CN114506834A - Treatment method of waste lithium iron phosphate powder and carbon-coated lithium iron phosphate - Google Patents

Treatment method of waste lithium iron phosphate powder and carbon-coated lithium iron phosphate Download PDF

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CN114506834A
CN114506834A CN202210125820.8A CN202210125820A CN114506834A CN 114506834 A CN114506834 A CN 114506834A CN 202210125820 A CN202210125820 A CN 202210125820A CN 114506834 A CN114506834 A CN 114506834A
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lithium iron
iron phosphate
powder
lithium
leaching solution
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陈迎迎
肖益帆
胡加文
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Hubei Jinhui Lithium Material Technology Co ltd
Hubei Yunxiang Juneng New Energy Technology Co ltd
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Hubei Jinhui Lithium Material Technology Co ltd
Hubei Yunxiang Juneng New Energy Technology Co ltd
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    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00Phosphorus; Compounds thereof
    • C01B25/16Oxyacids of phosphorus; Salts thereof
    • C01B25/26Phosphates
    • C01B25/45Phosphates containing plural metal, or metal and ammonium
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
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    • C01P2006/80Compositional purity
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    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02WCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
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Abstract

The invention provides a treatment method of waste lithium iron phosphate powder and lithium iron phosphate, comprising the following steps of: soaking waste lithium iron phosphate powder in alkali liquor, filtering to obtain alkali-soaked black powder, then adding acid for soaking, adjusting the pH value of the leachate to 1.5-3.5, adding iron powder for reaction, performing solid-liquid separation to obtain sponge copper and leachate, continuously removing heavy metals and aluminum, adding a phosphorus source, an iron source and a lithium source in a specific ratio for reaction to obtain slurry, drying to obtain lithium iron phosphate precursor powder, adding a carbon source, and sintering in a high-temperature inert atmosphere to obtain a lithium iron phosphate product. The treatment process can simultaneously recover lithium iron phosphorus in the waste lithium iron phosphate powder, and directly prepare the high-added-value lithium iron phosphate product.

Description

Treatment method of waste lithium iron phosphate powder and carbon-coated lithium iron phosphate
Technical Field
The invention relates to the technical field of lithium battery material recovery, in particular to a treatment method of waste lithium iron phosphate powder and carbon-coated lithium iron phosphate.
Background
The traditional recovery process of waste lithium iron phosphate powder mainly comprises two steps: (1) only recovering lithium to prepare lithium carbonate, and stacking the ferrophosphorus slag as tailings; (2) and meanwhile, lithium iron phosphorus elements are recovered, and the lithium carbonate and the crude iron phosphate are prepared, so that the impurity content is high. For example, patent document CN112441571A discloses a method for recovering high-aluminum lithium iron phosphate waste to prepare a lithium carbonate product; patent document CN113880064A discloses a method for treating high-impurity lithium iron phosphate waste powder with low consumption of phosphoric acid, which can prepare high-purity iron phosphate; patent document CN112410556A discloses a method for recovering lithium iron phosphate waste powder, which can prepare lithium carbonate and iron phosphate powder; patent document CN113443640A discloses a method for preparing battery-grade lithium carbonate and battery-grade iron phosphate from waste positive and negative electrode powders of lithium iron phosphate batteries, which can prepare a battery-grade lithium carbonate product and a battery-grade iron phosphate product; patent document CN112794300A discloses a method for separating, recovering and regenerating a positive plate of a waste lithium iron phosphate battery, which comprises the steps of calcining, screening, treating with alkali liquor, adding an iron source/lithium source/phosphorus source compound, and performing secondary calcination to obtain a new lithium iron phosphate material; patent document CN109095481B discloses a comprehensive recovery method of waste lithium iron phosphate powder, which comprises the process steps of oxidizing roasting, acid-reverse leaching, purifying to remove phosphate radicals, removing calcium and magnesium, synthesizing and the like; patent document CN109256595B discloses a method for preparing battery-grade lithium iron phosphate by directly repairing waste lithium iron phosphate powder by a pyrogenic process, wherein a battery-grade lithium iron phosphate product is obtained by oxidizing roasting, blending, ball milling, drying, sintering, screening and deironing.
