Method for recycling all components of waste manganese iron lithium phosphate positive electrode material

Abstract

The application relates to the technical field of lithium ion batteries, in particular to a recovery method of all components of a waste manganese iron lithium phosphate positive electrode material. The recovery method comprises the following steps: reacting the waste manganese iron lithium phosphate positive electrode material and an oxidizing agent under an oxygen-containing gas atmosphere to obtain a first mixed solution; performing solid-liquid separation on the first mixed solution to obtain a first filtrate and a first residue; reacting the first filtrate and carbon dioxide to obtain lithium carbonate; reacting the first residue and an acid to obtain a second mixed solution; performing solid-liquid separation on the second mixed solution to obtain a second filtrate and a second residue; reacting the second filtrate and manganese dioxide to obtain manganese phosphate; dissolving the second residue in an acid, and performing crystallization to obtain iron phosphate. The recovery method has the advantages of simple operation, small acid and alkali consumption, controllable quality, easy industrialization and the like, can generate good economic and social benefits, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery positive electrode materials, and in particular to a method for recovering all components of waste lithium manganese iron phosphate positive electrode materials. Background Art

[0002] Lithium manganese iron phosphate (LiFe 1-x Mn x Lithium manganese phosphate (LMFP) combines the high thermal stability of LiFePO4 with the high energy density of LiMnPO4, making it widely used as a cathode material for lithium batteries. With the continuous mass production and large-scale application of batteries, the amount of retired lithium manganese iron phosphate cathode material is increasing year by year, making the development of recycling methods for it of great significance.

[0003] Current LMFP recovery methods suffer from cumbersome operations, high acid and alkali consumption, and low product added value. Patent publication number CN 113851748 A describes a method for recycling and regenerating waste olivine-type cathode materials for lithium-ion batteries. This method involves reacting waste manganese iron lithium cathode powder with a strong oxidant and a dilute acid solution to separate the lithium and phosphate. While this method effectively recovers lithium, it also struggles with co-precipitation of iron and manganese, preventing high-value recovery of both.

[0004] Patent publication number CN 115535987 A describes a method for recovering valuable elements from lithium iron manganese phosphate cathode waste. The method involves fully leaching the lithium iron manganese phosphate cathode powder using a high-acid solution, followed by oxidation and pH adjustment to sequentially precipitate crude iron phosphate, manganese phosphate, and lithium phosphate. This method offers a higher recovery rate than traditional methods, but the production cost of the finished product is higher, and the purity of the finished product needs to be further improved.

[0005] Based on this, it is necessary to provide a method for recovering lithium manganese iron phosphate with low cost, more comprehensive recovery components and higher purity of finished products. Summary of the Invention

[0006] Based on this, one or more embodiments of the present application provide a method for recovering all components of waste lithium manganese iron phosphate positive electrode materials, and the technical solution is as follows:

[0007] A method for recovering all components of waste lithium manganese iron phosphate positive electrode material comprises the following steps:

[0008] reacting waste lithium manganese iron phosphate cathode material with an oxidant in an oxygen-containing gas atmosphere to obtain a first mixed liquid, performing solid-liquid separation on the first mixed liquid to obtain a first filtrate and a first filter residue, controlling the pH value of the first mixed liquid to be 4-7, wherein the oxidant comprises manganese phosphate hydrate;

[0009] reacting the first filtrate with carbon dioxide to obtain lithium carbonate;

[0010] reacting the first residue with an acid to obtain a second mixture, and performing solid-liquid separation on the second mixture to obtain a second filtrate and a second residue, wherein the pH value of the second mixture is controlled to be 2.5-4;

[0011] reacting the second filtrate with manganese dioxide to obtain manganese phosphate;

[0012] dissolving the second residue in an acid and performing crystallization to obtain iron phosphate.

[0013] In one embodiment, the waste lithium manganese iron phosphate positive electrode material and an oxidizing agent are reacted in an oxygen-containing gas atmosphere to obtain a first mixture, which comprises:

[0014] The waste lithium manganese iron phosphate, a first acid, a first water, and an oxidizing agent are heated at a first temperature for a first time in an oxygen-containing gas atmosphere to obtain the first mixture;

[0015] The flow rate of the oxygen-containing gas is 0.3 m 3 / h-0.5 m 3 / h, the first temperature is 50°C-95°C, and the first time is 3 h-10 h;

[0016] Optionally, the oxygen-containing gas contains oxygen molecules in a volume percentage of 20%-100%, and the oxygen molecules include oxygen gas molecules and ozone molecules;

[0017] Optionally, the manganese phosphate hydrate comprises at least one of MnPO4·H2O and Mn3(PO4)2·7H2O;

[0018] Optionally, the first acid comprises at least one of hydrochloric acid, sulfuric acid, and nitric acid;

[0019] Optionally, the weight ratio of the waste lithium manganese iron phosphate positive electrode material, the first acid, the first water, and the oxidizing agent is 1:(0.3-0.8):(2-8):(0.10-0.30).

[0020] In one embodiment, the pH value of the reaction solution is detected after the waste lithium manganese iron phosphate, a first acid, and a first water, and an oxidizing agent are heated at a first temperature for a first time in an oxygen-containing gas atmosphere;

[0021] If the pH value of the reaction solution is 4-7, the reaction solution is collected to obtain the first mixture;

[0022] If the pH value of the reaction solution is not 4-7, a pH value adjusting agent is added to the reaction solution in batches until the pH value of the reaction solution is 4-7, and the reaction solution is collected to obtain the first mixture.

[0023] In one embodiment, the first filtrate and carbon dioxide are reacted to obtain lithium carbonate, comprising:

[0024] The first filtrate, the first base and carbon dioxide are reacted in a closed container at a second temperature for a second time, and the liquid is collected by solid-liquid separation to obtain purified lithium liquid;

[0025] The purified lithium liquid is pyrolyzed to obtain the lithium carbonate;

[0026] The partial pressure of the carbon dioxide in the closed container is 1 MPa to 2 MPa, the second temperature is 25°C to 50°C, and the second time is 1 h to 5 h;

[0027] Optionally, the first base comprises at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate;

[0028] Optionally, the weight ratio of the first base to the waste manganese iron lithium phosphate positive electrode material is (0.2-0.6):1.

[0029] In one embodiment, the purified lithium liquid is pyrolyzed to obtain the lithium carbonate, comprising:

[0030] The purified lithium liquid is pyrolyzed at a third temperature for a third time, and the solid is collected by solid-liquid separation to obtain the lithium carbonate;

[0031] The third temperature is 85°C to 100°C, and the third time is 1.5 h to 4 h.

[0032] In one embodiment, the first filtrate and acid are reacted to obtain a second mixed liquid, comprising:

[0033] The first filtrate, the second acid and the second water are reacted at a fourth temperature for a fourth time to obtain the second mixed liquid;

[0034] The fourth temperature is 25°C to 60°C, and the fourth time is 2.5 h to 4 h;

[0035] Optionally, the second acid comprises at least one of sulfuric acid, nitric acid and phosphoric acid;

[0036] Optionally, the mass ratio of the waste manganese iron lithium phosphate positive electrode material, the second acid and the second water is 1:(0.15-0.5):(3-15).

[0037] In one embodiment, after the first filtrate, the second acid and the second water are heated at a fourth reaction temperature for a fourth reaction time, the pH value of the reaction liquid is detected;

[0038] if the pH value of the reaction solution is 2.5-4, the reaction solution is collected to obtain the second mixed solution;

[0039] if the pH value of the reaction solution is not 2.5-4, a pH value regulator is added to the reaction solution in batches until the pH value of the reaction solution is 2.5-4, and the reaction solution is collected to obtain the second mixed solution.

[0040] In one embodiment, the second filtrate and manganese dioxide are reacted to obtain manganese phosphate, including:

[0041] The second filtrate and the manganese dioxide are reacted at a fifth temperature for a fifth time, and the filtrate is collected by solid-liquid separation;

[0042] The filtrate is mixed with a second base and reacted at a sixth temperature for a sixth time, and the solid is collected by solid-liquid separation to obtain the manganese phosphate;

[0043] The fifth temperature is 25-50°C, the fifth time is 0.5-1.5h, the sixth temperature is 25-50°C, and the sixth time is 2-5h.

[0044] Optionally, the second base includes at least one of ammonia water or ammonium carbonate.

[0045] Optionally, the mass ratio of the manganese dioxide to the waste and old manganese iron lithium phosphate positive electrode material is (0.01-0.05):1.

