Method for preparing high-efficiency water electrolysis oxygen evolution reaction catalyst by modifying waste lithium battery positive electrode black powder based on electrochemical selective delithiation

Abstract

This invention provides a method for modifying spent lithium-ion battery cathode black powder based on electrochemical selective delithiation to prepare a high-efficiency catalyst for the oxygen evolution reaction (OER) in water electrolysis. The method includes the following steps: using spent lithium-ion battery cathode black powder as the anode, selectively leaching lithium ions into the electrolyte through an electrochemical delithiation process to obtain a residual solid powder containing transition metal components after delithiation; subsequently, reacting it with a metal salt solution containing foreign elements under mild conditions, incorporating the foreign elements into the solid structure, thereby obtaining a composite material with high OER catalytic activity, i.e., a high-efficiency catalyst for the OER in water electrolysis. Compared with existing technologies, the method of this invention is simple, has mild reaction conditions, low cost, and is environmentally friendly, achieving high-value-added resource utilization of residual components from spent lithium-ion battery cathode materials.

Description

Technical Field

[0001] This invention relates to the field of lithium battery recycling technology, and in particular to a method for modifying waste lithium battery cathode black powder based on electrochemical selective delithiation for use in preparing a highly efficient catalyst for the oxygen evolution reaction in water electrolysis. Background Technology

[0002] The research and application of renewable and clean energy technologies have attracted much attention. Lithium-ion batteries, with their high energy density and long cycle life, have become the core energy storage device for electric vehicles and large-scale energy storage systems. However, with the widespread adoption and replacement of lithium-ion batteries, the disposal and recycling of used batteries are becoming increasingly prominent issues. Therefore, there is an urgent need to develop efficient and environmentally friendly lithium-ion battery resource recovery technologies that can not only solve solid waste pollution problems and recover lithium and transition metal resources, but also achieve high-value utilization of recycled products.

[0003] Because lithium-ion batteries and oxygen evolution reaction (OER) catalysts in water electrolysis highly overlap in their use of transition metal elements such as iron, cobalt, nickel, and manganese, a new path for the high-value recycling of spent lithium-ion batteries is provided. Specifically, by recovering and extracting transition metal elements from the batteries, highly efficient OER electrocatalysts can be prepared. In recent years, water electrolysis for hydrogen production, relying on renewable electricity from wind and solar power, has developed rapidly. This not only solves the intermittent and geographical limitations of new energy sources but also holds promise for distributed hydrogen production. However, the overall efficiency of water electrolysis is limited by the anodic OER reaction, which has slow kinetics and requires highly efficient catalysts to lower the reaction energy barrier. Currently, while precious metal catalysts such as iridium dioxide exhibit excellent catalytic performance, their high price drives up the cost of hydrogen production from water electrolysis. Transition metal catalysts, on the other hand, combine abundant reserves, low cost, and good catalytic activity, making them a research hotspot in recent years. Recovering transition metal compounds from spent lithium-ion batteries and preparing OER catalysts is expected to simultaneously solve the challenges of spent battery disposal and recycling, as well as the bottleneck of high costs associated with water electrolysis for hydrogen production.

[0004] Currently, research on recycling waste lithium-ion battery cathode materials for the preparation of oxygen evolution reaction catalysts still faces two major shortcomings, and existing technologies have not yet achieved effective breakthroughs.

[0005] Firstly, some research focuses on the synthesis of composite structures for recycled battery substrates, a typical example being the technical solution disclosed in CN113355690A: using waste lithium-ion battery cathode materials as raw materials, a LiFePO4@Ni(OH)2 heterocomposite oxygen evolution reaction catalyst is prepared, and the catalytic activity is improved by constructing a special composite structure. However, this method only focuses on the catalytic modification and optimization of the transition metal matrix, without paying attention to the reasonable recycling and utilization of residual lithium elements in waste battery materials. Lithium, as a high-value element in batteries, usually does not possess catalytic active sites for the oxygen evolution reaction. How to accurately extract lithium resources through pretreatment processes while preserving the catalytic potential of the transition metal matrix remains a relatively scarce area of ​​research and technical design.

[0006] Secondly, existing technologies mostly employ destructive methods to process lithium-ion battery cathode materials. For example, the scheme disclosed in CN116986635A uses waste lithium-ion battery cathode materials as the treatment target, employing sulfuric acid as a leaching agent to dissolve transition metal elements, ultimately only recovering transition metal salts. This type of process not only relies on highly corrosive sulfuric acid reagents, posing significant environmental hazards and operational risks, but also requires additional steps such as structural destruction, leaching solution purification, and metal salt separation, significantly increasing process complexity and production costs. More importantly, it does not provide an effective pathway for the high-value utilization of transition metals, making it difficult to maximize resource value. Furthermore, the insufficient adaptability of green pretreatment technologies further exacerbates the scalability bottleneck of existing processes.

[0007] Therefore, there is an urgent need to develop an integrated technology that combines efficient lithium resource recovery with enhanced catalytic performance. By optimizing the electrochemical delithiation process, precise lithium extraction and preservation of the transition metal matrix structure can be achieved. Simultaneously, modification strategies adapted to the delithiation matrix can be designed to reduce environmental risks and production costs while improving the activity and stability of the oxygen evolution reaction catalyst. Ultimately, this will promote the coordinated development of high-value recycling of spent lithium-ion batteries and clean energy technologies. Summary of the Invention

[0008] The purpose of this invention is to provide a method for modifying spent lithium-ion battery cathode powder based on electrochemical selective delithiation for the preparation of a highly efficient oxygen evolution reaction catalyst in water electrolysis. This method involves extracting lithium from spent lithium-ion battery cathode materials using an electrochemical method and then doping the remaining components with foreign elements to construct a composite oxygen evolution reaction catalyst. Furthermore, this method recovers lithium from the spent cathode material at a low cost and with a simple approach, enabling its reuse in the field of water electrolysis catalysts.

