A Method for Comprehensive Recovery of Lithium and Cobalt from the Cathode Material of Waste Lithium Cobalt Oxide Batteries

Abstract

The present invention provides a method for comprehensively recovering lithium and cobalt from the cathode material of waste lithium cobalt oxide batteries, comprising the following steps: (1) Pretreating the cathode material of waste lithium cobalt oxide batteries to obtain lithium cobalt oxide cathode active material; mixing the lithium cobalt oxide cathode active material evenly with a sulfur-based compound and a carbon source to obtain a mixed material; subjecting the mixed material to roasting in an inert atmosphere, grinding, leaching, and filtering in sequence to obtain a lithium-containing solution and a sulfur-containing filter residue; (2) Subjecting the sulfur-containing filter residue to acid leaching for impurity removal and filtering to obtain cobalt sulfide slag; (3) Roasting the cobalt sulfide slag in an oxygen atmosphere to obtain a roasted product; (4) Subjecting the roasted product to leaching and filtering to obtain a cobalt sulfate solution and cobalt tetroxide. The method of the present invention can obtain soluble sulfates and high-purity cobalt oxides, and has a short process flow, low cost, and high lithium selectivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization of waste lithium-ion batteries, and particularly relates to a method for comprehensively recovering lithium and cobalt from the positive electrode material of waste lithium cobalt oxide batteries. Background Art

[0002] For a long time, coal, oil and natural gas have been the main energy sources in the form of fossil fuels. Such an energy structure has caused serious environmental pollution, and the resulting global warming problem and ecological environment deterioration problem have received increasing attention. Therefore, the development of renewable energy and new energy has become one of the most decisive influences in the future technical field and the future economic world. As a new type of secondary clean and renewable energy, lithium-ion batteries have the advantages of high working voltage, light weight, large energy density, etc., and have been widely used in fields such as power tools, digital cameras, mobile phones, and laptop computers, and show a strong development trend.

[0003] With the booming development of new energy vehicles, as well as the promotion of policies and the market, a large number of lithium-ion batteries have entered the market, and the problem of recycling and reuse of waste lithium-ion batteries has also become a major challenge in the industry. As the usage time increases, the performance of lithium-ion batteries in various aspects such as capacity, discharge efficiency, and safety will significantly decline. For lithium batteries that can no longer meet the current application requirements, recycling can effectively utilize their "remaining value".

[0004] The currently widely used mainstream treatment process mainly involves obtaining active substances after pretreatment of waste lithium-ion batteries, acid leaching the positive electrode active substances, neutralizing and removing impurities, solid-liquid separation, extraction, lithium precipitation, washing, and drying. It consumes a large amount of acids and alkalis, and the equipment needs to be acid- and alkali-resistant. The lithium obtained finally has a high impurity content and a low lithium recovery rate. The subsequent treatment process is cumbersome, and more alkali solution needs to be added for impurity removal and neutralization. There is a need to develop a method that can separate and recycle.

[0005] Patent document CN202110557624.3 discloses a recycling product and a recycling method of waste lithium cobalt oxide batteries. It dissolves the positive electrode material through acid leaching, and stops leaching when the cobalt dissolution is 10-40% and the cobalt dissolution reaches 88-99%. The filter cake is dried and calcined. This method will cause a part of the cobalt to enter the lithium-containing leaching solution, and the cobalt and lithium cannot be effectively separated, resulting in loss of cobalt.

[0006] Patent document CN202110399723.3 discloses a recycling method for the positive electrode material of waste lithium cobalt oxide batteries. It roasts with the addition of additives in a reducing atmosphere; the roasted product is subjected to water leaching, and a lithium-rich solution is obtained through solid-liquid separation. The water leaching residue is acid-leached to obtain a transition metal solution. This method has a large loss, the lithium extraction residue needs to be acid-leached to dissolve, and the process of removing impurities such as aluminum and iron will also cause acid and alkali losses. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology, and provide a method for comprehensively recovering lithium and cobalt from the cathode material of waste lithium cobalt oxide batteries. Compared with the traditional process, this method involves mixing the lithium cobalt oxide cathode active material with a sulfur-based compound and a carbon source for roasting, and subjecting the obtained sulfur-containing filter residue to acid leaching for impurity removal. Then, the obtained cobalt sulfide residue is oxidized and roasted to obtain soluble sulfate and high-purity cobalt oxide. Moreover, the method has a short process flow, low cost, and high lithium selectivity.

