A method for repairing and regenerating waste lithium iron phosphate positive electrode material

Abstract

The application discloses a kind of waste lithium iron phosphate positive electrode material's repair regeneration method, the method includes the following steps: the positive pole sheet of waste lithium iron phosphate battery is pretreated, obtains the lithium iron phosphate positive electrode material to be repaired;Mixing lithium iron phosphate positive electrode material to be repaired with titanium source, obtain mixed material;The mixed material is heat treated under inert atmosphere, and the repaired lithium iron phosphate positive electrode material is obtained.Compared with prior art, by introducing titanium source for high-temperature heat treatment, titanium source can promote the complete decomposition of PVDF and capture the HF generated by decomposition, effectively avoid HF and active lithium reaction to generate lithium fluoride, while titanium source can also repair the crystal structure of lithium iron phosphate, its method process flow is simple, no waste water is generated, recycled material gram capacity is high, and cycle performance is excellent, with good industrial practicability and environmental protection benefit.

Description

Technical Field

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

[0002] Lithium iron phosphate (LFP) battery cells possess excellent cycle performance and safety characteristics, making them widely used in energy storage and electric vehicles. However, the production process of LFP battery cells generates a large amount of defective slurry, electrode sheets, and cores. Directly discarding these materials would pollute the environment and waste resources.

[0003] Currently, the industry's process for handling waste materials involves first crushing and then sorting them, separating the current collector (metals such as copper and aluminum), separator, positive electrode material, and negative electrode material. The positive electrode material contains binders such as polyvinylidene fluoride (PVDF) and conductive agents, requiring processing using hydrometallurgy, pyrometallurgy, or a combination of hydrometallurgy and pyrometallurgy.

[0004] However, existing technologies have the following problems: Hydrometallurgical wastewater contains many salts and a certain amount of organic matter, making aqueous solution treatment difficult, posing a significant environmental burden, and the process is complex and costly. In pyrometallurgical processes, the binder PVDF decomposes at high temperatures to produce hydrofluoric acid (HF). HF reacts with active lithium in the cathode material to form lithium fluoride, resulting in a lower specific capacity of the repaired cathode material. Furthermore, PVDF cannot be completely decomposed during pyrometallurgical processes; undecomposed PVDF residue affects the electronic conductivity of lithium iron phosphate materials, leading to increased cell impedance. Simultaneously, incompletely decomposed PVDF also affects material processing performance, resulting in a low solids content in the slurry during preparation, making it difficult to meet the process requirements for subsequent electrode fabrication.

[0005] Therefore, developing a lithium iron phosphate recovery method that can effectively solve the problems of incomplete PVDF decomposition and hydrofluoric acid production during decomposition has significant industrial application value and environmental significance. Summary of the Invention

[0006] The purpose of this invention is to provide a method for repairing and regenerating waste lithium iron phosphate cathode materials, which solves the problems of incomplete PVDF decomposition and the generation of hydrofluoric acid during decomposition. This method can not only ensure the full deactivation or decomposition of PVDF, but also avoid the reaction between the hydrofluoric acid generated during PVDF decomposition and the active lithium in lithium iron phosphate, thus ensuring the specific capacity and processing performance of the recycled material.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for repairing and regenerating waste lithium iron phosphate cathode materials, comprising the following steps: Pre-treatment of the positive electrode sheet of waste lithium iron phosphate batteries yields lithium iron phosphate positive electrode material to be repaired. The lithium iron phosphate cathode material to be repaired is mixed with a titanium source to obtain a mixture. The mixture was heat-treated under an inert atmosphere to obtain the repaired lithium iron phosphate cathode material.

[0008] Preferably, the pretreatment step in step (1) includes: screening the positive electrode sheet of the waste lithium iron phosphate battery to remove foreign matter; And / or, the pretreatment step in step (1) includes: crushing and screening the positive electrode sheet of the waste lithium iron phosphate battery to obtain the lithium iron phosphate positive electrode material to be repaired.

[0009] Preferably, the foreign object in step (1) includes at least one of tape, metal, and negative electrode sheet.

[0010] Preferably, the mesh size of the sieve used in step (1) is 100 to 400 mesh.

