Method for recycling waste lithium iron phosphate battery powder

Abstract

The application discloses a method for recycling waste lithium iron phosphate battery powder, comprising the following steps: S1, mixing the waste lithium iron phosphate battery powder with additives and then grinding; S2, calcining the ground material at 400-550 DEG C for 1.5-2.5 h; S3, water immersion of the calcined material at a liquid-solid ratio of 5:1-10:1; S4, adding sodium hydroxide solution to the water immersion filtrate obtained in step S3, and adjusting the pH to 4.0-5.0; S5, evaporating and crystallizing the iron and aluminum removed solution obtained in step S4 through ion exchange resin deep impurity removal, and then filtering and drying; S6, washing the water immersion residue obtained in step S3 with sodium hydroxide solution to remove aluminum; S7, acid leaching of the washed residue obtained in step S6 with sulfuric acid; S8, adding hydrogen peroxide to the acid leaching solution for oxidation; S9, adding sodium carbonate solution to the oxidized solution to obtain regenerated iron phosphate product.

Description

Technical Field

[0001] This invention relates to the technical field of waste lithium battery recycling methods, and in particular to a method for recycling waste lithium iron phosphate battery powder. Background Technology

[0002] Currently, lithium iron phosphate batteries are widely used as one of the mainstream power batteries. However, as the first batch of power batteries gradually enters their retirement period, the recycling and disposal of used lithium iron phosphate batteries has become an urgent problem to be solved. Used lithium iron phosphate batteries contain valuable metal elements such as lithium, iron, and phosphorus, and have high recycling value. At the same time, improper disposal can also cause environmental pollution.

[0003] Currently, recycling technologies for spent lithium iron phosphate batteries mainly fall into two categories: pyrometallurgical and hydrometallurgical processes. Chinese patent CN109207730A discloses a method for recovering lithium sulfate and iron phosphate from spent lithium iron phosphate batteries using a hydrometallurgical alkaline dissolution-acid leaching-extraction process. This method involves recovering lithium through alkaline dissolution, acid leaching, and then extraction separation. US patent US20210032721A1 describes a recovery method that involves leaching pulverized battery materials with dilute sulfuric acid and an aqueous reducing agent at a pH greater than 3.5, followed by filtration and precipitation of valuable metals from the filtrate. However, traditional hydrometallurgical recycling processes suffer from low lithium recovery rates; the leaching rate is often difficult to achieve ideal levels, and the recovery value of iron phosphate is relatively low.

[0004] To address the limitations of wet recycling, researchers have begun exploring recycling routes that combine pyrometallurgical and wet processes. International patent WO2022134749A1 discloses a technology that repairs lithium iron phosphate through pyrometallurgical calcination followed by wet recycling of iron phosphate. This method involves extracting lithium during pyrometallurgical calcination and achieving secondary utilization of the material. Chinese patent CN118676466A provides a recycling process for spent lithium iron phosphate batteries, involving pyrometallurgical calcination to extract lithium followed by wet leaching to recover iron and phosphorus. Chinese patent CN115072688B discloses a method for the complete recycling of spent lithium iron phosphate batteries, employing a combination of pyrometallurgical and wet processes, but points out that pyrometallurgical processes at high temperatures can produce toxic exhaust gases due to the decomposition of organic matter, which is detrimental to the environment. Li H et al., in a journal article, conducted a multi-faceted evaluation of spent lithium iron phosphate recycling processes, analyzing the advantages and disadvantages of wet full extraction processes and pyrometallurgical recycling processes. Saju D et al., in a review article, summarized the recycling technologies for lithium iron phosphate cathode materials, focusing on the application of pyrometallurgical and wet technologies. The review paper by Jing C et al. analyzed the technologies for recovering lithium and iron from spent lithium iron phosphate batteries, and compared the advantages and disadvantages of pyrometallurgical, hydrometallurgical and mechanochemical methods.

