CN116190843A - Recycling method of waste lithium iron phosphate battery anode powder - Google Patents
Recycling method of waste lithium iron phosphate battery anode powder Download PDFInfo
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- 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
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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
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- 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
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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
Abstract
The invention discloses a recycling method of waste lithium iron phosphate battery anode powder, which mainly comprises the following steps: acid-dissolving waste lithium iron phosphate anode powder by adopting nitric acid and sodium hypochlorite to obtain acid-leaching liquid; heating the pickle liquor to remove acid, adjusting the pH value to 1.5-2.0, and carrying out suction filtration to obtain lithium-containing liquor and ferric phosphate filter residues; removing impurities from the lithium-containing liquid, precipitating lithium, and performing carbonization pyrolysis to obtain battery-grade lithium carbonate; and (3) carrying out solid-phase electrolysis and chemical precipitation on the iron phosphate filter residues, and then carrying out recycling electrolysis to obtain the battery grade iron phosphate. The method realizes the full recovery and high conversion rate of lithium, phosphorus and iron elements in the waste lithium iron phosphate positive electrode powder, and the prepared lithium carbonate and ferric phosphate reach the battery level standard, thereby having great application prospect.
Description
Technical Field
The invention belongs to the technical field of waste lithium ion battery recovery, and particularly relates to a method for recycling positive electrode powder of a waste lithium iron phosphate battery.
Background
Lithium iron phosphate batteries are widely used as one of the types of lithium ion batteries because of the advantages of good high-temperature performance, no pollution to the environment and the like, but along with the retirement of large-scale lithium ion batteries, the recovery of the lithium ion batteries becomes a difficult problem to be solved in the current society. The lithium ion battery consists of an anode, a cathode, electrolyte, a diaphragm and a shell, wherein each component has recycling value, and if the lithium ion battery is directly scrapped, the resource waste can be caused. In view of the extremely large market demand of the current lithium carbonate and ferric phosphate, the waste lithium iron phosphate anode material is recycled and changed into lithium carbonate and ferric phosphate, so that the waste is truly changed into valuable.
At present, a plurality of waste lithium iron phosphate anode materials are processed by acid leaching with sulfuric acid, hydrochloric acid or nitric acid to obtain lithium-containing liquid, and removing impurities, concentrating and precipitating lithium to obtain lithium carbonate. For example, the Chinese patent application with publication number CN109554545A is prepared by adding water into lithium iron phosphate waste to prepare slurry, adding acid into the slurry, heating the slurry to 40-100 ℃, regulating the pH value of the system to 2-4, maintaining the temperature and the pH value range, reacting for 1-10 hours, filtering and separating the reacted slurry to obtain lithium solution, and preparing lithium carbonate; according to the scheme, lithium is extracted by an acid leaching method, but iron and phosphorus are not recovered, so that resource waste is easily caused.
In another chinese patent application, CN107352524a, a decomposition accelerator is added to a lithium iron phosphate raw material, after sulfating roasting, water leaching, and pH adjustment with alkaline solution, ferric phosphate is precipitated, and then a battery grade ferric phosphate product is obtained by refining, and a filtrate is precipitated with sodium carbonate to obtain a lithium carbonate product; although the scheme realizes the preparation of lithium carbonate and ferric phosphate, the preparation method needs to be roasted when the pretreatment of the lithium iron phosphate is performed, has higher energy consumption and cannot be popularized in actual production.
In addition, in the chinese patent application publication No. CN112142077a, lithium iron phosphate is oxidized into ferric phosphate by using air as an oxidant, and lithium carbonate product is obtained by removing impurities and precipitating lithium; then mixing water leaching slag, iron powder and a small amount of phosphoric acid, performing ball milling, activating and reducing, stirring and dissolving out the solid product obtained after activation by using a phosphoric acid solution, filtering to obtain an iron and phosphorus solution, obtaining an iron phosphate precipitate by adopting a high-temperature evaporation crystallization method, and aging, washing and calcining to obtain the iron phosphate for the battery; the oxidant used in the scheme is air, the efficiency of leaching and separating lithium is low, in addition, although the phosphoric acid leaching mode is adopted to recycle the ferric phosphate, the ball milling activation is needed in the preparation process, the ferric phosphate seed crystal is also needed to be added, and then the reaction, washing and calcination are carried out, so that the steps are very complex and complicated, the cost is high, and the economic benefit is low.
