Method for recycling materials of waste and old lithium iron phosphate battery

Abstract

The application belongs to the technical field of secondary battery material regeneration, and more particularly relates to a method for regenerating materials of waste lithium iron phosphate batteries. The specific regeneration steps comprise: disassembling and separating to obtain positive electrode sheets, and then drying to remove residual electrolyte in the positive electrode sheets; laying the positive electrode sheets in a reactor, preheating to 100 DEG C, then introducing water vapor into the reactor, under the condition of a pressure of 0.3-0.5 MPa, pressure maintaining for 1-3 h, then releasing the pressure to normal pressure, discharging, separating and removing the positive current collector, and collecting the positive active material layer; crushing the positive active material layer to obtain positive active material layer fragments; taking the positive active material layer fragments, mixing lithium nitrate, ferrous oxalate and biomass sugar uniformly, heating and warming in an inert atmosphere, after heat preservation and melting reaction, cooling, water washing, drying, heating and warming in an inert atmosphere, after heat preservation and calcination, cooling and discharging, the regeneration of materials of waste lithium iron phosphate batteries is completed.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery material regeneration technology. More specifically, it relates to a method for regenerating materials from waste lithium iron phosphate batteries. Background Technology

[0002] A large amount of battery waste is generated during the processing, testing, and use of lithium-ion batteries. Among these, the recycling of battery cathode materials is particularly valuable. For batteries using lithium iron phosphate as the cathode material, the physical structure of lithium iron phosphate cathode material is stable due to its olivine structure. However, in actual use, it needs to be treated with carbon coating or doping. During processing, testing, or use, these coatings or dopants may be damaged. Therefore, after recycling, it still needs to be regenerated to ensure that the lithium iron phosphate cathode material obtains the ideal electrochemical performance. Summary of the Invention

[0003] The technical problem to be solved by this invention is: how to achieve ideal electrochemical performance in the process of recycling and regenerating the positive electrode active material of lithium iron phosphate batteries. This invention provides a method for regenerating materials from waste lithium iron phosphate batteries.

[0004] The purpose of this invention is to provide a method for regenerating materials from waste lithium iron phosphate batteries.

[0005] The above-mentioned objective of this invention is achieved through the following technical solution:

[0006] A method for regenerating materials from spent lithium iron phosphate batteries, the specific regeneration steps of which include:

[0007] The positive electrode sheet is disassembled and separated, and then dried to remove the residual electrolyte solvent in the positive electrode sheet, so that the fluorinated lithium salt in the electrolyte can be adsorbed into the pores of the positive electrode sheet.

[0008] The positive electrode sheet includes a positive current collector and a positive active material layer coated on the surface of the positive current collector. The positive active material layer includes a positive active material, which is lithium iron phosphate.

[0009] The positive electrode sheet is laid in the reactor and preheated to 100°C. Water vapor is introduced into the reactor and pressure is maintained at 0.3-0.5 MPa for 1-3 hours. The pressure is then released to atmospheric pressure, the material is discharged, the positive electrode current collector is separated and removed, and the positive electrode active material layer is collected.

[0010] The positive electrode active material layer is crushed to obtain fragments of the positive electrode active material layer;

[0011] By weight, take 100-110 parts of the positive electrode active material layer fragments, 20-25 parts of lithium nitrate, 3-5 parts of ferrous oxalate, and 5-8 parts of biomass sugar. Mix them evenly and heat them in an inert atmosphere to 300-310℃. After holding the temperature for 4-8 hours to melt and react, cool, wash with water, and dry. Then, heat them in an inert atmosphere to 660-680℃ and calcine them for 4-8 hours. After cooling, discharge the material to complete the regeneration of materials from waste lithium iron phosphate batteries.

[0012] The beneficial effects of the above technical solution are as follows:

[0013] First, the recovered positive electrode sheet is dried. During this process, the electrolyte absorbed in the pores of the positive electrode sheet will begin to evaporate. At this time, the solvent in the electrolyte will mainly evaporate, while the fluorinated lithium salt in the electrolyte will remain in the pores of the positive electrode sheet.