[0011] Preferably, the titanium source in step (2) is selected from at least one of Ti(OH)4, TiO2, Ti2O3, TiO, TiCl4, TiBr4, and TiCl3.

[0012] Preferably, the amount of titanium source added in step (2) is 0.2% to 2% of the mass of the lithium iron phosphate cathode material to be repaired.

[0013] Preferably, the temperature of the heat treatment in step (3) is 300℃~850℃.

[0014] Preferably, the heat treatment time in step (3) is 1h to 24h.

[0015] Preferably, the inert atmosphere in step (3) is selected from at least one of nitrogen, argon and helium, and the gas flow rate is 0.5 L / min to 10 L / min.

[0016] Secondly, the present invention provides a lithium iron phosphate cathode material obtained by the above-described repair and regeneration method.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: The addition of a titanium source in the lithium iron phosphate repair and regeneration method provided by this invention can ensure the full deactivation of PVDF in the lithium iron phosphate cathode material to be repaired, and avoid residual PVDF affecting the solid content of the homogenate and reducing the electronic conductivity of the material.

[0018] The lithium iron phosphate repair and regeneration method provided by this invention can avoid the reaction between hydrofluoric acid generated during PVDF decomposition and lithium iron phosphate cathode material, which would reduce the active lithium content of lithium iron phosphate cathode material and affect the specific capacity of cathode material.

[0019] The lithium iron phosphate repair and regeneration method provided by this invention can also increase the metal element doping ratio, improve the lithium ion migration rate of the repaired lithium iron phosphate cathode material, and thus improve the rate performance and energy efficiency of the cathode material. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is an electron microscope image of the regenerated waste lithium iron phosphate in this invention; Figure 2 This is a comparison chart of the 0.1C charge / discharge curves of Embodiment 2 and Comparative Example 5 of the present invention; Figure 3 This is a comparison chart of the 1C charge / discharge curves of Example 2 and Comparative Example 5 of the present invention. Detailed Implementation

[0022] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0023] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0024] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0025] It should be understood that in various embodiments of the present invention, the order of the above-mentioned processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0026] According to a first aspect of the present invention, the present invention provides a method for repairing and regenerating waste lithium iron phosphate cathode materials, comprising the following steps: Pre-treatment of the positive electrode sheet of waste lithium iron phosphate batteries yields lithium iron phosphate positive electrode material to be repaired. The lithium iron phosphate cathode material to be repaired is mixed with a titanium source to obtain a mixture. The mixture was heat-treated under an inert atmosphere to obtain the repaired lithium iron phosphate cathode material.

[0027] In some embodiments of the present invention, the pretreatment step in step (1) includes: screening the positive electrode sheet of the waste lithium iron phosphate battery to remove foreign matter; And / or, the pretreatment step in step (1) includes: crushing and screening the positive electrode sheet of the waste lithium iron phosphate battery to obtain the lithium iron phosphate positive electrode material to be repaired.

[0028] In some embodiments of the present invention, the foreign object in step (1) includes at least one of tape, metal, and negative electrode sheet.

[0029] In some embodiments of the present invention, the mesh size of the sieve used in step (1) is 100 to 400 mesh. For example, the mesh size of the sieve can be 100 mesh, 200 mesh, 300 mesh, 400 mesh, etc.

[0030] The reason for setting the sieve mesh size to 100-400 mesh is twofold: firstly, it effectively removes large metal impurities that failed to dissociate during the crushing process, as well as incompletely crushed electrode fragments, ensuring that the purity of the resulting lithium iron phosphate cathode material meets the requirements of subsequent high-temperature heat treatment; secondly, this mesh size range ensures a uniform particle size distribution of lithium iron phosphate particles, preventing excessive sintering or agglomeration of overly fine powder during high-temperature heat treatment, while also preventing insufficient heat treatment and uneven repair effects caused by overly coarse particles. When the mesh size is below 100 mesh, a large number of large impurities will be mixed into the undersize material, affecting the purity and electrochemical performance of the repaired material; when the mesh size is above 400 mesh, the sieving efficiency decreases significantly, and overly fine powder is prone to particle growth or abnormal sintering at high temperatures, which is detrimental to the stability of material properties.

