%.

[0046] Preparation of catalytic precursor: Sucrose was added to the leachate as a biomass carbon source, with a total mass ratio of carbon source to metal ions of 0.8:1. The mixture was stirred until homogeneous to obtain a catalytic precursor solution.

[0047] Low-temperature hydrothermal-carbonization composite: The precursor solution was transferred to a hydrothermal reactor and hydrothermally reacted at 100℃ for 8 hours, followed by carbonization at 300℃ for 2 hours under a nitrogen atmosphere to obtain Ni-Co-Fe oxide / carbon composite catalyst powder. The powder particle size was 40-180nm, the specific surface area was 80m² / g, the pore volume was 0.20cm³ / g, and the total content of impurities such as Mn and Al in the catalyst layer was 8.2%, which is lower than the limit of 10%.

[0048] Coating preparation and wastewater treatment: Electrochemical deposition current density 10 mA / cm², deposition time 20 min, other procedures are the same as in Example 1.

[0049] Performance testing: Under the same operating conditions as in Example 1, the OER overpotential of the coating was 278mV; after a 1000h constant current stability test, the final potential decay rate was 0.023mV / h, and there was no significant performance degradation after 1000h of operation, indicating stable operation.

[0050] Example 3

[0051] Solid waste raw material pretreatment: Same as in Example 1, crushed to 120 mesh.

[0052] Metal ion leaching and recovery: The pretreated powder was mixed with a 6 mol / L sulfuric acid solution at a solid-liquid ratio of 1:15 and stirred at 80℃ for 4 h to leach metal ions. The leachate was obtained by filtration, and the molar ratio of Ni, Co, and Fe was adjusted to 1:1.0:0.6. Subsequently, sodium carbonate solution was added to the leachate to adjust the pH to 8.5, and lithium carbonate precursor was precipitated. After filtration, washing, and drying, industrial-grade lithium carbonate was obtained, with a lithium recovery rate of 93.5%.

[0053] Preparation of catalytic precursor: Starch was added to the leachate as a biomass carbon source, with a total mass ratio of carbon source to metal ions of 1.2:1. The mixture was stirred until homogeneous to obtain a catalytic precursor solution.

[0054] Low-temperature hydrothermal-carbonization composite: The precursor solution was transferred to a hydrothermal reactor and hydrothermally reacted at 160℃ for 12 h, followed by carbonization at 400℃ for 3 h under a nitrogen atmosphere to obtain Ni-Co-Fe oxide / carbon composite catalyst powder. The powder particle size was 160-220 nm, the specific surface area was 108 m² / g, the pore volume was 0.4 cm³ / g, and the total content of impurities such as Mn and Al in the catalyst layer was 7.5%, which is lower than the limit of 10%.

[0055] Coating preparation and wastewater treatment: Electrochemical deposition current density 30 mA / cm², deposition time 40 min, other conditions are the same as in Example 1.

[0056] Performance testing: Under the same operating conditions, the OER overpotential of the coating is 269mV; after 1000h constant current stability testing, the final potential decay rate is 0.021mV / h, and there is no significant performance degradation after 1000h operation, indicating stable operation.

[0057] Comparative Example 1

[0058] The NiFe hydroxide catalyst was prepared by the traditional co-precipitation method. The specific steps were as follows: a mixed solution of nickel nitrate and ferric nitrate was prepared according to the Ni:Fe molar ratio of 1:0.5. Sodium hydroxide solution was added to adjust the pH to 10. The solution was stirred in a water bath at 60°C for 4 hours, allowed to stand and age for 12 hours, and then filtered, washed and dried to obtain NiFe hydroxide catalyst powder. The coating was prepared according to the same slurry preparation and coating process as in Example 1, and the performance was tested simultaneously.

[0059] Performance testing: Under the same operating conditions, the OER overpotential of this coating is 320mV; the decay rate of the 1000h stability test is 0.052mV / h, and significant performance degradation occurs after 500h of operation, which cannot meet the requirements of long-term industrial operation.

[0060] Comparative Example 2

[0061] Using a commercial IrO2 noble metal catalyst, a coating with the same loading was prepared using the same slurry preparation and coating process as in Example 1, and performance testing and cost accounting were carried out simultaneously.

