A method for recovering lithium dihydrogen phosphate from a battery
The direct production of lithium dihydrogen phosphate from waste battery leachate using electrodialysis and nanofiltration technologies solves the problems of long process and high cost in existing technologies, achieving efficient and low-cost preparation of battery-grade lithium dihydrogen phosphate, simplifying the impurity removal process and improving product purity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG BRUNP RECYCLING TECH CO LTD
- Filing Date
- 2026-03-24
- Publication Date
- 2026-06-09
Smart Images
Figure CN122166734A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery recycling and resource utilization technology, and specifically relates to a method for preparing lithium dihydrogen phosphate from recycled batteries. Background Technology
[0002] With the explosive growth of the new energy vehicle industry, a large number of batteries are entering their retirement period, making their efficient and high-value recycling a focus of the industry. Hydrometallurgy is currently the mainstream recycling technology, which typically involves crushing, sorting, acid leaching, and purification to obtain a pure lithium solution, which is ultimately recovered as lithium carbonate or lithium hydroxide. However, existing recycling methods require additional synthesis steps to convert basic lithium salts into battery cathode material precursors (such as lithium dihydrogen phosphate), resulting in a long process, high cost, and high energy consumption.
[0003] In related technologies, the main method for directly preparing lithium dihydrogen phosphate from lithium sulfate is the metathesis precipitation method, for example, mixing lithium sulfate with sodium dihydrogen phosphate and crystallizing lithium dihydrogen phosphate based on the difference in solubility. However, this method requires extremely high purity of raw materials and easily introduces impurities such as sodium and sulfate, requiring multiple recrystallization purifications, resulting in low yields and unsuitability for complex battery recycling systems. Therefore, this invention is proposed. Summary of the Invention
[0004] This invention aims to at least solve one of the technical problems existing in related technologies. To this end, this invention proposes a method for preparing lithium dihydrogen phosphate from recycled batteries. This method can directly produce battery-grade lithium dihydrogen phosphate from the leachate of spent batteries, shortening the production process and significantly improving the economics of recycling.
[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for preparing lithium dihydrogen phosphate from recycled batteries includes the following steps: (1) The waste battery powder is acid-leached and purified to obtain a lithium-containing solution; (2) The lithium-containing solution and sodium dihydrogen phosphate solution are subjected to an electrodialysis metathesis reaction to obtain a lithium dihydrogen phosphate solution and a sodium-containing solution.
[0006] In some embodiments, in step (1), the waste battery powder is one of waste ternary battery powder and waste lithium iron phosphate battery powder.
[0007] In some embodiments, in step (1), the acid leaching includes: mixing waste battery powder with a first acid solution to produce a leaching reaction, and obtaining a leachate after solid-liquid separation; the temperature of the leaching reaction is 50-90℃, and the leaching reaction time is 1-4h.
[0008] In some embodiments, in step (1), the first acid solution is 98 wt% sulfuric acid, and the amount of sulfuric acid used is 1.02 to 1.2 times the molar lithium content in the battery powder.
[0009] In some embodiments, an oxidant is also added during the leaching reaction in step (1).
[0010] In some embodiments, the oxidant is hydrogen peroxide, and the amount of hydrogen peroxide used is 1.05-1.3 times the molar lithium content in the battery powder.
[0011] In some embodiments, in step (2), the purification includes: adding carbide slag to the leachate obtained by acid leaching to adjust the pH of the system to 10-12, reacting for 0.5-2 hours, and then separating the solid and liquid to obtain a first filtrate; adding soda ash to the first filtrate, reacting, and then separating the solid and liquid to obtain a second filtrate; adding a second acid solution to the second filtrate to adjust the pH to 6.0-7.5, and then adding activated carbon for adsorption and oil removal to obtain a lithium-containing solution.
[0012] In some embodiments, the lithium dihydrogen phosphate solution is subjected to nanofiltration to obtain a refined lithium dihydrogen phosphate solution, which is then evaporated, concentrated, cooled, crystallized, separated from its solid state, and dried to obtain battery-grade lithium dihydrogen phosphate.
