Method for recycling waste lithium iron phosphate positive electrode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium element

Abstract

The present invention relates to a method for recycling waste lithium iron phosphate positive electrode powder for preparing a high-performance water electrolysis anode catalyst and extracting lithium elements, comprising the following steps: disassembling waste lithium iron phosphate batteries, peeling the positive electrode sheet from the current collector and grinding it; and coating the surface of the obtained lithium iron phosphate powder with a modified nickel compound. The obtained material is immersed in an oxidizing solution to leach the remaining lithium in the material, and the delithiated composite catalyst powder is collected. The lithium ion-containing soaking solution is further recrystallized to precipitate into lithium salts, thereby achieving lithium extraction. Compared with the prior art, the present invention achieves efficient lithium iron phosphate recovery and reuse, and the obtained composite structure catalyst has a significantly improved effect on the oxygen evolution reaction in water electrolysis than waste lithium iron phosphate powder, and its performance is superior to that of commercial Raney nickel electrocatalysts. In addition, compared with directly extracting lithium from waste lithium iron phosphate powder and then coating it with nickel compound, the composite structure catalyst of the present invention has better catalytic performance for the oxygen evolution reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery recycling, and in particular to a method for recycling waste lithium iron phosphate positive electrode powder for preparing a high-performance water electrolysis anode catalyst and extracting lithium elements. Background Art

[0002] Research on renewable and clean energy sources has attracted considerable attention. Lithium-ion batteries, with their high energy density and long cycle life, are widely used in electric vehicles and energy storage systems. However, with the increasing popularity and upgrading of lithium-ion batteries, the disposal and recycling of used batteries have become increasingly problematic. Therefore, there is an urgent need to develop an efficient and environmentally friendly method for recycling lithium-phosphorus batteries to address environmental issues, recover elemental resources, and achieve efficient utilization of recycled products.

[0003] Due to the high overlap in transition metal elements between lithium batteries and catalysts for the oxygen evolution reaction (ORE) in water electrolysis, recycling of used lithium batteries is promising for extracting and utilizing the transition metals they contain to produce highly efficient electrocatalysts. In recent years, the technology for producing hydrogen from water electrolysis using renewable electricity (such as wind power and photovoltaics) has rapidly developed. This technology not only addresses the intermittent and regional nature of renewable energy but also promises to enable distributed hydrogen production in the future. However, the overall efficiency of water electrolysis is limited by the efficiency of the anodic oxygen evolution reaction (ORE) in water electrolysis, which has slow kinetics and requires efficient catalysts to reduce the reaction energy barrier. Currently, precious metal catalysts such as iridium dioxide are considered highly efficient ORE catalysts, but their high price contributes to the high cost of hydrogen production from water electrolysis. Transition metal catalysts, which combine abundant reserves, low cost, and high catalytic performance, have attracted considerable attention in recent years. Recycling transition metal compounds from lithium batteries and further preparing electrocatalysts has the potential to simultaneously address the disposal and recycling issues of used batteries and the high cost of water electrolysis.

[0004] Currently, lithium iron phosphate batteries are a common type of battery among waste batteries, occupying a significant share of the lithium-ion battery market and have been widely used in electric vehicles, energy storage systems and other fields. The positive electrode materials of lithium iron phosphate batteries often contain abundant resources of elements such as iron and phosphorus. Through effective recycling and reuse, the positive electrode materials in waste lithium iron phosphate batteries can be processed to prepare efficient water electrolysis catalysts. For example, CN113355690A discloses a method for large-scale preparation of efficient water electrolysis catalysts using waste lithium-ion battery positive electrode materials, and CN111659399A discloses a method for preparing efficient oxygen evolution catalysts using waste lithium iron phosphate battery positive electrode materials. This opens up new avenues for the recycling and reuse of waste lithium iron phosphate batteries, while promoting the innovation and application of electrochemical catalytic materials and the development of clean energy technologies, contributing to sustainable development and environmental protection.

[0005] Existing research on recycling waste lithium iron phosphate cathode materials for the preparation of oxygen evolution catalysts still mainly focuses on the following two aspects: First, it focuses on the synthesis of composite structures of waste lithium iron phosphate cathode powders (such as the LiFePO4@Ni(OH)2 heterogeneous composite catalyst material disclosed in CN113355690A). However, little attention has been paid to the rational utilization of residual lithium in waste lithium iron phosphate cathode materials. The high-value element in waste lithium iron phosphate cathode materials is mainly lithium, and lithium is generally not used as an active metal site for the oxygen evolution reaction. Whether lithium can be pre-extracted from the catalyst structure still lacks corresponding attention. Second, existing research on recycling waste lithium iron phosphate cathode materials for the preparation of oxygen evolution catalysts focuses on directly destroying the structure of lithium iron phosphate materials, such as using strong acid reagents to dissolve the transition metal element iron in lithium iron phosphate, and then further inputting the dissolved iron-containing components as raw materials into the synthesis of oxygen evolution catalysts (such as a method disclosed in CN111659399A). However, the above method involves the use of strong acid reagents, which is not environmentally friendly and involves an additional step of destroying the lithium iron phosphate structure.

[0006] Therefore, there is an urgent need for a method that can effectively recover lithium from waste batteries and further enhance the catalytic performance of the composite catalyst for the oxygen evolution reaction. Summary of the Invention

[0007] The present invention aims to provide a method for recycling waste lithium iron phosphate cathode powder for use in preparing high-performance water electrolysis anode catalysts and extracting lithium. By recycling retired lithium iron phosphate battery cathode materials and coating and modifying them with nickel oxide, nickel sulfide, nickel selenide, nickel phosphide, or nickel nitride, and then leaching lithium, a highly efficient oxygen evolution reaction composite catalyst is prepared and elemental lithium is extracted from the waste lithium iron phosphate cathode. This method allows for the efficient recycling and reuse of waste lithium iron phosphate batteries at a low cost.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] The object of the present invention is to provide a method for recycling waste lithium iron phosphate positive electrode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium element, the method comprising the following steps:

[0010] (1) obtaining a positive electrode sheet from a recycled waste lithium iron phosphate power battery, separating the positive electrode material and the current collector in the positive electrode sheet, preparing the obtained positive electrode material into a positive electrode material powder, and recovering the retired lithium iron phosphate powder from the obtained positive electrode material powder;

[0011] (2) mixing the retired lithium iron phosphate powder recovered in step (1) with the nickelide-coated raw material to react and obtain a composite structure of nickelide-coated lithium iron phosphate material;

[0012] ((3) Soaking the composite structure of the nickelide-coated lithium iron phosphate material obtained in step (2) in an oxidizing solvent to dissolve the remaining lithium ions in the composite structure of the nickelide-coated lithium iron phosphate material, and separating the required electrolytic water oxygen evolution reaction catalyst from the soaking solution; the soaking solution containing lithium ions is further recrystallized to precipitate into lithium salts, and the lithium element is extracted.