[0008] To solve the above technical problem, the technical solution proposed by the present invention is as follows:

[0009] A method for comprehensively recovering lithium and cobalt from the cathode material of waste lithium cobalt oxide batteries, comprising the following steps:

[0010] (1) Pretreat the cathode material of waste lithium cobalt oxide batteries to obtain lithium cobalt oxide cathode active material; mix the lithium cobalt oxide cathode active material evenly with a sulfur-based compound and a carbon source to obtain a mixture; subject the mixture to roasting in an inert atmosphere, grinding, leaching, and filtration in sequence to obtain a lithium-containing solution and a sulfur-containing filter residue;

[0011] The sulfur-based compound is one or more of thiourea and mercaptan; the carbon source is one or more of carbon black, lignite, and asphalt; the mass ratio of the lithium cobalt oxide cathode active material to the sulfur-based compound and the carbon source is 2-4:1:0.3-0.5;

[0012] (2) Subject the sulfur-containing filter residue to acid leaching for impurity removal and filtration to obtain a cobalt sulfide residue; the acid used for acid leaching for impurity removal is at least one of sulfuric acid and hydrochloric acid; the concentration of the acid is 0.1-0.8 mol / L; the liquid-solid ratio of the acid leaching for impurity removal is 8-20:1 mL / g;

[0013] (3) Roast the cobalt sulfide residue in an oxygen atmosphere at a roasting temperature of 500-850 °C to obtain a roasted product;

[0014] (4) Subject the roasted product to leaching and filtration to obtain a cobalt sulfate solution and cobalt tetroxide.

[0015] The present invention uses a sulfur-based compound, a carbon source, and a lithium cobalt oxide cathode active material to be mixed and roasted. By using the generated sulfide atmosphere such as hydrogen sulfide and carbon disulfide, the oxygen site in lithium cobalt oxide is replaced by a sulfur site, destroying the layered structure of the lithium cobalt oxide material, and releasing the lithium restricted between the transition metal layers. The cobalt element is converted into a sulfide that is insoluble in water and acid, and the lithium is converted into a soluble lithium compound, achieving the effect of lithium-cobalt separation. Without the sulfur-based compound, the layered structure of lithium cobalt oxide cannot be destroyed at low temperature, and the reaction cannot proceed; without the carbon source, the sulfur generated in the reaction cannot be fixed, resulting in excessive consumption of the sulfur-based compound and a decrease in the reaction rate.

[0016] Preferably, the time for acid leaching and impurity removal is 1 - 3 h, the liquid-solid ratio is 8 - 20:1 mL / g, and the temperature is room temperature.

[0017] Preferably, in step (3), the heating rate of the roasting is 4 - 5 °C / min; the roasting time is 2 - 4 h. If the roasting temperature is too low, the reaction cannot proceed, and if the reaction time is too long, the energy consumption increases.

[0018] Preferably, in step (4), the leaching is carried out by stirring with pure water; the leaching time is 20 - 60 min, the liquid-solid ratio during leaching is 10 - 12:1 mL / g, and the leaching temperature is room temperature. If the above leaching time is too short, the cobalt salt cannot be completely released into the solution.

[0019] The present invention controls the oxidation degree of cobalt sulfide by controlling the temperature and reaction time of oxidative roasting, transfers the transition metal elements into the liquid phase to form a sulfate solution through water leaching, and the generated transition metal oxide can also be used as a negative electrode material or a raw material for synthesizing lithium cobalt oxide, realizing the comprehensive recovery of lithium and cobalt from the waste lithium cobalt oxide of waste lithium-ion batteries.

[0020] Preferably, in step (1), the waste lithium cobalt oxide battery cathode material is a lithium cobalt oxide battery cathode sheet, and the pretreatment includes the following steps: pyrolyzing the waste lithium cobalt oxide battery cathode material to separate the current collector aluminum foil from the cathode active material, and ball-milling and sieving the separated cathode active material to obtain the lithium cobalt oxide cathode active material.

