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CN115072688B - Method for recycling all components of waste lithium iron phosphate battery - Google Patents

Method for recycling all components of waste lithium iron phosphate battery Download PDF

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CN115072688B
CN115072688B CN202210990175.6A CN202210990175A CN115072688B CN 115072688 B CN115072688 B CN 115072688B CN 202210990175 A CN202210990175 A CN 202210990175A CN 115072688 B CN115072688 B CN 115072688B
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lithium
solution
battery
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CN115072688A (en
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孙留根
张正阳
杨玮娇
杨永强
韦其晋
程俊武
张胜梅
张逸飞
马鑫铭
张义
彭煜华
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BGRIMM Technology Group Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/37—Phosphates of heavy metals
    • C01B25/375—Phosphates of heavy metals of iron
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D15/00—Lithium compounds
    • C01D15/08—Carbonates; Bicarbonates
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
    • C22B26/10—Obtaining alkali metals
    • C22B26/12—Obtaining lithium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/006—Wet processes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/54—Reclaiming serviceable parts of waste accumulators
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/11—Powder tap density
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/84—Recycling of batteries or fuel cells

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Abstract

The invention belongs to the technical field of waste battery recovery, and particularly relates to a full-component recovery method of a waste lithium iron phosphate battery, which comprises the following steps: (1) Sorting and pretreating the full battery material to obtain battery black powder; (2) Mixing the battery black powder with the second-stage leaching solution for two-stage leaching; (3) The two-stage leaching residue is used for preparing negative graphite powder; (4) Purifying and removing impurities from the first-stage leaching solution to obtain second copper powder, purified slag and purified liquid; (5) Adding a phosphorus source and/or an iron source into the purified solution, reacting with an oxidant, and filtering to obtain a precipitation mother solution and precipitation slag; (6) the precipitation mother liquor is circularly returned to the step (2); (7) Washing, aging and calcining the obtained precipitation slag to obtain anhydrous iron phosphate; (8) And (3) carrying out impurity removal and carbonation reaction on the precipitation mother liquor with the lithium concentration of more than 20g/L to prepare lithium carbonate. The invention can improve the leaching rate and the recovery rate of recovered elements, reduce the leaching rate of impurities and reduce energy consumption.

Description

Method for recycling all components of waste lithium iron phosphate battery
Technical Field
The invention belongs to the technical field of waste battery recovery, and particularly relates to a full-component recovery method of a waste lithium iron phosphate battery.
Background
The advantages of long service life, high charge-discharge efficiency, low manufacturing cost, good safety and the like are achieved, so that LiFePO in the energy storage equipment 4 The demand for (LFP) type batteries has increased significantly. Lithium iron phosphate batteries are large in scale and can have negative environmental impact due to improper handling, which raises concerns about proper disposal after decommissioning. Therefore, recycling of waste LFP batteries is receiving much attention.
The recovery of waste LFP batteries mainly comprises two methods: pyrometallurgy (1) and hydrometallurgy (2). The fire method generates toxic tail gas due to the decomposition of organic matters at high temperature, and is not favorable for the environment; the method with the widest application and the best effect is wet recovery. The wet recovery mainly comprises selective recovery (preferential lithium extraction) and total recovery. The selective recovery mainly aims at the recovery of lithium, the oxidant is added during leaching to precipitate iron phosphorus in slag, a large amount of acid is additionally added during subsequent recovery of iron phosphate, and a large amount of alkali is correspondingly consumed to adjust the pH value. The comprehensive utilization rate of the full recovery process is high, however, the prior art has the following defects: the recovery rate of elements such as iron, phosphorus, lithium and the like is low, the leaching rate of impurities is high, the acid consumption is high, and the energy consumption is high.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a method for recovering all components of waste lithium iron phosphate batteries, which can improve the recovery rate of Fe, P and Li elements, reduce the impurity leaching rate and reduce the energy consumption, and can also adopt cheap waste lithium iron phosphate batteries with high impurity content as raw materials to prepare products such as battery-grade iron phosphate, battery-grade lithium carbonate and qualified negative electrode graphite powder precursors, thereby realizing the comprehensive recovery of all components.
In order to achieve the aim, the invention provides a method for recovering all components of waste lithium iron phosphate batteries, which comprises the following steps:
(1) Sorting and pretreating the raw materials of the full battery material to obtain battery black powder, first copper powder and a sorting solution;
(2) Mixing battery black powder and the second-stage leaching solution for first-stage leaching, filtering to obtain a first-stage leaching solution and first-stage leaching residues, mixing the first-stage leaching residues and an acid solution for second-stage leaching, and filtering to obtain a second-stage leaching solution and second-stage leaching residues; wherein the second-stage leachate is replaced by an acid solution in the first extraction process;
(3) Using the two-stage leaching residue obtained in the step (2) to prepare negative graphite powder;
(4) Purifying and removing impurities from the first-stage leaching solution obtained in the step (2) to obtain second copper powder, purified slag and purified liquid;
(5) Mixing the purified liquid with a phosphorus source and/or an iron source and an optional oxidant, reacting, and filtering to obtain a precipitation mother liquid and precipitation slag;
(6) The precipitation mother liquor is circularly returned to the step (2), and the two-stage leaching is carried out together with the first-stage leaching residue, wherein the circulating times are more than two times until the concentration of lithium in the precipitation mother liquor obtained in the step (5) in a circulating manner is more than 20 g/L;
(7) Washing and aging the precipitation slag obtained in the step (5), filtering to obtain ferric phosphate dihydrate, and then calcining to obtain anhydrous ferric phosphate;
(8) And (4) carrying out impurity removal and carbonation reaction on the precipitation mother liquor with the lithium concentration of more than 20g/L obtained in the step (6) in a circulating manner to prepare lithium carbonate.
In some preferred embodiments, in step (2), the molar amount of the acid in the acid solution is 1.4 to 1.9 times the molar amount of the iron in the battery black powder.