[0014] Subsequently, a steam pressurization reaction is adopted, and the steam will continuously diffuse and permeate into the pores of the positive electrode. During this process, the residual fluorinated lithium salt in the pores can react with the steam to produce HF. It should be noted that, due to the temperature and pressure in the reactor, HF and steam diffuse and permeate into the pores of the positive electrode together under steam pressure, thereby effectively and fully destroying the interface between the positive active material layer on the surface of the positive electrode and the positive current collector (aluminum foil). During the depressurization to atmospheric pressure, the rapid decrease in pressure causes the internal HF and steam to leak out rapidly. This process can further facilitate the peeling of the interface between the positive active material layer and the positive current collector.

[0015] During the subsequent regeneration process, thanks to the pores formed by the diffusion and permeation of water vapor and HF gas, the molten material will diffuse and permeate into the internal pores, thereby achieving sufficient and uniform replenishment of lithium and iron elements to the positive electrode active material; thus enabling the electrochemical performance of the regenerated lithium iron phosphate positive electrode material to achieve ideal results.

[0016] Furthermore, the specific regeneration steps also include:

[0017] The positive electrode active material layer fragments and the solvent N-methylpyrrolidone are mixed and stirred to form a slurry. The resulting slurry is then spray-granulated to obtain active material particles.

[0018] By weight, take 100-110 parts of active material particles, 15-20 parts of lithium nitrate, 3-5 parts of ferrous oxalate, and 5-8 parts of biomass sugar. Mix them evenly and heat them in an inert atmosphere to 300-310℃. After holding the temperature for melting reaction for 4-8 hours, cool, wash with water, and dry. Then, heat them in an inert atmosphere to 660-680℃ and hold the temperature for calcination for 4-8 hours. After cooling, discharge the material to complete the regeneration of materials from waste lithium iron phosphate batteries.

[0019] Furthermore, the specific regeneration steps also include:

[0020] The positive electrode active material layer fragments and the solvent N-methylpyrrolidone are mixed and stirred to form a slurry. The resulting slurry is then spray-granulated, and active material particles with a D50 of 80-120 μm are screened out.

[0021] In the above technical solution, the positive electrode active material layer fragments and N-methylpyrrolidone are further mixed. In this process, N-methylpyrrolidone can redissolve the binder (PVDF) in the positive electrode active material layer fragments to form a slurry. During the spray drying process, the PVDF binds the positive electrode active material into spherical particles, which is beneficial to increasing the contact area with the molten salt in the subsequent regeneration process. Furthermore, the pores formed by the diffusion of the solvent N-methylpyrrolidone during the spray granulation process not only reduce the density of the active material particles, making them easier to suspend in the molten salt system and avoiding sedimentation, but also provide a diffusion path for the molten salt, making the molten salt treatment process thorough and uniform.

[0022] Furthermore, the biomass sugar is selected from any one of glucose, fructose, galactose, lactose, and sucrose.

[0023] Furthermore, the specific preparation steps also include:

[0024] By weight, take 100-110 parts of the positive electrode active material layer fragments, 20-25 parts of lithium nitrate, 3-5 parts of ferrous oxalate, and 5-8 parts of biomass sugar. Mix them evenly and then slowly heat them to 300-310℃ at a rate of 0.3-0.5℃ / min in an inert atmosphere. After holding the temperature for 4-8 hours to melt and react, cool, wash with water, and dry. Then, heat them to 660-680℃ in an inert atmosphere and calcine them for 4-8 hours. After cooling, discharge the material to complete the regeneration of materials from waste lithium iron phosphate batteries.

[0025] Furthermore, the specific preparation steps also include:

[0026] By weight, take 100-110 parts of the positive electrode active material layer fragments, 20-25 parts of lithium nitrate, 3-5 parts of ferrous oxalate, and 5-8 parts of biomass sugar. Mix them evenly and then slowly heat them to 300-310℃ at a rate of 0.3-0.5℃ / min in an inert atmosphere. After holding the temperature for 4-8 hours to melt and react, cool, wash with water, and dry. Then, in an inert atmosphere, rapidly heat them to 660-680℃ at a rate of 3-5℃ / min and calcine them for 4-8 hours. After cooling, discharge the material to complete the regeneration of materials from waste lithium iron phosphate batteries.