[0013] Furthermore, the method comprises the following steps:

[0014] (1) Pretreatment step: After fully discharging the recycled lithium iron phosphate power battery, disassemble it and use an organic solvent to clean the side reaction products and residual lithium salt electrolyte on the surface of the positive electrode to obtain the positive electrode sheet. Separate the positive electrode material and the current collector by hot water immersion or other methods, and dry and grind the obtained positive electrode material into powder. After collecting the positive electrode material powder, wash it with an organic solvent and dry it to obtain the retired lithium iron phosphate powder.

[0015] (2) The steps of preparing the nickelide-coated retired lithium iron phosphate composite material include mixing the recovered lithium iron phosphate and the coating raw material to react, and after the reaction is completed, obtaining a composite structure of the nickelide-coated lithium iron phosphate material.

[0016] (3) A lithium ion recovery step, wherein the obtained nickel compound-coated lithium iron phosphate composite structure is immersed in an oxidizing solvent to dissolve the remaining lithium ions in the nickel compound-coated lithium iron phosphate composite structure, and the desired electrolytic water oxygen evolution reaction catalyst composite material is separated from the immersion solution. The lithium ion-containing immersion solution is further recrystallized to precipitate into lithium salts, and the lithium element is extracted.

[0017] (4) Electrode preparation step: the electrolytic water oxygen evolution reaction catalyst composite material, conductive agent, and binder separated in (3) are mixed and evenly dispersed in a solvent to obtain a dispersion liquid, and the dispersion liquid is dropped onto the target electrode to obtain a water electrolysis anode electrode.

[0018] Furthermore, the method comprises the following steps:

[0019] (1) Pretreatment step: After fully discharging the recycled lithium iron phosphate power battery, disassemble it and use dimethyl carbonate, an organic solvent, to clean the side reaction products and residual lithium salt electrolyte on the surface of the positive electrode to obtain the positive electrode. Separate the positive electrode material and the current collector by soaking in hot water, and dry and grind the obtained positive electrode material into powder. After collecting the positive electrode material powder, wash it with an organic solvent such as N-methylpyrrolidone (to remove the binder polyvinylidene fluoride PVDF) and dry it to obtain the retired lithium iron phosphate powder.

[0020] (2) Preparation of nickelide-coated retired lithium iron phosphate composite material, prepared by a one-step hydrothermal / solvothermal method or a two-step method (hydrothermal / solvothermal method plus further high-temperature sulfurization, selenization or phosphating, etc.). The one-step method comprises mixing retired lithium iron phosphate and nickelide coating raw materials (including a nickel source or a nickel source and an anion source) and transferring them to a hydrothermal kettle for reaction, heating to 150-300°C under stirring and reacting for 30-360 minutes to prepare a coating layer on the surface of the lithium iron phosphate, and collecting the product after the reaction, washing, and drying to obtain a nickelide-coated lithium iron phosphate composite material.

[0021] Optionally, the nickel source includes one or more of nickel acetylacetonate, nickel nitrate, nickel sulfate, nickel chloride, etc., the anion source includes one or more of thiourea, sodium thiosulfate, sulfur powder, selenium powder, selenium oxide, ammonium dihydrogen phosphate, phosphorus powder, sodium hypophosphite, etc., and the dispersion includes one or more of mesitylene, dimethylformamide, benzyl alcohol, diethylene glycol, ethanol, water, etc.

[0022] Optionally, the additives include one or more of hexadecylamine, oleic acid, octylamine, oleylamine, didodecylamine, ethylenediaminetetraacetic acid, urea, etc. The two-step method is mainly used to prepare composite materials of retired lithium iron phosphate coated with nickel sulfide, nickel selenide, nickel phosphide, nickel nitride, etc., which specifically includes: first preparing a lithium iron phosphate precursor coated with nickel hydroxide or nickel oxide by hydrothermal / solvothermal method, and then heat-treating the above composite material and one or more anion sources such as selenium powder, sulfur powder, phosphorus powder, sodium hypophosphite, etc. in an inert gas atmosphere (one of argon, nitrogen, etc.). During the heat treatment process, the vacuum degree is controlled to be 0.05-0.01MPa, the heat treatment reaction temperature is 300-500℃, and the heating rate is 1-10℃min -1 The heat preservation time is 30-480 minutes. After cooling, a composite material of nickel sulfide, nickel selenide, nickel phosphide, or nickel nitride coated lithium iron phosphate is obtained.

[0023] (3) Lithium ion recovery step: using a chemical soaking method, the obtained lithium iron phosphate composite material modified with a nickel-based compound is soaked in an oxidizing solvent (such as potassium ferrocyanide, sodium persulfate or ferric sulfate solution) whose standard electrode potential exceeds that of lithium iron phosphate, and the remaining lithium ions in the material are leached. After sufficient soaking, the solid precipitate in the soaking liquid is centrifuged and separated. The collected solid precipitate is further washed and dried to obtain the required composite structure electrolysis water oxygen evolution reaction catalyst composite material. The lithium ion-containing soaking liquid is evaporated and concentrated to increase the concentration of lithium ions to improve the extraction efficiency of lithium elements. Then, by adding a purifying agent such as sodium hydroxide solution to the solution, the pH value of the solution is adjusted to form a precipitate of impurity metal ions such as iron ions in the solution in the form of hydroxide, and the purified lithium ion-containing soaking liquid is obtained after filtration. The purified lithium ion-containing soaking liquid is further added with a recrystallization additive to react chemically with the lithium ions in the leaching liquid to form a lithium-containing precipitate that is difficult to dissolve in water. The reaction conditions (such as temperature, pH value, stirring speed, etc.) are controlled to ensure that the precipitation reaction is fully carried out. After the precipitation is complete, the lithium-containing precipitate is separated from the mother liquor by filtering, washing, drying and other steps to obtain a crystalline product.

[0024] The pure lithium salt is precipitated by recrystallization. Optionally, the crystallization additive includes sodium carbonate, sodium phosphate and sodium hydroxide, and the crystallization product is lithium carbonate, lithium phosphate or lithium hydroxide.

[0025] Furthermore, after step (3), the following steps are also included:

[0026] (4) The electrolytic water oxygen evolution reaction catalyst composite material, conductive agent, and binder prepared above are mixed and uniformly dispersed in a solvent to obtain a dispersion liquid, and the dispersion liquid is dropped onto a target electrode to obtain an electrolytic water anode electrode.

[0027] Furthermore, after step (3), the following steps are also included:

[0028] (4) The electrolytic water oxygen evolution reaction catalyst, conductive agent, and binder obtained in step (3) are mixed and uniformly dispersed in a solvent to obtain a first dispersion liquid, and the first dispersion liquid is dropped onto a target electrode to obtain an electrolytic water anode electrode.

[0029] Furthermore, in step (4), the mass ratio of the catalyst for oxygen evolution reaction by electrolysis of water to the conductive agent is (1:5)-(5:1).

