A regenerated positive electrode active material and a method for preparing the same

Abstract

This application discloses a method for preparing recycled positive electrode active material, comprising the steps of: adding waste lithium-ion battery positive electrode material sequentially to an aqueous solution of 2-hydroxypropionic acid and / or aspartic acid and an aqueous solution of ascorbic acid and / or tyrosine for reaction; then filtering, removing residue, and adjusting the valence metal ions and M in the leachate. n+ The molar ratio is adjusted, pH is adjusted, and the mixture is heated and concentrated by evaporation to form a gel-like substance. The gel-like substance is then calcined in steps, and then immersed in a solution containing a coating agent for a solvothermal reaction. After drying and low-temperature sintering, the regenerated positive electrode active material is obtained. The valuable metal ions include Ni. 2+ Co 2+ Mn 2+ Li + and M n+ M is one or more of W, Zr, Al, B, Sr, Nb, and Ta, and n is 2, 3, 5, or 6; the coating agent includes a coating precursor and a phosphorus compound. This application also provides a regenerated positive electrode active material.

Description

Technical Field

[0001] This application relates to the field of recycling technology for cathode materials from waste lithium-ion batteries, and in particular to a regenerated cathode active material and its preparation method. Background Technology

[0002] Current technologies for recycling cathode materials from spent lithium-ion batteries mainly focus on wet processes, primarily recovering Li, Ni, Co, and Mn elements. Valuable metals in the cathode material are transferred to a solution in ionic form through acid or alkaline leaching. Then, through separation, purification, and multi-step precipitation, salts or oxides such as nickel sulfate, cobalt sulfate, manganese sulfate, lithium carbonate, cobalt oxide, and nickel oxide are obtained. However, this recycling process is complex, and achieving efficient separation of various metal ions in the leached solution is technically challenging, resulting in poor separation performance, a cumbersome process flow, and high costs.

[0003] Furthermore, the active materials of lithium nickel cobalt manganese oxide cathodes currently used in the market have all undergone modification treatment, meaning that the materials themselves still contain other modifying elements, such as Al, Zr, and B. Since the content of these elements in the active material system is low, these elements are usually removed as impurities during the recycling process, and only Li, Ni, Co, and Mn elements are recycled and processed. This results in resource waste and increases the cost of subsequent treatment of these impurities.

[0004] In summary, it is necessary to develop a simple and efficient regeneration method that can not only recover and reuse Li, Ni, Co, and Mn elements, but also recover and regenerate the modified elements in one step, while ensuring that the performance of the regenerated positive electrode active material is further improved. Summary of the Invention

[0005] To address the aforementioned problems, this application provides a method for preparing a regenerated positive electrode active material.

[0006] Another objective of this application is to provide a regenerated positive electrode active material prepared by the above-described preparation method.

[0007] This application provides a method for preparing a regenerated positive electrode active material, comprising the following steps:

[0008] Waste lithium-ion battery cathode material is added to an aqueous solution of 2-hydroxypropionic acid and / or aspartic acid for a first reaction; an aqueous solution of ascorbic acid and / or tyrosine is added to the system after the first reaction at a certain flow rate for a second reaction, resulting in a black turbid liquid; the obtained black turbid liquid is filtered to remove residue, yielding a leachate rich in valuable metal ions; the concentrations of each valuable metal ion and M in the leachate are adjusted. n+The molar ratio was adjusted, the pH was adjusted, and the mixture was heated and evaporated to form a gel-like substance. The gel-like substance was then subjected to stepwise calcination to obtain a primary regenerated positive electrode active material. The primary regenerated positive electrode active material was then added to a solution containing a coating agent for a solvothermal reaction, dried, and sintered at a low temperature to obtain a regenerated positive electrode active material.

[0009] The valuable metal ions include Ni. 2+ Co 2+ Mn 2+ Li + and M n+ M is one or more of W, Zr, Al, B, Sr, Nb, and Ta, and n is 2, 3, 5, or 6; the coating agent includes a coating precursor and a phosphorus compound.