Disclosure of Invention
In view of the above, the present invention is necessary to provide a method for recycling the positive electrode powder of the waste lithium iron phosphate battery, which realizes the full recycling and high conversion rate of lithium, phosphorus and iron elements in the positive electrode powder of the waste lithium iron phosphate, and the prepared lithium carbonate and iron phosphate reach the battery level standard.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the invention provides a recycling method of waste lithium iron phosphate anode powder, which comprises the following steps:
acid-dissolving waste lithium iron phosphate anode powder by adopting nitric acid and sodium hypochlorite to obtain acid-leaching liquid;
heating the pickle liquor to remove acid, adjusting the pH value to 1.5-2.0, and carrying out suction filtration to obtain lithium-containing liquor and ferric phosphate filter residues;
removing impurities from the lithium-containing liquid, precipitating lithium, and performing carbonization pyrolysis to obtain battery-grade lithium carbonate;
and (3) carrying out solid-phase electrolysis and chemical precipitation on the iron phosphate filter residues, and then carrying out recycling electrolysis to obtain the battery grade iron phosphate.
Further, in the waste lithium iron phosphate positive electrode powder, the mass percentages of the elements are respectively as follows: 3.6% -4.4%, fe:33% -34%, P:22% -24%, al:0.1% -0.9%, cu:0.01% -0.02%, mg:1% -2%, ca:3% -4%.
Further, the acid leaching solution is obtained by the following steps: mixing, heating and stirring waste lithium iron phosphate anode powder with pure water to obtain slurry; adding nitric acid and sodium hypochlorite into the slurry to perform acid dissolution, and continuously stirring until the slurry fully reacts to obtain pickle liquor;
preferably, in the slurry, the solid-liquid mass ratio of the waste lithium iron phosphate anode powder to water is 1:1.5-2.5;
preferably, the concentration of the nitric acid is 3-6mol/L; the dosage ratio of the nitric acid to the lithium iron phosphate anode powder is 3-5:1 (mL/g).
Further, the heating and stirring speed of the slurry is 700-1000r/min, the heating temperature is 60-90 ℃, and the reaction time is 1-1.5h; the stirring speed of the pickle liquor is 200-300r/min.
Further scheme, the temperature of heating acid removal is 86-95 ℃ and the time is 1-1.5h.
Further, the steps of removing impurities and precipitating lithium specifically comprise:
adding sodium hydroxide solution into the lithium-containing liquid, adjusting the pH value to remove impurities, and filtering to obtain lithium-containing pure liquid;
carrying out lithium precipitation reaction on the lithium-containing pure solution and a sodium carbonate solution to obtain lithium carbonate precipitation;
preferably, the pH of the removed impurities is 11-13;
preferably, the concentration of the sodium carbonate solution is 210-250g/L.
Further, the carbonization pyrolysis comprises the following steps:
adding water into the lithium carbonate precipitate to prepare slurry, and introducing carbon dioxide to generate a lithium bicarbonate solution;
and heating the lithium bicarbonate solution to obtain the battery grade lithium carbonate.
Further, the process of the solid-phase electrolyte specifically comprises the following steps:
electrolyzing the iron phosphate filter residues under a phosphoric acid system;
preferably, the concentration of phosphoric acid adopted by the electrolysis is 0.5-1mol/L, the electrolysis voltage is 2.0-3.0V, and the electrolysis time is 60-90min.
