A method for recycling and regenerating lithium iron phosphate battery materials using liquid phase

Abstract

The present invention belongs to the technical field of secondary battery materials. More specifically, it relates to a method for recycling and regenerating lithium iron phosphate battery materials using a liquid phase. The method of the present invention comprises: peeling off the surface active material layer of the positive electrode plate to obtain a positive electrode active material layer, then mixing it with NMP, and heating it with microwave ultrasound to react to obtain a positive electrode active material; mixing the positive electrode active material and a mixed acid solution, adding hydrogen peroxide, heating for acid leaching reaction, filtering, and collecting the leachate; adjusting the pH of the leachate to 3.5, filtering, removing the precipitate, and then replenishing the lithium source, adjusting the molar ratio of Li:Fe:P to 1.05:1:1, and then adjusting the pH to 9.0. After reacting at a temperature of 50-60°C, heating to 80°C, standing for aging, filtering, and drying to obtain a dry precursor; calcining the dry precursor in a reducing atmosphere, cooling, and discharging to obtain a regenerated lithium iron phosphate material.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary battery materials and more specifically relates to a method for recovering and regenerating lithium iron phosphate battery materials using a liquid phase. Background Art

[0002] The liquid-phase method for recycling and regenerating lithium iron phosphate battery cathode materials is an efficient, environmentally friendly, and economical method. This process primarily involves dissolution, separation, purification, and regeneration. For example, acid leaching is a common method. A mild organic acid, such as citric acid or oxalic acid, or a low-concentration inorganic acid, such as sulfuric acid or hydrochloric acid, is first used to avoid iron dissolution or phosphorus loss caused by strong acid solutions. A reducing agent is then added to reduce any ferric ions present to ferrous ions. Temperature and acid concentration must be controlled to ensure the effectiveness of the acid leaching process. The pH is then adjusted to retain ferrous and phosphate ions in the solution, while impurities such as chloride ions precipitate. Finally, the ferrous ions are precipitated as Fe₃(PO₄)₂, separating the lithium⁺ and the iron₂⁺. This precipitate is then mixed with a lithium source and calcined in an inert atmosphere to obtain the regenerated lithium iron phosphate cathode material.

[0003] Based on the above description, it can be seen that the traditional recovery and regeneration process is complicated, and a large amount of additives, especially acidic solutions, are consumed in the process, which puts great pressure on the environment. Therefore, how to develop a simpler and more environmentally friendly recovery and regeneration method is one of the technical difficulties still faced by technicians in this field. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing acid leaching method for recovering and regenerating cathode materials from lithium iron phosphate batteries uses strong acid solutions, which can easily put significant pressure on the environment, while using organic acids results in low acid leaching efficiency. To address this problem, the present invention provides a liquid-phase method for recovering and regenerating lithium iron phosphate battery materials.

[0005] The purpose of the present invention is to provide a method for recycling and regenerating lithium iron phosphate battery materials using a liquid phase.

[0006] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0007] A method for recycling and regenerating lithium iron phosphate battery materials using liquid phase, the specific method comprising the following steps:

[0008] Disassemble the lithium iron phosphate battery and recycle the positive electrode;

[0009] The surface active material layer of the positive electrode sheet is peeled off to obtain a positive electrode active material layer, which is then mixed with NMP at a mass ratio of 1:8-10, subjected to microwave ultrasonic heating reaction, and then filtered, washed and dried to obtain a positive electrode active material;

[0010] By using NMP as a solvent, it can quickly and evenly penetrate into the internal pores under the action of ultrasound, effectively swelling and dissolving the binder. In combination with microwave heating, microwaves can directly act on the carbon conductive agent in the positive electrode active material layer. Thanks to the uniform distribution of the conductive agent itself, heat is quickly and evenly transferred internally, accelerating the swelling and dissolution of the binder by NMP.

