A method for regenerating waste lithium iron phosphate

Abstract

The invention belongs to the technical field of recycling waste lithium iron phosphate batteries, and particularly relates to a method for regenerating waste lithium iron phosphate. The method comprises the following steps: oxidizing and leaching the waste lithium iron phosphate in a solution containing iron ions, separating the waste lithium iron phosphate to obtain a leachate and iron phosphate; adding components to the leachate to control the molar number of chloride ions in the leachate to be more than twice the molar number of iron ions, and the molar number of sulfate ions to be no more than 0.5 times the molar number of lithium ions; spraying and pyrolyzing the leachate to obtain a pyrolysis powder; immersing the pyrolysis powder in water, performing solid-liquid separation to obtain iron oxide and a lithium-containing leachate; subjecting the lithium-containing leachate to a lithium precipitation reaction, and separating the lithium carbonate; and mixing an iron source, a lithium source, and a carbon source, and sintering the mixture to obtain the lithium iron phosphate. The method can improve the recycling rate.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste lithium iron phosphate battery recycling, and in particular relates to a waste lithium iron phosphate regeneration method. Background Art

[0002] The method for regenerating lithium iron phosphate comprises the following steps: first, disassembling a lithium iron phosphate battery to obtain a cathode material, and crushing and screening the material to obtain a powder; then, heat treating the material to remove residual graphite and a binder, and then adding an alkaline solution to the powder to dissolve aluminum and aluminum oxides; filtering the material to obtain a filter residue containing lithium, iron, etc., analyzing the molar ratio of iron, lithium, and phosphorus in the filter residue, adding an iron source, a lithium source, and a phosphorus source to adjust the molar ratio of iron, lithium, and phosphorus to 1:1:1; adding a carbon source, ball milling the material, and calcining the material in an inert atmosphere to obtain a new lithium iron phosphate cathode material. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for regenerating waste lithium iron phosphate to improve the recycling rate.

[0004] The embodiment of the present invention provides a method for regenerating waste lithium iron phosphate, comprising the following steps:

[0005] Waste lithium iron phosphate is oxidized and leached in a solution containing iron ions, and separated to obtain leachate and iron phosphate;

[0006] Adding ingredients to the leachate to control the molar number of chloride ions in the leachate to be more than twice the molar number of iron ions and the molar number of sulfate ions to be no more than 0.5 times the molar number of lithium ions;

[0007] The leachate is subjected to spray pyrolysis to obtain pyrolysis powder, the pyrolysis powder is soaked in water, and solid-liquid separation is performed to obtain iron oxide and lithium-containing leachate, and the lithium-containing leachate is subjected to lithium precipitation reaction to separate and obtain lithium carbonate;

[0008] The iron source, lithium source and carbon source are mixed and sintered to obtain lithium iron phosphate.

[0009] Waste lithium iron phosphate is generally in powder form, and the lithium-containing leachate generally contains lithium ions, chloride ions and sulfate ions.

[0010] Preferably, the solution containing iron ions is a mixture of one or more of ferric chloride, ferric chloride hexahydrate, ferric sulfate, ferric sulfate nonahydrate, and ferric nitrate.

[0011] Preferably, the conditions for oxidative leaching are: a molar ratio of iron ions to LiFePO4 of 1 to 2.25:1, a solid-liquid ratio of 10 to 500 g / L, a leaching temperature of 15 to 65°C, and a leaching time of 15 to 60 min.

[0012] Preferably, when adding components to the leachate, the added substances include but are not limited to a mixture of one or more of sulfuric acid, hydrochloric acid, ferric sulfate, ferric chloride, and lithium chloride.

[0013] Preferably, the molar number of chloride ions in the leachate is controlled to be 2 to 10 (preferably 2 to 5) times the molar number of iron ions, and the molar number of sulfate ions is controlled to be 0 to 0.5 (preferably 0.1 to 0.5) times the molar number of lithium ions.

[0014] Preferably, the temperature of the spray pyrolysis is 300-600° C., and hydrogen chloride tail gas is obtained during the spray pyrolysis.

[0015] Preferably, the temperature of the pyrolysis powder water immersion is 20-80°C; the lithium precipitation reaction is that the lithium-containing leaching solution and the carbonate solution are mixed, and the reaction temperature is 40-90°C.

