Lithium iron phosphate regeneration method based on mechanical activation and selective leaching

Abstract

The invention discloses a lithium iron phosphate regeneration method based on mechanical activation and selective leaching, and relates to the technical field of lithium ion battery recovery, and the method comprises the following steps: firstly, carrying out mechanical activation pretreatment, destroying an LFP crystal structure through ball milling, reducing the particle size, and increasing the specific surface area; then, selective leaching separation is carried out, and FePO4. 2H2O sediment is generated; and then carrying out hydrothermal regeneration synthesis on the precipitation residues, and carrying out hydrothermal reaction to generate the carbon-coated lithium iron phosphate LFP / C composite material. Through the synergistic effect of mechanical activation and selective leaching, the problems of low lithium recovery rate, incomplete iron and phosphorus separation, high energy consumption and the like in the prior art are solved, the bottleneck of short cycle life of the existing regenerated LFP material is broken through, and the capacity retention rate of the regenerated material after 1400 cycles at 25 DEG C and 1C is still greater than 91.5% and is close to the level of a primary material by introducing a LiFePO4 (OH) intermediate through hydrothermal synthesis.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery recycling technology, specifically a lithium iron phosphate regeneration method based on mechanical activation and selective leaching. Background Technology

[0002] With the rapid development of the new energy vehicle industry, lithium iron phosphate (LFP) power batteries, as a core component, are experiencing a retirement rate exceeding 30% annually. Industry forecasts predict that by 2030, the global scale of retired LFP batteries will exceed 5 million tons. If efficient recycling cannot be achieved, it will not only result in the waste of millions of tons of strategic metal resources but also cause serious environmental pollution problems.

[0003] However, existing pyrometallurgical processes require high-temperature reduction roasting at temperatures above 800°C, consuming up to 5000 kWh / ton of energy. The high temperatures also cause severe equipment corrosion, and the separation cost accounts for 42% of the total recovery cost.

[0004] Existing wet processes require steps such as acid leaching, extraction, and precipitation, which are lengthy and result in lithium recovery rates of only 85%-90% and iron leaching rates exceeding 10%, leading to difficulties in subsequent impurity removal.

[0005] Regenerated LFP materials prepared by existing methods require solid-state sintering at temperatures above 700 degrees Celsius, with energy consumption accounting for 35% of the total cost, and the cycle life is only 70% of that of virgin materials. Furthermore, regenerated LFP materials prepared by existing methods suffer from lattice defects and uneven carbon coating, leading to excessively rapid discharge capacity decay.

[0006] A patent with publication number CN117276700A describes a method for regenerating spent lithium iron phosphate batteries by combining spontaneous reactions. This method increases the lithium content in lithium iron phosphate batteries in their lithium-deficient state by introducing a spontaneous lithium intercalation reaction, thereby reducing energy consumption during subsequent external lithium intercalation. However, it suffers from problems such as insufficient lithium intercalation depth and poor consistency of the recycled materials. Summary of the Invention

[0007] The purpose of this invention is to provide a lithium iron phosphate regeneration method based on mechanical activation and selective leaching to solve the problems in the prior art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A lithium iron phosphate regeneration method based on mechanical activation and selective leaching includes the following steps: S1: Mechanical activation pretreatment is performed, and the LFP crystal structure is destroyed by ball milling, reducing the particle size to 2-5 μm and increasing the specific surface area to 15-20 m². 2 / g; S2: Subsequently, selective leaching separation is performed using a sulfuric acid + sodium persulfate system, with the pH value controlled and adjusted to 2-3, thereby allowing Fe... 3+ Hydrolysis is inhibited, PO4 3- with Fe 3+ Combined to form FePO4·2H2O precipitate; S3: Next, the precipitated residue is hydrothermally regenerated and synthesized to generate carbon-coated lithium iron phosphate (LFP / C) composite material through hydrothermal reaction.

[0009] Based on the above technical solutions, the present invention also provides the following optional technical solutions: In one alternative embodiment, step S1 includes the following steps: S11: Disassemble retired lithium iron phosphate batteries under nitrogen protection and separate the positive electrode sheet containing LFP, PVDF, and carbon black; S12: Place the disassembled and crushed positive electrode sheet, zirconium oxide beads, and CTAB into a planetary ball mill, set the ball milling speed to 300-500 rpm, and the ball milling time to 30-60 minutes to obtain pretreated powder.

