Method for recycling and regenerating waste lithium iron phosphate positive electrode material

Abstract

The invention belongs to the field of waste battery treatment, and particularly discloses a waste lithium iron phosphate positive electrode material recycling and regenerating method.The waste lithium iron phosphate positive electrode material recycling method comprises the steps that a waste lithium iron phosphate positive electrode material and a leaching solvent are mixed and leached under ultraviolet irradiation, then solid-liquid separation is conducted, and lithium liquid and iron phosphate slag are obtained; the leaching solvent is an aqueous solution in which a component A and a component B are dissolved, and the component A can release free radicals under ultraviolet light; and the component B is disulfate of at least one cation of sodium, potassium and ammonium. According to the method disclosed by the invention, lattice regulation and control in lithium iron phosphate can be efficiently realized, leaching of lithium can be efficiently improved, besides, imbalance of a phosphorus-iron ratio of iron phosphate can also be avoided, and subsequent regeneration and recovery are facilitated.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling and reuse of waste lithium-ion batteries, specifically relating to the recycling and reuse of waste lithium iron phosphate cathode materials. Background Technology

[0002] The rapid development of the global new energy industry has driven a significant increase in the demand for lithium-ion batteries. Against this backdrop, lithium iron phosphate (LiFePO4) has become a highly sought-after cathode material due to its high structural stability, excellent safety performance, and outstanding cost-effectiveness. However, during long-term cycling, the continuous loss of lithium in the lithium iron phosphate cathode leads to a gradual decline in its ion insertion / extraction capability. This degradation further induces lattice distortion, dislocation proliferation, and microcrack formation in lithium iron phosphate. Furthermore, electrolyte decomposition products (such as LiF and LixPOyFz) deposit on the surface of the cathode active material, forming a passivation layer that hinders ion and electron transport, ultimately causing battery performance failure. Currently, recycling technologies for spent lithium iron phosphate cathode materials have been extensively studied. Traditional recycling methods typically involve destroying the stable olivine structure of LiFePO4 through redox reactions, combined with leaching processes such as water leaching and acid leaching to selectively recover and extract the remaining lithium from spent lithium iron phosphate. In addition, emerging technologies such as photocatalysis, electrochemistry, magnetic field-assisted recycling, and biometallurgy are also being actively explored for use in the field of spent battery recycling.

[0003] Existing technologies provide several methods for LiFePO4 recovery. For example, Chinese patent document CN120728064A discloses a method for selectively extracting lithium from waste lithium iron phosphate using hydrogen peroxide and manganese sulfate, while simultaneously utilizing the leached manganese ions as a manganese source to generate a precursor for lithium manganese iron phosphate, ultimately synthesizing a high-performance lithium manganese iron phosphate cathode material. Chinese patent document CN119464722A discloses a method for recovering valuable elements from lithium iron phosphate using ferric oxide-assisted extraction. Specifically, it describes mixing waste lithium iron phosphate material with ferric oxide, then subjecting it to heat treatment with an inert gas, followed by leaching and solid-liquid separation to obtain a lithium extract and a leaching residue containing iron phosphate and ferrous oxide. Chinese patent document CN119660698A discloses a method for regenerating lithium iron phosphate in electrode materials, specifically including the following steps: mixing lithium iron phosphate-containing cathode material powder, a photocatalyst, and glacial acetic acid, and then introducing oxygen to carry out a photocatalytic reaction. After the reaction, the reaction solution is separated into a filtrate and a filter residue. Sodium carbonate is added to the filtrate and the pH is adjusted by heating to obtain lithium carbonate. The filter residue is heated and dried to obtain iron phosphate. The two are then mixed and reduced by calcination to obtain regenerated lithium iron phosphate.