However, although the above patent technology discloses a method for treating waste lithium iron phosphate powder, which can treat waste lithium iron phosphate powder, it cannot solve the problem that impurity elements such as copper, aluminum, and heavy metals exceed standards, and thus has specific requirements for waste lithium iron powder. The waste lithium iron powder on the market is mainly obtained by crushing and grading waste lithium iron phosphate electric cores, generally contains more impurity elements such as copper, aluminum, heavy metals and the like, and qualified lithium iron phosphate products cannot be obtained by the treatment method. In addition, the disclosed method for treating waste lithium iron phosphate powder generally adopts a step-by-step extraction process, namely, lithium salt and iron phosphate are respectively extracted, and then the lithium salt and the iron phosphate are used for synthesizing the lithium iron phosphate; therefore, the whole process is long, the preparation cost of the lithium iron phosphate is high, and the industrial application is not facilitated.
Disclosure of Invention
Based on the above, the invention provides a treatment method of waste lithium iron phosphate powder and a carbon-coated lithium iron phosphate finished product, and solves the problem of overproof impurity elements through alkaline leaching, acid dissolution, copper removal, heavy metal removal and aluminum removal; meanwhile, the hydrothermal method is adopted to directly synthesize the lithium iron phosphate, so that the processes of extracting lithium and iron and phosphorus are omitted, and the preparation cost of the lithium iron phosphate is reduced.
The invention adopts the following technical scheme:
the invention provides a treatment method of waste lithium iron phosphate powder, which comprises the following steps: by using OH-Soaking lithium iron phosphate waste powder in an aqueous alkali with the concentration of 1-5 mol/L, wherein the mass ratio of the lithium iron phosphate waste powder to the aqueous alkali is 1: (2-5) filtering after no bubbles are generated in the solution to obtain alkaline leaching black powder; then use H+Acid leaching alkali leaching black powder with the concentration of 3-10 mol/L; solid-liquid separation and deslagging (mainly comprising carbon powder, graphite powder, copper scraps and the like) to obtain a first leaching solution containing lithium, iron and phosphorus; adjusting the pH value of the first leaching solution to 1.5-3.5 to obtain a second leaching solution; adding iron powder into the second leaching solution, performing displacement reaction with copper ions, and performing solid-liquid separation to obtain sponge copper and a third leaching solution; adding a heavy metal capture agent into the third leaching solution, stirring for reaction, and carrying out solid-liquid separation and slag removal to obtain a fourth leaching solution; adding fluoride salt into the fourth leaching solution, stirring for reaction, and carrying out solid-liquid separation and slag removal to obtain a fifth leaching solution; adding a phosphorus source, an iron source and a lithium source into the fifth leaching solution, and adjusting the quantity ratio of P, Fe and Li substances in the solution to be (1-1.05): 1 (1.5-3) to obtain a lithium iron synthesis precursor solution; adjusting the pH value of the lithium iron synthesis precursor solution to 7-9, heating to 120-180 ℃, pressurizing to 0.3-0.8 Mpa, and carrying out heat preservation and pressure maintaining reaction for 4-7 hours to obtain lithium iron phosphate precursor slurry; performing solid-liquid separation on the lithium iron phosphate precursor slurry by using a filter press to obtain a lithium iron phosphate filter cake, washing the lithium iron phosphate filter cake by using pure water until the conductivity of rinsing water is less than or equal to 200us/cm, and then drying by using vacuum drying until the moisture is less than or equal to 1% to obtain lithium iron phosphate precursor powder; and adding a carbon source into the lithium iron phosphate precursor powder, uniformly dispersing, and sintering at a high temperature in an inert atmosphere to prepare the carbon-coated lithium iron phosphate product.
