Electric-pulse desorption recovery method for positive electrode sheet of waste lithium-ion battery

Abstract

An electric-pulse desorption recovery method for a positive electrode sheet of a waste lithium-ion battery. The recovery method comprises the following steps: (1) after discharging the waste lithium-ion battery, disassembling same to obtain a positive electrode sheet, performing high-voltage pulse discharging on the positive electrode sheet, then sorting and screening to obtain a positive electrode material and an aluminium foil; and (2) performing infrared heating on the positive electrode material to obtain a positive electrode material powder, performing hydrothermal lithium-supplementing repair on the positive electrode material powder, and calcining the lithium-supplemented repaired material to obtain a regenerated lithium-ion battery positive electrode material. The recovery method has advantages such as low energy consumption, high efficiency in separating the aluminium foil and the positive electrode material, good dispersibility of positive electrode material particles, and a good hydrothermal lithium-supplementing effect, thus achieving the recovery and reuse of positive electrode sheets of waste lithium-ion batteries.

Description

A method for recycling waste lithium-ion battery positive electrode sheets by electric pulse desorption Technical Field

[0001] The embodiments of the present application relate to the field of resource recovery technology, for example, a method for electric pulse desorption and recovery of positive electrode sheets of waste lithium-ion batteries. Background Art

[0002] The lithium-ion battery industry has experienced rapid growth in recent years. Due to their high energy density, long cycle life, and lack of memory, lithium-ion batteries are widely used in consumer electronics, electric vehicles, and chemical energy storage, making them a research hotspot in the new energy sector. However, the rapid growth in the application and demand for lithium-ion batteries is generating a significant amount of scrapped batteries. It is estimated that by 2030, over 1,100 tons of retired lithium-ion batteries will be produced. This raises environmental concerns and challenges regarding resource recycling and reuse.

[0003] Used lithium-ion battery cathodes contain valuable metals such as nickel, cobalt, manganese, aluminum, and lithium, making them a valuable metal resource. Furthermore, used lithium-ion batteries also contain hazardous substances such as electrolytes and binders, which can cause serious environmental damage if improperly handled. Currently, the recycling rate is less than 5%. Therefore, recycling used lithium-ion batteries has significant economic and environmental implications.

[0004] At present, the main process of recycling waste lithium-ion batteries is to reduce the bonding effect of the binder through mechanical crushing, thermal decomposition, organic solvent or organic acid dissolution, separate the aluminum foil from the positive electrode material, and then selectively leach the metal elements in the positive electrode material through acid leaching, alkaline leaching or mixed leaching. Finally, metal elements, metal compounds, positive electrode materials, etc. are obtained through extraction, precipitation and other methods.

[0005] CN102694217A discloses a method for recovering positive electrode active materials from battery material scraps and slurry, which includes the following steps: loading the positive electrode sheets or dry positive electrode slurry to be recovered into a crusher, sieving them into powder, and placing the powder into a fluidized bed to remove conductive carbon and binder impurities; passing the gas at the top of the fluidized bed through a cyclone separator to remove entrained powder, then passing it through a fixed bed to remove harmful gases, and finally heating it and passing it into the fluidized bed for recycling; after the powder at the bottom is cooled, it is sieved to obtain qualified positive electrode powder.

[0006] CN101570347A discloses a method for recycling positive electrode materials for lithium-ion batteries, comprising: 1) soaking a positive electrode sheet in a mixed solvent comprising N-methylpyrrolidone and acetone or in N-methylpyrrolidone; 2) screening; and 3) adjusting the solid content or viscosity of the screened slurry to an appropriate range.

[0007] The aforementioned recycling process has problems such as long process flow, high energy consumption, high pollution, incomplete separation of active materials from aluminum foil, low impurity removal rate and valuable element recovery rate, making it difficult to guarantee the quality and electrochemical performance of the recycled positive electrode material. Therefore, direct lithium regeneration of waste lithium-ion battery positive electrode materials is an important recycling strategy that can simplify the process and reduce costs. However, after the positive electrode material is separated from the aluminum foil, the binder remaining between the positive electrode material particles leads to larger positive electrode material particle size and poor dispersion. Subsequent lithium regeneration using hydrothermal method has the problem of uneven contact between the positive electrode material and the lithium source.