[0016] Preferably, the iron source is iron phosphate or iron oxide, the lithium source includes but is not limited to one or more mixtures of lithium dihydrogen phosphate, lithium phosphate, lithium carbonate, and lithium hydroxide, and the carbon source includes but is not limited to one or more mixtures of glucose, sucrose, starch, carbon black, and ascorbic acid.

[0017] Preferably, the weight of the carbon source is 10-20% of the total weight of the iron source and the lithium source.

[0018] Preferably, the sintering occurs in an inert atmosphere (argon or nitrogen), the sintering temperature is 600-800° C., and the sintering time is 6-15 h.

[0019] The beneficial effect of the present invention is that the present invention uses an iron salt solution instead of an acid solution to leach waste lithium iron phosphate, controls the molar ratio of chloride ions to iron ions, and controls the molar ratio of sulfate ions to lithium ions, so that during spray pyrolysis, the present invention can fully separate lithium, phosphorus and iron and convert them into their respective effective components, thereby maximizing the recovery of lithium iron phosphate and improving the recovery and utilization rate of lithium iron phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flowchart of Example 1 of the present invention. DETAILED DESCRIPTION

[0021] Example 1

[0022] (1) FeCl3•6H2O was prepared into an aqueous solution, and waste lithium iron phosphate powder was placed in the solution for stirring and leaching. The molar ratio of FeCl3•6H2O to LiFePO4 was 1.2:1, the solid-liquid ratio was 100 g / L, the temperature was 25°C, the leaching time was 30 minutes, and the stirring rate was 800 rpm. The leaching reaction liquid was subjected to liquid-solid separation to obtain a leachate containing LiCl and FeCl3 and a leach residue containing FePO4. The test and analysis results showed that the leaching rates of lithium and phosphorus were 99.69% and 1.08%, respectively.

[0023] (2) Sulfuric acid solution is added to the leachate containing LiCl and FeCl3 obtained in step (1) so that the molar number of sulfate ions therein is 0.5 times the molar number of lithium ions.

[0024] (3) The lithium-containing leachate after composition adjustment in step (2) was spray pyrolyzed at 500°C, and the pyrolyzed powder was immersed in water at 70°C. The solid-liquid separation was performed to obtain Fe2O3 and a lithium-containing solution. The test results showed that the leaching rates of lithium and iron under these conditions were 99.03% and 0%, respectively. A certain amount of Na2CO3 was added to the obtained lithium-containing solution to carry out lithium precipitation reaction. The molar ratio of Na2CO3 to lithium was 0.6:1. The lithium precipitation reaction temperature was 80°C and the reaction time was 1 hour. Li2CO3 was obtained after filtration, washing and drying.

[0025] (4) The FePO4 obtained in step (1) was mixed with Li2CO3 and glucose, with the molar ratio of Fe to Li being 1:1.1 and the amount of glucose being 20% of the total mass of the iron phosphate and lithium carbonate. After uniform mixing, the mixture was sintered at 650°C for 10 h under an argon atmosphere to obtain a new lithium iron phosphate positive electrode material. The LiFePO4 exhibited excellent cycling performance (capacity retention of 98.6% after 100 cycles at a 1 C rate).

[0026] The Fe2O3 obtained in step (3) was used as an iron source and mixed with lithium dihydrogen phosphate and glucose, wherein the molar ratio of Fe to Li was 1:1.1 and the amount of glucose was 10% of the total mass of iron phosphate and lithium carbonate. The LiFePO4 positive electrode material was prepared by carbon thermal reduction method under argon atmosphere at 350°C for 1 hour and then at 600°C for 9 hours. The LiFePO4 showed excellent cycle performance (100 cycles at 1 C rate and a capacity retention rate of 99.2%).

[0027] Example 2

[0028] (1) FeCl3•6H2O was prepared into an aqueous solution, and waste lithium iron phosphate powder was placed in the solution for stirring and leaching. The molar ratio of FeCl3•6H2O to LiFePO4 was 1.2:1, the solid-liquid ratio was 100 g / L, the temperature was 25°C, the leaching time was 30 minutes, and the stirring rate was 800 rpm. The leaching reaction liquid was subjected to liquid-solid separation to obtain a leachate containing LiCl and FeCl3 and a leach residue containing FePO4. The test and analysis results showed that the leaching rates of lithium and phosphorus were 99.69% and 0.96%, respectively.

