A method for recycling lithium manganese iron phosphate battery and positive electrode material thereof

Abstract

The present invention provides a method for recycling lithium iron manganese phosphate (LFMPO) batteries and their cathode materials, which relates to the field of battery material recycling technology. The method utilizes sodium hydroxide mixed with the LFMPO battery cathode material and roasted to oxidize the various metal elements in the LFMPO battery cathode material. The material is then dissolved using a weak acid to separate and recover the metal elements. This method avoids the use of strong acids, effectively reducing the burden on equipment and wastewater treatment, while achieving high recovery efficiency for each metal element.

Description

Technical Field

[0001] The present invention relates to the technical field of battery material recycling, and in particular to a method for recycling a lithium manganese iron phosphate battery and a cathode material thereof. Background Art

[0002] Lithium manganese iron phosphate (LMFP) is a new cathode material formed by introducing manganese into lithium iron phosphate (LFP). Compared to LFP batteries, LMFP batteries have a higher energy density and are driving the continued development of electric vehicle technology. However, with the widespread use of LFP, the amount of battery waste generated has also increased. Recycling the elements in this waste is of great economic and environmental significance.

[0003] In existing technologies, treatment of lithium manganese iron phosphate batteries typically involves strong acid leaching or oxidative roasting. Strong acid leaching, due to the use of strong acids, places significant strain on equipment and wastewater disposal. Oxidative roasting, on the other hand, not only offers lower yields but also requires multiple subsequent acid leaching steps, sometimes requiring the addition of auxiliary salts and reducing agents. This can be complex and introduce new impurities. Summary of the Invention

[0004] The object of the present invention is to provide a method for recovering the positive electrode material of a lithium manganese iron phosphate battery, which is simple and convenient to operate, has low requirements on equipment, and can quickly and efficiently recover various metal elements in the positive electrode material of the lithium manganese iron phosphate battery.

[0005] Another object of the present invention is to provide a method for recycling lithium manganese iron phosphate batteries, which can further improve the efficiency and purity of recycling by pretreatment in combination with the above-mentioned method for recycling the positive electrode material of lithium manganese iron phosphate batteries.

[0006] The present invention is achieved in that:

[0007] A method for recovering positive electrode materials of lithium manganese iron phosphate batteries, comprising:

[0008] S1. Mixing a positive electrode material of a lithium manganese iron phosphate battery with sodium hydroxide to obtain a mixture;

[0009] S2, roasting the mixture under oxygen conditions to obtain a roasted material;

[0010] S3, dissolving the calcined material under weak acidic conditions, filtering, and obtaining a filtrate;

[0011] S4, reacting the filtrate with aqueous ammonia, filtering, and obtaining lithium phosphate precipitate;

[0012] S5. Reacting the lithium phosphate precipitate with phosphoric acid, filtering, and concentrating to obtain lithium dihydrogen phosphate.

[0013] A method for recycling lithium manganese iron phosphate batteries, comprising:

[0014] The lithium iron phosphate battery is pretreated to obtain the positive electrode material of the lithium iron phosphate battery, and the positive electrode material of the lithium iron phosphate battery is processed using the above-mentioned method for recovering the positive electrode material of the lithium iron phosphate battery.

[0015] The beneficial effects of the embodiments of the present invention are:

[0016] An embodiment of the present invention provides a method for recovering lithium iron phosphate (LFMPO) batteries and their cathode materials. This method utilizes sodium hydroxide mixed with the LFMPO battery's cathode material and roasted to oxidize the various metal elements in the battery's cathode material. The material is then dissolved using a weak acid to separate and recover the metal elements. This method avoids the use of strong acids, effectively reducing the burden on equipment and wastewater treatment, while achieving high recovery efficiency for each metal element. DETAILED DESCRIPTION

[0017] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0018] The following is a detailed description of a lithium manganese iron phosphate battery and a method for recycling its positive electrode material according to an embodiment of the present invention.

[0019] An embodiment of the present invention provides a method for recycling a positive electrode material of a lithium manganese iron phosphate battery, comprising:

[0020] S1. Mixing a positive electrode material of a lithium manganese iron phosphate battery with sodium hydroxide to obtain a mixture;

[0021] S2. calcining the mixed material under oxygen conditions to obtain a calcined material.