[0004] In summary, among the current mainstream methods for recycling waste lithium iron phosphate, high-temperature metallurgy technology has high recycling costs due to the need for high-temperature conditions, while hydrometallurgical technology suffers from low efficiency and large amounts of wastewater and waste acid generation. How to efficiently and rationally recover valuable metal elements from waste LiFePO4 cathode materials and achieve resource utilization is a significant challenge facing the current industrial development and upgrading process. Summary of the Invention

[0005] In view of the problems of low recycling efficiency, high cost and unsatisfactory value of recycled materials in existing waste lithium iron phosphate recycling, the purpose of this invention is to provide a recycling method for waste lithium iron phosphate, which aims to efficiently recover valuable metals from waste lithium iron phosphate and recycle them for secondary use.

[0006] The second objective of this invention is to provide a method for regenerating waste lithium iron phosphate, aiming to achieve the resource-based recycling of waste materials.

[0007] Traditional wet lithium extraction processes for waste lithium iron phosphate cathode materials often rely on high-concentration strong oxidants and acids. While achieving good lithium extraction results, these processes pose certain safety hazards and environmental pollution problems. To address this issue, this invention proposes the following improvement:

[0008] A method for recycling waste lithium iron phosphate cathode materials involves mixing the waste lithium iron phosphate cathode materials with a leaching solvent and leaching them under ultraviolet light irradiation, followed by solid-liquid separation to obtain lithium liquid and iron phosphate residue.

[0009] The leaching solvent is an aqueous solution containing components A and B, wherein component A is a component that can release free radicals under ultraviolet light; and component B is a hydrogen sulfate salt of at least one cation selected from sodium, potassium, and ammonium.

[0010] This invention innovatively demonstrates that by combining components A and B with ultraviolet irradiation, a large number of free radicals can be released with a low amount of leaching agent. This can efficiently achieve lattice regulation in lithium iron phosphate, effectively improve lithium leaching, and also avoid imbalance in the phosphorus-iron ratio of iron phosphate, which is beneficial for subsequent regeneration and recycling.

[0011] In this invention, the waste lithium iron phosphate cathode material is obtained by stripping the cathode sheet of waste lithium iron phosphate batteries;

[0012] Preferably, the content of lithium iron phosphate in the waste lithium iron phosphate cathode material is above 70 wt.%.

[0013] In the leaching solvent, component A includes at least one of hydrogen peroxide, water-soluble persulfate, water-soluble permonosulfate, and peracetic acid. The water-soluble persulfate and water-soluble permonosulfate can be at least one of their respective sodium or ammonium salts. Preferably, component A is hydrogen peroxide. Using hydrogen peroxide as component A, in combination with component B and ultraviolet irradiation, can unexpectedly improve leaching efficiency, leaching effect, and leaching selectivity.

[0014] In this invention, the concentration of component A in the solvent is 5-20 vol%; the mass ratio of component B to the waste lithium iron phosphate cathode material is 0.5-1.5; preferably, the concentration of component A is 8-15 vol%; the mass ratio of component B to the waste lithium iron phosphate cathode material is 0.8-1.4; more preferably, the concentration of component A is 10-12 vol%; the mass ratio of component B to the waste lithium iron phosphate cathode material is 1-1.2. This invention demonstrates that under the preferred conditions, superior leaching and regeneration effects can be obtained.

[0015] In this invention, the liquid-to-solid ratio during the leaching process is 10-80 mL / g, and can be further 20-60 mL / g;

[0016] Preferably, the power of ultraviolet irradiation is 20~150 W, more preferably 50~120 W; and even more preferably 90~110 W. Studies have shown that the preferred ultraviolet power helps to synergize with component A and component B, and helps to further improve the extraction rate and selectivity of lithium.

[0017] The wavelength of ultraviolet light is 240~420 nm;

[0018] Preferably, the temperature during the leaching process is 15~60 ℃; further, it can be room temperature (e.g., 20~30 ℃). The leaching time can be reasonably adjusted as needed, but thanks to the leaching method described in this invention, the leaching time can be controlled within 60 min, further, it can be 10~40 min; further, it can be 15~25 min.

[0019] The present invention also provides a method for regenerating waste lithium iron phosphate cathode materials, wherein the waste lithium iron phosphate cathode materials are processed by the recycling method described in the present invention to obtain lithium liquid and iron phosphate slag.

