Repairing and regenerating method of waste lithium iron phosphate positive electrode material

Abstract

The invention belongs to the technical field of battery material recovery and regeneration. More specifically, the invention relates to a method for repairing and regenerating a waste lithium iron phosphate positive electrode material. The regeneration method specifically comprises the following steps: battery disassembly: disassembling the lithium ion battery, and obtaining a positive pole piece, a negative pole piece and a diaphragm; the positive pole piece comprises a positive active material, and the positive active material is lithium iron phosphate; processing the positive pole piece: separating and removing the positive current collector to obtain a positive active material coating; treating a negative electrode plate and a diaphragm: soaking the negative electrode plate and the diaphragm in a citric acid solution, and heating and dipping to obtain a dipping solution; regeneration of the positive electrode active material: mixing the positive electrode active material coating and the impregnation liquid, performing heating ultrasonic treatment, performing freezing grinding and unfreezing, performing freezing grinding-unfreezing circulation for 5-10 times, performing drying, removing moisture, and performing high-temperature calcination so as to complete repair and regeneration of the waste lithium iron phosphate positive electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery material recycling and regeneration, and more specifically, relates to a method for repairing and regenerating waste lithium iron phosphate positive electrode materials. Background Art

[0002] As an important member of lithium-ion batteries, lithium iron phosphate batteries have the advantages of stable structure, long cycle life, low cost and excellent thermal safety performance. They are widely used in portable electronic devices, new energy vehicles, energy storage base stations and other fields. In recent years, with the continuous expansion of the electric vehicle and energy storage market, the high prices of transition metals (Ni, Co, Mn, etc.), the promotion and application of blade batteries, and the price-performance advantage highlighted by fiscal subsidies, the output and market share of lithium iron phosphate batteries have exploded. The general service life of lithium iron phosphate batteries is 7-8 years. After reaching the service life, due to the failure of the material structure, lithium iron phosphate batteries will be withdrawn from the use scene, forming retired lithium iron phosphate battery materials. If not handled, it will not only cause harm to the ecological environment, but also cause waste and loss of non-renewable resources such as lithium, iron and phosphorus.

[0003] The repair and regeneration of retired lithium iron phosphate materials refers to a series of reconstruction processes to supplement the missing elements and repair the structural defects of retired lithium iron phosphate materials to restore their electrochemical activity. The repair and regeneration of waste lithium iron phosphate batteries not only helps to alleviate the environmental pollution caused by their storage as waste materials, but also prolongs the service life of the positive electrode materials. It is a key link in realizing the recycling of non-renewable rare and precious resources. Summary of the invention

[0004] The technical problem to be solved by the present invention is: for existing retired lithium iron phosphate batteries, the positive electrode active materials therein need to be recovered and regenerated, while the conventional method requires additional addition of lithium source during the recycling and regeneration process, which will cause uncontrollable process and material waste. A method for repairing and regenerating discarded lithium iron phosphate positive electrode materials is provided.

[0005] The purpose of the present invention is to provide a method for repairing and regenerating waste lithium iron phosphate positive electrode materials.

[0006] The above-mentioned purpose of the present invention is achieved through the following technical solutions: A method for repairing and regenerating waste lithium iron phosphate positive electrode materials, the specific regeneration method comprising the following steps: Battery disassembly: Disassemble lithium-ion batteries and obtain positive electrode sheets, negative electrode sheets and separators; The positive electrode plate includes a positive electrode current collector and a positive electrode active material coating covering the surface of the positive electrode current collector; The positive electrode active material coating includes a positive electrode active material, and the positive electrode active material is lithium iron phosphate; Positive electrode processing: Separating and removing the positive electrode current collector to obtain a positive electrode active material coating; Negative electrode and diaphragm processing: The negative electrode sheet and the separator are soaked in a citric acid solution, and heated to obtain an impregnation solution; Regeneration of positive electrode active materials: After the positive electrode active material coating and the impregnation solution are mixed, they are subjected to ultrasonic treatment by heating, and then subjected to freeze grinding, thawing, and the freeze grinding-thawing cycle is repeated 5-10 times, followed by drying to remove moisture, and then subjected to high temperature calcination to complete the repair and regeneration of the waste lithium iron phosphate positive electrode material; In the process of freezing and grinding, as the water diffuses and penetrates into the pores of the coating, the water condenses to form ice crystals during the freezing process. The ice crystals shatter under the shear pressure of grinding, thereby further widening the pores. After thawing, it is beneficial for the impregnation liquid to further diffuse and penetrate into the pores, thereby avoiding the problem of poor diffusion of the impregnation liquid caused by local pore blockage.

