Leaching method, recycling method and application of metal in lithium cobalt oxide positive plate

Abstract

The invention provides a leaching method and a recycling method of metal in a lithium cobalt oxide positive plate. The leaching method comprises the following steps: mixing a lithium cobalt oxide positive plate disassembled from a waste battery and methanol in a high-pressure reaction kettle, introducing inert gas to exhaust air, sealing the high-pressure reaction kettle, and heating to a certain temperature until a binder is dissolved in methanol to separate the lithium cobalt oxide positive plate from a current collector to obtain a mixture, performing solid-liquid separation on the mixture to obtain filter residues and filtrate; and dispersing the filter residue and chlorinated polyvinyl chloride powder in water, putting into a high-pressure reaction kettle, uniformly mixing, heating to 160 DEG C or above, carrying out a reaction until Li < + > and Co < 2 + > in the lithium cobalt oxide positive electrode material are leached out of water, and carrying out solid-liquid separation to obtain a leaching solution containing Li < + > and Co < 2 + >. According to the leaching method, the corrosion influence of direct use of strong acid on equipment can be avoided, the generation of pollutants can be avoided, and the damage to the current collector can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling and utilization of lithium-ion batteries, in particular to the recycling and utilization of cathode materials, and more particularly to a method for leaching metals in lithium cobaltate-based cathode sheets, a recycling method and applications thereof. Background Art

[0002] Lithium cobaltate is the earliest commercially applied cathode material for lithium-ion batteries, which has the characteristics of high energy density and good safety, and is widely used in mobile electronic devices such as mobile phones, laptop computers, cameras, etc. Waste lithium cobaltate secondary batteries have become the main type of waste lithium-ion batteries, which contain a large amount of cobalt resources. Therefore, waste lithium cobaltate secondary batteries have been studied earlier, and their recycling methods are also applicable to the recycling of waste ternary, lithium manganate and other types of lithium batteries.

[0003] Currently, the main substances recovered from waste lithium cobaltate secondary batteries are negative electrode current collectors (commonly copper foils), positive electrode current collectors (commonly aluminum foils), positive electrode active materials and negative electrode active materials. Among them, the recovery of positive electrode active materials mainly has two methods: wet process and pyrometallurgical process. The wet process has become the mainstream recovery solution due to its mild conditions and low energy consumption, and mainly includes pretreatment, leaching, recovery and other links.

[0004] Pretreatment is mainly to selectively separate the higher-value cathode materials, remove the slightly lower-value components or organic solvents, and reduce the adverse effects in the subsequent leaching process. The main methods include discharging, crushing, dissolving, calcining, pyrolysis, etc. The requirements for discharging in pretreatment are relatively high. Crushing is likely to damage the current collector and cause metal impurities to interfere. Dissolving produces a large amount of waste liquid. Calcining and pyrolysis require high energy consumption and produce gaseous pollutants. Leaching is mainly a process of selectively extracting and recovering lithium and cobalt from the cathode material, and the main methods include wet leaching, water leaching, etc. Recovery is a process of recovering lithium and cobalt from the leaching solution by extraction, precipitation, electrochemistry and other methods. Among them, the leaching process is the key step in the recovery of lithium and cobalt, and the leaching rate directly affects the subsequent recovery rate.

[0005] The wet leaching of lithium cobaltate materials is mainly an acid leaching scheme, and the most common leaching system is inorganic acid (sulfuric acid, hydrochloric acid or nitric acid) + hydrogen peroxide. The combination of inorganic acid + hydrogen peroxide can leach lithium and cobalt better, but inorganic acid has strong corrosiveness, high requirements for equipment, and is prone to generate harmful gases. Water leaching is to use reduction roasting to convert the cathode material obtained by pretreatment into lithium carbonate components, and then water leach / carbonated water leach to recover lithium first. Water leaching of lithium elements in waste materials has the characteristics of high efficiency and easy product treatment, but most of them require roasting treatment, and this link still has the disadvantages of slightly high energy consumption and easy pollution. Therefore, both acid leaching and water leaching have high requirements for energy consumption and post-treatment of chemical agents. Summary of the Invention

[0006] Based on the above problems, the object of the present invention is to provide a method for leaching metals in a lithium cobalt oxide-based positive electrode sheet, a recovery method and an application thereof. This leaching method can avoid the corrosion effect of direct use of strong acids on equipment, can also avoid the generation of pollutants, and can further avoid damage to the current collector.