[0020] Lithium products are recovered from lithium liquid; iron phosphate slag is subjected to alkali treatment, acid treatment and roasting treatment in sequence to obtain iron phosphate precursor;

[0021] Lithium products, iron phosphate precursors, carbon sources, and water are mixed to obtain a mixed slurry, which is then hydrothermally regenerated to obtain regenerated lithium iron phosphate.

[0022] Thanks to the aforementioned recycling method, this invention can achieve efficient separation of lithium and iron phosphate. In addition, it can avoid imbalance in the ratio of phosphorus to iron and promote beneficial hybridization, which is conducive to subsequent regeneration to obtain high-performance lithium iron phosphate active materials.

[0023] In this invention, the lithium liquid is pre-aged at pH 8-12, followed by solid-liquid separation and carbonation precipitation to obtain lithium products in the lithium carbonate phase.

[0024] In this invention, the pH of the alkali treatment process is 8-12; the alkali solution used in the alkali treatment can be at least one of sodium hydroxide, potassium hydroxide, and ammonia water.

[0025] The acid solution used for acid treatment is 0.1~0.5 M hydrochloric acid;

[0026] The calcination temperature is 300~700 ℃, further can be 400~600 ℃, and even further can be 450~550 ℃; at the preferred temperature, it is helpful to better control the physicochemical structure and further enhance the performance of regenerated lithium iron phosphate.

[0027] The roasting time is 2-4 hours.

[0028] In this invention, the Li / Fe molar ratio in the lithium product and the iron phosphate precursor is 1~1.07:1;

[0029] The carbon source is at least one of glucose, sucrose, and citric acid, and the carbon source is 5-15% of the total mass of lithium product and iron phosphate precursor; more specifically, it can be 8-12%.

[0030] The mixed slurry also contains additives, including at least one selected from titanium dioxide, zinc oxide, iron oxide, and tin oxide. Titanium dioxide is preferred. The combination of the preferred additives and the process described in this invention is expected to further enhance regeneration performance.

[0031] The additive is 1 to 10% of the total mass of the iron phosphate precursor, preferably 2 to 5%.

[0032] Preferably, the mixed slurry is pretreated under ultraviolet irradiation.

[0033] The pretreatment, performed with the aforementioned additives and under ultraviolet irradiation, followed by subsequent hydrothermal treatment, can further optimize the physicochemical structure of regenerated LFP and help to further enhance its regeneration performance.

[0034] Preferably, the power during the ultraviolet irradiation pretreatment process is 20~150 W; more preferably, it can be 80~120 W.

[0035] The wavelength is 240~420 nm;

[0036] The UV irradiation pretreatment time is 20~60 min.

[0037] Preferably, the hydrothermal temperature is 150~250 ℃, and more preferably 160~220 ℃.

[0038] The hydrothermal time is 5~25 h, and can be further extended to 5~10 h.

[0039] Beneficial effects

[0040] This invention innovatively employs photocatalytic recycling of waste lithium iron phosphate cathode materials, enabling faster recovery of valuable metals from waste lithium iron phosphate with less oxidant and acid. Furthermore, it can further regenerate lithium iron phosphate batteries, significantly optimizing the recycling process, reducing recycling costs, and making it suitable for large-scale industrial production.

[0041] Furthermore, hydrothermal regeneration following the aforementioned additives and UV-assisted pretreatment helps to further enhance the electrochemical performance of the regenerated materials. Attached Figure Description

[0042] Figure 1 The image shows the XRD pattern of the waste lithium iron phosphate cathode material from Example 1.

[0043] Figure 2 The image shows the XRD pattern of the ferric phosphate slag from Example 1.

[0044] Figure 3 This is a cycle diagram of the regenerated lithium iron phosphate battery in Example 1. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] In the following examples, as an optional solution, the waste lithium iron phosphate mainly contains 31% iron, 19% phosphorus, and approximately 4% lithium, and originates from a company in Jiangxi Province. In this invention, the "approximately" can be, for example, ±0.5%.

