Method for recovering iron and phosphorus from waste lithium iron phosphate battery

Abstract

The application discloses a recovery method of iron and phosphorus in waste lithium iron phosphate battery, and belongs to the technical field of lithium battery recycling. The application provides a salt-assisted carbon thermal reduction-water immersion method, which can efficiently separate phosphorus and iron elements in phosphorus-iron slag and recover Fe products, and the comprehensive recovery rate of iron reaches 99.3% by using the method. Lithium sulfonate and ferrocene are introduced into a sheet-type zirconia ceramic nanofiltration membrane through a chemical reaction, the compatibility of the nanofiltration membrane with fine lithium-containing and iron-suspending particles can be improved in water immersion filtration, the content of metal impurities in the filtrate can be reduced, the efficient separation of iron and phosphorus in the phosphorus-iron slag can be improved, the content of metal in the filtrate is lower than 8%, and the minimum content can reach 0.06%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium battery recycling, and particularly relates to a method for recycling iron and phosphorus from waste lithium iron phosphate batteries. BACKGROUND

[0002] Lithium ion batteries are generally considered to be environmentally friendly and pollution-free green batteries, but improper recycling of lithium ion batteries can also cause pollution. Although lithium ion batteries do not contain toxic heavy metals such as mercury, cadmium and lead, the positive and negative electrode materials, electrolyte and the like of the battery still have a greater impact on the environment and the human body. If the lithium ion battery is treated by ordinary garbage disposal methods (landfill, incineration, composting, etc.), the metals such as cobalt, nickel, lithium and manganese in the battery, as well as various organic and inorganic compounds will cause metal pollution, organic pollution, dust pollution and acid-base pollution. Lithium ion electrolyte machine conversion substances such as LiPF6, lithium hexafluoride arsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), hydrofluoric acid (HF), solvents and hydrolysis products such as ethylene glycol dimethyl ether (DME), methanol, formic acid, etc. are all toxic substances. Therefore, waste lithium ion batteries need to be recycled to reduce the harm to the natural environment and human health.

[0003] For example, the patent application with publication number CN117013128A performs gas reduction roasting on the positive electrode powder; the reduced roasting material is put into sulfuric acid for dissolution and filtration, to obtain a first filtrate and a filter residue, the first filtrate is concentrated and then a carbonate is added to form a precipitate, the precipitate is filtered and dried to obtain lithium carbonate; the filter residue is put into an acid solution, a reducing agent is added, and the leaching solution is obtained after heating and stirring; the leaching solution is adjusted in pH, a copper removal agent is added, and an oxidizing agent is added, and the nickel-cobalt-manganese mixed solution is obtained after heat preservation and impurity removal; evaporation crystallization is performed to obtain a nickel-cobalt-manganese mixed salt and an enrichment mother liquor; the enrichment mother liquor is added with a fluoride, and heat preservation is performed to form calcium-magnesium fluoride precipitate, and the second filtrate is obtained by filtration, most of the second filtrate is returned to the acid solution in the previous step, and a small amount of the second filtrate is discharged.

[0004] For another example, the patent application with publication number CN116903003A uniformly mixes lithium nickel cobalt manganese oxide waste, carbon powder and silicon dioxide to obtain a mixture; the mixture is subjected to gradient temperature dynamic calcination, and during the calcination process, the temperature is gradually increased, and the calcination is sequentially performed at each calcination temperature stage; the calcined material is added with water to form a slurry, sodium hydroxide is added, and a mixed solid is obtained by solid-liquid separation; the mixed solid is added with pure water to form a slurry, and after carbonization, solid-liquid separation is performed to obtain a lithium bicarbonate solution and a mixture of nickel-cobalt-manganese oxides, the lithium bicarbonate solution is purified to obtain a purified solution; the purified solution is pyrolyzed, and a crude lithium carbonate is obtained by solid-liquid separation.

[0005] For example, patent application No. CN116903002A discloses a method for recovering all elements from nickel-cobalt-manganese lithium oxide waste, belonging to the field of waste lithium battery recycling. The method solves the problems of large reagent consumption, complex process, and generation of a large amount of sodium sulfate decahydrate that affects production in existing recovery methods. The method comprises the following steps: mixing the material with carbon powder and calcining; slurry mixing and carbonization; pyrolysis; and cyclic acid leaching, which utilizes solubility characteristics and temperature control to stepwise crystallize different sulfates.