[0022] To achieve optimal mixing, the positive electrode material for the lithium iron phosphate battery is pre-crushed and sieved to a particle size of ≤20μm. Furthermore, the molar ratio of the positive electrode material to sodium hydroxide is 1:(3.03-3.05). At this ratio, a slight excess of sodium hydroxide ensures a more complete reaction and avoids the formation of byproducts. If the sodium hydroxide is too little, the lithium iron phosphate will not react completely and will produce the byproduct Li3PO4. If the sodium hydroxide is too much, the byproduct NaFe / MnO2 will be produced, which will reduce the efficiency of subsequent Na3PO4 leaching. It should be noted that the molar weight of the positive electrode material for the lithium iron phosphate battery is estimated by directly dividing the mass of the positive electrode material by the molecular weight of the lithium iron phosphate.

[0023] Furthermore, in step S2, the aerobic condition can be an air atmosphere or an oxygen atmosphere. The calcination temperature is 800-850°C and the duration is 6-10 hours. Under the calcination conditions, the following reactions occur:

[0024] a) Decomposition of sodium hydroxide: NaOH(l) → Na2O + H2O

[0025] b) Ion exchange: Na + Diffusion to the surface of LiMnFePO4 particles, and diffusion to the interior of particles through defects or grain boundaries, bulk reaction, and PO4 3- Combined to form Na3PO4; and Li + Backward diffusion to the surface to form Li2O;

[0026] LiMnFePO4+ 3Na + → Na3PO4+ Li + + Mn 2+ + Fe 2+ + O 2-

[0027] 2Li + + O 2- → Li2O

[0028] Mn 2+ + O 2- → MnO → Mn3O4

[0029] Fe 2+ + O 2- → FeO → Fe2O3

[0030] Li2O remains stable at calcination temperatures without decomposing, effectively preventing lithium loss during calcination. Manganese and iron, under oxygen and high temperature conditions, form the more stable Mn3O4 and Fe2O3, rather than Mn2O3 and Fe3O4. Furthermore, the moisture and carbon contained in the cathode material of lithium manganese iron phosphate batteries can be converted into water vapor and carbon dioxide during the calcination process and removed.

[0031] Furthermore, in step S2, the cathode material mixture of the lithium manganese iron phosphate battery is first heated to 400-500°C, kept warm for 1-3 hours, and then heated to 800-850°C for calcination. Preheating at 400-500°C allows the sodium hydroxide to form a molten state, better wrapping it around the lithium manganese iron phosphate powder. This not only ensures more uniform mixing and avoids local accumulation, but also improves mass transfer efficiency. During the heating process, the temperature should not be raised too quickly; a heating rate of 5-15°C / min is sufficient.

[0032] The embodiment of the present invention provides a method for recycling positive electrode materials of a lithium manganese iron phosphate battery, further comprising:

[0033] S3. Dissolve the calcined material under weak acidic conditions, filter, and obtain a filtrate.

[0034] Before dissolution, the calcined material should be cooled to below 100°C. The pH of weakly acidic conditions is 5-5.8, and the dissolution temperature is 10-30°C. In practice, the calcined material can be dispersed in water and the pH adjusted with an acid solution while stirring. Sulfuric acid is preferably used, with a concentration of 1wt% to 5wt%. Due to the low acid concentration and dissolution temperature, Mn3O4 and Fe2O3 dissolve slowly, forming a precipitate. Li2O, on the other hand, dissolves rapidly, generating the more soluble LiH2PO4 at this pH and entering the filtrate. It should be noted that improper pH control, if the pH is too high, will generate Li3PO4, which has a low solubility and forms a precipitate, resulting in lithium loss.

[0035] After filtration, the filtrate mainly contains LiH2PO4, Na2SO4, H2SO4, and trace amounts of (Fe / Mn)2(SO4)3 and MnSO4; while the filter cake mainly contains undissolved Fe2O3 and Mn3O4. After the filter cake is washed with 1% dilute sulfuric acid and dried in an oven at 120~150℃ for 2~5h, a higher purity iron-manganese mixture can be obtained, which can be recycled and reused in the synthesis of lithium manganese iron phosphate.

[0036] The embodiment of the present invention provides a method for recycling positive electrode materials of a lithium manganese iron phosphate battery, further comprising:

[0037] S4. reacting the filtrate with aqueous ammonia, filtering, and obtaining lithium phosphate precipitate.

