Recycling method of lithium battery positive electrode active material

Abstract

The invention provides a lithium ion battery positive electrode active material recovery method, which comprises: roasting a lithium ion battery positive electrode active material and an additive, carrying out water leaching, treating the water leaching liquid by using a bipolar membrane system to obtain lithium hydroxide monohydrate solid powder, and carrying out an acid leaching co-precipitation reaction on the water leaching residue to obtain a positive electrode active material precursor, compared with a traditional mode of recycling lithium-containing aqueous immersion liquid in a lithium carbonate mode, the lithium hydroxide prepared by the method is high in purity and can be directly used for preparing a high-nickel positive electrode material. Besides, heavy metal ions such as nickel, cobalt and manganese are obtained through one-step coprecipitation in the form of precursors, the complex step of extracting each metal through multiple extraction agents in a traditional wet process is omitted, and the whole technological process is simplified and more environmentally friendly.

Description

Technical Field

[0001] The present disclosure relates to the technical field of lithium battery materials, and in particular to a method for recovering positive electrode active materials of lithium batteries. Background Art

[0002] Lithium batteries have the characteristics of high energy density, high coulombic efficiency and long cycle life, making them the main power source for portable electronic products and electric vehicles. It is expected that the global manufacturing capacity of lithium-ion batteries will increase significantly at a rate of hundreds of GWh per year in the next five years. Among them, the nickel-cobalt-manganese ternary positive electrode materials for automobiles will generate greater demand for raw materials as the electric vehicle market grows. Lithium-ion batteries usually reach the end of their life after 3 to 6 years. Scrapped ternary lithium-ion batteries contain a large amount of Li, Co, Ni, Mn and other resources. Waste lithium-ion batteries are not only a source of garbage pollution, but their heavy metal elements will cause great soil, water and air pollution if directly exposed to the natural environment. The recycling of scrapped lithium battery materials can effectively supplement the supply chain, make full use of metal material resources, and avoid waste and loss.

[0003] The current recycling process is mainly based on hydrometallurgy, which extracts valuable metals through acid dissolution, impurity removal and extraction processes, and lithium is precipitated in the mother liquor to form lithium carbonate. This process requires a large amount of strong acid leaching and strong alkali neutralization and impurity removal. The extraction process uses an extractant with high cost and carbon emissions, and the cumbersome process will cause serious loss of lithium. Summary of the invention

[0004] In view of the problems existing in the prior art, the present disclosure aims to provide an environmentally friendly, simple process flow and low-cost lithium-ion battery positive electrode active material recovery solution.

[0005] The present invention provides a method for recovering positive electrode active materials of a lithium ion battery, comprising the following steps:

[0006] S1: mixing the positive electrode active material of the lithium ion battery with the additive and then calcining to obtain a calcined product;

[0007] S2: soaking the roasted product in water to obtain a water soaking liquid and a water soaking residue;

[0008] S3: treating the water extract with a bipolar membrane system to obtain a lithium hydroxide solution, and concentrating and crystallizing the lithium hydroxide solution to obtain a lithium hydroxide monohydrate solid powder;

[0009] S4: mixing the water-leached residue with sulfuric acid to obtain a sulfate solution, adjusting the ratio of at least one of the nickel salt, the cobalt salt, and the manganese salt according to a stoichiometric ratio, and obtaining a positive electrode active material precursor through a supergravity synthesis reaction.

[0010] The present invention provides a method for recovering positive active materials of lithium ion batteries, wherein the positive active materials of lithium ion batteries and additives are roasted and then soaked in water, and the water leaching liquid is treated by a bipolar membrane system to obtain a solid powder of lithium hydroxide monohydrate (i.e., LiOH·H2O), and the water leaching residue is acid-leached and subjected to a supergravity synthesis reaction to obtain a positive active material precursor. Compared with the traditional method of recovering lithium-containing water leaching liquid in the form of lithium carbonate, the final product prepared by the present invention is lithium hydroxide, which can be directly used for the preparation of high-nickel positive electrode materials. In addition, heavy metal ions such as nickel, cobalt, and manganese are obtained in the form of precursors through a one-step supergravity synthesis reaction, eliminating the complex steps of using multiple extractants to extract each metal separately in the traditional wet process, and the entire process flow is simplified and more environmentally friendly. Moreover, through a rapid microscopic mixing reaction, the transition metal salt ions and the alkali solution are rapidly and uniformly mixed on a microscopic scale, which is conducive to the production of precursor particles with uniform components. Compared with the existing synthesis method, the mixing time and reaction time are greatly shortened, which meets the needs of industrial large-scale production.