Further, the chemical precipitation comprises the following steps:
and (3) regulating the pH value of the electrolyte after solid-liquid separation to 1.5-2.0 by using ammonia water, heating for reaction, and filtering to obtain filtrate and ferric phosphate dihydrate precipitate.
Further, the steps of the cyclic electrolysis are specifically as follows: the solid phase electrolysis process is repeated at 70-90 ℃ for 3-5 hours.
The beneficial effects of the invention are as follows:
according to the invention, nitric acid is used for acid leaching of waste lithium iron phosphate, and the method of acid leaching and acid removal by heating is used for extracting lithium, so that the nitric acid is decomposed into nitrogen dioxide and water when meeting heat energy, and therefore, excessive acid can be directly removed by heating, the problems of high subsequent water consumption and the like are solved, and the production cost is reduced.
The invention creatively combines the traditional wet process lithium extraction with the solid-phase electrolysis method, firstly extracts lithium through the traditional wet process, and then extracts ferric phosphate in the ferric phosphate slag through the electrolysis method. The electrolytic method has simple steps, less pollution and high efficiency, and the two are perfectly combined, so that the full recovery and high conversion rate of lithium, phosphorus and iron elements in the waste lithium iron phosphate positive electrode powder are realized; meanwhile, the prepared lithium carbonate and ferric phosphate reach the battery level standard.
Drawings
FIG. 1 is a flow chart of a method for recycling anode powder of a waste lithium iron phosphate battery according to a preferred embodiment of the invention.
Detailed Description
The following detailed description of embodiments of the invention is exemplary and is provided merely to illustrate the invention and is not to be construed as limiting the invention.
Unless defined otherwise, 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 invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The embodiment of the invention discloses a recycling method of waste lithium iron phosphate positive electrode powder, wherein the waste lithium iron phosphate positive electrode powder refers to a lithium iron phosphate positive electrode material obtained by a conventional recycling method in the field, the composition of the material is not particularly limited, and in some typical embodiments of the invention, the mass percentages of elements in the waste lithium iron phosphate positive electrode powder are as follows: li:3.6% -4.4%, fe:33% -34%, P:22% -24%, al:0.1% -0.9%, cu:0.01% -0.02%, mg:1% -2%, ca:3% -4%.
In a preferred embodiment of the present invention, the method for recycling the waste lithium iron phosphate positive electrode powder mainly comprises the following steps:
obtaining pickle liquor
Mixing, heating and stirring waste lithium iron phosphate anode powder with pure water to obtain slurry; and adding nitric acid and sodium hypochlorite into the slurry to perform acid dissolution, and continuously stirring until the slurry fully reacts to obtain pickle liquor.
The ferrous ions are oxidized to ferric ions by adding nitric acid to provide a hydrogen ion, providing an acidic environment, and adding sodium hypochlorite as a strong oxidizer. During this process, an excess of sodium hypochlorite is maintained, ensuring a complete reaction, so that all ferrous ions are oxidized.
In the slurry, the solid-liquid mass ratio of the waste lithium iron phosphate anode powder to the pure water is 1:1.5-2.5; in the slurrying process, the heating and stirring speed is 700-1000r/min, the heating temperature is 60-90 ℃, and the reaction time is 1-1.5h; the stirring speed of the pickle liquor is 200-300r/min.
In order to ensure that the leaching rate of lithium ions is the highest, preferably, the concentration of nitric acid adopted by acid dissolution is 3-6mol/L; the dosage ratio of the nitric acid to the lithium iron phosphate anode powder is 3-5:1 (mL/g).