[0029] (2) The leachate containing LiCl and FeCl3 was spray-pyrolyzed at 500°C, and the pyrolyzed powder was then immersed in water at 70°C. Solid-liquid separation was performed to obtain Fe2O3 and LiCl solutions. Test results showed that the leaching rates of lithium and iron under these conditions were 93.43% and 0.1%, respectively. A certain amount of Na2CO3 was added to the obtained LiCl solution to carry out lithium precipitation reaction. The molar ratio of Na2CO3 to LiCl was 0.6:1. The lithium precipitation reaction temperature was 90°C and the reaction time was 1 hour. Li2CO3 was obtained after filtration, washing, and drying.

[0030] (3) The FePO4 obtained in step (1) was mixed with Li2CO3 and glucose, with the molar ratio of Fe to Li being 1:1.1 and the amount of glucose being 20% of the total mass of iron phosphate and lithium carbonate. After uniform mixing, the mixture was sintered at 650°C for 10 h in an argon atmosphere to obtain a new lithium iron phosphate positive electrode material. The LiFePO4 exhibited excellent cycle performance (100 cycles at a 1 C rate and a capacity retention rate of 99.06%).

[0031] The Fe2O3 obtained in step (2) was used as an iron source and mixed with lithium dihydrogen phosphate and glucose, wherein the molar ratio of Fe to Li was 1:1.1 and the amount of glucose was 20% of the total mass of iron phosphate and lithium carbonate. The LiFePO4 positive electrode material was prepared by carbon thermal reduction at 600°C for 9h under an argon atmosphere. The LiFePO4 showed excellent cycle performance (100 cycles at a rate of 1 C and a capacity retention rate of 98.22%).

[0032] Example 3

[0033] (1) Fe2(SO4)3 and FeCl3•6H2O were prepared into a mixed aqueous solution, and waste lithium iron phosphate powder was placed in the solution for stirring and leaching. The molar ratio of Fe2(SO4)3 to LiFePO4 was 1:6, the molar ratio of FeCl3•6H2O to LiFePO4 was 4:1, the solid-liquid ratio was 300 g / L, the temperature was 25°C, the leaching time was 30 minutes, and the stirring rate was 1000 rpm. The leaching reaction liquid was subjected to liquid-solid separation to obtain a leachate containing Li2SO4, Fe2(SO4)3, LiCl, FeCl3 and a leach residue containing FePO4. The test analysis results showed that the leaching rates of lithium and phosphorus were 98.23% and 2.01%, respectively.

[0034] (2) The leachate from step (1) was spray-pyrolyzed at 500°C, and the pyrolyzed powder was immersed in water at 70°C. The solid-liquid separation was performed to obtain Fe2O3 and a lithium-containing solution. The test results showed that the leaching rates of lithium and iron under these conditions were 98.53% and 0.15%, respectively. A certain amount of Na2CO3 was added to the obtained lithium-containing solution to carry out lithium precipitation reaction. The molar ratio of Na2CO3 to lithium was 0.6:1. The lithium precipitation reaction temperature was 90°C and the reaction time was 1 hour. Li2CO3 was obtained after filtration, washing, and drying.

[0035] (3) The FePO4 obtained in step (1) was mixed with Li2CO3 and glucose, with the molar ratio of Fe to Li being 1:1.1 and the amount of glucose being 20% of the total mass of iron phosphate and lithium carbonate. After uniform mixing, the mixture was sintered at 650°C for 10 h in an argon atmosphere to obtain a new lithium iron phosphate positive electrode material. The LiFePO4 exhibited excellent cycle performance (100 cycles at a rate of 1 C, with a capacity retention rate of 98.6%).

[0036] The Fe2O3 obtained in step (2) was used as an iron source and mixed with lithium dihydrogen phosphate and glucose, wherein the molar ratio of Fe to Li was 1:1.1 and the amount of glucose was 15% of the total mass of iron phosphate and lithium carbonate. The LiFePO4 positive electrode material was prepared by carbon thermal reduction at 600°C for 9h under an argon atmosphere. The LiFePO4 showed excellent cycle performance (100 cycles at a rate of 1 C and a capacity retention rate of 99.2%).

[0037] Example 4

[0038] (1) Fe2(SO4)3 was prepared into an aqueous solution, and waste lithium iron phosphate powder was placed in the solution for stirring and leaching. The molar ratio of Fe2(SO4)3 to LiFePO4 was 1:2, the solid-liquid ratio was 100 g / L, the temperature was 25°C, the leaching time was 30 minutes, and the stirring rate was 800 rpm. The leaching reaction liquid was subjected to liquid-solid separation to obtain a leachate containing Li2SO4 and Fe2(SO4)3 and a leach residue containing FePO4. The test analysis results showed that the leaching rates of lithium and phosphorus were 97.07% and 1.21%, respectively.