[0011] Furthermore, in the step S1, the additive includes sulfuric acid and at least one of vitamin C, glucose, chitosan, gallic acid and amino acids.

[0012] Compared with the traditional method of extracting lithium by roasting waste lithium-ion battery positive electrode active materials with sulfuric acid, the roasting additives of the present invention select reducing additives such as vitamin C, glucose, chitosan and gallic acid, and amino acids can greatly reduce the temperature of traditional acid roasting.

[0013] Furthermore, in the step S1, the molar ratio of the lithium-ion battery positive electrode active material to the additive is 0.05:1 to 5:1, preferably 2:1 to 3:1.

[0014] Furthermore, in step S1, the calcination temperature is 500° C. to 700° C., and the calcination atmosphere is an inert gas, preferably, the calcination atmosphere is nitrogen.

[0015] The calcination process causes a phase change in the crystal structure of the positive electrode material. The additives promote the release of lithium ions from the structure and their conversion into water-soluble sulfates. Nickel, cobalt, and manganese exist in the form of insoluble metal oxides. Choosing the appropriate calcination temperature and the amount of additives affects the selective extraction rate of lithium elements, thereby improving the recovery rate of lithium metal.

[0016] Furthermore, before the step S3, a de-impurity step is also included, and the de-impurity step includes adjusting the pH of the water leaching solution to 10-12 using a lithium hydroxide solution, separating the precipitated residue, and obtaining a lithium sulfate solution.

[0017] Furthermore, the impurity removal step further comprises removing impurities from the lithium sulfate solution by resin adsorption. Preferably, the resin is selected from a chelating resin and / or an ion exchange resin, wherein at least one of the chelating resin and the ion exchange resin satisfies at least one of the following conditions:

[0018] (1) The particle size of at least one of the chelating resin and the ion exchange resin is 0.3 mm to 1.25 mm;

[0019] (2) The resin adsorption rate is 1BV / h to 3BV / h;

[0020] The present invention utilizes a two-step impurity removal process, namely, removing divalent and above metal cations (such as Ca, Mg, Ni, Co, Mn, etc.) by controlling the pH value range through chemical coagulation precipitation, and further subjecting the precipitated liquid to deep impurity removal through resin adsorption, especially removing fluorine element and residual metal ions therein, thereby obtaining a high-purity lithium sulfate solution with extremely low impurity content.

[0021] The bipolar membrane system treatment includes electrodialysis concentration treatment and bipolar membrane conversion treatment, and the electrodialysis concentration treatment satisfies at least one of the following conditions:

[0022] (1) The single membrane voltage of the electrodialysis concentration treatment is 1.2V to 1.5V;

[0023] (2) The rated current range of the electrodialysis concentration treatment is 1.1A to 6.6A;

[0024] and / or,

[0025] The bipolar membrane conversion process satisfies at least one of the following conditions:

[0026] (1) The voltage of a single membrane group in the bipolar membrane conversion treatment is 3V to 3.5V;

[0027] (2) The rated current of the bipolar membrane conversion process is 3A to 4.4A.

[0028] The lithium content is increased through electrodialysis concentration treatment to form a high-concentration lithium sulfate solution, which is used for subsequent bipolar membrane conversion treatment to obtain lithium hydroxide solution and sulfuric acid. The prepared lithium hydroxide has extremely high purity.

[0029] Furthermore, the S4 step includes mixing the sulfate solution and alkali solution and adding the mixture into a high-gravity reactor to obtain a positive electrode active material precursor through a high-gravity synthesis reaction, wherein the alkali solution includes at least one of sodium hydroxide and ammonia water.