[0007] To achieve the above object, the first aspect of the present invention provides a method for leaching metals in a lithium cobalt oxide-based positive electrode sheet. The lithium cobalt oxide-based positive electrode sheet includes a current collector and a lithium cobalt oxide material coating attached to the current collector. The lithium cobalt oxide material coating includes a lithium cobalt oxide positive electrode material, a binder, and a conductive agent. The method for leaching metals in the lithium cobalt oxide-based positive electrode sheet includes: (1) High-pressure separation Mix the lithium cobalt oxide-based positive electrode sheet disassembled from a waste battery and methanol in a high-pressure reaction kettle, introduce an inert gas to exhaust air, then seal the high-pressure reaction kettle and raise the temperature to a certain level until the binder dissolves in methanol to detach the lithium cobalt oxide positive electrode material from the current collector to obtain a mixture, and perform solid-liquid separation on the mixture to obtain a filter residue and a filtrate; (2) Water leaching Disperse the filter residue and polyvinyl chloride powder in water and put them into a high-pressure reaction kettle to mix evenly, raise the temperature to above 160 °C for reaction until Li + and Co 2+ are leached into water, and then perform solid-liquid separation to obtain a leaching solution containing Li + and Co 2+ .

[0008] The leaching method of the present invention uses high pressure and high temperature to strip the lithium cobalt oxide positive electrode material. Compared with the conventional method of mechanically crushing and screening to obtain the lithium cobalt oxide positive electrode material, the method of high-pressure and high-temperature stripping will not damage the aluminum foil and there is no interference from aluminum chip impurities. Compared with the high-temperature calcination stripping method that generates gaseous fluorinated pollutants, the high-pressure and high-temperature stripping method has no pollution generation, and methanol and PVDF can be further recycled. By using the property that polyvinyl chloride powder decomposes to produce chlorine in water under high temperature and high pressure to produce hydrochloric acid to achieve the leaching of lithium and cobalt, the use of strong acids can be avoided.

[0009] The mechanism of the method for leaching metals in the lithium cobalt oxide-based positive electrode sheet of the present invention can be: (1) In a sealed high-pressure and high-temperature reaction kettle, the binder dissolves in methanol to obtain a non-damaged current collector and a mixture. The mixture is an organic solution system of methanol / binder dispersed with lithium cobalt oxide positive electrode material and a conductive agent. After filtration, a filter residue containing lithium cobalt oxide positive electrode material and a conductive agent can be obtained.

[0010] (2) The filter residue and the chlorinated polyvinyl chloride powder are dispersed in water and put into a high-pressure reactor for mixing. Since the chlorinated polyvinyl chloride itself has a relatively high chlorine content, in a high-pressure aqueous solution at a temperature higher than 160 °C, a large amount of chlorine will be released into the water phase and react with water at high temperature and pressure to generate HCl, which further promotes the leaching of Li + and Co 2+ in the lithium cobalt oxide cathode material. In addition, under high pressure, the viscosity, surface tension and dielectric constant of water decrease, and the diffusion rate of water increases, which is conducive to enhancing the diffusion and dissociation effect of water on various organic molecules, dissociating them into smaller particle molecules. Therefore, the high-pressure environment can accelerate the decomposition of chlorinated polyvinyl chloride. The decomposition reaction process of chlorinated polyvinyl chloride is shown in Equation 1. The leaching reaction of the lithium cobalt oxide cathode material is shown in Equation 2. After the reaction is completed, the filtrate obtained by solid-liquid separation is the leaching solution containing Li + and Co 2+ , and the filter residue is a mixture of various degradation products of chlorinated polyvinyl chloride and conductive agents.

[0011] Equation 1 6HCl + 2Li2CoO2 → 2LiCl + 2CoCl2 + 0.5O2 + 3H2O Equation 2 As a technical solution of the present invention, the liquid-solid ratio of the methanol and the lithium cobalt oxide-based positive electrode sheet is 8-15 L / kg.