[0027] The above technical solution further controls the heating rate during the melting process by using a lower heating rate for slow heating, thereby controlling the melting process of the molten salt. This is mainly because the thermal conductivity of the molten salt is different from that of the positive electrode active material particles. During the melting process, heat transfer relies on the internal heat transfer between the two. A slow heating rate can make the overall temperature of the system relatively uniform, avoiding local overheating, which would lead to uneven reaction and inconsistent product areas in the final processed product, which is undesirable.

[0028] Furthermore, the fluorinated lithium salt is selected from any one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalate borate.

[0029] Furthermore, the mass of the fluorinated lithium salt accounts for 5-12% of the total mass of the electrolyte. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0031] Unless otherwise specified, all reagents and materials used in the following examples are commercially available. Example 1

[0032] The square aluminum-cased battery with lithium iron phosphate as the main cathode material is used as the recycling target, and the battery is obtained by disassembling the battery pack;

[0033] The battery is fully discharged until the cutoff voltage is 2.5V, which is considered to put the battery into an empty state to ensure safety during disassembly and recycling.

[0034] The positive electrode is disassembled and separated. At this time, the positive electrode is still wetted with electrolyte. In this state, it is then dried in an oven at 80°C to constant weight to remove the residual electrolyte solvent in the positive electrode. Since the electrolyte consists of solvent and fluorinated lithium salt dissolved in it, after evaporating and removing the solvent, the fluorinated lithium salt in the electrolyte can be adsorbed into the pores of the positive electrode.

[0035] The positive electrode sheet includes a positive current collector and a positive active material layer coated on the surface of the positive current collector. The positive active material layer includes a positive active material, which is lithium iron phosphate.

[0036] The fluorinated lithium salt is selected from lithium hexafluorophosphate;

[0037] The fluorinated lithium salt accounts for 5% of the total mass of the electrolyte;

[0038] The positive electrode sheet is laid in the reactor. A hydrothermal reactor is used as the reactor. After preheating it to 100°C, superheated steam is introduced into the reactor. Under the condition of 0.3MPa, the pressure is maintained for 1 hour. After depressurization to atmospheric pressure, the material is discharged. At this time, the positive active material layer on the surface of the positive electrode sheet has been peeled off from the positive current collector. The positive current collector is separated and removed, and the positive active material layer is collected.

[0039] The positive electrode active material layer is crushed to obtain fragments of the positive electrode active material layer;

[0040] The positive electrode active material layer fragments and solvent N-methylpyrrolidone were mixed at a mass ratio of 1:8, stirred to form a slurry, and then the resulting slurry was pumped into a spray dryer for spray granulation, and active material particles with a D50 of 80 μm were screened out.

[0041] By weight, take 100 parts of active material particles, 20 parts of lithium nitrate, 3 parts of ferrous oxalate, and 5 parts of biomass sugar. Mix them evenly and slowly heat them to 300°C at a rate of 0.3°C / min in an inert atmosphere. After holding the temperature for 4 hours to melt and react, cool, wash with water, and dry. Then, heat them rapidly to 660°C at a rate of 3°C / min in an inert atmosphere and calcine them for 4 hours. After cooling, discharge the material to complete the regeneration of materials from waste lithium iron phosphate batteries.

[0042] The biomass sugar is selected from glucose. Example 2

[0043] The square aluminum-cased battery with lithium iron phosphate as the main cathode material is used as the recycling target, and the battery is obtained by disassembling the battery pack;

[0044] The battery is fully discharged until the cutoff voltage is 2.5V, which is considered to put the battery into an empty state to ensure safety during disassembly and recycling.

[0045] The positive electrode is disassembled and separated. At this time, the positive electrode is still wetted with electrolyte. In this state, it is then dried in an oven at 80°C to constant weight to remove the residual electrolyte solvent in the positive electrode. Since the electrolyte consists of solvent and fluorinated lithium salt dissolved in it, after evaporating and removing the solvent, the fluorinated lithium salt in the electrolyte can be adsorbed into the pores of the positive electrode.

[0046] The positive electrode sheet includes a positive current collector and a positive active material layer coated on the surface of the positive current collector. The positive active material layer includes a positive active material, which is lithium iron phosphate.

