Method for repairing and regenerating waste and old lithium iron phosphate positive electrode material

Abstract

The application discloses a kind of waste old lithium iron phosphate positive material's repair regeneration method, comprising the following steps: obtaining lithium iron phosphate waste powder, determine lithium ion missing amount in lithium iron phosphate waste powder;Lithium salt and thiourea are completely dissolved in solvent, obtain direct reduction repair agent solution;The lithium iron phosphate waste powder and direct reduction repair agent solution are mixed, and heating stirring until steaming dry, obtain mixture;After the mixture is sintered, it is cleaned, and the repaired lithium iron phosphate positive material is obtained.The application directly reduces the repair regeneration waste old lithium iron phosphate positive material by thiourea auxiliary solid phase sintering method, can directly repair structure and supplement lithium to lithium iron phosphate waste powder without damaging the structure of material itself, obtain recyclable battery-grade lithium iron phosphate positive material, and the method has great application prospect.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material recycling technology, specifically relating to a method for repairing and regenerating waste lithium iron phosphate cathode materials. Background Technology

[0002] With the development of electric vehicles, the installed capacity of power lithium-ion batteries is increasing year by year. However, lithium-ion power batteries have a limited lifespan, generally only 5-10 years, meaning that the number of retired lithium-ion power batteries in the future will be enormous. Effective recycling and regeneration of lithium-ion batteries to achieve a closed-loop development of the lithium battery industry chain is essential. The capacity decay of lithium-ion batteries mainly stems from the loss of components and structural deterioration of the cathode material, which cannot be directly recycled and reused. How to achieve high-value-added recycling of lithium-ion battery cathode materials is currently a hot topic.

[0003] Chinese patent application No. 2022101660291 discloses a modification method for the direct pyrometallurgical regeneration of lithium iron phosphate cathode material. The method involves medium-temperature impurity removal and activation, addition of lithium, iron, phosphorus, and carbon sources, followed by ball milling, spray drying, and sintering to obtain battery-grade lithium iron phosphate. However, this method has certain limitations. The calcination in air completely destroys the structure of the waste lithium iron phosphate, resulting in the loss of the inherent energy of lithium iron phosphate and the volatilization and waste of residual lithium.

[0004] Chinese patent application No. 2022115275336 discloses a method for the efficient recycling and reuse of waste lithium iron phosphate battery cathode materials. The method involves leaching the waste lithium iron phosphate battery cathode materials in a strong acid aqueous solution, filtering to obtain an acidic leachate, adjusting the pH of the acidic leachate to 3.0-3.75, initiating a precipitation reaction, filtering to remove aluminum impurities, and obtaining a dealuminized solution. The required raw materials are then replenished, and new lithium iron phosphate cathode materials are synthesized via a hydrothermal method. This type of method requires the use of large amounts of acid and alkali, which can easily cause secondary pollution; furthermore, the hydrothermal method used for the resynthesis of lithium iron phosphate is not suitable for large-scale industrial production.

[0005] Given that existing lithium iron phosphate recycling and regeneration technologies cannot meet the needs of enterprises to obtain higher economic benefits, there is an urgent need to develop a process for the large-scale recycling and regeneration of waste lithium iron phosphate. This process should meet the requirements of maximizing the original value of waste lithium iron phosphate powder, simple process steps, no secondary pollution, low cost, and suitability for large-scale production, so as to promote the large-scale recycling of retired lithium-ion batteries and realize the closed-loop production development of the industry. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a method for repairing and regenerating waste lithium iron phosphate cathode materials. This method does not require secondary processing of the lithium iron phosphate cathode materials separated from retired power lithium-ion batteries. It can directly repair the structure of waste lithium iron phosphate powder and replenish lithium without damaging the material's original structure, thereby obtaining recyclable battery-grade lithium iron phosphate cathode materials. Furthermore, this method has the advantages of simple process, ease of large-scale production, and low cost.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a method for repairing and regenerating waste lithium iron phosphate cathode materials, comprising the following steps:

[0009] Lithium iron phosphate waste powder was obtained, and the amount of lithium ion deficiency in the lithium iron phosphate waste powder was tested.

