Recycling method of lithium battery positive electrode active material

Abstract

The invention provides a recovery method of a lithium ion battery positive electrode active material, which comprises the following steps: roasting the lithium ion battery positive electrode active material and an additive, performing water immersion, and treating the water immersion liquid by using a bipolar membrane system to obtain lithium hydroxide monohydrate solid powder; meanwhile, the water leaching residues are subjected to an acid leaching coprecipitation reaction to obtain a positive electrode active material precursor, and compared with a traditional mode that lithium-containing water leaching liquid is recycled in a lithium carbonate mode, lithium hydroxide prepared through the method is high in purity and can be directly used for preparing a high-nickel positive electrode active 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 active 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 coprecipitation reaction.

[0010] The present invention provides a method for recovering positive active materials of lithium-ion batteries. The positive active materials of lithium-ion batteries and additives are roasted and then immersed in water. The water leaching liquid is treated with a bipolar membrane system to obtain a solid powder of lithium hydroxide monohydrate (i.e., LiOH·H2O). At the same time, the water leaching residue is subjected to an acid leaching coprecipitation 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 active materials. In addition, heavy metal ions such as nickel, cobalt, and manganese are obtained in the form of precursors through a one-step coprecipitation, which eliminates the complex steps of using multiple extractants to extract each metal separately in the traditional wet process, and the entire process is simplified and more environmentally friendly.

[0011] Furthermore, in the step S1, the additive includes at least one of nickel sulfate, cobalt sulfate and manganese sulfate.

[0012] Compared with the traditional method of extracting lithium by roasting the positive active material of waste lithium-ion batteries with sulfuric acid, the roasting additive of the present invention uses sulfates, such as nickel sulfate, cobalt sulfate, and manganese sulfate, which can greatly reduce the temperature of the traditional acid roasting on the one hand, and avoid the equipment cost and pollutant emission of the acid roasting on the other hand. In addition, the metal salt ions introduced into the sulfate substance can be recycled together with the heavy metal salt ions in the positive active material of the waste lithium-ion battery through the subsequent recycling step, realizing the closed loop of the material flow of the additive material, and improving the recycling rate of the roasting additive.

[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 air.

[0015] The calcination process causes a phase change in the crystal structure of the positive electrode active material. The additive promotes 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. The selection of appropriate calcination temperature and the amount of sulfate additives affect the selective extraction rate of lithium elements. The impurity content in the resulting water leaching solution is low, and the lithium recovery rate can be improved.

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

[0019] (b) 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.) through chemical coagulation precipitation by controlling the pH value range, and further subjecting the precipitated liquid to deep impurity removal through resin adsorption, especially removing fluorine elements and residual metal ions therein, thereby obtaining a high-purity lithium sulfate solution with extremely low impurity content, and the lithium content is increased through electrodialysis purification and concentration to obtain a high-concentration lithium sulfate solution, which is used for subsequent bipolar membrane conversion treatment to obtain a lithium hydroxide solution and sulfuric acid, and the prepared lithium hydroxide has extremely high purity.

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

[0023] (e) 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] (f) The voltage of a single membrane group in the bipolar membrane conversion treatment is 3V to 3.5V;

[0027] (g) The rated current of the bipolar membrane conversion process is 3A to 5A.

[0028] Furthermore, the S4 step includes mixing the sulfate solution, the precipitant and the complexing agent, and obtaining a positive electrode active material precursor through a coprecipitation reaction, wherein the precipitant includes sodium hydroxide, preferably, the precipitant is a mixture of sodium hydroxide and deionized water, and the complexing agent includes ammonia water.

[0029] Furthermore, in step S4, at least one of the following conditions is satisfied:

[0030] (h) carrying out the coprecipitation reaction under the protection of an inert gas, preferably, the inert gas is nitrogen;

[0031] (i) the coprecipitation reaction temperature is 50°C to 60°C;

[0032] (j) the coprecipitation reaction pH is 10 to 12;

[0033] (k) The concentration of the complexing agent is 5 g / L to 6 g / L.

[0034] The innovative method for recovering positive electrode active materials of lithium-ion batteries provided by the present invention has mild process conditions and simplified process steps, while avoiding the use of pollution source additives such as sulfuric acid. In addition, two impurity removal steps are used, and the lithium hydroxide recovered by the bipolar membrane system treatment has high purity and can be directly used for the preparation of high-nickel positive electrode active materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A process flow chart for 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 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 coprecipitation reaction.

[0042] In some embodiments of the present invention, in step S2, the roasted product is immersed in deionized water to obtain an immersion liquid and immersion 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 plate of the waste lithium battery and ③ negative electrode plate of the waste lithium battery; wherein ① shell and diaphragm, etc. and ③ negative electrode plate of the waste lithium battery are recycled and processed by other methods. The positive electrode plate 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 at least one of nickel sulfate, cobalt sulfate, and manganese sulfate, for example, nickel sulfate. The specific type of additive can be selected according to the type of heavy metal ions contained in the positive electrode active material to be recovered. For example, if the positive electrode active material to be recovered is a nickel-cobalt-manganese ternary positive electrode active material, any one of nickel-cobalt-manganese sulfates can be selected as a roasting additive, thereby not introducing additional heavy metal ions to complicate the subsequent impurity removal process.