[0010] This application also provides a regenerated positive electrode active material prepared by the above preparation method.

[0011] Compared with existing technologies, the preparation method provided in this application organically combines the recycling of waste lithium-ion battery cathode materials containing modified elements with the preparation of cathode active materials. A one-step sol-gel method is used to crosslink metal ions to regenerate new cathode active materials. During the regeneration process, the modified elements are fully utilized to dope and modify the regenerated cathode active materials, avoiding waste of modified elements and eliminating the need for subsequent dry doping, thus shortening the process, saving costs, and achieving the goal of doping modification of the regenerated cathode active materials. The doped ions are uniformly distributed in the bulk phase of the cathode material, achieving uniform distribution of doped elements and enabling the cathode material to preferentially grow towards a layered structure. Simultaneously, in the later stages of the regeneration process, a solvothermal method is used to coat the initially regenerated cathode active materials, making the material structure more stable and effectively improving the electrochemical performance of the cathode material. Attached Figure Description

[0012] Figure 1 This is the XRD pattern of the regenerated positive electrode active material prepared in Example 1 of this application.

[0013] Figure 2 The image shows the cycling curves of the lithium-ion batteries prepared in Example 1 and Comparative Examples 1-2 of this application at 10C rate and 45°C. Detailed Implementation

[0014] The present application is further illustrated below with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on this application are within the scope of protection claimed in this application.

[0015] One embodiment of this application provides a method for preparing a regenerated positive electrode active material, comprising the following steps:

[0016] Waste lithium-ion battery cathode material is added to an aqueous solution of 2-hydroxypropionic acid and / or aspartic acid for the first reaction;

[0017] A second reaction was carried out by adding an aqueous solution of ascorbic acid and / or tyrosine to the system after the first reaction at a certain flow rate, resulting in a black turbid liquid;

[0018] The resulting black turbid liquid was filtered to remove residue, yielding a leachate rich in valuable metal ions.

[0019] Adjusting the valence metal ions and M in the leachate n+ The molar ratio is adjusted, pH is adjusted, and the mixture is heated, evaporated, and concentrated to form a gel-like substance;

[0020] The gel-like substance is calcined in steps to obtain a primary regenerated positive electrode active material;

[0021] The primary regenerated positive electrode active material is added to a solution containing a coating agent for a solvothermal reaction, dried, and then sintered at low temperature to obtain the regenerated positive electrode active material.

[0022] The valuable metal ions include Ni. 2+ Co 2+ Mn 2+ Li + and M n+ M is one or more of W, Zr, Al, B, Sr, Nb, and Ta, and n is 2, 3, 5, or 6; the coating agent includes a coating precursor and a phosphorus compound.

[0023] This application organically combines the recycling of valuable metals from spent lithium-ion batteries with the preparation of cathode materials. A one-step sol-gel method is used to crosslink metal ions to regenerate new cathode active materials. During the regeneration process, modifying elements are fully utilized to dope and modify the regenerated cathode active materials, ensuring uniform distribution of dopant ions within the bulk phase. This atomic-level homogeneous mixing yields doped primary regenerated cathode active materials with high activity and high crystallinity. This eliminates the need for subsequent dry doping, shortening the process, saving costs, and achieving the goal of doping modification of the regenerated material. The doped primary regenerated cathode active material is then subjected to solvothermal treatment to achieve coating, further improving its performance. This method is simple and easy to implement, eliminates the need for metal ion separation in the leachate, shortens the process, is low-cost, and easily industrialized.