[0009] The objective of this invention can be achieved through the following technical solutions: The first objective of this invention is to provide a method for modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation for the preparation of a highly efficient catalyst for the oxygen evolution reaction in water electrolysis, the method comprising the following steps: Waste lithium battery cathode black powder is used to prepare the anode sheet of an electrochemical delithiation device, and lithium ions in the cathode material are selectively leached into the electrolyte by electrochemical method, resulting in an electrolyte containing lithium ions and residual solid powder containing transition metal components after delithiation. The residual solid powder containing transition metal components after delithiation is dispersed in a metal salt solution containing foreign elements for a simple reaction. After centrifugation to separate the solid, the solid is further washed and dried to obtain a composite water electrolysis oxygen evolution reaction catalyst, which is the high-efficiency water electrolysis oxygen evolution reaction catalyst.

[0010] Furthermore, the method specifically includes the following steps: (1) Electrochemical delithiation step: The waste lithium battery positive electrode black powder is coated on the current collector to prepare the anode plate of the electrochemical delithiation device, and the lithium ions in the positive electrode material are introduced into the solution by applying an electrical signal to obtain an electrolyte containing lithium ions and a delithiated electrode. (2) Modified catalyst preparation steps: Collect the residual solid powder containing transition metal components on the electrode after delithiation, and disperse it in a metal salt solution containing foreign elements. After static or continuous ultrasonic treatment, or stirring or oscillation treatment, after centrifugation to separate the solid, further wash and dry the solid to obtain the modified composite water electrolysis oxygen evolution reaction catalyst, which is the high-efficiency water electrolysis oxygen evolution reaction catalyst. (3) Lithium ion recovery steps: The electrolyte containing lithium ions can be further recrystallized into lithium salts to complete the recovery of lithium elements; (4) Preparation steps of oxygen evolution reaction catalytic electrode: The modified composite water electrolysis oxygen evolution reaction catalyst, conductive agent and binder are mixed and dispersed evenly in a solvent to obtain a dispersion. The dispersion is dropped onto the target electrode to obtain the water electrolysis anode electrode.

[0011] Furthermore, the electrochemical delithiation device includes an electrolytic cell, an anode electrode, and a cathode electrode.

[0012] Furthermore, the anode electrode includes a current collector and an active material coated on the current collector.

[0013] Furthermore, the active material of the anode electrode includes waste lithium battery cathode black powder.

[0014] Furthermore, the cathode electrode is placed on the other side of the anode electrode.

[0015] Furthermore, the cathode electrode of the electrochemical delithiation device is a Pt-based material electrode.

[0016] Furthermore, the electrolytic cell is used to hold the electrolyte for electrochemical delithiation, and the electrolyte is at least one of Na2SO4 aqueous solution, Na2CO3 aqueous solution, NaCl aqueous solution, KCl aqueous solution, K2SO4 aqueous solution, NaNO3 aqueous solution, and KNO3 aqueous solution.

[0017] Furthermore, the concentration of the electrolyte is 0.01~1 mol·L⁻¹. -1 .

[0018] Furthermore, the method for preparing the anode sheet of an electrochemical delithiation device from waste lithium battery cathode black powder includes the following steps: Waste lithium battery cathode black powder, binder, and conductive agent are mixed and then added to a solvent to prepare a slurry. The obtained slurry is loaded onto the current collector with a certain load and then vacuum dried to obtain the coated anode sheet.

[0019] Furthermore, the waste lithium battery cathode black powder is at least one of ternary nickel-cobalt-manganese NCM (such as NCM811, NCM523, NCM622, NCM111, etc.) and lithium cobalt oxide (LCO).

[0020] Furthermore, the adhesive is at least one of polyvinylidene fluoride, polyacrylic acid, styrene-butadiene rubber, sodium carboxymethyl cellulose, and polytetrafluoroethylene.

[0021] Furthermore, the solvent is at least one of N-methylpyrrolidone, water, and alcohol.

[0022] Furthermore, the conductive agent is at least one of acetylene black, conductive carbon black, carbon nanotubes, and graphene.

[0023] Furthermore, the current collector is one of carbon-based materials (such as carbon paper) and other inert conductive substrates.

[0024] Furthermore, the area loading of waste lithium-ion battery cathode black powder coated on the current collector is 1~50 mg·cm³. -2 .

[0025] Furthermore, the mass ratio of the waste lithium battery cathode black powder to the binder is 1:0.1 to 1:0.03.

[0026] Furthermore, the mass ratio of the adhesive to the solvent is 1:10 to 1:40.

[0027] Furthermore, when preparing the slurry, the stirring time is 4~24 h and the stirring speed is 150~450 rpm.

[0028] Furthermore, the thickness of the slurry coated on the current collector is 150~400 μm.

[0029] Furthermore, the vacuum drying temperature of the current collector is 60~120℃, and the time is 8~12 h.

[0030] Furthermore, the electrochemical method includes the following steps: applying an electrical signal between the anode and cathode to achieve an electrochemical delithiation process.

[0031] Furthermore, the electrical signal is applied in one of the following ways: constant voltage, constant current, or alternating constant current and constant voltage.

[0032] Furthermore, a constant voltage method is used: the voltage range is 0.1 V to 4.0 V, and the single delithiation time is 5 to 300 min.

[0033] Furthermore, a constant current method is employed: the current range is 0.1 mA·cm. -2 ~40mA·cm -2 The time for a single delithiation is 5 to 300 minutes.

[0034] Furthermore, an alternating method of constant current and constant voltage is employed: the voltage range during the constant voltage process is 0.1 V to 4.0 V, and the current range during the constant current process is 0.1 mA·cm. -2 ~40mA·cm -2 The time for a single constant voltage delithiation is 5~300 min, and the time for a single constant current delithiation is 5~300 min.

[0035] Furthermore, during the electrochemical delithiation process, the cathode electrode is completely immersed in the electrolyte, and the portion of the anode electrode coated with the active material is also immersed in the electrolyte.