[0011] The positive electrode active material and the mixed acid solution are mixed in a mass ratio of 1:8.5-9.0, and hydrogen peroxide is added at a mass ratio of 10-12% of the mass of the mixed acid solution. After heating and acid leaching at a temperature of 50-90°C for 2-3 hours, the leachate is filtered and collected;

[0012] The mixed acid solution is prepared by mixing a malic acid solution having a concentration of 1.8-2.2 mol / L and a citric acid solution having a concentration of 1.5-2.0 mol / L in a mass ratio of 1:1.

[0013] The above technical solution first uses a combination of malic acid and citric acid to replace traditional sulfuric acid or a single citric acid system to achieve an efficient and environmentally friendly leaching process. Specifically, malic acid can ionize to generate hydrogen ions at a lower temperature, thereby achieving the dissolution of ferrous ions, and after dissolution, it forms a moderately stable complex with the ferrous ions, thereby promoting the dissolution of Fe while avoiding excessive binding. Citric acid can preferentially and firmly complex the iron ions in the system, avoiding the formation of precipitates coating the surface of the positive electrode material, thereby affecting the mass transfer process of the acid leaching process and affecting the acid leaching efficiency. At the same time, citric acid can also react with hydrogen peroxide to generate active hydroxyl radicals, which destroy the passivation layer on the surface of the lithium iron phosphate and accelerate the leaching efficiency.

[0014] Since organic acid is used to replace sulfuric acid, the final wastewater can be biodegraded, thus ensuring environmental protection;

[0015] The leachate was adjusted to pH 3.5, filtered, and the precipitate was removed. A lithium source was then added to adjust the molar ratio of Li:Fe:P to 1.05:1:1, and the pH was adjusted to 9.0. The reaction was carried out at a temperature of 50-60°C, and then the temperature was raised to 80°C. After aging for 4 hours, the precursor was filtered and dried to obtain a dry precursor.

[0016] The dried precursor is calcined in a reducing atmosphere at a temperature of 650-670° C. for 6-8 hours, cooled, and discharged to obtain the regenerated lithium iron phosphate material.

[0017] The above technical solution adjusts the pH to 3.5, causing the trivalent iron ions in the system to precipitate out in the form of precipitation, which is then removed by filtration. After replenishing the lithium source and achieving the corresponding ratio, the pH is adjusted to 9.0 to begin to form a precursor precipitate. During the aging process, the crystallinity of the precursor is further improved, and finally the regeneration of the lithium iron phosphate material is achieved through calcination in a reducing atmosphere.

[0018] Furthermore, the microwave ultrasonic heating reaction includes:

[0019] The microwave-ultrasonic reaction was carried out for 2-2.5 hours under the conditions of microwave power of 300-320 W and ultrasonic frequency of 80-100 kHz.

[0020] Furthermore, the specific method also includes:

[0021] Anhydrous ethanol of an equal volume to the leachate is added to the leachate, and then the pH is adjusted to 3.5, filtered, and the precipitate is removed. Then, a lithium source is supplemented, and the molar ratio of Li:Fe:P is adjusted to 1.05:1:1. The pH is then adjusted to 9.0. After reacting at a temperature of 50-60°C, the temperature is raised to 80°C, and after aging for 4 hours, the mixture is transferred to a high-pressure reactor and reacted at a temperature of 180-190°C for 8-10 hours. The mixture is then cooled, discharged, filtered, and dried to obtain a dry precursor.

[0022] The beneficial effects of the above technical solution are:

[0023] The above technical solution further adds anhydrous ethanol to the leachate. Ethanol, as a polar solvent, can improve the system's wetting of the lithium iron phosphate material and accelerate the interfacial reaction. In addition, it can balance the oxidizing effect of hydrogen peroxide and prevent ferrous ions from being excessively oxidized to ferric ions.