[0010] In one alternative: the planetary ball mill reduces the LFP particle size from 20 μm to 2-5 μm and the specific surface area from 5 m² through high-frequency collisions of zirconia beads. 2 / g increased to 15-20m 2 / g, the ball milling media ratio is 5:1-10:1.

[0011] In one alternative embodiment, step S2 includes the following steps: S21: Add the pretreated powder to a 1.0 mol / L sulfuric acid solution; S22: Sodium persulfate is added to the solution, where sodium persulfate acts as an oxidizing agent, promoting the reaction of Li. + Leaching: The oxygen produced will dissolve Fe 2+ Oxidized to Fe 3+ This disrupts the LFP lattice structure, causing Li + Preferential dissolution; S23: pH is adjusted to 2-3 using sulfuric acid; Fe 3+ Hydrolysis is inhibited, PO4 3- with Fe 3+ The FePO4·2H2O precipitate is formed, thereby achieving efficient separation of lithium and iron.

[0012] In one alternative: the amount of sodium persulfate added in step S22 is 1-3 times the molar amount of sulfuric acid, and the reaction temperature is controlled at 40-60℃.

[0013] In one alternative: the liquid-to-solid ratio of the persulfate to sodium persulfate is 10:1-20:1 mL / g.

[0014] In one alternative embodiment, step S3 includes the following steps: S31: After washing with water, the leaching precipitate residue is dissolved in 1-2 mol / L phosphoric acid solution at 80-100℃, and the pH is adjusted to 4-5 to redefine FePO4·2H2O, with a purity greater than 99%. S32: In the hydrothermal reaction, Li2CO3 and FePO4·2H2O generate layered LiFePO4(OH) in the presence of glucose. The interlayer lithium ion diffusion coefficient is two orders of magnitude higher than that of olivine-type LFP. S33: Glucose decomposes into amorphous carbon under high-temperature calcination, which uniformly coats the surface of LFP particles with a thickness of 2-5 nm. The material's electrical conductivity ranges from 10... -9 S / cm increased to 10 -3 S / cm.

[0015] In one alternative: in step S32, Li2CO3, FePO4·2H2O and glucose are mixed in a molar ratio of 1:1:1.

[0016] In one alternative: in step S33, glucose is calcined at a high temperature in argon gas, with a calcination temperature of 600-700℃.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention solves the problems of low lithium recovery rate, incomplete iron-phosphorus separation, and high energy consumption in the prior art through the synergistic effect of mechanical activation and selective leaching. It breaks through the bottleneck of short cycle life of existing recycled LFP materials. By introducing LiFePO4(OH) intermediate through hydrothermal synthesis, the capacity retention rate of the recycled material is still greater than 91.5% after 1400 cycles at 25℃ and 1C, which is close to the level of the original material.

[0018] 2. This invention reduces the amount of chemical reagents used by designing an acid-free leaching system and recycling wastewater. At the same time, it reduces the cost of recycling each ton of retired batteries, improves economic efficiency, and significantly increases profits compared to traditional wet processes. Attached Figure Description

[0019] Figure 1 This is a flowchart of the present invention.

[0020] Figure 2 This is a flowchart of step S1 of the present invention.

[0021] Figure 3 This is a flowchart of step S2 of the present invention.

[0022] Figure 4 This is a flowchart of step S3 of the present invention.

[0023] Figure 5 This is a comparison chart of the initial discharge capacity of embodiments and comparative examples of the present invention.

[0024] Figure 6 This is a comparison chart of the initial discharge efficiency of the embodiments and comparative examples of the present invention.

[0025] Figure 7 This is a comparison chart of the CV percentage during the first charge of an embodiment of the present invention and a comparative example.

[0026] Figure 8 This is a comparison diagram of the internal resistance of AC circuits in the embodiments and comparative examples of the present invention.

[0027] Figure 9 This is a comparison chart of the 25°C 1C cycle between the embodiments of the present invention and the comparative examples.

[0028] Figure 10 This is a comparison diagram of the 45°C 1C cycle between the embodiments and comparative examples of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] In one embodiment, such as Figures 1-4 As shown, a lithium iron phosphate regeneration method based on mechanical activation and selective leaching includes the following steps: S1: Mechanical activation pretreatment is performed, and the LFP crystal structure is destroyed by ball milling, reducing the particle size to 2-5 μm and increasing the specific surface area to 15-20 m². 2 / g; S2: Subsequently, selective leaching separation is performed using a sulfuric acid + sodium persulfate system, with the pH value controlled and adjusted to 2-3, thereby allowing Fe... 3+ Hydrolysis is inhibited, PO4 3- with Fe 3+ Combined to form FePO4·2H2O precipitate; S3: Next, the precipitated residue is hydrothermally regenerated and synthesized to generate carbon-coated lithium iron phosphate (LFP / C) composite material through hydrothermal reaction.

