A method for regenerating waste lithium iron phosphate cathode materials and corresponding products

Abstract

This invention belongs to the field of recycled materials technology and discloses a method for regenerating waste lithium iron phosphate cathode materials and corresponding products. The method includes: soaking waste cathode sheets to separate the waste cathode material from aluminum foil, drying and grinding to obtain waste cathode material powder; adding the waste cathode material powder, gallic acid, and lithium acetate to deionized water, mixing evenly, heating, centrifuging, and drying to obtain intermediate product powder; and calcining the intermediate product powder to obtain regenerated lithium iron phosphate cathode material. During the regeneration process, gallic acid acts as a reducing agent and carbon source precursor, while lithium acetate acts as a lithium source. This process simultaneously repairs the lattice and surface degradation while repairing the carbon layer to build a conductive network, thus improving the electrochemical performance of the regenerated material. This invention features a simple process and low cost, solving the current problem of requiring stepwise addition of reducing agents and carbon sources and the difficulty in removing surface interface contamination, achieving efficient, low-cost, and green regeneration of waste lithium iron phosphate.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium iron phosphate battery recycling and regeneration technology, specifically relating to a method for regenerating the positive electrode material of waste lithium iron phosphate batteries and corresponding products. Background Technology

[0002] Lithium iron phosphate (LFP), as a cathode material for lithium-ion batteries, is widely used in new energy vehicles and energy storage due to its advantages such as low cost, high safety, and long cycle life. As early power batteries gradually reach their peak retirement age, the efficient disposal of spent LFP materials has become an urgent problem to solve. Current recycling methods for spent cathode materials mainly include three categories: pyrometallurgical, hydrometallurgical, and direct regeneration. Compared to traditional processes that are complex and uneconomical, direct regeneration technology, with its short process, low energy consumption, and high added value, has become the most promising recycling route.

[0003] Hydrothermal regeneration has attracted much attention due to its mild and controllable reaction conditions, simple operation, and controllable product morphology, enabling one-step material repair. However, while existing hydrothermal regeneration methods can replenish lithium, they rarely address surface degradation caused by interfacial side reactions. Furthermore, subsequent annealing often requires the addition of an extra carbon source to construct a conductive network, increasing process complexity and material costs. Therefore, exploring multi-functional additives that combine interfacial purification and conductive network reconstruction to achieve integrated and simultaneous repair of failed materials while simplifying the process has become a key research direction for improving the economics and practicality of hydrothermal regeneration technology. Summary of the Invention

[0004] Based on the aforementioned technical problems in the existing technology, the present invention provides a method for regenerating waste lithium iron phosphate using gallic acid. This method uses gallic acid as a multifunctional reducing agent, chelating agent, and carbon source. Through hydrothermal-short annealing synergistic treatment, lattice repair, interface impurity removal, and in-situ reconstruction of the conductive network are achieved, thereby comprehensively improving the lattice integrity, interface cleanliness, and electronic conductivity of the regenerated lithium iron phosphate, resulting in excellent electrochemical performance.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for regenerating waste lithium iron phosphate cathode materials, comprising the following steps: Step S1: Soak the waste positive electrode sheet in deionized water to separate the waste positive electrode material from the aluminum foil, and dry and grind the waste positive electrode material to obtain waste positive electrode material powder. Step S2: Add waste cathode material powder, gallic acid and lithium acetate to deionized water, mix evenly, place in a reaction vessel and heat, centrifuge the product after the reaction is completed, and then dry to obtain intermediate product powder. Step S3: The intermediate product powder is calcined under an inert atmosphere to obtain regenerated lithium iron phosphate cathode material.

[0006] Preferably, in step S1, the drying temperature is 60-80°C and the drying time is 12-24 hours.

[0007] Preferably, in step S2, the amounts of waste cathode material powder, gallic acid, and lithium acetate added are 0.3g, 0.3-0.45g, and 0.4g, respectively, and 50mL of deionized water is added to make the concentration of cathode material in the mixture 6g / L, ensuring that the cathode material can react fully. Gallic acid, as a multifunctional reducing agent, chelating agent, and carbon source, efficiently reduces Fe(III) to Fe(II) in a hydrothermal environment, repairing lattice defects in the material. Simultaneously, its chelating properties selectively remove amorphous Fe(III) compounds from the particle surface, purifying the interface, and its residues can participate in carbon layer construction during subsequent annealing. The gallic acid used in this invention is widely available, environmentally friendly, and possesses both reducing and chelating functions. Lithium acetate, as a lithium source, aims to replenish lithium elements lost during cycling, repair lithium vacancies, and restore the reversible capacity of the material; the lithium acetate used in this invention has high solubility and reactivity.