[0024] Furthermore, the specific method also includes:

[0025] An equal volume of anhydrous ethanol is added to the leachate, and then the pH is adjusted to 3.5. The mixture is filtered to remove the precipitate, and then a lithium source is added to adjust the molar ratio of Li:Fe:P to 1.05:1:1. The pH is then adjusted to 9.0. After reacting at a temperature of 50-60°C, a dopamine solution of 6-8% by weight of the leachate is added. The mixture is then heated to 80°C, allowed to stand for aging for 4 hours, and then transferred to a high-pressure reactor. After high-temperature reaction at a temperature of 180-190°C for 8-10 hours, the mixture is cooled, discharged, filtered, and dried to obtain a dry precursor.

[0026] Wherein, the concentration of the dopamine solution is 8-10 g / L.

[0027] The beneficial effects of the above technical solution are:

[0028] The above technical solution further introduces dopamine into the system, and uses dopamine to oxidatively polymerize on the surface of the precursor at a pH of 9.0 to form a polymer coating containing carbon and nitrogen elements. This coating can be converted into an SP2 hybrid carbon coating under subsequent calcination temperature conditions, and its conductive performance is better than that of the traditional sucrose carbon coating. In addition, the presence of nitrogen can form pyridine nitrogen in the coating after calcination, further promoting the transfer of electrons. In addition, the functional groups in dopamine can form coordination bonds with ferrous ions or phosphate ions, inhibiting the agglomeration of precursor particles and improving the uniformity of precursor particles. The choice of timing for adding dopamine can partially embed it into the crystal lattice of the precursor during the aging process to form nitrogen doping, thereby improving the intrinsic conductivity of the material.

[0029] Furthermore, the specific method also includes:

[0030] The dried precursor is heated to 650-670°C in a reducing atmosphere at a rate of 0.8-1.5°C / min, kept warm and calcined for 6-8 hours, cooled to room temperature with the furnace, and discharged to obtain the regenerated lithium iron phosphate material.

[0031] Furthermore, the reducing atmosphere is formed by mixing nitrogen and hydrogen in a volume ratio of 9-9.5:1.

[0032] Furthermore, the specific method also includes:

[0033] The positive electrode active material and the mixed acid solution are mixed in a mass ratio of 1:8.5-9.0, and hydrogen peroxide is added at a mass ratio of 10-12% of the mass of the mixed acid solution. The mixture is first heated and acid-leached for 1-1.5 hours at a temperature of 50-60°C and a stirring speed of 200-220 r / min, and then heated and acid-leached for 1-1.5 hours at a temperature of 80-90°C and a stirring speed of 150-180 r / min. The leachate is then filtered and collected.

[0034] The beneficial effects of the above technical solution are:

[0035] By further regulating the acid leaching process, distributed acid leaching reactions are carried out under two-stage reaction temperature steps. In the temperature range of 50-60°C, malic acid dominates the dissolution process, while in the temperature range of 80-90°C, citric acid dominates the deep complexation process. By regulating the temperature, the effects of both are fully exerted, thereby improving the acid leaching effect.

[0036] Furthermore, the mass fraction of the hydrogen peroxide is 28-32%. DETAILED DESCRIPTION

[0037] The present invention is further described below with reference to specific examples, which, however, are not intended to limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0038] Unless otherwise specified, the reagents and materials used in the following examples were commercially available. Example 1

[0039] Disassemble the lithium iron phosphate battery and recycle the positive electrode sheet: Specifically, remove the electrolyte, negative electrode sheet and separator by separation, retain the positive electrode sheet, and use DMC to soak and clean the positive electrode sheet to remove the lithium salt and other electrolytes remaining on the surface or in the pores of the positive electrode sheet. When cleaning again, DMC can be used for continuous soaking for 8 hours;

[0040] The positive electrode sheet was immersed in N-methylpyrrolidone (NMP) and subjected to ultrasonic stripping for 1 h at a temperature of 60°C and an ultrasonic frequency of 180 kHz. The positive electrode current collector was then separated and removed, and the positive electrode active material layer was collected.

[0041] It was then mixed with NMP at a mass ratio of 1:8, and subjected to microwave ultrasonic reaction for 2 h under microwave power of 300 W and ultrasonic frequency of 80 kHz. The mixture was then filtered, washed, and dried to obtain a positive electrode active material.