[0047] Example 1

[0048] Step 1. Discharge, crushing, and sieving: Immerse the battery in 5-10% salt water for 12 hours to discharge, crush it into powder of 30-40 mm, pyrolyze it under an inert atmosphere at 500-600 ℃, and sieve it to obtain black powder.

[0049] Step 2. Under 100 W ultraviolet light, mix 30 g of waste lithium iron phosphate cathode material with leaching solvent. The leaching agent contains an aqueous solution of component A (hydrogen peroxide) and component B (sodium bisulfate). The concentration of component A in the leaching solvent is 10 vol%, and the weight ratio of component B to the waste lithium iron phosphate material to be leached is 1:1.

[0050] After mixing and leaching at 30 ℃ and a liquid-to-solid ratio of 40:1 mL / g, the complete reaction time was 15 min. Solid-liquid separation was then performed to obtain a lithium-containing leachate and phosphorus-iron slag. The leaching rates of lithium, iron, and phosphorus were 98.93%, 2.7%, and 3.4%, respectively.

[0051] Step 3. Add sodium hydroxide to the leachate to adjust the pH to about 10 for co-precipitation. Aged the filtrate at 80 °C for 3 h with a stirring speed of 300 r / min. Filter and separate the precipitate. Heat the leachate filtrate to 90 °C and add sodium carbonate until no more precipitate is formed. Filter, separate the precipitate, wash with deionized water 3 times and dry to obtain lithium carbonate product.

[0052] Step 4. Add sodium hydroxide to the filter residue (iron phosphate slag) obtained in Step 2 to adjust the pH to about 10, stir and wash for 1 h, then wash with water and filter. Wash the filtered filter residue with 0.2 mol / L dilute hydrochloric acid for 1 h, wash with water and filter again and dry. Calcine the filter residue in a muffle furnace at 500 ℃ for 3 h to obtain the iron phosphate precursor.

[0053] Step 5. Mix the product obtained in Step 3 (lithium product), the product obtained in Step 4 (iron phosphate), carbon source (glucose), and additive (titanium dioxide) with water (the solid content in the mixed slurry is 30~35%), and pre-treat it under normal pressure with stirring and ultrasound, and the pre-treatment process is carried out under ultraviolet irradiation.

[0054] In the mixed slurry, the Li / Fe molar ratio is 1.05:1;

[0055] The carbon source is 10% of the total weight of lithium products and iron phosphate;

[0056] The auxiliary agent is 5% of the weight of ferric phosphate;

[0057] The stirring speed was 350 r / min; the ultrasonic power was 150 W, and the frequency was 40 kHz; the UV-assisted atmospheric pressure pretreatment time was 30~40 min. The irradiation power was 100 W, and the wavelength was 254 nm.

[0058] Step 6. The pretreated slurry was then heated to 180 °C at a heating rate of 5 °C / min and kept at that temperature for 8 h for hydrothermal reaction. After hydrothermal reaction, the resulting solution was centrifuged at 6000 r / min for 15 min to obtain a precipitate, which was then washed and dried to obtain regenerated lithium iron phosphate.

[0059] Step 7. Place the regenerated lithium iron phosphate from Step 6, conductive carbon black (conductive agent), and PVDF (binder) in a container at a mass ratio of 8:1:1. Add an appropriate amount of N-methylpyrrolidone (NMP) solvent and grind thoroughly to form a uniform and fine slurry. Use a 100 μm coater to uniformly coat the mixed slurry onto a clean glass plate covered with aluminum foil. Place the coated substrate in a vacuum drying oven and dry at 120 °C for 12 h to completely remove the solvent from the slurry, obtaining a dense and flat positive electrode sheet. Use a button cell slicing machine to cut the dried positive electrode sheet into small round pieces with a diameter of 12 mm. Assemble them in an argon-filled glove box. The assembly sequence from bottom to top is: positive electrode shell, positive electrode sheet, separator (Celigard-2400), lithium metal sheet, gasket, spring sheet, and negative electrode shell. Then, encapsulate them using a packaging machine. During assembly, the electrolyte (1 mol / L LiPF6 organic solution, wherein the solvent is a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1, using a lithium-ion secondary battery-specific electrolyte) is placed before and after the separator. After the assembled battery is sealed, it is left to stand at room temperature (25 °C) for 24 h to allow the electrolyte to fully wet the electrodes and separator. Electrochemical performance is tested by constant current charge-discharge cycling at a voltage of 2.4–4 V and a current density of 0.1 C. Its 0.1 C discharge specific capacity is 173.58 mAh / g, and the capacity retention rate after 300 cycles is 96.15%.