[0012] As a technical solution of the present invention, in the high-pressure separation step, the certain temperature is 180-250 °C, the heating rate is 3-5 °C / min, and the heat preservation time is 10-30 min.

[0013] As a technical solution of the present invention, the filtrate is evaporated at 80-100 °C to recover the methanol and applied to the high-pressure separation step.

[0014] As a technical solution of the present invention, the mass ratio of the filter residue and the chlorinated polyvinyl chloride powder is 1:2.5-3.5.

[0015] As a technical solution of the present invention, the sum of the masses of the filter residue and the chlorinated polyvinyl chloride powder is M, and the volume of the water is V. V / M is 20-30 L / kg.

[0016] As a technical solution of the present invention, in the water leaching step, the temperature is raised to 180-250 °C, the heating rate is 3-5 °C / min, and the reaction time is 20-100 min.

[0017] As a technical solution of the present invention, the chlorinated polyvinyl chloride powder can be obtained by crushing waste chlorinated polyvinyl chloride products. The particle size of the chlorinated polyvinyl chloride powder is 0.1 - 1.0 μm. The number average molecular weight of the chlorinated polyvinyl chloride in the chlorinated polyvinyl chloride powder is > 50,000, the chlorine content is 61 - 74 vol.%, and the thermal decomposition temperature is < 170 °C.

[0018] The second aspect of the present invention provides a method for recovering metals in a lithium cobalt oxide-based positive electrode sheet, including: (I) Obtaining a leaching solution containing Li + and Co 2+ according to the aforementioned method for leaching metals in a lithium cobalt oxide-based positive electrode sheet; II) Adding an alkali solution to the leaching solution to precipitate Co(OH)2, performing solid-liquid separation to recover metallic cobalt, adding sodium carbonate to the filtrate to precipitate Li2CO3, and performing solid-liquid separation to recover metallic lithium.

[0019] The third aspect of the present invention provides an application of the aforementioned method for recovering metals in a lithium cobalt oxide-based positive electrode sheet in a lithium cobalt oxide secondary battery, with the lithium recovery rate ≥ 95% and the cobalt recovery rate ≥ 90%. Detailed implementation manners

[0020] The present invention provides a method for leaching metals, a method for recovering metals, and an application in a lithium cobalt oxide-based positive electrode sheet, which can achieve high-proportion leaching and recovery of lithium and cobalt.

[0021] The lithium cobalt oxide-based positive electrode sheet of the present invention includes a current collector and a lithium cobalt oxide material coating attached to the current collector. The current collector can be an aluminum foil, and the lithium cobalt oxide material coating includes a lithium cobalt oxide positive electrode material, a binder, and a conductive agent. The chemical formula of the lithium cobalt oxide positive electrode material is Li a Co b M (1-b) O2, where M is at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, 0.95 ≤ a ≤ 1.05, and 0.95 ≤ b ≤ 1.00. The binder includes PVDF. The conductive agent includes at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, and graphene. The mass ratio of the lithium cobalt oxide positive electrode material, the binder, and the conductive agent can be, but is not limited to, 85 - 98:0.5 - 3.0:0.5 - 3.0. Making a slurry of the lithium cobalt oxide positive electrode material, the binder, and the conductive agent with a solvent and coating it on the aluminum foil, drying, rolling, etc. can obtain the lithium cobalt oxide-based positive electrode sheet.

[0022] The method for leaching metals in the lithium cobalt oxide-based positive electrode sheet of the present invention includes the following steps.

[0023] (1) High-pressure separation The lithium cobalt oxide-based positive electrode sheet disassembled from waste batteries and methanol are placed in a high-pressure reactor and mixed. After introducing an inert gas to exhaust air, the high-pressure reactor is sealed and heated to a certain temperature until the binder dissolves in methanol to separate the lithium cobalt oxide positive electrode material from the current collector, obtaining a mixture. The mixture is subjected to solid-liquid separation to obtain a filter residue and a filtrate.

[0024] (2) Water leaching The filter residue and polyvinyl chloride powder are dispersed in water and put into a high-pressure reactor and mixed evenly. The temperature is raised to above 160 °C for reaction until Li + and Co 2+ are leached into water, and then solid-liquid separation is carried out to obtain a leaching solution containing Li + and Co 2+ .