[0062] Performance testing: Under the same operating conditions, the OER overpotential of the coating is 260mV, which is close to the performance of Example 1. However, the raw material cost of the catalyst is 3.2 times that of Example 1. The cost of the present invention is reduced by 68.75%, which significantly reduces the cost of hydrogen production.

[0063] Comparative Example 3

[0064] Except for the absence of biomass carbon source, the other raw materials, process parameters, and preparation steps are completely consistent with those in Example 1. Carbon-free Ni-Co-Fe oxide catalyst powder was prepared and coated according to the same process, and its performance was tested simultaneously.

[0065] Performance testing: Under the same operating conditions, the OER overpotential of the coating is 308mV; the decay rate of the 1000h stability test is 0.046mV / h. After 600h of operation, obvious catalyst shedding and performance degradation are observed, proving that the introduction of biomass carbon source plays a key role in improving the conductivity, structural stability and catalytic activity of the catalyst.

[0066] Comparative Example 4

[0067] Except for replacing the biomass carbon source (glucose) with an equal mass of commercial conductive carbon black (Super P), the other raw materials, process parameters, and preparation steps were completely consistent with those in Example 1. Ni-Co-Fe oxide / commercial carbon black composite catalyst powder was prepared, and a coating was made according to the same process. Performance tests were conducted simultaneously.

[0068] Performance testing: Under the same operating conditions, the OER overpotential of this coating is 288mV; the decay rate of the 1000h stability test is 0.035mV / h. The results show that commercial carbon black, unlike biomass carbon sources, cannot undergo in-situ polymerization during the hydrothermal stage to uniformly anchor metal ions, resulting in uneven distribution and easy agglomeration of metal particles on the carbon black surface, and is also more expensive. This demonstrates that the biomass carbon source used in this invention is superior to commercial carbon black.

[0069] Comparative Example 5

[0070] Except for adjusting the hydrothermal reaction temperature to 200℃ and the carbonization temperature to 500℃ (both exceeding the parameter range defined in this invention), the other raw materials, process parameters, and preparation steps are completely consistent with Example 1. Ni-Co-Fe oxide / carbon composite catalyst powder was prepared, and a coating was made according to the same process. Performance tests were conducted simultaneously.

[0071] Performance testing: Under the same operating conditions, the OER overpotential of this coating is 295mV; the decay rate in the 1000h stability test is 0.038mV / h, and the catalyst powder shows obvious particle agglomeration and a decrease in specific surface area to only 56m². 2 / g, demonstrating that the low-temperature hydrothermal-carbonization process parameters defined in this invention play a decisive role in the microstructure and performance stability of the catalyst.

[0072] Comparative Example 6

[0073] In addition to adjusting Ni 2+ Co 2+ Fe 3+ Except for the molar ratio of 1:0.3:0.2 (which exceeds the molar ratio range defined by this invention), the other raw materials, process parameters, and preparation steps are completely consistent with those in Example 1. Ni-Co-Fe oxide / carbon composite catalyst powder was prepared and coated according to the same process, and its performance was tested simultaneously.

[0074] Performance testing: Under the same operating conditions, the OER overpotential of the coating is 312mV; the decay rate of the 1000h stability test is 0.049mV / h, which cannot form an effective trimetallic synergistic catalytic effect, proving that the metal ion molar ratio specified in this invention is the core condition for achieving high catalytic activity.

[0075] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for preparing an anode catalytic coating for water electrolysis based on waste lithium batteries, characterized in that, Includes the following steps: (1) Solid waste raw material pretreatment: Collect retired or discarded lithium battery cathode materials, remove aluminum foil current collectors and binders, crush into powder, and obtain pretreated cathode powder; (2) Metal ion leaching and recovery: The pretreated cathode powder and sulfuric acid solution are mixed and stirred at a solid-liquid ratio of 1:8-1:15 to leach Ni. 2+ Co 2+ Fe 3+ After filtration, Ni-containing 2+ Co 2+ Fe 3+ The leachate, while simultaneously recovering Li from the filtrate. + And prepare lithium carbonate byproduct; (3) Preparation of catalytic precursor: Add biomass carbon source to leachate and adjust Ni 2+ Co 2+ Fe 3+ The molar ratio of the two components was 1:(0.6-1.0):(0.4-0.6), resulting in a catalytic precursor solution. (4) Low-temperature hydrothermal-carbonization composite: The catalyst precursor solution is transferred to the reactor for hydrothermal reaction, and then carbonized in a nitrogen atmosphere to obtain Ni-Co-Fe oxide / carbon composite catalyst powder; (5) Coating preparation and environmental protection treatment: The catalyst powder and binder are mixed to form a slurry, which is then coated onto the surface of the conductive substrate by electrochemical deposition or spraying. After drying, the anodic catalytic coating is obtained. At the same time, the acidic wastewater generated during the acid leaching process is neutralized and flocculated before being discharged in compliance with standards.