[0024] In existing technologies, the acid leaching step typically involves adding waste lithium-ion battery cathode materials to a mixed solution of hydrochloric acid and hydrogen peroxide to obtain a leachate. This inorganic acid leaching system requires the subsequent separation of pure lithium-nickel-cobalt-manganese compounds, or the extraction of lithium from the leachate followed by co-precipitation to generate a nickel-cobalt-manganese composite hydroxide. This hydroxide is then calcined and doped with a lithium source to obtain the final cathode material. This method is lengthy, cumbersome, and costly. This application employs a pre-acidification treatment with 2-hydroxypropionic acid and / or aspartic acid, followed by a continuous reduction leaching method with ascorbic acid and / or tyrosine. This fully utilizes the acidity, chelation, and reducing properties of organic acids, avoiding the problems of partial loss of reducing power and insufficient utilization of reducing power caused by the one-time addition of ascorbic acid and / or tyrosine. This not only enables the recycling of the main elements Li, Ni, Co, and Mn in the cathode material of waste lithium-ion batteries, but also ensures that trace amounts of modifying elements can be efficiently leached and perfectly integrated into the subsequent regeneration process, achieving in-situ doping of the regenerated cathode active material.

[0025] Meanwhile, in order to further improve the performance of the primary regenerated positive electrode active material and stabilize the doping elements, it was subjected to solvothermal treatment. The surface treatment with phosphate compounds made the structure of the regenerated positive electrode active material more stable and suppressed the side reactions with the electrolyte, thereby improving the electrochemical performance of the positive electrode active material and giving the battery better high-temperature safety performance and high-temperature rate performance.

[0026] In some embodiments, the coating precursor is one of tetraethoxysilane, silicon ethoxide, titanium ethoxide, titanium tetraethoxysilane, titanium tetraethoxysilane, vanadium acetate, vanadium triisopropoxide, vanadium ethoxide, and vanadium tert-butoxide. The phosphorus compound is one of triethyl phosphate, trimethyl phosphate, trialkyl phosphate, and potassium dihydrogen phosphate.

[0027] In some embodiments, the chemical formula of the regenerated positive electrode active material is Li. k Ni x Co y Mn z M m O2·sT3(PO4)4, where x:y:z:m=(0.10~0.85):(0.05~0.20):(0.10~0.35):(0.001~0.1), and x+y+z+m=1, 0.95≤k≤1.15, 0<s≤0.05; T is one of Ti, Si, and V.

[0028] The specific ratio and amount of the coating precursor and phosphorus compound can be reasonably determined based on the molar ratio of T and P elements in the target product.

[0029] In some embodiments, the general chemical formula of the spent lithium-ion battery cathode material is LiNi. x Co y Mn z M m O2, where x:y:z:m=(0~1):(0~1):(0~1):(0.001~0.1), and x, y, and z are not all 0 at the same time.

[0030] In some embodiments, the mass ratio of 2-hydroxypropionic acid and / or aspartic acid to the mass of the spent lithium-ion battery cathode material is (5-50):(50-95). The first reaction is carried out at a temperature of 30-70°C for 0.1-1 h with a stirring speed of 200-600 r / min.

[0031] In some embodiments, the mass ratio of the ascorbic acid and / or tyrosine to the mass of the spent lithium-ion battery cathode material is 5–500:1000. The second reaction is carried out at a temperature of 30–70°C for 0.1–1 h, with a stirring speed of 300–800 r / min.

[0032] The concentration of the ascorbic acid and / or tyrosine solution is 0.01–3 mol / L; the flow rate added to the reaction system is 0.1–20 L / h.

[0033] In the specific implementation process, the content of each valuable metal ion in the leachate can be detected using conventional detection methods such as atomic emission spectrometry (ICP). Then, by adding salts of the corresponding metal elements, the proportion of each metal element in the leachate can be adjusted to the target ratio. Performing two ICP tests on the leachate before and after the test can determine whether the proportion of each metal ion meets the design requirements. The salts of the corresponding metal elements can be any salt soluble in this leachate system.

[0034] In some embodiments, the pH is adjusted to 6.5–7.5, and the heating temperature is 40–90°C; the reagent for adjusting the pH is one or more of ammonia, ammonium acetate, and ammonium citrate.

[0035] In some embodiments, the stepwise calcination includes: calcining the gel in an oxygen or air atmosphere in two steps. The first step of calcination is carried out at a temperature of 300–450°C, with a residence time of 2–12 h and a heating rate of 1–10°C / min; the second step of calcination is carried out at a temperature of 550–900°C, with a residence time of 1–15 h and a heating rate of 5–20°C / min.