[0046] In one embodiment, the second filter residue is dissolved in an acid, and crystallization is performed to obtain iron phosphate, including:

[0047] The second filter residue, a third acid, and a third water are reacted at a seventh temperature for a seventh time, and the filtrate is collected by solid-liquid separation;

[0048] After the pH value of the filtrate is adjusted to 2-3, seeding and crystallization are performed to obtain the iron phosphate;

[0049] The seventh temperature is 25-60°C, and the seventh time is 2.0-4.0h.

[0050] Optionally, the third acid includes at least one of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid.

[0051] Optionally, the seed crystal includes at least one of amorphous iron phosphate, amorphous hydroxy iron phosphate, crystalline iron phosphate, and crystalline hydroxy iron phosphate.

[0052] Optionally, the mass ratio of the third acid, the third water, and the waste and old manganese iron lithium phosphate positive electrode material is (0.5-1.5):(3-10):1.

[0053] Optionally, the ratio of the amount of the seed crystal to the weight of the waste lithium manganese iron phosphate positive electrode material is (0.05-0.1):1.

[0054] In one embodiment, the pH of the filtrate is adjusted to 2-3, seed crystals are added for crystallization, and the iron phosphate is obtained.

[0055] After the pH of the filtrate is adjusted to 2-3, the filtrate is heated to 80-100°C, the seed crystals are added and stirred for 2-4 hours, and the iron phosphate is obtained.

[0056] Optionally, the stirring speed is 250-500 r / min.

[0057] The present application has at least the following advantages:

[0058] (1) The recycling method of the present application can comprehensively recycle manganese, lithium, iron metal elements and phosphate in lithium manganese iron phosphate, and can achieve recycling at a very high yield. Manganese, lithium, iron metal elements and phosphate are recycled in the form of manganese phosphate, lithium carbonate and iron phosphate. It is detected that in some embodiments, the yield of the obtained manganese phosphate is ≥96%, the yield of lithium carbonate and iron phosphate is both ≥97%, and the purity of the three products is all ≥99%.

[0059] (2) The present application has the advantages of simple operation, controllable quality and easy industrialization, can produce good economic and social benefits, and has a broad application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0060] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0061] Figure 1 The XRD spectrum of lithium carbonate obtained by recycling in one embodiment of the present application;

[0062] Figure 2 The XRD spectrum of manganese phosphate obtained by recycling in one embodiment of the present application;

[0063] Figure 3 The XRD spectrum of iron phosphate obtained by recycling in one embodiment of the present application. DETAILED DESCRIPTION

[0064] The present application will be further described in conjunction with specific embodiments and drawings. The present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, the purpose of the embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0066] As used herein, the terms "and / or", "or / and", and "and / or" in the optional sense include any one of two or more associated listed items, as well as any and all combinations of the associated listed items, including a combination of any two associated listed items, any more associated listed items, or all associated listed items.

[0067] In the case of using "including", "having", and "containing" described herein, it is intended to cover non-exclusive inclusion, unless the explicit limiting language such as "only", "consisting of", etc. is used, another component can also be added.

[0068] Unless otherwise mentioned, the singular form of the terms can include the plural form and cannot be understood as one in number.

[0069] In the present application, "at least one" refers to any one, any two, or any two or more of the listed items.

[0070] In one aspect of the present application, a method for recycling all components of waste lithium manganese iron phosphate positive electrode material is provided, which can comprehensively recycle manganese, iron, lithium and phosphate of waste materials, has high recovery rate, and the recycled product has high quality, less impurities and high purity, and can be reused in battery manufacturing process.

[0071] Reference can be made to Figure 1 The method for recycling all components of waste lithium manganese iron phosphate positive electrode material according to an embodiment of the present application is realized by the following steps:

[0072] S100: reacting the waste lithium manganese iron phosphate positive electrode material and an oxidizing agent in an oxygen-containing gas atmosphere to obtain a first mixed solution, and performing solid-liquid separation on the first mixed solution to obtain a first filtrate and a first residue, wherein the pH value of the first mixed solution is controlled to be 4-7, and the oxidizing agent includes manganese phosphate hydrate;

[0073] S200: reacting the first filtrate with carbon dioxide to obtain lithium carbonate;

[0074] S300: reacting the first residue and the acid to obtain a second mixed solution, and performing solid-liquid separation on the second mixed solution to obtain a second filtrate and a second residue, wherein the pH value of the second mixed solution is controlled to be 2.5-4;

[0075] S400: reacting the second filtrate and manganese dioxide to obtain manganese phosphate;

[0076] S500: dissolving the second residue in acid and crystallizing to obtain iron phosphate.

[0077] The following further describes each step.

[0078] Step S100:

[0079] In S100, the lithium iron manganese phosphate material is selectively oxidized by manganese phosphate hydrate and an oxygen-containing gas, realizing efficient separation of lithium, manganese and iron components. On the one hand, based on the strong oxidizing property of manganese phosphate hydrate, the in-situ oxidation of the positive electrode material is strengthened, ensuring efficient dissolution of lithium while manganese and iron components are retained in the leaching residue. On the other hand, based on the crystallizing agent function of manganese phosphate hydrate, part of the manganese ions entering the solution are crystallized and precipitated in the form of Mn3(PO4)2·3H2O, further achieving the purpose of effective separation of lithium ions from manganese, iron and phosphorus.

[0080] In one embodiment, the waste lithium manganese iron phosphate positive electrode material and the oxidizing agent are reacted to obtain a first mixed solution, which includes:

[0081] The waste lithium manganese iron phosphate, the first acid, the first water and the oxidizing agent are heated at a first temperature for a first time under an oxygen-containing gas atmosphere to obtain a first mixed solution.

[0082] Optionally, the flow rate of the oxygen-containing gas is selected from 0.3m 3 / h to 0.5m 3 / h, for example 0.3m 3 / h, 0.4m 3 / h, 0.5m 3 / h, etc.

[0083] Optionally, the first temperature is selected from 50°C to 95°C, for example 50°C, 60°C, 70°C, 80°C, 90°C, 95°C, etc.

[0084] Optionally, the first time is selected from 3h to 10h, for example 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc.

[0085] Further, after heating the waste lithium manganese iron phosphate, the first acid, the first water and the oxidizing agent at a first temperature for a first time under an oxygen-containing gas atmosphere, the pH value of the reaction solution is detected;

[0086] If the pH value of the reaction solution is 4-7, the reaction solution is collected to obtain a first mixed solution;

[0087] If the pH value of the reaction solution is not 4-7, a pH value adjusting agent is added to the reaction solution in batches until the pH value of the reaction solution is 4-7, and the reaction solution is collected to obtain the first mixed solution.

[0088] Optionally, the pH value of the first mixed solution is selected from 4-7, for example, 4, 5, 6, 7, etc.

[0089] Optionally, the first acid includes at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0090] Optionally, the oxygen-containing gas contains oxygen molecules in a volume percentage of 20%-100%, and the oxygen molecules include oxygen molecules and ozone molecules.

[0091] Optionally, the manganese phosphate hydrate includes at least one of MnPO4·H2O and Mn3(PO4)2·7H2O.

[0092] Before step S100, through estimation of the stoichiometric ratio, the pH value of the reaction solution after mixing the waste old manganese iron lithium phosphate, the first acid, the first water, and the oxidizing agent can be initially determined, and the ideal pH value should be 4-7. It can also be calculated that after the waste old manganese iron lithium phosphate, the first acid, the first water, and the oxidizing agent are heated at the first temperature for the first time, the pH value of the reaction solution is 4-7 or close to this range, which is beneficial to improve the recovery rate of manganese, iron, and lithium, and is also beneficial to improve the reaction efficiency, save the reagent for adjusting the pH value, and improve the product quality of lithium carbonate.

[0093] In one embodiment, to obtain a suitable oxidation result and pH value, the weight ratio of the waste old manganese iron lithium phosphate positive electrode material, the first acid, the first water, and the oxidizing agent is 1:(0.3-0.8):(2-8):(0.10-0.30).

[0094] Optionally, the weight ratio of the waste old manganese iron lithium phosphate positive electrode material and the first acid is 1:(0.3-0.8), for example, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, etc.

[0095] Optionally, the weight ratio of the waste old manganese iron lithium phosphate positive electrode material and the first water is 1:(2-8), for example, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, etc.

[0096] Optionally, the weight ratio of the waste old manganese iron lithium phosphate positive electrode material and the oxidizing agent is 1:(0.1-0.3), for example, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, etc.