Obtaining lithium-containing liquid and ferric phosphate filter residues
Heating the pickle liquor to remove excessive nitric acid to obtain acid-removed liquor; and after the acid solution is removed, cooling to room temperature, controlling the pH value of the solution to be 1.5-2.0, and carrying out suction filtration after the reaction is completed to obtain lithium-containing solution and ferric phosphate filter residues. The method of acid leaching and heating acid removal is used for extracting lithium, and the nitric acid is decomposed into nitrogen dioxide and water when meeting heat energy, so that the excessive acid can be directly removed by heating, the problems of more subsequent water consumption and the like are solved, and the production cost is reduced. Controlling the pH of the acid removal liquid to control the generation of ferric phosphate, wherein when the pH value is too low, the phosphate ions react with hydrogen ions to generate hydrogen phosphate ions or dihydrogen phosphate ions; and Shi Tie ions with too high pH value react with hydroxide ions to produce ferric hydroxide.
Wherein the temperature for heating and removing acid is 86-95deg.C for 1-1.5h.
Obtaining the battery grade lithium carbonate
Mainly comprises the following steps:
removing impurities and precipitating lithium: adding sodium hydroxide solution into the lithium-containing liquid, adjusting the pH value to remove impurities, and filtering to obtain lithium-containing pure liquid; and carrying out lithium precipitation reaction on the lithium-containing pure solution and the sodium carbonate solution to obtain lithium carbonate precipitate. Wherein, the pH is adjusted to 11-13, and the concentration of the adopted sodium carbonate is 210-250g/L.
Carbonization and pyrolysis: adding water into lithium carbonate precipitate obtained after impurity removal and lithium precipitation to prepare slurry, and introducing carbon dioxide to generate lithium bicarbonate solution; and heating the lithium bicarbonate solution to obtain the battery grade lithium carbonate.
Obtaining battery grade ferric phosphate
The method comprises the following specific steps:
carrying out solid-phase electrolysis on the iron phosphate filter residues under a phosphoric acid system, wherein the concentration of phosphoric acid adopted in the electrolysis is 0.3-1mol/L, preferably 0.5-1mol/L; the electrolysis voltage is 2.0-3.0V, and the electrolysis time is 60min;
adjusting the pH of the electrolyte after solid-liquid separation to 1.5-2.0 by using ammonia water, heating the electrolyte at 60-90 ℃ for reaction, and filtering to obtain filtrate and ferric phosphate dihydrate precipitate;
and (3) repeating the solid-phase electrolysis step for cyclic electrolysis on the filtrate obtained after the chemical precipitation, and carrying out precipitation and drying on the finally obtained ferric phosphate dihydrate to obtain the battery-grade ferric phosphate, wherein the cyclic electrolysis process is specifically that the solid-phase electrolysis process is repeated for 3-5 hours at 70-90 ℃, and the purity and the recovery rate of the obtained ferric phosphate are improved through cyclic electrolysis.
The present invention will be illustrated by the following examples, which are given for illustrative purposes only and are not intended to limit the scope of the present invention in any way, and unless otherwise specified, the conditions or procedures not specifically described are conventional and the reagents and materials employed are commercially available.
Example 1
The recycling method of the waste lithium iron phosphate battery positive electrode powder in the embodiment, wherein the content of each element in the waste lithium iron phosphate positive electrode powder is respectively 3.61% of Li, 33.36% of Fe, 22.37% of P, 0.11% of Al, 0.01% of Cu, 1.17% of Mg and 3.32% of Ca, and the specific recycling method is as follows:
s1, acid leaching: weighing 100g of waste lithium iron phosphate anode powder, adding pure water into the waste lithium iron phosphate anode powder, wherein the mass ratio of the lithium iron phosphate anode powder to the water is 1:1.5, and heating and stirring the mixture at 60 ℃ for 1h to obtain slurry; adding 3mol/L nitric acid and sodium hypochlorite into the slurry for acid dissolution, wherein the dosage ratio of the nitric acid to the lithium iron phosphate is 3:1 (mL/g) when the sodium hypochlorite is 10% excessive, and continuously stirring for 1.5h at the rotating speed of 700r/min to fully react to obtain the pickle liquor.