[0008] Preferably, in step S2, the reactor is a reactor with a polytetrafluoroethylene liner.

[0009] Preferably, in step S2, the heating temperature is 160–200°C, and the heating time is 6–10 hours. The selection of process parameters is crucial for the regeneration of waste cathode materials. Appropriate temperature ensures that gallic acid fully exerts its reducing and chelating activity, achieving efficient Fe(III) conversion and effective removal of interfacial impurities; sufficient reaction time guarantees the full diffusion of lithium ions into the crystal lattice, contributing to the uniform repair of the material structure. If the temperature is too low or the time is too short, insufficient reduction and incomplete interfacial purification may occur; if the temperature is too high or the time is too long, excessive decomposition of gallic acid or abnormal grain growth may occur, which is detrimental to the electrochemical performance of the regenerated material.

[0010] Preferably, in step S2, the material is washed 2-4 times by centrifugation with deionized water and anhydrous ethanol, respectively, at a speed of 8000 rpm for 6-10 minutes per centrifugation. Centrifugation is used to thoroughly separate the reaction products from the residual solvent, ensuring the cleanliness of the regenerated material surface. The speed and time parameters can be adjusted according to the separation of the reaction product solids.

[0011] Preferably, in step S2, the drying temperature is 60–80°C, and the drying time is 12–24 hours. The drying temperature and time are adjusted according to the evaporation of the solvent to ensure that residual solvent is completely removed.

[0012] Preferably, in step S3, the temperature is increased to 600-750°C at a heating rate of 2-10°C, and held for 2-5 hours. Annealing treatment allows residual gallic acid and its derivatives to undergo in-situ pyrolysis on the material surface, forming a uniform carbon layer, repairing the damaged conductive network, and promoting further ordering of the crystal structure, thereby improving the electronic conductivity and electrochemical performance of the recycled material. Appropriate temperature and time ensure sufficient carbonization of gallic acid to form a uniform conductive carbon layer while avoiding abnormal grain growth or overheating of the material; a suitable heating rate helps control the carbonization process, preventing carbon layer breakage or agglomeration, thus constructing a complete and continuous conductive network on the material surface, improving the rate performance and cycle stability of the recycled lithium iron phosphate.

[0013] Preferably, in step S3, the inert atmosphere is high-purity argon or high-purity nitrogen. Choosing an inert atmosphere during the annealing process is to avoid oxidation side reactions in the lithium iron phosphate material at high temperatures, ensuring the phase purity of the recycled material.

[0014] Preferably, the method further includes step S0: discharging and disassembling the waste lithium iron phosphate battery to obtain waste positive electrode sheets; the specific operation is: manually disassembling and removing the stacked sheets, and then sorting the positive electrode sheets from the separator and negative electrode sheets.

[0015] The second aspect of the present invention provides a regenerated lithium iron phosphate cathode material prepared by the first aspect of the present invention.

[0016] The role and effect of invention The above-mentioned technical solution of the present invention has the following technical effects: This invention uses gallic acid as a multifunctional reducing agent, chelating agent and carbon source to simultaneously achieve Fe(III) reduction, interface impurity removal and in-situ reconstruction of conductive network in hydrothermal-short annealing synergistic treatment. No additional carbon source is required, which significantly simplifies the process and reduces material costs.

[0017] This invention selectively removes amorphous Fe(III) compounds from the surface of waste cathode material particles through the chelating effect of gallic acid, thus purifying the lithium-ion diffusion interface. Combined with the uniform carbon layer formed in situ during annealing, it effectively repairs the damaged conductive network, thereby synergistically improving the lattice integrity, interface cleanliness, and electronic conductivity of the regenerated lithium iron phosphate.