[0097] Step S200:

[0098] In S100, lithium in the waste old manganese iron phosphate positive electrode material is efficiently leached to obtain a first filtrate containing lithium, while manganese and iron components are retained in the leaching residue to obtain a first filter residue containing manganese and iron. In S200, the first filtrate is reacted with carbon dioxide to recover lithium in the form of lithium carbonate from the first filtrate.

[0099] In one embodiment, the first filtrate is reacted with carbon dioxide to obtain lithium carbonate, comprising:

[0100] In a closed container, the first filtrate, the first alkali and the carbon dioxide are reacted at a second temperature for a second time, and the liquid is collected by solid-liquid separation to obtain a purified lithium liquid;

[0101] The purified lithium liquid is pyrolyzed to obtain lithium carbonate;

[0102] In the above, the partial pressure of carbon dioxide in the closed container is 1 MPa to 2 MPa, the second temperature is 25°C to 50°C, and the second time is 1h to 5h.

[0103] Optionally, the first alkali includes at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate.

[0104] Optionally, the weight ratio of the first alkali to the waste old manganese iron phosphate positive electrode material is selected from (0.2-0.6):1, for example 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, etc.

[0105] In one embodiment, the purified lithium liquid is pyrolyzed to obtain the lithium carbonate, comprising:

[0106] The purified lithium liquid is pyrolyzed at a third temperature for a third time, and the solid is collected by solid-liquid separation to obtain lithium carbonate;

[0107] In the above, the partial pressure of carbon dioxide in the closed container is 1 MPa to 2 MPa, the second temperature is 25°C to 50°C, and the second time is 1h to 5h.

[0108] Optionally, the second temperature is selected from 25°C to 50°C, for example 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, etc.

[0109] Optionally, the second time is selected from 1h to 5h, for example 1h, 2h, 3h, 4h, 5h, etc.

[0110] In one embodiment, the purified lithium liquid is pyrolyzed to obtain the lithium carbonate, comprising:

[0111] The purified lithium liquid is pyrolyzed at a third temperature for a third time, solid-liquid separation is performed to obtain the solid, and lithium carbonate is obtained;

[0112] The third temperature is 85-100 DEG C, and the third time is 1.5-4 hours.

[0113] Optionally, the third temperature is selected from 85-100 DEG C, such as 85 DEG C, 88 DEG C, 90 DEG C, 92 DEG C, 95 DEG C, 100 DEG C, etc.

[0114] Optionally, the third time is selected from 1.5-4 hours, such as 1.5 hours, 2 hours, 3 hours, 4 hours, etc.

[0115] In the above, pyrolysis refers to the heating of an organic compound at high temperature, resulting in its decomposition into smaller molecules.

[0116] Step S300:

[0117] In S100, lithium in the waste old manganese iron phosphate positive electrode material is efficiently leached to obtain a first filtrate containing lithium, while manganese and iron components are retained in the leaching residue to obtain a first filter residue containing manganese and iron. In S300, the first filter residue is treated with acid to obtain a second mixed solution, and the second mixed solution is subjected to solid-liquid separation to obtain a second filtrate and a second filter residue, so that manganese is mainly present in the second filtrate and iron is mainly present in the second filter residue.

[0118] In one embodiment, the first filter residue and the acid are reacted to obtain a second mixed solution, comprising:

[0119] The first filter residue, the second acid and the second water are reacted at a fourth temperature for a fourth time to obtain a second mixed solution;

[0120] The fourth temperature is 25-60 DEG C, and the fourth time is 2.5-4 hours.

[0121] Further, the first filter residue, the second acid and the second water are heated at a fourth reaction temperature for a fourth reaction time, and the pH value of the reaction solution is detected;

[0122] If the pH value of the reaction solution is 2.5-4, the reaction solution is collected to obtain the second mixed solution;

[0123] If the pH value of the reaction solution is not 2.5-4, a pH value adjusting agent is added to the reaction solution in batches until the pH value of the reaction solution is 2.5-4, and the reaction solution is collected to obtain the mixed solution.

[0124] Optionally, the pH value of the second mixed solution is selected from 2.5-4, such as 2.5, 3, 3.5, 4, etc.

[0125] Optionally, the second acid comprises at least one of sulfuric acid, nitric acid and phosphoric acid.

[0126] Before step S300, through the estimation of stoichiometric ratio, the pH value of the reaction liquid after mixing the first filter residue, the second acid and the second water can be initially determined, and the ideal pH value should be 2.5-4, and it can also be calculated that after the first filter residue, the second acid and the second water are heated at the fourth reaction temperature for the fourth reaction time, the pH value of the reaction liquid is 2.5-4 or close to the range, which is beneficial to save the reagent for adjusting the pH value and improve the recovery rate of iron components.

[0127] In one embodiment, to obtain suitable oxidation results and pH values, the mass ratio of the first filter residue, the second acid and the second water is 1:(0.15-0.5):(3-15).

[0128] Optionally, the mass ratio of the first filter residue and the second acid is selected from 1:(0.15-0.5), for example, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, etc.

[0129] Optionally, the mass ratio of the first filter residue and the second water is selected from 1:(3-15), for example, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc.

[0130] Step S400:

[0131] In S300, the first filter residue is treated to obtain the second filtrate and the second filter residue, so that manganese mainly exists in the second filtrate, and in S400, the second filtrate and manganese dioxide are reacted to recover manganese in the form of manganese phosphate.

[0132] In one embodiment, the second filtrate and manganese dioxide are reacted to obtain manganese phosphate, which comprises:

[0133] The second filtrate and manganese dioxide are reacted at a fifth temperature for a fifth time, and the filtrate is obtained by solid-liquid separation;

[0134] The filtrate and the second base are mixed and reacted at a sixth temperature for a sixth time, and the solid is obtained by solid-liquid separation to obtain manganese phosphate;

[0135] Among them, the fifth temperature is 25℃-50℃, the fifth time is 0.5h-1.5h, the sixth temperature is 25℃-50℃, and the sixth time is 2h-5h.

[0136] Optionally, the fifth temperature and the sixth temperature are independently selected from 25℃-50℃, for example, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, etc.

[0137] Optionally, the fifth time and the sixth time are independently selected from 2h-5h, such as 2h, 3h, 4h, 5h, and the like.

[0138] Optionally, the second base comprises at least one of ammonia or ammonium carbonate.

[0139] Optionally, the mass ratio of the manganese dioxide to the waste and old lithium manganese iron phosphate positive electrode material is (0.01-0.05):1, such as 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, and the like.

[0140] Step S500:

[0141] In S300, the first residue is treated to obtain a second filtrate and a second residue, so that iron mainly exists in the second residue. In S500, the second residue is dissolved in acid, and iron is recovered in the form of iron phosphate by crystallization.

[0142] In one embodiment, the second residue is dissolved in acid, and iron phosphate is obtained by crystallization, comprising:

[0143] The second residue, the third acid, and the third water are reacted at a seventh temperature for a seventh time, and the filtrate is obtained by solid-liquid separation;

[0144] After adjusting the pH value of the filtrate to 2-3, seed crystals are added for crystallization to obtain iron phosphate;

[0145] The seventh temperature is 25-60°C, and the seventh time is 2h-4h.

[0146] Optionally, the seventh temperature is selected from 25°C-60°C, such as 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, and the like.

[0147] Optionally, the seventh time is independently selected from 2h-4h, such as 2h, 2.5h, 3h, 3.5h, 4h, and the like.

[0148] Optionally, the third acid comprises at least one of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid.

[0149] Optionally, the seed crystals comprise at least one of amorphous iron phosphate, amorphous iron hydroxy phosphate, crystalline iron phosphate, and crystalline iron hydroxy phosphate.

[0150] Optionally, the mass ratio of the third acid, the third water, and the waste and old lithium manganese iron phosphate positive electrode material is (0.5-1.5):(3-10):1.

[0151] Optionally, the mass ratio of the third acid to the waste and old lithium manganese iron phosphate positive electrode material is selected from (0.5-1.5):1, such as 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, and the like.

[0152] Optionally, the mass ratio of the third water to the waste old lithium manganese iron phosphate positive material is selected from (3-10): 1, for example, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0153] Optionally, the ratio of the amount of the seed crystal added to the weight of the waste old lithium manganese iron phosphate positive material is (0.05-0.1): 1, for example, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, etc.