[0030] Furthermore, in step (4), the first dispersion liquid is a mixture of ethanol, water, a binder (such as Nafion (wt 5%) solution, polytetrafluoroethylene (PTFE), etc.), etc.

[0031] Furthermore, in step (4), the solvent is a mixed solvent of water and ethanol.

[0032] Furthermore, in step (4), the volume ratio of water, ethanol and binder is 3:1:(0.2-0.4).

[0033] Furthermore, in step (4), the binder is a 5% by weight Nafion solution or polytetrafluoroethylene (PTFE).

[0034] Furthermore, in step (4), the electrode material of the target electrode is nickel foam, carbon paper and glassy carbon electrode, and the catalyst loading amount of the electrolytic water oxygen evolution reaction is 40 to 1000 μg cm -2 .

[0035] Furthermore, step (1) specifically includes the following process:

[0036] The spent lithium iron phosphate power battery after recycling is disassembled after being fully discharged, and the side reaction products and residual lithium salt electrolyte on the surface of the positive electrode are cleaned with an organic solvent to obtain the positive electrode plate;

[0037] Separating the positive electrode material and the current collector in the positive electrode sheet by soaking in hot water, drying the obtained positive electrode material, and grinding it into a positive electrode material powder;

[0038] After collecting the positive electrode material powder, the residual binder in the powder is washed with a second organic solvent and dried to obtain retired lithium iron phosphate powder.

[0039] Furthermore, in step (1), the first organic solvent used to clean the side reaction products and residual lithium salt electrolyte on the surface of the positive electrode is one or more organic electrolytes such as dimethyl carbonate.

[0040] Furthermore, the first organic solvent is preferably dimethyl carbonate.

[0041] Furthermore, in step (1), the second organic solvent used to clean the binder remaining in the positive electrode material powder is N-methylpyrrolidone or the like.

[0042] Furthermore, the second organic solvent is preferably N-methylpyrrolidone.

[0043] Furthermore, in step (1), the conditions for hot water soaking are: the hot water temperature range is 95-100° C., and the time is 1 to 5 minutes.

[0044] Furthermore, in step (2), the composite structure of the nickelide-coated lithium iron phosphate material includes lithium iron phosphate particles and a coating layer coating the lithium iron phosphate particles, the thickness of the coating layer is within 1 / 5 of the size / diameter of the lithium iron phosphate particles, and the coating layer material is one or more of nickel oxide, nickel hydroxide, nickel sulfide, nickel selenide, nickel phosphide, and nickel nitride.

[0045] Furthermore, in step (2), the composite structure of the nickelide-coated lithium iron phosphate material is prepared by a one-step hydrothermal / solvothermal method or a two-step method (hydrothermal / solvothermal method plus further high-temperature sulfurization, selenization or phosphating).

[0046] Furthermore, the one-step hydrothermal / solvothermal method comprises the following steps: dispersing lithium iron phosphate and nickel-coated raw materials in a solvent (such as mesitylene) for hydrothermal or solvothermal reaction to obtain a second dispersion, heating the second dispersion to 150-300°C at a heating rate of 1-10°C / min -1 , the reaction temperature is 150-300°C, the reaction time is 30-360min, and the stirring speed is 200-800rpm to obtain a composite structure of nickelide-coated lithium iron phosphate material.

[0047] Optionally, when synthesizing nickel oxide or nickel hydroxide, in the one-step hydrothermal / solvothermal method, the nickel compound coating raw material includes a nickel source.

[0048] Optionally, when synthesizing nickel sulfide, nickel selenide, nickel phosphide, or nickel nitride, in the one-step hydrothermal / solvothermal method, the nickelide coating raw material includes a nickel source and an anion source.

[0049] Furthermore, lithium iron phosphate and nickel-coated raw materials (including a nickel source, or a nickel source and an anion source) are dispersed in a hydrothermal / solvothermal solvent used for a hydrothermal or solvothermal reaction. Specifically, if nickel oxide or nickel hydroxide is synthesized, no additional anion source is required; however, if nickel sulfide, nickel selenide, nickel phosphide, or nickel nitride is synthesized, an anion source needs to be added.

[0050] Furthermore, the nickel source in the one-step hydrothermal / solvothermal method includes one or more of nickel acetylacetonate, nickel nitrate, nickel chloride, nickel acetate, and nickel sulfate.

[0051] Furthermore, the anion source in the one-step hydrothermal / solvothermal method includes one or more of thiourea, sodium thiosulfate, sulfur powder, selenium powder, selenium oxide, ammonium dihydrogen phosphate, phosphorus powder, sodium hypophosphite, etc.

[0052] Furthermore, the one-step hydrothermal / solvothermal method includes the following steps: dispersing lithium iron phosphate, nickel compound coating raw materials and additives in a solvent (such as mesitylene) used for hydrothermal or solvothermal reaction to obtain a second dispersion.

[0053] Furthermore, in the one-step hydrothermal / solvothermal method, optional additives include one or more of hexadecylamine, oleic acid, octylamine, oleylamine, didodecylamine, ethylenediaminetetraacetic acid, urea, etc., which are used to adjust the reaction environment.

[0054] Furthermore, the two-step method comprises the following steps:

[0055] (2-1) dispersing lithium iron phosphate and a nickel-coated raw material in a hydrothermal / solvothermal solvent to obtain a third dispersion, and preparing a lithium iron phosphate precursor coated with nickel hydroxide or nickel oxide by a hydrothermal / solvothermal method;

[0056] (2-2) The anion source and the lithium iron phosphate precursor are heat-treated in an inert gas atmosphere, and after cooling, a composite structure of nickelide-coated lithium iron phosphate material is obtained.

[0057] Furthermore, the hydrothermal / solvothermal solvent includes one or more of mesitylene, dimethylformamide, benzyl alcohol, diethylene glycol, ethanol, water, and the like.

[0058] Furthermore, the nickelide coating raw material in the two-step method includes a nickel source.

[0059] Furthermore, the nickel source in the two-step method includes one or more of nickel acetylacetonate, nickel nitrate, nickel chloride, nickel acetate, nickel sulfate, and the like.

[0060] Furthermore, the anion source in the two-step method includes one or more of selenium powder, sulfur powder, phosphorus powder, sodium hypophosphite, etc.

[0061] Furthermore, in the two-step method, the mass ratio of the lithium iron phosphate precursor to the anion source is (1:0.1)-(1:2).

[0062] Furthermore, the inert gas in the two-step method includes one of argon, nitrogen, etc.

[0063] Furthermore, the process of step (2-1) is as follows: an additive, lithium iron phosphate, and a nickelide coating raw material are dispersed in a hydrothermal / solvothermal solvent to obtain a third dispersion, and a lithium iron phosphate precursor coated with nickel hydroxide or nickel oxide is prepared by a hydrothermal / solvothermal method. The hydrothermal / solvothermal solvent provides the solvent environment for coating, and the additive provides the pH environment for hydrolysis.