[0038] Optionally, the filtrate is adjusted to a pH of 11-12 with 20wt%-40wt% ammonia water, and filtered after stirring at 30-50°C for 20-60 minutes. Under this condition, LiH2PO4 in the filtrate is converted into Li3PO4 and precipitated. After filtration, Na2SO4, (NH4)2SO4, (NH4)3PO4, and NH4OH remain in the filtrate, which can be subsequently used as raw materials for the production of fertilizers. It should be noted that since the solubility of Na2SO4 and LiH2PO4 in the filtrate is not much different, cooling crystallization separation is not suitable, so lithium phosphate must be generated by ammonia water to achieve separation.

[0039] The embodiment of the present invention provides a method for recycling positive electrode materials of a lithium manganese iron phosphate battery, further comprising:

[0040] S5. Reacting the lithium phosphate precipitate with phosphoric acid, filtering, and concentrating to obtain lithium dihydrogen phosphate.

[0041] Optionally, in step S5, the lithium phosphate precipitate is dispersed in water, and the pH is adjusted to 3.5-4.5 with phosphoric acid before filtration. The lithium phosphate is redissolved and filtered to further remove trace amounts of Mn / Fe(OH)2 and Mn / Fe(OH)3 impurities in the lithium phosphate precipitate. The filtered filtrate is concentrated and evaporated at 100-130°C to remove the solvent, yielding high-purity LiH2PO4 crystals.

[0042] Furthermore, an embodiment of the present invention also provides a method for recycling lithium manganese iron phosphate batteries, which comprises:

[0043] The lithium iron phosphate battery is pretreated to obtain the positive electrode material of the lithium iron phosphate battery, and the positive electrode material of the lithium iron phosphate battery is processed using the above-mentioned method for recovering the positive electrode material of the lithium iron phosphate battery.

[0044] Furthermore, pre-treating the lithium manganese iron phosphate battery includes:

[0045] S0-1. Calcine the lithium manganese iron phosphate battery and crush it into powder.

[0046] Before roasting, the easily separated battery shells (aluminum shells, steel shells, etc.) and surface plastic parts are removed by manual or mechanical sorting. Then, the battery is crushed and discharged using a jaw crusher.

[0047] The roasting temperature is 400-450℃. Roasting can decompose organic materials such as electrolyte, binder, and diaphragm in the battery. The decomposed tail gas is sent to the alkaline spray tower for absorption. The combustible CH gas not absorbed by the spray tower is stored and then burned as waste gas. The reaction formula is as follows:

[0048] LiPF6→ LiF(s) + PF5(g)

[0049] PF5+ H2O → POF3(g)+ HF(g)

[0050] HF + NaOH → NaF(aq)+ H2O(l)

[0051] POF3+ NaOH → Na3PO4(aq) + NaF(aq)+ H2O(l)

[0052] Organic carbonate, PP membrane + NaOH → Na2CO3(aq) + CH3COONa(aq) + small molecule hydrocarbons (CH4, C2H4, C3H8, etc.)

[0053] PVDF + NaOH → NaF(aq) + Na2CO3(aq) + CH3COONa(aq)+ CH4(g)

[0054] The calcined material enters a roller mill for mechanical crushing, and then is crushed by air flow to obtain a powder with a particle size of ≤1mm.

[0055] S0-2. Separate the powder into heavy powder and light powder using a cyclone.

[0056] The ingredients and density of the powder are as follows:

[0057] Positive electrode material: 3.4-3.6 g / cm³, negative electrode graphite: 2.2-2.3 g / cm³, copper foil: 8.96 g / cm³, aluminum foil: 2.7g / cm³.

[0058] The cyclone uses a heavy medium suspension with a density of approximately 2.85 g / cm³, achieving optimal separation. The separation yields heavy powder, composed of copper powder and cathode material powder, and light powder, composed of aluminum powder and graphite powder.

[0059] S0-3. The heavy powder is separated by a continuous centrifugal concentrator to obtain the positive electrode material of lithium manganese iron phosphate battery.

[0060] Furthermore, the centrifugal concentrator uses a feed concentration of 10% to 20%, water as the dispersion medium, a centrifugal force of ≥500G, and a drum inclination of 15°. After separation, a high-purity positive electrode material for lithium manganese iron phosphate batteries can be obtained.

[0061] Alternatively, the light powder can be separated using an eddy current separator: A high-frequency separation of the Al powder is employed, with a magnetic field frequency of 300-500 Hz, a magnetic roller speed of 2000-4000 rpm, and a conveyor belt inclination angle of ≤10°. The separated Al powder contains approximately 0.15% LiF, which can be recovered during the aluminum powder refining process through Li+ resin adsorption / desorption in the solution step, or through directional extraction using solvents such as tributyl phosphate and crown ether.