[0154] In one embodiment, after adjusting the pH value of the filtrate to 2-3, seed crystals are added for crystallization to obtain iron phosphate, including:

[0155] After adjusting the pH value of the filtrate to 2-3, the filtrate is heated to 80-100°C, seed crystals are added, and stirred for 2-4h to obtain iron phosphate.

[0156] Optionally, the stirring speed is 250-500r / min, for example, 250r / min, 300r / min, 350r / min, 400r / min, 450r / min, 500r / min, etc.

[0157] Optionally, after adding seed crystals for crystallization, iron phosphate crystals are obtained, filtered, and dried.

[0158] Optionally, the drying temperature is 80-120°C, and the drying time is 1-4h.

[0159] Optionally, the seed crystal is at least one of amorphous iron phosphate, amorphous iron hydroxy phosphate, crystalline iron phosphate, and crystalline iron hydroxy phosphate, and the mass ratio of the seed crystal to the waste old lithium manganese iron phosphate positive material is (0.05-0.1): 1.

[0160] In some embodiments, the waste old lithium manganese iron phosphate positive material is recovered by the full-component recovery method of the present application, the recovery rates of lithium carbonate and iron phosphate are both not less than 97%, the recovery rate of manganese phosphate is not less than 96.5%, the purity of lithium carbonate can reach 99.6% or above, the amount of impurity phosphate in lithium carbonate meets the battery recycling standard, and the contents of phosphate and sulfate impurities are not higher than 500ppm.

[0161] The following are some specific embodiments.

[0162] The raw materials, reagent materials, etc. used in the following specific embodiments are commercially available products unless otherwise specified.

[0163] In this application, the amount of acid added refers to the amount to be added after estimation based on the waste powder, and can be adjusted appropriately during actual addition as long as the pH value of the mixed solution after the acid and water are added is within the specified range.

[0164] Example 1

[0165] (1) At a flow rate of 0.40 m 3 In an air atmosphere at a flow rate of 1 / h, 500 kg of waste lithium manganese iron phosphate powder, approximately 150 kg of sulfuric acid, and 1000 kg of pure water were mixed, and 150 kg of an oxidizing agent, Mn3(PO4)2·3H2O, was added. The pH was adjusted to 4.0, and the mixture was reacted at 95°C for 10 hours. The end point pH was measured to be 5, thereby obtaining a first mixed solution. The first mixed solution was subjected to solid-liquid separation to obtain a first filtrate and a first filter residue.

[0166] (2) In a sealed container, mix 100 kg of sodium hydroxide and the first filtrate, introduce carbon dioxide at a partial pressure of 1.0 MPa, and react at 25°C for 5 h. Collect the liquid after solid-liquid separation to obtain a purified lithium solution. Pyrolyze the purified lithium solution at 100°C for 1.5 h, collect the solid after solid-liquid separation, and dry the solid at 100°C for 1.5 h to obtain battery-grade lithium carbonate. Yield: 97.6%.

[0167] (3) The first filter residue, approximately 150 kg of sulfuric acid, and 3000 kg of pure water were mixed, the pH value was adjusted to 2.5, and the mixture was reacted at 25°C for 2.5 hours. The end point pH value was measured to be 2.65, thereby obtaining a second mixed solution. The second mixed solution was subjected to solid-liquid separation to obtain a second filtrate and a second filter residue.

[0168] (4) The second filtrate and 5 kg of manganese dioxide were reacted at 50°C for 0.5 h. The liquid was collected by solid-liquid separation. Ammonia water was added to the liquid to adjust the pH to 5. The mixture was reacted at 50°C for another 2 h. The solid was collected by solid-liquid separation. The solid was washed and dried at 110°C for 2 h to obtain high-purity manganese phosphate heptahydrate with a yield of 96.8%.

[0169] (5) The second filter residue, 250 kg of sulfuric acid and 1500 kg of pure water were mixed and stirred at 50 ° C for 2 hours to dissolve. The liquid was collected by solid-liquid separation. Ammonia water was added to the liquid to adjust the pH value to 2.5. The liquid was heated to 100 ° C. 25 kg of crystalline iron phosphate was added and stirred for 2 hours (400 r / min). The solid was collected by solid-liquid separation to obtain wet iron phosphate. The wet iron phosphate was washed and dried at 200 ° C for 1 hour to obtain battery-grade iron phosphate dihydrate with a yield of 97.2%. The lithium carbonate, manganese phosphate and iron phosphate prepared above were subjected to XRD test and obtained Figure 1 The diffraction patterns shown were compared with the corresponding product standard cards to confirm that the products obtained in this example were all pure phases.

[0170] The lithium carbonate prepared above is detected by atomic emission spectrometry (ICP), and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead are all less than 10 ppm; the content of impurity SO4 2- and PO4 3- is 300 ppm by infrared spectroscopy analysis; and the content of lithium carbonate is 99.65% by chemical titration analysis.

[0171] The manganese phosphate prepared above is detected by atomic emission spectrometry (ICP), and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, and nickel are all less than 10 ppm.

[0172] The iron phosphate prepared above is detected by atomic emission spectrometry (ICP), and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead are all less than 10 ppm; the content of impurity SO4 2- is 300 ppm by infrared spectroscopy analysis; and the Fe / P ratio is 0.975 by chemical titration analysis.

[0173] Example 2

[0174] (1) 800 Kg of lithium manganese iron phosphate waste powder, about 240 Kg of sulfuric acid, 80 Kg of nitric acid, and 4000 Kg of pure water are mixed under an oxygen atmosphere with a flow rate of 1.0 m 3 / h, 240 kg of oxidant MnPO4·H2O is added, the pH value is adjusted to 5.5, and reaction is carried out at 95°C for 3 h. The end point pH value is measured to be 6.0, and a first mixed solution is obtained. The first mixed solution is subjected to solid-liquid separation to obtain a first filtrate and a first residue.

[0175] (2) 200 Kg of sodium hydroxide is mixed with the first filtrate in a closed container, carbon dioxide is introduced and the carbon dioxide oxygen partial pressure is controlled to be 1.0 MPa, reaction is carried out at 45°C for 5 h, and the liquid is collected by solid-liquid separation to obtain purified lithium liquid. The purified lithium liquid is pyrolyzed at 100°C for 2 h, the solid is collected by solid-liquid separation, and the solid is dried at 90°C for 4 h to obtain battery-grade lithium carbonate, with a yield of 97.5%.

[0176] (3) The first residue, about 400 Kg of sulfuric acid, and 8000 Kg of pure water are mixed, the pH value is adjusted to 3.0, and reaction is carried out at 45°C for 3 h. The end point pH value is measured to be 3.2, and a second mixed solution is obtained. The second mixed solution is subjected to solid-liquid separation to obtain a second filtrate and a second residue.

[0177] (4) The second filtrate is reacted with 40 Kg of manganese dioxide at 30°C for 0.5 h, and the liquid is collected by solid-liquid separation. Ammonia water is added to the liquid to adjust the pH value to 5.0, and then the liquid is reacted at 40°C for 2 h. The solid is collected by solid-liquid separation, washed, and dried at 100°C for 1 h to obtain high-purity manganese phosphate heptahydrate, with a yield of 96.9%.

[0178] (5) The second filter residue, 1200 kg of phosphoric acid and 4000 kg of pure water were mixed and stirred at 25 ° C for 2 hours. The liquid was collected by solid-liquid separation. Ammonia water was added to the liquid to adjust the pH value to 2.0. The liquid was heated to 100 ° C. 40 kg of crystalline iron phosphate was added and stirred for 2 hours (400 r / min). The solid was collected by solid-liquid separation to obtain wet iron phosphate. The wet iron phosphate was washed and dried at 150 ° C for 1 hour to obtain battery-grade iron phosphate dihydrate with a yield of 97.2%. The lithium carbonate prepared above was tested by atomic emission spectrometry (ICP). The contents of its impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were all less than 10 ppm. The impurity SO4 was analyzed by infrared spectroscopy. 2- PO4 3- The contents of lithium carbonate are 300ppm and 380ppm respectively; after chemical titration analysis, the lithium carbonate content is 99.63%.

[0179] The manganese phosphate prepared above was tested by atomic emission spectrometry (ICP), and the contents of the impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron were all less than 10 ppm.

[0180] The iron phosphate prepared above was tested by atomic emission spectrometry (ICP), and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were all less than 10ppm; the impurity SO4 2- The content is 50ppm; after chemical titration analysis, Fe / P is 0.972.