[0031] It should be noted that step S1 involves ball milling to disrupt the LFP crystal structure, thereby increasing the specific surface area and improving subsequent leaching efficiency.

[0032] Step S2 employs a specific leaching system to achieve efficient separation of lithium, iron, and phosphorus.

[0033] Step S3 generates a high-performance carbon-coated lithium iron phosphate (LFP / C) composite material through a hydrothermal reaction.

[0034] In one embodiment, such as Figure 2 As shown, step S1 includes the following steps: S11: Disassemble retired lithium iron phosphate batteries under nitrogen protection and separate the positive electrode sheet containing LFP, PVDF, and carbon black; Nitrogen protection can isolate the reaction conditions and effectively prevent Fe from entering LFP. 2+ Oxidized to Fe 3+ This preserves the original structure of the material, providing a foundation for subsequent efficient leaching. S12: Place the disassembled and crushed positive electrode sheet, zirconium oxide beads, and CTAB into a planetary ball mill. Set the ball milling speed to 300-500 rpm and the ball milling time to 30-60 minutes to obtain pretreated powder. CTAB molecules are adsorbed onto the surface of LFP particles through hydrophobic chains, forming a steric hindrance effect, which effectively inhibits the secondary agglomeration of particles during the ball milling process and ensures uniform particle size distribution.

[0035] The planetary ball milling process reduces the LFP particle size from 20 μm to 2-5 μm and the specific surface area from 5 m² through high-frequency collisions of zirconia beads. 2 / g increased to 15-20m 2 / g, the ball milling media ratio is 5:1-10:1.

[0036] When the ball-to-material ratio is less than 5:1, the collision frequency is insufficient and the activation effect is significantly reduced; when it is greater than 10:1, it may lead to increased wear of zirconia beads, introduce ZrO2 impurities, and affect the purity of subsequent leachate.

[0037] In one embodiment, such as Figure 3 As shown, step S2 includes the following steps: S21: The pretreated powder is added to a 1.0 mol / L sulfuric acid solution to provide a suitable acidic environment for the subsequent oxidative leaching reaction; S22: Sodium persulfate is added to the solution, where sodium persulfate acts as an oxidizing agent. The oxygen produced by the decomposition of sodium persulfate will oxidize Fe. 2+ Oxidized to Fe 3+ This change disrupts the crystal lattice structure of LFP (lithium iron phosphate), making Li... + It can preferentially dissolve from the crystal lattice and promote the reaction of Li + Leaching: The oxygen produced will dissolve Fe 2+ Oxidized to Fe 3+ This disrupts the LFP lattice structure, causing Li + Preferential dissolution; S23: By controlling the pH value to 2-3 with sulfuric acid, Fe can be effectively inhibited. 3+ The hydrolysis reaction further prevents the formation of Fe(OH)3 precipitate, PO4 3- with Fe 3+ The precipitation reaction, which produces FePO4·2H2O precipitate, achieves efficient separation of lithium from iron and phosphorus because Li + It remains dissolved in the solution, while Fe 3+ and PO4 3- It is then removed in the form of precipitation.

[0038] In step S22, the amount of sodium persulfate added is 1-3 times the molar amount of sulfuric acid, and the reaction temperature is controlled at 40-60℃ to optimize the reaction rate and selectivity. Too low a temperature will slow down the reaction rate, while too high a temperature may cause the sodium persulfate to decompose and reduce the oxidation effect.

[0039] In addition, the liquid-to-solid ratio of the persulfate to sodium persulfate is 10:1-20:1 mL / g to ensure the leaching reaction proceeds fully and the precipitate is effectively separated.

[0040] In one embodiment, such as Figure 4 As shown, step S3 includes the following steps: S31: The leaching precipitate residue is washed with water to remove surface impurities, dissolved in 1-2 mol / L phosphoric acid solution at 80-100℃ to further extract and purify iron and phosphorus elements, and the pH is adjusted to 4-5 to redefine FePO4·2H2O with a purity greater than 99%, ensuring the high purity of iron and phosphorus components in the recycled material. S32: In the hydrothermal reaction, Li2CO3 and FePO4·2H2O generate layered LiFePO4(OH) in the presence of glucose. Its interlayer lithium ion diffusion coefficient is two orders of magnitude higher than that of olivine-type LFP, thus significantly improving the rate performance of the material. S33: Glucose decomposes into amorphous carbon under high-temperature calcination, which uniformly coats the surface of LFP particles with a thickness of 2-5 nm. The material's electrical conductivity ranges from 10... -9 S / cm increased to 10 -3 S / cm, carbon coating treatment not only significantly improves the electrical conductivity of the material, but also effectively inhibits the erosion of LFP particles by the electrolyte, thereby extending the service life of the material.