[0031] In some embodiments of the present invention, the titanium source in step (2) is selected from at least one of Ti(OH)4, TiO2, Ti2O3, TiO, TiCl4, TiBr4, and TiCl3.

[0032] Among them, Ti(OH)4 showed the best effect. Ti(OH)4 contains a large number of surface -OH groups, which readily undergo an exothermic fluorination reaction with the HF removed from PVDF at high temperatures. Ti(OH)4+4HF → TiF4+ 4H2O, Ti(OH)4+6HF → H2TiF6+ 4H2O; The reaction consumes HF, thereby promoting the de-HF decomposition of PVDF, lowering the onset temperature of the decomposition reaction, and accelerating the weight loss rate. Moreover, this process is exothermic, further accelerating thermal decomposition and forming an autocatalytic cycle.

[0033] In some embodiments of the present invention, the amount of titanium source added in step (2) is 0.2% to 2% of the mass of the lithium iron phosphate cathode material to be repaired. For example, the amount of titanium source added can be 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, etc.

[0034] The titanium source addition amount is set to 0.2%–2% of the mass of the lithium iron phosphate cathode material to be repaired because: when the titanium source addition amount is less than 0.2%, it is difficult for the titanium source to form a uniform coating layer on the surface of lithium iron phosphate particles or achieve sufficient bulk doping during high-temperature heat treatment. This results in insufficient capture capacity for HF generated by PVDF decomposition, and some HF will still react with active lithium to form lithium fluoride, leading to a minimal increase in the specific capacity of the repaired material. Simultaneously, too low a titanium content cannot effectively repair the lattice defects generated in lithium iron phosphate during long-term cycling, resulting in limited improvement in the material's rate performance and cycle stability. When the titanium source addition amount is higher than 2%, excessive titanium source may form too much titanium compound second phase at high temperatures. These inactive substances will dilute the effective active components of lithium iron phosphate, reducing the specific capacity of the material. Furthermore, the introduction of excessive titanium may also change the surface chemical state of lithium iron phosphate, increasing electrode polarization and adversely affecting the electrochemical performance of the material.

[0035] In some embodiments of the present invention, the heat treatment temperature in step (3) is 300°C to 850°C. For example, the heat treatment temperature can be 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, etc.

[0036] The heat treatment temperature is set between 300℃ and 850℃ because: Below 300℃, PVDF only partially softens or undergoes preliminary decomposition, making complete carbonization and removal difficult. Residual PVDF coats the surface of lithium iron phosphate particles, hindering electron conduction and affecting subsequent pulping and processing performance. Simultaneously, titanium powder exhibits low activity at this temperature, failing to effectively react with the HF produced by PVDF decomposition, and hindering the repair of lattice defects in lithium iron phosphate. Above 850℃, irreversible phase transitions or abnormal grain growth may occur in lithium iron phosphate materials, leading to a significant decrease in electrochemical performance. Furthermore, excessively high temperatures increase energy consumption and may cause excessive reaction between titanium powder and lithium iron phosphate, generating non-electrochemically active titanium-iron compounds, which conversely reduces the specific capacity of the recycled material.

[0037] In some embodiments of the present invention, the heat treatment time in step (3) is 1h to 24h. For example, the heat treatment time can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc.

[0038] The heat treatment time is set to 1 to 24 hours because: when the heat treatment time is less than 1 hour, the PVDF decomposition reaction has not been fully carried out, and residual PVDF will still coat the lithium iron phosphate particles, affecting the electronic conductivity of the material; at the same time, the reaction between the titanium source and HF and the diffusion doping of titanium into the lithium iron phosphate lattice both require sufficient time to reach equilibrium. Too short a time will lead to insufficient repair effect, and the improvement in specific capacity and cycle performance of the recycled material will be limited. When the heat treatment time exceeds 24 hours, although the PVDF decomposition and titanium diffusion are more thorough, the excessively long holding time will lead to excessive growth of lithium iron phosphate grains, a decrease in specific surface area, and an increase in lithium-ion diffusion paths, which is detrimental to rate performance; at the same time, long heat treatment will significantly increase energy consumption and production costs, reduce production efficiency, and is not conducive to large-scale industrial applications.