[0006] At present, the proportion of lithium iron phosphate batteries in retired lithium batteries is gradually increasing. While lithium is extracted from these batteries, a large amount of phosphorus-iron slag is left and stored. The composition of the phosphorus-iron slag is complex, and the impurity content is high, which urgently needs to be recycled. SUMMARY

[0007] The present application aims to provide a method for recovering iron and phosphorus from waste lithium iron phosphate batteries. There is no effective treatment method for the phosphorus-iron slag left after lithium recovery from lithium iron phosphate positive electrode materials, which needs to be solved urgently. Therefore, a salt-assisted carbon thermal reduction and water leaching separation method is adopted. First, FePO4 is converted into Fe and phosphorus-containing compounds through the combined action of metal carbonate and carbon thermal reduction. Then, iron and phosphorus are separated by water leaching, and Fe products are recovered. This process is simple to operate, does not use strong inorganic acid, is efficient in recovery, and has the prospect of industrial application.

[0008] The technical problem to be solved by the present application is to achieve efficient separation of iron and phosphorus from phosphorus-iron slag.

[0009] The object of the present application can be achieved by the following technical solutions:

[0010] On the one hand, the present application provides a method for recovering iron and phosphorus from waste lithium iron phosphate batteries, comprising the following steps:

[0011] (1) Discharge, crush and screen the waste lithium iron phosphate batteries to obtain a separator, Al, Cu, lithium iron phosphate powder, graphite powder and a shell, and heat treat the lithium iron phosphate powder;

[0012] (2) Use acid leaching on the heat-treated lithium iron phosphate powder of step (1), filter and wash to obtain phosphorus-iron slag;

[0013] (3) Mix the phosphorus-iron slag obtained in step (2), carbon and metal carbonate uniformly, and then calcine under inert gas to obtain a calcined product;

[0014] (4) Water leach the calcined product in step (3) to obtain a slurry, and then perform solid-liquid separation on the slurry to obtain water leaching residue and water leaching filtrate;

[0015] (5) Magnetically separate the water leaching residue to obtain iron, and filter the water leaching filtrate using a modified ceramic membrane to obtain a phosphorus-containing compound.

[0016] Specifically, in step (5), the preparation method of the modified ceramic membrane is:

[0017] The lithium ferrocene-containing lithium ethyl acrylate sulfonate is generated from lithium 2-hydroxyethyl sulfonate, ferrocene methanol and isocyanate ethyl acrylate, and then a mercapto-acrylic acid addition reaction is performed with the mercapto groups of the mercapotized ceramic nanofiltration membrane to obtain the modified ceramic membrane.

[0018] Further, the modified ceramic membrane is a lithium-loaded sheet-shaped zirconia ceramic nanofiltration membrane, and the specific preparation method is:

[0019] S1: 100-120 parts of sheet-shaped zirconia ceramic nanofiltration membrane with an average pore size of 2-8 nm, 2-4 parts of (mercapto)methylsiloxane, and 600-1000 parts of petroleum ether are put into a stirred tank, and the mixture is stirred at a temperature of 30-42℃ for 2-5 hours, and then taken out and dried; to obtain a mercapotized sheet-shaped zirconia ceramic nanofiltration membrane;

[0020] S2: In a reaction kettle, 0.6-3 parts of lithium 2-hydroxyethyl sulfonate, 10-20 parts of ferrocene methanol, 14-28 parts of isocyanate ethyl acrylate, 2-5 parts of dibutyltin dilaurate, 500-800 parts of petroleum ether, and 50-60℃ are stirred for 2-5 hours, then 100-120 parts of the mercapotized sheet-shaped zirconia ceramic nanofiltration membrane and 5-10 parts of potassium tert-butoxide are added, and the mixture is stirred at a temperature of 50-60℃ for 30-100 minutes, and then taken out and dried to obtain a lithium-loaded sheet-shaped zirconia ceramic nanofiltration membrane.

[0021] Lithium 2-hydroxyethyl sulfonate, ferrocene methanol, and isocyanate ethyl acrylate generate lithium ethyl acrylate sulfonate containing ferrocene; a mercapto-acrylic acid addition reaction is performed with the mercapto groups of the mercapotized sheet-shaped zirconia ceramic nanofiltration membrane; the sulfonate lithium and ferrocene are introduced into the sheet-shaped zirconia ceramic nanofiltration membrane through a chemical reaction, which can improve the compatibility with fine lithium-containing and iron-containing suspended particles in water immersion filtration.