[0064] Furthermore, in step (2-1), the conditions for preparing the lithium iron phosphate precursor coated with nickel hydroxide or nickel oxide by hydrothermal / solvothermal method are as follows: the third dispersion is heated to 150-300°C at a heating rate of 1-10°C min -1 The reaction temperature is 150-300° C., the reaction time is 30-360 min, and the stirring speed is 200-800 rpm to obtain a lithium iron phosphate precursor coated with nickel hydroxide or nickel oxide.

[0065] Furthermore, in step (2-1), optional additives include one or more of hexadecylamine, oleic acid, octylamine, oleylamine, didodecylamine, ethylenediaminetetraacetic acid, urea, etc., for adjusting the reaction environment.

[0066] Furthermore, during the heat treatment process, the vacuum degree is controlled at 0.05-0.01 MPa, the heat treatment reaction temperature is 200-500°C, and the heating rate is 1-10°C min -1 , the insulation time is 30-480 minutes.

[0067] Furthermore, in step (3), the optional oxidizing solvent is a solution having a standard electrode potential exceeding that of lithium iron phosphate, such as a potassium ferrocyanide solution. The standard electrode potential, sometimes also called the equilibrium electrode potential, reflects the redox ability of a substance.

[0068] Furthermore, in step (3), the recrystallization additive is one or more of carbonates, hydroxides, and sulfates.

[0069] Furthermore, step (3) specifically includes the following steps:

[0070] The composite structure of the nickel compound-coated lithium iron phosphate material is immersed in an oxidizing solvent to dissolve the remaining lithium ions in the composite structure of the nickel compound-coated lithium iron phosphate material. After sufficient reaction, the desired delithiated water electrolysis oxygen evolution reaction catalyst solid is separated from the immersion solution by centrifugation;

[0071] The collected lithium ion-containing soaking solution is evaporated and concentrated to improve the efficiency of lithium element extraction, and then a purifying agent is added to the solution to adjust the pH value of the solution so that the impure metal ions are precipitated in the form of hydroxide and filtered.

[0072] A recrystallization additive is added to the purified lithium-ion-containing soaking solution to precipitate the lithium ions into lithium salts, thereby extracting the lithium element. The recrystallization additive reacts chemically with the lithium ions in the solution to form a lithium-containing precipitate that is insoluble in water. After filtration, the lithium-containing recrystallized product is obtained.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] (1) The present invention provides a new, simple, low-cost, and minimally intensive battery material recycling method that eliminates the need for long-term, high-temperature pyrometallurgical reactions and the use of large amounts of acid and alkali reagents in hydrometallurgical processes. Furthermore, the hot water immersion method for separating lithium iron phosphate and the current collector does not generate waste liquid, making it a low-cost, low-energy, and green recycling method that reduces environmental pollution from waste lithium iron phosphate batteries.

[0075] (2) The method provided by the present invention can recycle and reuse the lithium, iron, and phosphorus elements in the positive electrode lithium iron phosphate, avoiding the energy consumption of repeated mining and saving resources. The composite structure catalyst finally obtained has a significantly improved effect on the catalytic oxygen evolution reaction in water electrolysis compared with retired lithium iron phosphate powder, and its performance is better than that of commercial Raney nickel electrocatalysts. It has more excellent water electrolysis catalytic properties and stability, can effectively improve the efficiency of the oxygen evolution reaction, and is easy to operate and scale production, significantly improving the economic benefits of recycling waste lithium iron phosphate batteries.

[0076] (3) By performing catalyst preparation and lithium extraction in the same process, the present invention not only achieves high performance of the anode catalyst for water electrolysis, but also extracts high-value lithium from waste lithium iron phosphate batteries, thereby obtaining high-value, high-quality pure lithium compounds. This achieves comprehensive resource utilization and efficient energy conversion, and has important economic and environmental significance.

[0077] (4) The method provided by the present invention not only extracts the high-value element lithium from the waste lithium iron phosphate cathode, but also utilizes the leaching effect of lithium from the composite structure of the nickel-coated lithium iron phosphate material to significantly enhance the catalytic performance of the composite catalyst for the oxygen evolution reaction. The composite catalyst obtained by the method provided by the present invention (compared to the method of directly extracting lithium from the waste lithium iron phosphate cathode and then coating it with nickel) has significantly improved oxygen evolution catalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 Transmission electron micrographs of the retired lithium iron phosphate composite material of s-LFP@NiO modified nickel oxide prepared in Example 1 of the present invention, including: (a) TEM image of a single s-LFP@NiO particle, and (b) an enlarged image of the heterojunction structure at the edge of the s-LFP@NiO particle and its lattice fringes.

[0079] Figure 2 These are the SEM images and element mapping diagrams of the s-LFP@NiO-PL composite catalyst prepared in Example 1 of the present invention, where (a) and (b) are SEM images of the s-LFP@NiO-PL composite catalyst at different magnifications, (c) SEM image of the s-LFP@NiO-PL energy spectrum element mapping area, (d) Ni element analysis diagram, (e) Fe element analysis diagram, and (f) P element analysis diagram.

[0080] Figure 3 This is a graph showing the oxygen evolution reaction performance of the s-LFP@NiO-PL composite catalyst prepared in Example 1 of the present invention loaded on a glassy carbon electrode, the s-LFP catalyst prepared in Comparative Example 1 loaded on a glassy carbon electrode, and the s-FP@NiO composite catalyst prepared in Comparative Example 2 loaded on a glassy carbon electrode after cyclic voltammetry scanning and stabilization.

[0081] Figure 4 This is a performance diagram of oxygen evolution reaction after cyclic voltammetry scanning and stabilization of the s-LFP@NiO-PL composite catalyst prepared in Example 1 of the present invention loaded on a nickel foam electrode, a Raney nickel catalyst loaded on a nickel foam electrode, and a blank nickel foam electrode. DETAILED DESCRIPTION

[0082] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operating process. However, the scope of protection of the present invention is not limited to the following embodiments. It should be understood that the accompanying drawings and the following embodiments are only used to illustrate the present invention, not to limit the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0083] Any value in the numerical range disclosed in the present invention is not limited to the exact range or value. These ranges or values ​​should be understood to include values ​​close to these ranges or values. The endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges. These numerical ranges should be regarded as specifically disclosed in the present invention.

[0084] The preparation methods, materials, structures or composition ratios that are not clearly described in this technical solution are deemed to be common technical features disclosed in the prior art.

[0085] For steps where no conditions are specified, conventional procedures will be followed. The reagents and instruments used are commonly available and readily available in the market, and the technical terminology employed conforms to general standards in the field.