In some of these embodiments, H+The acid with the concentration of 3-10 mol/L isHydrochloric acid or sulfuric acid. Preferably H+Hydrochloric acid or sulfuric acid with the concentration of 5-8 mol/L.
In some embodiments, the liquid-solid ratio of the acid to the waste lithium iron phosphate powder is (2-5): 1, the leaching temperature is 20-60 ℃, and the leaching time is 2-6 h.
In some of these embodiments, the employing H+The process of acid soaking the waste lithium iron phosphate powder with the concentration of 3-10 mol/L further comprises the step of adopting inert gas protection to prevent ferrous oxidation.
In some embodiments, the lithium iron synthesis precursor solution further contains glucose or ascorbic acid to prevent oxidation of ferrous ions.
In some embodiments, the pH adjusting agent used for preparing the second leaching solution is at least one selected from iron powder, sodium (hydrogen) carbonate, ammonium (hydrogen) carbonate and liquid alkali.
In some embodiments, the molar amount of the iron powder is more than 10-15% of the stoichiometric ratio of the reaction with the copper ions in the second leaching solution.
In some of these embodiments, the heavy metal scavenger is selected from at least one of sodium sulfide, potassium sulfide, ammonium sulfide. The addition amount is calculated according to the content of the heavy metal catching agent in the leaching solution of 0.2-0.6 g/L.
In some embodiments, the fluoride salt is added in a molar amount of 300-350% of the aluminum ion content in the fourth leachate.
In some of these embodiments, the source of phosphorus is selected from at least one of phosphoric acid, monoammonium phosphate, diammonium phosphate, and sodium phosphate.
In some of these embodiments, the iron source is selected from at least one of ferrous sulfate, ferrous chloride.
In some of these embodiments, the lithium source is selected from at least one of lithium sulfate, lithium chloride, lithium carbonate, lithium phosphate.
In some of these embodiments, the carbon source is selected from glucose or sucrose.
In some embodiments, the adding amount of the carbon source is 1.4-1.8 wt% of the carbon content in the lithium iron product, the sintering heat preservation temperature is 700-750 ℃, and the heat preservation time is 3-6 hours.
The invention also provides a lithium iron phosphate finished product prepared by the treatment method of the lithium iron phosphate waste powder, wherein the carbon content is 1.4-1.8%, and the tap density is 0.8-1.2 g/cm3Specific surface area of 15. + -.2 m2The specific discharge capacity is more than or equal to 155 mAh/g.
The invention has the beneficial effects that:
compared with the prior art, the treatment method of the lithium iron phosphate waste powder comprises the steps of soaking the lithium iron phosphate waste powder in alkali liquor to leach Al in the lithium iron phosphate waste powder, filtering to obtain alkali-leached black powder, leaching the lithium iron phosphate by acid leaching, filtering to remove carbon powder, graphite powder and copper scraps, and removing a small amount of residual Cu in filtrate2+Heavy metal ion and Al3+Then, iron powder, a heavy metal catching agent and fluoride salt are added to remove the iron powder, the heavy metal catching agent and the fluoride salt, so that lithium iron phosphate leachate with extremely low impurity content is obtained; and then adjusting the proportion of iron, phosphorus and lithium in the leachate, directly synthesizing a lithium iron phosphate precursor by a hydrothermal process, and then preparing a carbon-coated lithium iron phosphate finished product by carbon coating and sintering, so that the processes of extracting lithium and iron and phosphorus are omitted, and the carbon-coated lithium iron phosphate product with high added value is directly prepared.
Drawings
Fig. 1 is an SEM photograph of a finished carbon-coated lithium iron phosphate product prepared in example 1.
Fig. 2 is an XRD pattern of the carbon-coated lithium iron phosphate finished product prepared in example 1.
Detailed Description
The present invention is further described in detail below with reference to specific examples so that those skilled in the art can more clearly understand the present invention.