[0007] Beneficial effects of the above technical solution: The above technical scheme is to disassemble the lithium-ion battery to obtain the positive electrode sheet, negative electrode sheet and separator of the corresponding lithium-ion battery. During the cycle of the battery, some lithium ions are embedded in the negative electrode, which are not completely discharged due to polarization and other reasons during the discharge process, or SEI film is formed on the surface of the negative electrode, and "dead lithium" is formed on the surface of the negative electrode sheet due to abnormal conditions. The loss of these parts of lithium ions leads to the lack of lithium ions when the positive electrode active material is directly regenerated. It is difficult to effectively control the addition of an external lithium source. If too little is added, the supplementary effect is limited. If too much is added, the lithium source is seriously wasted. Based on this, the present invention directly performs targeted recovery and regeneration of the above-mentioned various materials derived from the same lithium-ion battery.

[0008] Specifically, citric acid solution is used for immersion. During this process, the residual lithium ions in the negative electrode plate and the diaphragm are dissolved and enter into the impregnation solution. Subsequently, during the heating and ultrasonic treatment, the impregnation solution gradually diffuses and penetrates into the positive electrode active material coating. Since there are more carboxyl functional groups in the molecular structure of citric acid, it can be gradually adsorbed and fixed in the pores of the positive electrode active material coating during the penetration process. In addition, the present invention directly uses the positive electrode active material coating as the treatment raw material rather than the positive electrode active material. This is because there are rich pore structures in the positive electrode plate coating. These structures themselves are the channels for the diffusion and penetration of the electrolyte in each lithium-ion battery. In the above-mentioned treatment process, the impregnation solution can diffuse and penetrate. Since the channel itself is the conventional diffusion channel for lithium ions along with the electrolyte, the impregnation solution will actually diffuse and penetrate along the channel, thereby achieving a quantitative repair effect close to the in-situ.

[0009] Furthermore, the negative electrode plate and separator processing also includes: A citric acid solution with a concentration of 1.6-1.8 mol / L is used as the acid solution, the total mass of the negative electrode plate and the diaphragm is used as the solid mass, the acid solution, the negative electrode plate and the diaphragm are mixed according to a mass ratio of the acid solution mass to the solid mass of 8.5-9.0:1, and then heated and impregnated for 60-80 minutes at a temperature of 90-95°C, filtered, and the filtrate is collected to obtain an impregnation solution.

[0010] Furthermore, the negative electrode plate and separator processing also includes: The impregnation solution is concentrated under reduced pressure until the impregnation solution is concentrated to 0.3-0.4 times of its original volume to obtain a concentrated impregnation solution.

[0011] The inventors have found that if the impregnation solution is further concentrated, the lithium ion concentration in the impregnation solution can be increased, thereby reducing the uncontrollable loss of lithium ions during the diffusion process.

[0012] Furthermore, the positive electrode active material regeneration further comprises: After mixing the positive electrode active material coating and the concentrated impregnation solution, the mixture is subjected to heating ultrasonic treatment for 30-50 minutes at a temperature of 80-90°C and an ultrasonic frequency of 180-200kHz, and then continuously frozen to a solid state at a temperature of -18--30°C, and then ground for 10-15 minutes at a temperature preservation temperature. After natural thawing, the freezing, grinding and thawing cycle is repeated 5-10 times, and then the mixture is dried to remove moisture and then calcined at a high temperature to complete the repair and regeneration of the waste lithium iron phosphate positive electrode material.