[0005] Although existing technologies have explored recovery routes combining pyrometallurgical and hydrometallurgical processes, the following problems remain: First, the separation efficiency of elements such as lithium, iron, and aluminum is low during the water leaching process after pyrometallurgical calcination, leading to complex subsequent impurity removal processes; second, residual impurities such as aluminum in the water leaching residue affect the purity and quality of the iron phosphate product; and third, existing processes have not achieved an optimal balance between lithium extraction and iron phosphate recovery, and the overall economic efficiency of recovery needs to be improved. Therefore, it is necessary to develop an improved process that can increase lithium yield while efficiently recovering high-purity iron phosphate. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for recycling waste lithium iron phosphate battery powder.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A method for recycling waste lithium iron phosphate battery powder includes the following steps: S1. Mix the waste lithium iron phosphate battery powder and additives at a mass ratio of 1:1.2 and then grind them for 20-30 minutes. S2. Calcine the ground material at 400-550℃ for 1.5-2.5 hours; S3. The calcined material is soaked in water at a liquid-solid ratio of 5:1-10:1, the water soaking temperature is 60-80℃, the water soaking time is 1-2h, and after leaching, it is washed and filtered to obtain water-leached filtrate and water-leached filter residue. S4. Add sodium hydroxide solution to the water leaching filtrate obtained in step S3, adjust the pH to 4.0-5.0, and perform iron and aluminum removal treatment to obtain the iron and aluminum removed liquid. S5. The liquid obtained in step S4 after removing iron and aluminum is subjected to deep impurity removal by ion exchange resin, then evaporated and crystallized, filtered and dried to obtain lithium hydroxide. S6. Wash the water-impregnated filter residue obtained in step S3 with sodium hydroxide solution to remove aluminum, and obtain the washed filter residue. S7. Use sulfuric acid to leach the washed filter residue obtained in step S6 to obtain an acid leaching solution. S8. Add hydrogen peroxide to the acid leaching solution to oxidize it, so that ferrous ions are converted into ferric ions. S9. Add sodium carbonate solution to the oxidized solution, adjust the pH to 2.0-3.0, filter, wash with hot water and dry to obtain the regenerated iron phosphate product.

[0008] In step S1, grinding is performed using a planetary ball mill.

[0009] In step S4, the temperature for iron and aluminum removal treatment is 60-80℃, and the time is 2-3 hours.

[0010] In step S6, the concentration of the sodium hydroxide solution is less than 8%.

[0011] In step S7, the liquid-to-solid ratio of acid leaching is 4:1-5:1, the acid leaching temperature is 60-80℃, the acid leaching time is 2-3h, and the amount of sulfuric acid added is such that the pH reaches 1.

[0012] In step S9, the concentration of the sodium carbonate solution is 20-40%, the precipitation temperature is 60-80℃, the precipitation time is 2-3 hours, and the final pH is 2.5.

[0013] In step S9, the hot water washing is performed 5-8 times.

[0014] The beneficial effects of this invention are: 1. This invention involves mixing and grinding waste lithium iron phosphate battery powder with additives for 20-30 minutes, followed by calcination at 400-550℃ for 1.5-2.5 hours to convert lithium into a water-soluble compound. The calcined material is then soaked in water at 60-80℃ for 1-2 hours at a liquid-to-solid ratio of 5:1-10:1, yielding a lithium-rich filtrate and a phosphorus-containing iron residue, with a lithium leaching rate exceeding 95%. The filtrate undergoes iron and aluminum removal, deep impurity removal via ion exchange, and then evaporation and crystallization to obtain battery-grade lithium hydroxide. The residue is subjected to alkaline washing to remove aluminum, sulfuric acid leaching, and hydrogen peroxide oxidation, followed by pH adjustment and precipitation to obtain a high-purity regenerated iron phosphate product. This method solves the problem of low lithium recovery in traditional wet recycling, achieving efficient separation and high-value recovery of lithium and phosphorus-iron, with a lithium recovery rate exceeding 92% and a phosphorus-iron recovery rate exceeding 95%.

[0015] 2. Lithium is preferentially extracted by pyrometallurgical calcination, and then phosphorus iron is separated and recovered by wet leaching, which achieves efficient separation of lithium and phosphorus iron. The leaching rate of lithium can reach more than 95%, and the leaching rate of phosphorus iron can reach more than 99%, which significantly improves the recovery efficiency.

[0016] 3. The filtrate and filter residue after water immersion are subjected to targeted impurity removal treatments. The filtrate is treated to remove iron and aluminum by adjusting the pH to 4.0-5.0 with sodium hydroxide solution, and the filter residue is washed with sodium hydroxide solution to remove aluminum. This effectively improves the purity of lithium products and regenerated iron phosphate products and reduces the impact of impurities on subsequent processes.