[0039] In some embodiments of the present invention, the inert atmosphere in step (3) is selected from at least one of nitrogen, argon and helium, and the gas flow rate is 0.5 L / min to 10 L / min. For example, the gas flow rate can be 0.5 L / min, 1 L / min, 2 L / min, 4 L / min, 6 L / min, 8 L / min, 10 L / min, etc.

[0040] According to a second aspect of the present invention, the present invention provides a lithium iron phosphate cathode material obtained by the above-described repair and regeneration method.

[0041] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. Example 1

[0042] Repair and regeneration of waste lithium iron phosphate cathode materials 1) Screen the positive electrode sheets of waste lithium iron phosphate batteries to remove foreign objects such as tape, metal, and negative electrode sheets. Then crush and screen the positive electrode sheets of waste lithium iron phosphate batteries with a screen mesh of 300 mesh to obtain waste lithium iron phosphate positive electrode material powder. 2) Take 50g of waste lithium iron phosphate cathode material powder and mix it with 0.2g of Ti(OH)4 to obtain a mixture. 3) Place the mixture in a heating furnace and heat it to 350°C at 8°C / min under a nitrogen atmosphere, and hold it at that temperature for 3 hours. After cooling in the furnace, crush, screen, and demagnetize, the repaired lithium iron phosphate cathode material is obtained.

[0043] Preparation of button cells 1) The repaired lithium iron phosphate cathode material, conductive agent, and polyvinylidene fluoride were mixed in a mass ratio of 9:5:5. NMP was added and stirred to obtain a cathode slurry with a solid content of 62%. 2) The positive electrode slurry is uniformly coated on aluminum foil and vacuum baked for 12 hours to obtain a positive electrode sheet with a film resistance of 0.8Ω; the positive electrode sheet is then stamped and assembled with the separator and lithium sheet into a button cell. Example 2

[0044] Unlike Example 1, step 3) of the repair and regeneration of waste lithium iron phosphate cathode material is heated to 750°C; the solid content of the slurry in the preparation of the coin cell is measured to be 65%, and the film resistance is measured to be 0.4Ω. The remaining steps are the same as in Example 1. Example 3

[0045] Unlike Example 1, in step 2) of the repair and regeneration of waste lithium iron phosphate cathode material, 0.3g of Ti(OH)4 was added; the measured solid content of the slurry in the preparation of the coin cell was 62.7%, and the measured membrane resistance was 0.65Ω. The remaining steps were the same as in Example 1. Example 4

[0046] Unlike Example 1, in step 2) of the repair and regeneration of waste lithium iron phosphate cathode material, 0.6g of Ti(OH)4 was added; the measured solid content of the slurry in the preparation of the coin cell was 63.8%, and the measured membrane resistance was 0.62Ω. The remaining steps were the same as in Example 1. Example 5

[0047] Unlike Example 1, in step 2) of the repair and regeneration of waste lithium iron phosphate cathode material, 0.9g of Ti(OH)4 was added; the measured solid content of the slurry in the preparation of the coin cell was 63.9%, and the measured membrane resistance was 0.6Ω. The remaining steps were the same as in Example 1. Example 6

[0048] Unlike Example 1, in step 2) of the repair and regeneration of waste lithium iron phosphate cathode material, Ti(OH)4 was replaced with TiO2; the measured solid content of the slurry in the preparation of the coin cell was 61.4%, and the measured membrane resistance was 0.85Ω. The remaining steps were the same as in Example 1. Example 7

[0049] Unlike Example 1, in step 3) of the repair and regeneration of waste lithium iron phosphate cathode material, Ti(OH)4 was replaced with TiCl4; the measured solid content of the slurry in the preparation of the coin cell was 61.2%, and the measured membrane resistance was 0.87Ω. The remaining steps were the same as in Example 1. Example 8

[0050] Unlike Example 1, the heat preservation time in step 3) of the repair and regeneration of waste lithium iron phosphate cathode material is 6 hours; the measured solid content of the slurry in the preparation of the coin cell is 63.1%, and the measured membrane resistance is 0.69Ω. The remaining steps are the same as in Example 1.