[0036] Furthermore, the electrolyte is stirred during electrochemical delithiation at a stirring rate of 100-800 rpm.

[0037] Furthermore, the temperature for electrochemical delithiation is 10~30℃.

[0038] Furthermore, after completing the electrochemical delithiation, the residual solid powder containing transition metal components after delithiation is collected from the anode plate, and the residual solid powder containing transition metal components after delithiation is placed in an aqueous solution of metal salt containing foreign elements to react and modify the structure.

[0039] Furthermore, the residual solid powder containing transition metal components after delithiation on the anode electrode is collected by one or more methods such as physical scraping and ultrasonic stripping.

[0040] Furthermore, the modified catalyst preparation method described in step (2) specifically includes the following steps: The anode sheet after electrochemical delithiation is collected, and the delithiated active material on the anode sheet is scraped off or peeled off using physical scraping or ultrasonic stripping methods, obtaining the residual solid powder containing transition metal components after delithiation. This powder is then placed in a certain amount of metal salt solution containing foreign elements and subjected to static, continuous ultrasonic, continuous stirring, or continuous oscillation treatment. During this process, the residual solid powder containing transition metal components after delithiation is uniformly dispersed in the metal salt solution containing foreign elements, and the foreign metal ions in the metal salt solution are incorporated into the delithiated solid structure. After element doping, the solid powder and metal salt solution are separated by centrifugation. The doped solid powder is then washed twice with a mixed solution of deionized water and ethanol. After drying, the modified water electrolysis oxygen evolution reaction catalyst, i.e., a high-efficiency water electrolysis oxygen evolution reaction catalyst, is obtained.

[0041] Furthermore, when the waste lithium battery cathode black powder is ternary nickel-cobalt-manganese NCM (such as NCM811, NCM523, NCM622, NCM111, etc.), that is, for waste ternary NCM cathode, the metal salt in the metal salt solution containing foreign elements includes iron-containing soluble compounds. For example, the iron-containing soluble compounds are selected from at least one of inorganic iron salts (such as Fe2(SO4)3, FeCl3, Fe(NO3)3) or organic iron salts (such as iron acetylacetone, iron ammonium citrate, iron oxalate).

[0042] Furthermore, when the waste lithium battery cathode black powder is lithium cobalt oxide (LCO), that is, for waste lithium cobalt oxide (LCO) cathode, the metal salt in the metal salt aqueous solution includes at least one of the following: an inorganic salt containing iron, nickel, or both iron and nickel (such as Fe2(SO4)3, FeCl3, Fe(NO3)3, NiSO4, NiCl2, Ni(NO3)2) or an organic salt containing iron, nickel, or both iron and nickel (such as iron acetylacetonate, nickel acetylacetonate, ferric ammonium citrate, nickel citrate, iron oxalate, nickel oxalate, nickel formate), or a mixture of any of the above salts.

[0043] Furthermore, the solvent in the metal salt solution containing the foreign element, i.e. the reagent for dissolving the metal salt, is a polar solvent, including but not limited to at least one of water, alcohols (such as methanol, ethanol, isopropanol, ethylene glycol), ketones (such as acetone), or other suitable organic solvents (such as tetrahydrofuran, N,N-dimethylformamide).

[0044] Furthermore, the concentration of the metal salt solution containing the foreign element can be adjusted within a wide range, typically 10-50 g / L, but can also be selected outside this range depending on the impregnation requirements and target loading.

[0045] Furthermore, the concentration of the residual solid powder containing transition metal components after delithiation in the metal salt solution containing foreign elements is between 1 and 5 g / L.

[0046] Furthermore, the residual solid powder containing transition metal components after delithiation is dispersed in a metal salt solution containing foreign elements to obtain a mixture. The mixture can be subjected to treatments such as standing, continuous ultrasonication, stirring, or oscillation to modify the waste lithium battery cathode black powder.

[0047] Furthermore, the time for the static, continuous ultrasonic, stirring, or oscillation treatment is 0.1 to 5 hours.

[0048] Furthermore, the frequency of the ultrasonic treatment is 10kHz-100kHz.

[0049] Furthermore, the stirring speed is 100-800 rpm.

[0050] Furthermore, the rotational speed of the oscillation process is 100-200 rpm.

[0051] Furthermore, the centrifugation speed is 5000~8000 rpm, and the time is 5~10 minutes.

[0052] Furthermore, the washing process uses water, ethanol, or a mixture of water and ethanol.

[0053] Furthermore, the drying temperature after washing is 60~80℃, and the time is 2~12h.

[0054] Furthermore, the electrolyte containing lithium ions can be further recrystallized into lithium salt to complete the recovery of lithium.

[0055] Furthermore, the method for further recrystallization (i.e., further precipitation of the electrolyte containing lithium ions into lithium salts) includes the following steps: The collected electrolyte containing lithium ions is evaporated and concentrated to improve the efficiency of lithium extraction. Then, a purifying agent is added to the concentrated solution to adjust the pH value of the solution, so that the impurity metal ions are precipitated in the form of hydroxide precipitates. The hydroxide precipitates are then filtered to obtain the 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, and the crystalline products are separated to achieve the extraction of lithium.

[0056] Furthermore, step (3) involves further precipitating the electrolyte containing lithium ions into lithium salts, specifically including the following steps: The purified lithium-ion-containing leaching solution is further treated with a recrystallization additive, which reacts chemically with the lithium ions in the leaching solution to form a water-insoluble lithium precipitate. Reaction conditions (such as temperature, pH, and stirring speed) are controlled to ensure the precipitation reaction proceeds fully. After complete precipitation, the lithium precipitate is separated from the mother liquor through filtration, washing, and drying to obtain the crystalline product.

[0057] Furthermore, the purifying agent includes one or more of sodium hydroxide and potassium hydroxide.

[0058] Furthermore, the recrystallization additive includes one or more of sodium carbonate, sodium phosphate, and sodium hydroxide, and the crystallization product is at least one of lithium carbonate, lithium phosphate, or lithium hydroxide.