[0025] Among them, in step (1), the liquid-solid ratio of methanol to the lithium cobalt oxide-based positive electrode sheet is 8-15 L / kg. As an example, it can be but is not limited to 8 L / kg, 9 L / kg, 10 L / kg, 11 L / kg, 12 L / kg, 13 L / kg, 14 L / kg, 15 L / kg. The inert gas can be nitrogen, helium, neon, argon, krypton, and xenon. The certain temperature is 180-250 °C. As an example, it can be but is not limited to 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C. The heating rate is 3-5 °C / min. As an example, it can be but is not limited to 3 °C / min, 4 °C / min, 5 °C / min. The heat preservation time is 10-30 min. As an example, it can be but is not limited to 10 min, 15 min, 20 min, 25 min, 30 min. The filtrate is evaporated at 80-100 °C to recover methanol and applied to the high-pressure separation step, and the methanol can be reused repeatedly.

[0026] In step (2), the mass ratio of the filter residue to the chlorinated polyvinyl chloride powder is 1:2.5 to 3.5. As an example, the mass ratio can be, but is not limited to, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3.0, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5. The sum of the masses of the filter residue and the chlorinated polyvinyl chloride powder is M, and the volume of water is V. V / M is 20 to 30 L / kg. As an example, V / M can be, but is not limited to, 20 L / kg, 21 L / kg, 22 L / kg, 23 L / kg, 24 L / kg, 25 L / kg, 26 L / kg, 27 L / kg, 28 L / kg, 29 L / kg, 30 L / kg. During the water leaching step, the temperature is raised to 180 to 250 °C. As an example, the temperature can be, but is not limited to, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C. The heating rate is 3 to 5 °C / min. As an example, it can be, but is not limited to, 3 °C / min, 4 °C / min, 5 °C / min. The reaction time is 20 to 100 min. As an example, the reaction time can be, but is not limited to, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min.

[0027] The chlorinated polyvinyl chloride powder can be obtained by crushing waste chlorinated polyvinyl chloride products. The particle size of the chlorinated polyvinyl chloride powder is 0.1 to 1.0 μm. As an example, the particle size can be, but is not limited to, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm. The number average molecular weight of the chlorinated polyvinyl chloride in the chlorinated polyvinyl chloride powder > 50000, the chlorine content is 61 to 74 vol.%, and the thermal decomposition temperature < 120 °C. The waste chlorinated polyvinyl chloride products can be conventional consumer materials, such as materials used for various pipes, cables, etc. Using waste chlorinated polyvinyl chloride products can promote leaching, the raw material source is wide, and resource recovery can be realized, which has more advantages in recovery cost.

[0028] The leaching solution obtained by the method for leaching metals in the lithium cobalt oxide-based cathode sheet of the present invention can be further recycled. The recycling method includes: adding an alkali solution to the obtained leaching solution containing Li + and Co 2+ to precipitate Co(OH)2, and performing solid-liquid separation to recover metallic cobalt. Adding sodium carbonate to the filtrate to precipitate Li2CO3, and performing solid-liquid separation to recover metallic lithium. The alkali solution can be a sodium hydroxide solution, and the alkali solution is added to adjust the pH value of the leaching solution to 6.8 to 7.2.

[0029] In addition, the solid-liquid separation in the high-pressure separation step and the water leaching step can be centrifugation, filtration, suction filtration, etc.

[0030] To better illustrate the objectives, technical solutions, and beneficial effects of the present invention, the following will further explain the present invention in combination with specific embodiments. It should be noted that the methods described in the following embodiments are further explanatory illustrations of the present invention and should not be construed as limitations on the present invention.

[0031] Example 1 This example is a method for leaching metals from a lithium cobalt oxide-based positive electrode sheet, and the steps are as follows.

[0032] (1) High-pressure separation The lithium cobalt oxide-based positive electrode sheet disassembled from the No. 1 waste battery and methanol are placed in a high-pressure reaction kettle and mixed. The liquid-solid ratio of methanol to the lithium cobalt oxide-based positive electrode sheet is 10 L / kg. After purging the air with nitrogen, the high-pressure reaction kettle is sealed and heated to 220 °C at a rate of 4 °C / min until the binder dissolves in methanol to separate the lithium cobalt oxide positive electrode material from the aluminum foil to obtain a mixture. The mixture is filtered to obtain filter residue and filtrate, and the filtrate is recovered after evaporation at 90 °C.