[0181] Example 3

[0182] (1) At a flow rate of 1.5 m 3 In an oxygen atmosphere at 1000 rpm / h, 2000 kg of waste lithium manganese iron phosphate powder, 1600 kg of nitric acid, and 16,000 kg of pure water were mixed. 200 kg of an oxidizing agent, MnPO₄·H₂O, was added, the pH was adjusted to 7.0, and the mixture was reacted at 50°C for 6 hours. The endpoint pH was measured to be 6.0, yielding a first mixed solution. The first mixed solution was subjected to solid-liquid separation to obtain a first filtrate and a first filter residue.

[0183] (2) In a sealed container, 1200 kg of sodium carbonate was mixed with the first filtrate, and carbon dioxide was introduced while controlling the carbon dioxide oxygen partial pressure to 2.0 MPa. The mixture was reacted at 25°C for 1 hour, and the liquid was collected by solid-liquid separation to obtain a purified lithium solution. The purified lithium solution was pyrolyzed at 100°C for 2 hours, and the solid was collected by solid-liquid separation. The solid was dried at 85°C for 5 hours to obtain battery-grade lithium carbonate with a yield of 97.2%.

[0184] (3) The first filter residue, about 200 Kg of nitric acid, 800 Kg of phosphoric acid and 30000 Kg of pure water are mixed to adjust the pH value to 2.5, and reacted at 60°C for 4 h. The terminal pH value is 3.2, and a second mixed solution is obtained. The second mixed solution is subjected to solid-liquid separation to obtain a second filtrate and a second filter residue.

[0185] (4) The second filtrate is reacted with 100 Kg of manganese dioxide at 25°C for 0.5 h, and subjected to solid-liquid separation to collect the liquid. Ammonia water is added to the liquid to adjust the pH value to 4.5, and the liquid is reacted at 50°C for 2 h. The solid is collected by solid-liquid separation, washed, and dried at 100°C for 2 h to obtain high-purity manganese phosphate heptahydrate, with a yield of 96.5%.

[0186] (5) The second filter residue, 200 Kg of sulfuric acid, 1200 Kg of phosphoric acid and 4000 Kg of pure water are mixed, stirred and dissolved at 50°C for 2 h. The liquid is collected by solid-liquid separation, ammonia water is added to the liquid to adjust the pH value to 2.5, and the liquid is heated to 100°C. 50 Kg of crystalline iron phosphate is added to the liquid for 2 h (400 r / min), and the solid is collected by solid-liquid separation to obtain wet iron phosphate. The wet iron phosphate is washed and dried at 150°C for 1 h to obtain battery-grade iron phosphate dihydrate, with a yield of 97.2%.

[0187] The lithium carbonate prepared above is detected by atomic emission spectrometry (ICP), and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead are all less than 10 ppm. The contents of impurities SO4 2- and PO4 3- are 200 ppm and 450 ppm respectively by infrared spectrometry analysis. The content of lithium carbonate is 99.60% by chemical titration analysis.

[0188] The manganese phosphate prepared above is detected by atomic emission spectrometry (ICP), and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron are all less than 10 ppm.

[0189] The iron phosphate prepared above is detected by atomic emission spectrometry (ICP), and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead are all less than 10 ppm. The content of impurity SO4 2- is 120 ppm by infrared spectrometry analysis. The Fe / P ratio is 0.972 by chemical titration analysis.

[0190] Example 4

[0191] (1) The flow rate of the water is 0.3 m 3Under oxygen atmosphere of 2.0 MPa, 200 Kg of lithium iron manganese phosphate waste powder, 120 Kg of sulfuric acid, 40 Kg of hydrochloric acid and 1200 Kg of pure water were mixed, 60 Kg of oxidant Mn3(PO4)2·3H2O was added, the pH value was adjusted to 5.0, and reaction was carried out at 90 ℃ for 6 h. The final pH value was 7.0, and a first mixed solution was obtained. The first mixed solution was subjected to solid-liquid separation to obtain a first filtrate and a first residue.

[0192] (2) In a closed container, 120 Kg of sodium bicarbonate was mixed with the first filtrate, carbon dioxide was introduced and the oxygen partial pressure of carbon dioxide was controlled to be 2.0 MPa, reaction was carried out at 50 ℃ for 1 h, and the liquid was collected by solid-liquid separation to obtain purified lithium liquid. The purified lithium liquid was pyrolyzed at 100 ℃ for 2 h, the solid was collected by solid-liquid separation, and the solid was dried at 100 ℃ for 1.5 h to obtain battery-grade lithium carbonate, with a yield of 97.5%.

[0193] (3) The first residue, about 100 Kg of phosphoric acid and 600 Kg of pure water were mixed, the pH value was adjusted to 2.5, and reaction was carried out at 50 ℃ for 4 h. The final pH value was 2.55, and a second mixed solution was obtained. The second mixed solution was subjected to solid-liquid separation to obtain a second filtrate and a second residue.

[0194] (4) The second filtrate was reacted with 4 Kg of manganese dioxide at 25 ℃ for 0.5 h, and the liquid was collected by solid-liquid separation. Ammonia water was added to the liquid to adjust the pH value to 4.5, and then the liquid was reacted at 50 ℃ for 2 h. The solid was collected by solid-liquid separation. The solid was washed and dried at 100 ℃ for 2 h to obtain high-purity manganese phosphate heptahydrate, with a yield of 96.5%.

[0195] (5) The second residue, 40 Kg of sulfuric acid, 260 Kg of phosphoric acid and 2000 Kg of pure water were mixed, and stirred and dissolved at 60 ℃ for 2 h. The liquid was collected by solid-liquid separation. Ammonia water was added to the liquid to adjust the pH value to 2.5. The liquid was heated to 100 ℃, 10 Kg of crystalline iron phosphate was added and stirred for 2 h (400 r / min). The solid was collected by solid-liquid separation to obtain wet iron phosphate. The wet iron phosphate was washed and dried at 150 ℃ for 1.5 h to obtain battery-grade iron phosphate dihydrate, with a yield of 97.0%. 2- The lithium carbonate prepared above was detected by atomic emission spectrometry (ICP), and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were all less than 10 ppm. The contents of impurities SO4 3- and PO4 were 200 ppm by infrared spectroscopy analysis. The content of lithium carbonate was 99.63% by chemical titration analysis.

[0196] The manganese phosphate prepared above was detected by atomic emission spectrometry (ICP), and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron were all less than 10 ppm.

[0197] The prepared iron phosphate was detected by atomic emission spectrometry (ICP), and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm; the content of impurity SO4 2- was 120 ppm by infrared spectroscopy analysis; and Fe / P was 0.972 by chemical titration analysis.

[0198] Example 5

[0199] The whole-component recovery of the waste old lithium manganese iron phosphate positive electrode material was carried out according to the same steps and processes of Example 1, except that the amount of manganese phosphate hydrate was 0.5:1 relative to the weight of the waste old lithium manganese iron phosphate positive electrode material, and other operations were the same as those of Example 1.

[0200] The yield of the prepared lithium carbonate was 97.6%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm by atomic emission spectrometry (ICP); the contents of SO4 2- and PO4 3- were 300 ppm by chemical analysis, and the content of lithium carbonate was 99.61%.

[0201] The yield of the prepared manganese phosphate was 96.9%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron were less than 10 ppm.

[0202] The yield of the prepared iron phosphate was 97.4%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm by atomic emission spectrometry (ICP); the content of impurity SO4 2- was 300 ppm by infrared spectroscopy analysis; and Fe / P was 0.972 by chemical titration analysis.

[0203] Example 6

[0204] The whole-component recovery of the waste old lithium manganese iron phosphate positive electrode material was carried out according to the same steps and processes of Example 1, except that the amount of manganese phosphate hydrate was 0.05:1 relative to the weight of the waste old lithium manganese iron phosphate positive electrode material, and other operations were the same as those of Example 1.

[0205] The yield of the prepared lithium carbonate was 96.9%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm by atomic emission spectrometry (ICP); the content of SO4 2- was 300 ppm by chemical analysis, the content of PO4 3- was 850 ppm, and the content of lithium carbonate was 99.53%.

[0206] The yield of the prepared manganese phosphate was 96.7%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, and iron were less than 10 ppm.

[0207] The yield of the prepared iron phosphate was 97.4%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were less than 10 ppm by atomic emission spectrometry (ICP); the content of SO4 2- was 300 ppm by infrared spectroscopy analysis; and the Fe / P ratio was 0.972 by chemical titration analysis.