[0030] Furthermore, in step S4, at least one of the following conditions is satisfied:

[0031] (1) The high gravity synthesis reaction temperature is 50°C to 60°C;

[0032] (2) The pH of the high gravity synthesis reaction is 9 to 11;

[0033] The innovative method for recovering positive active materials of lithium-ion batteries provided by the present invention has mild process conditions, simplified process steps, and uses two impurity removal steps. The recovered lithium hydroxide has high purity and can be directly used for the preparation of high-nickel positive electrode materials. Compared with the existing synthesis methods, the ultra-gravity synthesis reaction greatly shortens the mixing time and reaction time, which meets the needs of industrial large-scale production.

[0034] Furthermore, the method further comprises: sintering the positive electrode active material precursor with a lithium salt to obtain a lithium-supplemented positive electrode active material for a lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The process flow chart of recycling positive electrode active materials of a lithium-ion battery provided in Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present disclosure clearer, the technical solution of the present disclosure will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. The relevant embodiments described herein are illustrative and are used to provide a basic understanding of the present disclosure. The embodiments of the present disclosure should not be interpreted as limiting the present disclosure.

[0037] The present invention provides a method for recovering positive electrode active materials of a lithium ion battery, comprising the following steps:

[0038] S1: mixing the positive electrode active material of the lithium ion battery with the additive and then calcining to obtain a calcined product;

[0039] S2: soaking the roasted product in water to obtain a water soaking liquid and a water soaking residue;

[0040] S3: treating the water extract with a bipolar membrane system to obtain a lithium hydroxide solution, and concentrating and crystallizing the lithium hydroxide solution to obtain a lithium hydroxide monohydrate solid powder;

[0041] S4: mixing the water-leached residue with sulfuric acid to obtain a sulfate solution, adjusting the ratio of at least one of the nickel salt, the cobalt salt, and the manganese salt according to a stoichiometric ratio, and obtaining a positive electrode active material precursor through a supergravity synthesis reaction.

[0042] In some embodiments of the present invention, in step S2, the roasted product is added to deionized water for water leaching to obtain a water leaching liquid and water leaching residue.

[0043] In some embodiments of the present invention, the lithium-ion battery positive electrode active material includes one or more of lithium transition metal oxides and modified compounds thereof.

[0044] In some embodiments of the present invention, the lithium ion battery positive electrode active material is selected from lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium manganese cobalt oxide, and a general formula of LiNi x Co y At least one oxide of M(1-xy)O2 material, and one or more modified compounds of the above oxides, wherein M is selected from at least one of Mn, Al, Mg, Cr, Ca, Zr, Mo, Ag, and Nb, 0≤x<1, 0.1≤y≤1, and 0.6≤x+y≤1.

[0045] In some embodiments of the present invention, the positive electrode active material of the lithium ion battery used in the recycling method of the present invention is obtained by the following steps: discharging the waste lithium ion battery and disassembling the waste lithium ion battery into three parts, namely ① shell and diaphragm, etc.; ② positive electrode sheet of the waste lithium battery and ③ negative electrode sheet of the waste lithium battery; wherein ① shell and diaphragm, etc. and ③ negative electrode sheet of the waste lithium battery are recycled and processed by other methods. The positive electrode sheet obtained by ② is placed in a muffle furnace, and after pyrolysis at 400°C under nitrogen conditions, optionally, the pyrolysis product is passed through a 100-mesh sieve to obtain the sieve-under product as the positive electrode active material of the lithium ion battery to be recycled.

[0046] In some embodiments of the present invention, the additive includes sulfuric acid and at least one of vitamin C, glucose, chitosan, gallic acid and amino acids, for example, vitamin C.

[0047] In some embodiments of the present invention, the molar ratio of the lithium ion battery positive electrode active material to the additive is 0.05:1 to 5:1. In some embodiments of the present invention, the molar ratio of the lithium ion battery positive electrode active material to the additive is 2:1 to 3:1.

[0048] In some embodiments of the present invention, in the step S1, the calcination temperature is 500°C to 700°C, and the calcination atmosphere is an inert gas. In some embodiments of the present invention, the calcination temperature is 550°C to 650°C, and the calcination atmosphere is nitrogen.