[0051] Comparative Example 1 Unlike Example 1, step 3) of the repair and regeneration of waste lithium iron phosphate cathode material is heated to 120°C; the measured solid content of the slurry in the preparation of the coin cell is 51%, and the measured membrane resistance is 2.2Ω. The remaining steps are the same as in Example 1.

[0052] Comparative Example 2 Unlike Example 1, in step 2) of the repair and regeneration of waste lithium iron phosphate cathode material, 0.1g of Ti(OH)4 was added; the measured solid content of the slurry in the preparation of the coin cell was 59%, and the measured membrane resistance was 0.93Ω. The remaining steps were the same as in Example 1.

[0053] Comparative Example 3 Unlike Example 1, in step 2) of the repair and regeneration of waste lithium iron phosphate cathode material, 1.2g of Ti(OH)4 was added; the measured solid content of the slurry in the preparation of the coin cell was 63.9%, and the measured membrane resistance was 0.59Ω. The remaining steps were the same as in Example 1.

[0054] Comparative Example 4 Unlike Example 1, the heat preservation time in step 3) of the repair and regeneration of waste lithium iron phosphate cathode material is 30 hours; the measured solid content of the slurry in the preparation of the coin cell is 62.9%, and the measured membrane resistance is 0.68Ω. The remaining steps are the same as in Example 1.

[0055] Comparative Example 5 Unlike Example 1, Ti(OH)4 is not added in step 2) of the repair and regeneration of waste lithium iron phosphate cathode material; the measured film resistance in the preparation of the coin cell is 1.5Ω. The remaining steps are the same as in Example 1.

[0056] Comparative Example 6 Unlike Example 1, carbon powder was added in step 2) of the repair and regeneration of waste lithium iron phosphate cathode material; the measured solid content of the slurry in the preparation of the coin cell was 50.4%, and the measured membrane resistance was 1.45Ω. The remaining steps were the same as in Example 1.

[0057] Comparative Example 7 Take 50g of the same waste lithium iron phosphate cathode black powder as in Example 1, and after preliminary screening and crushing, obtain lithium iron phosphate black powder. Then, recover lithium iron phosphate using the acid leaching-precipitation method.

[0058] Table 1 From Table 1, we can obtain: As shown in Example 1, the addition of Ti(OH)4 to waste lithium iron phosphate cathode black powder at 350°C can promote PVDF failure. Simultaneously, Ti(OH)4 can protect lithium iron phosphate, preventing the HF generated from PVDF decomposition from consuming the active lithium in the material. However, at this temperature, Ti cannot enter the lithium iron phosphate lattice. Due to PVDF failure, the slurry solid content is increased, the membrane resistance is reduced, and the coin cell charging capacity is significantly improved.

[0059] As shown in Example 2, the addition of Ti(OH)4 to waste lithium iron phosphate cathode black powder at 750℃ not only promotes PVDF failure and protects the active lithium in the material, but also allows Ti to enter the lithium iron phosphate lattice at this temperature, achieving a doping effect. Compared to Example 1, Ti doping improves the kinetic performance of the lithium iron phosphate material, with a significant increase in 1C discharge specific capacity.

[0060] Examples 3-5 show that increasing the amount of Ti(OH)4 promotes PVDF failure, thereby increasing the slurry solids content and reducing membrane resistance. However, when the amount exceeds 0.6g, there is no significant improvement in slurry solids content and membrane resistance, indicating that the upper limit of Ti(OH)4 dosage in this process is 0.6g.

[0061] As shown in Examples 6-7, TiO2 and TiCl4 can also react with HF generated during the modification process, thereby promoting the failure of PVDF. However, a comparison of their effects with Ti(OH)4 shows that Ti(OH)4 is superior to TiO2, while TiO2 is slightly superior to TiCl4.

[0062] As demonstrated in Example 8, increasing the thermal modification time allows for more complete failure of PVDF in the recycled material, thereby increasing the solid content and reducing the film resistance. However, at 350°C, Ti cannot be effectively doped into the lithium iron phosphate lattice, thus failing to improve the coin cell performance of the material.