[0008] Summary of the Invention

[0009] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0010] The embodiment of the present application provides an electric pulse desorption and recovery method for the positive electrode sheets of waste lithium-ion batteries. The recovery method described in the present application has the advantages of low energy consumption, high separation efficiency of aluminum foil and positive electrode material, good dispersion of positive electrode material particles, and good hydrothermal lithium replenishment effect, thereby realizing the recycling and reuse of waste lithium-ion battery positive electrode sheets.

[0011] The present invention provides a method for recycling waste lithium-ion battery positive electrode sheets by electric pulse desorption, which comprises the following steps:

[0012] (1) disassembling the waste lithium-ion batteries after discharge to obtain positive electrode sheets, subjecting the positive electrode sheets to high-voltage pulse discharge treatment, and obtaining positive electrode materials and aluminum foil through sorting and screening;

[0013] (2) The positive electrode material is subjected to infrared heating treatment to obtain positive electrode material powder, the positive electrode material powder is subjected to hydrothermal lithium replenishment and repair treatment, and the lithium replenishment and repaired material is calcined to obtain a regenerated lithium-ion battery positive electrode material.

[0014] The method for recycling waste lithium-ion battery positive electrode sheets described in the present application uses high-voltage pulse discharge technology to process waste lithium-ion battery positive electrode sheets. The high-voltage pulse discharge process produces various complex physical and chemical effects, forming a strong electric field, a non-equilibrium plasma channel, and accompanied by strong thermal energy and expansion pressure thermal energy. It can quickly heat the binder on the surface of the aluminum foil to its melting point, and the aluminum foil will not be broken down under a suitable voltage, thereby greatly improving the separation rate of the positive electrode material and the aluminum foil. The positive electrode material separated from the aluminum foil is subjected to infrared heating to decompose the binder, and then dispersed positive electrode material particles can be obtained through grinding and screening. The positive electrode material particles are efficiently separated without the need for high-temperature calcination of the positive electrode material as a whole. The high-purity and highly dispersed positive electrode material particles can be directly used for subsequent hydrothermal lithium replenishment and regeneration. They can be evenly mixed and fully contacted with the lithium source to achieve efficient lithium replenishment and repair. The resulting regenerated battery positive electrode material has excellent electrochemical properties.

[0015] Preferably, the discharging in step (1) comprises: immersing the waste lithium-ion battery in a sodium chloride solution for discharging.

[0016] Preferably, the mass concentration of the sodium chloride solution is 0.6-6%, for example, 0.6%, 1%, 2%, 3%, 5% or 6%.

[0017] Preferably, the soaking time is 24 to 48 hours, for example, 24 hours, 28 hours, 30 hours, 40 hours or 48 hours.

[0018] Preferably, the high-voltage pulse discharge treatment in step (1) includes: placing the positive electrode sheet between the metal plate and the plate electrode of the high-voltage pulse device, and discharging the metal plate and the plate electrode through positive and negative pulse power supplies.

[0019] Preferably, the pulse discharge frequency of the high-voltage pulse discharge treatment in step (1) is 50 to 200 Hz, for example, 50 Hz, 80 Hz, 100 Hz, 150 Hz or 200 Hz.

[0020] Preferably, the voltage of the high-voltage pulse discharge treatment is 20-35 kV, for example, 20 kV, 22 kV, 25 kV, 30 kV or 35 kV.

[0021] Preferably, the pulse power of the high-voltage pulse discharge treatment is 20-200 kW, for example, 20 kW, 50 kW, 80 kW, 100 kW or 200 kW.

[0022] Preferably, the pulse treatment time of the high-voltage pulse discharge treatment is 1 to 100 μs, for example, 1 μs, 5 μs, 10 μs, 50 μs or 100 μs.

[0023] Preferably, the particle size of the positive electrode material is 1 to 10 mm, for example, 1 mm, 2 mm, 5 mm, 8 mm or 10 mm.

[0024] Preferably, the infrared wavelength of the infrared heat treatment in step (2) is 2 to 15 μm, for example, 2 μm, 5 μm, 8 μm, 10 μm or 15 μm.

[0025] The infrared wavelength of the infrared heat treatment described in this application is the same as the particle size of most positive electrode materials. Therefore, the maximum oscillating electromagnetic field is generated at the contact point between the positive electrode material particles, and the temperature rises rapidly, causing the binder to decompose. After grinding and screening, dispersed positive electrode material particles can be obtained. During the heating process, the infrared wavelength can be adaptively adjusted according to the state of the powder screened out after the heat treatment. If a large number of large-block positive electrode material particles are found after screening, the infrared wavelength is adjusted and the infrared heating treatment steps are repeated until a binder-free positive electrode material powder is obtained.