[0049] In some embodiments of the present invention, the process of mixing the positive electrode active material of the lithium ion battery with the additive in the step S1 includes: mixing the positive electrode active material of the lithium ion battery with deionized water, beating and soaking, adding vitamin C, stirring until the mixture is uniform, and gradually adding concentrated sulfuric acid (98%) during the stirring process. The mixture is placed in a muffle furnace and dried at 120°C, and the dried powder is stirred and mixed for the second time with a mixer, and the obtained mixture is used for subsequent roasting treatment.

[0050] In some embodiments of the present invention, a de-impurity step is further included before the S3 step, and the de-impurity step includes adjusting the pH of the water leaching solution to 10-12 using a lithium hydroxide solution, separating the precipitated residue, and obtaining a lithium sulfate solution.

[0051] In some embodiments of the present invention, the impurity removal step further comprises passing the lithium sulfate solution through a chelating resin and / or an ion exchange resin, wherein at least one of the chelating resin and / or the ion exchange resin satisfies at least one of the following conditions:

[0052] (1) The particle size of at least one of the chelating resin and the ion exchange resin is 0.3 mm to 1.25 mm, and further, the particle size is 0.9 mm;

[0053] (2) The resin adsorption rate is 1BV / h to 3BV / h.

[0054] The resin mentioned in the present invention has good adsorption effect on heavy metal ions, calcium ions, magnesium ions, etc., and is very efficient for removing impurities. The resin generally used is a chelating resin or an ion exchange resin. The atoms on the functional groups of the chelating resin react with the metal ions to produce coordinated covalent bonds, forming a chelate with stable structure, and the adsorption performance is relatively stable. The ion exchange resin utilizes electrostatic action to combine with metal ions, and the ion exchange resin performs exchange adsorption. When the resin is saturated with adsorption, acid elution and alkali regeneration treatment are performed to restore the activity of the resin. Generally, the ion exchange resin is a sodium type. In order to avoid the introduction of sodium ions into the system, it is generally used for removing impurities in lithium-containing solutions after being washed with a lithium solution after activation to convert the resin into a lithium type resin.

[0055] The resin is usually loaded into a cylindrical resin column for the solution to pass through continuously. The volume of the resin loaded in the resin column is called the bed volume, abbreviated as BV. If the flow rate of the solution through the resin column is 2BV / h~4BV / h, the volume of the solution passing through per hour is 2~4 times the resin bed volume.

[0056] In some embodiments of the present invention, in the step S3, the bipolar membrane system treatment includes electrodialysis concentration treatment and bipolar membrane conversion treatment. In some embodiments of the present invention, the voltage of a single pair of membranes in the electrodialysis concentration treatment is 1.2V to 1.5V, and the voltage is too high to easily break through the membrane. The rated current range of the electrodialysis concentration treatment is 1.1A to 6.6A. In some embodiments of the present invention, a total of ten pairs of membranes are used in the electrodialysis concentration treatment, and the total voltage is 12V to 15V at this time; in some embodiments of the present invention, the device for bipolar membrane conversion treatment is a three-chamber bipolar membrane device. Specifically, it includes a bipolar membrane, an anion exchange membrane and a monovalent cation exchange membrane, which constitute a salt chamber, an acid chamber and an alkali chamber; the anion exchange membrane and the monovalent cation exchange membrane are paired. The lithium sulfate solution after impurity removal and concentration enters the salt chamber in the three-chamber bipolar membrane device for bipolar membrane conversion treatment, and finally outputs lithium hydroxide solution from the alkali chamber, outputs salt solution from the salt chamber, and outputs acid solution, i.e. sulfuric acid, from the acid chamber. In some embodiments, in the bipolar membrane conversion treatment, the voltage setting of a single set of membranes for the bipolar membrane conversion treatment is 3V to 3.5V, and the rated current of the bipolar membrane conversion treatment is 1.1A to 6.6A. In some embodiments of the present invention, a total of ten sets of membranes are used for the bipolar membrane conversion treatment, and the voltage setting is 30V to 35V. The use of bipolar membrane conversion treatment to prepare lithium hydroxide can promote water dissociation, because there is no electrode reaction and no redox reaction is produced, and no by-products are produced, thereby preparing lithium hydroxide with extremely high purity. At the same time, this step also includes the product sulfuric acid, which can be recycled, for example, it can be used for subsequent acid leaching of water-leached residues, realizing the recycling of intermediate products.