[0017] 4. By optimizing the parameters of each process step, such as grinding time, calcination temperature and time, water immersion conditions, impurity removal pH range, acid immersion conditions, and precipitation conditions, a complete and efficient pyrometallurgical-hydrometallurgical combined recycling process has been formed, which has improved the economic efficiency and resource utilization rate of waste lithium iron phosphate batteries.

[0018] 5. Hydrogen peroxide is used to oxidize ferrous ions to ferric ions, and then sodium carbonate is used for precipitation to obtain high-purity regenerated iron phosphate. The product has high quality and can be directly used in battery material production, which has good practical value and economic benefits. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention.

[0020] This invention provides a method for recycling waste lithium iron phosphate battery powder, employing a combined pyrometallurgical-hydrometallurgical process to achieve efficient separation and recovery of lithium and iron phosphate. The method includes: mixing waste lithium iron phosphate battery powder with additives and then grinding for 20-30 minutes, preferably using a planetary ball mill to improve grinding efficiency and ensure uniform mixing; calcining the ground material at 400-550℃ for 1.5-2.5 hours, where pyrometallurgical calcination preferentially breaks down the lithium iron phosphate crystal structure, converting lithium into water-soluble compounds; leaching the calcined material in water at a liquid-to-solid ratio of 5:1-10:1 at 60-80℃ for 1-2 hours; washing and filtering the leachate to obtain a lithium-rich leachate and an iron phosphate-containing leachate residue, achieving a lithium leaching rate of over 95%; adding a 100-200 g / L sodium hydroxide solution to the leachate to adjust the pH to 4.0-5.0. The reaction is carried out at 60-80℃ for 2-3 hours to remove iron and aluminum impurities from the filtrate by precipitation, resulting in a post-iron and aluminum removed liquid. This post-iron and aluminum removed liquid is then subjected to deep impurity removal via ion exchange resin, followed by evaporation and crystallization, filtration, and drying to obtain battery-grade lithium hydroxide product. The water-leached filter residue is washed with an 8% sodium hydroxide solution to remove aluminum impurities, effectively removing aluminum from the filter residue while avoiding excessive corrosion of the ferrophosphorus, resulting in a washed filter residue. The washed filter residue is then acid-leached with sulfuric acid at a liquid-to-solid ratio of 4:1-5:1, an acid-leaching temperature of 60-80℃, and an acid-leaching time of 2-3 hours. The amount of sulfuric acid added is adjusted to achieve a pH of 1, ensuring a ferrophosphorus leaching rate of over 99%, resulting in an acid-leaching solution containing ferrous ions. Excess hydrogen peroxide is added to the acid-leaching solution for oxidation, completely converting the ferrous ions to ferric ions. A 20-40% sodium carbonate solution is added to the oxidized solution to adjust the pH to 2.0-3.0. The mixture is reacted at 60-80℃ for 2-3 hours to precipitate ferric phosphate. After filtration, the precipitate is washed 5-8 times with hot water to thoroughly remove residual impurities. After drying, a high-purity regenerated ferric phosphate product is obtained, with a phosphorus and iron precipitation rate of over 98%. This method preferentially extracts lithium through pyrometallurgical calcination, solving the problem of low lithium yield in traditional wet recovery methods. Furthermore, targeted impurity removal treatments are applied to the filtrate and filter residue after water leaching, resulting in battery-grade lithium hydroxide and regenerated ferric phosphate products. This achieves efficient separation and high-value recovery of lithium and ferric phosphate.