[0047] The fluorinated lithium salt is selected from lithium tetrafluoroborate;

[0048] The fluorinated lithium salt accounts for 8% of the total mass of the electrolyte;

[0049] The positive electrode sheet is laid in the reactor. A hydrothermal reactor is used as the reactor. After preheating it to 100°C, superheated steam is introduced into the reactor. Under the condition of 0.4MPa, the pressure is maintained for 2 hours. After depressurization to atmospheric pressure, the material is discharged. At this time, the positive active material layer on the surface of the positive electrode sheet has been peeled off from the positive current collector. The positive current collector is separated and removed, and the positive active material layer is collected.

[0050] The positive electrode active material layer is crushed to obtain fragments of the positive electrode active material layer;

[0051] The positive electrode active material layer fragments and solvent N-methylpyrrolidone were mixed at a mass ratio of 1:8, stirred to form a slurry, and then the resulting slurry was pumped into a spray dryer for spray granulation, and active material particles with a D50 of 100 μm were screened out.

[0052] By weight, take 105 parts of active material particles, 22 parts of lithium nitrate, 4 parts of ferrous oxalate, and 6 parts of biomass sugar. Mix them evenly and then slowly heat them to 305°C at a rate of 0.4°C / min in an inert atmosphere. After holding the temperature for 6 hours to melt and react, cool, wash with water, and dry. Then, rapidly heat them to 670°C at a rate of 4°C / min in an inert atmosphere and calcine them for 6 hours. After cooling, discharge the material to complete the regeneration of materials from waste lithium iron phosphate batteries.

[0053] The biomass sugar is selected from sucrose. Example 3

[0054] The square aluminum-cased battery with lithium iron phosphate as the main cathode material is used as the recycling target, and the battery is obtained by disassembling the battery pack;

[0055] The battery is fully discharged until the cutoff voltage is 2.5V, which is considered to put the battery into an empty state to ensure safety during disassembly and recycling.

[0056] The positive electrode is disassembled and separated. At this time, the positive electrode is still wetted with electrolyte. In this state, it is then dried in an oven at 80°C to constant weight to remove the residual electrolyte solvent in the positive electrode. Since the electrolyte consists of solvent and fluorinated lithium salt dissolved in it, after evaporating and removing the solvent, the fluorinated lithium salt in the electrolyte can be adsorbed into the pores of the positive electrode.

[0057] The positive electrode sheet includes a positive current collector and a positive active material layer coated on the surface of the positive current collector. The positive active material layer includes a positive active material, which is lithium iron phosphate.

[0058] The fluorinated lithium salt is selected from any one of lithium difluorooxalate borate;

[0059] The fluorinated lithium salt accounts for 12% of the total mass of the electrolyte;

[0060] The positive electrode sheet is laid in the reactor. A hydrothermal reactor is used as the reactor. After preheating it to 100°C, superheated steam is introduced into the reactor. Under a pressure of 0.5MPa, the pressure is maintained for 3 hours. After depressurization to atmospheric pressure, the material is discharged. At this time, the positive active material layer on the surface of the positive electrode sheet has been peeled off from the positive current collector. The positive current collector is separated and removed, and the positive active material layer is collected.

[0061] The positive electrode active material layer is crushed to obtain fragments of the positive electrode active material layer;

[0062] The positive electrode active material layer fragments and solvent N-methylpyrrolidone were mixed at a mass ratio of 1:8, stirred to form a slurry, and then the resulting slurry was pumped into a spray dryer for spray granulation, and active material particles with a D50 of 120 μm were screened out.

[0063] By weight, take 110 parts of active material particles, 25 parts of lithium nitrate, 5 parts of ferrous oxalate, and 8 parts of biomass sugar. Mix them evenly and slowly heat them to 310°C at a rate of 0.5°C / min in an inert atmosphere. After holding the temperature for melting reaction for 8 hours, cool, wash with water, and dry. Then, heat them rapidly to 680°C at a rate of 5°C / min in an inert atmosphere and calcine them for 8 hours. After cooling, discharge the material to complete the regeneration of materials from waste lithium iron phosphate batteries.

[0064] The biomass sugar is selected from fructose. Example 4

[0065] Compared with Example 1, the difference in this embodiment is that the fragmented positive electrode active material layer is directly subjected to the subsequent regeneration process without spray granulation. Specifically:

[0066] The positive electrode active material layer is crushed and sieved to obtain particles with a D50 of 80μm to obtain fragments of the positive electrode active material layer.