[0208] Example 7

[0209] The full-component recovery of the waste old manganese iron lithium phosphate positive electrode material was performed according to the same steps and processes of Example 1, except that the oxygen-containing gas was not introduced, but was directly performed in an air atmosphere; and other operations were the same as those in Example 1.

[0210] The yield of the prepared lithium carbonate was 82.6%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were less than 10 ppm by atomic emission spectrometry (ICP); the contents of SO4 2- and PO4 3- were 400 ppm by chemical analysis, and the content of lithium carbonate was 99.59%.

[0211] The yield of the prepared manganese phosphate was 96.0%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, and nickel were less than 10 ppm, and the content of iron was 980 ppm.

[0212] The yield of the prepared iron phosphate was 95.3%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were less than 10 ppm by atomic emission spectrometry (ICP); the content of SO4 2- was 300 ppm by infrared spectroscopy analysis; and the Fe / P ratio was 0.972 by chemical titration analysis.

[0213] Example 8

[0214] The full-component recovery of the waste old manganese iron lithium phosphate positive electrode material was performed according to the same steps and processes of Example 1, except that the flow rate of the oxygen-containing gas was 0.1 m3 / h; and other operations were the same as those in Example 1.

[0215] The yield of the prepared lithium carbonate was 90.1%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were less than 10 ppm by atomic emission spectrometry (ICP); the contents of SO4 2- and PO4 3-The content of SO4

[0216] The prepared manganese phosphate has a yield of 96.3%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron are all less than 10 ppm.

[0217] The prepared iron phosphate has a yield of 96.7%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead are all less than 10 ppm by atomic emission spectrometry (ICP); the content of SO4 2- is 300 ppm by infrared spectroscopy; and Fe / P is 0.975 by chemical titration analysis.

[0218] Example 9

[0219] The full-component recovery of the waste old manganese iron lithium phosphate positive electrode material is carried out according to the same steps and processes of Example 1, except that the flow rate of the oxygen-containing gas is 0.5 m3 / h; and the other operations are the same as those in Example 1.

[0220] The prepared lithium carbonate has a yield of 97.6%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead are all less than 10 ppm by atomic emission spectrometry (ICP); the contents of SO4 2- and PO4 3- are 380 ppm by chemical analysis; and the content of lithium carbonate is 99.65%.

[0221] The prepared manganese phosphate has a yield of 96.9%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron are all less than 10 ppm.

[0222] The prepared iron phosphate has a yield of 97.2%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead are all less than 10 ppm by atomic emission spectrometry (ICP); the content of SO4 2- is 300 ppm by infrared spectroscopy; and Fe / P is 0.975 by chemical titration analysis.

[0223] Example 10

[0224] The full-component recovery of the waste old manganese iron lithium phosphate positive electrode material is carried out according to the same steps and processes of Example 1, except that the reaction temperature in step (1) is 25°C; and the other operations are the same as those in Example 1.

[0225] The prepared lithium carbonate has a yield of 95.9%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead are all less than 10 ppm by atomic emission spectrometry (ICP); the contents of SO42- and PO4 3- The content of SO4 2- was 300 ppm, and the content of lithium carbonate was 99.57%.

[0226] The yield of the prepared manganese phosphate was 95.8%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, and iron were all less than 10 ppm.

[0227] The yield of the prepared iron phosphate was 97.0%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were all less than 10 ppm by atomic emission spectrometry (ICP). The content of SO4 2- was 300 ppm by infrared spectroscopy analysis, and Fe / P was 0.975 by chemical titration analysis.

[0228] Example 11

[0229] The full-component recovery of the waste old lithium manganese iron phosphate positive electrode material was performed according to the same steps and processes of Example 1, except that the mass ratio of the second acid to the waste old lithium manganese iron phosphate positive electrode material was 0.1:1, and the other operations were the same as in Example 1.

[0230] The yield of the prepared lithium carbonate was 97.6%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were all less than 10 ppm by atomic emission spectrometry (ICP). The content of SO4 3- was 300 ppm by chemical analysis, and the content of lithium carbonate was 99.65%.

[0231] The yield of the prepared manganese phosphate was 90.3%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, and iron were all less than 10 ppm.

[0232] The yield of the prepared iron phosphate was 97.4%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, zinc, cadmium, and lead were all less than 10 ppm by atomic emission spectrometry (ICP), and the content of manganese was 1250 ppm. The content of SO4 2- was 300 ppm by infrared spectroscopy analysis, and Fe / P was 0.975 by chemical titration analysis.

[0233] Example 12

[0234] The full-component recovery of the waste old lithium manganese iron phosphate positive electrode material was performed according to the same steps and processes of Example 1, except that the mass ratio of the second acid to the waste old lithium manganese iron phosphate positive electrode material was 0.1:1, and the other operations were the same as in Example 1.

[0235] The yield of the prepared lithium carbonate is 97.6%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead are less than 10 ppm as detected by atomic emission spectrometry (ICP); the contents of SO4 2- and PO4 3- are 300 ppm as detected by chemical analysis, and the content of lithium carbonate is 99.65%.

[0236] The yield of the prepared manganese phosphate is 97.0%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt and nickel are less than 10 ppm.

[0237] The yield of the prepared iron phosphate is 97.2%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead are less than 10 ppm as detected by atomic emission spectrometry (ICP); the content of SO4 2- is 300 ppm as detected by infrared spectrometry; and the Fe / P ratio is 0.975 as detected by chemical titration analysis.

[0238] Example 13

[0239] The full-component recovery of the waste old manganese iron lithium phosphate positive electrode material is performed according to the same steps and processes of Example 1, except that the mass ratio of the third acid to the waste old manganese iron lithium phosphate positive electrode material is 5:1, and the other operations are the same as in Example 1.

[0240] The yield of the prepared lithium carbonate is 97.6%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead are less than 10 ppm as detected by atomic emission spectrometry (ICP); the contents of SO4 2- and PO4 3- are 300 ppm as detected by chemical analysis, and the content of lithium carbonate is 99.65%.

[0241] The yield of the prepared manganese phosphate is 97.2%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron are less than 10 ppm.

[0242] The yield of the prepared iron phosphate is 94.1%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead are less than 10 ppm as detected by atomic emission spectrometry (ICP); the content of SO4 2- is 300 ppm as detected by infrared spectrometry; and the Fe / P ratio is 0.975 as detected by chemical titration analysis.

[0243] Example 14

[0244] The whole component recovery of the waste old lithium manganese iron phosphate positive material was carried out according to the same steps and processes of example 1, except that the ratio of the added amount of the seed crystal to the weight of the waste old lithium manganese iron phosphate positive material was 0.01:1; and other operations were the same as those in example 1.

[0245] The yield of the prepared lithium carbonate was 97.6%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm detected by atomic emission spectrometry (ICP); the content of SO4 2- and PO4 3- was 300 ppm, and the content of lithium carbonate was 99.65% detected by chemical analysis.

[0246] The yield of the prepared manganese phosphate was 97.2%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron were less than 10 ppm.

[0247] The yield of the prepared iron phosphate was 96.3%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm detected by atomic emission spectrometry (ICP); the content of SO4 2- was 300 ppm detected by infrared spectrometry; and the Fe / P was 0.975 detected by chemical titration analysis.

[0248] Example 15

[0249] The whole component recovery of the waste old lithium manganese iron phosphate positive material was carried out according to the same steps and processes of example 1, except that the ratio of the added amount of the seed crystal to the weight of the waste old lithium manganese iron phosphate positive material was 0.2:1; and other operations were the same as those in example 1.

[0250] The yield of the prepared lithium carbonate was 97.6%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm detected by atomic emission spectrometry (ICP); the content of SO4 2- and PO4 3- was 300 ppm, and the content of lithium carbonate was 99.65% detected by chemical analysis.

[0251] The yield of the prepared manganese phosphate was 97.2%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron were less than 10 ppm.

[0252] The yield of the prepared iron phosphate was 97.5%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm detected by atomic emission spectrometry (ICP); the content of SO4 2- was 300 ppm detected by infrared spectrometry; and the Fe / P was 0.965 detected by chemical titration analysis.

[0253] Comparative Example 1

[0254] The full-component recovery of the waste old lithium manganese iron phosphate positive electrode material was carried out according to the same steps and processes of Example 1, except that the pH value was adjusted to 3 in the S1 step, and the other operations were the same as those of Example 1.

[0255] The yield of the lithium carbonate prepared above was 96.1%, and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm by atomic emission spectrometry (ICP). The content of SO4 2- was 300 ppm by chemical analysis, and the content of PO4 3- was 3900 ppm. The content of lithium carbonate was 99.29% by chemical analysis.