[0059] Furthermore, step (3) is followed by the following steps: (4) The modified composite water electrolysis oxygen evolution reaction catalyst, conductive agent and binder prepared above are mixed and dispersed evenly in a solvent to obtain a first dispersion. The first dispersion is dropped onto the target electrode to obtain the water electrolysis anode electrode.

[0060] Furthermore, in step (4), the mass ratio of the modified composite water electrolysis oxygen evolution reaction catalyst to the conductive agent is (1:5)-(5:1).

[0061] Furthermore, in step (4), the first dispersion is a mixture of ethanol, water (solvent), binder (such as Nafion (5 wt%) solution, polytetrafluoroethylene PTFE, etc.).

[0062] Furthermore, in step (4), the solvent is a mixture of water and ethanol.

[0063] Furthermore, in step (4), the volume ratio of water, ethanol and binder is 3:1:(0.2-0.4).

[0064] Further, in step (4), the adhesive is a 5 wt% Nafion solution or polytetrafluoroethylene (PTFE).

[0065] Further, in step (4), the electrode material of the target electrode is one or more of nickel foam, carbon paper, and glassy carbon electrode, and the modified composite water electrolysis oxygen evolution reaction catalyst loading is 40~1000 μg·cm³. -2 .

[0066] The second objective of this invention is to provide a high-efficiency water electrolysis oxygen evolution reaction catalyst, which is prepared by modifying waste lithium battery cathode black powder based on electrochemical selective delithiation.

[0067] This invention provides a method for rapidly preparing a high-efficiency oxygen evolution reaction catalyst for water electrolysis and simultaneously recovering lithium elements by modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation. The method includes the following steps: using waste lithium-ion battery cathode black powder as the anode, selectively leaching lithium ions into the electrolyte through an electrochemical delithiation process to obtain a residual solid powder containing transition metal components after delithiation; subsequently, reacting it with a metal salt solution containing an external element under mild conditions, incorporating the external element into the solid structure, thereby obtaining a composite material with high-efficiency oxygen evolution reaction catalytic activity, i.e., a high-efficiency oxygen evolution reaction catalyst for water electrolysis. This invention finds that the introduction of the external element only significantly improves the catalytic performance of the residual solid component after electrochemical delithiation, while having no significant effect on the cathode powder that has not been delithiated. This method is simple, has mild reaction conditions, is low-cost, and environmentally friendly, achieving high-value-added resource utilization of residual components of waste lithium-ion battery cathode materials.

[0068] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention proposes a recycling process for waste lithium battery materials, which has the significant advantages of simple operation, controllable cost, and low equipment threshold. It does not rely on the long-term high-temperature treatment of pyrometallurgy and avoids the consumption of large amounts of acid and alkali reagents in hydrometallurgy. The process adopts electrochemical delithiation technology, which does not require the intervention of strong acids and alkalis throughout the process, thus avoiding the generation of large amounts of corrosive waste liquid. It takes into account both low cost and low energy consumption characteristics, and belongs to an environmentally friendly recycling path, effectively reducing the impact of waste lithium battery disposal on the ecological environment.

[0069] (2) The method proposed in this invention can achieve efficient recovery and resource reuse of multiple elements such as lithium, cobalt, nickel, and manganese in waste cathode materials, reduce energy consumption caused by repeated mining, and achieve the goal of resource conservation. The modified oxygen evolution reaction catalyst prepared in the end has significantly improved catalytic performance compared with the initial waste lithium battery cathode powder, exhibiting better electrolytic water electrolysis catalytic activity and structural stability, and can significantly optimize the oxygen evolution reaction efficiency; at the same time, the process is easy to operate and adaptable to large-scale production, which greatly improves the economic added value of waste lithium battery recycling.

[0070] (3) This invention integrates the catalyst preparation and lithium extraction processes, thereby obtaining a high-performance water electrolysis anode catalyst while efficiently extracting high-value lithium from spent lithium batteries to produce high-purity, high-value-added lithium compound products. This technological approach achieves the dual goals of comprehensive resource utilization and efficient energy conversion, possessing significant economic and environmental value. Attached Figure Description

[0071] Figure 1These are the XRD patterns and corresponding PDF cards of de-NCM811-Fe, s-NCM811, and de-NCM811 in Embodiment 1 of the present invention.

[0072] Figure 2 The figures show the ternary lithium composite materials of de-NCM811-Fe, de-NCM523-Fe, and de-NCM622-Fe iron-doped electrochemically selectively delithiated materials in Example 1 of this invention, and the oxygen evolution reaction performance of s-NCM811, s-NCM523, and s-NCM622 loaded on a glassy carbon electrode in Comparative Example 1, after cyclic voltammetry scanning and stabilization. s-NCM811, s-NCM523, and s-NCM622 are the initial ternary lithium powders before delithiation and iron doping.

[0073] Figure 3 The figures show the ternary lithium composite materials of de-NCM811-Fe, de-NCM523-Fe, and de-NCM622-Fe iron element doped with electrochemical selective delithiation in Example 1 of the present invention, and the oxygen evolution reaction performance of s-NCM811-Fe, s-NCM523-Fe, and s-NCM622-Fe loaded on glassy carbon electrodes in Comparative Example 2 after cyclic voltammetry scanning for stabilization.

[0074] Figure 4 The images show the TEM, HRTEM, SAED, and EDS elemental distribution maps of the ternary lithium composite material after electrochemical selective delithiation of iron doped de-NCM811-Fe in Example 1 of this invention and the s-NCM811-Fe in Comparative Example 2. Among them, (a) is the TEM of s-NCM811-Fe, (b) is the HRTEM of s-NCM811-Fe, (c) is the SAED of s-NCM811-Fe, (d) is the EDS overlay of s-NCM811-Fe, (e) is the Ni element distribution map of s-NCM811-Fe, (f) is the Fe element distribution map of s-NCM811-Fe, (g) is the TEM of de-NCM811-Fe, (h) is the HRTEM of de-NCM811-Fe, (i) is the SAED of de-NCM811-Fe, (j) is the EDS overlay map of de-NCM811-Fe, (k) is the Ni element distribution map of de-NCM811-Fe, and (l) is the Fe element distribution map of de-NCM811-Fe. The distributions of Co and Mn are basically consistent with those of the bulk particles, so they are not all listed.