[0026] Preferably, the power of the infrared heat treatment is 500-2000W, for example, 500W, 800W, 1000W, 1500W or 2000W.

[0027] Preferably, the infrared heat treatment time is 0.5 to 2 minutes, for example, 0.5 minutes, 0.8 minutes, 1 minute, 1.5 minutes or 2 minutes.

[0028] Preferably, the infrared heat treatment is followed by cooling, grinding and screening.

[0029] Preferably, the hydrothermal lithium replenishment treatment in step (2) comprises mixing the positive electrode material powder with a lithium salt solution and then performing a hydrothermal reaction.

[0030] Preferably, the mass volume ratio of the positive electrode material powder to the lithium salt solution is 1:(20-25) g / mL, for example: 1:20 g / mL, 1:21 g / mL, 1:22 g / mL, 1:23 g / mL, 1:24 g / mL or 1:25 g / mL, etc.

[0031] Preferably, the solute of the lithium salt solution includes any one of lithium hydroxide, lithium oxalate or lithium acetate, or a combination of at least two of them.

[0032] Preferably, the molar concentration of the lithium salt solution is 1 to 4 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L or 4 mol / L.

[0033] Preferably, the temperature of the hydrothermal reaction is 100-250°C, for example, 100°C, 120°C, 150°C, 200°C or 250°C.

[0034] Preferably, the hydrothermal reaction time is 2 to 10 hours, for example, 2 hours, 4 hours, 6 hours, 8 hours or 10 hours.

[0035] Preferably, the calcination temperature in step (2) is 700-900°C, for example, 700°C, 750°C, 800°C, 850°C or 900°C.

[0036] Preferably, the calcination time is 5 to 12 hours, for example, 5 hours, 6 hours, 8 hours, 10 hours or 12 hours.

[0037] As a preferred embodiment of the present application, the recovery method comprises the following steps:

[0038] (1) The waste lithium-ion battery is placed in a sodium chloride solution with a mass concentration of 0.6-6% and soaked for 24-48 hours for discharge, and then disassembled to obtain a positive electrode sheet. The positive electrode sheet is placed between a metal plate and a plate electrode of a high-voltage pulse device. The metal plate and the plate electrode are discharged by a positive and negative pulse power supply. The pulse discharge frequency is 50-200 Hz, the voltage is 20-35 kV, the pulse power is 20-200 kW, and the pulse processing time is 1-100 μs. After sorting and screening, a positive electrode material and aluminum foil with a particle size of 1-10 mm are obtained;

[0039] (2) The positive electrode material is subjected to infrared heating treatment at a wavelength of 2 to 15 μm and a power of 500 to 2000 W for 0.5 to 2 minutes to obtain a positive electrode material powder. After cooling, grinding and screening, the positive electrode material powder is mixed with a 1 to 4 mol / L lithium salt solution at a mass volume ratio of 1: (20 to 25) g / mL, and a hydrothermal reaction is carried out at 100 to 250° C. for 2 to 10 hours. The lithium-repaired material is calcined at 700 to 900° C. for 5 to 12 hours to obtain a regenerated lithium-ion battery positive electrode material.

[0040] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0041] (1) The embodiment of the present application uses high-voltage pulse discharge technology to process the positive electrode sheets of waste lithium-ion batteries, which can greatly improve the separation rate of the positive electrode material and the aluminum foil. The positive electrode material is then subjected to infrared heating treatment to efficiently separate the positive electrode material particles. Subsequent lithium replenishment and repair can make the regenerated positive electrode material have excellent electrochemical properties.

[0042] (2) The separation rate of the positive electrode material and the aluminum foil in the recycling method described in the embodiment of the present application can reach more than 91.1%, the purity of the obtained positive electrode material can reach more than 94.5%, the 0.1C first discharge capacity of the obtained battery can reach more than 158.7mAh / g, and the capacity retention rate after 100 cycles can reach more than 91%.