In some preferred embodiments, the acid in the acid solution is selected from sulfuric acid and/or hydrochloric acid.
In some preferred embodiments, in step (2), the conditions of the primary leaching and the secondary leaching each independently satisfy: the temperature is 20-40 ℃, the liquid-solid mass ratio is 3-5:1; and/or the leaching time is 1-3h.
In some preferred embodiments, in the step (3), the preparing of the negative electrode graphite powder includes: and (3) carrying out sulfuric acid curing roasting and acid leaching on the two-stage leaching residue obtained in the step (2) to prepare a negative electrode graphite powder precursor. The preferred scheme of the invention can obtain the negative electrode graphite powder precursor with metal impurities less than 0.1 wt%.
More preferably, in step (3), the acid leaching conditions include: the liquid-solid mass ratio is 5-15, the reaction pH value is controlled to be less than 0.5, the leaching temperature is 50-100 ℃, and the leaching time is 6-8h.
In some preferred embodiments, in step (5), the process of the reaction comprises: adjusting the molar ratio of Fe/P to 1-1.05, adding an oxidant which is 1-2 times of the theoretical oxidation dosage based on the molar amount of Fe, adding a pH regulator, controlling the pH to be 1.6-2.0, and controlling the reaction time to be 1-3h.
More preferably, the reaction is carried out in a water bath with stirring, the temperature of the water bath being 40-70 ℃, preferably with a stirring speed of 150-250rpm.
More preferably, the oxidizing agent is added slowly, and even more preferably at a rate of 0.5 to 2ml/min.
In some preferred embodiments, in step (6), the number of cycles is 2 to 4.
In some preferred embodiments, the lithium concentration in the precipitation mother liquor obtained in the recycling of step (5) is 20 to 30g/L.
In some preferred embodiments, in the step (7), the washing process comprises: and washing the mixture for several times by using washing water with the pH value of 0.5-5 in a countercurrent way under the conditions that the liquid-solid mass ratio is 20-30.
In some preferred embodiments, the aging process comprises: aging in a solution with the phosphoric acid concentration of 10-35g/L at the aging temperature of 70-90 ℃ for 3-10h, wherein the liquid-solid ratio is 3-10 mL/g.
In some preferred embodiments, step (4) further comprises: and (2) supplementing at least one of a phosphorus source, an iron source and a lithium source into the purified liquid obtained by purifying and removing impurities to adjust the molar ratio of Fe to P to Li to be 1-1.5, adjusting the pH value to be 5-8, and directly preparing lithium iron phosphate by a hydrothermal synthesis method.
According to the technical scheme, particularly, in the step (1), the raw materials are subjected to sorting pretreatment, the sorting pretreatment can promote separation of impurities such as copper and aluminum and black powder, the battery black powder is leached by matching with the two-stage countercurrent leaching process in the step (2), and the precipitation mother liquor is circularly used in the step (6) of the two-stage leaching to obtain the lithium-rich precipitation mother liquor with the lithium concentration of more than 20g/L, so that the impurity leaching rate is effectively reduced, the higher metal recovery rate is obtained, the energy consumption is low, the economy is good, and high-value products such as battery-grade iron phosphate, battery-grade lithium carbonate, high-value copper powder, qualified cathode material precursors and the like can be recovered. The leaching rates of Fe, P and Li are favorably and remarkably improved through sorting pretreatment and two-stage countercurrent leaching (in some specific embodiments, the recovery rates of Fe, P and Li are increased by 2-5% compared with the recovery rates of Fe, P and Li in the traditional direct one-stage acid leaching process), the impurity content of the purified solution obtained through purifying and impurity removing of the obtained two-stage leaching solution is low, and therefore the subsequent preparation of a battery-grade product is favorably realized, and the prepared battery-grade iron phosphate has better electrochemical performance; the circulating leaching of the precipitation mother liquor improves the lithium concentration to a proper range, can improve the precipitation rate of lithium, improves the direct yield, avoids the use of the traditional thermal evaporation mode, reduces the energy consumption by about 50 percent, and saves the additional production cost caused by evaporation.
Due to high leaching rate and low energy consumption, the method can effectively treat the raw material with the lithium content of less than 2.3 wt%.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a process flow diagram of one embodiment of the process of the present invention.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and these ranges or values should be understood to encompass values close to these ranges or values. For numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed as specifically disclosed herein.
The invention provides a method for recovering all components of a waste lithium iron phosphate battery, which comprises the following steps:
(1) Sorting and pretreating the raw materials of the full battery to obtain battery black powder, first copper powder and a sorting solution;
(2) Mixing the battery black powder and the second-stage leaching solution for first-stage leaching, filtering to obtain a first-stage leaching solution and a first-stage leaching residue, mixing the first-stage leaching residue and an acid solution for second-stage leaching, and filtering to obtain a second-stage leaching solution and a second-stage leaching residue; wherein the second-stage leachate is replaced by an acid solution in the first extraction process;
(3) Using the two-stage leaching residue obtained in the step (2) to prepare negative graphite powder;
(4) Purifying and removing impurities from the first-stage leaching solution obtained in the step (2) to obtain second copper powder, purified slag and purified liquid;
(5) Mixing the purified liquid with a phosphorus source and/or an iron source and an optional oxidant, reacting, and filtering to obtain a precipitation mother liquid and precipitation slag;
(6) The precipitation mother liquor is circularly returned to the step (2) to carry out the secondary leaching together with the primary leaching residue, the circulating times are more than two times, and the lithium concentration in the precipitation mother liquor obtained by the circulation of the step (5) is more than 20 g/L;
(7) Washing and aging the precipitation slag obtained in the step (5), filtering to obtain ferric phosphate dihydrate, and then calcining to obtain anhydrous ferric phosphate;
(8) And (4) carrying out impurity removal and carbonation reaction on the precipitation mother liquor with the lithium concentration of more than 20g/L obtained in the step (6) in a circulating manner to prepare lithium carbonate.