[0033] (2) Water leaching The filter residue and polyvinyl chloride powder (the polyvinyl chloride powder is obtained by mechanically crushing waste polyvinyl chloride cable sleeves, with a particle size of 0.5 μm, the number average molecular weight of polyvinyl chloride in the polyvinyl chloride powder > 50000, a chlorine content of 61 - 62 vol.%, and a thermal decomposition temperature of 170 °C) are dispersed in water (V / M is 24 L / kg) at a mass ratio of 1:3.0 and put into a high-pressure reaction kettle and mixed evenly. The temperature is raised to 230 °C at a rate of 4 °C / min for reaction for 60 min until Li + and Co 2+ are leached into the water, and then filtered to obtain a leaching solution containing Li + and Co 2+ .

[0034] Example 2 This example is a method for leaching metals from a lithium cobalt oxide-based positive electrode sheet, and the steps are as follows.

[0035] (1) High-pressure separation The lithium cobalt oxide-based positive electrode sheet disassembled from the No. 2 waste battery and methanol are placed in a high-pressure reaction kettle and mixed. The liquid-solid ratio of methanol to the lithium cobalt oxide-based positive electrode sheet is 15 L / kg. After purging the air with nitrogen, the high-pressure reaction kettle is sealed and heated to 200 °C at a rate of 3 °C / min until the binder dissolves in methanol to separate the lithium cobalt oxide positive electrode material from the aluminum foil to obtain a mixture. The mixture is filtered to obtain filter residue and filtrate, and the filtrate is recovered after evaporation at 95 °C.

[0036] (2) Water leaching Disperse the filter residue and polyvinyl chloride powder (the polyvinyl chloride powder is obtained by mechanically crushing waste polyvinyl chloride cable sheaths, with a particle size of 0.8 μm, the number average molecular weight of polyvinyl chloride in the polyvinyl chloride powder > 50,000, chlorine content of 65 - 67 vol.%, and thermal decomposition temperature of 170 °C) in water (V / M is 28 L / kg) at a mass ratio of 1:3.5 and put it into a high-pressure reactor to mix evenly. Heat it to 200 °C at a rate of 5 °C / min for reaction for 90 min until Li + and Co 2+ are leached into water, and then filter to obtain the leaching solution containing Li + and Co 2+ .

[0037] Example 3 This example is a method for leaching metals in a lithium cobalt oxide-based positive electrode sheet, and its steps are as follows.

[0038] (1) High-pressure separation Put the lithium cobalt oxide-based positive electrode sheet disassembled from the 3# waste battery and methanol into a high-pressure reactor to mix. The liquid-solid ratio of methanol and the lithium cobalt oxide-based positive electrode sheet is 8 L / kg. After purging the air with argon, seal the high-pressure reactor and heat it to 190 °C at a rate of 5 °C / min until the binder dissolves in methanol to separate the lithium cobalt oxide positive electrode material from the aluminum foil to obtain a mixture. Filter the mixture to obtain a filter residue and a filtrate, and the filtrate is recovered after evaporation at 100 °C.

[0039] (2) Water leaching Disperse the filter residue and polyvinyl chloride powder (the polyvinyl chloride powder is obtained by mechanically crushing waste polyvinyl chloride cable sheaths, with a particle size of 1.0 μm, the number average molecular weight of polyvinyl chloride in the polyvinyl chloride powder > 50,000, chlorine content of 70 - 72 vol.%, and thermal decomposition temperature of 170 °C) in water (V / M is 21 L / kg) at a mass ratio of 1:2.8 and put it into a high-pressure reactor to mix evenly. Heat it to 230 °C at a rate of 5 °C / min for reaction for 45 min until Li + and Co 2+ are leached into water, and then filter to obtain the leaching solution containing Li + and Co 2+ .

[0040] Calculate the leaching rates of various metal ions in the leaching solutions of Examples 1 - 3, and the results are shown in Table 1. Carry out ion recovery on the leaching solutions obtained in Examples 1 - 3, and its recovery method is as follows. The recovery rates of various metal ions are shown in Table 1.