[0039] (2) Add a certain amount of hydrochloric acid solution and lithium chloride to the leachate containing Li2SO4 and Fe2(SO4)3 obtained in step (1). After mixing, SO4 2- With Li + The molar ratio of Fe is 1:2; 3+ and Cl - The molar ratio is 1:2.5.

[0040] (3) The lithium-containing leachate after the composition adjustment in step (2) was spray-pyrolyzed at 500°C, and the pyrolysis powder was immersed in water at 70°C. The solid-liquid separation was performed to obtain Fe2O3 and a lithium-containing solution. The test results showed that the leaching rates of lithium and iron under these conditions were 99.7% and 0, respectively. A certain amount of Na2CO3 was added to the obtained lithium-containing solution to carry out lithium precipitation reaction. The molar ratio of Na2CO3 to lithium was 0.6:1. The lithium precipitation reaction temperature was 90°C and the reaction time was 1 h. Li2CO3 was obtained after filtration, washing and drying.

[0041] (4) The FePO4 obtained in step (1) was mixed with Li2CO3 and glucose, with the molar ratio of Fe to Li being 1:1.1 and the amount of glucose being 20% of the total mass of iron phosphate and lithium carbonate. After uniform mixing, the mixture was sintered at 650°C for 10 h in an argon atmosphere to obtain a new lithium iron phosphate positive electrode material. The LiFePO4 exhibited excellent cycle performance (100 cycles at a rate of 1 C, with a capacity retention rate of 98.5%).

[0042] The Fe2O3 obtained in step (3) was used as an iron source and mixed with lithium dihydrogen phosphate and glucose, wherein the molar ratio of Fe to Li was 1:1.1 and the amount of glucose was 10% of the total mass of iron phosphate and lithium carbonate. The LiFePO4 positive electrode material was prepared by carbon thermal reduction at 600°C for 9h under an argon atmosphere. The LiFePO4 showed excellent cycle performance (100 cycles at a rate of 1 C and a capacity retention rate of 98.7%).

[0043] Example 5

[0044] (1) FeCl3•6H2O was prepared into an aqueous solution, a small amount of H2O2 was added to the solution, and waste lithium iron phosphate powder was placed in the solution for stirring and leaching. The molar ratio of FeCl3•6H2O to LiFePO4 was 0.6:1, the solid-liquid ratio was 100 g / L, the temperature was 25°C, the leaching time was 30 minutes, and the stirring rate was 800 rpm. The leaching reaction liquid was subjected to liquid-solid separation to obtain a leachate containing LiCl and FeCl3 and a leach residue containing FePO4. The test analysis results showed that the leaching rates of lithium and phosphorus were 99.88% and 2.43%, respectively.

[0045] (2) Sulfuric acid solution is added to the leachate containing LiCl and FeCl3 obtained in step (1) so that the molar number of sulfate ions therein is 0.5 times the molar number of lithium ions.

[0046] (3) The leachate containing LiCl and FeCl3 in step (2) was spray-pyrolyzed at 500°C, and the pyrolysis powder was then immersed in water at 70°C. The solid-liquid separation was performed to obtain Fe2O3 and LiCl solutions. The test results showed that the leaching rates of lithium and iron under these conditions were 99.86% and 0, respectively. A certain amount of Na2CO3 was added to the obtained LiCl solution to carry out lithium precipitation reaction. The molar ratio of Na2CO3 to LiCl was 0.6:1. The lithium precipitation reaction temperature was 90°C and the reaction time was 1 h. Li2CO3 was obtained after filtration, washing and drying.

[0047] (4) The FePO4 obtained in step (1) was mixed with Li2CO3 and glucose, with the molar ratio of Fe to Li being 1:1.1 and the amount of glucose being 20% of the total mass of iron phosphate and lithium carbonate. After uniform mixing, the mixture was sintered at 650°C for 10 h in an argon atmosphere to obtain a new lithium iron phosphate positive electrode material. The LiFePO4 exhibited excellent cycle performance (100 cycles at a rate of 1 C, with a capacity retention rate of 98.5%).