[0021] Example 1: This example systematically demonstrates the complete process flow for recycling waste lithium iron phosphate battery powder under medium calcination temperature and high liquid-to-solid ratio conditions. Process Principle: During high-temperature calcination, lithium iron phosphate undergoes a solid-phase reaction with additives (such as sulfates), preferentially converting lithium elements into soluble lithium salts. Subsequent water leaching achieves preliminary separation of lithium and lithium iron phosphate. Specific steps are as follows: Weigh 100g of waste lithium iron phosphate battery powder (purity ≥95%, particle size <200 mesh) and mix it evenly with an appropriate amount of additives (mass ratio 1:1.2). Place the mixture in a QM-X8L planetary ball mill, setting the ball-to-powder ratio to 2:1, and grinding at 300rpm for 30min to ensure thorough mixing and refinement of the additives and battery powder, thereby improving subsequent reaction activity. Transfer the ground mixture to a corundum crucible and place it in a box-type muffle furnace. Heat the mixture to 450℃ at a rate of 5℃ / min and maintain this temperature for 2 hours. Allow the calcined material to cool naturally to room temperature and weigh it. The calcined material was placed in a 2000 mL beaker and placed on a magnetic stirrer in a constant temperature water bath at a liquid-to-solid ratio of 10:1. The water bath temperature was set to 60℃, the stirring speed to 200 rpm, and the leaching time to 2 hours. After leaching, solid-liquid separation was performed using a vacuum filtration device. The filter residue was washed three times with deionized water (200 mL each time). The wash water and filtrate were combined to obtain approximately 1600 mL of water-leached filtrate. The filter residue was dried (80℃, 4 hours) and weighed to approximately 75 g. Samples were taken from the filtrate and the filter residue to determine the content of Li, Fe, and P elements (using ICP-OES). The calculated leaching rates were 96.5% for lithium, 9.8% for iron, and 8.2% for phosphorus, indicating that the pyrometallurgical-water leaching process successfully achieved preferential extraction of lithium. 1600 mL of the water filtrate was placed in a 3000 mL beaker and placed in a 60℃ constant temperature water bath. A 150 g / L sodium hydroxide solution was slowly added dropwise under magnetic stirring, with real-time pH monitoring. The addition was stopped when the pH reached 4.5, and the reaction was continued with stirring for 3 hours. This step adjusts the pH to cause Fe³⁺ and Al³⁺ in the solution to form hydroxide precipitates. After the reaction, the solution was filtered to obtain approximately 1550 mL of the iron and aluminum-removed liquid. The Fe and Al contents were found to be below 5 ppm and 3 ppm, respectively. The iron and aluminum-removed liquid was then passed through an exchange column packed with D402 ion exchange resin at a flow rate controlled at 2 BV / h (BV is the bed volume) for deep impurity removal, removing residual divalent cation impurities such as Ca²⁺ and Mg²⁺. The total impurity content in the purified liquid was <20 ppm. The purified liquid was transferred to a rotary evaporator, and the water bath temperature was set to 80℃ and the vacuum degree to -0.08MPa. The liquid was evaporated and concentrated to 1 / 5 of the original volume. After cooling to room temperature, a large amount of white crystals precipitated out. After filtration, the crystals were washed twice with anhydrous ethanol and dried in a vacuum drying oven at 80℃ for 6 hours to obtain 21.5g of battery-grade lithium hydroxide product with a purity of 99.2% and a total lithium recovery rate of 93.8%.75g of water-leached filter residue was placed in a 1000mL beaker, and deionized water was added at a liquid-to-solid ratio of 4:1. The beaker was heated to 80℃ in a constant temperature water bath, and a 50g / L sodium hydroxide solution was slowly added dropwise while stirring (low concentration to avoid excessive corrosion) to remove aluminum impurities from the filter residue. After reacting for 1 hour, the residue was filtered, washed, dried, and weighed to approximately 68g. The aluminum content was found to have decreased from 0.8% to 0.12%. The aluminum-removed filter residue was placed in a 1000mL beaker, and 340mL of deionized water was added at a liquid-to-solid ratio of 5:1. The beaker was heated in an 80℃ water bath, and concentrated sulfuric acid (98%, analytical grade) was slowly added dropwise while stirring. The reaction was stopped when the pH reached 1 (approximately 65mL of concentrated sulfuric acid was consumed), and stirring was continued for 2 hours. After the acid leaching reaction was completed, the residue was filtered, and washed twice with deionized water. The wash water and filtrate were combined to obtain approximately 450mL of acid leaching solution. The filter residue was dried and weighed to only 1.2g. The Fe and P contents in the acid leaching solution were measured, and the leaching rates of phosphorus and iron were calculated to reach 99.2%. An excess of 50 mL of 30% hydrogen peroxide solution (H₂O₂:Fe²⁺ molar ratio approximately 1.5:1, ensuring excess) was added to 450 mL of the acid leaching solution. The mixture was stirred at room temperature for 30 min to completely oxidize ferrous ions to ferric ions. After oxidation, a sample was taken to test the solution, and no residual Fe²⁺ was found. The oxidized solution was placed in a 70℃ constant temperature water bath, and a 30% sodium carbonate solution (prepared from analytical grade sodium carbonate) was slowly added dropwise with stirring. The pH was monitored until it reached 2.5, at which point the reaction was stopped, and stirring continued for 3 h. During this process, ferric iron combines with phosphate ions to form ferric phosphate precipitate. pH 2.5 is the optimal pH for ferric phosphate precipitation; a higher pH will result in the formation of Fe(OH)₃, while a lower pH will increase the solubility of ferric phosphate. After the reaction was completed, the mixture was filtered, and the filter residue was washed six times (100 mL each time) with hot deionized water at 80℃ to thoroughly remove residual impurities such as Na⁺ and SO₄²⁻, until the conductivity of the filtrate was <50 μS / cm. The washed filter residue was then dried in an oven at 80℃ for 8 hours to obtain 61.8 g of regenerated ferric phosphate powder. Product characterization: XRD analysis showed that the phase was orthorhombic FePO₄•2H₂O with intact crystal form; ICP-OES analysis showed that the Fe:P molar ratio was 1:1.02, which conformed to the stoichiometric ratio; the total impurity content was <0.3%; the specific surface area (BET method) was 10.5 m² / g. The total recovery rate of ferric phosphate was 96.3%.