[0021] Preferably, in step (1), the roasting temperature is 400 - 650 °C, the roasting time is 5 - 40 min; the heating rate of the roasting is 5 - 7 °C / min. In the present invention, if the roasting temperature is too low and the reaction temperature is not reached, the lithium cobalt oxide cathode active material cannot be decomposed. If the roasting temperature is too high, the energy consumption increases. At the same time, if the reaction time is too short, the decomposition of the sulfur-based compound and the like is incomplete, and if the reaction time is too long, the roasted material agglomerates seriously. In addition, the roasting atmosphere is an inert atmosphere. Roasting in this atmosphere can isolate oxygen and water. Roasting in air may generate sulfates, resulting in the loss of cobalt during leaching.

[0022] Preferably, in step (1), the leaching is carried out by stirring with water or weak acid, the leaching time is 30 - 60 min, the liquid - solid ratio during leaching is 10 - 12:1 mL / g, and the leaching temperature is room temperature.

[0023] In the present invention, the treated active material is mixed evenly with a certain amount of sulfur - containing compound and carbon source. By controlling the addition amounts of the sulfur - containing compound and carbon source and the reaction temperature, the sulfidation degree of cobalt is controlled, and the cobalt metal oxide in the positive - electrode active material is changed into insoluble sulfide. Then, lithium is transferred from the solid phase to the liquid phase by leaching with water or weak acid.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) In the present invention, by mixing and roasting the lithium cobalt oxide positive - electrode active material with a sulfur - containing compound and a carbon source, and subjecting the sulfur - containing filter residue to acid leaching for impurity removal and filtration, a single transition - metal sulfide (cobalt sulfide) can be generated, and by controlling oxidative roasting and water leaching, it can be changed into cobalt sulfate solutions with different ratios and cobalt tetroxide. Moreover, the cobalt tetroxide generated in the present invention can still be used as battery materials such as the synthesis of lithium cobalt oxide positive - electrode materials or oxide negative - electrode materials.

[0026] (2) The method for comprehensively recovering lithium and cobalt from the positive - electrode material of waste lithium cobalt oxide batteries in the present invention reduces costs. The transition - metal element cobalt has no loss during lithium leaching, and has a high selectivity for lithium.

[0027] (3) The method of the present invention has a simple process, a short process time, low raw material costs, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 is the process flow chart of the method of the present invention;

[0030] Figure 2 is the XRD pattern of cobalt sulfide slag in Example 3;

[0031] Figure 3 is the XRD pattern of the roasting product in Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] To facilitate the understanding of the present invention, the following will provide a more comprehensive and detailed description of the present invention in conjunction with the accompanying drawings of the specification and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0033] Unless otherwise defined, all the technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0034] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0035] Example 1:

[0036] A method for comprehensively recovering lithium and cobalt from the cathode material of waste lithium cobalt oxide batteries, and its process flow chart is as Figure 1 shown. The specific steps are as follows:

[0037] (1) Put the waste lithium cobalt oxide battery into a sodium chloride solution of 130 g / L for discharging treatment, disassemble the battery case, and separate the cathode plate of the lithium cobalt oxide battery, the anode plate of the lithium cobalt oxide battery, the separator, and the electrolyte from the battery; subject the cathode plate of the lithium cobalt oxide battery to high-temperature pyrolysis. The temperature of the high-temperature pyrolysis is 650 °C and the time is 6 h to separate the current collector aluminum foil from the cathode active material. Ball-mill and sieve the separated cathode active material to obtain the cathode active material of lithium cobalt oxide.

[0038] (2) Ball-mill and mix the cathode active material of lithium cobalt oxide, thiourea, and carbon black according to a mass ratio of 2:1:0.3 to make the materials evenly mixed and obtain a mixed material.

[0039] (3) Put the mixed material obtained in step (2) into a tubular furnace and carry out roasting under an argon atmosphere. The heating rate of the roasting is 5 °C / min, the roasting temperature is 550 °C, and the time is 20 min to obtain a roasted material.

[0040] (4) Grind the roasted material obtained in step (3), stir and leach it with ultrapure water at a liquid-solid ratio of 10:1 mL / g at room temperature for 30 min. After the leaching is completed, filter to obtain a lithium-containing filtrate with a lithium leaching rate of 99.6% and a sulfur-containing filter residue. The lithium-containing filtrate can be heated and evaporated to prepare lithium sulfide or sodium carbonate can be added to obtain lithium carbonate.