[0018] This invention uses gallic acid, a widely available and environmentally friendly natural polyphenol compound, to replace traditional chemical reducing agents. This avoids the poor thermal stability and transportation and storage risks associated with reagents such as H2O2, reduces the environmental impact of the regeneration process, and achieves high-value utilization of spent materials through a short-process regeneration, thus demonstrating promising prospects for industrial application. Attached Figure Description

[0019] Figure 1The X-ray diffraction patterns are of the recycled lithium iron phosphate material of Example 1 and the waste lithium iron phosphate material of Comparative Example 1. Figure 2 The X-ray diffraction patterns of the regenerated lithium iron phosphate obtained in Examples 1-4 of this invention are shown below. Figure 3 These are scanning electron microscope (SEM) images of the regenerated lithium iron phosphate materials obtained in Examples 1-4 of this invention. Figure 4 The graph shows the cycle performance of the regenerated lithium iron phosphate batteries obtained in Examples 1-4 of this invention at a 1C rate. Figure 5 The first charge-discharge curves of the regenerated lithium iron phosphate batteries obtained in Examples 1-4 of this invention at a rate of 0.2C are shown. Figure 6 The images are scanning electron microscope (SEM) images of the waste lithium iron phosphate material of Comparative Example 1 and the recycled lithium iron phosphate materials obtained in Comparative Examples 2-3 of this invention. Figure 7 The graph shows the cycle performance of the waste lithium iron phosphate battery of Comparative Example 1 and the regenerated lithium iron phosphate batteries obtained from Comparative Examples 2-3 at a 1C rate. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, a method for regenerating waste lithium iron phosphate battery cathode materials will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of protection of this invention, which is defined by the appended claims.

[0021] 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. The terminology used in the specification herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention.

[0022] In the following embodiments, unless otherwise specified, the raw materials and reagents used can be obtained through conventional commercial channels, and the equipment and apparatus used are all conventional equipment known in the art or commercially available. Structures, materials, and operating procedures known in the art will not be described further here to avoid obscuring the inventive point of this invention.

[0023] The source information of the raw materials, materials, and instruments involved in the following embodiments or comparative examples is as follows: The waste lithium iron phosphate batteries used in this invention were purchased from the Shanghai SEG Electronic Recycling Market. Unless otherwise specified, all reagents used were of analytical grade, and all experimental water was double-distilled water. The main experimental materials are shown in Table 1. The electrolyte was a LiPF6 electrolyte with EC / DEC / DMC ratio of 1:1:1.

[0024] Table 1 Main experimental materials

[0025] The main experimental equipment and characterization instruments used in this invention are shown in Table 2.

[0026] Table 2 Main experimental equipment and characterization instruments

[0027] <Example 1> A method for regenerating cathode materials from spent lithium iron phosphate batteries specifically includes the following steps: Step S0: Discharge and disassemble the waste lithium iron phosphate batteries to obtain waste positive electrode sheets; Step S1: Soak the waste positive electrode sheet obtained in step S0 in deionized water to separate the waste positive electrode material from the aluminum foil. Finally, dry the collected waste positive electrode material at 80°C for 12 hours. After drying, grind it to obtain waste positive electrode material powder. Step S2: Add 0.3g of waste cathode material powder, 0.4g of gallic acid and 0.4g of lithium acetate obtained in step S1 to 50mL of deionized water, stir for 30min, and then place in a 100mL polytetrafluoroethylene-lined reactor. Heat at 180℃ for 6h. After the reaction is completed, cool to room temperature, and wash the reactants three times with deionized water and anhydrous ethanol by centrifugation. Finally, dry the solid reactants at 80℃ for 12h to obtain intermediate product powder. Step S3: The intermediate product powder obtained in step S2 is placed in an Ar atmosphere and heated to 600°C at a rate of 5°C, and held for 5 hours to obtain the regenerated lithium iron phosphate cathode material (named RLFP-1).

[0028] <Example 2> A method for regenerating cathode materials from spent lithium iron phosphate batteries specifically includes the following steps: Step S0: Discharge and disassemble the waste lithium iron phosphate batteries to obtain waste positive electrode sheets; Step S1: Soak the waste positive electrode sheet obtained in step S0 in deionized water to separate the waste positive electrode material from the aluminum foil. Finally, dry the collected waste positive electrode material at 80°C for 12 hours. After drying, grind it to obtain waste positive electrode material powder. Step S2: Add 0.3g of waste cathode material powder, 0.3g of gallic acid and 0.4g of lithium acetate obtained in step S1 to 50mL of deionized water, stir for 30min, and then place in a 100mL polytetrafluoroethylene-lined reactor. Heat at 180℃ for 6h. After the reaction is completed, cool to room temperature, and wash the reactants three times with deionized water and anhydrous ethanol by centrifugation. Finally, dry the solid reactants at 80℃ for 12h to obtain intermediate product powder. Step S3: The intermediate product powder obtained in step S2 is placed in an Ar atmosphere and heated to 600°C at a rate of 5°C, and held for 5 hours to obtain the regenerated lithium iron phosphate cathode material (named RLFP-2).