The following examples are provided only for illustrating the present invention and are not intended to limit the scope of the present invention. All other embodiments obtained by a person skilled in the art based on the specific embodiments of the present invention without any inventive step are within the scope of the present invention.
In the examples of the present invention, all the raw material components are commercially available products well known to those skilled in the art, unless otherwise specified; in the examples of the present invention, unless otherwise specified, all technical means used are conventional means well known to those skilled in the art.
Lithium iron phosphate waste powder: and crushing and grading the purchased waste lithium iron battery cell.
Description of component detection: 24.1 percent of iron, 13.4 percent of phosphorus, 3.0 percent of lithium, 32.3 percent of carbon, 1.1 percent of aluminum and 0.7 percent of copper.
Example 1
The embodiment provides a method for treating waste lithium iron phosphate powder, which comprises the following steps:
s1, weighing 500g of waste lithium iron phosphate powder, adding 1500g of 3mol/L NaOH solution, stirring, filtering after no bubbles are generated in the solution, obtaining alkali leaching black powder, adding 1500g of sulfuric acid solution for leaching, wherein the hydrogen ion concentration of the sulfuric acid solution is 5mol/L, stirring and leaching for 3 hours at the temperature of 30 ℃, filtering to obtain filter residues mainly containing carbon powder, graphite powder, copper scraps and the like and a first leaching solution containing lithium, iron and phosphorus, and the leaching rate of lithium is measured to be 91.24%. The leaching process adopts high-purity nitrogen protection, so that the environment is in a micro-positive pressure state, the ferrous oxidation in the leaching process is reduced, the generation of ferric phosphate is reduced, and the iron loss is reduced.
S2, adding sodium carbonate into the first leaching solution containing lithium, iron and phosphorus obtained in the step S1, and adjusting the pH of the solution to 2.0 to obtain a second leaching solution. And then detecting the content of copper ions in the solution, adding iron powder according to the reaction stoichiometric ratio of the copper ions and the iron powder, reducing the copper ions into sponge copper, and filtering to obtain a copper-removing leaching solution, which is marked as a third leaching solution.
And S3, adding sodium sulfide into the copper removal leaching solution (the third leaching solution), wherein the adding amount is calculated according to the concentration of the sodium sulfide in the leaching solution of 0.3g/L, and filtering to obtain a heavy metal removal leaching solution which is recorded as a fourth leaching solution.
S4, sampling the fourth leaching solution, detecting the aluminum content in the fourth leaching solution, adding sodium fluoride, stirring and reacting for 30min, and filtering to obtain an aluminum-removed leaching solution, which is marked as a fifth leaching solution.
And S5, sampling the fifth leaching solution, detecting the content of lithium, iron and phosphorus in the solution, and adjusting n (P/Fe/Li) in the solution to be 1.03:1:2 by respectively using lithium sulfate as a lithium source, ferrous sulfate as an iron source and phosphoric acid as a phosphorus source to obtain a lithium iron synthesis precursor solution. In addition, the lithium iron synthesis solution also contains a certain amount of glucose to prevent the oxidation of ferrous ions.
S6, adding liquid alkali into the pre-synthesis solution obtained in the step S5, adjusting the pH of the solution to 8, heating to 130 ℃, pressurizing to 0.4Mpa, and carrying out heat preservation and pressure maintaining reaction for 5 hours to obtain the lithium iron phosphate precursor slurry. And performing solid-liquid separation to obtain a lithium iron phosphate precursor filter cake, washing with pure water until the conductance is less than or equal to 200us/cm, and drying by vacuum drying until the moisture is less than or equal to 1% to obtain lithium iron phosphate precursor powder.
S7, adding glucose (the carbon content of the finished product is 1.5 wt%) into the lithium iron phosphate precursor powder, fully mixing uniformly, keeping the temperature for 4 hours at 720 ℃ in a nitrogen atmosphere, and sintering to obtain the carbon-coated lithium iron phosphate product.