In step (1), the skilled person can select the existing manner of the sorting pretreatment according to the requirements. The sorting and pretreatment modes of the invention can adopt one of any existing sorting modes, such as air separation and the like; the pretreatment method is one of shaking table and reselection, and is not described herein again.
In one embodiment, the sorting pre-treatment process comprises: dividing the raw materials into low-aluminum materials and high-aluminum materials according to different Al contents of the raw materials; then, the low-aluminum material is simply screened to remove part of plastics; the high-aluminum material is pretreated by one of methods of shaking table, gravity separation and the like, and most of copper and aluminum are separated.
In a more preferred embodiment, the sorting pre-treatment is such that: the aluminum content in the raw material is reduced to below 1wt%, and the lithium loss rate is controlled to be less than 1.5%.
In another more preferred embodiment, the sorting pre-treatment is such that: the removal rates of aluminum and copper in the raw materials are respectively more than 75wt% and more than 85wt%, and the loss rates of lithium, iron and phosphorus are respectively controlled to be 0.5-1wt%, 1-2wt% and 1-2wt%.
The first copper powder of the present invention is a high-value copper powder, preferably containing 70 to 80wt% of copper and 15 to 20wt% of aluminum.
The full battery material refers to a mixture of a positive electrode material, a negative electrode material and electrolyte of a waste lithium iron phosphate battery. In some embodiments, the whole electric core of the waste lithium iron phosphate battery can be crushed and then air-separated to obtain the raw material.
In one specific embodiment, the raw material contains 2-3wt% of lithium, 0-2wt% of aluminum and 4-15wt% of copper, wherein the battery black powder containing 0-1wt% of aluminum is treated as a low-aluminum material, and the battery black powder containing 1-2wt% of aluminum is treated as a high-aluminum material.
The step (2) of the invention adopts a countercurrent full-leaching mode of two-stage leaching, can obtain higher leaching rates of Fe, P and Li, lower leaching rates of impurities and higher acid utilization rate, and can reduce the consumption and energy consumption of subsequent impurity-removing chemicals. Compared with the prior art of only directly leaching the black powder by acid, the method adopts low-acid to leach the battery black powder with high content of components and adopts acid to leach the first-stage leaching residue with low content of components, and the two-stage countercurrent leaching mode can improve the leaching rate of Fe, P and Li, reduce the leaching rate of impurities, optimize the process and reduce the subsequent alkali addition.
The step (2) of the invention adopts two-stage countercurrent leaching, wherein the countercurrent leaching refers to the first-stage leaching of the obtained two-stage leachate and battery black powder which is used as a raw material in the step (2); compared with the one-stage leaching under the same condition, the leaching rate of the valuable elements can be obviously improved. Illustratively, in some embodiments, under the condition of the same acid amount and 20 ℃, the leaching rates of Fe, P and Li in the two-stage countercurrent leaching scheme are respectively 98.8%, 98.2% and 99% by mass; in the first stage leaching scheme, the leaching rates of Fe, P and Li are respectively 96.7%, 96.4% and 95.8%, which is lower than that of the two-stage countercurrent leaching scheme.
In some preferred embodiments, in step (2), the molar amount of the acid in the acid solution is 1.4 to 1.9 times, for example, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 times, etc., and more preferably 1.5 to 1.7 times the molar amount of the iron in the battery black powder.
In some preferred embodiments, the acid in the acid solution is selected from sulfuric acid and/or hydrochloric acid.
In some preferred embodiments, in the step (2), the conditions of the primary leaching and the secondary leaching each independently satisfy: the temperature is 20-40 ℃, for example, 20, 25, 30, 35, 40 ℃, and the like, and the liquid-solid mass ratio is 3-5:1; and/or the leaching time is 1-3h. Under the preferable scheme, the invention particularly utilizes low-temperature two-stage leaching, can further reduce the leaching rate of impurities such as aluminum and the like, simultaneously further improve the leaching rates of Fe, P and Li, promote higher acid utilization rate, and further reduce the consumption and energy consumption of subsequent impurity removal chemicals.
Compared with the scheme of high-temperature (higher than 40 ℃), the low-temperature two-stage leaching scheme of the invention has the advantages that the leaching rates of Fe, P and Li are higher, and the leaching rate of impurities is lower; the low-temperature two-stage leaching can slow down the oxidation precipitation of ferrous ions, so that the leaching rate of Fe and P can be improved, the energy consumption can be reduced, and the leaching of impurities can be obviously inhibited. In one embodiment, under the same conditions, in a low-temperature (20 ℃) two-stage leaching scheme, the leaching rates of Fe, P and Li are respectively 98.8%, 98.2% and 99% by mass, and the leaching rate of impurity Al is 36.2%; in the high-temperature (60 ℃) two-stage leaching scheme, the leaching rates of Fe, P and Li are respectively 97.3%, 96.4% and 99% by mass, and the leaching rate of impurity Al is 75.3%.
In some preferred embodiments, in the step (3), the preparing of the negative electrode graphite powder includes: and (3) curing, roasting and acid leaching the second-stage leaching residue obtained in the step (2) by sulfuric acid. The preferable scheme of the invention can prepare the precursor of the battery negative electrode material with each metal impurity less than 0.1 wt%. The precursor can be prepared into a battery cathode by the existing method, and then the battery cathode is dried and packaged by the technicians in the field.
It is understood that the sulfuric acid curing roasting process comprises: adding concentrated sulfuric acid, curing and roasting, and optionally cooling. The various stages can be performed by using the existing method, and are not described herein again.
More preferably, in step (3), the acid leaching conditions include: the liquid-solid mass ratio is 5-15, the reaction pH value is controlled to be less than 0.5, the leaching temperature is 50-100 ℃, and the leaching time is 6-8h.
The kind of acid used in the acid leaching can be selected by those skilled in the art according to requirements, for example, the acid used in the acid leaching according to the present invention can be at least one of sulfuric acid, hydrochloric acid, nitric acid, and the like. The concentration and the dosage of the acid can meet the liquid-solid mass ratio and the pH value.