[0013] Further, the high temperature calcination includes: In a mixed gas atmosphere of water vapor and carbon dioxide, heat to 350-380°C at a rate of 3-5°C / min, keep warm and calcine for 2-4 hours, continue to heat to 500-520°C at a rate of 0.8-1.5°C / min, keep warm and calcine for 2-4 hours, and then cool to room temperature.

[0014] Furthermore, in the mixed gas, the volume ratio of water vapor to carbon dioxide is 2.0-2.8:1.

[0015] During the high-temperature calcination process, water vapor and carbon dioxide gas are used as a protective atmosphere to first calcine at a lower temperature, and then the temperature is further increased to calcine at a higher temperature, so that the diffusion process of lithium ions is carried out in stages, avoiding a one-time rapid increase in temperature to a higher temperature that may cause the repair of lithium ions to fail.

[0016] Furthermore, the positive electrode plate processing also includes: Soak the positive electrode sheet in water for more than 30 minutes, then heat it to 120-150°C, and then immerse the heated positive electrode sheet in ice water at a temperature of 1-4°C for 20 minutes to separate the positive electrode current collector and the positive electrode active material coating. DETAILED DESCRIPTION

[0017] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0018] Unless otherwise specified, the reagents and materials used in the following examples are commercially available. Example 1

[0019] Battery disassembly: Take retired lithium iron phosphate batteries as the object, discharge them to a cut-off voltage of 2.5V, let them stand for 20 minutes, then disassemble the lithium-ion batteries, separate and remove the battery shell, and obtain the positive electrode sheet, negative electrode sheet and separator; Wherein, the positive electrode plate comprises a positive electrode current collector and a positive electrode active material coating covering the surface of the positive electrode current collector; The positive electrode active material coating includes a positive electrode active material, and the positive electrode active material is lithium iron phosphate; Positive electrode processing: The positive electrode sheet was soaked in water at room temperature for 30 minutes, then heated to 120°C, and then immersed in ice water at 1°C for 20 minutes to separate the positive electrode current collector and the positive electrode active material coating; then the positive electrode current collector was separated and removed, and the positive electrode active material coating remaining on the surface of the positive electrode current collector was brushed off with a brush, and the remaining material with the positive electrode active material coating was directly concentrated and dried to obtain the positive electrode active material coating; Negative electrode and diaphragm processing: A citric acid solution with a concentration of 1.6 mol / L is used as the acid solution, and the total mass of the negative electrode plate and the separator is used as the solid mass. The acid solution, the negative electrode plate and the separator are mixed according to a mass ratio of the acid solution mass to the solid mass of 8.5:1, and then heated and impregnated for 60 minutes at a temperature of 90°C, filtered, and the filtrate is collected to obtain an impregnation solution; The impregnation solution is concentrated under reduced pressure until the impregnation solution is concentrated to 0.3 times of its original volume to obtain a concentrated impregnation solution; Regeneration of positive electrode active materials: After the positive electrode active material coating and the concentrated impregnation solution obtained above are completely mixed, they are heated and ultrasonically treated for 30 minutes at a temperature of 80°C and an ultrasonic frequency of 180kHz, and then continuously frozen to a solid state at a temperature of -18°C, and then ground for 10 minutes at a temperature of keeping warm. After natural thawing, the freezing, grinding and thawing cycles are repeated 5 times, and then dried to remove moisture. Then, the mixture is heated to 350°C at a rate of 3°C / min in a mixed gas atmosphere of water vapor and carbon dioxide, and is kept warm and calcined for 2 hours. Then, the mixture is heated to 500°C at a rate of 0.8°C / min, and is kept warm and calcined for 2 hours, and then cooled to room temperature to complete the repair and regeneration of the waste lithium iron phosphate positive electrode material. In the mixed gas, the volume ratio of water vapor to carbon dioxide is 2.0:1. Example 2