[0013] In some embodiments, the amount of soda ash added is 1.02-1.2 times the calcium molar content in the first filtrate.
[0014] In some embodiments, the second acid is sulfuric acid.
[0015] In some embodiments, the amount of activated carbon added is 0.1%-0.5% of the solution mass, and the adsorption and oil removal time is 20-60 min.
[0016] In some embodiments, the electrodialysis metathesis reaction is carried out by passing the lithium-containing solution and the sodium dihydrogen phosphate solution separately into the feed chamber of the electrodialysis apparatus and under the action of a direct current electric field.
[0017] In some embodiments, the membrane stack sequence within the electrodialysis apparatus includes alternating anion exchange membranes and cation exchange membranes, with membrane partitions forming alternating feed chambers and product chambers.
[0018] In some embodiments, the membrane stack sequence in the electrodialysis apparatus includes alternating anion exchange membranes and cation exchange membranes, with membrane partitions forming alternating feed chambers and product chambers. Lithium sulfate solution and sodium dihydrogen phosphate solution flow into two adjacent feed chambers respectively, so that lithium dihydrogen phosphate solution is generated in the product chamber between the two adjacent feed chambers.
[0019] In some embodiments, the cation exchange membrane is a conventional cation exchange membrane or a selective cation exchange membrane, and the anion exchange membrane is a conventional anion exchange membrane or a selective anion exchange membrane.
[0020] In some embodiments, the voltage of the electrodialysis is 5-15V, and the current density is 10-100A / m. 2 .
[0021] In some embodiments, the sodium-containing solution is a sodium sulfate solution.
[0022] In some embodiments, the pressure of the nanofiltration process is 0.5-3.5 MPa.
[0023] In some embodiments, the evaporation and concentration temperature is 60-90°C.
[0024] In some embodiments, the cooling crystallization temperature is 5-25°C.
[0025] In some embodiments, the following steps are also included: evaporating and crystallizing the sodium-containing solution, and drying it to obtain sodium sulfate as a byproduct.
[0026] In some embodiments, the evaporation and crystallization temperature is 60-90°C.
[0027] The beneficial effects of this invention are: (1) High value and short process: This invention seamlessly connects wet recycling with material preparation, directly producing battery-grade lithium dihydrogen phosphate from waste battery leachate, shortening the industrial path from "waste" to "high-end raw material" (lithium dihydrogen phosphate), and significantly improving the economic efficiency of recycling.
[0028] (2) Simplified impurity removal process: Most of the impurities in the leachate are removed in one step by using carbide slag. The refined lithium sulfate solution can be obtained by using soda ash to remove calcium. The refined lithium sulfate solution can be further purified by electrodialysis and nanofiltration to obtain the target product solution. This solves the problem that different types of resins are still needed for fine purification after the traditional multi-step purification process.
[0029] (3) High-efficiency ion exchange and precise separation: An electrodialysis device is used as the core reactor, transforming the traditional liquid-phase metathesis reaction into a controllable ion-membrane exchange reaction driven by an electric field. The membrane stack in the electrodialysis device consists of alternating anion exchange membranes and cation exchange membranes, with membrane partitions forming alternating raw material and product chambers. Lithium sulfate solution and sodium dihydrogen phosphate solution flow into different raw material chambers respectively. Lithium ions in the lithium sulfate solution permeate through the cation exchange membrane, while sulfate ions permeate through the anion exchange membrane. Dihydrogen phosphate ions in the sodium dihydrogen phosphate solution permeate through the anion exchange membrane, while sodium ions permeate through the cation exchange membrane. This results in the generation of lithium dihydrogen phosphate solution and by-product sodium sulfate in different product chambers, achieving efficient and clean separation of the target product and impurity ions, avoiding the introduction of new impurities, and realizing the separation of Li + and SO4 2- The separation of sodium sulfate and the production of sodium sulfate byproducts improve the economic efficiency of the process.