[0086] The present invention provides a method for recycling waste lithium iron phosphate positive electrode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium elements, comprising the following steps: disassembling waste lithium iron phosphate power batteries, peeling the positive electrode plate from the current collector to obtain positive electrode black powder, further grinding the dried positive electrode lithium iron phosphate black powder; and coating the surface of the obtained lithium iron phosphate powder with a modified nickel compound. The obtained material is immersed in an oxidizing solution to leach the remaining lithium in the material, and the composite catalyst powder after delithiation is collected. The present invention achieves efficient lithium iron phosphate recovery and reuse, and the obtained composite structure catalyst has a significantly improved effect on catalyzing the oxygen evolution reaction in water electrolysis than waste lithium iron phosphate powder, and its performance is better than that of commercial Raney nickel electrocatalysts. In addition, compared with directly extracting lithium from waste lithium iron phosphate powder and then coating it with nickel compound, the composite structure catalyst of the present invention has better catalytic performance for the oxygen evolution reaction.

[0087] The present invention provides a method for simultaneously recovering waste lithium iron phosphate positive electrode materials for use in preparing composite catalysts for the anode side (oxygen evolution reaction) of water electrolysis, and for efficiently extracting residual elemental lithium from waste lithium iron phosphate. The process comprises the following steps: Step 1: Dismantling waste lithium iron phosphate power batteries, cleaning the surface of the electrode plates from side reaction products and lithium salts to obtain positive electrode plates, separating them from the current collector, and grinding the resulting dried positive electrode material lithium iron phosphate powder; Step 2: Coating the obtained lithium iron phosphate powder with a modified nickel compound, including one or more of nickel oxide, nickel hydroxide, nickel sulfide, nickel selenide, nickel phosphide, and nickel nitride, to obtain a lithium iron phosphate composite material coated with a modified nickel-based compound. Step 3: Soaking the obtained material in an oxidizing solution to leach the remaining lithium from the material, further extracting it as lithium salts, and simultaneously collecting the delithiated composite catalyst powder. Step 4: Mixing the obtained composite catalyst, conductive agent, and binder, uniformly dispersing them in a solvent to obtain a dispersion, and dropwise adding the dispersion onto the target electrode to obtain a water electrolysis anode electrode. The present invention realizes efficient recovery and reuse of lithium iron phosphate and effective recycling of resources. The obtained composite structure catalyst has a significantly improved effect on catalyzing the oxygen evolution reaction of electrolyzed water compared with waste lithium iron phosphate powder, and its performance is better than that of commercial Raney nickel electrocatalyst.

[0088] A method for recycling waste lithium iron phosphate positive electrode material to prepare a composite catalyst for the anode side of water electrolysis (oxygen evolution reaction), comprising the following steps:

[0089] First, after fully discharging the recycled lithium iron phosphate batteries, they are disassembled. Dimethyl carbonate is used to clean the surface of the positive electrode sheets, removing side reaction products and the lithium salt electrolyte. The resulting positive electrode sheets are then immersed in hot water at 95-99°C. After 10 seconds, the positive electrode material is manually peeled off and collected from the aluminum foil using a fixture. Residual polyvinylidene fluoride (PVDF) in the positive electrode material is then washed with N-methylpyrrolidone (NMP). After drying and grinding, the decommissioned lithium iron phosphate powder (s-LFP) is obtained. Hot water immersion is used because it can cause the binder PVDF to phase separate, reducing its viscosity. NMP is also commonly used to dissolve PVDF, thereby separating the active material from the positive electrode sheets. However, NMP is very expensive and requires solvent post-processing, resulting in negative economic and environmental impacts. In comparison, the 10-second hot water immersion followed by manual separation method offers the advantages of faster processing time and lower costs, making it more suitable for industrial waste battery recycling.

[0090] The nickel compound coating adopts a one-step solvent thermal method. 60mg of retired lithium iron phosphate (s-LFP) nanoparticles, 160mg of nickel acetylacetonate and 480mg of hexadecylamine are added to 16mL of mesitylene. After the mixture is ultrasonically treated for 20 minutes, the obtained uniform colloidal suspension is transferred to a 50mL hydrothermal reactor and solvent thermally reacted at a temperature of 150-200℃ for 1-4 hours. After the reaction is completed and cooled to room temperature, the turbid liquid is washed with ethanol and water, centrifuged, and the precipitate is collected and repeated several times. The collected product is dried in a vacuum oven to obtain a black s-LFP@NiO modified nickel oxide lithium iron phosphate composite material.

[0091] Furthermore, the remaining lithium ions in the product are recovered by chemical immersion. 20 mg of the obtained s-LFP@NiO modified nickel-based compound lithium iron phosphate composite material is immersed in 50 mL of an oxidizing solvent such as a 0.2 M potassium ferrocyanide solution and allowed to stand for 24 hours for full reaction. Through the redox reaction, the remaining lithium ions in the leached material enter the solution. The precipitated product is washed with water, centrifuged, and repeatedly collected. After drying, the precipitated product obtains a black s-LFP@NiO-PL delithiation composite catalyst powder. PL refers to the use of a pre-leaching chemical method to pre-leach the lithium ions in the material to obtain the required electrolytic water oxygen evolution reaction catalyst. The lithium-containing solution obtained by evaporation and concentration makes the concentration of lithium element reach 40 g L -1 To improve the subsequent extraction efficiency of lithium elements. Then add 2 mol L -1 Adjust the pH value of the solution to 7-8 with sodium hydroxide solution to precipitate the impurity metal ions. After filtering the precipitate, add 1-5 mL min -1 Saturated sodium carbonate solution is added at a rate to react with lithium ions to form lithium carbonate precipitate. The solution is stirred continuously at 300 rpm and maintained at 95°C for 2 hours. The resulting lithium carbonate precipitate is filtered, washed, and dried, completing the extraction of the lithium element.

[0092] Finally, the s-LFP@NiO-PL composite catalyst, conductive agent, and binder are uniformly dispersed in a solvent to form a dispersion. The mass ratio of catalyst to conductive agent is 1:4-4:1. The dispersion is a mixture of ethanol, water, and Nafion (5% by weight) solution, with a volume ratio of 3:1:0.2-0.4. The dispersion is then dripped onto the target electrode, such as nickel foam, carbon paper, or glassy carbon, to obtain a catalyst loading of 40-1000 μg cm. -2 Anode electrode for water electrolysis.

[0093] The separated spent lithium iron phosphate active material is collected and dried. Specifically, the binder and other impurities on the collected lithium iron phosphate positive electrode material are removed to reduce the impact of the separation process on the lithium iron phosphate sample. The collected lithium iron phosphate is washed with N-methylpyrrolidone (NMP) and centrifuged at 8000 rpm for 8 minutes. This process is repeated three times, and the lithium iron phosphate is dried at 80°C under vacuum for 12 hours.