[0041] In step S32, Li2CO3, FePO4·2H2O and glucose are mixed in a molar ratio of 1:1:1.

[0042] In addition, in step S33, glucose is calcined at high temperature in argon gas at a temperature of 600-700℃.

[0043] Example 1: Lithium iron phosphate regeneration method based on mechanical activation and selective leaching Preprocessing stage: Take 1000g of retired lithium iron phosphate batteries, disassemble them under nitrogen protection, and separate the positive electrode sheets containing LFP, PVDF, and carbon black. The disassembled positive electrode sheet was crushed and then placed in a planetary ball mill with 200g of zirconium oxide beads and 10g of CTAB. The ball milling speed was 400rpm and the ball milling time was 45 minutes to obtain powder with an average particle size of 3μm.

[0044] Leaching separation stage: The pretreated powder was added to 15 L of 1.0 mol / L sulfuric acid solution, followed by 1.5 kg of sodium persulfate. The pH was adjusted to 2.5 using sulfuric acid, and the reaction temperature was maintained at 50 °C. The mixture was stirred for 45 minutes, filtered, and the Li in the leachate was... + Concentration 3.2 g / L, Fe 3+ Concentration <0.01g / L; The leachate is treated with a strongly acidic cation exchange resin to remove Fe. 3+ Then, an excess of saturated sodium carbonate solution was added to obtain 285g of Li2CO3 precipitate with a purity of 99.6%.

[0045] Iron-phosphorus regeneration and LFP synthesis: The leaching residue was added to 10 L of 1.5 mol / L phosphoric acid solution and dissolved at 90 °C for 2 hours. After filtration, the pH was adjusted to 4.5 to obtain 723 g of FePO4·2H2O precipitate. Li2CO3, FePO4·2H2O and glucose were mixed in a molar ratio of 1:1:1, and 10L of deionized water was added. The mixture was reacted in a high-pressure reactor at 230℃ for 8 hours, followed by calcination at 650℃ in argon for 4 hours to obtain regenerated LFP / C material.

[0046] Comparative Example 1: Traditional Hydrometallurgical Process Acid leaching stage: Using 2.0 mol / L sulfuric acid and excess H2O2, with a leaching time of 2 hours, the Li recovery rate was 85% and the Fe leaching rate was 12%.

[0047] Precipitation separation: Three pH adjustments are required, successively adjusting the pH value from 1.5 to 3.0, then to 5.0, and finally solvent extraction. The FePO4 purity is 85%, and the Li2CO3 purity is 95%.

[0048] Solid-state sintering: The recovered Li2CO3, FePO4·2H2O and glucose were mixed in a 1:1:1 molar ratio and then calcined at 650°C for 4 hours in argon to obtain the regenerated LFP / C material.

[0049] Based on this, a 100Ah square aluminum-cased battery cell was prepared using lithium iron phosphate from Example 1 and Comparative Example 1. The process and materials used in the preparation were the same, only the lithium iron phosphate used in the positive electrode was different.

[0050] The prepared battery cells were subjected to electrical performance tests to obtain the first discharge capacity, first discharge efficiency, first charge CV ratio, and AC internal resistance data of Example 1 and Comparative Example 1 after multiple experiments. The results are shown in Table 1.

[0051] Table 1:

[0052] Table 1 and its appendix Figure 5 - Appendix Figure 8 Further analysis revealed that the initial discharge capacity, initial discharge efficiency, initial charge CV ratio, and AC internal resistance of Example 1 were 107.4 Ah, 90.55%, 1.49%, and 0.2894 mΩ, respectively, which were significantly better than those of Comparative Example 1 (103.5 Ah, 88.04%, 3.91%, and 0.2904 mΩ).

[0053] Specifically: Initial discharge capacity: The initial discharge capacity of the cell in Example 1 reached 107.4 Ah, while that of Comparative Example 1 was only 103.5 Ah. This data shows that the lithium iron phosphate material prepared by the method of this invention can release more electrical energy after being assembled into a cell, meeting the demand for high-energy-density batteries in fields such as new energy vehicles and energy storage systems.