[0043] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0044] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0045] Example 1

[0046] This embodiment provides a method for recycling waste lithium-ion battery positive electrode sheets by electric pulse desorption, the recycling method comprising the following steps:

[0047] (1) The waste lithium-ion battery was immersed in a sodium chloride solution with a mass concentration of 0.6% for 48 hours for discharge, and then disassembled to obtain a positive electrode sheet. The positive electrode sheet was placed between a metal plate and a plate electrode of a high-voltage pulse device. The metal plate and the plate electrode were discharged by a positive and negative pulse power supply. The pulse discharge frequency was 100 Hz, the voltage was 25 kV, the pulse power was 50 kW, and the pulse processing time was 50 μs. After sorting and screening, a positive electrode material and aluminum foil with a particle size of 5 mm were obtained;

[0048] (2) The positive electrode material was infrared heated for 0.5 min at a wavelength of 5 μm and a power of 500 W to obtain a positive electrode material powder with an average particle size of 5 μm. After cooling, grinding and screening, 5 g of the positive electrode material powder was mixed with 75 mL of a lithium oxalate solution with a concentration of 3 mol / L, and then hydrothermally reacted at 200 ° C for 4 h. The lithium-repaired material was calcined at 700 ° C for 10 h to obtain a regenerated lithium-ion battery positive electrode material.

[0049] Example 2

[0050] This embodiment provides a method for recycling waste lithium-ion battery positive electrode sheets by electric pulse desorption, the recycling method comprising the following steps:

[0051] (1) The waste lithium-ion battery was placed in a sodium chloride solution with a mass concentration of 1% for 36 hours for discharge, and then disassembled to obtain a positive electrode sheet. The positive electrode sheet was placed between a metal plate and a plate electrode of a high-voltage pulse device. The metal plate and the plate electrode were discharged by a positive and negative pulse power supply. The pulse discharge frequency was 200 Hz, the voltage was 20 kV, the pulse power was 20 kW, and the pulse processing time was 100 μs. After sorting and screening, a positive electrode material and aluminum foil with a particle size of 10 mm were obtained;

[0052] (2) The positive electrode material was infrared heated for 1 minute at a wavelength of 10 μm and a power of 1000 W to obtain a positive electrode material powder. After cooling, grinding, and screening, it was found that there were still a large number of large-block positive electrode material particles. Therefore, step (3) was repeated and the infrared wavelength was adjusted to 12 μm. After grinding and screening, a positive electrode material powder with an average particle size of 12 μm was obtained. After mixing 2 g of the positive electrode material powder with 40 mL of a lithium acetate solution with a concentration of 1 mol / L, a hydrothermal reaction was carried out at 180°C for 8 hours. The lithium-repaired material was calcined at 900°C for 5 hours to obtain a regenerated lithium-ion battery positive electrode material.

[0053] Example 3

[0054] This embodiment provides a method for recycling waste lithium-ion battery positive electrode sheets by electric pulse desorption, the recycling method comprising the following steps:

[0055] (1) The waste lithium-ion battery was placed in a sodium chloride solution with a mass concentration of 5% for 24 hours for discharge, and then disassembled to obtain a positive electrode sheet. The positive electrode sheet was placed between a metal plate and a plate electrode of a high-voltage pulse device. The metal plate and the plate electrode were discharged by a positive and negative pulse power supply. The pulse discharge frequency was 50 Hz, the voltage was 30 kV, the pulse power was 100 kW, and the pulse processing time was 20 μs. After sorting and screening, a positive electrode material and aluminum foil with a particle size of 10 mm were obtained;

[0056] (2) The positive electrode material was infrared heated for 2 minutes at a wavelength of 15 μm and a power of 2000 W to obtain a positive electrode material powder with an average particle size of 18 μm. After cooling, grinding and screening, 1 g of the positive electrode material powder was mixed with 25 mL of a lithium hydroxide solution with a concentration of 1 mol / L, and a hydrothermal reaction was carried out at 200°C for 4 hours. The lithium-repaired material was calcined at 700°C for 10 hours to obtain a regenerated lithium-ion battery positive electrode material.

[0057] Example 4

[0058] The only difference between this embodiment and embodiment 1 is that the voltage of the high-voltage pulse discharge treatment is 10 kV, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0059] Example 5

[0060] The only difference between this embodiment and embodiment 1 is that the voltage of the high-voltage pulse discharge treatment is 40 kV, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0061] Example 6

[0062] The only difference between this embodiment and embodiment 1 is that the infrared wavelength of the infrared heat treatment is 1 μm, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0063] Example 7

[0064] The only difference between this embodiment and embodiment 1 is that the infrared wavelength of the infrared heat treatment is 50 μm, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0065] Comparative Example 1

[0066] In this comparative example, the aluminum foil and the positive electrode material were separated by solution immersion, and other conditions and parameters were exactly the same as those in Example 1.