S2, filtering: heating the pickle liquor obtained in the step S1 at 86 ℃ for 1h, and removing excessive nitric acid to obtain acid-removed liquor; after the acid solution is cooled to room temperature, controlling the pH value of the solution to be 1.5; after the reaction is completed, carrying out suction filtration to obtain lithium-containing liquid and ferric phosphate filter residues;
s3, removing impurities and precipitating lithium: adding sodium hydroxide solution into the lithium-containing solution obtained in the step S2, adjusting the pH value of the solution to 11, removing impurities, and filtering to obtain lithium-containing pure solution; carrying out lithium precipitation reaction on the lithium-containing pure solution and a sodium carbonate solution with the concentration of 210g/L to obtain lithium carbonate precipitate;
s4, carbonization pyrolysis: adding water into the lithium carbonate obtained in the step S3 to prepare slurry, introducing carbon dioxide to generate a lithium bicarbonate solution, and then heating the lithium bicarbonate solution to obtain battery-grade lithium carbonate;
s5, solid-phase electrolysis: electrolyzing the iron phosphate filter residue in the step S2, wherein the concentration of the phosphoric acid electrolyte is 0.3mol/L, the electrolysis voltage is 2.3V, and the electrolysis time is 1h;
s6, chemical precipitation: adjusting the pH value of the electrolyte after solid-liquid separation in the step S5 to 1.5 by using ammonia water, heating for reaction, and then filtering to obtain filtrate and ferric phosphate dihydrate precipitate;
s7, cyclic electrolysis: and (3) repeating the step (S5) for cyclic electrolysis on the filtrate obtained in the step (S6), and drying the finally obtained dihydrate ferric phosphate precipitate to obtain the battery grade ferric phosphate.
Example 2
The recycling method of the waste lithium iron phosphate battery positive electrode powder in the embodiment, wherein the content of each element in the waste lithium iron phosphate positive electrode powder is respectively 3.98% of Li, 33.41% of Fe, 22.56% of P, 0.18% of Al, 0.01% of Cu, 1.15% of Mg and 3.81% of Ca, and the specific recycling method is as follows:
s1, acid leaching: weighing 100g of waste lithium iron phosphate positive electrode powder, adding pure water into the powder, heating and stirring the powder for 1h at 80 ℃ to obtain slurry, wherein the solid-liquid mass ratio of the lithium iron phosphate positive electrode powder to the water is 1:2; adding 3mol/L nitric acid and sodium hypochlorite into the slurry for acid dissolution, wherein the dosage ratio of the nitric acid to the lithium iron phosphate is 4:1 (mL/g) when the sodium hypochlorite is excessive by 15%, and continuously stirring for 2 hours at the rotating speed of 850r/min until the acid leaching solution is fully reacted, thereby obtaining the acid leaching solution.
S2, filtering: heating the pickle liquor obtained in the step S1 at 90 ℃ for 1.5 hours, and removing excessive nitric acid to obtain acid-removed liquor; after the acid solution is cooled to room temperature, controlling the pH value of the solution to be 1.65; after the reaction is completed, carrying out suction filtration to obtain lithium-containing liquid and ferric phosphate filter residues;
s3, removing impurities and precipitating lithium: adding sodium hydroxide solution into the lithium-containing solution obtained in the step S2, adjusting the pH value of the solution to 11, removing impurities, and filtering to obtain lithium-containing pure solution; and carrying out lithium precipitation reaction on the lithium-containing pure solution and a sodium carbonate solution with the concentration of 225g/L to obtain lithium carbonate precipitate.
S4, carbonization pyrolysis: and (3) adding water into the lithium carbonate in the step (S3) to prepare slurry, introducing carbon dioxide to generate a lithium bicarbonate solution, and heating the lithium bicarbonate solution to obtain the battery-grade lithium carbonate.