[0022] Technical Results: This embodiment achieved efficient lithium extraction under moderate calcination temperature (450℃) and high water-to-solid ratio (10:1), with a lithium leaching rate of 96.5% ± 0.8% and a total lithium recovery rate of 93.8%, yielding a battery-grade lithium hydroxide product with a purity of 99.2%. The ferric phosphorus leaching rate reached 99.2% ± 0.5%, with a total ferric phosphorus recovery rate of 96.3%. The resulting regenerated ferric phosphate product had an Fe:P molar ratio of 1:1.02, a total impurity content of <0.3%, a pure phase (single orthorhombic phase in XRD), and a specific surface area of ​​10.5 m² / g, meeting the standards for regenerated ferric phosphate products. Compared to traditional wet recycling, this method uses pyrometallurgical calcination to preferentially destroy the LiFePO4 lattice and convert it into lithium salt, avoiding the loss of lithium caused by wet strong acid leaching (the lithium yield of traditional methods is only 60-75%). At the same time, it achieves complete separation of lithium and iron phosphate through stepwise impurity removal, solving the technical problem of separating lithium, phosphorus and iron in lithium iron phosphate recycling, and significantly improving recycling efficiency and product value.

[0023] Example 2: Recovery process under high temperature calcination and medium liquid-solid ratio conditions (550℃, liquid-solid ratio 8:1) This embodiment selects the upper limit of the calcination temperature (550℃) and a medium water-to-solid ratio (8:1) within the scope of the claims to investigate the effect of high temperature conditions on lithium conversion efficiency and subsequent recycling effect. 100g of waste lithium iron phosphate battery powder was mixed with additives and ground in a planetary ball mill for 30min. The ground material was placed in a muffle furnace and heated to 550℃ at a rate of 5℃ / min, then calcined at a constant temperature for 1.5h. After cooling, the material was weighed, and the weight loss during calcination was approximately 10-14%. The calcined material was then water-leached at a liquid-to-solid ratio of 8:1 (800mL deionized water), with the water leaching temperature set at 70℃ and a stirring time of 1.5h. After leaching, the material was filtered and washed, yielding approximately 1200mL of water filtrate. The filter residue was dried and weighed to approximately 73g. The lithium leaching rate was found to be 95.8%, the iron leaching rate 11.2%, and the phosphorus leaching rate 9.5%. Take 1200 mL of the water leaching filtrate and add 150 g / L sodium hydroxide solution dropwise to pH 4.5 in an 80℃ constant temperature water bath. React for 2 h, and filter to obtain approximately 1150 mL of liquid after iron and aluminum removal. The Fe and Al contents are reduced to 6 ppm and 4 ppm, respectively. The liquid after iron and aluminum removal is subjected to deep purification with ion exchange resin (flow rate 2 BV / h), then concentrated to approximately 230 mL in a rotary evaporator. After cooling and crystallization, filter, wash, and dry to obtain 20.8 g of battery-grade lithium hydroxide with a purity of 99.0% and a total lithium recovery rate of 92.4%. Take 73 g of the water leaching residue and add 30 g / L sodium hydroxide solution at a liquid-to-solid ratio of 4:1. React at 80℃ for 1 h to remove aluminum. After washing, drying, and weighing, it is approximately 66 g, and the aluminum content is reduced to 0.15%. After aluminum removal, the filter residue was added to 330 mL of deionized water at a liquid-to-solid ratio of 5:1. Concentrated sulfuric acid was added dropwise at 70°C until the pH reached 1, and the reaction was allowed to proceed for 2.5 h. The residue was then filtered and washed to obtain an acid leaching solution, which was sent for analysis. The ferric phosphorus leaching rate was 99.0%. 48 mL of 30% hydrogen peroxide solution (excess) was added to the acid leaching solution, and oxidation was carried out at room temperature for 30 min. After oxidation, 30% sodium carbonate solution was added dropwise at 80°C until the pH reached 2.5, and the reaction was allowed to proceed for 2 h. After filtration, the solution was washed seven times with 80°C hot water and dried to obtain 59.6 g of regenerated ferric phosphorus. Product characterization: XRD showed an orthorhombic phase of FePO4•2H2O, Fe:P = 1:1.02, impurities <0.35%, and a specific surface area of ​​9.2 m² / g. The total recovery rate of ferric phosphorus was 95.1%.