[0057] The present invention has no special restrictions on the materials of the bipolar membrane, anion exchange membrane and monovalent cation exchange membrane, and the materials of the bipolar membrane, anion exchange membrane and monovalent cation exchange membrane well known to those skilled in the art can be used.

[0058] In some embodiments of the present invention, the S4 step includes mixing a sulfate solution and an alkali solution and adding the mixture to a high-gravity reactor to obtain a positive electrode active material precursor through a high-gravity synthesis reaction, wherein the alkali solution includes at least one of sodium hydroxide and ammonia water.

[0059] In some embodiments of the present invention, the high-gravity synthesis reaction temperature in step S4 is 50° C. to 60° C.; the high-gravity synthesis reaction pH is 10.0 to 11.0.

[0060] In some embodiments of the present invention, the cathode active material precursor is sintered with a lithium salt to obtain a lithium-supplemented cathode active material for a lithium-ion battery.

[0061] The present disclosure is further described below in conjunction with the examples. It should be understood that these examples are only used to illustrate the present disclosure and are not used to limit the scope of the present disclosure.

[0062] In order to facilitate the description of the recycling method of the present invention, the lithium ion batteries selected in the embodiment are all ternary lithium ion batteries, specifically NCM523, that is, the batteries used meet the requirements of LiNi 0.5 Co 0.2 Mn 0.3 The recycling method of the present invention is also applicable to the recycling of other positive electrode active materials, such as lithium transition metal oxides and modified compounds thereof, specifically, ternary lithium ion batteries such as Ni55, NCM523, and NCM811.

[0063] Embodiment 1:

[0064] S1: Calcination of ternary cathode active materials and additives

[0065] The ternary positive electrode active material was mixed with vitamin C at a molar ratio of 2:1, and concentrated sulfuric acid was added to the mixture, and the mixture was placed in a muffle furnace, heated to 500°C at a rate of 5°C / min and kept warm for 3 hours in a nitrogen atmosphere, and the calcined product was obtained after natural cooling. The calcined product was crushed through a 200-mesh sieve, and the treated calcined product was taken for the next step.

[0066] S2: Water immersion of roasted product and two-step impurity removal

[0067] The treated calcined product is immersed in deionized water and stirred at room temperature, and the solid-liquid ratio of the calcined product to deionized water is 1:2. The water infusion and the water infusion residue are then filtered and separated, and the water infusion residue is dried to obtain nickel cobalt manganese oxide. A lithium hydroxide solution with a concentration of 4.19% is added to the water infusion until the pH is equal to 11, and the precipitated residue is filtered and separated to obtain a lithium sulfate solution after preliminary impurity removal. The lithium sulfate solution after preliminary impurity removal is further impurity-removed by a chelating resin and an ion exchange resin (lithium type resin column), the resin particle size is 0.9 mm, and the flow rate is 2BV / h, to obtain a lithium sulfate water infusion after impurity removal.

[0068] S3: Bipolar membrane system treatment

[0069] The impurity-removed lithium sulfate water infusion obtained in S2 is subjected to electrodialysis concentration treatment, and the concentrated lithium sulfate concentrate is introduced into a bipolar membrane device for bipolar membrane conversion treatment. The bipolar membrane conversion treatment voltage is set to 3.2V, and the bipolar membrane conversion treatment current is 4.4A to obtain a lithium hydroxide solution. The lithium hydroxide solution is introduced into a rotary evaporator, and after rotary evaporation concentration and crystallization, a lithium hydroxide monohydrate solid powder can be obtained.