Preferably, the quality parameters of the obtained battery anode material precursor satisfy the following conditions: the mass percentage of Fe is less than 0.1%, al is less than 0.05%, cu is less than 0.05%, li is less than 0.01%, P is less than 0.1%, si is less than 0.1%, and S is less than 0.2%.
Any means of decontamination known in the art may be used in the present invention by one skilled in the art, provided that the second copper powder, the decontamination slag, and the decontamination solution described above are obtained. The purification and impurity removal of the invention can adopt the existing method in the field, and are not described in detail herein.
Preferably, in step (4), the method further comprises: adding at least one of a phosphorus source, an iron source and a lithium source into the purified liquid obtained by purifying and impurity removing to adjust the molar ratio of Fe to P to Li to be 1-1.5, adjusting the pH value to be 5-8, and directly preparing the lithium iron phosphate by a hydrothermal synthesis method.
The hydrothermal synthesis method can be performed by referring to the existing method, and is not described herein again.
In some preferred embodiments, in step (5), the process of the reaction comprises: adjusting the Fe/P molar ratio to be 1-1.05, optionally slowly adding an oxidizing agent which is 1-2 times of the theoretical oxidation dosage based on the Fe molar amount, adding a pH regulator, controlling the pH to be 1.6-2.0, and controlling the reaction time to be 1-3h. It will be appreciated that the oxidant is used here to leach ferrous iron from the purge, and therefore the theoretical molar amount of oxidant required is calculated in terms of the molar amount of iron ions, and in practice the oxidant is typically in excess of this theoretical molar amount, and the oxidant amount of the present invention is set to 1-2 times the theoretical molar amount.
The oxidizing agent and the pH regulator may be added simultaneously or separately.
More preferably, the process of the reaction comprises: adjusting the molar ratio of Fe/P to 1-1.02, slowly adding an oxidant which is 1-2 times of the theoretical oxidation dosage based on the molar amount of Fe, then adding a pH regulator, controlling the pH to be 1.8-2.0, and controlling the reaction time to be 1-2h. More preferably, the temperature of the reaction is 70-90 ℃.
The Fe/P molar ratio can be adjusted by adding an iron source and/or a phosphorus source.
More preferably, the reaction is carried out in a water bath with stirring, the temperature of the water bath being 40-70 ℃. Preferably the stirring speed is 150-250rpm.
Preferably, the oxidant of the present invention may be hydrogen peroxide, SO 2 -O 2 Mixed gas or SO 2 -any of the air mixtures.
Preferably, the pH adjuster of the present invention may be at least one of ammonia water, sodium hydroxide, potassium hydroxide, and the like. More preferably, the pH adjusting agent is introduced in the form of an alkaline solution having a concentration of 2 to 5mol/L.
In step (6), it is to be understood that, when the precipitation mother liquor is recycled for leaching the primary leaching residue, the precipitation mother liquor is used as a leaching solution together with an acid for the secondary leaching, and then the precipitation mother liquor and the acid are metered as a whole leaching solution.
In some embodiments, in step (6), the number of cycles is 2 to 5, for example, 2,3,4,5, and most preferably 3. Under the preferred scheme, the method not only ensures higher metal leaching rate, but also can avoid impurity accumulation to influence the purity and recovery rate of the product.
The inventor of the invention researches and discovers that the lithium concentration in the precipitation mother liquor obtained by the circulation of the step (5) is more than 20g/L, so that the precipitation efficiency of lithium can be improved, the yield can be improved, and the recovery cost can be reduced. Furthermore, the precipitation mother liquor circulating leaching mode in the step (6) of the invention is adopted to improve the lithium concentration in the high range, the energy consumption is low, the economy is strong, and the lithium-rich liquor with the concentration meeting the requirement can be obtained under the appropriate cycle times. And the Li concentration in the lithium-rich solution (namely the precipitation mother solution) is less than 20g/L, which causes low precipitation efficiency of lithium, low yield and increased recovery cost. In the prior art, the lithium concentration is generally improved by adopting a method of directly evaporating and concentrating black powder leachate, but the method needs to consume a large amount of heat energy, and for fluorine-containing waste battery raw materials, the existence of fluorine in the solution causes serious corrosion of equipment in the evaporation process.
In some preferred embodiments, the lithium concentration in the precipitation mother liquor obtained in the recycling of step (5) is 20 to 30g/L. In other preferred embodiments, the lithium concentration in the precipitation mother liquor obtained in the recycling of step (5) is 20 to 25g/L.
The precipitation slag obtained in the step (5) is coarse phosphorus iron slag, and part of impurities are removed through washing for a plurality of times; and (3) aging for a period of time after washing to obtain white ferric phosphate dihydrate, and calcining to obtain the battery-grade anhydrous ferric phosphate. After said aging, an optional washing may also be carried out; optional drying may also be carried out prior to the calcination. In step (7) of the present invention, the calcination conditions may be performed according to the conditions existing in the art.
In step (7) of the present invention, the washing may comprise acid washing and optionally water washing.
In some preferred embodiments, in step (7), the washing process comprises: and (2) washing for several times by using washing water with the pH value of 0.5-5 in a countercurrent way under the conditions that the liquid-solid mass ratio is 20-30. The number of counter current washes can be selected by one skilled in the art as desired, preferably from 3 to 5.
The washing water can be fresh acid liquor or aged liquor obtained by filtering after aging; preferably, the filtrate obtained after the acid washing of the aging solution mainly contains lithium, phosphorus and iron, and the filtrate can be used as a pH regulator for other steps after the addition of alkali to prepare lithium phosphate and iron phosphate.
And ageing the washing slag obtained after washing to finish the conversion of chemical composition and crystal form. In some preferred embodiments, in step (7), the aging process comprises: aging in a solution with the phosphoric acid concentration of 10-35g/L at the aging temperature of 70-90 ℃ for 3-10h, wherein the liquid-solid ratio is 3-10 mL/g. The aging process also comprises filtering to obtain an aging liquid and ferric phosphate dihydrate.