[0067] (1) The waste lithium-ion battery was placed in a sodium chloride solution with a mass concentration of 0.6% for 48 hours for discharge, and then disassembled to obtain a positive electrode sheet. The positive electrode sheet was crushed and 160g was placed in 2L of a 1wt% sodium chloride aqueous solution at a temperature of 65°C. After stirring for 30 minutes, the sodium chloride aqueous solution was filtered to obtain a mixture of aluminum foil and positive electrode material, which was dried and sieved to obtain the positive electrode material and aluminum foil;

[0068] (2) The positive electrode material was infrared heated for 0.5 min at a wavelength of 5 μm and a power of 500 W to obtain a positive electrode material powder with an average particle size of 5 μm. After cooling, grinding and screening, 5 g of the positive electrode material powder was mixed with 75 mL of a lithium oxalate solution with a concentration of 3 mol / L, and then hydrothermally reacted at 200 ° C for 4 h. The lithium-repaired material was calcined at 700 ° C for 10 h to obtain a regenerated lithium-ion battery positive electrode material.

[0069] Comparative Example 2

[0070] The only difference between this comparative example and Example 1 is that no infrared heat treatment is performed, and other conditions and parameters are exactly the same as those in Example 1.

[0071] Performance testing:

[0072] The separation rate of the positive electrode material and the aluminum foil, as well as the purity of the positive electrode material, were tested. The recycled positive electrode material was made into a battery, and the battery's 0.1C initial discharge capacity and capacity retention after 100 cycles were tested. The test results are shown in Table 1:

[0073] Table 1

[0074] As can be seen from Table 1, from Examples 1-3, the separation rate of the positive electrode material and the aluminum foil by the recycling method described in the present application can reach more than 91.1%, the purity of the obtained positive electrode material can reach more than 94.5%, the 0.1C first discharge capacity of the obtained battery can reach more than 158.7 mAh / g, and the capacity retention rate after 100 cycles can reach more than 91%.

[0075] By comparing Example 1 with Examples 4-5, it can be seen that in the recycling method described in the present application, the voltage of the high-voltage pulse discharge treatment will affect the recovery effect. The recovery effect is better when the voltage of the high-voltage pulse discharge treatment is controlled at 20-35 kV. If the voltage of the high-voltage pulse discharge treatment is too high, the aluminum foil will be broken through, causing aluminum foil fragments to mix into the positive electrode material, reducing the purity. If the voltage of the high-voltage pulse discharge treatment is too low, the heat generated is not enough to decompose the binder, and the positive electrode material and the aluminum foil cannot be effectively separated.

[0076] By comparing Example 1 with Examples 6-7, it can be seen that in the recovery method described in the present application, the infrared wavelength of high infrared heat treatment will affect the recovery effect. The recovery effect is better when the infrared wavelength of infrared heat treatment is controlled within 2 to 15 μm. If the infrared wavelength of infrared heat treatment is too long, it exceeds the particle size range of most positive electrode materials, making it difficult to separate the particles. If the infrared wavelength of infrared heat treatment is too short, it does not reach the particle size of the positive electrode material, and the temperature of the bonding point between the particles cannot be quickly increased, thereby reducing the particle separation efficiency.

[0077] By comparing Example 1 and Comparative Example 1, it can be seen that the present application uses high-voltage pulse discharge technology to process the positive electrode sheets of waste lithium-ion batteries. The high-voltage pulse discharge process produces various complex physical and chemical effects, forming a strong electric field, a non-equilibrium plasma channel, and accompanied by strong thermal energy and expansion pressure thermal energy, which can quickly heat the adhesive on the surface of the aluminum foil to its melting point, and the aluminum foil will not be broken down under a suitable voltage, thereby greatly improving the separation rate between the positive electrode material and the aluminum foil.

[0078] As can be seen from the comparison between Example 1 and Comparative Example 2, the present application subjects the positive electrode material after separation from the aluminum foil to infrared heating. The wavelength of the infrared light is the same as the particle size of most positive electrode materials. Therefore, the maximum oscillating electromagnetic field is generated at the contact points between the positive electrode material particles, rapidly increasing the temperature and decomposing the binder. After grinding and screening, dispersed positive electrode material particles can be obtained. The positive electrode material particles are efficiently separated without the need for high-temperature calcination of the entire positive electrode material, resulting in high-purity, highly dispersed positive electrode material particles.