[0022] Specifically, in step (1), the heat treatment conditions are: using nitrogen protection in a high-temperature pyrolysis furnace to perform anaerobic pyrolysis on the organic matter of the waste lithium iron phosphate battery, and the pyrolysis conditions are 450-600℃ and 2-5 hours. Through heat treatment, part of the impurities can be removed.

[0023] Specifically, in step (2), the acid is hydrochloric acid, and the concentration of the acid is 1-3 mol / L.

[0024] The mass ratio of the lithium iron phosphate powder to the acid is 3-4:4-5.

[0025] Preferably, in step (3), the carbon is at least one of graphite, activated carbon, and coke, and in the present application, graphite is preferred.

[0026] The metal carbonate is at least one of potassium carbonate, sodium bicarbonate, magnesium carbonate, and preferably potassium carbonate in the present application,

[0027] The mass ratio of the phosphorus iron slag, carbon and metal carbonate is 1:0.1-0.5:0.6-1.

[0028] Preferably, in step (3), the temperature of the roasting is 800-1000℃, and the roasting time is 3-5h.

[0029] Preferably, in step (4), the water immersion time is 0.8-1.5h.

[0030] The beneficial effects of the present application are:

[0031] (1) To achieve the goal of resource recycling of phosphorus iron slag, a salt-assisted carbon thermal reduction-water immersion method is innovatively developed, which efficiently separates phosphorus and iron elements in the phosphorus iron slag and recovers Fe products from the phosphorus iron slag. The comprehensive recovery rate of iron using the process of the present application is as high as 99.3%.

[0032] (2) The present application introduces lithium sulfonate and ferrocene into the sheet-shaped zirconia ceramic nanofiltration membrane through chemical reaction, which can improve the compatibility with fine lithium and iron-containing suspended particles in the water immersion filtrate, reduce the metal impurity content in the filtrate, improve the efficient separation of iron and phosphorus in the phosphorus iron slag, and reduce the metal content in the filtrate to less than 8%, and the minimum can reach 0.06%. DETAILED DESCRIPTION

[0033] To further illustrate the technical means and effects taken by the present application to achieve the predetermined invention purpose, the specific embodiments, structures, features and effects according to the present application are described in detail as follows in combination with examples.

[0034] Example 1

[0035] 1. Modified ceramic membrane

[0036] S1: Put 110g of sheet-shaped zirconia ceramic nanofiltration membrane with an average pore size of 5nm, 408.6g of (mercapto)methylsiloxane, and 4080g of petroleum ether into a stirred tank, stir at a temperature of 35℃ for 4h, and take out and dry; obtain mercapto sheet-shaped zirconia ceramic nanofiltration membrane;

[0037] S2: In a reaction kettle, 254g of lithium 2-hydroxyethyl sulfonate, 3240.9g of ferrocene methanol, 2963.52g of isocyanate acrylate, 2526.24g of dibutyl tin dilaurate, 3250g of petroleum ether, 55℃ temperature stirring for 4h, then adding 110g of mercapto zirconia ceramic nanofiltration membrane, 785.47g of potassium tert-butoxide, stirring at 55℃ for 65min, taking out and drying to obtain lithium loaded zirconia ceramic nanofiltration membrane.

[0038] 2. A method for recycling iron and phosphorus from waste lithium iron phosphate batteries, comprising the following steps:

[0039] (1) After discharging, disassembling, crushing and sorting the lithium battery, the separator, Al, Cu, iron lithium powder, graphite powder and shell are obtained respectively;

[0040] (2) The iron lithium powder is subjected to heat treatment, and the organic matter of the waste lithium iron phosphate battery is subjected to anaerobic pyrolysis in a nitrogen atmosphere in a high-temperature pyrolysis furnace, and the pyrolysis conditions are 450℃ and 2 hours, and part of the impurities are removed by heat treatment;

[0041] Then 54.75g of hydrochloric acid solution is added for leaching; the concentration of the acid is 1mol / L; the mass ratio of the lithium iron phosphate powder to the acid is 3:4;