[0036] The equipment for step-by-step calcination includes one of the following: rotary kiln, tube furnace, box furnace, bell furnace, or roller kiln.

[0037] In some embodiments, the solvothermal reaction is carried out at a temperature of 100–300°C for a total time of 4–8 hours. The solvothermal reaction comprises two stages, with the temperature ratio of the first stage to the second stage being 1:(1–2), and the holding time ratio of the first stage to the second stage being 1:(1–2). The low-temperature sintering treatment is carried out at a temperature of 300–450°C for a time of 2–6 hours.

[0038] In this application, the regenerated positive electrode active material is prepared using a sol-gel method combined with stepwise calcination. The first step, calcination, involves thoroughly removing organic matter or organic carbon chains from the sol-gel process at a relatively low temperature, preparing for the next step of material crystallization. The second step, calcination, is the process of material crystallization at a higher temperature, i.e., the construction of the material structure. The material prepared by this process is essentially at an applicable level.

[0039] This application also provides a regenerated positive electrode active material prepared by the above preparation method.

[0040] The preparation method and performance of the regenerated positive electrode active material are described below using specific examples and comparative examples.

[0041] Example 1

[0042] This embodiment provides a method for preparing a regenerated positive electrode active material, wherein the chemical formula of the regenerated positive electrode active material to be prepared is LiNi. 0.55 Co 0.199 Mn 0.246 Ta 0.005 O2·0.002Ti3(PO4)4. The preparation method specifically includes the following steps:

[0043] (1) Add 55g of 2-hydroxypropionic acid and 2g of aspartic acid to 3L of deionized water to obtain a mixed solution. 500g of LiNi... 0.55 Co 0.199 Mn 0.248 Ta 0.003 O2 was added to the above mixed solution and reacted for 0.2 h under heating conditions of 60°C and stirring conditions of 300 r / min.

[0044] (2) Add 20g of ascorbic acid and 1g of tyrosine to 4.8L of deionized water to obtain a solution. Slowly pump the above solution into the system after the reaction in step (1) at a flow rate of 4.8L / h. The reaction conditions are: temperature 45℃, stirring speed 350r / min. After 1h, the pumping is stopped, and a black turbid liquid is obtained.

[0045] (3) The black turbid liquid is filtered to remove the filter residue, and a leachate rich in valuable metal ions is obtained.

[0046] (4) Adjusting the Ni content in the leachate 2+ Co 2+ Mn 2+ Ta 5+ Li + The molar ratio x:y:z:m:k satisfies x:y:z:m=0.55:0.199:0.246:0.005, k=1.08, and ammonium acetate solution is added to adjust the pH to 7.1. Most of the water is removed by heating at 50℃ to form a gel.

[0047] (5) The above gel is transferred to the roller kiln and calcined in steps under an oxygen atmosphere. The temperature of the first step of calcination is 250°C, the residence time is 3h, and the heating rate is 5°C / min. The temperature of the second step of calcination is 800°C, the residence time is 10h, and the heating rate is 10°C / min. After sieving the calcined material, the primary regenerated positive electrode active material is obtained.

[0048] (6) According to the stoichiometric ratio of the target product, the primary regenerated positive electrode active material is added to a high-pressure reactor containing a mixed solution of tetraethanol titanium and triethyl phosphate in a specific molar amount. The reaction is first carried out at 150°C for 2.5 hours, and then the temperature is raised to 300°C and the reaction is continued for 5 hours. The reaction product is filtered, dried, and then calcined at 400°C for 4 hours under a nitrogen atmosphere to obtain a regenerated positive electrode active material.