[0070] S4: Impurity removal and preparation of nickel-cobalt-manganese precursor

[0071] The nickel-cobalt-manganese oxide obtained in step S2 is added to 2M sulfuric acid to obtain a nickel-cobalt-manganese salt leachate, and a soluble sulfate (NiSO4, CoSO4, MnSO4) is added according to the stoichiometric ratio of Ni:Co:Mn=8:1:1 to adjust the ratio of nickel salt, cobalt salt and manganese salt, and deionized water is added to control the metal ion concentration in the mixed solution to 2M. Sodium hydroxide is added to the nickel-cobalt-manganese salt leachate to adjust the pH to 5, and a filtrate is obtained by filtering, and the pH of the filtrate is adjusted to about 7, and a filtrate is obtained by filtering and the filtrate is deeply impurized by a chelating resin to obtain a nickel-cobalt-manganese sulfate solution. The obtained nickel-cobalt-manganese sulfate solution after impurity removal, sodium hydroxide and ammonia water are mixed, wherein the NaOH concentration is 2mol / L and the ammonia concentration is 0.5mol / L, and the mixed solution is poured into a supergravity reactor with a flow rate of less than 1L / min. The speed of the supergravity reactor is adjusted to 2500rpm, the temperature is 50°C, and the pH is adjusted to between 9 and 11. After the reaction, the reaction products in the ultra-gravity reactor are collected, and after washing and drying, a nickel-cobalt-manganese ternary positive electrode active material precursor is obtained.

[0072] Table 1 Content of each element in the solution at different stages of the recovery method of Example 1 (ppm)

[0073]

[0074] Embodiment 2:

[0075] The difference from Example 1 is that the calcination temperature used is 550°C.

[0076] Table 2: Content of each element in the solution at different stages of the recovery method of Example 2 (ppm)

[0077]

[0078]

[0079] Embodiment 3:

[0080] The difference from Example 1 is that the calcination temperature used is 650°C.

[0081] Table 3: Content of each element in the solution at different stages of the recovery method of Example 3 (ppm)

[0082]

[0083] Embodiment 4:

[0084] The difference from Example 1 is that the calcination temperature used is 500°C.

[0085] Table 4: Content of each element in the solution at different stages of the recovery method of Example 4 (ppm)

[0086]

[0087]

[0088] Embodiment 5:

[0089] The difference from Example 1 is that the molar ratio of the ternary positive electrode active material to nickel sulfate is 2:0.8, and the calcination temperature is 550°C.

[0090] Table 5: Content of each element in the solution at different stages of the recovery method of Example 5 (ppm)

[0091]

[0092] The results of Examples 1 to 5 show that increasing the roasting temperature is conducive to obtaining a higher lithium recovery rate, and the lithium sulfate solution after two-step impurity removal contains almost no impurity elements or the impurity element content is reduced to a very low level, indicating that this method has a high impurity removal effect and is conducive to obtaining lithium hydroxide with a higher purity.

[0093] Test method:

[0094] ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer) element content test:

[0095] Place a certain amount of the sample to be tested in a digestion container, add an acid solution (such as hydrochloric acid, nitric acid or sulfuric acid), seal it, and heat and digest it in a microwave digester or oven. After the digestion is completed, transfer the digestion solution to a volumetric flask and perform the volume adjustment and shake steps. Use ICP-OES equipment to test the trace element content of the digestion solution. For liquid phase samples such as leaching solutions, use ICP-OES equipment to test the trace element content of the digestion solution after dilution.

[0096] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present disclosure, and that changes, substitutions and modifications may be made to the embodiments without departing from the spirit, principles and scope of the present disclosure.

Claims

1. A method for recovering positive electrode active materials of lithium ion batteries, characterized in that: The method comprises: S1: mixing the lithium-ion battery positive electrode active material with the additive and then calcining to obtain a calcined product; S2: soaking the roasted product in water to obtain a water soaking liquid and a water soaking residue; S3: treating the water extract with a bipolar membrane system to obtain a lithium hydroxide solution, and concentrating the lithium hydroxide solution to obtain a lithium hydroxide monohydrate solid powder; S4: mixing the water-leached residue with sulfuric acid to obtain a sulfate solution, adjusting the ratio of at least one of nickel salt, cobalt salt and manganese salt in the sulfate solution according to a stoichiometric ratio, and obtaining a positive electrode active material precursor through a supergravity synthesis reaction.

2. The method according to claim 1, characterized in that In the step S1, at least one of the following conditions is met: (1) The additive comprises sulfuric acid and at least one of vitamin C, glucose, chitosan, gallic acid and amino acid; (2) The molar ratio of the lithium ion battery positive electrode active material to the additive is 0.05:1 to 5:1; (3) The calcination temperature is 500° C. to 700° C.; (4) The calcination atmosphere is an inert gas.