[0062] This pretreatment process effectively separates copper, aluminum, and cathode materials from lithium manganese iron phosphate batteries, achieving recovery rates of 99.87%, 99.0%, and 98.5%, respectively. This efficient recovery of copper and aluminum not only provides a high-purity cathode material, but also lays the foundation for further recycling.

[0063] The features and performance of the present invention are further described in detail below with reference to the embodiments. Example 1

[0064] This embodiment provides a pretreatment method for a lithium manganese iron phosphate battery, which includes:

[0065] S0-1: Lithium manganese iron phosphate batteries are mechanically sorted to remove easily detachable battery casings (aluminum, steel, etc.) and surface plastic parts. They are then initially crushed and discharged using a jaw crusher. They are then calcined in a 400°C kiln. After calcination, they are then subjected to roller milling and then air flow milling to obtain a powder with a particle size of ≤1mm.

[0066] S0-2: The powder is separated into heavy and light powders using a cyclone. The density of the heavy medium suspension used in the cyclone is approximately 2.85 g / cm³.

[0067] S0-3: The heavy powder is separated by a continuous centrifugal concentrator to obtain the positive electrode material of lithium manganese iron phosphate battery. Example 2

[0068] This embodiment provides a method for recycling positive electrode materials of a lithium manganese iron phosphate battery, which includes:

[0069] S1: The positive electrode material of the lithium manganese iron phosphate battery obtained in Example 1 is further air flow-pulverized, sieved to a particle size of ≤20 μm, and mixed with sodium hydroxide (molar ratio 1:3.03) to obtain a mixture.

[0070] S2. The mixture was heated to 450°C at a rate of 10°C / min in air atmosphere and kept at that temperature for 2 hours. Then, the mixture was heated to 850°C at a rate of 10°C / min and calcined for 6 hours.

[0071] S3. Cool the calcined material to below 100°C, take it out, add it into pure water at a ratio of S / L = 1 / 10, and stir it at room temperature of 25°C for 30 minutes. During this period, use 3% dilute sulfuric acid to adjust the pH to ≤ 5.8; filter to obtain the filtrate and filter cake, wash the filter cake with dilute sulfuric acid with a mass ratio of (1% dilute sulfuric acid: filter cake = 1:1), and dry the filter cake in an oven at 120°C for 2 hours to recover Fe2O3 and Mn3O4.

[0072] S4. The filtrate was adjusted to pH 11-12 using 28% ammonia solution, stirred at 40°C for 30 minutes, filtered, and washed with pure water at a mass ratio (washing: filter cake = 1:1) to obtain lithium phosphate precipitate.

[0073] S5. Add lithium phosphate into 2.5 times the mass of pure water, stir and disperse at 80°C, and use phosphoric acid to adjust the pH to 4. At this time, the solution is transparent; after filtering, the filtrate is heated to 120°C for evaporation and concentration to obtain LiH2PO4 crystals, which are washed with pure water at a mass ratio of (washing liquid: filter cake = 0.3:1). Example 3

[0074] This embodiment provides a method for recycling positive electrode materials of a lithium manganese iron phosphate battery, which includes:

[0075] S1: The positive electrode material of the lithium manganese iron phosphate battery obtained in Example 1 is further air flow-pulverized, sieved to a particle size of ≤20 μm, and mixed with sodium hydroxide (molar ratio 1:3.05) to obtain a mixture.

[0076] S2. The mixture was heated to 500°C at a rate of 15°C / min in air atmosphere and kept at that temperature for 1 hour. Then, the mixture was heated to 800°C at a rate of 15°C / min and calcined and kept at that temperature for 10 hours.

[0077] S3. Cool the calcined material to below 100°C, take it out, add it into pure water at a ratio of S / L = 1 / 10, and stir it at room temperature at 30°C for 30 minutes. During this period, use 5% dilute sulfuric acid to adjust the pH to ≤ 5.5; filter to obtain the filtrate and filter cake, use dilute sulfuric acid with a mass ratio of (1% dilute sulfuric acid: filter cake = 1:1) to wash the filter cake, and dry the filter cake in a 120°C oven for 2 hours to recover Fe2O3 and Mn3O4.

[0078] S4. The filtrate was adjusted to pH 11-12 using 35% ammonia solution, stirred at 50°C for 20 minutes, filtered, and washed with pure water at a mass ratio (washing: filter cake = 1:1) to obtain lithium phosphate precipitate.