[0049] Figure 1 The image shows the XRD pattern of the regenerated positive electrode active material. As can be seen from the image, the positive electrode material prepared in this embodiment is LiNi. 0.55 Co 0.199 Mn 0.246Ta 0.005 The diffraction peaks of O2·0.002Ti3(PO4)4 are sharp, indicating high crystallinity and the absence of impurity peaks. The main peaks are consistent with the structure of nickel-cobalt-manganese cathode material, indicating that the doping elements have been fully incorporated into the lattice structure of the cathode material and have not formed compounds separately outside the main structure of the nickel-cobalt-manganese cathode material.

[0050] Example 2

[0051] This embodiment provides a method for preparing a regenerated positive electrode active material, wherein the chemical formula of the regenerated positive electrode active material to be prepared is LiNi. 0.698 Co 0.099 Mn 0.198 Al 0.005 O2·0.003VPO4. The preparation method specifically includes the following steps:

[0052] (1) Add 520g of 2-hydroxypropionic acid to 30L of deionized water to obtain a solution. 5200g of the solution is composed of LiNi. 0.698 Co 0.099 Mn 0.198 Al 0.005 O2 was added to the above solution and reacted for 0.2 h under heating conditions of 60°C and stirring conditions of 300 r / min.

[0053] (2) Add 130g of ascorbic acid and 10g of tyrosine to 20L of deionized water to obtain a solution. Slowly pump the above solution into the system after the reaction in step (1) at a flow rate of 20L / h. The reaction conditions are: temperature 50℃, stirring speed 350r / min. After 1h, the pumping is stopped, and a black turbid liquid is obtained.

[0054] (3) The black turbid liquid is filtered to remove the filter residue, and a leachate rich in valuable metal ions is obtained.

[0055] (4) Adjusting the Ni content in the leachate 2+ Co 2+ Mn 2+ Al 3+ Li + The molar ratio x:y:z:m:k satisfies x:y:z:m=0.698:0.099:0.198:0.005, k=1.08, and ammonium citrate solution is added to adjust the pH to 7.0. Most of the water is removed by heating at 50℃ to form a gel.

[0056] (5) The above gel is transferred to the roller kiln and calcined in steps under an oxygen atmosphere. The temperature of the first step of calcination is 350℃, the residence time is 3h, and the heating rate is 5℃ / min. The temperature of the second step of calcination is 820℃, the residence time is 11h, and the heating rate is 10℃ / min. After sieving the calcined material, the primary regenerated positive electrode active material is obtained.

[0057] (6) According to the stoichiometric ratio of the target product, the primary regenerated positive electrode active material is added to a high-pressure reactor containing a mixed solution of vanadium tert-butoxide and trimethyl phosphate in a specific molar amount. The reaction is first carried out at 180°C for 2 hours, and then the temperature is raised to 280°C and the reaction is continued for 3.8 hours. The reaction product is filtered, dried, and then calcined at 420°C for 4 hours under a nitrogen atmosphere to obtain a regenerated positive electrode active material.

[0058] Example 3

[0059] This embodiment provides a method for preparing a regenerated positive electrode active material, wherein the chemical formula of the regenerated positive electrode active material to be prepared is LiNi. 0.499 Co 0.199 Mn 0.296 Zr 0.002 W 0.002 O2·0.005Si3(PO4)4. The preparation method specifically includes the following steps:

[0060] (1) A solution was obtained by adding a mixture of 1000g 2-hydroxypropionic acid and 5g aspartic acid to 90L of deionized water. 10kg of this solution was then used to form LiNi. 0.499 Co 0.199 Mn 0.296 Zr 0.002 W 0.002 O2 was added to the above solution and reacted for 0.2 h under heating conditions of 52°C and stirring conditions of 310 r / min.

[0061] (2) Add 200g of ascorbic acid to 18L of deionized water to obtain a solution. Slowly pump the above solution into the system after the reaction in step (1) at a flow rate of 18L / h. The reaction conditions are: temperature 45℃, stirring speed 350r / min. After 1h, the pumping is stopped, and a black turbid liquid is obtained.

[0062] (3) The black turbid liquid is filtered to remove the filter residue, and a leachate rich in valuable metal ions is obtained.