Example 2
The present embodiment provides a method for processing waste lithium iron phosphate powder, which has substantially the same process steps as those in embodiment 1, and the difference is that: the acid added in step S1 is hydrochloric acid, and the leaching rate of lithium is 99.37% by stirring and leaching at 30 ℃ for 3 hours.
Example 3
The present embodiment provides a method for processing waste lithium iron phosphate powder, which has substantially the same process steps as those in embodiment 1, and the difference is that: in step S2, iron powder is added in a 15% excess over the stoichiometric ratio for the copper ions to react with the iron powder. In the step S3, the heavy metal catching agent is ammonium sulfide, and the adding amount is calculated according to the concentration of the ammonium sulfide in the leaching solution of 0.5 g/L.
Example 4
The present embodiment provides a method for processing waste lithium iron phosphate powder, which has substantially the same process steps as those in embodiment 1, and the difference is that: and (5) adding ammonia water into the synthesis precursor solution obtained in the step S5, adjusting the pH value of the solution to 8, heating to 170 ℃, pressurizing to 0.6Mpa, and carrying out heat preservation and pressure maintaining reaction for 5 hours to obtain the lithium iron phosphate precursor slurry.
Comparative example 1
The comparative example provides a treatment method of waste lithium iron phosphate powder, which is basically the same as the process steps of example 1, and is different from the following steps: the lithium iron phosphate waste powder is extracted by using a sodium hydroxide solution, and the leaching rate of lithium is 3.48 percent.
Comparative example 2
The comparative example provides a treatment method of waste lithium iron phosphate powder, which is basically the same as the process steps of example 1, and is different from the following steps: the copper removal process of step S2 is omitted.
Comparative example 3
The comparative example provides a treatment method of waste lithium iron phosphate powder, which is basically the same as the process steps of example 1, and is different from the following steps: the heavy metal removal process of step S3 is omitted.
Comparative example 4
The comparative example provides a treatment method of waste lithium iron phosphate powder, which is basically the same as the process steps of example 1, and is different from the following steps: the aluminum removal process of step S4 is omitted.
Comparative example 5
The comparative example provides a treatment method of waste lithium iron phosphate powder, which is basically the same as the process steps of example 1, and is different from the following steps: the sintering heat preservation temperature is 600 ℃, and the heat preservation time is 2 hours.
The material performance and the electrical performance of the lithium iron phosphate prepared in examples 1 to 4 and comparative examples 1 to 5 were respectively tested, and the test results are shown in table 1 below:
TABLE 1 statistical table of test performance
Figure BDA0003500457880000071
As shown in Table 1, the lithium iron phosphate prepared in examples 1 to 4 had a carbon content of 1.5 to 1.7% and a tap density of 0.9 to 1.1g/cm3The specific surface area is 14-16 m2The specific discharge capacity is more than 155mAh/g, and the first efficiency is more than 97%.
In the comparative example 1, the battery powder is leached by using the sodium hydroxide solution, and the leaching rate of lithium is extremely low, so that the follow-up verification cannot be carried out. Comparative example 2 copper ions in the leachate can be removed only in the removal of heavy metals because copper is not removed, but the content of copper ions is too high because the concentration of copper ions in the leachate is too high and the addition amount of sodium sulfide is insufficient; meanwhile, a large amount of sodium sulfide is consumed by copper ions, so that heavy metal ions Ni and Zn cannot be completely removed. Comparative example 3 has no heavy metal removal process, so that heavy metal ions Ni and Zn cannot be removed, and the contents of Ni and Zn are too high; however, copper ions could not be further removed after the copper removal process, resulting in a higher copper ion content than in example 1. The high impurity content of heavy metals such as Cu, Ni, Zn, etc. can result in high self-discharge of the battery, increased polarization, and poor consistency and safety, so that the gram-discharge capacity of comparative examples 2 and 3 is low. Comparative example 4 has no aluminum removal process, so that the aluminum content of the product seriously exceeds the standard and cannot meet the requirements of customers. When the lithium iron phosphate is prepared according to the comparative example 5, the sintering temperature is too low, the heat preservation time is too short, so that the carbon source cannot be fully sintered, the graphitization degree of the coated carbon is low, the carbon content and the specific surface area are high, the tap density is low, and the electrical property is poor.