2. The preparation method according to claim 1, characterized in that, In step (1), the lithium battery cathode material is pulverized to 80-120 mesh; in step (2), the concentration of the sulfuric acid solution is 2-6 mol / L, and the pretreated cathode powder is mixed with the sulfuric acid solution and stirred at 50-80℃ for 2-4 h; in step (4), the catalyst precursor solution is transferred to a reaction vessel and hydrothermally reacted at 100-160℃ for 8-12 h, and then carbonized at 300-400℃ for 2-3 h under a nitrogen atmosphere.

3. The preparation method according to claim 1, characterized in that, The retired or discarded lithium battery cathode material is selected from one of the following options: (a) Lithium nickel cobalt manganese oxide battery + lithium iron phosphate battery; (b) Lithium cobalt oxide battery + lithium iron phosphate battery + nickel-containing waste; (c) Lithium nickel cobalt aluminum oxide battery + lithium iron phosphate battery; (d) Mixed types of waste batteries are tested and the ratio of each type of battery is adjusted to achieve the target molar ratio; The sources of Fe, Co, and Ni include, but are not limited to, waste battery cathode materials, battery steel casing acid leaching solutions, or industrial waste.

4. The preparation method according to claim 1, characterized in that, The biomass carbon source is one or more of glucose, sucrose, starch, straw charcoal, wood chip charcoal, or food waste, and the mass ratio of the biomass carbon source to the total mass of metal ions in the leachate is (0.8-1.2):

1. The total molar content of Mn, Al, and Li impurities in the catalytic coating does not exceed 10% of the total molar content of Fe-Co-Ni. The conductive substrate is one of nickel mesh, nickel foam, titanium mesh, or conductive carbon cloth, and the specific surface area of ​​the substrate is ≥100 cm². 2 / g.

5. The preparation method according to claim 1, characterized in that, In step (2), Li + The recovery method is as follows: add sodium carbonate solution to the leachate filtrate, adjust the pH to 8-9, precipitate to obtain lithium carbonate precursor, and obtain industrial grade lithium carbonate after filtration, washing and drying. In step (4), the low-temperature hydrothermal-carbonization composite process is as follows: the catalyst precursor solution is transferred to the reactor and hydrothermally reacted at 100-160℃ for 8-12h, and then carbonized at 300-400℃ for 2-3h under a nitrogen atmosphere to obtain Ni-Co-Fe oxide / carbon composite catalyst powder.

6. The preparation method according to claim 1, characterized in that, In step (5), the treatment method for acidic wastewater is as follows: add calcium hydroxide solution to the acidic wastewater to neutralize it to pH=6-8, add polyacrylamide flocculant to precipitate impurities, filter and discharge the clear liquid after it meets the standards, and use the filter residue as a resource for building materials.

7. The preparation method according to claim 6, characterized in that, The preparation method of the slurry in step (5) is as follows: the catalyst powder and polyvinylidene fluoride are mixed at a mass ratio of 9:1, N-methylpyrrolidone is added to make a slurry with a solid content of 20%-30%, and ultrasonically dispersed for 30-60 min; The electrochemical deposition process parameters are: current density 10-30 mA / cm², deposition time 20-40 min, and deposition temperature room temperature; The process parameters for the spraying method are: spraying pressure 0.3-0.5MPa, spraying distance 15-25cm, and spraying times 3-5 times.

8. The preparation method according to claim 1, characterized in that, The Ni-Co-Fe oxide / carbon composite catalyst has a particle size of 40-220 nm, a specific surface area of ​​≥80 m² / g, and a pore volume of 0.2-0.4 cm³ / g.

9. A catalytic coating for an anode of water electrolysis based on waste lithium batteries, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

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