[0067] By weight, take 100 parts of positive electrode active material layer fragments, 20 parts of lithium nitrate, 3 parts of ferrous oxalate, and 5 parts of biomass sugar. Mix them evenly and then slowly heat them to 300°C at a rate of 0.3°C / min in an inert atmosphere. After holding the temperature for 4 hours to melt and react, cool, wash with water, and dry. Then, rapidly heat them to 660°C at a rate of 3°C / min in an inert atmosphere and hold the temperature for calcination for 4 hours. After cooling, discharge the material to complete the regeneration of materials from waste lithium iron phosphate batteries. Example 5

[0068] The difference between this embodiment and Embodiment 1 is that the heating rate during the melting process is 3℃ / min, while all other conditions remain unchanged. Specifically:

[0069] By weight, take 100 parts of active material particles, 20 parts of lithium nitrate, 3 parts of ferrous oxalate, and 5 parts of biomass sugar. Mix them evenly and heat them rapidly to 300°C at a rate of 3°C / min in an inert atmosphere. After holding the temperature for 4 hours to melt and react, cool, wash with water, and dry. Then, heat them rapidly to 660°C at a rate of 3°C / min in an inert atmosphere and calcine them for 4 hours. After cooling, discharge the material to complete the regeneration of materials from waste lithium iron phosphate batteries.

[0070] Comparative Example 1

[0071] The difference between this comparative example and Example 1 is as follows:

[0072] The square aluminum-cased battery with lithium iron phosphate as the main cathode material is used as the recycling target, and the battery is obtained by disassembling the battery pack;

[0073] The battery is fully discharged until the cutoff voltage is 2.5V, which is considered to put the battery into an empty state to ensure safety during disassembly and recycling.

[0074] The positive electrode is disassembled and separated. At this time, the positive electrode is still wetted with electrolyte. In this state, it is then dried in an oven at 80°C to constant weight to remove the residual electrolyte solvent in the positive electrode. Since the electrolyte consists of solvent and fluorinated lithium salt dissolved in it, after evaporating and removing the solvent, the fluorinated lithium salt in the electrolyte can be adsorbed into the pores of the positive electrode.

[0075] The positive electrode sheet includes a positive current collector and a positive active material layer coated on the surface of the positive current collector. The positive active material layer includes a positive active material, which is lithium iron phosphate.

[0076] The fluorinated lithium salt is selected from lithium hexafluorophosphate;

[0077] The fluorinated lithium salt accounts for 5% of the total mass of the electrolyte;

[0078] The positive electrode sheet is laid in the reactor. A hydrothermal reactor is used as the reactor. After preheating it to 100°C, deionized water is added to the reactor. After heating to 100°C, the reactor is kept warm and impregnated for 1 hour. The material is discharged and filtered. At this time, the positive active material layer on the surface of the positive electrode sheet has been peeled off from the positive current collector. The positive current collector is separated and removed, and the positive active material layer is collected.

[0079] The positive electrode active material layer is crushed to obtain fragments of the positive electrode active material layer.

[0080] Performance tests were conducted on the products obtained in the examples and comparative examples. The specific test methods and results are shown below:

[0081] Weigh the materials according to a mass ratio of m(regenerated lithium iron phosphate material):m(acetylene black):m(PVDF) = 8:1:1. Place the lithium iron phosphate material and acetylene black in a forced-air drying oven and dry at 100°C for 2 hours. Simultaneously, dissolve the PVDF in N-methylpyrrolidone and stir magnetically for 2 hours until uniformly mixed. Grind the dried lithium iron phosphate material and acetylene black in a mortar and sieve, then add them to the above PVDF N-methylpyrrolidone solution and stir until a uniform black slurry is formed. Coat the slurry onto aluminum foil with a coating thickness of 80 μm, then transfer it to a forced-air drying oven and dry at 90°C for 2 hours. After drying, remove it and roll it under a pressure of 1.8 MPa. Finally, slice it using a button cell punching machine to obtain the positive electrode sheet.