[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 air. In some embodiments of the present invention, the calcination temperature is 550°C to 650°C.

[0049] 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.

[0050] 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:

[0051] (1) The particle size of at least one of the chelating resin and the ion exchange resin is 0.3

[0052] mm~1.25mm, further, the particle size is 0.9mm,

[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. For example, the flow rate of the solution through the resin column is 2 to 4 BV / h, that is, the volume of the solution passing through the resin column per hour is 2 to 4 times the volume of the resin bed. In some embodiments of the present invention, in the S3 step, 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, salt solution from the salt chamber, and acid solution, that is, sulfuric acid, from the acid chamber. In some embodiments, in the bipolar membrane conversion treatment, the voltage setting of a single membrane group for bipolar membrane conversion treatment is 3V to 3.5V, and the rated current of bipolar membrane conversion treatment is 1.1A to 6.6A. In some embodiments of the present invention, a total of ten membrane groups are used for bipolar membrane conversion treatment, and the voltage setting is 30V to 35V. The preparation of lithium hydroxide by bipolar membrane conversion treatment 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 product sulfuric acid, which can be recycled, for example, it can be used for subsequent acid leaching of water-leached slag.

[0056] 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.

[0057] In some embodiments of the present invention, the step S4 includes mixing the water-leached residue with sulfuric acid to obtain a sulfate solution, and the sulfuric acid preferably comes from a bipolar membrane conversion treatment step.

[0058] In some embodiments of the present invention, the S4 step includes mixing a sulfate solution, a precipitant and a complexing agent, and then obtaining a positive electrode active material precursor through a coprecipitation reaction, wherein the precipitant is a mixture of sodium hydroxide and deionized water, and the complexing agent includes ammonia water.

[0059] In some embodiments of the present invention, in the step S4, the coprecipitation reaction is carried out under the protection of an inert gas; the coprecipitation reaction temperature is 50°C to 60°C; the coprecipitation reaction pH is 10.0 to 12.0; and the concentration of the complexing agent is 5 g / L to 6 g / L. In some embodiments of the present invention, the inert gas is nitrogen.

[0060] 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.

[0061] 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 Ni55, that is, the batteries used meet the requirements of LiNi 0.55 Co 0.15 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 NCM532 and NCM811.

[0062] Test methods:

[0063] ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer) element content test:

[0064] 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.

[0065] Embodiment 1:

[0066] S1: Calcination of ternary cathode active materials and additives

[0067] The ternary positive electrode active material is mixed with nickel sulfate hexahydrate (NiSO4·6H2O) in a molar ratio of 2:1 and mixed evenly using a mixer. The obtained mixture is loaded into a boat and placed in a muffle furnace, heated to 600°C at a rate of 5°C / min and kept warm for 1 hour in an air atmosphere, and the calcined product is obtained after natural cooling. The calcined product is crushed through a 200-mesh sieve, and the treated calcined product is taken for the next step.

[0068] S2: Water immersion of roasted products and two-step impurity removal

[0069] The treated calcined product is immersed in deionized water and stirred at room temperature, the solid-liquid ratio of the calcined product to the deionized water is 1:5, the magnetic rotation rate is 1000rpm, and the stirring time is 60min. After that, the water leaching liquid and the water leaching residue are filtered and separated, and the water leaching residue is dried to obtain nickel cobalt manganese oxide. A lithium hydroxide solution with a concentration of 4.19% is added to the water leaching liquid 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 0.9mm, and the flow rate is 2BV / h to obtain a lithium sulfate solution after impurity removal.

[0070] S3: Bipolar membrane system treatment

[0071] The impurity-removed lithium sulfate solution obtained in S2 is subjected to electrodialysis concentration treatment, and the concentrated lithium sulfate solution is introduced into a bipolar membrane conversion device for bipolar membrane conversion treatment. The bipolar membrane conversion treatment setting voltage is 3.2V, and the bipolar membrane conversion treatment rated current is 4.4A, and 20g / L to 30g / L lithium hydroxide solution is obtained by treatment. 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.