[0010] Lithium salt and thiourea were completely dissolved in a solvent to obtain a direct reduction and repair agent solution;

[0011] The waste lithium iron phosphate powder and the direct reduction remediation agent solution are mixed and heated and stirred until evaporated to dryness to obtain a mixture;

[0012] The mixture is sintered and then cleaned to obtain the repaired lithium iron phosphate cathode material.

[0013] This invention uses lithium salt and thiourea to directly obtain a reducing agent solution, which is low-cost. Simultaneously, it employs a dissolution-evaporation method to mix with lithium iron phosphate waste powder, ensuring a uniform coating of the reducing agent on its surface. Compared to the LiFePO4 phase in the waste powder particles, the amine groups in thiourea preferentially bind to the Fe in the irreversible FePO4 phase. 3+ The interaction between the two materials enables precise and targeted repair and regeneration. The addition of thiourea helps to create a suitable repair and reduction environment for lithium iron phosphate waste powder in large-scale industrial production. Furthermore, the present invention uses dissolution and evaporation instead of mixing and grinding, which facilitates the uniform distribution of the direct reduction and repair agent on the surface of the lithium iron phosphate waste powder particles. The evaporated water can be recovered and reused, reducing costs. In addition, the use of solid-state sintering for direct regeneration eliminates the need for secondary treatment of the lithium iron phosphate waste powder, maximizing the utilization of its original energy value. The entire method is simple, requires no large amounts of acid and alkali chemical reagents, and has great application potential.

[0014] The lithium iron phosphate waste powder mentioned in this article refers to the lithium iron phosphate waste powder obtained from the dismantling and separation of retired power lithium-ion batteries with different capacities, health, and state of performance (SOH), or from the lithium iron phosphate cathode waste and scrap generated during the production process of power lithium-ion batteries.

[0015] In some specific embodiments of the present invention, the lithium iron phosphate waste powder is obtained by dismantling and separating it from retired power lithium-ion batteries. In some specific embodiments of the present invention, the dismantling and separation steps are as follows: lithium iron phosphate positive electrode sheets are obtained by dismantling and separating them from retired power lithium-ion batteries; the lithium iron phosphate positive electrode sheets are cleaned with a cleaning agent, and then the positive electrode current collector and positive electrode material are separated from the whole sheet using deionized water at 80℃-95℃. The cleaning agent removes residual electrolyte from the positive electrode sheet. The cleaning agent can be dimethyl carbonate (DMC), acetone, or N-methylpyrrolidone (NMP), but is not limited to these; any conventional electrolyte cleaning solvent in the art is acceptable. Furthermore, in the dismantling process of retired power lithium-ion batteries, this paper adopts the 80℃-95℃ hot deionized water immersion method to peel the waste lithium iron phosphate cathode material from the cathode current collector in one piece. This reduces the generation of impurities (such as aluminum impurities) during crushing and screening, eliminates the step of removing impurities, simplifies the process, reduces costs, and facilitates the complete recovery of metal elements in the cathode current collector.

[0016] In a further embodiment, the amount of lithium ion missing in the lithium iron phosphate waste powder mentioned in this paper can be tested using methods known in the art, such as inductively coupled plasma mass spectrometry (ICP-MS). Specifically, the lithium iron phosphate waste powder is dissolved in aqua regia to remove insoluble impurities, and then the concentration of each element in the filtrate is tested. The molar amount of lithium ion missing in the lithium iron phosphate waste powder is determined based on the stoichiometric coefficients, which is denoted as x in this paper. Alternatively, the amount of lithium ion missing can be determined through simulation based on the state of health (SOH) of the batch of power batteries.

[0017] In a further embodiment, the lithium salt described herein is lithium hydroxide monohydrate or lithium acetate dihydrate. The solvent used is at least one of deionized water and anhydrous ethanol; preferably, the solvent is a mixture of deionized water and anhydrous ethanol.

[0018] In a further proposal, the amount of lithium salt added in this paper should be determined based on the amount of lithium ion missing, x (moles).

[0019] In a further step, the amount of thiourea added in this study needs to be controlled. Too little thiourea will not have a significant repair effect, while too much will reduce the specific capacity due to the pyrolysis products of thiourea and increase costs. Therefore, in this study, the mass ratio of thiourea to lithium iron phosphate waste powder is (0.8–1.2):10, preferably (0.9–1.1):10; more preferably, the mass ratio is 1:10.