[0060] Example 2

[0061] Compared with Example 1, the only difference is the light intensity during leaching in step 2, specifically:

[0062] Group A: The UV lamp was replaced with a 50 W lamp, while all other conditions remained unchanged. In step 2, the leaching rate of lithium was 96.52%, the leaching rate of iron was 3.38%, and the leaching rate of phosphorus was 3.1%. The complete reaction time was 22 min.

[0063] Group B: Replace the UV lamp with a 30 W lamp, keeping all other conditions unchanged. In step 2, the leaching rate of lithium was 92.52%, the leaching rate of iron was 7.51%, and the leaching rate of phosphorus was 6.34%. The complete reaction time was 25 min.

[0064] Example 3

[0065] Compared with Example 1, the only difference is that the type of component A is changed, specifically:

[0066] Group A: Component A was replaced with sodium persulfate, while all other conditions remained unchanged. Step 2) The leaching rate of lithium was 89.55%, the leaching rate of iron was 7.21%, and the leaching rate of phosphorus was 5.41%. The complete reaction time was 23 min.

[0067] Group B: Replace component A with peracetic acid, keeping all other conditions unchanged. Step 2) The leaching rate of lithium was 92.73%, the leaching rate of iron was 8.54%, and the leaching rate of phosphorus was 9.39%. The complete reaction time was 21 min.

[0068] In summary, using hydrogen peroxide as component A, combined with component B and ultraviolet irradiation, unexpectedly improved leaching efficiency, leaching effect, and leaching selectivity.

[0069] Example 4

[0070] Compared to Example 1, the only difference lies in the leaching conditions of step 2. Specifically, the concentration of component A in the leaching solvent is changed to 15 vol%, the mass ratio of component B to waste lithium iron phosphate is 1.2:1, and the liquid-to-solid ratio during leaching is 60:1, while other conditions remain unchanged. In step 2), the leaching rate of lithium is 94.02%, the leaching rate of iron is 1.07%, and the leaching rate of phosphorus is 2.19%. The complete reaction time is approximately 25 minutes.

[0071] Example 5

[0072] Compared with Example 1, the only difference is that the reaction conditions during the calcination of the filter residue in step 4 are changed, specifically the calcination temperature is 300 ℃, 350 ℃ and 400 ℃. The 0.1 C discharge specific capacities of the synthesized regenerated lithium iron phosphate are 152.11, 162.66 and 164.37 mAh / g, respectively, and the capacity retention rates after 300 cycles are 85.31%, 89.66% and 93.13%, respectively.

[0073] Example 6

[0074] Compared with Example 1, the only difference is that in step 5, sucrose and citric acid are used instead of glucose as carbon sources. After synthesizing regenerated lithium iron phosphate, the 0.1 C discharge specific capacity is 162.99 and 168.06 mAh / g, respectively, and the capacity retention rate after 300 cycles is 93.01% and 92.67%, respectively.

[0075] Example 7

[0076] Compared to Example 1, the only difference is that in step 5, the additive is either zinc oxide or tin oxide. The results are as follows:

[0077] After synthesis, the 0.1 C discharge specific capacities of the regenerated lithium iron phosphate were 161.52 and 169.77 mAh / g, respectively, and the capacity retention rates after 300 cycles were 91.23% and 93.32%, respectively.