[0041] (5) Carry out acid leaching and impurity removal on the sulfur-containing filter residue obtained in step (4) and filter to obtain a cobalt sulfide residue. The acid leaching and impurity removal is carried out by acid leaching with 0.5 mol / L sulfuric acid, the liquid-solid ratio is 20:1 mL / g, the time of acid leaching and impurity removal is 2 h, the temperature is room temperature, and the cobalt sulfide residue is obtained by filtration.

[0042] (6) Put the cobalt sulfide slag obtained in step (5) into a tubular furnace and roast it in an oxygen atmosphere. The heating rate of roasting is 5 °C / min, the roasting temperature is 850 °C, and the time is 180 min to obtain a roasted product.

[0043] (7) Stir and leach the roasted product obtained in step (6) with ultrapure water at room temperature for 20 min. The liquid-solid ratio is 10:1 mL / g. After the leaching is completed, filter to obtain a cobalt sulfate solution and cobalt tetroxide. The leaching rate of cobalt is 0.3%; the purity of cobalt tetroxide reaches 99.3% and can be used as a raw material for synthesizing lithium cobaltate; the total recovery rate of cobalt is 99.3%. In the method of this example, the product after high-temperature oxidation roasting is mainly cobalt tetroxide, and the soluble cobalt sulfate is almost completely converted into insoluble oxides, and cobalt is hardly leached.

[0044] Example 2:

[0045] A method for comprehensively recovering lithium and cobalt from the positive electrode material of waste lithium cobalt oxide batteries, and its process flow chart is as Figure 1 shown, and the specific steps are as follows:

[0046] (1) Put the waste lithium cobalt oxide battery into a 130 g / L sodium chloride solution for discharging treatment, disassemble the battery case, and separate the positive electrode sheet, negative electrode sheet, separator, and electrolyte of the lithium cobalt oxide battery from the battery; subject the positive electrode sheet of the lithium cobalt oxide battery to high-temperature pyrolysis at a temperature of 650 °C for 6 h to separate the current collector aluminum foil from the positive electrode active material, and ball-mill and sieve the separated positive electrode active material to obtain the positive electrode active material of lithium cobalt oxide.

[0047] (2) Ball-mill and mix the positive electrode active material of lithium cobalt oxide with thiourea and carbon black according to a mass ratio of 3:1:0.5 to make the materials evenly mixed to obtain a mixed material.

[0048] (3) Put the mixed material obtained in step (2) into a tubular furnace and roast it in an argon atmosphere. The heating rate of roasting is 5 °C / min, the roasting temperature is 550 °C, and the time is 20 min to obtain a roasted material.

[0049] (4) Grind the roasted material obtained in step (3), stir and leach it with ultrapure water at a liquid-solid ratio of 10:1 mL / g at room temperature for 30 min. After the leaching is completed, filter to obtain a lithium-containing filtrate with a lithium leaching rate of 90% and a sulfur-containing filter residue. The lithium-containing filtrate can be heated and evaporated to prepare lithium sulfide or added with sodium carbonate to obtain lithium carbonate.

[0050] (5) The sulfur-containing filter residue obtained in step (4) is subjected to acid leaching for impurity removal and filtration to obtain cobalt sulfide residue. The acid leaching for impurity removal is carried out using 0.1 mol / L sulfuric acid, with a liquid-solid ratio of 10:1 mL / g, an acid leaching time of 2 h, a temperature of room temperature, and filtration to obtain cobalt sulfide residue.

[0051] (6) The cobalt sulfide residue obtained in step (5) is placed in a tubular furnace and roasted in an oxygen atmosphere. The heating rate of roasting is 5 °C / min, the roasting temperature is 550 °C, and the time is 180 min to obtain a roasted product.

[0052] (7) The roasted product obtained in step (6) is stirred and leached with ultrapure water at room temperature for 20 min, with a liquid-solid ratio of 10:1 mL / g. After the leaching is completed, filtration is carried out to obtain cobalt sulfate solution and cobalt tetroxide. The leaching rate of cobalt can reach 43%. The cobalt sulfate solution can be concentrated, evaporated, and crystallized to obtain high-purity cobalt sulfate; the purity of cobalt tetroxide reaches 98.0%, which can be used as a raw material for synthesizing lithium cobaltate; the total recovery rate of cobalt is 99.2%.