[0048] The Fe2O3 obtained in step (2) was used as an iron source and mixed with lithium dihydrogen phosphate and glucose, wherein the molar ratio of Fe to Li was 1:1.1 and the amount of glucose was 10% of the total mass of iron phosphate and lithium carbonate. The LiFePO4 positive electrode material was prepared by carbon thermal reduction at 600°C for 9h under an argon atmosphere. The LiFePO4 showed excellent cycle performance (100 cycles at a rate of 1 C and a capacity retention rate of 98.8%).

[0049] Comparative Example 1

[0050] (1) Fe2(SO4)3 was prepared into an aqueous solution, and waste lithium iron phosphate powder was placed in the solution for stirring and leaching. The molar ratio of Fe2(SO4)3 to LiFePO4 was 1.1:2, the solid-liquid ratio was 100 g / L, the temperature was 25°C, the leaching time was 30 minutes, and the stirring rate was 800 rpm. The leaching reaction liquid was subjected to liquid-solid separation to obtain a leachate containing Li2SO4 and Fe2(SO4)3 and a leach residue containing FePO4. The test analysis results showed that the leaching rates of lithium and phosphorus were 98.24% and 1.21%, respectively.

[0051] (2) The lithium-containing leachate from step (1) was spray-pyrolyzed at 500°C, and the pyrolyzed powder was immersed in water at 70°C. Solid-liquid separation was performed to obtain Fe2O3 and a lithium-containing solution. Test results showed that under these conditions, the leaching rates of lithium and iron were 99.63% and 98.82%, respectively. It can be seen that although the iron sulfate solution can effectively leach waste lithium iron phosphate, the effective separation of lithium and iron cannot be achieved by directly spray-pyrolyzing the leachate without adjusting its composition.

[0052] Comparative Example 2

[0053] (1) Fe (NO3)3 was prepared into an aqueous solution, and waste lithium iron phosphate powder was placed in the solution for stirring and leaching. The molar ratio of Fe (NO3)3 to LiFePO4 was 1.2:1, the solid-liquid ratio was 100 g / L, the temperature was 25℃, the leaching time was 30 minutes, and the stirring rate was 800 rpm. The leaching reaction liquid was subjected to liquid-solid separation to obtain a leachate containing LiNO3 and Fe (NO3)3 and a leachate containing FePO4. The test analysis results showed that the leaching rates of lithium and phosphorus were 95.62% and 1.34%, respectively.

[0054] (2) The lithium-containing leachate from step (1) was spray-pyrolyzed at 500°C, and the pyrolyzed powder was immersed in water at 70°C. Solid-liquid separation was performed to obtain Fe2O3 and a lithium-containing solution. Test results showed that under these conditions, the leaching rates of lithium and iron were 96.76% and 2.35%, respectively. It can be seen that although the ferric nitrate solution can effectively leach waste lithium iron phosphate and achieve the separation of lithium and iron, it will produce difficult-to-treat NO2 tail gas, causing serious environmental pollution.

[0055] Comparative Example 3

[0056] (1) Fe2(SO4)3 was prepared into an aqueous solution, and waste lithium iron phosphate powder was placed in the solution for stirring and leaching. The molar ratio of Fe2(SO4)3 to LiFePO4 was 1:2, the solid-liquid ratio was 100 g / L, the temperature was 25°C, the leaching time was 30 minutes, and the stirring rate was 800 rpm. The leaching reaction liquid was subjected to liquid-solid separation to obtain a leachate containing Li2SO4 and Fe2(SO4)3 and a leach residue containing FePO4. The test analysis results showed that the leaching rates of lithium and phosphorus were 97.07% and 1.21%, respectively.

[0057] (2) Add a certain amount of hydrochloric acid solution to the leaching solution containing Li2SO4 and Fe2(SO4)3 obtained in step (1), wherein Fe 3+ and Cl - The molar ratio is 1: 1.5.

[0058] (3) The lithium-containing leachate after the composition adjustment in step (2) was spray-pyrolyzed at 500°C, and the pyrolysis powder was immersed in water at 70°C. The solid-liquid separation was carried out to obtain Fe2O3 and lithium-containing solution. The test results showed that the leaching rates of lithium and iron under this condition were 98.63% and 26.82%, respectively. - When the molar number of Fe ions is less than 2 times, lithium and iron elements cannot be well separated by spray pyrolysis.