[0094] s-LFP, nickel acetylacetonate, and hexadecylamine were mixed in mesitylene for a solvothermal reaction. Specifically, nickel salt was introduced to achieve nickel compound coating; hexadecylamine was used as a surfactant and stabilizer, which could be adsorbed on the surface of the nanoparticles to form a protective layer, helping to control the growth of the coating layer and avoid agglomeration; mesitylene was used as a good dispersant to provide a solvent environment, aiming to uniformly disperse the nickel acetylacetonate in the solution. In detail, the concentration of nickel acetylacetonate was 0.02-0.04 mol L -1 ; Hexadecylamine concentration is 0.12-0.14 mol L -1 The liquid-to-solid ratio of the solution to the s-LFP used was 3.5 to 5 L g -1 The concentration of nickel acetylacetonate was set to control the Ni source to achieve a controllable coating amount. The concentration of hexadecylamine and the solid-liquid ratio of s-LFP to trimethylbenzene solution were set to provide a uniform liquid phase environment to ensure sufficient contact between s-LFP powder and nickel acetylacetonate, thereby allowing the solvothermal reaction to proceed fully.

[0095] The hydrothermal reaction is carried out at a temperature of 150-200 ° C for 1-4 hours, with a heating rate of 5-10 ° C min -1 After the reaction is complete and the mixture is cooled to room temperature, the turbid liquid in the hydrothermal reactor is removed and washed alternately with ethanol and water. Centrifugation is then repeated five times at 9000 rpm for 5 minutes to remove any residual organic liquid and nickel salts on the surface of the s-LFP@NiO. The collected black powder is then dried at room temperature under vacuum for 12 hours to obtain the s-LFP@NiO-modified nickel oxide lithium iron phosphate composite.

[0096] In the lithium ion recovery step, the optional oxidizing solvent is a solution whose standard electrode potential exceeds the standard electrode potential of lithium iron phosphate, such as potassium ferrocyanide. Optionally, the recrystallization additive is one or more of carbonates and hydroxides. The purpose of soaking in the oxidizing solvent is to further leach the residual Li ions in the s-LFP@NiO powder and recover them by recrystallization to improve economic benefits. In addition, the chemical leaching of lithium in the s-LFP@NiO material can simultaneously enhance the oxygen evolution performance of the composite catalyst, thereby obtaining a high-performance, long-term stable electrolytic water oxygen evolution catalyst.

[0097] Example 1

[0098] This embodiment provides a method for recycling waste lithium iron phosphate positive electrode powder for preparing a high-performance water electrolysis anode catalyst and extracting high-value lithium elements, which is used to illustrate the nickel oxide-coated lithium iron phosphate composite structure nanomaterial prepared by the solvothermal method provided by the present invention, comprising the following steps:

[0099] The positive electrode strips of disassembled, self-discharged lithium iron phosphate batteries were cleaned with dimethyl carbonate, cut into 3 cm x 7 cm pieces, and immersed in 95°C hot water for 10 seconds. After that, the positive electrode material was manually peeled off and collected. The separated positive electrode material was then washed with N-methylpyrrolidone to remove any residual PVDF. After drying and grinding, the decommissioned lithium iron phosphate powder (s-LFP) was obtained.

[0100] 60 mg of retired s-LFP nanoparticles (retired lithium iron phosphate powder (s-LFP)), 160 mg of nickel acetylacetonate, and 480 mg of hexadecylamine were added to 16 mL of mesitylene. After ultrasonication for 20 min, the obtained uniform colloidal suspension was transferred to a 50 mL hydrothermal reactor and subjected to solvothermal reaction at 170 °C with a heating rate of 5 °C min -1 The mixture was heated for 60 minutes, then raised to 200°C and held for 75 minutes with stirring at 400 rpm. The precipitate was washed with ethanol and water, centrifuged repeatedly, and dried to obtain a black s-LFP@NiO-modified nickel-based compound-lithium iron phosphate composite (i.e., a composite structure of nickel-compound-coated lithium iron phosphate). The heterojunction components, from the center outward, were lithium iron phosphate (s-LFP) and nickel oxide (NiO). 20 mg of the prepared s-LFP@NiO composite nanostructured material was immersed in 50 mL of 0.2 M potassium ferricyanide solution and allowed to react for 24 hours. The precipitate was washed with water, centrifuged at 8000 rpm, and dried to obtain a black s-LFP@NiO-PL composite catalyst, which was used as a catalyst for oxygen evolution in water electrolysis. The components of the s-LFP@NiO-PL composite catalyst, from the center outward, were FePO4 and NiO.

[0101] The lithium-containing solution obtained by evaporation and concentration (the supernatant obtained after centrifugation) was concentrated to a lithium concentration of 40 g L -1 To improve the subsequent extraction efficiency of lithium elements. Then add 2 mol L -1 Adjust the pH value of the solution to 7-8 with sodium hydroxide solution to precipitate the impurity metal ions. After filtering the precipitate, add 1-5 mL min -1Saturated sodium carbonate solution is added at a rate to react with lithium ions to form lithium carbonate precipitate. The solution is stirred continuously at 300 rpm and maintained at 95°C for 2 hours. The resulting lithium carbonate precipitate is filtered, washed, and dried, completing the extraction of the lithium element.

[0102] Electrode Preparation: The obtained s-LFP@NiO-PL composite catalyst, conductive agent Vulcan Carbon (purchased from CABOT, model XC-72), and binder (Nafion (wt 5%)) were mixed and uniformly dispersed in a solvent to obtain a dispersion. The mass ratio of catalyst to conductive agent was 4:1. The dispersion was a mixture of ethanol, water, and Nafion (wt 5%) solutions. The volume ratio of ethanol, water, and Nafion (wt 5%) was 3:1:0.2. The solid-liquid ratio of the obtained dispersion was 3.75 mg mL -1 Furthermore, the dispersion was added dropwise to a surface with an area of ​​0.19625 cm 2 The catalyst loading was 255 μg cm -2 The anode electrode for electrolysis of water. Add the dispersion dropwise to the 0.8*1.8cm 2 The catalyst loading was 1388 μg cm -2 Self-supporting anode electrode for water electrolysis.

[0103] Electrochemical performance test: The prepared glassy carbon working electrode loaded with s-LFP@NiO-PL was assembled into a three-electrode system with a counter electrode (platinum sheet) and a HgO / Hg reference electrode. The assembled three-cell was electrochemically tested using a biologic electrochemical workstation. The voltage applied to the working electrode ranged from 1.1-1.6 V vs. RHE, with a scan rate of 10 mV s -1 , to obtain stable catalytic performance for oxygen evolution reaction in water electrolysis. For nickel foam electrodes with larger specific surface area, a larger scanning range is required, and the voltage range applied to the electrode is 1.0-1.7V vs. RHE, with a scanning rate of 10mV s -1 .