[0053] Example 3:

[0054] A method for comprehensively recovering lithium and cobalt from the cathode material of waste lithium cobalt oxide batteries, and its process flow chart is as Figure 1 shown, and the specific steps are as follows:

[0055] (1) The waste lithium cobalt oxide battery is placed in a 130 g / L sodium chloride solution for discharging treatment. The battery case is disassembled, and the battery is separated into a lithium cobalt oxide battery cathode plate, a lithium cobalt oxide battery anode plate, a separator, and an electrolyte; the lithium cobalt oxide battery cathode plate is subjected to high-temperature pyrolysis. The high-temperature pyrolysis temperature is 650 °C, and the time is 3 h to separate the current collector aluminum foil from the cathode active material. The separated cathode active material is ball-milled and sieved to obtain lithium cobalt oxide cathode active material.

[0056] (2) The lithium cobalt oxide cathode active material, thiourea, and carbon black are ball-milled and mixed according to a mass ratio of 2:1:0.3 to make the materials mixed evenly to obtain a mixed material.

[0057] (3) The mixed material obtained in step (2) is placed in a tubular furnace and roasted in an argon atmosphere. The heating rate of roasting is 5 °C / min, the roasting temperature is 550 °C, and the time is 20 min to obtain a roasted material.

[0058] (4) The roasted material obtained in step (3) is ground and stirred and leached with ultrapure water at a liquid-solid ratio of 10:1 mL / g at room temperature for 30 min. After the leaching is completed, filtration is carried out to obtain a lithium-containing filtrate with a lithium leaching rate of 99.2% and a sulfur-containing filter residue. The lithium-containing filtrate can be heated and evaporated to prepare lithium sulfide or sodium carbonate can be added to obtain lithium carbonate.

[0059] (5) The sulfur-containing filter residue obtained in step (4) is subjected to acid leaching for impurity removal and filtration to obtain cobalt sulfide residue. The acid leaching for impurity removal is carried out using 0.5 mol / L sulfuric acid for acid leaching and impurity removal, the liquid-solid ratio is 10:1 mL / g, the time for acid leaching and impurity removal is 2 h, the temperature is room temperature, and filtration is carried out to obtain cobalt sulfide residue.

[0060] (6) The cobalt sulfide residue obtained in step (5) is placed in a tube furnace and calcined in an oxygen atmosphere. The heating rate of the calcination is 5 °C / min, the temperature of the calcination is 600 °C, and the time is 240 min to obtain a calcined product.

[0061] (7) The calcined product obtained in step (6) is stirred and leached with ultrapure water at room temperature for 20 min, and the liquid-solid ratio is 10:1 mL / g. After the leaching is completed, filtration is carried out to obtain cobalt sulfate solution and cobalt tetroxide. The leaching rate of cobalt can reach 75%. The cobalt sulfate solution can obtain high-purity cobalt sulfate through concentration, evaporation and crystallization; the purity of cobalt tetroxide reaches 99.1% and can be used as a raw material for synthesizing lithium cobaltate; the total recovery rate of cobalt is 99.3%.

[0062] The XRD pattern of the cobalt sulfide residue in step (5) of this example is shown in Figure 2. After calcination, cobalt is converted to CoS2. The XRD pattern of the calcined product in step (6) is as Figure 3 shown. After oxidative calcination, cobalt sulfide is converted to cobalt sulfate and cobalt tetroxide.

[0063] Comparative Example 1:

[0064] Different from Example 1, in step (6) of Comparative Example 1, the calcination temperature is 400 °C.

[0065] Finally, the leaching rate of cobalt is 8.2%, the purity of cobalt tetroxide is 15.2%, and the total recovery rate of cobalt is 99.1%. The reasons for the decrease in leaching rate and purity are that the oxidative calcination temperature of 400 °C does not reach the reaction temperature of CoS2, resulting in incomplete reaction and failure to be completely converted into cobalt sulfate or cobalt tetroxide. The cobalt tetroxide product has many impurities and is difficult to utilize.

[0066] Comparative Example 2:

[0067] Different from Example 3, in step (5) of Comparative Example 2, 0.05 mol / L sulfuric acid is used for acid leaching and impurity removal; the liquid-solid ratio is 15:1.