[0079] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A method for electric pulse desorption and recovery of positive electrode sheets of waste lithium-ion batteries, wherein: The recovery method comprises the following steps: (1) disassembling the waste lithium-ion batteries after discharge to obtain positive electrode sheets, subjecting the positive electrode sheets to high-voltage pulse discharge treatment, and obtaining positive electrode materials and aluminum foil through sorting and screening; (2) The positive electrode material is subjected to infrared heating treatment to obtain positive electrode material powder, the positive electrode material powder is subjected to hydrothermal lithium replenishment and repair treatment, and the lithium replenishment and repair material is calcined to obtain a regenerated lithium ion battery positive electrode material.

2. The recycling method according to claim 1, wherein: The discharging in step (1) comprises: immersing the waste lithium-ion battery in a sodium chloride solution for discharging.

3. The recycling method according to claim 2, wherein: The mass concentration of the sodium chloride solution is 0.6-6%.

4. The recovery method according to claim 2 or 3, wherein: The soaking time is 24 to 48 hours.

5. The recovery method according to claims 1 to 4, wherein: The high-voltage pulse discharge treatment in step (1) includes: placing the positive electrode sheet between the metal plate and the plate electrode of the high-voltage pulse device, and discharging the metal plate and the plate electrode through positive and negative pulse power supplies.

6. The recovery method according to any one of claims 1 to 5, wherein: The pulse discharge frequency of the high voltage pulse discharge treatment in step (1) is 50 to 200 Hz; Preferably, the voltage of the high-voltage pulse discharge treatment is 20 to 35 kV; Preferably, the pulse power of the high-voltage pulse discharge treatment is 20 to 200 kW; Preferably, the pulse treatment time of the high voltage pulse discharge treatment is 1 to 100 μs; Preferably, the particle size of the positive electrode material is 1 to 10 mm.

7. The recovery method according to any one of claims 1 to 6, wherein: The infrared wavelength of the infrared heat treatment in step (2) is 2 to 15 μm; Preferably, the power of the infrared heat treatment is 500-2000W; Preferably, the infrared heat treatment time is 0.5 to 2 minutes; Preferably, the infrared heat treatment is followed by cooling, grinding and screening.

8. The recovery method according to any one of claims 1 to 7, wherein: The hydrothermal lithium-replenishing treatment in step (2) includes mixing the positive electrode material powder with a lithium salt solution and then performing a hydrothermal reaction.

9. The recycling method according to claim 8, wherein: The mass volume ratio of the positive electrode material powder to the lithium salt solution is 1:(20-25) g / mL; Preferably, the solute of the lithium salt solution includes any one of lithium hydroxide, lithium oxalate or lithium acetate, or a combination of at least two thereof; Preferably, the molar concentration of the lithium salt solution is 1 to 4 mol / L.

10. The recovery method according to claim 8 or 9, wherein: The temperature of the hydrothermal reaction is 100-250°C; Preferably, the hydrothermal reaction time is 2 to 10 hours.

11. The recycling method according to any one of claims 1 to 10, wherein: The calcination temperature in step (2) is 700-900° C. Preferably, the calcination time is 5 to 12 hours.

12. The recovery method according to any one of claims 1 to 11, wherein: The recovery method comprises the following steps: (1) placing the waste lithium-ion battery in a sodium chloride solution with a mass concentration of 0.6-6% for 24-48 hours for discharge, disassembling to obtain a positive electrode sheet, placing the positive electrode sheet between a metal plate and a plate electrode of a high-voltage pulse device, and discharging the metal plate and the plate electrode through a positive and negative pulse power supply, wherein the pulse discharge frequency is 50-200 Hz, the voltage is 20-35 kV, the pulse power is 20-200 kW, and the pulse processing time is 1-100 μs, and then sorting and screening to obtain a positive electrode material and aluminum foil with a particle size of 1-10 mm; (2) The positive electrode material is subjected to infrared heating treatment at a wavelength of 2 to 15 μm and a power of 500 to 2000 W for 0.5 to 2 min to obtain a positive electrode material powder. After cooling, grinding and screening, the positive electrode material powder is mixed with a 1 to 4 mol / L lithium salt solution at a mass volume ratio of 1: (20 to 25) g / mL, and a hydrothermal reaction is carried out at 100 to 250° C. for 2 to 10 hours. The lithium-repaired material is calcined at 700 to 900° C. for 5 to 12 hours to obtain a regenerated lithium-ion battery positive electrode material.

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