[0042] (3) After filtration and washing, the lithium product and the phosphorus iron residue are obtained;

[0043] (4) The mass ratio of K2CO3 to the phosphorus iron residue is 0.7, and the mass ratio of the graphite powder to the phosphorus iron residue is 0.3, and after being uniformly mixed, they are placed in a tube furnace and calcined at 900℃ for 4h in an argon atmosphere;

[0044] (5) The calcined product is then immersed in water at room temperature for 1h to obtain a slurry;

[0045] (6) Then the slurry is subjected to solid-liquid separation to obtain water immersion residue and water immersion filtrate;

[0046] (7) The water immersion residue is subjected to magnetic separation to remove carbon to obtain an iron product, and the water immersion filtrate is filtered by using a modified ceramic membrane, and is evaporated and concentrated to obtain a potassium phosphorus compound.

[0047] The detection results show that the comprehensive recovery rate of iron in this embodiment is 99.3%, and the metal content in the filtrate is 0.06%.

[0048] Example 2

[0049] 1. Modified ceramic membrane

[0050] S1: Put 100 g of sheet-shaped zirconia ceramic nanofiltration membrane with an average pore size of 5 nm, 272.4 g of (mercapto)methylsiloxane, and 3060 g of petroleum ether into a stirred tank, stir for 2 h at a temperature of 30°C, and take out to dry; a sheet-shaped zirconia ceramic nanofiltration membrane with mercapto groups is obtained;

[0051] S2: In a reaction kettle, add 76.2 g of lithium 2-hydroxyethyl sulfonate, 2160.6 g of ferrocene methanol, 1975.68 g of isocyanate acrylate, 1684.16 g of dibutyltin dilaurate, 2550 g of petroleum ether, and stir for 2 h at a temperature of 50°C, then add 100 g of the sheet-shaped zirconia ceramic nanofiltration membrane with mercapto groups, 561.05 g of potassium tert-butoxide, and stir for 30 min at a temperature of 50°C, and take out to dry; a lithium-loaded sheet-shaped zirconia ceramic nanofiltration membrane is obtained.

[0052] 2. A method for recycling iron and phosphorus from waste lithium iron phosphate batteries, comprising the following steps:

[0053] (1) After discharging, disassembling, crushing and sorting the lithium battery, a separator, Al, Cu, iron lithium powder, graphite powder and a shell are obtained respectively;

[0054] (2) The iron lithium powder is subjected to heat treatment, and the organic matter of the waste lithium iron phosphate battery is subjected to anaerobic pyrolysis in a high-temperature pyrolysis furnace under nitrogen protection, the pyrolysis conditions are 500°C and 3 hours, and part of the impurities are removed by heat treatment;

[0055] Then 36.5 g of hydrochloric acid solution is added for leaching; the concentration of the acid is 1.8 mol / L; and the mass ratio of the lithium iron phosphate powder to the acid is 3.5:4.5;

[0056] (3) After filtration and washing, a lithium product and a phosphorus-iron residue are obtained by removing impurities;

[0057] (4) The mass ratio of K2CO3 to the phosphorus-iron residue is 0.6, the mass ratio of graphite powder to the phosphorus-iron residue is 0.1, and after being uniformly mixed, they are placed in a tube furnace and calcined at 800°C for 3 h under an argon atmosphere;

[0058] (5) Then the calcined product is immersed in water at room temperature for 0.8 h to obtain a slurry;

[0059] (6) Then the slurry is subjected to solid-liquid separation to obtain a water immersion residue and a water immersion filtrate;

[0060] (7) The water immersion residue is subjected to magnetic separation to remove carbon to obtain an iron product, and the water immersion filtrate is filtered by using a modified ceramic membrane, evaporated and concentrated to obtain a potassium phosphorus compound.

[0061] The detection results show that the comprehensive recovery rate of iron in this embodiment is 98.1%, and the metal content in the filtrate is 3.5%.