[0030] (4) Multiple purification processes ensure product purity: After electrodialysis, a nanofiltration (NF) purification step is creatively added. The nanofiltration membrane can effectively retain polyvalent metal ions and organic macromolecules that may have passed through the previous steps or dissolved in trace amounts from the membrane, serving as the "ultimate barrier" to ensure that the final product meets the purity requirements of battery-grade products. This combined process (electrodialysis + nanofiltration) constitutes a dual membrane purification system, and the product purity is significantly better than that of a single method. The resulting lithium dihydrogen phosphate solution can be directly evaporated to obtain the product without recrystallization. Attached Figure Description
[0031] Figure 1 This is a flowchart illustrating Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the electrodialysis device in Embodiment 1 of the present invention; Figure 3 The image shows the XRD pattern of the lithium dihydrogen phosphate solid prepared in Example 1 of this invention. Detailed Implementation
[0032] The present invention will be further described below with reference to specific embodiments.
[0033] Example 1: A method for producing lithium dihydrogen phosphate from recycled batteries, such as Figure 1 As shown, it includes the following steps: (1) Take 500g of waste lithium iron phosphate battery black powder (Li content is about 3.11%) obtained by crushing and sorting, add 134.44g of 98% sulfuric acid solution and 152.36g of 30% hydrogen peroxide, stir and react at 80℃ for 2h, after the reaction is completed, filter under pressure to obtain about 1.42L of lithium sulfate leachate containing impurities; (2) Under stirring, the pH of the system was adjusted to 12.0 by slowly adding carbide slag to the leachate, and the reaction continued for 1 hour. A large amount of precipitate was generated in the solution. After filtration, the first filtrate was obtained. The concentration of calcium ions in the first filtrate was 0.7421 g / L. (3) Add 3.16g of soda ash to the first filtrate to remove calcium, and after the reaction, separate the solid and liquid to obtain the second filtrate; (4) Add dilute sulfuric acid to the second filtrate to adjust the pH of the filtrate to 7.0, add 5g of powdered activated carbon, stir and adsorb for 40min, and then filter to obtain about 1.42L of refined lithium sulfate solution; (5) Prepare a 1.0 mol / L sodium dihydrogen phosphate solution. Pump the purified lithium sulfate solution and sodium dihydrogen phosphate solution into an electrodialysis apparatus at a certain flow rate. The electrodialysis apparatus is as follows: Figure 2 As shown, the membrane stack sequence in the electrodialysis device includes alternating selective anion exchange membranes and selective cation exchange membranes. The membranes are divided into alternating feed chambers and product chambers. Lithium sulfate solution and sodium dihydrogen phosphate solution flow into different feed chambers respectively. Lithium ions in the lithium sulfate solution pass through the selective cation exchange membrane, and sulfate ions pass through the selective anion exchange membrane. Dihydrogen phosphate ions in the sodium dihydrogen phosphate solution pass through the selective anion exchange membrane, and sodium ions pass through the selective cation exchange membrane. This results in the generation of lithium dihydrogen phosphate solution and by-product sodium sulfate in different product chambers. The product chamber is initially filled with deionized water. The device operates at a DC voltage of 15V, an average current density of approximately 40A / m², and a temperature of 30℃. The flow rates of both feed and product are 3mL / min. (6) The obtained crude lithium dihydrogen phosphate solution (concentration approximately 1.5 mol / L) was pumped into a nanofiltration system (using a spiral wound nanofiltration membrane with a molecular weight cutoff of 200 Da, operating pressure 3.0 MPa) for purification. The permeate was collected to obtain a purified lithium dihydrogen phosphate solution. This solution was evaporated and concentrated at 85 °C until crystals precipitated. The solution was then transferred to a crystallization vessel and slowly cooled and crystallized at 15 °C for 8 h. After filtration, the crystals were washed with a small amount of saturated lithium dihydrogen phosphate solution and finally dried at 80 °C for 6 h to obtain white crystalline lithium dihydrogen phosphate solid. The XRD pattern of the obtained product is shown in the figure. Figure 3 As shown, by Figure 3 It can be seen that the product obtained by XRD is pure phase LiH2PO4; (7) Evaporate the sodium sulfate solution to obtain sodium sulfate byproduct.