[0104] See also Figure 1 (a) and (b) show that a certain amount of the s-LFP@NiO-modified nickel-based compound lithium iron phosphate composite material prepared in Example 1 was weighed and observed under a transmission electron microscope. The obtained s-LFP@NiO-modified nickel-based compound lithium iron phosphate composite material has a size of about 200 nm and a uniform morphology. The coated shell is about 9 nm and is evenly coated on the s-LFP nanoparticles without destroying the overall structure. Figure 1(b) and its illustration show that the components of s-LFP@NiO from the center to the outside are: clear lattice fringes, corresponding to the (200) crystal plane of the core layer LiFePO4, and the outer amorphous NiO shell.

[0105] See also Figure 2 (a) and (b) show that a certain amount of the s-LFP@NiO-PL sample prepared in Example 1 was weighed and observed under a scanning electron microscope. It can be seen that the immersion did not destroy the overall structure of the composite material s-LFP@NiO-PL, and the morphology and size were well maintained. Figure 2 Evenly distributed Ni, Fe, and P elements can be seen in the element energy spectra (d), (e), and (f) corresponding to the (c) region.

[0106] Comparative Example 1

[0107] Retired dry lithium iron phosphate powder s-LFP was obtained according to the operating steps of Example 1. A glassy carbon electrode was prepared using the s-LFP catalyst, and the same catalytic performance test and analysis of water electrolysis and oxygen evolution as in Example 1 were performed.

[0108] Comparative Example 2s-FP@NiO composite catalyst

[0109] This comparative example provides an s-FP@NiO composite catalyst, which is as follows:

[0110] Obtain retired dry lithium iron phosphate powder s-LFP according to the operating steps of Example 1. Soak 100 mg of the obtained s-LFP lithium iron phosphate powder in 50 mL of 0.2 M potassium ferrocyanide solution and let it stand for 24 hours to fully react. Wash with water, centrifuge at a speed of 8000 rpm-10000 rpm, repeatedly collect the precipitated product, and obtain black retired iron phosphate s-FP granular powder after drying. Add 60 mg of retired iron phosphate granular powder (iron phosphate powder (s-FP)), 160 mg of nickel acetylacetonate and 480 mg of hexadecylamine to 16 mL of mesitylene, and transfer the obtained uniform colloidal suspension to a 50 mL hydrothermal reactor after ultrasonication for 20 minutes, and carry out solvent thermal reaction at a temperature of 170 ° C, with a heating rate of 5 ° C min -1 , holding time 60min, then rising to 200℃, holding time 75min, stirring speed 400rpm. Washing with ethanol and water, centrifugation, repeatedly collecting the precipitate product and drying it, a black s-FP@NiO modified nickel-based compound iron phosphate composite material is obtained, and its heterojunction components are iron phosphate s-FP and nickel oxide NiO from the center to the outside. It is used as a catalyst for the electrolysis of water and oxygen evolution reaction. The s-FP@NiO catalyst is used to prepare a glassy carbon electrode, and the same electrolysis of water and oxygen evolution catalytic performance test and analysis as in Example 1 are carried out.

[0111] like Figure 3 As shown in the figure, after the above electrochemical oxygen evolution reaction performance test, the electrochemical CV curves of oxygen evolution reaction under voltage were obtained for Example 1, Comparative Example 1, and Comparative Example 2, where the horizontal axis is voltage and the vertical axis is current density. The s-LFP@NiO-PL composite catalyst material prepared in Example 1 of the present invention has a catalytic oxygen evolution reaction current density of 10 mA cm -2 The required overpotential is about 267mV, and the electrochemical performance is much better than that of the initial material s-LFP. In contrast, the s-FP@NiO composite catalyst in Comparative Example 2 has an oxygen evolution reaction current density of 10mAcm -2 The overpotential required is about 327mV, and the performance is significantly inferior to that of the prepared s-LFP@NiO-PL composite catalyst, indicating that the method provided by the present invention can not only extract the high-value element lithium from the waste lithium iron phosphate positive electrode, but also utilize the leaching effect of lithium from the composite structure of the nickelide-coated lithium iron phosphate material to significantly enhance the catalytic performance of the composite catalyst for the oxygen evolution reaction. Compared with the method of directly extracting lithium from the waste lithium iron phosphate positive electrode and then coating it with nickelide in the comparative example, the method provided by the present invention first recovers the retired lithium iron phosphate battery positive electrode material and coats it with nickelide such as nickel oxide, nickel sulfide, nickel selenide, nickel phosphide, or nickel nitride, and further leaches lithium. The composite catalyst obtained has a significantly improved oxygen evolution catalytic performance.

[0112] like Figure 4 As shown in FIG, the obtained Example 1 is prepared into a porous nickel foam electrode. Nickel foam is the most commonly used self-supporting electrode and is widely used in industrial water electrolysis. Figure 4 As shown, the nickel foam electrode loaded with 2 mg of s-LFP@NiO-PL composite catalyst (s-LEP@NiO-PL / Ni Foam) catalyzed oxygen evolution reaction with a current density of 50 mA cm -2 The required overpotential is 307mV. In comparison, the Raney nickel catalyst is prepared into a porous nickel foam electrode (Rayne Ni / Ni Foam). The commonly used industrial Raney nickel catalyst (Rayne Ni) has a 35-fold catalyst mass loading (70mg cm -2 ), a 450 mV overpotential is required to achieve 50 mA cm -2 In addition, the above electrodes all showed catalytic performance that was significantly better than that of blank nickel foam (NiFoam) electrodes.

[0113] In summary, the present invention provides a novel method for preparing composite structural materials from waste lithium iron phosphate batteries for use as anode catalysts for water electrolysis, which is simple to operate, low in cost, and requires little equipment. By recycling the positive electrode materials of retired lithium iron phosphate batteries, a lithium iron phosphate composite material modified with nickel-based compounds is prepared by adding nickel acetylacetonate, hexadecylamine, and trimethylbenzene using a solvent thermal method to coat nickel oxide on the surface of the lithium iron phosphate. Further, a chemical soaking method is used to leach the remaining lithium ions in the composite structural material, thereby obtaining a highly efficient catalyst for the oxygen evolution reaction in water electrolysis. Waste lithium iron phosphate batteries are processed at a relatively low cost, and efficient recycling and reuse are achieved. Compared with traditional battery material recycling, there is no need for long-term high-temperature pyrometallurgical reactions and the use of large amounts of acid and alkali reagents in hydrometallurgy. It is a low-cost, low-energy, green recycling method that reduces the environmental pollution caused by waste lithium iron phosphate batteries. By preparing a catalyst for the oxygen evolution reaction in water electrolysis, the recycled lithium iron phosphate is utilized, the energy consumption of repeated mining is avoided, and resources are saved. The composite catalyst finally obtained has more excellent catalytic properties and stability in water electrolysis than commercial Raney nickel electrocatalysts, can effectively improve the efficiency of oxygen evolution reaction, is easy to operate and mass-produce, and significantly improves the economic benefits of recycling waste lithium iron phosphate batteries. The present invention achieves catalyst preparation and lithium element extraction at the same time by immersing the obtained material in an oxidizing solution to leach the remaining lithium in the material. The high-value lithium element in the extracted waste lithium iron phosphate batteries is converted into high-value, high-quality pure lithium compounds. Lithium is an important material that is indispensable in current new energy batteries, and its demand is increasing year by year. Through the application of this technical solution, the efficient recovery of the usable lithium resources still contained in waste batteries can be achieved, the utilization rate of resources can be improved, and more raw material support can be provided for the new energy battery industry. This unique method not only improves the economic benefits of waste battery recycling, but also realizes the comprehensive utilization of resources and the efficient conversion of energy, which has important economic and environmental significance.