[0042] The positive electrode active material and the mixed acid solution were mixed in a mass ratio of 1:8.5, and hydrogen peroxide with a mass ratio of 10% of the mixed acid solution was added. The mixture was first heated and acid-leached at 50°C and a stirring speed of 200 r / min for 1 hour, and then heated and acid-leached at 80°C and a stirring speed of 150 r / min for 1 hour. The leachate was then filtered and collected.

[0043] The mass fraction of the hydrogen peroxide is 28%;

[0044] The mixed acid solution is prepared by mixing a malic acid solution with a concentration of 1.8 mol / L and a citric acid solution with a concentration of 1.5 mol / L in a mass ratio of 1:1.

[0045] Anhydrous ethanol equal in volume to the leachate was added to the leachate, and then the pH was adjusted to 3.5, filtered, and the precipitate was removed. Subsequently, lithium hydroxide was used as a lithium source to supplement the lithium source, and the molar ratio of Li:Fe:P was adjusted to 1.05:1:1. The pH was then adjusted to 9.0, and the reaction was carried out at a temperature of 50°C and a stirring speed of 200 r / min for 30 minutes. A dopamine solution of 6% by mass of the leachate was added, and the temperature was then raised to 80°C. After continued stirring and mixing for 10 minutes, the mixture was allowed to stand for aging for 4 hours, and then transferred to a high-pressure reactor. After high-temperature reaction for 8 hours at a temperature of 180°C and a stirring speed of 400 r / min, the mixture was cooled, discharged, filtered, and dried to obtain a dry precursor.

[0046] Wherein, the concentration of the dopamine solution is 8 g / L;

[0047] The dried precursor was heated to 650°C at a rate of 0.8°C / min in a reducing atmosphere, kept at this temperature for 6 hours, cooled to room temperature, and discharged to obtain the regenerated lithium iron phosphate material;

[0048] The reducing atmosphere is formed by mixing nitrogen and hydrogen in a volume ratio of 9:1. Example 2

[0049] Disassemble the lithium iron phosphate battery and recycle the positive electrode sheet: Specifically, remove the electrolyte, negative electrode sheet and separator by separation, retain the positive electrode sheet, and use DMC to soak and clean the positive electrode sheet to remove the lithium salt and other electrolytes remaining on the surface or in the pores of the positive electrode sheet. When cleaning again, DMC can be used for continuous soaking for 8 hours;

[0050] The positive electrode sheet was immersed in N-methylpyrrolidone (NMP) and subjected to ultrasonic stripping for 1 h at a temperature of 60°C and an ultrasonic frequency of 180 kHz. The positive electrode current collector was then separated and removed, and the positive electrode active material layer was collected.

[0051] It was then mixed with NMP at a mass ratio of 1:9, and subjected to microwave ultrasonic reaction for 2.2 h at a microwave power of 310 W and an ultrasonic frequency of 90 kHz. The mixture was then filtered, washed, and dried to obtain a positive electrode active material.

[0052] The positive electrode active material and the mixed acid solution were mixed in a mass ratio of 1:8.8, and hydrogen peroxide with a mass ratio of 11% of the mixed acid solution was added. The mixture was first heated at a temperature of 55°C and a stirring speed of 210 r / min for acid leaching for 1.2 h, and then heated at a temperature of 86°C and a stirring speed of 160 r / min for acid leaching for 1.2 h. The leachate was then filtered and collected.

[0053] The mass fraction of the hydrogen peroxide is 30%;

[0054] The mixed acid solution is prepared by mixing a 2.0 mol / L malic acid solution and a 1.8 mol / L citric acid solution in a mass ratio of 1:1.