[0082] The battery assembly was carried out in a vacuum glove box filled with Ar. The assembled battery model was CR2016. The positive electrode obtained above was used as the positive electrode, the lithium sheet was used as the counter electrode, and 1 mol / L LiPF6 / EC.DMC.EMC was used as the electrolyte. The positive electrode shell, positive electrode sheet, separator (Celgard 2400), lithium sheet, gasket, spring sheet, and negative electrode shell were placed in sequence and then pressed into a button cell using a pressing machine. The cells were aged in the glove box for 12 hours and then taken out for testing.

[0083] Three sets of batteries were prepared using the same lithium iron phosphate material prepared in the same embodiment or comparative example, according to the battery preparation method described above, to evaluate the performance consistency of the materials obtained in the same batch of embodiments or comparative examples.

[0084] The cycle performance of coin cells was tested using a LAND CT2001A battery testing system. The test environment was 25°C, and the voltage window was 2.5-4.2V. During charging, the charging rate was 0.3C during the constant current stage and cut off at 0.05C after reaching the constant voltage stage, which was considered a full charge. The discharge rate was 0.1C, and the discharge was carried out until the cutoff voltage. The nominal specific capacity of the LFP was set to 170mAh / g. The capacity retention rate after 100 cycles under the corresponding rate conditions was tested to evaluate its cycle performance.

[0085] Detailed test results are shown in Table 1:

[0086] Table 1: Product Performance Test Results

[0087]

[0088]

[0089] As can be seen from the test results in Table 1, in Example 4, the consistency of the product was affected during the regeneration process because spray granulation was not performed, and the test results of different groups had the largest deviation. In contrast, in Comparative Example 1, the pretreatment in the early stage was insufficient due to the lack of water vapor pressurization, and the uniformity and product capacity retention were relatively poor compared to Example 1.

[0090] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for regenerating materials from waste lithium iron phosphate batteries, characterized in that, The specific regeneration steps include: The positive electrode sheet is disassembled and separated, and then dried to remove the residual electrolyte solvent in the positive electrode sheet, so that the fluorinated lithium salt in the electrolyte can be adsorbed into the pores of the positive electrode sheet. The positive electrode sheet includes a positive current collector and a positive active material layer coated on the surface of the positive current collector. The positive active material layer includes a positive active material, which is lithium iron phosphate. The positive electrode sheet is laid in the reactor and preheated to 100°C. Water vapor is introduced into the reactor and pressure is maintained at 0.3-0.5 MPa for 1-3 hours. The pressure is then released to atmospheric pressure, the material is discharged, the positive electrode current collector is separated and removed, and the positive electrode active material layer is collected. The positive electrode active material layer is crushed to obtain fragments of the positive electrode active material layer; By weight, take 100-110 parts of the positive electrode active material layer fragments, 20-25 parts of lithium nitrate, 3-5 parts of ferrous oxalate, and 5-8 parts of biomass sugar. Mix them evenly and heat them in an inert atmosphere to 300-310℃. After holding the temperature for 4-8 hours to melt and react, cool, wash with water, and dry. Then, heat them in an inert atmosphere to 660-680℃ and calcine them for 4-8 hours. After cooling, discharge the material to complete the regeneration of materials from waste lithium iron phosphate batteries.

2. The method for regenerating materials from waste lithium iron phosphate batteries according to claim 1, characterized in that, The biomass sugar is selected from any one of glucose, fructose, galactose, lactose, and sucrose.

3. The method for regenerating materials from waste lithium iron phosphate batteries according to claim 1, characterized in that, The heating temperature rise to 300-310℃ is as follows: Slowly heat to 300-310℃ at a rate of 0.3-0.5℃ / min.

4. The method for regenerating materials from waste lithium iron phosphate batteries according to claim 3, characterized in that, The heating temperature rise to 660-680℃ is as follows: Rapidly heat to 660-680℃ at a rate of 3-5℃ / min.

5. A method for regenerating materials from waste lithium iron phosphate batteries according to claim 1, characterized in that, The fluorinated lithium salt is selected from any one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalate borate.

6. A method for regenerating materials from waste lithium iron phosphate batteries according to claim 5, characterized in that, The mass of the fluorinated lithium salt accounts for 5-12% of the total mass of the electrolyte.

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