[0029] <Example 3> A method for regenerating cathode materials from spent lithium iron phosphate batteries specifically includes the following steps: Step S0: Discharge and disassemble the waste lithium iron phosphate batteries to obtain waste positive electrode sheets; Step S1: Soak the waste positive electrode sheet obtained in step S0 in deionized water to separate the waste positive electrode material from the aluminum foil. Finally, dry the collected waste positive electrode material at 80°C for 12 hours. After drying, grind it to obtain waste positive electrode material powder. Step S2: Add 0.3g of waste cathode material powder, 0.35g of gallic acid and 0.4g of lithium acetate obtained in step S1 to 50mL of deionized water, stir for 30min, and then place in a 100mL polytetrafluoroethylene-lined reactor. Heat at 180℃ for 6h. After the reaction is completed, cool to room temperature, wash the reactants three times with deionized water and anhydrous ethanol, and finally dry the solid reactants at 80℃ for 12h to obtain intermediate product powder. Step S3: The intermediate product powder obtained in step S2 is placed in an Ar atmosphere and heated to 600°C at a rate of 5°C, and held for 5 hours to obtain the regenerated lithium iron phosphate cathode material (named RLFP-3).

[0030] <Example 4> A method for regenerating cathode materials from spent lithium iron phosphate batteries specifically includes the following steps: Step S0: Discharge and disassemble the waste lithium iron phosphate batteries to obtain waste positive electrode sheets; Step S1: Soak the waste positive electrode sheet obtained in step S0 in deionized water to separate the waste positive electrode material from the aluminum foil. Finally, dry the collected waste positive electrode material at 80°C for 12 hours. After drying, grind it to obtain waste positive electrode material powder. Step S2: Add 0.3g of waste cathode material powder, 0.45g of gallic acid and 0.4g of lithium acetate obtained in step S1 to 50mL of deionized water, stir for 30min, and then place in a 100mL polytetrafluoroethylene-lined reactor. Heat at 180℃ for 6h. After the reaction is completed, cool to room temperature, wash the reactants three times with deionized water and anhydrous ethanol by centrifugation, and finally dry the solid reactants at 80℃ for 12h to obtain intermediate product powder. Step S3: The intermediate product powder obtained in step S2 is placed in an Ar atmosphere and heated to 600°C at a rate of 5°C, and held for 5 hours to obtain the regenerated lithium iron phosphate cathode material (named RLFP-4).

[0031] <Comparative Example 1> The method of this comparative example is the same as that of Example 1, except that Comparative Example 1 is waste lithium iron phosphate material (named SLFP) that has not undergone steps S2 and S3.

[0032] <Comparative Example 2> The method of this comparative example is the same as that of Example 1, except that Comparative Example 2 is a regenerated lithium iron phosphate material (named BLFP) that was not treated with gallic acid in step S2.

[0033] <Comparative Example 3> The method of this comparative example is the same as that of Example 1, except that Comparative Example 3 is a recycled lithium iron phosphate material (named OLFP) that was not treated with lithium acetate in step S2.

[0034] <Test Example> The materials obtained in Examples 1-4 and Comparative Examples 1-3 were characterized in morphology and tested in electrochemical performance using the following methods: Battery Assembly: Weigh 0.08g of positive electrode powder, 0.01g of polyvinylidene fluoride (binder), and 0.01g of acetylene black (conductive agent), grind them in agate slurry for 15min, then add an appropriate amount of N-methylpyrrolidone solution and continue ball milling until a uniform slurry is formed. Coat the slurry uniformly onto aluminum foil with a coating thickness of 150μm, and dry at 80℃ for 12h to obtain the positive electrode sheet. Fabricate the dried positive electrode sheet into a 12mm diameter circular electrode, and use a 15mm diameter, 0.45mm thick lithium metal disc as the negative electrode. Celgard 2325 membrane and 1M LiPF6 (EC:DEC:DMC) (volume ratio 1:1:1) electrolyte are used as the separator and electrolyte, respectively. Then, CR2032 coin cells are prepared in an argon-filled glove box (H2O < 0.01ppm, O2 < 0.01ppm). The battery needs to be left to stand for 8 hours before testing to ensure that the electrolyte is fully immersed.