[0055] Anhydrous ethanol equal in volume to the leachate was added to the leachate, and then the pH was adjusted to 3.5, filtered, and the precipitate was removed. Subsequently, lithium hydroxide was used as a lithium source to supplement the lithium source, and the molar ratio of Li:Fe:P was adjusted to 1.05:1:1. The pH was then adjusted to 9.0, and the reaction was carried out at a temperature of 56°C and a stirring speed of 200 r / min for 30 minutes. A dopamine solution of 7% by mass of the leachate was added, and the temperature was then raised to 80°C. After continued stirring and mixing for 10 minutes, the mixture was allowed to stand for aging for 4 hours, and then transferred to a high-pressure reactor. After high-temperature reaction for 9 hours at a temperature of 186°C and a stirring speed of 400 r / min, the mixture was cooled, discharged, filtered, and dried to obtain a dry precursor.

[0056] Wherein, the concentration of the dopamine solution is 9 g / L;

[0057] The dried precursor was heated to 660°C in a reducing atmosphere at a rate of 1.2°C / min, kept at this temperature for 7 hours, cooled to room temperature, and discharged to obtain the regenerated lithium iron phosphate material;

[0058] The reducing atmosphere is formed by mixing nitrogen and hydrogen in a volume ratio of 9.2:1. Example 3

[0059] Disassemble the lithium iron phosphate battery and recycle the positive electrode sheet: Specifically, remove the electrolyte, negative electrode sheet and separator by separation, retain the positive electrode sheet, and use DMC to soak and clean the positive electrode sheet to remove the lithium salt and other electrolytes remaining on the surface or in the pores of the positive electrode sheet. When cleaning again, DMC can be used for continuous soaking for 8 hours;

[0060] The positive electrode sheet was immersed in N-methylpyrrolidone (NMP) and subjected to ultrasonic stripping for 1 h at a temperature of 60°C and an ultrasonic frequency of 180 kHz. The positive electrode current collector was then separated and removed, and the positive electrode active material layer was collected.

[0061] It was then mixed with NMP at a mass ratio of 1:10, and subjected to microwave ultrasonic reaction for 2.5 h under microwave power of 320 W and ultrasonic frequency of 100 kHz. The mixture was then filtered, washed, and dried to obtain a positive electrode active material.

[0062] The positive electrode active material and the mixed acid solution were mixed in a mass ratio of 1:9.0, and hydrogen peroxide with a mass ratio of 12% of the mixed acid solution was added. The mixture was first heated and acid-leached for 1.5 hours at a temperature of 60°C and a stirring speed of 220 r / min, and then heated and acid-leached for 1.5 hours at a temperature of 90°C and a stirring speed of 180 r / min. The leachate was then filtered and collected.

[0063] The mass fraction of the hydrogen peroxide is 32%;

[0064] The mixed acid solution is prepared by mixing a 2.2 mol / L malic acid solution and a 2.0 mol / L citric acid solution in a mass ratio of 1:1.

[0065] Anhydrous ethanol of the same volume as the leachate was added to the leachate, and then the pH was adjusted to 3.5, filtered, and the precipitate was removed. Subsequently, lithium hydroxide was used as a lithium source to supplement the lithium source, and the molar ratio of Li:Fe:P was adjusted to 1.05:1:1. The pH was then adjusted to 9.0, and the reaction was carried out at a temperature of 60°C and a stirring speed of 200 r / min for 30 minutes. A dopamine solution of 8% by mass of the leachate was added, and then the temperature was raised to 80°C, and the stirring was continued for 10 minutes. After aging for 4 hours, the product was transferred to a high-pressure reactor, and the product was reacted at a temperature of 190°C and a stirring speed of 400 r / min for 10 hours. After cooling, discharging, filtering, and drying, a dry precursor was obtained.