[0063] (4) Adjusting the Ni content in the leachate 2+ Co 2+ Mn 2+ Zr 2+ W 5+Li + The molar ratio x:y:z:m:f:k satisfies x:y:z:m=0.499:0.199:0.296:0.002:0.002, k=1.08, and ammonium acetate solution is added to adjust the pH to 7.1. Most of the water is removed by heating at 50℃ to form a gel.

[0064] (5) The above gel is transferred to the roller kiln and calcined in steps under an oxygen atmosphere. The temperature of the first step of calcination is 310℃, the residence time is 3h, and the heating rate is 5℃ / min. The temperature of the second step of calcination is 860℃, the residence time is 12h, and the heating rate is 10℃ / min. After sieving the calcined material, the primary regenerated positive electrode active material is obtained.

[0065] (6) According to the stoichiometric ratio of the target product, the primary regenerated positive electrode active material is added to a high-pressure reactor containing a mixed solution of tetraethoxysilane and triethyl phosphate in a specific molar amount. The reaction is first carried out at 160°C for 2.5 h, and then the temperature is raised to 280°C and the reaction is continued for 4.8 h. The reaction product is filtered, dried, and then calcined at 410°C for 4 h under a nitrogen atmosphere to obtain a regenerated positive electrode active material.

[0066] Comparative Example 1

[0067] The difference between this comparative example and Example 1 is that step (6) is omitted, and the chemical formula of the prepared regenerated cathode material is LiNi. 0.55 Co 0.199 Mn 0.246 Ta 0.005 O2.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 1 is that the waste cathode material is simultaneously added to a mixed solution of 2-hydroxypropionic acid, aspartic acid, ascorbic acid, and tyrosine during the leaching process, i.e., a one-step reaction is used to obtain the leachate:

[0070] A mixed solution was prepared by adding 55g of 2-hydroxypropionic acid, 2g of aspartic acid, 20g of ascorbic acid, and 1g of tyrosine to 7.8L of deionized water. 500g of LiNi... 0.55 Co 0.199 Mn 0.248 Ta 0.003Waste lithium-ion battery cathode material containing O2 was added to the above mixed solution and reacted at a temperature of 45°C for 1.2 hours with a stirring speed of 350 r / min. A black turbid liquid was obtained. The black turbid liquid was filtered to remove the filter residue (a large amount of filter residue indicates that a large amount of waste lithium-ion cathode material remained undissolved; the mass of the filter residue was 20 to 50 times that of Example 1), thus obtaining a leachate rich in valuable metal ions.

[0071] The other steps are the same as in Example 1, and the chemical formula of the prepared regenerated positive electrode active material is LiNi. 0.55 Co 0.199 Mn 0.246 Ta 0.005 O2·0.002Ti3(PO4)4.

[0072] The positive electrode materials prepared in Example 1 and Comparative Examples 1-2 were respectively added to acetylene black and polyvinylidene fluoride (PVDF), mixed evenly, and then ground into a uniform slurry. The slurry was coated onto aluminum foil to form a positive electrode. A coin cell lithium-ion battery was made using lithium metal sheet as the negative electrode and LiPF6 as the electrolyte. The electrochemical test voltage was 4.3V.

[0073] Figure 2 The graphs show the cycling curves of the lithium-ion batteries prepared in Example 1 and Comparative Examples 1-2 at 10C rate and 45°C. Figure 2 As can be seen, the lithium-ion battery prepared in Example 1 has an initial discharge specific capacity of 157.5 mAh / g, and after 50 cycles, the discharge specific capacity is still as high as 153 mAh / g, with a capacity retention rate of 97.1%. However, the lithium-ion battery prepared in Comparative Example 1 has a capacity retention rate of only 93%, and the lithium-ion battery prepared in Comparative Example 2 has a capacity retention rate of only 90.8%.