[0062] Example 3

[0063] 1. Modified ceramic membrane

[0064] S1: Put 120 g of zirconium oxide ceramic nanofiltration membrane with an average pore size of 5 nm, 544.8 g of (mercapto)methylsiloxane, and 5100 g of petroleum ether into a stirred tank, stir at a temperature of 42°C for 5 h, and take out to dry; obtain mercapto zirconium oxide ceramic nanofiltration membrane;

[0065] S2: In a reaction kettle, add 381 g of lithium 2-hydroxyethyl sulfonate, 4321.2 g of ferrocene methanol, 3951.36 g of isocyanate acrylate, 4210.4 g of dibutyltin dilaurate, 4080 g of petroleum ether, and stir at a temperature of 60°C for 5 h, then add 120 g of mercapto zirconium oxide ceramic nanofiltration membrane and 1122.1 g of potassium tert-butoxide, stir at a temperature of 60°C for 100 min, take out to dry, and obtain lithium-loaded zirconium oxide ceramic nanofiltration membrane.

[0066] 2. A method for recycling iron and phosphorus from waste lithium iron phosphate batteries, comprising the following steps:

[0067] (1) After discharging, disassembling, crushing and sorting the lithium battery, the separator, Al, Cu, lithium iron powder, graphite powder and shell are obtained respectively;

[0068] (2) The lithium iron powder is subjected to heat treatment, and the organic matter of the waste lithium iron phosphate battery is subjected to anaerobic pyrolysis in a high-temperature pyrolysis furnace under nitrogen protection, the pyrolysis conditions are 600°C and 5 hours, and part of the impurities are removed by heat treatment;

[0069] Then add 73 g of hydrochloric acid solution for leaching; the concentration of the acid is 3 mol / L; the mass ratio of the lithium iron phosphate powder to the acid is 4:5;

[0070] (3) After filtration and washing, the lithium product and the phosphorus-iron residue are obtained;

[0071] (4) The mass ratio of K2CO3 to the phosphorus-iron residue is 1.0, the mass ratio of graphite powder to the phosphorus-iron residue is 0.5, and after being uniformly mixed, they are placed in a tube furnace and calcined at 1000°C for 5 h under argon atmosphere;

[0072] (5) Then the calcined product is immersed in water at room temperature for 1.5 h to obtain a slurry;

[0073] (6) Then the slurry is subjected to solid-liquid separation to obtain water immersion residue and water immersion filtrate;

[0074] (7) The water immersion residue is subjected to magnetic separation to remove carbon to obtain an iron product, and the water immersion filtrate is subjected to filtration using a modified ceramic membrane, evaporation and concentration to obtain a potassium phosphorus compound.

[0075] The detection results show that the comprehensive recovery rate of iron in this embodiment is 97.5%, and the metal content in the filtrate is 7.85%.

[0076] Comparative Example 1

[0077] In the filtration of the water immersion filtrate, a 5 nm sheet-shaped zirconium oxide ceramic nanofiltration membrane is used for separation. The other steps are the same as in Example 1.

[0078] The detection results show that the comprehensive recovery rate of iron in this embodiment is 85%, and the metal content in the filtrate is 36.85%.

[0079] Comparative Example 2

[0080] A method for recovering iron and phosphorus from a waste lithium iron phosphate battery, comprising the following steps:

[0081] (1) After discharging, disassembling, crushing and sorting the lithium battery, the separator, Al, Cu, iron lithium powder, graphite powder and shell are obtained respectively;

[0082] (2) The iron lithium powder is subjected to heat treatment, and the organic matter of the waste lithium iron phosphate battery is subjected to anaerobic pyrolysis in a nitrogen atmosphere in a high-temperature pyrolysis furnace. The pyrolysis conditions are 450℃ and 2 hours, and part of the impurities are removed by heat treatment;

[0083] Then 36.5g of hydrochloric acid solution is added for leaching; the concentration of the acid is 1mol / L; the mass ratio of the lithium iron phosphate powder to the acid is 3:4;

[0084] (3) After filtration and washing, the lithium product and the phosphorus-iron residue are obtained;

[0085] (4) The mass ratio of K2CO3 to the phosphorus-iron residue is 1.0, and the mass ratio of the graphite powder to the phosphorus-iron residue is 0.5. After being mixed uniformly, they are placed in a tube furnace and calcined at 300℃ for 4h under an argon atmosphere;

[0086] (5) The calcined product is then immersed in water at room temperature to obtain a slurry;

[0087] (6) Then the slurry is subjected to solid-liquid separation to obtain a water immersion residue and a water immersion filtrate;

[0088] (7) The water immersion residue is subjected to magnetic separation to remove carbon to obtain an iron product, and the water immersion filtrate is subjected to filter filtration, evaporation and concentration to obtain a potassium-phosphorus compound.