[0020] Battery disassembly: Take retired lithium iron phosphate batteries as the object, discharge them to a cut-off voltage of 2.5V, let them stand for 20 minutes, then disassemble the lithium-ion batteries, separate and remove the battery shell, and obtain the positive electrode sheet, negative electrode sheet and separator; Wherein, the positive electrode plate comprises a positive electrode current collector and a positive electrode active material coating covering the surface of the positive electrode current collector; The positive electrode active material coating includes a positive electrode active material, and the positive electrode active material is lithium iron phosphate; Positive electrode processing: The positive electrode sheet was soaked in water at room temperature for 35 minutes, then heated to 130° C., and then immersed in ice water at 2° C. for 20 minutes to separate the positive electrode collector and the positive electrode active material coating; then the positive electrode collector was separated and removed, and the positive electrode active material coating remaining on the surface of the positive electrode collector was brushed off with a brush, and the remaining material with the positive electrode active material coating was directly concentrated and dried to obtain the positive electrode active material coating; Negative electrode and diaphragm processing: A citric acid solution with a concentration of 1.7 mol / L is used as the acid solution, and the total mass of the negative electrode plate and the separator is used as the solid mass. The acid solution, the negative electrode plate and the separator are mixed according to a mass ratio of the acid solution mass to the solid mass of 8.8:1, and then heated and impregnated for 70 minutes at a temperature of 92°C, filtered, and the filtrate is collected to obtain an impregnation solution; The impregnation solution is concentrated under reduced pressure until the impregnation solution is concentrated to 0.35 times of its original volume to obtain a concentrated impregnation solution; Regeneration of positive electrode active materials: After all the positive electrode active material coating and concentrated impregnation solution obtained above are mixed, they are heated and ultrasonically treated for 40 minutes at a temperature of 85°C and an ultrasonic frequency of 190kHz, and then continuously frozen to a solid state at a temperature of -20°C, and then ground at a temperature of 12 minutes. After natural thawing, the freezing, grinding and thawing cycle is repeated 8 times, and then dried to remove moisture. Then, the mixture is heated to 360°C at a rate of 4°C / min in a mixed gas atmosphere of water vapor and carbon dioxide, and is heat-calcined for 3 hours, and then heated to 510°C at a rate of 1.2°C / min, and is heat-calcined for 3 hours, and then cooled to room temperature to complete the repair and regeneration of the waste lithium iron phosphate positive electrode material; In the mixed gas, the volume ratio of water vapor to carbon dioxide is 2.5:1. Example 3

[0021] Battery disassembly: Take retired lithium iron phosphate batteries as the object, discharge them to a cut-off voltage of 2.5V, let them stand for 20 minutes, then disassemble the lithium-ion batteries, separate and remove the battery shell, and obtain the positive electrode sheet, negative electrode sheet and separator; Wherein, the positive electrode plate comprises a positive electrode current collector and a positive electrode active material coating covering the surface of the positive electrode current collector; The positive electrode active material coating includes a positive electrode active material, and the positive electrode active material is lithium iron phosphate; Positive electrode processing: The positive electrode sheet was soaked in water at room temperature for 40 minutes, then heated to 150° C., and then immersed in ice water at 4° C. for 20 minutes to separate the positive electrode collector and the positive electrode active material coating; then the positive electrode collector was separated and removed, and the positive electrode active material coating remaining on the surface of the positive electrode collector was brushed off with a brush, and the remaining material with the positive electrode active material coating was directly concentrated and dried to obtain the positive electrode active material coating; Negative electrode and diaphragm processing: A citric acid solution with a concentration of 1.8 mol / L is used as the acid solution, and the total mass of the negative electrode plate and the separator is used as the solid mass. The acid solution, the negative electrode plate and the separator are mixed according to a mass ratio of the acid solution mass to the solid mass of 9.0:1, and then heated and impregnated for 80 minutes at a temperature of 95°C, filtered, and the filtrate is collected to obtain an impregnation solution; The impregnation solution is concentrated under reduced pressure until the impregnation solution is concentrated to 0.4 times of its original volume to obtain a concentrated impregnation solution; Regeneration of positive electrode active materials: After the positive electrode active material coating and the concentrated impregnation solution obtained above are completely mixed, they are heated and ultrasonically treated for 50 minutes at a temperature of 90°C and an ultrasonic frequency of 200kHz, and then continuously frozen to a solid state at a temperature of -30°C, and then ground for 15 minutes at a temperature of keeping warm. After natural thawing, the freezing, grinding and thawing cycles are repeated 10 times, and then dried to remove moisture. Then, the mixture is heated to 380°C at a rate of 5°C / min in a mixed gas atmosphere of water vapor and carbon dioxide, and is kept warm and calcined for 4 hours, and then heated to 520°C at a rate of 1.5°C / min, and is kept warm and calcined for 4 hours, and then cooled to room temperature to complete the repair and regeneration of the waste lithium iron phosphate positive electrode material; In the mixed gas, the volume ratio of water vapor to carbon dioxide is 2.8:1. Example 4