[0075] Figure 5The figures show the oxygen evolution reaction performance of the ternary lithium composite material after electrochemical selective delithiation of de-NCM811-Fe iron element doped in Example 1 of this invention, and the oxygen evolution reaction performance of de-NCM811-KOH and de-NCM811-H2O loaded on glassy carbon electrodes in Comparative Example 3 after cyclic voltammetry scanning. Detailed Implementation

[0076] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. 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 for illustrative purposes only and are not intended to limit the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0077] Any value in the numerical range disclosed in this invention is not limited to the precise 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 individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0078] Preparation methods, materials, structures, or composition ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0079] Steps not specified will be performed according to standard procedures. All reagents and instruments used are readily available and commercially available products, and the technical terminology employed conforms to general industry standards.

[0080] This invention provides a method for rapidly preparing a high-efficiency catalyst for water electrolysis oxygen evolution reaction and simultaneously recovering lithium elements by modifying waste lithium battery cathode black powder based on electrochemical selective delithiation.

[0081] The process includes the following steps: Step 1, electrochemical delithiation: After preparing the waste lithium-ion battery cathode powder into an electrode, lithium is selectively leached into the electrolyte using an electrochemical delithiation device; Step 2, the residual solid powder containing transition metal components after delithiation is collected and dispersed in a metal salt solution containing foreign elements to react, obtaining a modified high-efficiency oxygen evolution reaction catalyst for water electrolysis; Step 3, the electrolyte containing lithium ions is collected, evaporated, concentrated, and impurities are removed, and a recrystallization additive is added to recover lithium from the solution; Step 4, the obtained high-efficiency oxygen evolution reaction catalyst for water electrolysis, a conductive agent, and a binder are mixed and uniformly dispersed in a solvent to obtain a dispersion, which is then dropped onto the target electrode to obtain an anode electrode for water electrolysis. This invention achieves efficient recycling and reuse of waste lithium-ion battery cathode materials, as well as effective resource recycling, and the oxygen evolution reaction performance of the obtained catalyst is significantly improved compared to the original waste lithium-ion battery cathode materials.

[0082] A method for preparing a composite catalyst for the anode side (oxygen evolution reaction) of water electrolysis by recycling waste lithium battery cathode materials includes the following steps: Waste lithium-ion battery cathode black powder and PVDF binder were mixed, NMP was added, and the mixture was stirred to form a slurry. This slurry was then coated onto graphite paper and vacuum dried. Coating the waste lithium-ion battery cathode black powder onto the current collector serves to conduct current during the delithiation process and allows for the recovery of the cathode material from the current collector as powder after delithiation, facilitating subsequent modification. The coated electrode was then cut to a suitable size to serve as the anode for electrochemical delithiation. A platinum sheet was used as the cathode, and a 0.1 M sodium sulfate solution was used as the electrolyte. The delithiation reaction was carried out at a voltage of 1.5-2.5 V. At this voltage, lithium ions in the waste lithium-ion battery cathode black powder were released from the structure (a process similar to the charging process of a lithium-ion battery), while other transition metal elements in the waste lithium-ion battery cathode black powder remained in the solid powder. After the reaction, an electrolyte containing lithium ions and a delithiated cathode material electrode were obtained. After delithiation, the active material on the electrode is gently scraped off (this step should avoid scraping off the current collector as much as possible to reduce contamination), resulting in the residual solid powder containing transition metal components after delithiation.

[0083] The modified catalyst material was prepared by introducing foreign elements into the residual solid powder containing transition metal components after delithiation: the residual solid powder containing transition metal components after delithiation was soaked in a 0.1 M ferric sulfate solution. The solution was placed in an ultrasonic cleaner, and the powder was uniformly dispersed and iron ions were incorporated using ultrasound. Ultrasound was continued for 0.1-8 hours to form iron-doped nickel-based composite catalysts deNCM955-Fe, deNCM811-Fe, and deNCM523-Fe (de indicates electrochemical pre-delithiation). The catalyst after reaction was collected and dried, specifically to remove binders and other impurities: the catalyst was washed with a mixture of deionized water and ethanol, centrifuged at 8000 rpm for 8 minutes, and this process was repeated twice. Then, it was dried at 80°C under vacuum for 12 hours to obtain a highly efficient catalyst for the oxygen evolution reaction of water electrolysis.

[0084] The lithium-ion-containing electrolyte obtained by evaporation and concentration achieves a lithium concentration of 40 g·L⁻¹. -1 To improve extraction efficiency, then add 2 mol·L -1 The pH was adjusted to 7.8 with sodium hydroxide solution to precipitate the impurity metal ions. After filtration, the solution was dissolved at 15 mL / min. -1 A saturated sodium carbonate solution was added at a constant rate to react with lithium ions and form lithium carbonate precipitate. The mixture was continuously stirred (300 rpm) during precipitation, the solution temperature was maintained at 95°C, and the precipitation time was 2 hours. The resulting lithium carbonate precipitate was filtered, washed, and dried, thus completing the extraction of lithium.

[0085] Finally, the high-efficiency water electrolysis oxygen evolution reaction catalyst, conductive agent, and binder were uniformly dispersed in a solvent to obtain a dispersion (catalyst to conductive agent mass ratio of 1:44:1). The dispersion was a mixture of ethanol, water, and Nafion (wt5%) solution, with a volume ratio of 3:1:0.2:0.4. The dispersion was dropwise added to the target electrode (such as nickel foam, carbon paper, or glassy carbon electrode) to obtain a catalyst loading of 401000 μg·cm³. -2 The anode electrode for water electrolysis.