[0020] In a further embodiment, the heating and stirring temperature and stirring speed can be adjusted as needed. In some specific embodiments of the present invention, the heating temperature is 80℃-100℃; and / or the stirring speed is 300rpm-500rpm.

[0021] In a further embodiment, the solid-state sintering temperature and heating rate can be adjusted as needed. In some specific embodiments of the present invention, the sintering temperature is 750℃-850℃, the sintering time is 6h-8h; and / or, the sintering heating rate is 3℃ / min-5℃ / min.

[0022] In a further embodiment, the post-sintering cleaning process described in this paper can adopt conventional processes in the field, specifically, it can be cleaning with deionized water and anhydrous ethanol alternately until the cleaning solution is neutral.

[0023] The beneficial effects of this invention are:

[0024] The regeneration method for waste lithium iron phosphate cathode materials in this invention involves direct reduction and regeneration of the waste lithium iron phosphate cathode materials through thiourea-assisted solid-state sintering. Compared with other recycling methods, this method uses lithium salt and thiourea to directly obtain a reducing agent solution, resulting in lower costs. Simultaneously, a dissolution-drying method is employed to mix the material with the waste lithium iron phosphate powder, ensuring a uniform coating of the reducing agent on its surface. Compared to the LiFePO4 phase in the waste powder particles, the amine groups in thiourea preferentially bind to the Fe in the irreversible FePO4 phase. 3+ The interaction between the components enables precise and targeted repair and regeneration. Furthermore, this invention uses a solid-state sintering method for direct regeneration, eliminating the need for secondary treatment of lithium iron phosphate waste powder. This maximizes the utilization of the original energy value of the waste powder. The entire method is simple, requiring minimal use of acid and alkali chemical reagents, making it suitable for large-scale commercial recycling and regeneration production. It can realize a closed-loop production development for the lithium-ion battery industry and has broad application prospects. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the direct repair, regeneration, and recycling of waste lithium iron phosphate cathode materials in a preferred embodiment of the present invention.

[0026] Figure 2 The XRD patterns of waste lithium iron phosphate and repaired lithium iron phosphate in Example 1 are compared.

[0027] Figure 3 Comparison of HAADF-STEM images of waste lithium iron phosphate and repaired lithium iron phosphate in Example 1.

[0028] Figure 4 Comparison of SEM images of waste lithium iron phosphate and lithium iron phosphate after repair in Examples 1 and Comparative Examples 1-3.

[0029] Figure 5 Electrochemical performance graphs of waste lithium iron phosphate and lithium iron phosphate after repair in Examples 1 and Comparative Examples 1-3. Detailed Implementation

[0030] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, unless otherwise specified, methods not specifically describing conditions or steps are conventional methods, and the reagents and materials used are commercially available.

[0032] Example 1

[0033] This embodiment discloses a method for repairing and regenerating waste lithium iron phosphate cathode materials. For the specific process flow, please refer to [reference needed]. Figure 1 The specific steps are as follows:

[0034] S1. Lithium iron phosphate cathode sheets are obtained by disassembling and separating from retired lithium-ion power batteries. After cleaning the obtained lithium iron phosphate cathode sheets with dimethyl carbonate (DMC), they are soaked in deionized water at 90°C and the cathode material and aluminum foil are peeled off from the whole sheet.

[0035] S2. The Li / P and Li / Fe ratios of the cathode material stripped in step S1 were tested using ICP-MS technology. The results were approximately 4:5, indicating that the lithium ion deficiency was about 20% (molar percentage).

[0036] S3. Add the lithium iron phosphate waste powder with a lithium ion deficiency of 20% (molar percentage) from step S2 to the direct reduction repair agent solution, heat to 90°C and stir at 400 rpm until completely evaporated, then grind to obtain a mixture; wherein, the direct reduction repair agent solution is prepared by dissolving thiourea and lithium hydroxide monohydrate in a mixed solvent of deionized water and ethanol, the molar ratio of lithium iron phosphate waste powder to lithium hydroxide monohydrate is 4:1, the mass ratio of lithium iron phosphate waste powder to thiourea is 10:1, and the amount of deionized water and ethanol mixed solvent corresponding to 0.2g of lithium iron phosphate waste powder is 10ml (5ml each).