[0078] Example 8

[0079] Compared with Example 1, the only difference is that in step 5, the Li / Fe molar ratio in the mixed slurry is 1.04:1;

[0080] The carbon source is 8% of the total weight of lithium products and iron phosphate;

[0081] The additive is 3% of the weight of ferric phosphate;

[0082] After synthesizing regenerated lithium iron phosphate, its 0.1 C discharge specific capacity is 169.37 mAh / g, and the capacity retention rate after 300 cycles is 94.56%.

[0083] Example 9

[0084] Compared with Example 1, the only differences are that in step 5, the ultraviolet power is 80W; the ultraviolet irradiation time is 50~55min; and in step 6, the hydrothermal temperature is 200℃ and the time is 6h. Its 0.1C discharge specific capacity is 174.92 mAh / g, and the capacity retention rate after 300 cycles is 94.48%.

[0085] Example 10

[0086] Compared with Example 1, the only difference is that ultraviolet irradiation was not performed in step 5, but instead under normal natural light. All other operations and parameters are the same as in Example 1. The results are as follows: the 0.1 C discharge specific capacity of the synthesized regenerated lithium iron phosphate is 155.61 mAh / g, and the capacity retention rate after 300 cycles is 85.28%.

[0087] Example 11

[0088] Compared with Example 1, the only difference is that no additives were added in step 5. All other operations and parameters are the same as in Example 1. After synthesizing regenerated lithium iron phosphate, its 0.1 C discharge specific capacity is 153.49 mAh / g, and the capacity retention rate after 300 cycles is 84.01%.

[0089] Example 12

[0090] Compared with Example 1, the only difference is that manganese dioxide was used as an additive in step 5; all other operations and parameters were the same as in Example 1. The results showed that the 0.1 C discharge specific capacity was 152.34 mAh / g, and the capacity retention rate after 300 cycles was 84.85%.

[0091] Comparative Example 1

[0092] Compared to Example 1, the only difference is that in step 2, no ultraviolet irradiation was performed; the operation was carried out under normal natural light. All other operations and parameters remained the same as in Example 1. The results showed that after 40 minutes, the lithium leaching rate was 85.73%, the iron leaching rate was 11.9%, and the phosphorus leaching rate was 9.72%. Its 0.1 C discharge specific capacity was 142.01 mAh / g, and the capacity retention rate after 300 cycles was 81.85%.

[0093] Comparative Example 2

[0094] Compared with Example 1, the only difference is that in step 2, component B in the leaching solvent is changed; all other operations and parameters are the same as in Example 1. Specifically:

[0095] Group A: Replace sodium bisulfate with sulfuric acid by an equal weight;

[0096] Group B: Replace sodium bisulfate with oxalic acid by the same weight;

[0097] Group C: Sodium bicarbonate is used as component B;

[0098] Group D: Sodium dihydrogen phosphate was used as component B.

[0099] The results are as follows:

[0100] Group A: In step 2, the leaching rate of lithium was 99.15%, the leaching rate of iron was 16.12%, and the leaching rate of phosphorus was 15.83%. Its 0.1 C discharge specific capacity was 141.37 mAh / g, and the capacity retention rate after 300 cycles was 79.66%.

[0101] Group B: In step 2, the leaching rates of lithium, iron, and phosphorus were 79.11%, 14.63%, and 11.46%, respectively. Its 0.1 C discharge specific capacity was 135.01 mAh / g, and its capacity retention rate after 300 cycles was 77.85%.

[0102] Group C: In step 2, the leaching rate of lithium was 59.73%, the leaching rate of iron was 2.15%, and the leaching rate of phosphorus was 5.57%.

[0103] Group D: In step 2, the leaching rate of lithium was 92.73%, the leaching rate of iron was 3.44%, and the leaching rate of phosphorus was 65.83%.