[0086] The following oxygen evolution reaction tests were performed on a Biologic electrochemical workstation using a three-electrode system: the electrolyte was 1 M KOH solution, a commercial platinum sheet electrode was used as the counter electrode, a mercury / mercury oxide (Hg / HgO) electrode was used as the reference electrode, and the final sample prepared in the examples (or comparative examples) was used as the working electrode.

[0087] Example 1 This embodiment provides a method for rapidly preparing a high-efficiency catalyst for the oxygen evolution reaction in water electrolysis and simultaneously recovering lithium by modifying waste ternary NCM black powder based on electrochemical selective delithiation, including the following steps: 500 mg of s-NCM811 (or s-NCM523 or s-NCM622) was mixed with 25 mg of PVDF and ground in a small mortar for 5 minutes. Then, 500 mg of NMP was added as a solvent, and the mixture was stirred at 300 rpm for 24 hours. The slurry was then coated onto graphite paper to a thickness of 200 μm and vacuum dried at 80 °C for 12 hours to obtain a coated ternary lithium electrode. The electrode was cut into 2 cm × 3 cm pieces, with a 2 cm × 2 cm area covered by the active material, serving as the anode for electrochemical delithiation. A platinum sheet of the same size or larger was selected as the cathode, and a 0.1 M sodium sulfate solution was used as the electrolyte. The delithiation reaction was carried out at 2.25 V for 0.5 hours to obtain an electrolyte containing lithium ions and a delithiated positive electrode material. After delithiation is completed, the delithiated positive electrode material is removed and allowed to air dry naturally. Then, a small spatula is used to gently scrape off the active material on the electrode. While scraping off the active material as completely as possible, the amount of graphite paper scraped off should be minimized to obtain approximately 20 mg of delithiated ternary lithium powder.

[0088] The delithiated ternary lithium powder de-NCM811 (or de-NCM523 or de-NCM622) was immersed in 30 mL of 0.1 M ferric sulfate solution and ultrasonicated for 0.5 hours using an ultrasonic cleaner, occasionally shaking the centrifuge tube to ensure uniform dispersion of the ternary lithium powder. After ultrasonication, the solution and solid powder were centrifuged at 8000 rpm for 8 minutes. The solid powder was then washed with 30 mL of a 1:1 mixture of deionized water and ethanol, and centrifuged again, repeating the process twice. After washing, the powder was dried at 80 °C for 12 hours to obtain the modified catalyst de-NCM811-Fe (or de-NCM523-Fe or de-NCM622-Fe), which is a highly efficient catalyst for the oxygen evolution reaction in water electrolysis.

[0089] The lithium-ion-containing electrolyte obtained by evaporation and concentration achieves a lithium concentration of 40 g·L⁻¹. -1 To improve the efficiency of subsequent lithium extraction, the lithium ion concentration in the solution can be increased by repeatedly performing multiple delithiation reactions in the same solution. Then, 2 mol·L⁻¹ is added. -1 The pH of the solution was adjusted to 7-8 with sodium hydroxide solution to precipitate the impurity metal ions. After filtering the precipitate, it was added to the solution at a rate of 1-5 mL / min. -1 A saturated sodium carbonate solution was added at a certain rate to allow it to react chemically with lithium ions, forming lithium carbonate precipitate. During the precipitation process, the solution was continuously stirred at 300 rpm, and the solution temperature was maintained at 95°C for 2 hours. The resulting lithium carbonate precipitate was filtered, washed, and dried, thus completing the extraction of lithium.

[0090] Electrode preparation: The modified catalyst, conductive agent Vulcan Carbon, and binder (Nafion (5 wt%)) were 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 (5 wt%), with a volume ratio of ethanol, water, and Nafion (5 wt%) of 3:1:0.2. The solid-liquid ratio of the obtained dispersion was 3.75 mg·mL⁻¹. -1 Furthermore, the dispersion droplets were added to a surface with an area of ​​0.19625 cm². 2 A catalyst loading of 255 μg·cm⁻¹ was obtained on a glassy carbon electrode. -2 The anode electrode for water electrolysis.

[0091] Comparative Example 1 This comparative example provides a catalyst in which untreated waste lithium battery cathode ternary lithium black powder is directly used as the catalyst. The catalyst material is named s-NCM811, or s-NCM523, s-NCM622. The oxygen evolution performance of the catalyst is tested using the same electrode preparation and electrochemical performance testing methods as in Example 1.

[0092] like Figure 1 As shown, the XRD data of s-NCM811, de-NCM811, and de-NCM811-Fe indicate that after electrochemical selective delithiation, the crystal structure of the de-NCM811 powder scraped from the current collector underwent significant changes. The characteristic diffraction peaks of the typical R3m layered crystal structure of s-NCM811 almost completely disappeared, replaced by a completely new set of characteristic diffraction peaks. This phenomenon indicates that the electrochemical delithiation treatment led to a complete phase transformation, converting it into a typical layered hydroxide crystal structure, Ni(OH)2 (NiOOH) (PDF #97-007-6650). Furthermore, after iron doping modification of de-NCM811, the characteristic diffraction peaks of de-NCM811-Fe almost completely disappeared, with only graphite substrate diffraction peaks observed around 26°. This phenomenon clearly indicates that the crystal structure has essentially transformed into an amorphous structure.

[0093] like Figure 2 As shown, the electrochemical CV curves of the oxygen evolution reaction (OER) of Example 1 under different voltage values ​​were obtained after electrochemical OER performance testing. The horizontal axis represents voltage, and the vertical axis represents current density. The de-NCM811-Fe, de-NCM523-Fe, and de-NCM622-Fe composite catalyst materials prepared in Example 1 of this invention exhibit an OER catalytic current density of 10 mA·cm⁻¹. -2The required overpotentials are approximately 270 mV, 267 mV, and 293 mV, respectively, and the electrochemical performance is significantly better than that of the initial materials s-NCM811, s-NCM523, and s-NCM622 in Comparative Example 1.