[0037] S4. Place the ground mixture from step S3 into a tube furnace and sinter it at 800°C for 6 hours in a mixed atmosphere of hydrogen and argon. After cooling the sintered material, wash it alternately with deionized water and anhydrous ethanol until the washing solution is neutral to obtain the repaired lithium iron phosphate material.

[0038] Example 2

[0039] This embodiment discloses a method for repairing and regenerating waste lithium iron phosphate cathode materials, the specific steps of which are as follows:

[0040] S1, Same as Example 1.

[0041] S2, same as Example 1.

[0042] S3. Add the lithium iron phosphate waste powder with a lithium ion deficiency of 20% (molar percentage) from step S2 to the direct reduction repair agent solution, heat to 90°C and stir at 400 rpm until completely evaporated, then grind to obtain a mixture; wherein, the direct reduction repair agent solution is prepared by dissolving thiourea and lithium acetate dihydrate in a mixed solvent of deionized water and ethanol, the molar ratio of lithium iron phosphate waste powder to lithium acetate dihydrate is 4:1, the mass ratio of lithium iron phosphate waste powder to thiourea is 10:1, and the amount of deionized water and ethanol mixed solvent corresponding to 0.2g of lithium iron phosphate waste powder is 10ml (5ml each).

[0043] S4, Same as Example 1.

[0044] Example 3

[0045] This embodiment discloses a method for repairing and regenerating waste lithium iron phosphate cathode materials, which adopts the same implementation method as in Embodiment 1, except that: ① In step S3, the molar ratio of waste lithium iron phosphate powder to lithium hydroxide monohydrate in the direct reduction repair agent solution is 4:1, and the mass ratio of waste lithium iron phosphate powder to thiourea is 10:0.8; ② In step S3, the heating and stirring temperature is 80℃ and the rotation speed is 300rpm; ③ In step S4, the sintering temperature is 750℃ and the time is 7h.

[0046] Example 4

[0047] This embodiment discloses a method for repairing and regenerating waste lithium iron phosphate cathode material, which adopts the same implementation method as in embodiment 3, except that: in step S3, the molar ratio of waste lithium iron phosphate powder to lithium hydroxide monohydrate in the direct reduction repair agent solution is 4:1, and the mass ratio of waste lithium iron phosphate powder to thiourea is 10:0.9.

[0048] Example 5

[0049] This embodiment discloses a method for repairing and regenerating waste lithium iron phosphate cathode materials, which adopts the same implementation method as in Embodiment 1, except that: ① In step S3, the molar ratio of waste lithium iron phosphate powder to lithium hydroxide monohydrate in the direct reduction repair agent solution is 4:1, and the mass ratio of waste lithium iron phosphate powder to thiourea is 10:1.1; ② In step S3, the heating and stirring temperature is 85℃ and the rotation speed is 500rpm; ③ In step S4, the sintering temperature is 850℃ and the time is 8h.

[0050] Example 6

[0051] This embodiment discloses a method for repairing and regenerating waste lithium iron phosphate cathode materials, which adopts the same implementation method as in embodiment 5, except that: in step S3, the molar ratio of waste lithium iron phosphate powder to lithium hydroxide monohydrate in the direct reduction repair agent solution is 4:1, and the mass ratio of waste lithium iron phosphate powder to thiourea is 10:1.2.

[0052] Comparative Example 1

[0053] This comparative example discloses a method for repairing and regenerating waste lithium iron phosphate cathode material, which adopts the same implementation method as Example 1, except that in step S3, a lithium replenishment repair solution without thiourea is used instead of a direct repair reducing agent solution. The specific steps are as follows:

[0054] S1, Same as Example 1.

[0055] S2, same as Example 1.

[0056] S3. Add the lithium iron phosphate waste powder with a lithium ion deficiency of 20% (molar percentage) from step S2 to the lithium replenishment and repair solution, heat to 90°C and stir at 400 rpm until completely evaporated, then grind to obtain a mixture; wherein, the lithium replenishment and repair solution is prepared by dissolving lithium hydroxide monohydrate in a mixed solvent of deionized water and ethanol, the molar ratio of lithium iron phosphate waste powder to lithium hydroxide monohydrate is 4:1, and the amount of deionized water and ethanol mixed solvent corresponding to 0.2g of lithium iron phosphate waste powder is 10ml (5ml each).