3. The method according to claim 2, characterized in that At least one of the following conditions is met: (1) The molar ratio of the lithium ion battery positive electrode active material to the additive is 2:1 to 3:1; (2) The calcination atmosphere is nitrogen.

4. The method according to claim 1, characterized in that Before the step S3, a de-impurity step is also included, and the de-impurity step includes adjusting the pH of the water leaching solution to 10-12 using a lithium hydroxide solution, separating the precipitated residue, and obtaining a lithium sulfate solution.

5. The method according to claim 4, characterized in that The impurity removal step further comprises removing impurities from the lithium sulfate solution by resin adsorption, wherein the resin satisfies at least one of the following conditions: (1) The resin comprises particles having a particle size of 0.3 mm to 1.25 mm; (2) The adsorption rate of the resin is 1 BV / h to 3 BV / h; (3) The resin is a chelating resin or an ion exchange resin.

6. The method according to claim 1, characterized in that In the step S3, the bipolar membrane system treatment includes an electrodialysis concentration treatment and a bipolar membrane conversion treatment, and the electrodialysis concentration treatment satisfies at least one of the following conditions: (1) The single membrane voltage of the electrodialysis concentration treatment is 1.2V to 1.5V; (2) The rated current of the electrodialysis concentration treatment is 1.1A to 6.6A; and / or, The bipolar membrane conversion process satisfies at least one of the following conditions: (1) The voltage of a single membrane group in the bipolar membrane conversion treatment is 3V to 3.5V; (2) The rated current of the bipolar membrane conversion process is 3A to 4.4A.

7. The method according to claim 1, characterized in that In the step S4, the sulfate solution and the alkali solution are mixed and then subjected to a supergravity synthesis reaction in a supergravity reactor to obtain a positive electrode active material precursor, wherein the alkali solution includes at least one of sodium hydroxide and ammonia water.

8. The method according to claim 7, characterized in that In the step S4, at least one of the following conditions is met: (1) The high gravity synthesis reaction temperature is 50°C to 60°C; (2) The pH of the supergravity synthesis reaction is 9-11.

9. The method according to claim 1, characterized in that The method further comprises: sintering the positive electrode active material precursor with a lithium salt to obtain a lithium-supplemented positive electrode active material for a lithium-ion battery.

10. A method for recovering positive electrode active materials of lithium ion batteries, characterized in that: The method comprises: (s1) mixing the positive electrode active material of the lithium ion battery with the additive, heating to 500° C. to 600° C. and keeping the temperature in a nitrogen atmosphere, and naturally cooling to obtain a calcined product; (s2) immersing the calcined product in deionized water at room temperature and stirring to obtain a water leaching liquid and a water leaching residue; (s3) adding lithium hydroxide solution to the water extract to adjust the pH to 10-11, filtering and separating the precipitated residue to obtain a lithium sulfate solution; (s4) passing the lithium sulfate solution through a chelating resin or an ion exchange resin to obtain a lithium sulfate solution after impurities are removed, wherein the resin particles have a particle size of 0.9 mm to 1 mm and the resin adsorption rate is 1 BV / h to 3 BV / h; (s5) treating the impurity-removed lithium sulfate solution with a bipolar membrane system to obtain a lithium hydroxide solution, wherein the bipolar membrane system treatment includes a bipolar membrane conversion treatment, wherein the voltage of a single membrane group in the bipolar membrane conversion treatment is 3V to 3.5V, and the rated current of the bipolar membrane conversion treatment is 3A to 4.4A; (s6) The water-leached residue described in step s2 is leached with sulfuric acid to obtain a nickel-cobalt-manganese salt leachate, sodium hydroxide is added to adjust the pH to 5-6, and a filtrate is obtained by filtering, and the pH of the filtrate is then increased to 7-8, and the filtrate is obtained by filtering and then removing impurities with a chelating resin to obtain a nickel-cobalt-manganese sulfate solution. (s7) The nickel-cobalt-manganese sulfate solution and an alkaline solution including sodium hydroxide and ammonia water are mixed and added into a high-gravity reactor, wherein the temperature of the high-gravity reactor is 50° C. to 60° C. and the pH is 9 to 11, and a high-gravity synthesis reaction is performed to obtain a nickel-cobalt-manganese positive electrode active material precursor.

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