[0059] Comparative Example 4

[0060] (1) FeCl3•6H2O was prepared into an aqueous solution, and waste lithium iron phosphate powder was placed in the solution for stirring and leaching. The molar ratio of FeCl3•6H2O to LiFePO4 was 1.2:1, the solid-liquid ratio was 100 g / L, the temperature was 25°C, the leaching time was 30 minutes, and the stirring rate was 800 rpm. The leaching reaction liquid was subjected to liquid-solid separation to obtain a leachate containing LiCl and FeCl3 and a leach residue containing FePO4. The test and analysis results showed that the leaching rates of lithium and phosphorus were 99.69% and 1.08%, respectively.

[0061] (2) Sulfuric acid solution is added to the leachate containing LiCl and FeCl3 obtained in step (1) so that the molar ratio of sulfate ions to lithium ions is 1:1.

[0062] (3) The lithium-containing leachate after the composition adjustment in step (2) was spray pyrolyzed at 500°C, and the pyrolyzed powder was then immersed in water at 70°C. The solid-liquid separation was performed to obtain Fe2O3 and LiCl solutions. The test results showed that under these conditions, the leaching rates of lithium and iron were 99.15% and 52.44%, respectively. It can be seen that when the molar ratio of sulfate to lithium in the solution exceeds 0.5 times, the lithium and iron elements cannot be separated well by spray pyrolysis.

[0063] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0064] The one or more embodiments of this application are intended to encompass all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this application should be included in the scope of protection of this application.

Claims

1. A method for regenerating waste lithium iron phosphate, characterized in that: The following steps are included: Waste lithium iron phosphate is oxidized and leached in a solution containing iron ions, and separated to obtain leachate and iron phosphate; Adding ingredients to the leachate to control the molar number of chloride ions in the leachate to be more than twice the molar number of iron ions and the molar number of sulfate ions to be no more than 0.5 times the molar number of lithium ions; The leachate is subjected to spray pyrolysis at a temperature of 300 to 600° C. to obtain pyrolysis powder, the pyrolysis powder is immersed in water, and solid-liquid separation is performed to obtain iron oxide and lithium-containing leachate, and the lithium-containing leachate is subjected to lithium precipitation reaction to separate and obtain lithium carbonate; An iron source, a lithium source and a carbon source are mixed and sintered to obtain lithium iron phosphate; The solution containing iron ions is a mixture of one or more of ferric chloride, ferric chloride hexahydrate, ferric sulfate, ferric sulfate nonahydrate and ferric nitrate.

2. The method for regenerating waste lithium iron phosphate according to claim 1, wherein: The conditions for oxidative leaching are: a molar ratio of iron ions to LiFePO4 of 1 to 2.25:1, a solid-liquid ratio of 10 to 500 g / L, and a leaching temperature of 15 to 65°C.

3. The method for regenerating waste lithium iron phosphate according to claim 1, wherein: When adding components to the leachate, the added substances include but are not limited to one or more mixtures of sulfuric acid, hydrochloric acid, ferric sulfate, ferric chloride, and lithium chloride.

4. The method for regenerating waste lithium iron phosphate according to claim 1, wherein: The molar number of chloride ions in the leachate is controlled to be 2 to 10 times the molar number of iron ions, and the molar number of sulfate ions is controlled to be 0 to 0.5 times the molar number of lithium ions.

5. The method for regenerating waste lithium iron phosphate according to any one of claims 1 to 4, characterized in that: The temperature of water immersion of the pyrolysis powder is 20-80°C; the lithium precipitation reaction is that the lithium-containing leaching solution and the carbonate solution are mixed, and the reaction temperature is 40-90°C.

6. The method for regenerating waste lithium iron phosphate according to any one of claims 1 to 4, wherein: The iron source is iron phosphate or iron oxide, the lithium source includes but is not limited to one or more mixtures of lithium dihydrogen phosphate, lithium phosphate, lithium carbonate, and lithium hydroxide, and the carbon source includes but is not limited to one or more mixtures of glucose, sucrose, starch, carbon black, and ascorbic acid.

7. The method for regenerating waste lithium iron phosphate according to any one of claims 1 to 4, characterized in that: The weight of the carbon source is 10-20% of the total weight of the iron source and the lithium source.

8. The method for regenerating waste lithium iron phosphate according to any one of claims 1 to 4, characterized in that: Sintering takes place in an inert atmosphere at a temperature of 600-800°C.

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