[0034] Example 2: A method for preparing lithium dihydrogen phosphate from recycled batteries includes the following steps: (1) Take 500g of waste lithium iron phosphate battery black powder (Li content is about 3.11%) obtained by crushing and sorting, add 134.44g of 98% sulfuric acid solution and 152.36g of 30% hydrogen peroxide, stir and react at 80℃ for 2h, after the reaction is completed, filter under pressure to obtain about 1.42L of lithium sulfate leachate containing impurities; (2) Under stirring, the pH of the system was adjusted to 11.0 by slowly adding carbide slag to the leachate, and the reaction continued for 1 hour. A large amount of precipitate was generated in the solution. After filtration, the first filtrate was obtained. The concentration of calcium ions in the first filtrate was 0.6923 g / L. (3) Add 2.96g of soda ash to the first filtrate to remove calcium, and after the reaction, separate the solid and liquid to obtain the second filtrate; (4) Add dilute sulfuric acid to the second filtrate to adjust the pH of the filtrate to 7.0, add 5g of powdered activated carbon, stir and adsorb for 40min, and then filter to obtain about 1.42L of refined lithium sulfate solution; (5) Prepare a 1.0 mol / L sodium dihydrogen phosphate solution. Pump the refined lithium sulfate solution and sodium dihydrogen phosphate solution into an electrodialysis device at a certain flow rate. The electrodialysis device has a membrane stack sequence including alternating selective anion exchange membranes and selective cation exchange membranes. The membrane is divided into alternating raw material chambers and product chambers. The lithium sulfate solution and sodium dihydrogen phosphate solution flow into different raw material chambers. Lithium ions in the lithium sulfate solution pass through the selective cation exchange membrane, and sulfate ions pass through the selective anion exchange membrane. Dihydrogen phosphate ions in the sodium dihydrogen phosphate solution pass through the selective anion exchange membrane, and sodium ions pass through the selective cation exchange membrane, so that lithium dihydrogen phosphate solution and by-product sodium sulfate are generated in different product chambers. Deionized water is initially injected into the product chamber. The device is operated at a DC voltage of 15V, an average current density of about 40A / m², and a temperature of 30℃. The flow rates of raw material inflow and product outflow are both 3mL / min. (6) The crude lithium dihydrogen phosphate solution (concentration of about 1.5 mol / L) was pumped into a nanofiltration system (using a spiral wound nanofiltration membrane with a molecular weight cutoff of 200 Da and an operating pressure of 3.0 MPa) for purification. The permeate was collected to obtain a purified lithium dihydrogen phosphate solution. The solution was evaporated and concentrated at 85 °C until crystals precipitated. Then it was transferred to a crystallization vessel and slowly cooled and crystallized at 15 °C for 8 h. After filtration, the crystals were washed with a small amount of saturated lithium dihydrogen phosphate solution and finally dried at 80 °C for 6 h to obtain white crystalline lithium dihydrogen phosphate solid. The obtained product was identified as pure phase LiH2PO4 by XRD. (7) Evaporate the sodium sulfate solution to obtain sodium sulfate byproduct.