[0057] S4, Same as Example 1.

[0058] Comparative Example 2

[0059] This comparative example discloses a method for repairing and regenerating waste lithium iron phosphate cathode material, which adopts the same implementation method as Example 1, except that in step S3, the molar ratio of waste lithium iron phosphate powder to lithium hydroxide monohydrate in the direct reduction repair agent solution is 4:1, and the mass ratio of waste lithium iron phosphate powder to thiourea is 10:2. The specific steps are as follows:

[0060] S1, Same as Example 1.

[0061] S2, same as Example 1.

[0062] S3. Add the lithium iron phosphate waste powder with a lithium ion deficiency of 20% (molar percentage) from step S2 to the direct reduction repair agent solution, heat to 90°C and stir at 400 rpm until completely evaporated, then grind to obtain a mixture; wherein, the direct reduction repair agent solution is prepared by dissolving thiourea and lithium hydroxide monohydrate in a mixed solvent of deionized water and ethanol, the molar ratio of lithium iron phosphate waste powder to lithium hydroxide monohydrate is 4:1, the mass ratio of lithium iron phosphate waste powder to thiourea is 10:2, and the amount of deionized water and ethanol mixed solvent corresponding to 0.2g of lithium iron phosphate waste powder is 10ml (5ml each).

[0063] S4, Same as Example 1.

[0064] Comparative Example 3

[0065] This comparative example discloses a method for repairing and regenerating waste lithium iron phosphate cathode material, which adopts the same implementation method as Example 1, except that in step S3, the molar ratio of waste lithium iron phosphate powder to lithium hydroxide monohydrate in the direct reduction repair agent solution is 4:1, and the mass ratio of waste lithium iron phosphate powder to thiourea is 10:5. The specific steps are as follows:

[0066] S1, Same as Example 1.

[0067] S2, same as Example 1.

[0068] S3. Add the lithium iron phosphate waste powder with a lithium ion deficiency of 20% (molar percentage) from step S2 to the direct reduction repair agent solution, heat to 90°C and stir at 400 rpm until completely evaporated, then grind to obtain a mixture; wherein, the direct reduction repair agent solution is prepared by dissolving thiourea and lithium hydroxide monohydrate in a mixed solvent of deionized water and ethanol, the molar ratio of lithium iron phosphate waste powder to lithium hydroxide monohydrate is 4:1, the mass ratio of lithium iron phosphate waste powder to thiourea is 10:5, and the amount of deionized water and ethanol mixed solvent corresponding to 0.2g of lithium iron phosphate waste powder is 10ml (5ml each).

[0069] S4, Same as Example 1.

[0070] Performance testing

[0071] 1. Material Characterization

[0072] Figure 2The image shows a comparison of the XRD patterns of the disassembled waste lithium iron phosphate and the repaired lithium iron phosphate in Example 1. It can be seen that the waste lithium iron phosphate powder has a lack of active lithium and some ferrous iron is oxidized, resulting in the formation of the FePO4 phase; while after thiourea-assisted high-temperature solid-state sintering repair, it has been regenerated into the LiFePO4 phase.

[0073] Figure 3 The high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) images of waste lithium iron phosphate and repaired lithium iron phosphate from Example 1 are shown for comparison. It can be seen that the waste lithium iron phosphate powder particles have obvious microcracks and appear broken, while the repaired lithium iron phosphate particles do not show microcracks and are more rounded.

[0074] Figure 4 The SEM images of waste lithium iron phosphate and the reconstituted lithium iron phosphate from Examples 1 and Comparative Examples 1-3 are shown for comparison. It can be seen that in Comparative Example 1 without thiourea, the high-temperature solid-state sintering process caused severe agglomeration. However, in Example 1 with thiourea, the high-temperature solid-state sintering did not significantly change the morphology and size of the particles, with particle sizes distributed between 0.3-1 μm. This is because the pyrolysis products of thiourea can inhibit the agglomeration of lithium iron phosphate particles during the high-temperature solid-state sintering process. In Example 1, a small amount of thiourea was sufficient to inhibit agglomeration; further increasing the amount of thiourea in Comparative Examples 2 and 3 did not have much effect.