[0104] Comparative Example 3

[0105] Compared with Example 1, the only difference is that in step 2, the type of component A in the leaching solvent is changed, specifically:

[0106] Group A: Component A was replaced with oxygen, the flow rate was 1.5 L / min, and all other conditions remained unchanged. In step 2, the leaching rate of lithium was 89.55%, iron was 7.21%, and phosphorus was 5.41%. The complete reaction time was 90 min. Its 0.1 C discharge specific capacity was 141.55 mAh / g, and the capacity retention rate after 300 cycles was 82.85%.

[0107] Group B: Component A was replaced with sodium hypochlorite, while all other conditions remained unchanged. In step 2, the leaching rates of lithium, iron, and phosphorus were 89.55%, 7.21%, and 5.41%, respectively. The complete reaction time was 50 min. Its 0.1 C discharge specific capacity was 150.69 mAh / g, and the capacity retention rate after 300 cycles was 83.66%.

Claims

1. A method for recycling waste lithium iron phosphate cathode materials, characterized in that, Waste lithium iron phosphate cathode material and leaching solvent are mixed and leached under ultraviolet light irradiation, followed by solid-liquid separation to obtain lithium liquid and iron phosphate residue; The leaching solvent is an aqueous solution containing components A and B, wherein component A is a component that can release free radicals under ultraviolet light; and component B is a hydrogen sulfate salt of at least one cation selected from sodium, potassium, and ammonium.

2. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, The waste lithium iron phosphate cathode material is obtained by stripping the cathode sheet of waste lithium iron phosphate batteries; Preferably, the content of lithium iron phosphate in the waste lithium iron phosphate cathode material is above 70 wt.%.

3. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, In the leaching solvent, component A includes at least one of hydrogen peroxide, water-soluble persulfate, water-soluble permonosulfate, and peracetic acid.

4. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, In the solvent, the concentration of component A is 5~20 vol%; the mass ratio of component B to waste lithium iron phosphate cathode material is 0.5~1.

5.

5. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, The liquid-to-solid ratio during the leaching process is 10~80 mL / g; Preferably, the power of the ultraviolet irradiation is 20~150 W; Preferably, the temperature during the leaching process is 15~60℃; Preferably, the leaching time is within 60 minutes.

6. A method for regenerating waste lithium iron phosphate cathode material, characterized in that, Waste lithium iron phosphate cathode material is processed using the recycling method described in any one of claims 1 to 5 to obtain lithium liquid and iron phosphate residue; Lithium products are recovered from lithium liquid; iron phosphate slag is subjected to alkali treatment, acid treatment and roasting treatment in sequence to obtain iron phosphate precursor; Lithium products, iron phosphate precursors, carbon sources, and water are mixed to obtain a mixed slurry, which is then hydrothermally regenerated to obtain regenerated lithium iron phosphate.

7. The method for regenerating waste lithium iron phosphate cathode material as described in claim 6, characterized in that, The lithium liquid was pre-aged at pH 8-12, followed by solid-liquid separation and carbonation precipitation to obtain lithium products in the lithium carbonate phase.

8. The method for regenerating waste lithium iron phosphate cathode material as described in claim 6, characterized in that, The pH during the alkali treatment process is 8-12; The acid solution used for acid treatment is 0.1~0.5 M hydrochloric acid; The roasting temperature is 300~700 ℃; The roasting time is 2-4 hours.

9. The method for regenerating waste lithium iron phosphate cathode material as described in claim 6, characterized in that, The Li / Fe molar ratio in lithium products and iron phosphate precursors is 1~1.07:1; The carbon source is at least one of glucose, sucrose, and citric acid, and the carbon source accounts for 5-15% of the total mass of lithium products and iron phosphate precursors. The mixed slurry also contains additives, including at least one of titanium dioxide, zinc oxide, ferric oxide and tin oxide, and the additives are 1-10% of the total mass of the iron phosphate precursor, preferably 2-5%. Preferably, the mixed slurry is pretreated under ultraviolet irradiation.

10. The method for regenerating waste lithium iron phosphate cathode material as described in any one of claims 6 to 9, characterized in that, The hydrothermal temperature is 150~250 ℃, and the time is 5~25 h.

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