[0035] Example 3: A method for preparing lithium dihydrogen phosphate from recycled batteries includes the following steps: (1) Take 500g of waste lithium iron phosphate battery black powder (Li content is about 3.11%) obtained by crushing and sorting, add 134.44g of 98% sulfuric acid solution and 152.36g of 30% hydrogen peroxide, stir and react at 80℃ for 2h, after the reaction is completed, filter under pressure to obtain about 1.42L of lithium sulfate leachate containing impurities; (2) Under stirring, the pH of the system was adjusted to 12.0 by slowly adding carbide slag to the leachate, and the reaction continued for 1 hour. A large amount of precipitate was generated in the solution. After filtration, the first filtrate was obtained. The concentration of calcium ions in the first filtrate was 0.7421 g / L. (3) Add 3.16g of soda ash to the first filtrate to remove calcium, and after the reaction, separate the solid and liquid to obtain the second filtrate; (4) Add dilute sulfuric acid to the second filtrate to adjust the pH of the filtrate to 7.0, add 5g of powdered activated carbon, stir and adsorb for 40min, and then filter to obtain about 1.42L of refined lithium sulfate solution; (5) Prepare a 1.0 mol / L sodium dihydrogen phosphate solution. Pump the refined lithium sulfate solution and sodium dihydrogen phosphate solution into an electrodialysis device at a certain flow rate. The membrane stack in the electrodialysis device includes alternating selective anion exchange membranes and selective cation exchange membranes. The membranes are divided into alternating raw material chambers and product chambers. The lithium sulfate solution and sodium dihydrogen phosphate solution flow into different raw material chambers. Lithium ions in the lithium sulfate solution pass through the selective cation exchange membrane, and sulfate ions pass through the selective anion exchange membrane. Dihydrogen phosphate ions in the sodium dihydrogen phosphate solution pass through the selective anion exchange membrane, and sodium ions pass through the selective cation exchange membrane, so that lithium dihydrogen phosphate solution and by-product sodium sulfate are generated in different product chambers. Deionized water is initially injected into the product chamber. The device is operated at a DC voltage of 15V, an average current density of about 40A / m², and a temperature of 30℃. The flow rates of raw material inflow and product outflow are both 3mL / min. (6) The obtained crude lithium dihydrogen phosphate solution (concentration of about 1.5 mol / L) was pumped into a nanofiltration system (using a spiral wound nanofiltration membrane with a molecular weight cutoff of 200 Da and an operating pressure of 3.5 MPa) for purification. The permeate was collected to obtain a purified lithium dihydrogen phosphate solution. The solution was evaporated and concentrated at 85 °C until crystals precipitated. Then it was transferred to a crystallization vessel and slowly cooled and crystallized at 15 °C for 8 h. After filtration, the crystals were washed with a small amount of saturated lithium dihydrogen phosphate solution. Finally, it was dried at 80 °C for 6 h to obtain white crystalline lithium dihydrogen phosphate solid. The obtained product was identified as pure phase LiH2PO4 by XRD. (7) Evaporate the sodium sulfate solution to obtain sodium sulfate byproduct.
[0036] Comparative Example 1: A method for preparing lithium dihydrogen phosphate from recycled batteries includes the following steps: (1) Take 500g of waste lithium iron phosphate battery black powder (Li content is about 3.11%) obtained by crushing and sorting, add 134.44g of 98% sulfuric acid solution and 152.36g of 30% hydrogen peroxide, stir and react at 80℃ for 2h, after the reaction is completed, filter under pressure to obtain about 1.42L of lithium sulfate leachate containing impurities; (2) Under stirring, the pH of the system was adjusted to 12.0 by slowly adding carbide slag to the leachate and the reaction continued for 1 hour. A large amount of precipitate was generated in the solution. After filtration, the first filtrate and filter residue were obtained. The concentration of calcium ions in the first filtrate was 0.7421 g / L. (3) Add 3.16g of soda ash to the first filtrate to remove calcium, and after the reaction, separate the solid and liquid to obtain the second filtrate; (4) The second filtrate was treated with calcium and magnesium removal resin, and then the pH of the filtrate was adjusted back to 7.0 with dilute sulfuric acid. 5g of powdered activated carbon was added, and the mixture was stirred and adsorbed for 40 minutes before filtration to obtain about 1.42L of refined lithium sulfate solution. (5) Add soda ash to the refined lithium sulfate solution to precipitate lithium, filter and dry to obtain lithium carbonate powder, react the prepared lithium carbonate with phosphoric acid to obtain lithium dihydrogen phosphate solution, evaporate and concentrate at 85°C until crystallization occurs, then transfer to crystallization vessel, slowly cool and crystallize at 15°C for 8 hours, filter, wash the crystal with a small amount of saturated lithium dihydrogen phosphate solution, and finally dry at 80°C for 6 hours to obtain white crystalline lithium dihydrogen phosphate solid.