A person skilled in the art can perform impurity removal and carbonation reaction on the precipitation mother liquor in step (8) according to the existing method, as long as battery-grade lithium carbonate can be obtained, and details are not described herein.
The method of the invention can effectively process the lithium in the raw material with the lithium content of less than 2.3 wt%.
In the invention, the quality parameter standards of the anhydrous battery grade iron phosphate and the battery grade lithium carbonate are shown in the following tables 1 and 2; it can be used directly in battery preparation.
TABLE 1 quality parameters of anhydrous battery grade iron phosphate products
Item Unit Standard of merit
Fe wt% 36.0-36.6
P wt% 20.5-21.1
Fe/P / 0.96-0.98
Ca wt% ≤0.005
Mg wt% ≤0.005
Na wt% ≤0.01
Ni wt% ≤0.005
Zn wt% ≤0.005
Cu wt% ≤0.002
Mn wt% ≤0.0090
Pb wt% ≤0.009
Cr wt% ≤0.009
Co wt% ≤0.005
K wt% ≤0.005
Al wt% ≤0.0060
Ti wt% ≤0.002
Mo wt% ≤0.0020
Cd wt% ≤0.0030
Magnetic foreign matter ppm ≤1000
S wt% ≤0.0400
Tap density g/cm 3 ≥0.60
Specific surface area m 2 /g 8-20
TABLE 2 quality parameters of battery grade lithium carbonate product
Figure T_220817105216746_746947002
The present invention will be described in detail with reference to specific examples. The raw materials are the mixture of the anode material, the cathode material and the electrolyte of the waste lithium iron phosphate battery, namely LFP black powder, and the main chemical components are as follows: by mass percent, 19.69 percent of Fe, 2.28 percent of Li, 5.86 percent of Cu, 1.62 percent of Al and 11.89 percent of P. The materials in the following examples are by mass unless otherwise indicated.
Example 1
A method for recycling all components of a waste lithium iron phosphate battery is shown in figure 1 and specifically comprises the following steps:
(1) The raw materials are subjected to sorting pretreatment to obtain a component 1, a component 2 and a sorting solution, wherein the component 2 contains 72.3% of copper and 18.6% of aluminum, the component 1 enters a subsequent leaching and recycling step, the removal rates of aluminum and copper are 73.26% and 84.33% in the pretreatment process, and the loss rates of lithium, iron and phosphorus are only 0.62%, 1.25% and 1.07%.
(2) The component 1 is prepared from the following components in a liquid-solid mass ratio of 3:1, the molar amount of sulfuric acid in the acid solution is 1.6 times of the molar amount of iron in the component 1, leaching is carried out at a low temperature by two stages at 20 ℃, and filtering is carried out to obtain a leaching solution and leaching residues (namely, the first-stage leaching solution and the second-stage leaching residue), wherein the leaching rates of Fe, P and Li residues are respectively 98.73%, 98.17% and 98.76%, and the leaching rate of impurity Al is 26.67%.
Wherein, the low-temperature two-stage leaching process comprises the following steps: mixing the battery black powder and the second-stage leaching solution for first-stage leaching, filtering to obtain a first-stage leaching solution and a first-stage leaching residue, mixing the first-stage leaching residue and an acid solution for second-stage leaching, and filtering to obtain a second-stage leaching solution and a second-stage leaching residue; wherein the second-stage leachate is replaced by an acid solution in the first extraction process; the first leaching time is 1h, and the second leaching time is 1h.
(3) The first-stage leachate is subjected to reduction purification and hydrolysis purification to obtain high-value copper powder (Cu 81.34%), slag and qualified purified liquid.
(4) Precipitating the purified solution under the following conditions: adjusting the molar ratio of Fe/P in the solution to 1, the temperature of the water bath to 70 ℃, the stirring speed to 200rpm, and simultaneously adding 30% H 2 O 2 And a pH adjusting agent (specifically 3mol/L sodium hydroxide solution), maintaining the pH at 2.0 2 O 2 The adding speed is 1ml/min, the reaction time is controlled to be 1h 2 O 2 Is 1.3 times the theoretical oxidation amount in the solution in terms of moles of Fe. Filtering to obtain a precipitation mother liquor 1 and a precipitation slag 1.
(5) Washing the sediment 1, wherein the washing comprises acid washing and water washing; specifically, under the condition that the total liquid-solid mass ratio is 25. The acid washing solution is from an aging solution (i.e., the aging solution in the step (6)), and the water washing solution is pure water. And (4) after the acid washing of the aging solution is finished, mainly containing lithium, phosphorus and iron, adding alkali to prepare lithium phosphate and iron phosphate, and returning to the step (3) for regulating the pH value in the purification.
(6) Wherein washing slag 1 obtained by filtering after washing is aged under the following conditions: aging in a solution with the phosphoric acid concentration of 30g/L for 8h at the aging temperature of 85 ℃ and the liquid-solid ratio of 5 mL/g. Filtering to obtain an aging solution and ferric phosphate dihydrate.
(7) The ferric phosphate dihydrate was calcined to give battery grade ferric phosphate (part of the composition of the product is shown in table 3 below).
Table 3 analysis results of battery grade iron phosphate product
Element(s) Fe P Zn Cu Pb Al Cr Ti S
Iron phosphate product/wt% 36.21 20.75 0.0016 <0.001 0.004 0.002 0.004 0.001 0.0048
(8) And (3) returning the precipitation mother liquor 1 obtained in the step (4) to the step (2) for leaching a section of leaching slag, repeating the leaching, the step (3) and the step (4), and filtering to obtain a precipitation mother liquor 2 and a precipitation slag 2, wherein the following table 4 shows analysis results of Li in the precipitation mother liquor after three times of circulation.