[0068] Finally, the leaching rate of cobalt is 43%, the purity of cobalt tetroxide is 94.2%, and the total recovery rate of cobalt is 99.2%. The reason for the decrease in purity is that the concentration of acid during acid leaching is too low, resulting in incomplete impurity removal and too many impurities entering the cobalt tetroxide.

[0069] Comparative Example 3:

[0070] Different from Example 3, step (2) was replaced with the following step: The lithium cobalt oxide cathode active material and thiourea were ball-milled and mixed at a mass ratio of 2:1 to make the materials evenly mixed, obtaining a mixed material.

[0071] The final leaching rate of cobalt was 51%, the purity of cobalt tetroxide was 82.3%, and the total recovery rate of cobalt was 99.1%; the reasons for the decrease in the leaching rate and purity were that no carbon source was added, resulting in insufficient sulfidation reaction and inability to be fully converted into sulfide components.

[0072] Comparative Example 4:

[0073] Different from Example 3, step (2) was replaced with the following step: The lithium cobalt oxide cathode active material and carbon black were ball-milled and mixed at a mass ratio of 2:0.3 to make the materials evenly mixed, obtaining a mixed material.

[0074] The final leaching rate of cobalt was 0%, and the purity of cobalt tetroxide was 13%; without adding sulfur-based compounds, it was impossible to effectively destroy the used lithium cobalt oxide at low temperature, and only a small part of the lithium cobalt oxide was decomposed, and most of the products still maintained the structure of the intact lithium cobalt oxide.

Claims

1. A method for comprehensively recovering lithium and cobalt from the cathode material of waste lithium cobalt oxide batteries, characterized in that, It includes the following steps: (1) Pretreat the cathode material of waste lithium cobalt oxide batteries to obtain lithium cobalt oxide cathode active material; mix the lithium cobalt oxide cathode active material evenly with a sulfur-based compound and a carbon source to obtain a mixture; subject the mixture to calcination in an inert atmosphere, grinding, leaching, and filtration in sequence to obtain a lithium-containing solution and a sulfur-containing filter residue; The sulfur-based compound is one or more of thiourea and mercaptan; the carbon source is one or more of carbon black, lignite, and pitch; the mass ratio of the lithium cobalt oxide cathode active material, the sulfur-based compound, and the carbon source is 2-4:1:0.3-0.5; (2) Acid-leach and filter the sulfur-containing filter residue to obtain cobalt sulfide slag; the acid used for acid-leaching and impurity removal is at least one of sulfuric acid and hydrochloric acid; the concentration of the acid is 0.1-0.8 mol / L; the liquid-solid ratio of the acid-leaching and impurity removal is 8-20:1 mL / g; (3) Calcinate the cobalt sulfide slag in an oxygen atmosphere at a calcination temperature of 500-850 °C to obtain a calcined product; (4) Leach and filter the calcined product to obtain a cobalt sulfate solution and cobalt tetroxide.

2. The method according to claim 1, characterized in that, The time for acid-leaching and impurity removal is 1-3 h, and the temperature is room temperature.

3. The method according to claim 1, wherein In step (3), the heating rate of the calcination is 4-5 °C / min; the calcination time is 2-4 h.

4. The method according to claim 1, characterized in that, In step (4), the leaching is carried out by stirring with pure water; the leaching time is 20-60 min, the liquid-solid ratio during leaching is 10-12:1 mL / g, and the leaching temperature is room temperature.

5. The method according to any one of claims 1-4, characterized in that, In step (1), the cathode material of the waste lithium cobalt oxide battery is a lithium cobalt oxide battery cathode sheet, and the pretreatment includes the following steps: pyrolyze the cathode material of the waste lithium cobalt oxide battery to separate the current collector aluminum foil from the cathode active material, and ball-mill and screen the separated cathode active material to obtain lithium cobalt oxide cathode active material.

6. The method according to any one of claims 1-4, characterized in that In step (1), the calcination temperature is 400-650 °C, and the calcination time is 5-40 min; the heating rate of the calcination is 5-7 °C / min.

7. The method according to any one of claims 1 to 4, characterized in that, In step (1), the leaching is carried out by stirring with water or weak acid, the leaching time is 30-60 min, the liquid-solid ratio during leaching is 10-12:1 mL / g, and the leaching temperature is room temperature.

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