[0063] Compared with Example 1, the waste lithium iron phosphate cathode black powder in Comparative Example 1 did not fail in PVDF at 120°C without the addition of Ti(OH)4. The presence of PVDF resulted in a severely low solid content in the slurry, while the electrode film resistance was high, leading to a reduction in the coin cell charge / discharge capacity.

[0064] Compared to Examples 1 / 3 / 4 / 5, in Comparative Examples 2-3, increasing the amount of Ti(OH)4 promoted PVDF failure, thereby increasing the slurry solids content and reducing membrane resistance. However, when the amount exceeded 0.6g, there was no significant improvement in the slurry solids content and membrane resistance, indicating that the upper limit of Ti(OH)4 usage in this process is 0.6g.

[0065] Compared to Examples 1 / 8, in Comparative Example 4, further increasing the thermal modification time failed to completely deactivate the PVDF in the recycled material, thus failing to increase the solid content and reduce the film resistance. However, at 350°C, Ti could not be effectively doped into the lithium iron phosphate lattice, thus failing to improve the coin cell performance of the material.

[0066] Compared with Example 1, the waste lithium iron phosphate cathode black powder of Comparative Example 5 showed partial failure of PVDF at 350°C without the addition of Ti(OH)4, resulting in increased film resistance and significantly reduced coin charge / discharge capacity.

[0067] Compared to Example 1, Comparative Example 6 added toner, but the addition of toner did not cause PVDF to fail. Simultaneously, the addition of toner increased the amount of high specific surface area material in the slurry system, further reducing the slurry solids content and failing to improve the material's tack capacity.

[0068] Compared with Example 1, Comparative Example 7 used the acid leaching-precipitation method to recover lithium iron phosphate, and the resulting lithium iron phosphate material had the highest specific capacity.

[0069] In summary, the lithium iron phosphate cathode material repair and regeneration method provided by this invention effectively solves the problem of reduced specific capacity caused by the decomposition of PVDF to produce lithium fluoride in the prior art by introducing a titanium source for high-temperature heat treatment. The repaired and regenerated material has excellent specific capacity and cycle stability, and the process is simple, environmentally friendly, and suitable for industrial applications.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for repairing and regenerating waste lithium iron phosphate cathode materials, characterized in that, Includes the following steps: Pre-treatment of the positive electrode sheet of waste lithium iron phosphate batteries yields lithium iron phosphate positive electrode material to be repaired. The lithium iron phosphate cathode material to be repaired is mixed with a titanium source to obtain a mixture. The mixture was heat-treated under an inert atmosphere to obtain the repaired lithium iron phosphate cathode material.

2. The method for repairing and regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, The pretreatment step in step (1) includes: screening the positive electrode sheet of the waste lithium iron phosphate battery to remove foreign matter; And / or, the pretreatment step in step (1) includes: crushing and screening the positive electrode sheet of the waste lithium iron phosphate battery to obtain the lithium iron phosphate positive electrode material to be repaired.

3. The method for repairing and regenerating waste lithium iron phosphate cathode materials according to claim 2, characterized in that, The foreign object mentioned in step (1) includes at least one of tape, metal, and negative electrode sheet.

4. The method for repairing and regenerating waste lithium iron phosphate cathode materials according to claim 2, characterized in that, The sieve mesh number for sieving in step (1) is 100 mesh to 400 mesh.

5. The method for repairing and regenerating waste lithium iron phosphate cathode materials according to claim 1, characterized in that, The titanium source mentioned in step (2) is selected from at least one of Ti(OH)4, TiO2, Ti2O3, TiO, TiCl4, TiBr4, and TiCl3.

6. The method for repairing and regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, The amount of titanium source added in step (2) is 0.2% to 2% of the mass of the lithium iron phosphate cathode material to be repaired.

7. The method for repairing and regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, The heat treatment temperature in step (3) is 300℃~850℃.

8. The method for repairing and regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, The heat treatment time in step (3) is 1h to 24h.

9. The method for repairing and regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, The inert atmosphere mentioned in step (3) is selected from at least one of nitrogen, argon and helium, and the gas flow rate is 0.5L / min to 10L / min.

10. A lithium iron phosphate cathode material obtained by the repair and regeneration method according to any one of claims 1 to 9.

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