TABLE 4 experimental analysis results of lithium concentration after cyclic leaching
Type (B) Li/ g/L
Precipitation mother liquor 1 7.54
Mother liquor of precipitation 2 15.24
Precipitation mother liquor 3 21.69
(9) The precipitation mother liquor 3 was adjusted to pH 6.0, and after impurities were removed, reacted with a qualified saturated sodium carbonate solution to prepare battery-grade lithium carbonate, part of the composition of which is shown in table 5 below.
(10) And (3) carrying out sulfuric acid curing roasting and acid leaching on the two-stage leached residues obtained in the step (2) to obtain qualified negative electrode powder with each metal impurity less than 0.1wt%, wherein the partial composition of the qualified negative electrode powder is shown in the following table 6. Wherein, the acid leaching conditions comprise: the liquid-solid mass ratio is 10, the reaction pH value is controlled to be 0, the leaching temperature is 80 ℃, and the leaching time is 8h.
TABLE 5 analysis of impurity content of cell-grade lithium carbonate product
Figure T_220817105216888_888073005
Table 6 preparation of negative electrode powder composition analysis
Impurities in the product Fe Al Cu Li P Si S
Negative electrode slag/wt% 0.094 0.037 0.001 0.001 0.079 0.07 0.16
From the above analysis results, it can be known that both the prepared iron phosphate and lithium carbonate meet the requirements of battery grade, and the negative electrode powder also meets the requirements of impurities. The overall process recovery rates of iron, phosphorus, lithium and carbon in this example were 93.82%, 92.96%, 92.41% and 91.86%, respectively.
Example 2
The method is carried out according to the method of the example 1, except that the dosage and the temperature of the sulfuric acid in the two-stage leaching are different, specifically, in the leaching process of the step (2), the molar dosage of the sulfuric acid is 1.7 times of the molar dosage of the iron in the component 1, the leaching rates of Fe, P and Li slag are respectively 98.89%, 98.27% and 99.13% under the condition of 40 ℃, and the leaching rate of impurity Al is 43.75%; and the subsequent steps were continued as in example 1. Correspondingly, in the step (3), the Cu content in the high-value copper powder is 83.59 percent; the composition of part of the battery grade iron phosphate obtained in step (7) is shown in table 7 below; the analysis results of Li in the precipitation mother liquor after the three cycles of step (8) are shown in table 8 below; the battery grade lithium carbonate obtained in step (9), part of which is shown in table 9 below; the composition of the negative electrode powder portion obtained in step (10) is shown in table 10 below.
Table 7 analysis results of battery grade iron phosphate product
Element(s) Fe P Zn Cu Pb Al Cr Ti S
Iron phosphate product/wt% 36.46 20.87 0.0033 <0.001 0.005 0.005 0.005 0.001 0.0045
TABLE 8 experimental analysis results of lithium concentration after cyclic leaching
Type (B) Li/ g/L
Precipitation mother liquor 1 7.67
Mother liquor of precipitation 2 16.88
Precipitation mother liquor 3 23.54
TABLE 9 analysis of impurity content of cell-grade lithium carbonate product
Figure T_220817105216971_971561009
TABLE 10 preparation of negative electrode powder composition analysis
Impurities Fe Al Cu Li P Si S
Negative electrode fraction/%) 0.086 0.032 0.001 <0.001 0.087 0.054 0.15
From the analysis results, the obtained iron phosphate and lithium carbonate both meet the requirements of battery grade, and the negative electrode powder also meets the requirements of impurities. The overall process recovery rates of iron, phosphorus, lithium and carbon in this example were 94.23%, 93.67%, 93.64% and 89.44%, respectively.
Example 3
The process is carried out according to the method of example 1, except that the amount of sulfuric acid in the step (2) is different, specifically, in the leaching process of the step (2), under the condition that the molar amount of the sulfuric acid is 1.4 times of the molar amount of iron in the component 1, the leaching rates of Fe, P and Li slag are respectively 97.16%, 97.01% and 97.05%, and the leaching rate of impurity Al is 21.33%; and the subsequent steps were continued in the same manner as in example 1. Correspondingly, in the step (3), 82.61% of Cu in the high-value copper powder is contained; the partial composition of the battery grade iron phosphate obtained in step (7) is shown in table 11 below; the analysis results of Li in the precipitation mother liquor after the three cycles of the step (8) are shown in table 12 below; the composition of the battery grade lithium carbonate obtained in step (9) is shown in Table 13 below; the composition of the negative electrode powder portion obtained in step (10) is shown in table 14 below.
TABLE 11 analysis of cell grade iron phosphate products
Element(s) Fe P Zn Cu Pb Al Cr Ti S
Iron phosphate product/wt% 36.35 20.92 0.003 <0.001 0.004 0.002 0.006 0.001 0.006
TABLE 12 experimental analysis results of lithium concentration after cyclic leaching
Types of Li/ g/L
Precipitation mother liquor 1 7.30
Mother liquor of precipitation 2 16.08
Precipitation mother liquor 3 22.42
TABLE 13 analysis of impurity content of cell-grade lithium carbonate product
Figure T_220817105217112_112189013
TABLE 14 preparation of negative electrode powder composition analysis
Impurities Fe Al Cu Li P Si S
Slag/% of negative electrode 0.089 0.04 0.001 <0.001 0.091 0.058 0.12
From the analysis results, the obtained iron phosphate and lithium carbonate both meet the requirements of battery grade, and the negative electrode powder also meets the requirements of impurities. The overall process recovery rates of iron, phosphorus, lithium and carbon in this example were 92.11%, 92.85%, 91.59% and 89.51%, respectively.
Example 4
The procedure of example 1 was followed except that the precipitation mother liquor in step (8) was circulated for a different number of times, specifically, for four times in step (8), and the subsequent steps were continued in accordance with the procedure of example 1, and the results of analysis of Li in the precipitation mother liquor after the four cycles were as shown in Table 15 below. The partial compositions of the battery grade iron phosphate obtained in step (7) are shown in table 16 below; the composition of the battery grade lithium carbonate obtained in step (9) is shown in Table 17 below; the compositions of the negative electrode powders obtained in the step (10) are partially shown in the following table 18.