[0075] 2. Electrochemical performance

[0076] Figure 5 Electrochemical performance graphs of waste lithium iron phosphate and the remediated lithium iron phosphate of Example 1 and Comparative Examples 1-3 are shown. It can be seen that compared to waste lithium iron phosphate, the specific capacity of the remediated lithium iron phosphate in Example 1 is significantly improved at different current densities. In contrast, the capacity recovery of the lithium iron phosphate in Comparative Example 1 without thiourea is not significant. This is because the direct reduction remediation agent with thiourea uniformly covers the surface of the waste lithium iron phosphate particles. Compared to the LiFePO4 phase in the particles, the amine groups in thiourea preferentially bind to the Fe in the irreversible FePO4 phase. 3+ The interaction helps to precisely locate the structural damage. Then, thiourea undergoes pyrolysis at high temperatures, releasing reducing gases such as ammonia (NH3) and hydrogen sulfide (H2S), which are beneficial for Fe. 3+The reduction and irreversible phase restoration create an optimal repair and reduction environment. Simultaneously, the pyrolysis products of thiourea effectively inhibit the aggregation of LiFePO4 particles at high temperatures. In Example 1, a small amount of thiourea in the direct reduction repair agent can assist high-temperature sintering, thereby restoring the electrochemical performance of waste lithium iron phosphate. In Comparative Examples 2 and 3, further increasing the amount of thiourea actually led to a deterioration in electrochemical performance. This is because excessive addition of thiourea causes its pyrolysis products to reduce the energy density of the system.

[0077] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for repairing and regenerating waste lithium iron phosphate cathode materials, characterized in that, Includes the following steps: Lithium iron phosphate waste powder was obtained, and the amount of lithium ion deficiency in the lithium iron phosphate waste powder was tested. Lithium salt and thiourea were completely dissolved in a solvent to obtain a direct reduction and repair agent solution; The waste lithium iron phosphate powder and the direct reduction remediation agent solution are mixed and heated and stirred until evaporated to dryness to obtain a mixture; The mixture is sintered and then cleaned to obtain the repaired lithium iron phosphate cathode material.

2. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 1, characterized in that, The lithium iron phosphate waste powder is obtained by dismantling and separating retired power lithium-ion batteries, or by stripping it from waste lithium iron phosphate cathode sheets and scraps generated during the production of power lithium-ion batteries.

3. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 2, characterized in that, The disassembly and separation steps are as follows: disassemble and separate lithium iron phosphate positive electrode sheets from retired power lithium-ion batteries; clean the lithium iron phosphate positive electrode sheets with a cleaning agent, and then use deionized water at 80℃-95℃ to separate the positive electrode current collector and positive electrode material in one piece.

4. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 3, characterized in that, The cleaning agent is dimethyl carbonate, acetone, or N-methylpyrrolidone.

5. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 1, characterized in that, The amount of lithium ion missing in the lithium iron phosphate waste powder was obtained by inductively coupled plasma mass spectrometry; or, it was determined by simulation based on the performance status of the batch of power batteries.

6. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 1, characterized in that, The lithium salt is lithium hydroxide monohydrate or lithium acetate dihydrate.

7. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 1, characterized in that, The solvent is at least one of deionized water and anhydrous ethanol.

8. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 1, characterized in that, The amount of lithium salt added is determined based on the amount of lithium ion deficiency.

9. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 1, characterized in that, The mass ratio of thiourea to lithium iron phosphate waste powder is (0.8-1.2):

10.

10. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 9, characterized in that, The mass ratio of thiourea to lithium iron phosphate waste powder is (0.9-1.1):

10.

11. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 9, characterized in that, The mass ratio of thiourea to lithium iron phosphate waste powder is 1:

10.

12. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 1, characterized in that, The heating temperature is 80℃-100℃; and / or the stirring speed is 300rpm-500rpm.

13. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 1, characterized in that, The sintering temperature is 750℃-850℃, and the sintering time is 6h-8h; and / or the sintering heating rate is 3℃ / min-5℃ / min.

14. The method for repairing and regenerating waste lithium iron phosphate cathode materials as described in claim 1, characterized in that, The cleaning process involves alternating between deionized water and anhydrous ethanol until the cleaning solution becomes neutral.

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