[0024] Technical Results: This embodiment employs high-temperature calcination (550℃) and a moderate liquid-to-solid ratio (8:1), achieving a lithium leaching rate of 95.8% ± 0.6% and a total lithium recovery rate of 92.4%. The calcination time is shortened by 25% (2h → 1.5h), and water consumption is reduced by 20% (liquid-to-solid ratio 10:1 → 8:1). Overall energy and water consumption are reduced by approximately 18%, significantly improving economic efficiency. The phosphorus-iron leaching rate is 99.0% ± 0.4%, with a total recovery rate of 95.1%. The product has a Fe:P molar ratio of 1:1.02, impurities < 0.35%, and a specific surface area of ​​9.2 m² / g. This embodiment verifies that efficient recovery can still be achieved under high-temperature, short-time conditions, providing an energy-optimized solution for industrial applications.

[0025] Example 3 A method for recycling waste lithium iron phosphate battery powder includes the following steps: S1. Mix the waste lithium iron phosphate battery powder and additives at a mass ratio of 1:1.2 and grind them for 20 minutes. S2. Calcine the ground material at 400℃ for 2.5 hours; S3. The calcined material is soaked in water at a liquid-solid ratio of 5:1, the water soaking temperature is 80℃, the water soaking time is 1h, and after leaching, it is washed and filtered to obtain water leaching filtrate and water leaching residue. S4. Add a sodium hydroxide solution with a concentration of 100 g / L to the water leaching filtrate obtained in step S3, adjust the pH to 4.0, and perform iron and aluminum removal treatment to obtain the iron and aluminum removed liquid. S5. The liquid obtained in step S4 after removing iron and aluminum is subjected to deep impurity removal by ion exchange resin, then evaporated and crystallized, filtered and dried to obtain lithium hydroxide. S6. Wash the water-impregnated filter residue obtained in step S3 with sodium hydroxide solution to remove aluminum, and obtain the washed filter residue. S7. Use sulfuric acid to leach the washed filter residue obtained in step S6 to obtain an acid leaching solution. S8. Add hydrogen peroxide to the acid leaching solution to oxidize it, so that ferrous ions are converted into ferric ions. S9. Add sodium carbonate solution to the oxidized solution, adjust the pH to 2.0, filter, wash with hot water and dry to obtain the regenerated iron phosphate product.

[0026] In step S1, grinding is performed using a planetary ball mill.

[0027] In step S4, the temperature for iron and aluminum removal treatment is 60°C and the time is 2 hours.

[0028] In step S6, the concentration of the sodium hydroxide solution is less than 8%.

[0029] In step S7, the liquid-to-solid ratio of acid leaching is 4:1, the acid leaching temperature is 60℃, the acid leaching time is 3h, and the amount of sulfuric acid added is such that the pH reaches 1.

[0030] In step S9, the concentration of the sodium carbonate solution is 20%, the precipitation temperature is 60℃, and the precipitation time is 2 hours.

[0031] In step S9, the hot water washing is performed 5 times.