TABLE 15 experimental analysis results of lithium concentration after cyclic leaching
Type (B) Li/ g/L
Precipitation mother liquor 1 7.54
Precipitation mother liquor 2 15.24
Precipitation mother liquor 3 21.69
Precipitation mother liquor 4 28.35
Table 16 analysis results of battery grade iron phosphate product
Element(s) Fe P Zn Cu Pb Al Cr Ti S
Iron phosphate product/wt% 36.54 20.85 0.005 0.001 0.008 0.005 0.009 0.002 0.012
TABLE 17 analysis of impurity content of cell-grade lithium carbonate product
Figure T_220817105217161_161986017
TABLE 18 preparation of negative electrode powder composition analysis
Impurities in the product Fe Al Cu Li P Si S
Negative electrode fraction/%) 0.093 0.05 0.003 <0.001 0.098 0.08 0.29
From the above analysis results, it was found that the number of cycles increased, and the concentration of lithium in the precipitation mother liquor increased, but the amount of other impurity elements enriched was relatively increased. The iron phosphate and the lithium carbonate obtained in the embodiment both meet the requirements of battery grade, and the negative electrode powder also meets the requirements of impurities. The total process recovery rates of iron, phosphorus, lithium and carbon in this example were 90.21%, 90.68%, 90.52% and 88.67%, respectively.
Comparative example 1
The procedure is as in example 1 except that no sorting pretreatment is used, but the material is passed directly to the subsequent leach recovery step. Wherein in the step (2), the leaching rates of Fe, P and Li slag are respectively 97.52%, 97.89% and 98.58%, and the leaching rate of impurity Al is 35.41%; in the step (3), the Cu content in the high-value copper powder is 83.56 percent; the partial compositions of the battery grade iron phosphate obtained in step (7) are shown in the following table 1-1; the analysis results of Li in the precipitation mother liquor after the step (8) was circulated three times are shown in the following tables 1 to 2; the battery grade lithium carbonate obtained in the step (9) has a part of the composition shown in the following tables 1 to 3; the compositions of the negative electrode powder obtained in step (10) are shown in tables 1 to 4 below.
TABLE 1-1 analysis results of iron phosphate product
Element(s) Fe P Zn Cu Pb Al Cr Ti S
Iron phosphate product/wt% 36.16 20.79 0.01 <0.001 0.009 0.023 0.005 0.001 0.007
TABLE 1-2 experimental analysis results of lithium concentration after cycle Leaching
Types of Li/ g/L
Precipitation mother liquor 1 6.22
Mother liquor of precipitation 2 13.56
Precipitation mother liquor 3 18.33
TABLE 1-3 analysis of lithium carbonate product for impurity content
Figure T_220817105217224_224495021
Tables 1 to 4 preparation of negative electrode powder composition analysis
Impurities Fe Al Cu Li P Si S
Negative electrode fraction/%) 0.12 0.18 0.002 <0.001 0.09 0.06 0.15
The results show that some impurities in the obtained iron phosphate and lithium carbonate do not meet the requirements of battery grade, and the negative electrode powder also cannot meet the requirements of impurities. The recovery rates of iron, phosphorus, lithium and carbon in the whole process are respectively 86.24%, 83.61%, 84.71% and 93.95%. This is due to the co-hydrolysis precipitation and large entrainment loss of the elements during the impurity removal process.
Comparative example 2
The method is carried out according to the method of the embodiment 1, except that the step (2) adopts a one-stage leaching process, the leaching process conditions (liquid-solid ratio and temperature) are the same as those of the embodiment 1, and specifically, the leaching process of the step (2) is as follows: the component 1 is leached at low temperature for 2 hours under the same leaching condition as the embodiment 1, leaching liquid and leaching slag are obtained after filtration, the leaching rates of Fe, P and Li slag are respectively 96.23%, 95.17% and 95.75%, and the leaching rate of impurity Al is 25.26%;
and the subsequent steps were continued in the same manner as in example 1. Correspondingly, in the step (3), 80.05% of Cu in the high-value copper powder; the compositions of part of the battery grade iron phosphate obtained in step (7) are shown in tables 1-5 below; the analysis results of Li in the precipitation mother liquor after the step (8) is circulated three times are shown in the following tables 1 to 6; the battery grade lithium carbonate obtained in the step (9) has a part of compositions shown in the following tables 1 to 7; the compositions of the negative electrode powder obtained in step (10) are shown in tables 1 to 8 below.
Table 1-5 analysis results of battery grade iron phosphate product
Element(s) Fe P Zn Cu Pb Al Cr Ti S
Iron phosphate product/wt% 36.26 20.87 0.002 <0.001 0.005 0.002 0.004 0.001 0.005
TABLE 1-6 experimental analysis results of lithium concentration after cyclic leaching
Type (B) Li/ g/L
Precipitation mother liquor 1 7.06
Mother liquor of precipitation 2 14.52
Precipitation mother liquor 3 20.63
TABLE 1-7 analysis of impurity content of cell-grade lithium carbonate product
Figure T_220817105217271_271359025
Tables 1 to 8 analysis of the components of the negative electrode powders prepared
Impurities Fe Al Cu Li P Si S
Cathode slag/wt% 0.085 0.03 0.001 0.001 0.081 0.05 0.5
The results show that some impurities in the obtained iron phosphate and lithium carbonate basically meet the requirements of battery grade, the negative electrode powder meets the requirements of impurities, but the recovery rates of all elements are low, and the recovery rates of the iron, phosphorus, lithium and carbon in the whole process are respectively 88.02%, 87.67%, 87.88% and 90.85%.
Comparative example 3
The procedure of example 1 was followed except that the precipitation mother liquor after precipitation of iron phosphate was 7.54g/L in the precipitation mother liquor 1 without carrying out step (8), that is, without circulating the precipitation mother liquor, and then it was subjected to the subsequent steps of example 1, step (9), etc. Wherein, the corresponding partial compositions of the battery grade iron phosphate obtained in step (7) are shown in tables 1 to 9 below; the battery grade lithium carbonate obtained in the step (9) has a part of compositions shown in the following tables 1 to 10; the compositions of the negative electrode powder portions obtained in step (10) are shown in tables 1 to 11 below.