S5, solid-phase electrolysis: electrolyzing the iron phosphate filter residue in the step S2, wherein the concentration of the phosphoric acid electrolyte is 0.6mol/L, the electrolysis voltage is 2.5V, and the electrolysis time is 1h;
s6, chemical precipitation: adjusting the pH value of the electrolyte after solid-liquid separation in the step S5 to 1.6 by using ammonia water, heating for reaction, and then filtering to obtain filtrate and ferric phosphate dihydrate precipitate;
s7, cyclic electrolysis: and (3) repeating the step (S5) for cyclic electrolysis on the filtrate obtained in the step (S6), and drying the finally obtained dihydrate ferric phosphate precipitate to obtain the battery grade ferric phosphate.
Example 3
The recycling method of the waste lithium iron phosphate battery positive electrode powder in the embodiment, wherein the content of each element in the waste lithium iron phosphate positive electrode powder is respectively 4.1% of Li, 33.49% of Fe, 23.1% of P, 0.30% of Al, 0.02% of Cu, 1.19% of Mg and 3.66% of Ca, and the specific recycling method is as follows:
s1, acid leaching: weighing 100g of waste lithium iron phosphate positive electrode powder, adding pure water into the powder, heating and stirring the powder for 1h at 90 ℃ to obtain slurry, wherein the solid-liquid mass ratio of the lithium iron phosphate positive electrode powder to the water is 1:2.5; adding 3mol/L nitric acid and sodium hypochlorite into the slurry for acid dissolution, wherein the dosage ratio of the nitric acid to the lithium iron phosphate is 4:1 (mL/g) when the sodium hypochlorite is 10% excessive, and continuously stirring for 2 hours at the rotating speed of 850r/min until the acid leaching solution is fully reacted, thereby obtaining the acid leaching solution.
S2, filtering: heating the pickle liquor obtained in the step S1 at 90 ℃ for 1.5 hours, and removing excessive nitric acid to obtain acid-removed liquor; after the acid solution is cooled to room temperature, controlling the pH value of the solution to be 1.65; after the reaction is completed, carrying out suction filtration to obtain lithium-containing liquid and ferric phosphate filter residues;
s3, removing impurities and precipitating lithium: adding sodium hydroxide solution into the lithium-containing solution obtained in the step S2, adjusting the pH value of the solution to 12, removing impurities, and filtering to obtain lithium-containing pure solution; and carrying out lithium precipitation reaction on the lithium-containing pure solution and a sodium carbonate solution with the concentration of 225g/L to obtain lithium carbonate precipitate.
S4, carbonization pyrolysis: and (3) adding water into the lithium carbonate in the step (S3) to prepare slurry, introducing carbon dioxide to generate a lithium bicarbonate solution, and heating the lithium bicarbonate solution to obtain the battery-grade lithium carbonate.
S5, solid-phase electrolysis: electrolyzing the iron phosphate filter residue in the step S2, wherein the concentration of the phosphoric acid electrolyte is 1mol/L, the electrolysis voltage is 3V, and the electrolysis time is 1.5h;
s6, chemical precipitation: adjusting the pH value of the electrolyte after solid-liquid separation in the step S5 to 1.7 by using ammonia water, heating for reaction, and then filtering to obtain filtrate and ferric phosphate dihydrate precipitate;
s7, cyclic electrolysis: and (3) repeating the step (S5) for cyclic electrolysis on the filtrate obtained in the step (S6), and drying the finally obtained dihydrate ferric phosphate precipitate to obtain the battery grade ferric phosphate.
Comparative example 1
The present comparative example uses the same embodiment as in example 2, except that: this comparative example does not remove excess nitric acid by heating, but uses sulfuric acid for pickling. The specific recycling method in this comparative example is as follows:
s1, acid leaching: weighing 100g of waste lithium iron phosphate positive electrode powder, adding pure water into the powder, heating and stirring the powder for 1h at 80 ℃ to obtain slurry, wherein the dosage ratio of the lithium iron phosphate positive electrode powder to the water is 1:2; adding 3mol/L sulfuric acid and sodium hypochlorite into the slurry for acid dissolution, wherein the dosage ratio of the sodium hypochlorite to the lithium iron phosphate is 4:1 (mL/g), and continuously stirring at the rotating speed of 850r/min for 2h until the acid leaching solution is obtained.