[0074] In summary, this application organically combines the recycling of valuable metals from waste lithium-ion batteries with the preparation of cathode materials. A one-step sol-gel method is used to crosslink metal ions to regenerate new cathode active materials. During the regeneration process, the modifying elements are fully utilized to dope and modify the regenerated cathode active materials. In the later stage of the regeneration process, a solvothermal method is used to coat the primary regenerated cathode active materials, making the material structure more stable. The regenerated cathode active materials prepared have high crystallinity and excellent electrochemical performance.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A method for preparing a regenerated positive electrode active material, characterized in that, Includes the following steps: Waste lithium-ion battery cathode material is added to an aqueous solution of 2-hydroxypropionic acid and / or aspartic acid for the first reaction; A second reaction was carried out by adding an aqueous solution of ascorbic acid and / or tyrosine to the system after the first reaction at a certain flow rate, resulting in a black turbid liquid; The resulting black turbid liquid was filtered to remove residue, yielding a leachate rich in valuable metal ions. Adjusting the valence metal ions and M in the leachate n+ The molar ratio is adjusted, pH is adjusted, and the mixture is heated, evaporated, and concentrated to form a gel-like substance; The gel-like material is subjected to two-step calcination in an oxygen or air atmosphere to obtain a primary regenerated positive electrode active material; wherein, the temperature of the first calcination step is 300℃~450℃, the residence time is 2h~12h, and the heating rate is 1℃ / min~10℃ / min; the temperature of the second calcination step is 550℃~900℃, the residence time is 1h~15h, and the heating rate is 5℃ / min~20℃ / min; The primary regenerated positive electrode active material is added to a solution containing a coating agent for a solvothermal reaction, dried, and then sintered at low temperature to obtain the regenerated positive electrode active material. The valuable metal ions include Ni. 2+ Co 2+ Mn 2+ Li + and M n+ M is one or more of W, Zr, Al, Sr, Nb, and Ta, and n is 2, 3, 5, or 6; the coating agent includes a coating precursor and a phosphorus compound, wherein the coating precursor is one of tetraethoxysilane, ethoxysilane, titanium ethoxide, titanium tetraethoxysilane, titanium tetraethoxyacetate, vanadium acetate, vanadium triisopropoxide, vanadium ethoxide, and vanadium tert-butoxide; and the phosphorus compound is one of triethyl phosphate, trimethyl phosphate, trialkyl phosphate, and potassium dihydrogen phosphate.

2. The preparation method according to claim 1, characterized in that, The chemical formula of the regenerated positive electrode active material is Li. k Ni x Co y Mn z M m O2·sT3(PO4)4, where x:y:z:m=(0.10~0.85):(0.05~0.20):(0.10~0.35):(0.001~0.1), and x+y+z+m=1, 0.95≤k≤1.15, 0<s≤0.05; T is one of Ti, Si, and V.

3. The preparation method according to claim 1, characterized in that, The general chemical formula of the cathode material of the waste lithium-ion battery is LiNi. x Co y Mn z M m O2, where x:y:z:m=(0~1):(0~1):(0~1):(0.001~0.1), and x, y, and z are not all 0 at the same time.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the 2-hydroxypropionic acid and / or aspartic acid to the mass of the waste lithium-ion battery cathode material is (5-50):(50-95); the temperature of the first reaction is 30-70℃, the time is 0.1-1h, and the stirring speed is 200-600r / min.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the ascorbic acid and / or tyrosine to the mass of the waste lithium-ion battery cathode material is 5~500:1000; the temperature of the second reaction is 30-55℃, the time is 0.1-1h, and the stirring speed is 300-800r / min.

6. The preparation method according to claim 1, characterized in that, The pH is adjusted to 6.5~7.5, and the heating temperature is 40~90℃.

7. The preparation method according to claim 1, characterized in that, The temperature of the solvothermal reaction is 100~300℃, and the total time is 4-8h; The solvothermal reaction includes two stages, with the temperature ratio of the first stage to the second stage being 1:(1~2) and the holding time ratio of the first stage to the second stage being 1:(1~2). The low-temperature sintering treatment is performed at a temperature of 300~450℃ for 2-6 hours.

8. A regenerated positive electrode active material, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

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