[0041] Recovery method: Add the leaching solution to a sodium hydroxide solution with a concentration of 13.0 wt.% to adjust the pH value of the leaching solution to 6.8 to precipitate Co(OH)2. Filter and take the filtrate, add saturated sodium carbonate solution and react for 3 h, and crystallize to precipitate lithium carbonate.

[0042] Table 1 Metal leaching rates and recovery rates of Examples 1 to 3

[0043] As can be seen from the results in Table 1, the leaching methods of Examples 1 to 3 first strip the lithium cobalt oxide cathode material through high pressure and high temperature, and then under high temperature and high pressure, the property of polyvinyl chloride powder decomposing to produce chlorine in water is used to produce hydrochloric acid to achieve high leaching rates of lithium and cobalt. Finally, precipitation with different alkaline solutions is used to separate and highly recover lithium and cobalt.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it is not limited to only those listed in the embodiments. Those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for leaching metal from a lithium cobalt oxide positive electrode sheet, characterized in that: The lithium cobalt oxide positive electrode sheet comprises a current collector and a lithium cobalt oxide material coating attached to the current collector, wherein the lithium cobalt oxide material coating comprises a lithium cobalt oxide positive electrode material, a binder and a conductive agent, including: (1) High-pressure separation The lithium cobalt oxide positive electrode sheet disassembled from the waste battery and methanol are placed in a high-pressure reactor and mixed, and after the inert gas is introduced to exhaust the air, the high-pressure reactor is sealed and heated to a certain temperature until the binder is dissolved in the methanol to separate the lithium cobalt oxide positive electrode material from the current collector to obtain a mixture, and the mixture is subjected to solid-liquid separation to obtain a filter residue and a filtrate; (2) Water leaching The filter residue and chlorinated polyvinyl chloride powder are dispersed in water and put into a high-pressure reactor for mixing, and the temperature is raised to above 160° C. for reaction until the Li in the lithium cobalt oxide positive electrode material is + and Co 2+ Soak in water, and then separate the solid and liquid to obtain Li + and Co 2+ of the leachate.

2. The method for leaching metal from a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The liquid-to-solid ratio of the methanol to the lithium cobalt oxide positive electrode sheet is 8-15 L / kg.

3. The method for leaching metal from a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The certain temperature in the high-pressure separation step is 180-250° C., the heating rate is 3-5° C. / min, and the insulation time is 10-30 min.

4. The method for leaching metal from a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The filtrate is evaporated at 80-100° C. to recover the methanol and applied to the high-pressure separation step.

5. The method for leaching metal from a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The mass ratio of the filter residue to the chlorinated polyvinyl chloride powder is 1:2.5-3.

5.

6. The method for leaching metal from a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The sum of the masses of the filter residue and the chlorinated polyvinyl chloride powder is M, the volume of the water is V, and V / M is 20-30 L / kg.

7. The method for leaching metal from a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: In the water leaching step, the temperature is raised to 180-250°C, the heating rate is 3-5°C / min, and the reaction time is 20-100min.

8. The method for leaching metal from a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The chlorinated polyvinyl chloride powder can be obtained by crushing waste chlorinated polyvinyl chloride products. The particle size of the chlorinated polyvinyl chloride powder is 0.1-1.0 μm. The number average molecular weight of the chlorinated polyvinyl chloride in the chlorinated polyvinyl chloride powder is greater than 50,000, the chlorine content is 61-74 vol.%, and the thermal decomposition temperature is less than 170°C.

9. A method for recovering metals from lithium cobalt oxide positive electrode sheets, characterized in that: include: (I) The method for leaching metal from a lithium cobalt oxide positive electrode sheet according to any one of claims 1 to 8 to obtain a Li-containing + and Co 2+ of the leachate; (II) adding alkaline solution to the leachate to precipitate Co(OH)2 and performing solid-liquid separation to recover metallic cobalt, and adding sodium carbonate to the filtrate to precipitate Li2CO3 and performing solid-liquid separation to recover metallic lithium.

10. Application of the method for recovering metals from lithium cobalt oxide positive electrode sheets according to claim 9 in lithium cobalt oxide secondary batteries, characterized in that: The recovery rate of lithium is ≥95%, and the recovery rate of cobalt is ≥90%.

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