[0094] Comparative Example 2 This comparative example provides a catalyst that is identical to Example 1 in all other aspects except for omitting the preparation of the electrochemical delithiation anode electrode, electrochemical delithiation, and the extraction of the electrolyte containing lithium ions after delithiation. In this example, untreated waste lithium battery cathode ternary lithium black powder (i.e., s-NCM811, or s-NCM523, s-NCM622) is directly soaked in a 0.1M ferric sulfate solution for modification treatment, and finally the modified water electrolysis oxygen evolution reaction catalyst material is obtained. The corresponding catalysts are named s-NCM811-Fe, s-NCM523-Fe, and s-NCM622-Fe. like Figure 3 As shown, the electrochemical CV curves of the oxygen evolution reaction (OER) in Comparative Example 2 under different voltage conditions were obtained after electrochemical OER performance testing. The s-NCM811-Fe, s-NCM523-Fe, and s-NCM622-Fe composite catalyst materials prepared in Comparative Example 2 of this invention exhibit an OER catalytic current density of 10 mA·cm⁻¹. -2 The required overpotentials are approximately 315 mV, 321 mV, and 322 mV, respectively. Comparative results with Example 1 show that the performance of samples directly modified with iron doping from waste lithium-ion battery cathode ternary lithium black powder that has not undergone electrochemical delithiation treatment is relatively worse than that of samples modified with iron doping after delithiation.

[0095] like Figure 4 As shown, s-NCM811-Fe directly doped with iron without delithiation retains a relatively complete particle morphology and regular lattice, with iron mainly enriched in the particle edge regions. In contrast, de-NCM811-Fe obtained after delithiation exhibits a more widespread and continuous distribution of iron, and the sample displays more pronounced localized disorder. These results indicate that electrochemical delithiation treatment facilitates the uniform introduction of iron and promotes the formation of structures more conducive to the oxygen evolution reaction.

[0096] Comparative Example 3 This comparative example provides a catalyst, taking NCM811 as an example. Compared with Example 1, all other parts are the same, except that the 0.1M ferric sulfate solution is replaced with KOH solution without foreign transition metal elements or pure deionized water. Finally, modified water electrolysis oxygen evolution reaction catalyst materials are obtained, named de-NCM811-KOH and de-NCM811-H2O, respectively.

[0097] like Figure 5As shown, the electrochemical CV curves of the oxygen evolution reaction (OER) in Comparative Example 3 under different voltage conditions were obtained after electrochemical OER performance testing. Compared with de-NCM811-Fe, the de-NCM811-KOH and de-NCM811-H2O catalysts prepared in Comparative Example 3 exhibit an OER catalytic current density of 10 mA·cm⁻¹. -2 The required overpotentials were approximately 377 mV, 386 mV, and 270 mV, respectively. This result indicates that the performance improvement of the delithiated samples after modification stems from the introduction of exogenous elements, rather than from the effects of ultrasound or stirring.

[0098] In summary, this invention provides a novel process for converting spent lithium-ion batteries into composite structural materials that can be used as anode catalysts for water electrolysis. This process boasts core advantages such as simple operation, low cost, and minimal equipment requirements. The technical path is as follows: after recovering the cathode material from spent lithium-ion batteries, lithium ions are selectively extracted from the cathode black powder using an electrochemical method. Then, a simple and mild process is used to introduce foreign elements into the residual solid components after electrochemical delithiation, ultimately preparing a highly efficient oxygen evolution reaction catalyst for water electrolysis. This process achieves the harmless disposal and high-value recycling of spent lithium-ion batteries at low cost. Compared to traditional battery recycling technologies, it eliminates the need for prolonged high-temperature reactions in pyrometallurgical processes and the consumption of large amounts of acid and alkali reagents required in hydrometallurgical processes. It also features low cost and low energy consumption, making it an environmentally friendly recycling technology that significantly reduces environmental pollution from spent lithium-ion battery disposal. By converting the recovered cathode material into an oxygen evolution reaction catalyst, this invention enables efficient resource reuse, avoids the energy consumption caused by repeated mining, and achieves the goal of resource conservation. The final product, a highly efficient water electrolysis oxygen evolution reaction catalyst, exhibits excellent catalytic activity and structural stability, effectively improving the oxygen evolution reaction efficiency. Furthermore, the process is easy to control and adaptable to large-scale production, significantly increasing the economic added value of recycled lithium-ion batteries. Simultaneously, the high-value lithium element extracted from the waste batteries can be converted into high-purity, high-value-added pure lithium compounds. Lithium, as an indispensable core raw material for the new energy battery industry, has seen its market demand increase year by year. This invention enables the efficient recovery of residual lithium resources from waste batteries, improving resource utilization and providing raw material replenishment for the new energy battery industry. This invention constructs an integrated technology path for catalyst preparation and lithium extraction. While producing a high-performance water electrolysis anode catalyst, it simultaneously recovers and purifies high-value lithium resources. Electrochemical delithiation selectively extracts lithium from the material, making the solution environmentally friendly. A high-performance catalyst is prepared using a simple ultrasonic method. This technology achieves the dual goals of comprehensive resource utilization and efficient energy conversion, possessing significant economic and environmental value.

[0099] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any 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 invention should be within the protection scope of the present invention.

Claims

1. A method for modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation for the preparation of a high-efficiency catalyst for oxygen evolution reaction in water electrolysis, characterized in that, The method includes the following steps: Waste lithium battery cathode black powder is used to prepare the anode sheet of an electrochemical delithiation device, and lithium ions in the cathode material are selectively leached into the electrolyte by electrochemical method, resulting in an electrolyte containing lithium ions and residual solid powder containing transition metal components after delithiation. The residual solid powder containing transition metal components after delithiation is dispersed in a metal salt solution containing foreign elements for reaction. After centrifugation to separate the solid, the solid is further washed and dried to obtain a composite water electrolysis oxygen evolution reaction catalyst, which is the high-efficiency water electrolysis oxygen evolution reaction catalyst.