[0032] Example 4 A method for recycling waste lithium iron phosphate battery powder includes the following steps: S1. Mix the waste lithium iron phosphate battery powder and additives at a mass ratio of 1:1.2 and grind them for 30 minutes. S2. Calcine the ground material at 550℃ for 2.5 hours; S3. The calcined material is soaked in water at a liquid-solid ratio of 5:1, the water soaking temperature is 80℃, the water soaking time is 1h, and after leaching, it is washed and filtered to obtain water leaching filtrate and water leaching residue. S4. Add a sodium hydroxide solution with a concentration of 200 g / L to the water leaching filtrate obtained in step S3, adjust the pH to 5.0, and perform iron and aluminum removal treatment to obtain the iron and aluminum removed solution. S5. The liquid obtained in step S4 after removing iron and aluminum is subjected to deep impurity removal by ion exchange resin, then evaporated and crystallized, filtered and dried to obtain lithium hydroxide. S6. Wash the water-impregnated filter residue obtained in step S3 with sodium hydroxide solution to remove aluminum, and obtain the washed filter residue. S7. Use sulfuric acid to leach the washed filter residue obtained in step S6 to obtain an acid leaching solution. S8. Add hydrogen peroxide to the acid leaching solution to oxidize it, so that ferrous ions are converted into ferric ions. S9. Add sodium carbonate solution to the oxidized solution, adjust the pH to 3.0, filter, wash with hot water and dry to obtain the regenerated iron phosphate product.

[0033] In step S1, grinding is performed using a planetary ball mill.

[0034] In step S4, the temperature for iron and aluminum removal treatment is 80°C and the time is 3 hours.

[0035] In step S6, the concentration of the sodium hydroxide solution is less than 8%.

[0036] In step S7, the liquid-to-solid ratio of acid leaching is 4:1, the acid leaching temperature is 60℃, the acid leaching time is 3h, and the amount of sulfuric acid added is such that the pH reaches 1.

[0037] In step S9, the concentration of the sodium carbonate solution is 40%, the precipitation temperature is 60℃, and the precipitation time is 3 hours.

[0038] In step S9, the hot water washing is performed 8 times.

[0039] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for recycling waste lithium iron phosphate battery powder, characterized in that, Includes the following steps: S1. Mix the waste lithium iron phosphate battery powder and additives at a mass ratio of 1:1.2 and then grind them for 20-30 minutes. S2. Calcine the ground material at 400-550℃ for 1.5-2.5 hours; S3. The calcined material is soaked in water at a liquid-solid ratio of 5:1-10:1, the water soaking temperature is 60-80℃, the water soaking time is 1-2h, and after leaching, it is washed and filtered to obtain water-leached filtrate and water-leached filter residue. S4. Add sodium hydroxide solution to the water leaching filtrate obtained in step S3, adjust the pH to 4.0-5.0, and perform iron and aluminum removal treatment to obtain the iron and aluminum removed liquid. S5. The liquid obtained in step S4 after removing iron and aluminum is subjected to deep impurity removal by ion exchange resin, then evaporated and crystallized, filtered and dried to obtain lithium hydroxide. S6. Wash the water-impregnated filter residue obtained in step S3 with sodium hydroxide solution to remove aluminum, and obtain the washed filter residue. S7. Use sulfuric acid to leach the washed filter residue obtained in step S6 to obtain an acid leaching solution. S8. Add hydrogen peroxide to the acid leaching solution to oxidize it, so that ferrous ions are converted into ferric ions. S9. Add sodium carbonate solution to the oxidized solution, adjust the pH to 2.0-3.0, filter, wash with hot water and dry to obtain the regenerated iron phosphate product.

2. The method for recycling waste lithium iron phosphate battery powder according to claim 1, characterized in that, In step S1, grinding is performed using a planetary ball mill.

3. The method for recycling waste lithium iron phosphate battery powder according to claim 1, characterized in that, In step S4, the temperature for iron and aluminum removal treatment is 60-80℃, and the time is 2-3 hours.

4. The method for recycling waste lithium iron phosphate battery powder according to claim 1, characterized in that, In step S6, the concentration of the sodium hydroxide solution is less than 8%.

5. The method for recycling waste lithium iron phosphate battery powder according to claim 1, characterized in that, In step S7, the liquid-to-solid ratio of acid leaching is 4:1-5:1, the acid leaching temperature is 60-80℃, the acid leaching time is 2-3h, and the amount of sulfuric acid added is such that the pH reaches 1.

6. The method for recycling waste lithium iron phosphate battery powder according to claim 1, characterized in that, In step S9, the concentration of the sodium carbonate solution is 20-40%, the precipitation temperature is 60-80℃, the precipitation time is 2-3 hours, and the final pH is 2.

5.

7. The method for recycling waste lithium iron phosphate battery powder according to claim 1, characterized in that, In step S9, the hot water washing is performed 5-8 times.