[0035] The relevant substances were tested, and the results are shown below. Figure 1-7 .

[0036] Figure 1 The X-ray diffraction patterns are of the recycled lithium iron phosphate in Example 1 of the present invention and the waste lithium iron phosphate material in Comparative Example 1.

[0037] from Figure 1 It can be concluded that the waste lithium iron phosphate material has formed a significant FePO4 impurity phase due to irreversible lithium loss during long-term cycling. Simultaneously, the intensity of the characteristic peaks attributed to LiFePO4 has weakened. The phase structure of the recycled lithium iron phosphate material is consistent with the LiFePO4 standard card (PDF#81-1173), and the crystal structure has been fully restored.

[0038] Figure 2 The X-ray diffraction patterns are those of the regenerated lithium iron phosphate obtained in Examples 1-4 of this invention.

[0039] from Figure 2 The crystal phase structure diagrams of regenerated lithium iron phosphate materials under different gallic acid addition amounts can be obtained. When the gallic acid addition amount is 0.3 g, FePO4 impurity phase still exists in RLFP-2. As the gallic acid addition amount increases, Fe(III) is fully reduced, and the crystal structure is restored. The optimal addition amount of gallic acid is 0.4 g.

[0040] Figure 3 These are scanning electron microscope (SEM) images of the regenerated lithium iron phosphate materials obtained in Examples 1-4 of this invention. from Figure 3 As can be seen, with the increase of gallic acid addition, the residual polyvinylidene fluoride (PVDF) and particle cracks on the surface of the recycled lithium iron phosphate material are reduced. When the amount of gallic acid added is 0.4g, the morphology of the recycled lithium iron phosphate material is well restored and the impurity residue is minimal.

[0041] Figure 4 Table 3 shows the cycle performance of the regenerated lithium iron phosphate batteries obtained in Examples 1-4 of this invention at a 1C rate. Table 4 presents the cycle performance data of the regenerated lithium iron phosphate batteries obtained in Examples 1-4 of this invention at a 1C rate. Figure 4The specific test conditions were as follows: the materials obtained in Examples 1-4 were assembled into CR2032 coin cell half-cells, and constant current charge-discharge tests were conducted using a LAND CT2001A battery testing system at room temperature (25 °C). The batteries underwent long-cycle testing at a 1C rate (1C = 170 mA / g) within a voltage window of 2.5-4.3 V. The “Initial Capacity” in Table 3 refers to the discharge specific capacity measured during the first cycle at a 1C rate. The “Capacity Retention Rate” was calculated using the following formula: (Discharge specific capacity after 200 cycles / Initial Capacity) × 100%.

[0042] according to Figure 4 As shown in Table 3, at a 1C rate, the RLFP-1 battery exhibits the best cycle performance, with an initial specific capacity of 143.7 mAh / g. After 200 cycles, its capacity retention reaches 98%, and its coulombic efficiency remains above 99%. This result indicates that the crystal structure and chemical composition of the regenerated lithium iron phosphate material are fully restored, thus improving the battery's cycle performance. RLFP-2 and RLFP-3 did not fully recover their capacity due to insufficient lithium replenishment. RLFP-4, due to excessive gallic acid content, experienced excessive reduction and chelation, which damaged the material structure and affected its electrochemical performance, leading to a decrease in capacity.

[0043] Figure 5 The first charge-discharge curves of the regenerated lithium iron phosphate batteries obtained in Examples 1-4 of this invention at a rate of 0.2C are shown.

[0044] from Figure 5 It can be concluded that at a rate of 0.2C, the first charge-discharge curve of RLFP-1 shows the most stable charge-discharge voltage plateau, indicating that its initial overpotential is low and its battery stability is better.

[0045] Figure 6 These are scanning electron microscope (SEM) images of the waste lithium iron phosphate material of Comparative Example 1 and the recycled lithium iron phosphate materials obtained in Comparative Examples 2-3 of the present invention.