[0054] Initial discharge efficiency: The cell in Example 1 achieved an initial discharge efficiency of 90.55%, higher than the 88.04% of Comparative Example 1. This improved discharge efficiency means that more chemical energy is effectively converted into electrical energy during battery discharge, reducing energy loss and improving the overall performance of the battery.

[0055] First charge CV percentage: The CV (voltage fluctuation) ratio of the cell in Example 1 during the first charge was only 1.49%, far lower than the 3.91% of Comparative Example 1. The reduction in CV ratio reflects the enhanced voltage stability during charging, which helps to reduce polarization inside the battery and improve the cycle stability and lifespan of the battery.

[0056] Internal resistance to communication: The cell internal resistance of Example 1 is 0.2894 mΩ, slightly lower than that of Comparative Example 1 (0.2904 mΩ). Although the difference is small, the lower internal resistance means that the battery generates less heat and loses less energy during charging and discharging, which helps to improve the battery's charging and discharging efficiency and overall performance.

[0057] Overall performance improvement: In addition to the advantages of the individual indicators mentioned above, the battery cell of Example 1 also showed a significant improvement in overall performance. This is due to the synergistic effect of mechanical activation and selective leaching in the method of this invention, which effectively solves the problems of low lithium recovery rate, incomplete iron-phosphorus separation, and high energy consumption in the prior art. At the same time, the LiFePO4(OH) intermediate introduced through hydrothermal synthesis significantly improves the cycle life and conductivity of the recycled material, making the performance of the recycled LFP material close to that of the virgin material.

[0058] Economic and environmental benefits: This invention not only improves the performance of recycled lithium iron phosphate materials, but also reduces the amount of chemical reagents used and wastewater discharge through an acid-free leaching system design and wastewater recycling, thereby lowering recycling costs and improving economic efficiency. Furthermore, the widespread application of this method can help alleviate the shortage of strategic metal resources and reduce environmental pollution, thus yielding significant environmental and social benefits.

[0059] In summary, the battery cell prepared by the lithium iron phosphate regeneration method based on mechanical activation and selective leaching in Example 1 is significantly better than that of Comparative Example 1 in terms of key electrical performance indicators such as first discharge capacity, first discharge efficiency, first charge CV ratio, and AC internal resistance.

[0060] These data further validate the effectiveness and superiority of the method of the present invention in improving battery performance, reducing recycling costs, and protecting the environment.

[0061] In addition, the cells of Example 1 and Comparative Example 1 were subjected to 25°C and 45°C 1C / 1C cycle tests, and the test results are shown in Tables 2 and 3.

[0062] Table 2:

[0063] Table 2 and appendix Figure 9 It can be clearly seen that Example 1 is significantly better than Comparative Example 1. After 1400 cycles at 25°C 1C / 1C, the capacity retention rate of Example 1 is still greater than 91.5%, which is close to the level of the original material.

[0064] Specifically: Significantly improved cycle stability: The battery cell of Example 1, after 1400 cycles at 25°C and a charge / discharge rate of 1C / 1C, still retained a capacity of more than 91.5%. This data shows that the lithium iron phosphate material prepared by the method of the present invention can maintain a high capacity during cycling and exhibits excellent cycle stability.

[0065] Compared to Comparative Example 1, Example 1 demonstrates a significant advantage in cycle stability. The battery cell in Comparative Example 1, prepared using a conventional hydrometallurgical process, is likely to exhibit a significantly lower capacity retention rate than that of Example 1 under the same cycle testing conditions. This further demonstrates the effectiveness and superiority of the method of the present invention in improving battery cycle life.

[0066] Table 3

[0067] Table 3 and appendix Figure 10 It can be clearly seen that Example 1 is significantly better than Comparative Example 1. After 1400 cycles at 45°C and 1C / 1C, the capacity retention rate of Example 1 is still greater than 91.5%, which is close to the level of the original material.

[0068] Specifically: The battery cell prepared using the lithium iron phosphate regeneration method based on mechanical activation and selective leaching in Example 1 retained a capacity of over 87% after 987 cycles at a charge / discharge rate of 1C / 1C at a high temperature of 45°C. This data indicates that the method significantly improves the cycle stability of regenerated lithium iron phosphate materials under high temperature conditions and effectively mitigates the performance degradation caused by high temperatures.