[0079] S5. Add lithium phosphate into 3 times the mass of pure water, stir and disperse at 80℃, use phosphoric acid to adjust the pH to 4, at which time the solution is transparent; after filtering, heat the filtrate to 120℃ and evaporate and concentrate to obtain LiH2PO4 crystals, which are washed with pure water with a mass ratio of (washing liquid: filter cake = 0.3:1).

[0080] Comparative Example 1

[0081] This comparative example provides a method for recovering the positive electrode material of a lithium manganese iron phosphate battery. The operating steps are basically the same as those in Example 2, except that, in step S1, the molar ratio of the positive electrode material of the lithium manganese iron phosphate battery to sodium hydroxide is adjusted to 1:4.

[0082] Comparative Example 2

[0083] This comparative example provides a method for recovering the positive electrode material of a lithium manganese iron phosphate battery. The operating steps are basically the same as those in Example 2, except that, in step S1, the molar ratio of the positive electrode material of the lithium manganese iron phosphate battery to sodium hydroxide is adjusted to 1:2.

[0084] Comparative Example 3

[0085] This comparative example provides a method for recovering the positive electrode material of a lithium manganese iron phosphate battery. The operating steps are basically the same as those in Example 2, except that in step S2, calcination is performed under oxygen-free conditions (nitrogen atmosphere).

[0086] Comparative Example 4

[0087] This comparative example provides a method for recovering the positive electrode material of a lithium manganese iron phosphate battery. The operating steps are basically the same as those in Example 2, except that in step S3, the pH of the dissolution is 6.5.

[0088] Comparative Example 5

[0089] This comparative example provides a method for recovering the positive electrode material of a lithium manganese iron phosphate battery. The operating steps are basically the same as those in Example 2, except that in step S3, the dissolution temperature is 80°C.

[0090] Comparative Example 6

[0091] This comparative example provides a method for recycling the positive electrode material of a lithium iron manganese phosphate battery. The operating steps are basically the same as those in Example 2, except that, in step S1, 0.5 wt% of aluminum powder is mixed into the positive electrode material of the lithium iron manganese phosphate battery.

[0092] Test Example 1

[0093] The recovery methods for the positive electrode materials of lithium manganese iron phosphate batteries provided in Examples 2-3 and Comparative Examples 1-6 were used to test the recovery rate of each element and the purity of the product. The specific results are shown in Table 1:

[0094] Table 1: Comparison of lithium iron phosphide recovery rates

[0095] <![CDATA[Purity of Mn3O4 / %]]> <![CDATA[Fe2O3 purity / %]]> <![CDATA[Purity of LiH2PO4 / %]]> Manganese recovery rate / % Iron recovery rate / % Lithium recovery rate / % Example 2 99.82 99.69 99.98 99.07 98.94 99.47 Example 3 100.01 99.98 99.75 98.90 99.13 99.06 Comparative Example 1 90.73 91.25 98.96 95.80 94.55 97.34 Comparative Example 2 87.33 85.62 93.49 80.09 75.84 83.26 Comparative Example 3 23.67 17.84 36.98 19.77 27.50 43.11 Comparative Example 4 97.83 96.02 98.74 98.83 99.04 90.56 Comparative Example 5 98.57 98.80 96.68 97.70 96.89 99.08 Comparative Example 6 97.90 98.38 98.57 98.02 97.57 90.81

[0096] As shown in Table 1, the recovery methods provided in Examples 2 and 3 of the present invention can achieve recovery rates of over 98% for the manganese, iron, and lithium elements in the positive electrode material of lithium manganese iron phosphate batteries, and the resulting product purity exceeds 99%. These materials can be directly used as raw materials for re-introduction into lithium manganese iron phosphate production.

[0097] In contrast, in Comparative Example 1, excessive sodium hydroxide was used in step S1, resulting in the formation of a large amount of NaFe / MnO2 byproducts. In subsequent steps, the presence of Na(Fe / Mn)O2 significantly affected the purity of Mn3O4 and Fe2O3. Furthermore, excessive NaSO4 was generated and adhered to the LiPO4 surface, slightly affecting the purity of LiH2PO4 without secondary recrystallization or acid washing. Furthermore, excessive NaOH resulted in the use of more acid during pH adjustment, increasing costs.