[0046] from Figure 6 As can be seen, the surface of SLFP material contains a large amount of PVDF residual impurities and particle cracks. The surface of BLFP material shows a significant reduction in residual impurities and cracks. The surface of OLFP material still contains some PVDF residues.

[0047] By comparing Example 1 with the comparative example, gallic acid and lithium acetate can effectively regenerate waste lithium iron phosphate materials. This indicates that the regeneration method of Example 1 effectively regenerates waste lithium iron phosphate, restoring the material morphology well.

[0048] Figure 7Table 4 shows the cycle performance of the spent lithium iron phosphate battery of Comparative Example 1 and the regenerated lithium iron phosphate batteries obtained from Comparative Examples 2-3 at 1C rate. Table 4 presents the cycle performance data of the regenerated lithium iron phosphate batteries obtained from Comparative Examples 1-3 and Example 1 at 1C rate. Figure 7 The specific test conditions were as follows: the materials obtained from Comparative Examples 1-3 and Example 1 were assembled into CR2032 coin cell half-cells, and constant current charge-discharge tests were conducted using a LAND CT2001A battery testing system at room temperature (25 °C). The batteries underwent long-cycle testing at a 1C rate (1C = 170 mA / g) within a voltage window of 2.5–4.3 V. The “Initial Capacity” in Table 4 refers to the discharge specific capacity measured during the first cycle at a 1C rate. The “Capacity Retention Rate” was calculated using the following formula: (Discharge specific capacity after 200 cycles / Initial Capacity) × 100%.

[0049] according to Figure 7 As shown in Table 4, the SLFP material suffers structural damage due to irreversible lithium loss during long-term cycling. At 1C rate, its initial specific capacity is only 81.6 mAh / g, and after 200 cycles, the capacity retention is only 49%. Although BLFP receives lithium replenishment, incomplete Fe(III) reduction results in lattice defects, preventing full capacity recovery. OLFP also fails to fully recover its capacity due to lithium loss.

[0050] By comparing Example 1 with the comparative example, the cycle stability and electrochemical performance of RLFP-1 after regeneration were significantly improved, demonstrating the effectiveness of the gallic acid and lithium acetate regeneration method.

[0051] Table 3 Comparison of battery electrochemical performance in Examples 1-4

[0052] Table 4 Comparison of the electrochemical performance of batteries in Comparative Examples 1-3 (including Example 1)

[0053] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for regenerating waste lithium iron phosphate cathode material, characterized in that, Includes the following steps: Step S1: Soak the waste positive electrode sheet in deionized water to separate the waste positive electrode material from the aluminum foil. Dry and grind the waste positive electrode material to obtain waste positive electrode material powder. Step S2: Add the waste cathode material powder, gallic acid and lithium acetate to deionized water, mix evenly, place in a reaction vessel and heat, centrifuge the product after heating, and then dry to obtain intermediate product powder; Step S3: The intermediate product powder is calcined under an inert atmosphere to obtain regenerated lithium iron phosphate cathode material.

2. The method for regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that: In step S2, the amounts of waste cathode material powder, gallic acid, and lithium acetate added are 0.3g, 0.3-0.45g, and 0.4g, respectively, and 50mL of deionized water is added.

3. The method for regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, In step S2, the heating temperature is 160-200℃ and the heating time is 6-10 hours.

4. The method for regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, In step S2, the water is washed 2 to 4 times with deionized water and anhydrous ethanol, respectively, at a centrifugation speed of 8000 rpm and a centrifugation time of 6 to 10 minutes each time.

5. The method for regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, In step S2, the drying temperature is 60-80℃ and the drying time is 12-24 hours.

6. The method for regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, In step S3, the temperature is increased to 600-750°C at a heating rate of 2-10°C, and the holding time is 2-5 hours.

7. The method for regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, In step S1, the drying temperature is 60-80℃ and the drying time is 12-24 hours.

8. The method for regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, In step S3, the inert atmosphere is high-purity argon or high-purity nitrogen.

9. The method for regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, It also includes step S0: discharging and dismantling the waste lithium iron phosphate battery to obtain waste positive electrode sheet.

10. A recycled lithium iron phosphate cathode material, characterized in that, Prepared by the method according to any one of claims 1-9.

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