[0256] The yield of the manganese phosphate prepared was 81.9%, and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron were less than 10 ppm.

[0257] The yield of the iron phosphate prepared above was 97.0%, and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm by atomic emission spectrometry (ICP). The content of SO4 2- was 300 ppm by infrared spectroscopy analysis. The Fe / P ratio was 0.972 by chemical titration analysis.

[0258] Comparative Example 2

[0259] The full-component recovery of the waste old lithium manganese iron phosphate positive electrode material was carried out according to the same steps and processes of Example 1, except that the manganese phosphate hydrate was replaced by hydrogen peroxide in the S2 step, and the other operations were the same as those of Example 1.

[0260] The yield of the lithium carbonate prepared above was 97.2%, and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm by atomic emission spectrometry (ICP). The content of SO4 2- was 300 ppm by chemical analysis, and the content of PO4 3- was 1400 ppm. The content of lithium carbonate was 99.43% by chemical analysis.

[0261] The yield of the manganese phosphate prepared was 96.6%, and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron were less than 10 ppm.

[0262] The yield of the iron phosphate prepared above was 97.0%, and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm by atomic emission spectrometry (ICP). The content of SO42- The content of SO4was 300 ppm; and Fe / P was 0.972 by chemical titration analysis.

[0263] Comparative Example 3

[0264] The whole-component recovery of the waste old lithium manganese iron phosphate positive electrode material was performed according to the same steps and processes of Example 1, except that no manganese phosphate hydrate was used in the S2 step, and other operations were the same as in Example 1.

[0265] The yield of the lithium carbonate prepared above was 71.9%, and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were all less than 10 ppm by atomic emission spectrometry (ICP); the content of SO4was 300 ppm by chemical analysis; and the content of PO4was 6500 ppm by chemical analysis. 2- The content of SO4was 300 ppm; and Fe / P was 0.972 by chemical titration analysis. 3- The content of PO4was 6500 ppm, and the content of lithium carbonate was 99.15%.

[0266] The yield of the manganese phosphate prepared was 95.9%, and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, and cobalt were all less than 10 ppm, and the content of iron was 1250 ppm.

[0267] The yield of the iron phosphate prepared above was 90.3%, and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were all less than 10 ppm by atomic emission spectrometry (ICP); the content of SO4was 300 ppm by infrared spectroscopy analysis; and Fe / P was 0.972 by chemical titration analysis. 2- The content of SO4was 300 ppm; and Fe / P was 0.972 by chemical titration analysis.

[0268] Comparative Example 4

[0269] The whole-component recovery of the waste old lithium manganese iron phosphate positive electrode material was performed according to the same steps and processes of Example 1, except that an excess of acid was added in the initial stage so that the pH value of the second mixed solution was 2.0 after the reaction ended, and other operations were the same as in Example 1.

[0270] The yield of the lithium carbonate prepared above was 97.2%, and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium, and lead were all less than 10 ppm by atomic emission spectrometry (ICP); the content of SO4was 300 ppm by chemical analysis; and the content of PO4was 250 ppm by chemical analysis. 2- The content of SO4was 300 ppm; and Fe / P was 0.972 by chemical titration analysis. 3- The content of PO4was 250 ppm, and the content of lithium carbonate was 99.63%.

[0271] The yield of the manganese phosphate prepared was 95.3%, and the contents of impurities sodium, magnesium, silicon, potassium, calcium, chromium, and cobalt were all less than 10 ppm, and the content of iron was 1470 ppm.

[0272] The yield of the prepared iron phosphate was 93.2%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm by atomic emission spectrometry (ICP); the content of impurity SO4 2- was 300 ppm by infrared spectroscopy analysis; and Fe / P was 0.970 by chemical titration analysis.

[0273] Comparative Example 5

[0274] The whole-component recovery of the waste old lithium manganese iron phosphate positive electrode material was performed according to the same steps and processes of Example 1, except that the acid was insufficiently added in the initial stage, and no supplement was performed in the middle, so that the pH value of the second mixed solution was 4.8 after the reaction, and the other operations were the same as those in Example 1.

[0275] The yield of the prepared lithium carbonate was 97.6%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm by atomic emission spectrometry (ICP); the contents of SO4 2- and PO4 3- were 300 ppm by chemical analysis, and the content of lithium carbonate was 99.65%.

[0276] The yield of the prepared manganese phosphate was 18.2%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel and iron were less than 10 ppm.

[0277] The yield of the prepared iron phosphate was 97.5%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, zinc, cadmium and lead were less than 10 ppm by atomic emission spectrometry (ICP), and the content of manganese was 3850 ppm; the content of impurity SO4 2- was 300 ppm by infrared spectroscopy analysis; and Fe / P was 0.931 by chemical titration analysis.

[0278] Comparative Example 6

[0279] The whole-component recovery of the waste old lithium manganese iron phosphate positive electrode material was performed according to the same steps and processes of Example 1, except that the waste old lithium manganese iron phosphate positive electrode material and manganese phosphate hydrate were reacted in a closed atmosphere, so that the oxygen content was insufficient after 1 h after the reaction started, and the reaction was performed in an oxygen-free environment to the reaction endpoint. The other operations were the same as those in Example 1.

[0280] The yield of the prepared lithium carbonate was 91.8%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, manganese, zinc, cadmium and lead were less than 10 ppm by atomic emission spectrometry (ICP); the contents of SO4 2- and PO4 3-The content of lithium carbonate is 99.63%.

[0281] The yield of the prepared manganese phosphate is 96.2%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt and nickel are all less than 10 ppm, and the content of iron is 90 ppm.

[0282] The yield of the above prepared iron phosphate is 93.4%, and the contents of impurities such as sodium, magnesium, silicon, potassium, calcium, chromium, cobalt, nickel, zinc, cadmium and lead are all less than 10 ppm, and the content of manganese is 3850 ppm, as detected by atomic emission spectrometry (ICP); and the content of SO4 2- The content of lithium carbonate is 99.63%.

[0283] Result analysis:

[0284] The carbonic acid lithium, manganese phosphate and iron phosphate are recovered in high yield according to the embodiments of the present application, and the recovered products have high quality, high purity and low impurity content, and can be reused for battery production, realizing resource recycling and utilization.

[0285] According to the comparison results of the embodiments and the comparative examples, it is found that the oxygen blowing in S1 is a very critical step. For example, compared with example 1, the purity of lithium carbonate and manganese phosphate is reduced in example 7 when the reaction is carried out in air, and the purity of each product is relatively reduced in example 8 when the oxygen flow rate is 0.1 m3 / h. In addition, in order to obtain better purity, it is also necessary to control the reaction conditions and the material ratio of each step. For example, compared with example 1, the yield of lithium carbonate and manganese phosphate is slightly reduced in example 10 when the reaction temperature in S1 is 25℃, the purity of lithium carbonate and manganese phosphate is slightly reduced, the yield of manganese phosphate is slightly reduced in example 11 when the mass ratio of the second acid to the waste lithium manganese iron phosphate positive material in S1 is 0.1:1, and the purity of iron phosphate is slightly reduced, the purity of manganese phosphate is slightly reduced in example 12 when the mass ratio of the second acid to the waste lithium manganese iron phosphate positive material in S2 is 0.1:1, the yield of iron phosphate is slightly reduced in example 13 when the mass ratio of the third acid to the waste lithium manganese iron phosphate positive material in S3 is 5:1, and the yield of iron phosphate is slightly reduced in example 14 when the addition amount of the seed crystal in S3 is 0.01:1 relative to the weight of the waste lithium manganese iron phosphate positive material.

[0286] The comparison results of the various embodiments and the comparative examples show that the yield and purity of the comparative examples are partially or totally unsatisfactory, and cannot achieve the purpose of ensuring high recovery rate and purity of the products in the present application. For example, in Comparative Example 1, the yield and purity of lithium carbonate are low in the S1 step of reducing the pH value, and the yield of manganese phosphate is also low. In Comparative Example 2, the purity of lithium carbonate is low in the S2 step of replacing manganese phosphate hydrate with hydrogen peroxide. In Comparative Example 3, the yield of the three products is low, and the purity of lithium carbonate and manganese phosphate is low in the S2 step of not using manganese phosphate hydrate. In Comparative Example 4, the yield of ferric phosphate is low, and the purity of manganese phosphate is low in the S4 step of pH value being 2.0. In Comparative Example 5, the yield of manganese phosphate is greatly reduced, and the purity of ferric phosphate is greatly reduced in the S2 step of insufficient acid addition in the initial stage and no intermediate addition. In Comparative Example 6, the yield of lithium carbonate is greatly reduced, the yield and purity of manganese phosphate are slightly reduced, and the yield of ferric phosphate is greatly reduced in the S1 step of reacting the waste and old manganese iron lithium phosphate positive electrode material with manganese phosphate hydrate in a closed atmosphere, so that the oxygen content is insufficient after 1 h of reaction, and the reaction is carried out in an oxygen-free environment to the end of the reaction. The purpose of ensuring high recovery rate of the products in the present application is not achieved.