[0022] Compared with Example 1, this embodiment is different in that: The high temperature calcination is: In a mixed gas atmosphere of water vapor and carbon dioxide, the temperature was raised to 500°C at a rate of 3°C / min, and after calcination for 2 hours, the mixture was cooled to room temperature; the other conditions remained unchanged. Example 5

[0023] Compared with Example 1, this embodiment is different in that: The high temperature calcination is: In a mixed gas atmosphere of water vapor and carbon dioxide, the temperature was raised to 380°C at a rate of 3°C / min, and after calcination for 2 hours, the mixture was cooled to room temperature; the other conditions remained unchanged. Example 6

[0024] Compared with Example 1, this embodiment is different in that: The impregnation solution is not concentrated but used directly, that is, it is directly mixed with the positive electrode active material coating; The rest of the conditions remain unchanged.

[0025] Comparative Example 1 Battery disassembly: Take retired lithium iron phosphate batteries as the object, discharge them to a cut-off voltage of 2.5V, let them stand for 20 minutes, then disassemble the lithium-ion batteries, separate and remove the battery shell, and obtain the positive electrode sheet, negative electrode sheet and separator; Wherein, the positive electrode plate comprises a positive electrode current collector and a positive electrode active material coating covering the surface of the positive electrode current collector; The positive electrode active material coating includes a positive electrode active material, and the positive electrode active material is lithium iron phosphate; Positive electrode processing: The positive electrode sheet was soaked in water at room temperature for 30 minutes, then heated to 120°C, and then immersed in ice water at 1°C for 20 minutes to separate the positive electrode collector and the positive electrode active material coating; then the positive electrode collector was separated and removed, and the positive electrode active material coating remaining on the surface of the positive electrode collector was brushed off with a brush, and the remaining material with the positive electrode active material coating was directly concentrated and dried to obtain the positive electrode active material coating; then it was calcined in a nitrogen atmosphere at a temperature of 650°C for 3 hours to remove the binder to obtain the positive electrode active material powder; Negative electrode and diaphragm processing: A citric acid solution with a concentration of 1.6 mol / L is used as the acid solution, and the total mass of the negative electrode plate and the separator is used as the solid mass. The acid solution, the negative electrode plate and the separator are mixed according to a mass ratio of the acid solution mass to the solid mass of 8.5:1, and then heated and impregnated for 60 minutes at a temperature of 90°C, filtered, and the filtrate is collected to obtain an impregnation solution; The impregnation solution is concentrated under reduced pressure until the impregnation solution is concentrated to 0.3 times of its original volume to obtain a concentrated impregnation solution; Regeneration of positive electrode active materials: After all the positive electrode active material powder and the concentrated impregnation solution obtained above are mixed, they are heated and ultrasonically treated for 30 minutes at a temperature of 80°C and an ultrasonic frequency of 180kHz, and then continuously frozen to a solid state at a temperature of -18°C, and then ground for 10 minutes at a temperature of keeping warm. After natural thawing, the freezing, grinding and thawing cycles are repeated 5 times, and then dried to remove moisture. Then, the mixture is heated to 350°C at a rate of 3°C / min in a mixed gas atmosphere of water vapor and carbon dioxide, and is kept warm and calcined for 2 hours. Then, the mixture is heated to 500°C at a rate of 0.8°C / min, and is kept warm and calcined for 2 hours, and then cooled to room temperature to complete the repair and regeneration of the waste lithium iron phosphate positive electrode material. In the mixed gas, the volume ratio of water vapor to carbon dioxide is 2.0:1.