[0114] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for recycling waste lithium iron phosphate cathode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium element, characterized in that: The method comprises the following steps: (1) obtaining a positive electrode sheet from a recycled waste lithium iron phosphate power battery, separating the positive electrode material and the current collector in the positive electrode sheet, preparing the obtained positive electrode material into a positive electrode material powder, and recovering the retired lithium iron phosphate powder from the obtained positive electrode material powder; (2) mixing the retired lithium iron phosphate powder recovered in step (1) with the nickelide-coated raw material to react and obtain a composite structure of nickelide-coated lithium iron phosphate material; (3) soaking the composite structure of the nickel compound-coated lithium iron phosphate material obtained in step (2) in an oxidizing solvent to dissolve the remaining lithium ions in the composite structure of the nickel compound-coated lithium iron phosphate material, and separating the required electrolytic water oxygen evolution reaction catalyst from the soaking solution; the soaking solution containing lithium ions is further recrystallized to precipitate into lithium salt, and the lithium element is extracted.

2. The method for recycling waste lithium iron phosphate cathode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium according to claim 1, characterized in that: After step (3), the following steps are also included: (4) The electrolytic water oxygen evolution reaction catalyst, conductive agent, and binder obtained in step (3) are mixed and uniformly dispersed in a solvent to obtain a first dispersion liquid, and the first dispersion liquid is dropped onto a target electrode to obtain an electrolytic water anode electrode.

3. The method for recycling waste lithium iron phosphate cathode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium according to claim 1, characterized in that: Step (1) specifically includes the following process: Dismantling the recycled waste lithium iron phosphate power battery after full discharge, and using a first organic solvent to clean the side reaction products and residual lithium salt electrolyte on the surface of the positive electrode to obtain a positive electrode plate; Separating the positive electrode material and the current collector in the positive electrode sheet, drying and grinding the obtained positive electrode material into positive electrode material powder; After collecting the positive electrode material powder, the residual binder in the powder is washed with a second organic solvent and dried to obtain retired lithium iron phosphate powder.

4. The method for recycling waste lithium iron phosphate cathode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium according to claim 1, characterized in that: In step (2), the composite structure of the nickelide-coated lithium iron phosphate material includes lithium iron phosphate particles and a coating layer coating the lithium iron phosphate particles, and the thickness of the coating layer is within 1 / 5 of the diameter of the lithium iron phosphate particles; The coating layer material is one or more of nickel oxide, nickel hydroxide, nickel sulfide, nickel selenide, nickel phosphide and nickel nitride.

5. The method for recycling waste lithium iron phosphate cathode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium according to claim 1, characterized in that: In step (2), the composite structure of the nickel compound-coated lithium iron phosphate material is prepared by a one-step hydrothermal / solvothermal method or a two-step method.

6. The method for recycling waste lithium iron phosphate cathode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium according to claim 5, characterized in that: The one-step hydrothermal / solvothermal method comprises the following steps: dispersing lithium iron phosphate and nickel-coated raw materials in a hydrothermal / solvothermal solvent used for a hydrothermal or solvothermal reaction to obtain a second dispersion, and heating the second dispersion to react to obtain a composite structure of nickel-coated lithium iron phosphate materials; The hydrothermal / solvothermal solvent includes one or more of mesitylene, dimethylformamide, benzyl alcohol, diethylene glycol, ethanol, and water; The nickelide coating raw material includes a nickel source; The nickel source includes one or more of nickel acetylacetonate, nickel nitrate, nickel chloride, nickel acetate, and nickel sulfate; Additives are also dispersed in the hydrothermal / solvothermal solvent used for the hydrothermal or solvothermal reaction, and are used to adjust the reaction environment.

7. The method for recycling waste lithium iron phosphate cathode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium according to claim 6, characterized in that: The nickel compound coating raw material also includes an anion source; The anion source includes one or more of thiourea, sodium thiosulfate, sulfur powder, selenium powder, selenium oxide, ammonium dihydrogen phosphate, phosphorus powder, and sodium hypophosphite.

8. The method for recycling waste lithium iron phosphate cathode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium according to claim 5, characterized in that: The two-step method comprises the following steps: (2-1) dispersing lithium iron phosphate and nickel compound coating raw materials in a hydrothermal / solvothermal solvent, and preparing a lithium iron phosphate precursor coated with nickel hydroxide or nickel oxide by a hydrothermal / solvothermal method; (2-2) heat-treating the anion source and the lithium iron phosphate precursor in an inert gas atmosphere, and obtaining a composite structure of the nickelide-coated lithium iron phosphate material after cooling; In step (2-1), the hydrothermal / solvothermal solvent includes one or more of mesitylene, dimethylformamide, benzyl alcohol, diethylene glycol, ethanol, and water; The nickelide coating raw material includes a nickel source; The nickel source includes one or more of nickel acetylacetonate, nickel nitrate, nickel chloride, nickel acetate, and nickel sulfate; In step (2-2), the anion source includes one or more of selenium powder, sulfur powder, phosphorus powder, and sodium hypophosphite; In step (2-1), additives are further dispersed in the hydrothermal / solvothermal solvent used for the hydrothermal or solvothermal reaction, and the additives are used to adjust the reaction environment.

9. The method for recycling waste lithium iron phosphate cathode powder for preparing high-performance water electrolysis anode catalyst and extracting lithium according to claim 1, characterized in that: In step (3), the oxidizing solvent is a solution having a standard electrode potential exceeding that of lithium iron phosphate; Step (3) specifically includes the following steps: soaking the composite structure of the nickel compound-coated lithium iron phosphate material in an oxidizing solvent to dissolve the remaining lithium ions in the composite structure of the nickel compound-coated lithium iron phosphate material; and after the reaction, centrifugally separating the desired delithiated water electrolysis oxygen evolution reaction catalyst solid from the soaking solution; The collected lithium ion-containing soaking solution is evaporated and concentrated to improve the efficiency of lithium element extraction, and then a purifying agent is added to the solution to adjust the pH value of the solution so that the impurity metal ions are precipitated in the form of hydroxides and filtered to obtain a purified lithium ion-containing soaking solution; A recrystallization additive is added to the purified lithium ion-containing soaking solution to precipitate the lithium ions into lithium salts, thereby achieving the extraction of lithium elements.

Images