2. The method for modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation for use in preparing a high-efficiency catalyst for oxygen evolution reaction in water electrolysis, as described in claim 1, is characterized in that... The method for preparing the anode sheet of an electrochemical delithiation device from waste lithium battery cathode black powder includes the following steps: Waste lithium battery cathode black powder, binder, and conductive agent are mixed and then added to a solvent to prepare a slurry. The obtained slurry is loaded onto the current collector with a certain loading capacity and then vacuum dried to obtain the coated anode sheet. The waste lithium battery cathode black powder is at least one of ternary nickel-cobalt-manganese and lithium cobalt oxide. The adhesive is at least one of polyvinylidene fluoride, polyacrylic acid, styrene-butadiene rubber, sodium carboxymethyl cellulose, and polytetrafluoroethylene; The solvent is at least one of N-methylpyrrolidone, water, and alcohol; The conductive agent is at least one of acetylene black, conductive carbon black, carbon nanotubes, and graphene. The current collector is one of the inert conductive substrates; The vacuum drying temperature is 60~120℃; The surface loading of waste lithium-ion battery cathode black powder coated on the current collector is 1~50 mg·cm³. -2 .

3. The method for modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation for use in preparing a high-efficiency catalyst for oxygen evolution reaction in water electrolysis, as described in claim 1, is characterized in that... The electrochemical delithiation device includes an electrolytic cell, an anode electrode, and a cathode electrode; The cathode electrode of the electrochemical delithiation device is a Pt-based material electrode. The electrolytic cell is used to hold the electrolyte for electrochemical delithiation, and the electrolyte is at least one of Na2SO4 aqueous solution, Na2CO3 aqueous solution, NaCl aqueous solution, KCl aqueous solution, K2SO4 aqueous solution, NaNO3 aqueous solution, and KNO3 aqueous solution; The electrochemical method includes the following steps: applying an electrical signal between the anode and cathode to achieve an electrochemical delithiation process; The electrical signal is applied in one of the following ways: constant voltage, constant current, or alternating constant current and constant voltage.

4. The method for modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation for use in preparing a high-efficiency catalyst for oxygen evolution reaction in water electrolysis, as described in claim 3, is characterized in that... After completing the electrochemical delithiation, the residual solid powder containing transition metal components after delithiation on the anode plate is collected, and the residual solid powder containing transition metal components after delithiation is placed in an aqueous solution of metal salt containing foreign elements to react and modify the structure. The residual solid powder containing transition metal components after delithiation on the anode electrode is collected by one or more of physical scraping and ultrasonic stripping.

5. The method for modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation for use in preparing a high-efficiency catalyst for oxygen evolution reaction in water electrolysis, as described in claim 1, is characterized in that... When the waste lithium battery cathode black powder is a ternary nickel-cobalt-manganese compound, the metal salt in the metal salt solution containing foreign elements includes iron-soluble compounds. The iron-containing soluble compound is selected from at least one of inorganic iron salts or organic iron salts; When the waste lithium battery cathode black powder is lithium cobalt oxide, the metal salt in the metal salt aqueous solution includes soluble compounds containing iron, nickel, or both iron and nickel. The iron-, nickel-, or iron- and nickel-containing soluble compounds are selected from at least one of inorganic iron-, nickel-, or iron- and nickel-containing salts or organic iron-, nickel-, or iron- and nickel-containing salts. The solvent in the metal salt solution containing the foreign element is a polar solvent, including at least one of water, alcohol solvents, ketone solvents, tetrahydrofuran, and N,N-dimethylformamide.

6. The method for modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation for use in preparing a high-efficiency catalyst for oxygen evolution reaction in water electrolysis, as described in claim 1, is characterized in that... The concentration of the metal salt solution containing the foreign element is 10-50 g / L; The concentration of the residual solid powder containing transition metal components after delithiation in the metal salt solution containing foreign elements is between 1 and 5 g / L.

7. The method for modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation for use in preparing a high-efficiency catalyst for oxygen evolution reaction in water electrolysis, as described in claim 1, is characterized in that... The residual solid powder containing transition metal components after delithiation is dispersed in a metal salt solution containing foreign elements to obtain a mixture. The mixture is then subjected to static, continuous ultrasonic, stirring, or oscillation to modify the waste lithium battery cathode black powder.

8. The method for modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation for use in preparing a high-efficiency catalyst for oxygen evolution reaction in water electrolysis, as described in claim 7, is characterized in that... When the reaction is allowed to stand, or subjected to continuous ultrasound, or stirred, or oscillated, the reaction time is 0.1-5 hours.

9. The method for modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation for use in preparing a high-efficiency catalyst for oxygen evolution reaction in water electrolysis, as described in claim 1, is characterized in that... The electrolyte containing lithium ions is further recrystallized into lithium salt to complete the recovery of lithium. The further recrystallization method includes the following steps: The collected lithium-ion-containing electrolyte is collected by evaporation and concentration. Then, a purifying agent is added to the concentrated electrolyte to adjust the pH value of the solution, so that the impurity metal ions are precipitated in the form of hydroxide precipitates. The hydroxide precipitates are filtered to obtain the purified lithium-ion-containing soaking solution. A recrystallization additive is added to the purified lithium-ion-containing soaking solution to precipitate lithium ions into lithium salts, and the crystalline product is separated to achieve the extraction of lithium. The purifying agent includes one or more of sodium hydroxide and potassium hydroxide; The recrystallization additive includes one or more of sodium carbonate, sodium phosphate, and sodium hydroxide, and the crystallization product is at least one of lithium carbonate, lithium phosphate, or lithium hydroxide.

10. A highly efficient catalyst for the oxygen evolution reaction in water electrolysis, characterized in that, The catalyst is prepared by modifying waste lithium-ion battery cathode black powder based on electrochemical selective delithiation as described in any one of claims 1-9 for use in preparing a high-efficiency catalyst for water electrolysis oxygen evolution reaction.

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