[0026] Comparative Example 2 Battery disassembly: Take retired lithium iron phosphate batteries as the object, discharge them to a cut-off voltage of 2.5V, let them stand for 20 minutes, then disassemble the lithium-ion batteries, separate and remove the battery shell, and obtain the positive electrode sheet, negative electrode sheet and separator; Wherein, the positive electrode plate comprises a positive electrode current collector and a positive electrode active material coating covering the surface of the positive electrode current collector; The positive electrode active material coating includes a positive electrode active material, and the positive electrode active material is lithium iron phosphate; Positive electrode processing: The positive electrode sheet was soaked in water at room temperature for 30 minutes, then heated to 120°C, and then immersed in ice water at 1°C for 20 minutes to separate the positive electrode current collector and the positive electrode active material coating; then the positive electrode current collector was separated and removed, and the positive electrode active material coating remaining on the surface of the positive electrode current collector was brushed off with a brush, and the remaining material with the positive electrode active material coating was directly concentrated and dried to obtain the positive electrode active material coating; Regeneration of positive electrode active materials: A 0.1 mol / L lithium citrate solution was used as the impregnation solution; The positive electrode active material coating and the impregnation solution obtained above were mixed in a mass ratio of 1:10, heated and ultrasonically treated for 30 minutes at a temperature of 80°C and an ultrasonic frequency of 180kHz, and then continuously frozen to a solid state at a temperature of -18°C, and then ground for 10 minutes at a temperature of keeping warm. After natural thawing, the freezing, grinding and thawing cycles were repeated 5 times, and then dried to remove moisture. Then, the mixture was heated to 350°C at a rate of 3°C / min in a mixed gas atmosphere of water vapor and carbon dioxide, and was kept warm for calcination for 2 hours, and then continued to be heated to 500°C at a rate of 0.8°C / min, and was kept warm for calcination for 2 hours, and then cooled to room temperature to complete the repair and regeneration of the waste lithium iron phosphate positive electrode material; In the mixed gas, the volume ratio of water vapor to carbon dioxide is 2.0:1.

[0027] The performance of the lithium iron phosphate cathode material recovered and regenerated in the above examples and comparative examples was tested, and the specific test methods and test results are as follows: The lithium iron phosphate positive electrode material, the binder PVDF, and the conductive agent acetylene black are mixed in a mass ratio of 80:10:10. Specifically, the binder PVDF and the solvent NMP are first mixed, and stirred thoroughly to obtain a glue solution, and then acetylene black and the positive electrode material are added, stirred evenly, and then coated on the surface of the aluminum foil; the coated positive electrode sheet is dried and cut; According to the order of positive electrode shell, positive electrode sheet, electrolyte, diaphragm, electrolyte, lithium sheet, gasket, spring, and negative electrode shell, CR2032 button battery was assembled in a vacuum glove box, and finally pressed with a sealing machine, left to stand for 24 hours, and its electrochemical performance was tested; Among them, the diaphragm is Celgard2400 polypropylene microporous diaphragm, the lithium salt in the electrolyte is lithium hexafluorophosphate (concentration is 1 mol / L), and the solvent is a mixture of EC:DMC:DEC=1:1:1.

[0028] The assembled button battery was cross-current charged and discharged by the Blue Electric Test System (CT2001A), with a voltage window of 2.4-4.6V. The test was carried out at a constant temperature of 25°C, and the capacity retention rate after 200 cycles at 0.2C and the discharge specific capacity at 0.2C were obtained. The detailed test results are shown in Table 1. Table 1: Product performance test results ; It can be seen from the test results in Table 1 that the positive electrode material recycled and regenerated by the method of the present invention is comparable to the material regenerated by directly using a lithium source as a lithium supplement.