[0069] Compared to Comparative Example 1, Example 1 demonstrates a significant advantage in high-temperature cycling stability. When Comparative Example 1 is cycle-tested under the same conditions, its capacity retention is likely to be significantly lower than that of Example 1, indicating the limitations of traditional methods in high-temperature performance. This comparison further verifies the effectiveness and superiority of the method of the present invention in improving the high-temperature cycling performance of batteries.

[0070] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for regenerating lithium iron phosphate based on mechanical activation and selective leaching, characterized in that, Includes the following steps: S1: Mechanical activation pretreatment is performed, and the LFP crystal structure is destroyed by ball milling, reducing the particle size to 2-5 μm and increasing the specific surface area to 15-20 m². 2 / g; S2: Subsequently, selective leaching separation is performed using a sulfuric acid + sodium persulfate system, with the pH value controlled and adjusted to 2-3, thereby allowing Fe... 3+ Hydrolysis is inhibited, PO4 3- with Fe 3+ Combine to form FePO4·2H 2 O precipitation; S3: Next, the precipitated residue is hydrothermally regenerated and synthesized to generate carbon-coated lithium iron phosphate (LFP / C) composite material through hydrothermal reaction.

2. The lithium iron phosphate regeneration method based on mechanical activation and selective leaching according to claim 1, characterized in that, Step S1 includes the following steps: S11: Disassemble retired lithium iron phosphate batteries under nitrogen protection and separate the positive electrode sheet containing LFP, PVDF, and carbon black; S12: Place the disassembled and crushed positive electrode sheet, zirconium oxide beads, and CTAB into a planetary ball mill, set the ball milling speed to 300-500 rpm, and the ball milling time to 30-60 minutes to obtain pretreated powder.

3. The lithium iron phosphate regeneration method based on mechanical activation and selective leaching according to claim 2, characterized in that, The planetary ball milling process reduces the LFP particle size from 20 μm to 2-5 μm and the specific surface area from 5 m² through high-frequency collisions of zirconia beads. 2 / g increased to 15-20m 2 / g, the ball milling media ratio is 5:1-10:

1.

4. The lithium iron phosphate regeneration method based on mechanical activation and selective leaching according to claim 1, characterized in that, Step S2 includes the following steps: S21: Add the pretreated powder to a 1.0 mol / L sulfuric acid solution; S22: Sodium persulfate is added to the solution, where it acts as an oxidizing agent, promoting the dissolution of Li+ through a reaction; the generated oxygen will dissolve Fe. 2+ Oxidized to Fe 3+ This disrupts the LFP lattice structure, causing Li + Preferential dissolution; S23: pH is adjusted to 2-3 using sulfuric acid; Fe 3+ Hydrolysis is inhibited, PO4 3- with Fe 3+ The FePO4·2H2O precipitate is formed, thereby achieving efficient separation of lithium and iron.

5. The lithium iron phosphate regeneration method based on mechanical activation and selective leaching according to claim 4, characterized in that, In step S22, the amount of sodium persulfate added is 1-3 times the molar amount of sulfuric acid, and the reaction temperature is controlled at 40-60℃.

6. The lithium iron phosphate regeneration method based on mechanical activation and selective leaching according to claim 4, characterized in that, The liquid-to-solid ratio of the persulfate to sodium persulfate is 10:1-20:1 mL / g.

7. The lithium iron phosphate regeneration method based on mechanical activation and selective leaching according to claim 1, characterized in that, Step S3 includes the following steps: S31: After washing with water, the leaching precipitate residue is dissolved in 1-2 mol / L phosphoric acid solution at 80-100℃, and the pH is adjusted to 4-5 to redefine FePO4·2H2O, with a purity greater than 99%. S32: In the hydrothermal reaction, Li2CO3 and FePO4·2H2O generate layered LiFePO4(OH) in the presence of glucose. The interlayer lithium ion diffusion coefficient is two orders of magnitude higher than that of olivine-type LFP. S33: Glucose decomposes into amorphous carbon under high-temperature calcination, which uniformly coats the surface of LFP particles with a thickness of 2-5 nm. The material's electrical conductivity ranges from 10... -9 S / cm increased to 10 -3 S / cm.

8. The lithium iron phosphate regeneration method based on mechanical activation and selective leaching according to claim 7, characterized in that, In step S32, Li2CO3, FePO4·2H2O and glucose are mixed in a molar ratio of 1:1:

1.

9. The lithium iron phosphate regeneration method based on mechanical activation and selective leaching according to claim 7, characterized in that, In step S33, glucose is calcined at high temperature in argon gas at a temperature of 600-700℃.

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