[0287] The above results also reveal that there is an inherent correlation between the content of impurity phosphate and the purity of lithium carbonate. When the content of phosphate impurity is controlled to be relatively appropriate, the purity of lithium carbonate is high, and the recovery rate is also relatively ideal. This may be related to the specific process of the oxidant manganese phosphate hydrate participating in the reaction. In our speculation, this specific oxide is extremely likely to have the dual functions of oxidant and inducer of crystallization. While participating in the oxidation of the waste powder, it can make a small amount of dissolved manganese and phosphate components remain in the form of precipitate in the slag, thereby helping us to achieve high recovery rate and high purity of the target product.

Claims

1. A method for recycling all components of a waste lithium iron manganese phosphate cathode material, characterized in that, The method comprises the following steps: reacting the waste lithium iron manganese phosphate positive electrode material and an oxidizing agent in an oxygen-containing gas atmosphere to obtain a first mixed solution, and performing solid-liquid separation on the first mixed solution to obtain a first filtrate and a first residue, wherein the pH value of the first mixed solution is controlled to be 4-7, and the oxidizing agent comprises manganese phosphate hydrate; reacting the first filtrate with carbon dioxide to obtain lithium carbonate; reacting the first residue with an acid to obtain a second mixed solution, and performing solid-liquid separation on the second mixed solution to obtain a second filtrate and a second residue, wherein the pH value of the second mixed solution is controlled to be 2.5-4; reacting the second filtrate with manganese dioxide to obtain manganese phosphate; dissolving the second residue in an acid and performing crystallization to obtain iron phosphate.

2. The recycling method according to claim 1, characterized in that, The method comprises the following steps: reacting the waste lithium iron manganese phosphate positive electrode material, a first acid, first water and an oxidizing agent in an oxygen-containing gas atmosphere at a first temperature for a first time to obtain the first mixed solution; The flow rate of the oxygen-containing gas is 0.3m 3 / h~0.5m 3 / h, the first temperature is 50℃~95℃, and the first time is 3h~10h.

3. The recycling method according to claim 2, characterized in that, the oxygen-containing gas contains 20-100% oxygen molecules by volume, and the oxygen molecules comprise oxygen gas molecules and ozone molecules.

4. The recycling method according to claim 2, characterized in that, The manganese phosphate hydrate comprises at least one of MnPO4·H2O and Mn3(PO4)2·7H2O.

5. The recycling method of claim 2, wherein, The first acid comprises at least one of hydrochloric acid, sulfuric acid and nitric acid.

6. The recycling method of claim 2, wherein, The weight ratio of the waste lithium iron manganese phosphate positive electrode material, the first acid, the first water and the oxidizing agent is 1:(0.3-0.8):(2-8):(0.10-0.30).

7. The recycling method of claim 2, wherein, After the waste lithium iron manganese phosphate positive electrode material, the first acid, the first water and the oxidizing agent are heated in the oxygen-containing gas atmosphere at the first temperature for the first time, the pH value of the reaction solution is detected; if the pH value of the reaction solution is 4-7, the reaction solution is collected to obtain the first mixed solution; if the pH value of the reaction solution is not 4-7, a pH value adjusting agent is added to the reaction solution in batches until the pH value of the reaction solution is 4-7, and the reaction solution is collected to obtain the first mixed solution.

8. The recycling method of claim 1, wherein, The method comprises the following steps: reacting the first filtrate with carbon dioxide to obtain lithium carbonate, which comprises the following steps: reacting the first filtrate, a first base and carbon dioxide in a sealed container at a second temperature for a second time, and performing solid-liquid separation to collect a liquid to obtain purified lithium liquid; pyrolyzing the purified lithium liquid to obtain the lithium carbonate; 9. The recycling method according to claim 8, characterized in that, wherein the partial pressure of the carbon dioxide in the sealed container is 1-2 MPa, the second temperature is 25-50 DEG C, and the second time is 1-5 h.

10. The recycling method of claim 8, wherein, The first base comprises at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate.

11. The recycling method of claim 8, wherein, The weight ratio of the first base to the waste lithium iron manganese phosphate positive electrode material is (0.2-0.6):

1. The method comprises the following steps: pyrolyzing the purified lithium liquid at a third temperature for a third time, performing solid-liquid separation to collect a solid to obtain the lithium carbonate; 12. The recycling method of claim 1, wherein, wherein the third temperature is 85-100 DEG C, and the third time is 1.5-4 h. The method comprises the following steps: reacting the first residue, a second acid and second water at a fourth temperature for a fourth time to obtain the second mixed solution; The fourth temperature is 25-60 DEG C, and the fourth time is 2.5-4 hours.

13. The recycling method of claim 12, wherein, The second acid comprises at least one of sulfuric acid, nitric acid and phosphoric acid.

14. The recycling method of claim 12, wherein, The mass ratio of the waste old lithium manganese iron phosphate positive electrode material, the second acid and the second water is 1:(0.15-0.5):(3-15).

15. The recycling method of claim 12, wherein, The first residue, the second acid and the second water are heated at a fourth reaction temperature for a fourth reaction time, and the pH value of the reaction solution is detected; If the pH value of the reaction solution is 2.5-4, the reaction solution is collected to obtain the second mixed solution; If the pH value of the reaction solution is not 2.5-4, a pH value adjusting agent is added into the reaction solution in batches until the pH value of the reaction solution is 2.5-4, and the reaction solution is collected to obtain the second mixed solution.

16. The recycling method of claim 1, wherein, The second filtrate and manganese dioxide are reacted to obtain manganese phosphate, comprising: The second filtrate and the manganese dioxide are reacted at a fifth temperature for a fifth time, and the filtrate is collected by solid-liquid separation; The filtrate and a second base are mixed, reacted at a sixth temperature for a sixth time, and the solid is collected by solid-liquid separation to obtain the manganese phosphate; The fifth temperature is 25-50 DEG C, the fifth time is 0.5-1.5 hours, the sixth temperature is 25-50 DEG C, and the sixth time is 2-5 hours.

17. The recycling method of claim 16, wherein, The second base comprises at least one of ammonia water or ammonium carbonate.

18. The recycling method of claim 16, wherein, The mass ratio of the manganese dioxide to the waste old lithium manganese iron phosphate positive electrode material is (0.01-0.05):

1.

19. The recycling method of claim 1, wherein, The second residue is dissolved in an acid, and crystallization is carried out to obtain iron phosphate, comprising: The second residue, a third acid and a third water are reacted at a seventh temperature for a seventh time, and the filtrate is collected by solid-liquid separation; After the pH value of the filtrate is adjusted to 2-3, seed crystals are added for crystallization to obtain the iron phosphate; The seventh temperature is 25-60 DEG C, and the seventh time is 2.0-4.0 hours.

20. The recycling method of claim 19, wherein, The third acid comprises at least one of hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid.

21. The recycling method of claim 19, wherein, The seed crystals comprise at least one of amorphous iron phosphate, amorphous hydroxy iron phosphate, crystalline iron phosphate and crystalline hydroxy iron phosphate.

22. The recycling method of claim 19, wherein, The mass ratio of the third acid, the third water and the waste old lithium manganese iron phosphate positive electrode material is (0.5-1.5):(3-10):

1.

23. The recycling method of claim 19, wherein, The ratio of the amount of the seed crystals to the weight of the waste old lithium manganese iron phosphate positive electrode material is (0.05-0.1):

1.

24. The recycling method of claim 19, wherein, After the pH value of the filtrate is adjusted to 2-3, seed crystals are added for crystallization to obtain the iron phosphate, comprising: After the pH value of the filtrate is adjusted to 2-3, the filtrate is heated to 80-100 DEG C, the seed crystals are added, and stirring is carried out for 2-4 hours to obtain the iron phosphate.

25. The recycling method of claim 24, wherein, The stirring speed is 250-500 r / min.

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