Table 1-9 analysis results of battery grade iron phosphate product
Element(s) Fe P Zn Cu Pb Al Cr Ti S
Iron phosphate product/wt% 36.37 20.66 0.0014 <0.001 0.004 0.001 0.003 0.001 0.005
TABLE 1-10 analysis of impurity content of cell grade lithium carbonate product
Figure T_220817105217318_318238028
Tables 1 to 11 preparation of negative electrode powder composition analysis
Impurities in the product Fe Al Cu Li P Si S
Slag/% of negative electrode 0.092 0.045 0.001 <0.001 0.075 0.08 0.16
The analysis result shows that the recycling of the precipitation mother liquor can greatly reduce the recovery rate of lithium, the negative electrode powder meets the requirement of impurities, and the full-process recovery rates of iron, phosphorus, lithium and carbon are 93.46%, 92.55%, 81.23% and 91.59% respectively.
As can be seen from the examples 1-2 and the comparative examples 1-3, the scheme of the invention can obtain higher comprehensive metal recovery rate, can prepare battery-grade iron phosphate, lithium carbonate and battery negative electrode material precursor, and has the advantages of less acid consumption and low energy consumption; in the comparative example, the effect of the invention cannot be achieved by the scheme of not carrying out sorting pretreatment, or only carrying out low-temperature one-stage leaching, or not carrying out circulating precipitation of mother liquor.
Further, it can be seen from examples 1 and 3 that the leaching rates and recovery rates of Fe, li and P are higher when the amount of sulfuric acid is in the preferred range. It can be seen from examples 1 and 4 that the recovery rate is higher when the number of cycles of the precipitation mother liquor is in the preferred range.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including various technical features being combined in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims (8)

1. A method for recovering all components of a waste lithium iron phosphate battery is characterized by comprising the following steps:
(1) Sorting and pretreating the raw materials of the full battery material to obtain battery black powder, first copper powder and a sorting solution;
(2) Mixing battery black powder and the second-stage leaching solution for first-stage leaching, filtering to obtain a first-stage leaching solution and first-stage leaching residues, mixing the first-stage leaching residues and an acid solution for second-stage leaching, and filtering to obtain a second-stage leaching solution and second-stage leaching residues; wherein the second-stage leachate is replaced by an acid solution in the first extraction process; the molar amount of acid in the acid solution is 1.4-1.9 times of the molar amount of iron in the battery black powder, and the conditions of the first-stage leaching and the second-stage leaching are respectively and independently satisfied: the temperature is 20-40 ℃, and the liquid-solid mass ratio is 3-5; and/or the leaching time is 1-3h;
(3) Using the two-stage leaching residue obtained in the step (2) to prepare negative graphite powder;
(4) Purifying and removing impurities from the first-stage leaching solution obtained in the step (2) to obtain second copper powder, purified slag and purified liquid;
(5) Mixing the purified liquid with a phosphorus source and/or an iron source and an oxidant, reacting, and filtering to obtain a precipitation mother liquid and precipitation slag;
(6) The precipitation mother liquor is circularly returned to the step (2), and the two-stage leaching is carried out together with the first-stage leaching residue, wherein the circulating times are more than two times until the concentration of lithium in the precipitation mother liquor obtained in the step (5) in a circulating manner is more than 20 g/L;
(7) Washing and aging the precipitation slag obtained in the step (5), filtering to obtain ferric phosphate dihydrate, and then calcining to obtain anhydrous ferric phosphate;
(8) And (4) carrying out impurity removal and carbonation reaction on the precipitation mother liquor with the lithium concentration of more than 20g/L obtained in the step (6) in a circulating manner to prepare lithium carbonate.
2. The recycling method according to claim 1, wherein in the step (2), the acid in the acid solution is selected from sulfuric acid and/or hydrochloric acid.
3. The recycling method according to claim 1, wherein in the step (3), the process of preparing the negative electrode graphite powder comprises: and (3) curing, roasting and acid leaching the second-stage leached residues in the step (2) by sulfuric acid.
4. The recovery process according to claim 3, characterized in that the acid leaching conditions comprise: the liquid-solid mass ratio is 5-15, the reaction pH value is controlled to be less than 0.5, the leaching temperature is 50-100 ℃, and the leaching time is 6-8h.
5. The recovery method according to claim 1, wherein in the step (5), the reaction process comprises: adjusting the molar ratio of Fe/P to be 1-1.05, adding an oxidant which is 1-2 times of the theoretical oxidation dosage in terms of Fe molar amount, adding a pH regulator, controlling the pH to be 1.6-2.0, and controlling the reaction time to be 1-3h;
and/or, the reaction is carried out in a water bath with stirring, and the temperature of the water bath is 40-70 ℃.
6. The recovery method according to claim 1, wherein the number of the circulation in the step (6) is 2 to 4, and/or the concentration of lithium in the precipitation mother liquor obtained by the circulation in the step (5) is 20 to 30g/L.
7. A recycling method according to claim 1, characterized in that, in the step (7),
the washing process comprises the following steps: washing with washing water with pH value of 0.5-5 in countercurrent for several times under the condition that the mass ratio of liquid to solid is 20-30;
and/or, the aging process comprises: aging in a solution with the concentration of phosphoric acid of 10-35g/L at the temperature of 70-90 ℃ for 3-10h, wherein the liquid-solid ratio is 3-10 mL/g.
8. The recycling method according to claim 1, wherein the step (4) further comprises: and (2) supplementing at least one of a phosphorus source, an iron source and a lithium source into the purified liquid obtained by purifying and removing impurities to adjust the molar ratio of Fe to P to Li to be 1-1.5, adjusting the pH value to be 5-8, and directly preparing lithium iron phosphate by a hydrothermal synthesis method.
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