[0072] S4: Impurity removal and preparation of nickel-cobalt-manganese precursor

[0073] The nickel cobalt manganese oxide obtained in step S2 is added to 2M sulfuric acid to obtain a nickel cobalt manganese salt solution, sodium hydroxide is added to the nickel cobalt manganese salt solution to adjust the pH and remove impurities, and a filtrate is obtained by filtering, and then the filtrate is subjected to deep impurity removal through a chelating resin to obtain a nickel cobalt manganese sulfate solution after the impurities are removed. The nickel cobalt manganese sulfate solution after the impurities are removed is poured into a coprecipitation reactor, and soluble sulfate (NiSO4, CoSO4, MnSO4) is added according to a stoichiometric ratio to adjust the ratio of nickel salt, cobalt salt, and manganese salt, and deionized water is added so that the metal ion concentration in the mixed solution is controlled at 2M. Sodium hydroxide and deionized water are mixed and configured to form a precipitation agent solution with a concentration of 2.2M, and a complexing agent solution with ammonia concentration of 5.2M is adjusted. Deionized water was added to the reactor, the stirring speed was controlled at 300 rpm and the temperature was raised to 56°C. Ammonia water was added to adjust the ammonia concentration of the bottom liquid in the reactor to 5.4 g / L. Sodium hydroxide solution was added to adjust the pH value to 11.8. In addition, nitrogen was introduced into the reactor for 1 h while adding nickel-cobalt-manganese sulfate solution. The nitrogen flow rate was controlled at 1 m 3 / h; the mixed sulfate solution, precipitant and complexing agent are added into the reaction kettle containing the base liquid in a continuous feeding manner to obtain a nickel-cobalt-manganese ternary positive electrode active material precursor.

[0074] Table 1 Content of each element in the solution at different stages of the recovery method of Example 1 (ppm)

[0075]

[0076] Embodiment 2:

[0077] The difference from Example 1 is that the calcination temperature used is 550°C.

[0078] Table 2: Content of each element in the solution at different stages of the recovery method of Example 2 (ppm)

[0079]

[0080] Embodiment 3:

[0081] The difference from Example 1 is that the calcination temperature used is 650°C.

[0082] Table 3: Content of each element in the solution at different stages of the recovery method of Example 3 (ppm)

[0083]

[0084]

[0085] Embodiment 4:

[0086] The difference from Example 1 is that the calcination temperature used is 500°C.

[0087] Table 4: Content of each element in the solution at different stages of the recovery method of Example 4 (ppm)

[0088]

[0089] Embodiment 5:

[0090] 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.

[0091] Table 5: Content of each element in the solution at different stages of the recovery method of Example 5 (ppm)

[0092]

[0093]

[0094] The results of Examples 1 to 5 show that the use of a suitable proportion of a metal sulfate reducing agent and an increase in the roasting temperature are 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 content of impurity elements 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.

[0095] 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 positive electrode active material of the lithium ion battery 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 coprecipitation reaction.

2. The method according to claim 1, characterized in that In the step S1, the additive includes at least one of nickel sulfate, cobalt sulfate and manganese sulfate.

3. The method according to claim 1 or 2, characterized in that 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.

4. The method according to claim 1 or 2, characterized in that: In the step S1, the calcination temperature is 500° C. to 700° C., and / or the calcination atmosphere is air.

5. 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.

6. The method according to claim 5, 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.

7. 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 5A.

8. The method according to claim 1, characterized in that In the step S4, the sulfate solution, the precipitant and the complexing agent are mixed and subjected to a coprecipitation reaction to obtain a positive electrode active material precursor, wherein the precipitant includes sodium hydroxide and the complexing agent includes aqueous ammonia.

9. The method according to claim 8, characterized in that In the step S4, at least one of the following conditions is met: (1) The coprecipitation reaction is carried out under the protection of an inert gas; (2) The coprecipitation reaction temperature is 50°C to 60°C; (3) The pH of the coprecipitation reaction is 10 to 12; (4) The concentration of the complexing agent is 5 g / L to 6 g / L.

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 an air atmosphere, and cooling to obtain a calcined product; (s2) immersing the calcined product in deionized water at room temperature with a solid-liquid ratio of 1:5 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) removing impurities from the lithium sulfate solution through a chelating resin or an ion exchange resin to obtain a lithium sulfate solution, wherein the resin particles have a particle size of 0.9 mm and a resin adsorption rate of 1 BV / h to 3 BV / h; (s5) treating the impurity-removed lithium sulfate solution by a bipolar membrane system, 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 3 to 3.5 V, and the rated current of the bipolar membrane conversion treatment is 3 A to 4.4 A, to obtain a lithium hydroxide solution, wherein the lithium hydroxide solution is concentrated to obtain a lithium hydroxide monohydrate solid powder; (s6) leaching the water-leached residue obtained in step s2 with sulfuric acid to obtain a nickel-cobalt-manganese salt leachate, adding sodium hydroxide to adjust the pH to remove impurities, filtering to obtain a filtrate, and removing impurities from the filtrate with a chelating resin to obtain a nickel-cobalt-manganese sulfate solution; (s7) Under a nitrogen atmosphere, the nickel-cobalt-manganese sulfate solution, the precipitant and the complexing agent are mixed to carry out a coprecipitation reaction to obtain a nickel-cobalt-manganese positive electrode active material precursor.

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