[0037] Experimental example: The products prepared in Examples 1-3 and Comparative Example 1 were subjected to ICP detection and analysis, and the detection results are shown in Table 1 below.
[0038] Table 1.
[0039] As shown in Table 1, the content of key impurity elements in the lithium dihydrogen phosphate products prepared in Examples 1-3 is lower than the requirements of the battery-grade material standard (YS / T 967-2014). The impurity content of the lithium dihydrogen phosphate product prepared in Comparative Example 1 does not meet the requirements of the battery-grade material standard, and further purification by recrystallization is required to obtain battery-grade products.
Claims
1. A method for preparing lithium dihydrogen phosphate from recycled batteries, characterized in that: Includes the following steps: (1) The waste battery powder is acid-leached and purified to obtain a lithium-containing solution; (2) The lithium-containing solution and sodium dihydrogen phosphate solution are subjected to an electrodialysis metathesis reaction to obtain a lithium dihydrogen phosphate solution and a sodium-containing solution.
2. The method for preparing lithium dihydrogen phosphate from recycled batteries according to claim 1, characterized in that: In step (1), the acid leaching includes: mixing waste battery powder with a first acid solution to produce a leaching reaction, and obtaining a leachate after solid-liquid separation; the temperature of the leaching reaction is 50-90℃, and the leaching reaction time is 1-4h.
3. A method for preparing lithium dihydrogen phosphate from recycled batteries according to claim 1 or 2, characterized in that: In step (2), the purification includes: adding carbide slag to the leachate obtained by acid leaching to adjust the pH of the system to 10-12, reacting for 0.5-2 hours, and then separating the solid and liquid to obtain the first filtrate; adding soda ash to the first filtrate, reacting, and then separating the solid and liquid to obtain the second filtrate; adding a second acid solution to the second filtrate to adjust the pH to 6.0-7.5, and then adding activated carbon for adsorption and oil removal to obtain a lithium-containing solution.
4. The method for preparing lithium dihydrogen phosphate from recycled batteries according to claim 1, characterized in that: The lithium dihydrogen phosphate solution is subjected to nanofiltration to obtain a refined lithium dihydrogen phosphate solution. This solution is then evaporated, concentrated, cooled, crystallized, separated from its solid state, and dried to obtain battery-grade lithium dihydrogen phosphate.
5. The method for preparing lithium dihydrogen phosphate from recycled batteries according to claim 3, characterized in that: The amount of soda ash added is 1.02-1.2 times the calcium molar content in the first filtrate.
6. The method for preparing lithium dihydrogen phosphate from recycled batteries according to claim 3, characterized in that: The second acid solution is sulfuric acid.
7. The method for preparing lithium dihydrogen phosphate from recycled batteries according to claim 3, characterized in that: The amount of activated carbon added is 0.1%-0.5% of the solution mass, and the adsorption and oil removal time is 20-60 minutes.
8. The method for preparing lithium dihydrogen phosphate from recycled batteries according to claim 1, characterized in that: The electrodialysis metathesis reaction is carried out by passing the lithium-containing solution and the sodium dihydrogen phosphate solution into the raw material chamber of the electrodialysis device, respectively, and under the action of a DC electric field.
9. The method for preparing lithium dihydrogen phosphate from recycled batteries according to claim 8, characterized in that: The voltage for electrodialysis is 5-15V, and the current density is 10-100A / m².
10. The method for preparing lithium dihydrogen phosphate from recycled batteries according to claim 4, characterized in that: The pressure of the nanofiltration process is 0.5-3.5 MPa.