[0066] Wherein, the concentration of the dopamine solution is 10 g / L;

[0067] The dried precursor was heated to 670°C in a reducing atmosphere at a rate of 1.5°C / min, kept at this temperature for 8 hours, cooled to room temperature, and discharged to obtain the regenerated lithium iron phosphate material;

[0068] The reducing atmosphere is formed by mixing nitrogen and hydrogen in a volume ratio of 9.5:1. Example 4

[0069] The difference between this embodiment and embodiment 1 is that an equal mass of sucrose solution with a mass fraction of 10% is used to replace the dopamine solution, and other conditions remain unchanged. Example 5

[0070] Compared with Example 1, this embodiment differs in that no anhydrous ethanol is added, and other conditions remain unchanged. Example 6

[0071] Compared with Example 1, this embodiment has the following differences:

[0072] The positive electrode active material and the mixed acid solution were mixed in a mass ratio of 1:8.5, and hydrogen peroxide with a mass ratio of 10% of the mixed acid solution was added. The mixture was heated at a temperature of 50°C and a stirring speed of 200 r / min for acid leaching reaction for 2 hours, and then filtered to collect the leachate.

[0073] The rest of the conditions remain unchanged. Example 7

[0074] Compared with Example 1, this embodiment has the following differences:

[0075] The positive electrode active material and the mixed acid solution were mixed in a mass ratio of 1:8.5, and hydrogen peroxide with a mass ratio of 10% of the mixed acid solution was added. The mixture was heated and acid-leached for 2 hours at a temperature of 80°C and a stirring speed of 150 r / min, and then filtered to collect the leachate.

[0076] The rest of the conditions remain unchanged.

[0077] Comparative Example 1

[0078] Compared with Example 1, this comparative example has the following differences:

[0079] No malic acid solution was added, only citric acid solution was added, and the other conditions remained unchanged.

[0080] Comparative Example 2

[0081] Compared with Example 1, this comparative example has the following differences:

[0082] No citric acid solution was added, only malic acid solution was added, and the other conditions remained unchanged.

[0083] The performance evaluation tests were conducted on the products obtained in the examples and comparative examples. The specific evaluation methods and test results are as follows:

[0084] The lithium iron phosphate positive electrode material, the binder PVDF, and the conductive agent acetylene black are mixed in a mass ratio of 90:5:5. Specifically, the binder PVDF and the solvent NMP are first mixed and stirred to obtain a glue solution, and then the acetylene black and the positive electrode material are added. After stirring evenly, the glue solution is coated on the surface of the aluminum foil. The coated positive electrode sheet is dried and cut. The compaction density on the surface of the aluminum foil is controlled to be 2.75g / cm 3 , thickness is 80μm;

[0085] Assemble the positive electrode shell, positive electrode sheet, electrolyte, diaphragm, electrolyte, lithium sheet, gasket, spring, and negative electrode shell in the order of CR2032 button battery in a vacuum glove box, and finally press it with a sealing machine, let it stand for 24 hours, and test its electrochemical performance;

[0086] 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.

[0087] The assembled buckle battery was subjected to cross-current charge and discharge using a Blue Power test system (CT2001A) with a voltage window of 2.4-4.6V at a constant temperature of 25°C. The test results showed a capacity retention rate of 1 after 200 cycles at 0.2C, and a capacity retention rate of 2 after 200 cycles at 0.6C. The detailed test results are shown in Table 1.

[0088] Table 1: Product performance test results

[0089]

[0090] The test results in Table 1 show that the product obtained by the present invention has excellent cycle performance, and as the charge rate increases, the cycle performance of the product decreases relatively insignificantly.

[0091] 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 considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for recycling and regenerating lithium iron phosphate battery materials using liquid phase, characterized in that: The specific method includes the following steps: Disassemble the lithium iron phosphate battery and recycle the positive electrode; The surface active material layer of the positive electrode sheet is peeled off to obtain the positive electrode active material layer, which is then mixed with NMP at a mass ratio of 1:(8-10), subjected to microwave ultrasonic heating reaction, and then filtered, washed and dried to obtain the positive electrode active material; The positive electrode active material and the mixed acid solution are mixed in a mass ratio of 1: (8.5-9.0), and hydrogen peroxide with a mass ratio of 10-12% of the mixed acid solution is added. After heating and acid leaching at a temperature of 50-90 ° C for 2-3 hours, the leachate is filtered and collected; The mixed acid solution is prepared by mixing a malic acid solution having a concentration of 1.8-2.2 mol / L and a citric acid solution having a concentration of 1.5-2.0 mol / L in a mass ratio of 1:

1. The leachate was adjusted to pH 3.5, filtered, and the precipitate was removed. A lithium source was then added to adjust the molar ratio of Li:Fe:P to 1.05:1:1, and the pH was adjusted to 9.