S2, filtering: adjusting the pH value of the pickle liquor to 1.65; after the reaction is completed, carrying out suction filtration to obtain lithium-containing liquid and ferric phosphate filter residues;
s3, removing impurities and precipitating lithium: as in example 2, lithium carbonate precipitate was obtained.
S4, carbonization pyrolysis: as in example 2, battery grade lithium carbonate was obtained.
S5, solid-phase electrolysis: same as in example 2;
s6, chemical precipitation: same as in example 2;
s7: and (3) cyclic electrolysis: as in example 2, a battery grade iron phosphate was obtained.
Comparative example 2
This comparative example uses the same embodiment as that of example 2, except that: no cyclic electrolysis is performed. The specific recycling method in this comparative example is as follows:
s1, acid leaching: an pickle liquor was obtained as in example 2.
S2, filtering: as in example 2, a lithium-containing solution and iron phosphate filter residue were obtained;
s3, removing impurities and precipitating lithium: as in example 2, a lithium carbonate precipitate was obtained.
S4, carbonization pyrolysis: as in example 2, battery grade lithium carbonate was obtained.
S5, solid-phase electrolysis: as in example 2.
S6, chemical precipitation: and (3) adjusting the pH value of the electrolyte after solid-liquid separation in the step (S5) to 1.6 by using ammonia water, heating for reaction, filtering to obtain filtrate and ferric phosphate dihydrate precipitate, and drying the obtained ferric phosphate dihydrate precipitate to obtain the battery grade ferric phosphate.
Performance testing
Recovery and purity tests were performed on the battery grade lithium carbonate and iron phosphate obtained in examples 1-3 and comparative examples 1-2, and the test results are shown in table 1.
TABLE 1 recovery and purity test results of lithium carbonate and iron phosphate
| Project | Example 1 | Example 2 | Example 3 | Comparative example 1 | Comparative example 2 |
| Recovery rate of lithium carbonate | 98.51％ | 98.95％ | 96.12％ | 92.08％ | 93.25％ |
| Purity of lithium carbonate | 99.36％ | 99.88％ | 99.63％ | 99.48％ | 99.52％ |
| Recovery rate of iron phosphate | 98.8％ | 99.2％ | 97.6％ | 94.6％ | 95.51％ |
| Purity of iron phosphate | 99.26％ | 99.62％ | 99.11％ | 94.3％ | 96.82％ |
As can be seen from the test results in table 1, in the three examples, the recovery rates of lithium carbonate and iron phosphate of the waste lithium iron phosphate were all 96% or more, and the purity of the lithium carbonate was battery grade; in comparative example 1, the recovery rate of lithium carbonate and iron phosphate obtained by acid leaching using sulfuric acid without removing excess nitric acid by heating method was only 92.08% and 94.6%, which is significantly lower than the recovery rate of lithium carbonate obtained in each example; in comparative example 2, the recovery rate of lithium carbonate and iron phosphate obtained without cyclic electrolysis was 93.25% and 95.51%, respectively, lower than that obtained in each example.
According to the test results, the method for recycling the waste lithium iron phosphate and preparing the lithium carbonate and the ferric phosphate by adopting the recycling method can obviously improve the recycling rate of the lithium carbonate and the ferric phosphate and the purity of the lithium carbonate and the ferric phosphate, and has strong practicability.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (10)
1. The method for recycling the anode powder of the waste lithium iron phosphate battery is characterized by comprising the following steps of:
acid-dissolving waste lithium iron phosphate anode powder by adopting nitric acid and sodium hypochlorite to obtain acid-leaching liquid;
heating the pickle liquor to remove acid, adjusting the pH value to 1.5-2.0, and carrying out suction filtration to obtain lithium-containing liquor and ferric phosphate filter residues;
removing impurities from the lithium-containing liquid, precipitating lithium, and performing carbonization pyrolysis to obtain battery-grade lithium carbonate;
and (3) carrying out solid-phase electrolysis and chemical precipitation on the iron phosphate filter residues, and then carrying out recycling electrolysis to obtain the battery grade iron phosphate.