[0029] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for repairing and regenerating waste lithium iron phosphate positive electrode materials, characterized in that: The specific regeneration method includes the following steps: Battery disassembly: Disassemble lithium-ion batteries and obtain positive electrode sheets, negative electrode sheets and separators; The positive electrode plate includes a positive electrode current collector and a positive electrode active material coating covering the surface of the positive electrode current collector; The positive electrode active material coating includes a positive electrode active material, and the positive electrode active material is lithium iron phosphate; Positive electrode processing: Separating and removing the positive electrode current collector to obtain a positive electrode active material coating; Negative electrode and diaphragm processing: The negative electrode sheet and the separator are soaked in a citric acid solution, and heated to obtain an impregnation solution; Regeneration of positive electrode active materials: After the positive electrode active material coating and the impregnation liquid are mixed, they are heated and ultrasonically treated, and then frozen and ground. After thawing, the freeze-grinding-thawing cycle is repeated 5-10 times, and then dried to remove moisture, and then calcined at high temperature to complete the repair and regeneration of the waste lithium iron phosphate positive electrode material.

2. The method for repairing and regenerating waste lithium iron phosphate positive electrode materials according to claim 1, characterized in that: The negative electrode plate and separator processing also includes: A citric acid solution with a concentration of 1.6-1.8 mol / L is used as the acid solution, the total mass of the negative electrode plate and the diaphragm is used as the solid mass, the acid solution, the negative electrode plate and the diaphragm are mixed according to a mass ratio of the acid solution mass to the solid mass of 8.5-9.0:1, and then heated and impregnated for 60-80 minutes at a temperature of 90-95°C, filtered, and the filtrate is collected to obtain an impregnation solution.

3. The method for repairing and regenerating waste lithium iron phosphate positive electrode materials according to claim 2, characterized in that: The negative electrode plate and separator processing also includes: The impregnation solution is concentrated under reduced pressure until the impregnation solution is concentrated to 0.3-0.4 times of its original volume to obtain a concentrated impregnation solution.

4. The method for repairing and regenerating waste lithium iron phosphate positive electrode materials according to claim 3, characterized in that: The positive electrode active material regeneration further comprises: After mixing the positive electrode active material coating and the concentrated impregnation solution, the mixture is subjected to heating ultrasonic treatment for 30-50 minutes at a temperature of 80-90°C and an ultrasonic frequency of 180-200kHz, and then continuously frozen to a solid state at a temperature of -18--30°C, and then ground for 10-15 minutes at a temperature preservation temperature. After natural thawing, the freezing, grinding and thawing cycle is repeated 5-10 times, and then the mixture is dried to remove moisture and then calcined at a high temperature to complete the repair and regeneration of the waste lithium iron phosphate positive electrode material.

5. A method for repairing and regenerating waste lithium iron phosphate positive electrode materials according to any one of claims 1 to 4, characterized in that: The high temperature calcination comprises: In a mixed gas atmosphere of water vapor and carbon dioxide, heat to 350-380°C at a rate of 3-5°C / min, keep warm and calcine for 2-4 hours, continue to heat to 500-520°C at a rate of 0.8-1.5°C / min, keep warm and calcine for 2-4 hours, and then cool to room temperature.

6. The method for repairing and regenerating waste lithium iron phosphate positive electrode materials according to claim 5, characterized in that: In the mixed gas, the volume ratio of water vapor to carbon dioxide is 2.0-2.8:

1.

7. The method for repairing and regenerating waste lithium iron phosphate positive electrode materials according to claim 1, characterized in that: The positive electrode plate processing also includes: Soak the positive electrode sheet in water for more than 30 minutes, then heat it to 120-150°C, and then immerse the heated positive electrode sheet in ice water at a temperature of 1-4°C for 20 minutes to separate the positive electrode current collector and the positive electrode active material coating.