[0098] In Comparative Example 2, in step S1, the amount of sodium hydroxide was reduced, the lithium manganese iron phosphate could not react completely, and the unreacted lithium manganese iron phosphate was difficult to dissolve with dilute sulfuric acid, resulting in a large amount of metal element loss.

[0099] In Comparative Example 3, the oxygen-free conditions were changed to anaerobic conditions. Metal elements such as manganese, iron, and lithium were unable to form oxides, and subsequent dissolution with dilute sulfuric acid was impossible, resulting in recovery failure. Only a small amount of metal elements was recovered, and the purity was very low.

[0100] In Comparative Example 4, the pH of the solution in step S3 was adjusted to 6.5. Part of the lithium precipitated as lithium phosphate and entered the filter cake, resulting in lithium loss and affecting the purity of Mn3O4 and Fe2O3.

[0101] In Comparative Example 5, increasing the dissolution temperature in step S3 accelerated the dissolution of Mn3O4 and Fe2O3, causing Mn and Fe to enter the filtrate, making subsequent purification difficult. This reduced the purity of LiH2PO4 and affected the recovery rates of all three metals to varying degrees.

[0102] In Comparative Example 6, 0.5 wt% aluminum powder was mixed into step S1 to investigate the situation where the pretreatment failed to completely separate the aluminum powder. It can be seen that the high activity of Al will form a compound with Li, resulting in difficulty in dissolving in the subsequent dilute sulfuric acid dissolution step, causing significant lithium loss and reducing the lithium yield to 90.81%.

[0103] In summary, the present invention provides a method for recovering lithium iron phosphate (LFMPO) batteries and their cathode materials. This method utilizes sodium hydroxide mixed with the LFMPO battery's cathode material for calcination to oxidize the metal elements in the battery's cathode material. The material is then dissolved in a weak acid solution to separate and recover the metal elements. This method avoids the use of strong acids, effectively reducing equipment and wastewater processing pressures, while achieving high recovery efficiency for each metal element.

[0104] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for recovering positive electrode materials of lithium manganese iron phosphate batteries, characterized in that: include: S1, mixing the lithium manganese iron phosphate battery positive electrode material with sodium hydroxide to obtain a mixture; S2, roasting the mixed material under oxygen conditions to obtain a roasted material; S3, dissolving the calcined material under weak acidic conditions, filtering, and obtaining a filtrate; S4, reacting the filtrate with aqueous ammonia, filtering, and obtaining lithium phosphate precipitate; S5, reacting the lithium phosphate precipitate with phosphoric acid, filtering, and concentrating to obtain lithium dihydrogen phosphate; In step S1, the molar ratio of the lithium manganese iron phosphate battery positive electrode material to the sodium hydroxide is 1: (3.03-3.05); In step S2, the calcination temperature is 800-850°C and the calcination time is 6-10 hours; In step S3, the pH of the weakly acidic conditions is 5-5.8, and the dissolution temperature is 10-30°C; In step S4, the filtrate is adjusted to a pH of 11-12 with 20 wt %-40 wt % ammonia water, stirred at 30-50° C. for 20-60 min, and then filtered.

2. The method for recycling the positive electrode material of lithium manganese iron phosphate battery according to claim 1, characterized in that: In step S2, the mixed material is first heated to 400-500°C, kept at this temperature for 1-3 hours, and then heated to 800-850°C for calcination.

3. The method for recycling the positive electrode material of lithium manganese iron phosphate battery according to claim 1, characterized in that: In step S5, the lithium phosphate precipitate is dispersed in water, and the pH is adjusted to 3.5-4.5 with phosphoric acid before filtering.

4. A method for recycling lithium manganese iron phosphate batteries, characterized in that: include: The lithium iron manganese phosphate battery is pretreated to obtain a lithium iron manganese phosphate battery positive electrode material, and the lithium iron manganese phosphate battery positive electrode material is processed using the recovery method of the lithium iron manganese phosphate battery positive electrode material according to any one of claims 1 to 3.

5. The method for recycling lithium manganese iron phosphate batteries according to claim 4, characterized in that: Pre-treating the lithium manganese iron phosphate battery includes: calcining the lithium manganese iron phosphate battery and crushing it into powder; Separating the powder into heavy powder and light powder using a cyclone; The heavy powder is separated by a continuous centrifugal concentrator to obtain the positive electrode material of lithium manganese iron phosphate battery.

6. The method for recycling lithium manganese iron phosphate batteries according to claim 5, wherein: The particle size of the powder does not exceed 1 mm.