0. The reaction was carried out at a temperature of 50-60°C, and then the temperature was raised to 80°C. After aging for 4 hours, the precursor was filtered and dried to obtain a dry precursor. The dried precursor is calcined in a reducing atmosphere at a temperature of 650-670° C. for 6-8 hours, cooled, and discharged to obtain the regenerated lithium iron phosphate material.

2. The method for recycling and regenerating lithium iron phosphate battery materials using liquid phase according to claim 1, characterized in that: The microwave ultrasonic heating reaction comprises: The microwave-ultrasonic reaction was carried out for 2-2.5 hours under the conditions of microwave power of 300-320 W and ultrasonic frequency of 80-100 kHz.

3. The method for recycling and regenerating lithium iron phosphate battery materials using liquid phase according to claim 1, characterized in that: The specific method also includes: Anhydrous ethanol of an equal volume to the leachate is added to the leachate, and then the pH is adjusted to 3.5, filtered, and the precipitate is removed. Then, a lithium source is supplemented, and the molar ratio of Li:Fe:P is adjusted to 1.05:1:

1. The pH is then adjusted to 9.

0. After reacting at a temperature of 50-60°C, the temperature is raised to 80°C, and after aging for 4 hours, the mixture is transferred to a high-pressure reactor and reacted at a temperature of 180-190°C for 8-10 hours. The mixture is then cooled, discharged, filtered, and dried to obtain a dry precursor.

4. A method for recycling and regenerating lithium iron phosphate battery materials using liquid phase according to any one of claims 1-2, characterized in that: The specific method also includes: An equal volume of anhydrous ethanol is added to the leachate, and then the pH is adjusted to 3.

5. The mixture is filtered to remove the precipitate, and then a lithium source is added to adjust the molar ratio of Li:Fe:P to 1.05:1:

1. The pH is then adjusted to 9.

0. After reacting at a temperature of 50-60°C, a dopamine solution of 6-8% by weight of the leachate is added. The mixture is then heated to 80°C, allowed to stand for aging for 4 hours, and then transferred to a high-pressure reactor. After high-temperature reaction at a temperature of 180-190°C for 8-10 hours, the mixture is cooled, discharged, filtered, and dried to obtain a dry precursor. Wherein, the concentration of the dopamine solution is 8-10 g / L.

5. A method for recycling and regenerating lithium iron phosphate battery materials using liquid phase according to any one of claims 1 to 3, characterized in that: The specific method also includes: The dried precursor is heated to 650-670°C in a reducing atmosphere at a rate of 0.8-1.5°C / min, kept warm and calcined for 6-8 hours, cooled to room temperature with the furnace, and discharged to obtain the regenerated lithium iron phosphate material.

6. The method for recycling and regenerating lithium iron phosphate battery materials using liquid phase according to claim 5, characterized in that: The reducing atmosphere is formed by mixing nitrogen and hydrogen in a volume ratio of (9-9.5):

1.

7. The method for recycling and regenerating lithium iron phosphate battery materials using liquid phase according to claim 1, characterized in that: The specific method also includes: The positive electrode active material and the mixed acid solution are mixed in a mass ratio of 1: (8.5-9.0), and hydrogen peroxide is added which is 10-12% of the mass of the mixed acid solution. The mixture is first heated and acid-leached for 1-1.5 hours at a temperature of 50-60°C and a stirring speed of 200-220 r / min, and then heated and acid-leached for 1-1.5 hours at a temperature of 80-90°C and a stirring speed of 150-180 r / min. The leachate is then filtered and collected.

8. The method for recycling and regenerating lithium iron phosphate battery materials using liquid phase according to claim 1, characterized in that: The mass fraction of the hydrogen peroxide is 28-32%.

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