2. The recycling method of claim 1, wherein the mass percentages of the elements in the waste lithium iron phosphate positive electrode powder are respectively as follows: 3.6% -4.4%, fe:33% -34%, P:22% -24%, al:0.1% -0.9%, cu:0.01% -0.02%, mg:1% -2%, ca:3% -4%.
3. The recycling method according to claim 1, characterized in that the step of obtaining the pickling liquid comprises: mixing, heating and stirring waste lithium iron phosphate anode powder with pure water to obtain slurry; adding nitric acid and sodium hypochlorite into the slurry to perform acid dissolution, and continuously stirring until the slurry fully reacts to obtain pickle liquor;
preferably, in the slurry, the solid-liquid mass ratio of the waste lithium iron phosphate anode powder to water is 1:1.5-2.5;
preferably, the concentration of the nitric acid is 3-6mol/L; the dosage ratio of the nitric acid to the lithium iron phosphate anode powder is 3-5:1 (mL/g).
4. The recycling method according to claim 3, wherein the slurry is heated and stirred at a rate of 700-1000r/min, a heating temperature of 60-90 ℃ and a reaction time of 1-1.5h; the stirring speed of the pickle liquor is 200-300r/min.
5. The recycling method according to claim 1, wherein the temperature of the heating acid removal is 86-95 ℃ for 1-1.5 hours.
6. The recycling method according to claim 1, wherein the step of removing impurities and precipitating lithium comprises the steps of:
adding sodium hydroxide solution into the lithium-containing liquid, adjusting the pH value to remove impurities, and filtering to obtain lithium-containing pure liquid;
carrying out lithium precipitation reaction on the lithium-containing pure solution and a sodium carbonate solution to obtain lithium carbonate precipitation;
preferably, the pH of the removed impurities is 11-13;
preferably, the concentration of the sodium carbonate solution is 210-250g/L.
7. The recycling method according to claim 6, wherein the step of carbonization pyrolysis is specifically:
adding water into the lithium carbonate precipitate to prepare slurry, and introducing carbon dioxide to generate a lithium bicarbonate solution;
and heating the lithium bicarbonate solution to obtain the battery grade lithium carbonate.
8. The recycling method according to claim 1, wherein the process of the solid phase electrolyte is specifically as follows:
electrolyzing the iron phosphate filter residues under a phosphoric acid system;
preferably, the concentration of phosphoric acid adopted by the electrolysis is 0.5-1mol/L, the electrolysis voltage is 2.0-3.0V, and the electrolysis time is 60-90min.
9. The recycling method according to claim 1, wherein the step of chemical precipitation is specifically:
and (3) regulating the pH value of the electrolyte after solid-liquid separation to 1.5-2.0 by using ammonia water, heating for reaction, and filtering to obtain filtrate and ferric phosphate dihydrate precipitate.
10. The recycling method according to claim 1, characterized in that the step of cyclic electrolysis is in particular: the solid phase electrolysis process is repeated at 70-90 ℃ for 3-5 hours.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116835543A (en) * | 2023-07-07 | 2023-10-03 | 江西华赛新材料有限公司 | Lithium iron phosphate powder recovery process |
| CN116902999A (en) * | 2023-05-31 | 2023-10-20 | 广东盛祥新材料科技有限公司 | Ternary powder/lithium iron powder/lithium carbonate processing method and waste battery recycling method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116902999A (en) * | 2023-05-31 | 2023-10-20 | 广东盛祥新材料科技有限公司 | Ternary powder/lithium iron powder/lithium carbonate processing method and waste battery recycling method |
| CN116835543A (en) * | 2023-07-07 | 2023-10-03 | 江西华赛新材料有限公司 | Lithium iron phosphate powder recovery process |
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