In addition, it is worth stating that the team of the inventors found through a great deal of research:
(1) by means of H+Acid leaching alkali leaching black powder with the concentration of 3-10 mol/L can obtain synchronous carbon powder, graphite powder, copper scraps and the like; when H is present+The concentration is lower than 3mol/L, which causes the leaching speed of the battery powder to be too slow, the leaching time to be too long, and the leaching rate of lithium in the same time to be low; when H is present+The concentration higher than 10mol/L may result in too large amount of acid, too low pH value of the first leaching solution, consumption of a large amount of pH regulator when adjusting pH in step S2, and high production cost.
(2) The pH value of the second leaching solution is preferably 1.5-3.5, so that the effect of the replacement reaction between the iron powder and the copper ions is better. If the pH is less than 1.5, the iron powder will react with H+The reaction not only generates hydrogen gas but also increases the amount of iron powder consumed. If the pH is higher than 3.5, precipitation of ferrous phosphate is likely to occur, resulting in a large loss of iron and phosphorus, which affects the recovery rate.
(3) The molar weight of the iron powder added during copper removal is preferably more than 10-15% of the reaction stoichiometric ratio of the iron powder and the copper ions in the second leaching solution. If the adding amount of the iron powder is less than 10% of the reaction metering ratio, the copper ions are not completely reacted, and the copper ions cannot be completely removed; if the adding amount of the iron powder is more than 15% of the reaction metering ratio, the iron powder is too much, and the residual iron powder is too much after the reaction is finished, so that the iron powder is wasted.
(4) The addition amount of the heavy metal catching agent is calculated according to the content of the heavy metal catching agent in the leaching solution of 0.2-0.6 g/L. If the content of the heavy metal capture agent in the leachate is lower than 0.2g/L, the heavy metal ions in the leachate cannot be completely removed; if the content of the heavy metal scavenger in the leachate is higher than 0.6g/L, the heavy metal scavenger is too much, so that the heavy metal scavenger is wasted.
(5) The adding molar weight of the fluoride salt is 300-350% of the aluminum ion content in the fourth leaching solution. If the adding molar weight of the fluoride salt is less than 300% of the content of the aluminum ions in the fourth leaching solution, the aluminum ions in the fourth leaching solution cannot be completely removed; if the adding molar amount of the fluoride salt is more than 350% of the aluminum ion content in the fourth leaching solution, the adding amount of the fluoride salt is too much, and the fluoride salt is wasted.
Compared with the existing process for extracting the iron phosphate and the lithium carbonate, the method has better compatibility with the waste battery powder, can treat the waste battery powder with high aluminum, high copper and high heavy metal impurities, directly recycles the waste lithium iron phosphate battery powder to prepare the qualified lithium iron phosphate material by using a hydrothermal process, simplifies and shortens recycling procedures, and is favorable for reducing recycling cost and industrial application.