[0089] The detection results show that the comprehensive recovery rate of iron in this embodiment is 83.5%, and the metal content in the filtrate is 33.77%.

Claims

1. A method for recovering iron and phosphorus from a spent lithium iron phosphate battery, characterized by, The method comprises the following steps: (1) discharging, crushing, disassembling and sorting the waste lithium iron phosphate battery to obtain a separator, Al, Cu, lithium iron phosphate powder, graphite powder and a shell, and performing heat treatment on the lithium iron phosphate powder; (2) performing acid leaching on the lithium iron phosphate powder after the heat treatment in step (1), and obtaining a phosphorus-iron residue after filtration and washing; (3) mixing the phosphorus-iron residue obtained in step (2), carbon and a metal carbonate uniformly, and performing roasting under an inert gas to obtain a roasting product; (4) performing water leaching on the roasting product in step (3) to obtain a slurry, and performing solid-liquid separation on the slurry to obtain a water leaching residue and a water leaching filtrate; (5) obtaining iron by performing magnetic separation on the water leaching residue, and obtaining a phosphorus-containing compound by performing filtration on the water leaching filtrate using a modified ceramic membrane. The preparation method of the modified ceramic membrane is as follows: The lithium 2-hydroxyethyl sulfonate, ferrocene methanol and isocyanate acrylate ethyl ester are used to generate lithium acrylate ethyl ester sulfonate containing ferrocene, and then a thiol-acrylic acid addition reaction is performed on the thiol of the thiolated ceramic nanofiltration membrane to obtain the modified ceramic membrane.

2. The method of claim 1, wherein the spent lithium iron phosphate battery is a lithium iron phosphate battery. The modified ceramic membrane is a lithium-loaded sheet-shaped zirconium oxide ceramic nanofiltration membrane, and the specific preparation method is as follows: S1: 100-120 parts of sheet-shaped zirconium oxide ceramic nanofiltration membrane with an average pore size of 2-8 nm, 2-4 parts of mercaptomethyl siloxane and 600-1000 parts of petroleum ether are put into a stirring kettle, and the mixture is stirred at a temperature of 30-42°C for 2-5 hours, and then taken out and dried; a thiolated sheet-shaped zirconium oxide ceramic nanofiltration membrane is obtained; S2: 0.6-3 parts of lithium 2-hydroxyethyl sulfonate, 10-20 parts of ferrocene methanol, 14-28 parts of isocyanate acrylate ethyl ester, 2-5 parts of dibutyltin dilaurate, 500-800 parts of petroleum ether and 50-60°C are added to a reaction kettle, and the mixture is stirred at a temperature of 50-60°C for 2-5 hours, and then 100-120 parts of the thiolated sheet-shaped zirconium oxide ceramic nanofiltration membrane and 5-10 parts of potassium tert-butoxide are added, and the mixture is stirred at a temperature of 50-60°C for 30-100 minutes, and then taken out and dried; a lithium-loaded sheet-shaped zirconium oxide ceramic nanofiltration membrane is obtained.

3. The method for recovering iron and phosphorus from spent lithium iron phosphate batteries according to claim 1, characterized in that, In step (1), the heat treatment is performed at a temperature of 450-600°C for 2-5 hours.

4. The method as claimed in claim 1, wherein the spent lithium iron phosphate battery is a lithium ion battery. In step (2), the acid is hydrochloric acid, and the concentration of the acid is 1-3 mol / L. The mass ratio of the lithium iron phosphate powder to the acid is 3-4:4-5.

5. The method for recovering iron and phosphorus from spent lithium iron phosphate batteries according to claim 1, characterized in that, In step (3), the carbon is at least one of graphite, activated carbon and coke, and the metal carbonate is at least one of potassium carbonate, sodium bicarbonate and magnesium carbonate. The mass ratio of the phosphorus-iron residue, carbon and metal carbonate is 1:0.1-0.5:0.6-1.

6. The method for recovering iron and phosphorus from spent lithium iron phosphate batteries according to claim 1, characterized in that, In step (3), the roasting temperature is 800-1000°C, and the roasting time is 3-5 hours.

7. The method for recovering iron and phosphorus from spent lithium iron phosphate batteries according to claim 1, characterized in that, In step (4), the water leaching time is 0.8-1.5 hours.