It should be noted that the above examples are only for further illustration and description of the technical solution of the present invention, and are not intended to further limit the technical solution of the present invention, and the method of the present invention is only a preferred embodiment, and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A treatment method of waste lithium iron phosphate powder comprises the following steps:
by using OH-The concentration of the organic solvent is 1-5 moSoaking the waste lithium iron phosphate powder in an L/L aqueous alkali, wherein the mass ratio of the waste lithium iron phosphate powder to the aqueous alkali is 1: (2-5) filtering after no bubble is generated in the solution to obtain alkali leaching black powder;
then use H+Soaking the alkali-leached black powder in acid with the concentration of 3-10 mol/L, and performing solid-liquid separation and slag removal to obtain a first leaching solution;
adjusting the pH value of the first leaching solution to 1.5-3.5 to obtain a second leaching solution; adding iron powder into the second leaching solution, performing displacement reaction with copper ions, and performing solid-liquid separation to obtain sponge copper and a third leaching solution;
adding a heavy metal capture agent into the third leaching solution, stirring for reaction, and carrying out solid-liquid separation and slag removal to obtain a fourth leaching solution;
adding fluoride salt into the fourth leaching solution, stirring for reaction, and carrying out solid-liquid separation and slag removal to obtain a fifth leaching solution;
adding a phosphorus source, an iron source and a lithium source into the fifth leaching solution, and adjusting the quantity ratio of P, Fe and Li substances in the solution to be (1-1.05): 1 (1.5-3) to obtain a lithium iron synthesis precursor solution;
adjusting the pH value of the lithium iron synthesis precursor solution to 7-9, heating to 120-180 ℃, pressurizing to 0.3-0.8 Mpa, and carrying out heat preservation and pressure maintaining reaction for 4-7 hours to obtain lithium iron phosphate precursor slurry;
performing solid-liquid separation on the lithium iron phosphate precursor slurry by using a filter press to obtain a lithium iron phosphate filter cake, washing the lithium iron phosphate filter cake by using pure water until the conductivity of rinsing water is less than or equal to 200us/cm, and then drying by using vacuum drying until the moisture is less than or equal to 1% to obtain lithium iron phosphate precursor powder;
and adding a carbon source into the lithium iron phosphate precursor powder, uniformly dispersing, and sintering in a high-temperature inert atmosphere to prepare the lithium iron phosphate product.
2. The method for treating waste lithium iron phosphate powder according to claim 1, wherein H is H+The acid with the concentration of 3-10 mol/L is hydrochloric acid or sulfuric acid.
3. The method for treating waste lithium iron phosphate powder according to claim 2, wherein the method is characterized in thatIs characterized in that H+The liquid-solid ratio of acid with the concentration of 3-10 mol/L to the waste lithium iron phosphate powder is (2-5): 1, leaching at the temperature of 20-60 ℃ for 2-6 h;
said adopt H+The process of acid soaking the waste lithium iron phosphate powder with the concentration of 3-10 mol/L further comprises the step of adopting inert gas protection to prevent ferrous oxidation.
4. The method for treating the waste lithium iron phosphate powder according to claim 1, wherein the molar amount of the iron powder is more than 10-15% of the stoichiometric ratio of the molar amount of the iron powder to the molar amount of the copper ions in the second leaching solution.
5. The method for treating waste lithium iron phosphate powder according to claim 1, wherein the heavy metal scavenger is at least one selected from the group consisting of sodium sulfide, potassium sulfide and ammonium sulfide.
6. The method for treating the waste lithium iron phosphate powder according to claim 1, wherein the molar amount of the fluoride salt added is 300-350% of the aluminum ion content in the fourth leachate.
7. The method for treating waste lithium iron phosphate powder according to claim 1, wherein the phosphorus source is at least one selected from phosphoric acid, monoammonium phosphate, diammonium phosphate and sodium phosphate;
the iron source is at least one of ferrous sulfate and ferrous chloride;
the lithium source is at least one selected from lithium sulfate, lithium chloride, lithium carbonate and lithium phosphate.
8. The method for treating waste lithium iron phosphate powder according to claim 1, wherein the carbon source is selected from glucose or sucrose.
9. The method for treating the waste lithium iron phosphate powder according to claim 1, wherein the carbon source is added in an amount of 1.4-1.8 wt% based on the carbon content in the lithium iron product, the sintering temperature is 700-750 ℃, and the sintering time is 3-6 h.
10. The finished product of carbon-coated lithium iron phosphate prepared by the method for treating waste lithium iron phosphate powder of any one of claims 1 to 9.
CN202210125820.8A 2022-02-10 2022-02-10 Treatment method of waste lithium iron phosphate powder and carbon-coated lithium iron phosphate Pending CN114506834A (en)

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