Method for recycling lithium iron phosphate and re-preparing lithium iron phosphate positive electrode
By treating lithium iron phosphate waste slag through concentrated phosphoric acid and hydrogen peroxide, controlling the ratio of iron and phosphate, combining NaOH solution to adjust the pH value and heating and calcining, the problem of removing impurity metals in lithium iron phosphate waste slag is solved, and the recycling and reuse of high-purity lithium iron phosphate positive electrode material is achieved, and economic benefits and environmental protection are improved.
Patent Information
- Application Number
- CN202510511672.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-23
- Publication Date
- 2025-07-04
AI Technical Summary
In the prior art, lithium iron phosphate waste slag contains metal impurities such as Cu, Ni, Na, Mn, etc., which are difficult to effectively recycle and utilize, resulting in waste of resources and environmental pollution.
The lithium iron phosphate waste slag is treated with concentrated phosphoric acid and hydrogen peroxide. By controlling the ratio of iron and phosphate, combining NaOH solution to adjust the pH value and heating and calcining, a high-purity lithium iron phosphate positive electrode material is prepared to avoid the introduction of new impurities.
The leaching purity of lithium iron phosphate waste slag has been improved, and efficient recycling and reuse of lithium iron phosphate positive electrode material has been achieved, which has improved economic benefits and reduced environmental pollution.
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Figure CN120246969A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of lithium ion battery electrode material recovery, and specifically relates to a method for resource recovery of lithium iron phosphate and re-preparation of a lithium iron phosphate positive electrode. Background Art
[0002] Facing the crisis of global warming, the world has reached a consensus on low-carbon emission reduction. In the new energy industry, lithium batteries have an irreplaceable position as a new energy storage technology. Among them, olivine-structured lithium iron phosphate is widely used in power batteries due to its high thermal stability, long cycle life and low cost. The service life of lithium iron phosphate is only about five years; in the next few years, lithium batteries will usher in a "blowout" retirement.
[0003] After lithium is extracted from scrapped lithium iron phosphate batteries, lithium iron phosphate waste residue is obtained. Lithium iron phosphate waste residue is often treated as solid waste and is discarded at will or sent to landfill. However, a large number of waste lithium iron phosphate batteries contain rich lithium, iron and phosphorus elements, and the potential resource volume is huge. Recycling high economic value to prepare iron phosphate from iron phosphate waste residue and reuse it in the preparation of lithium iron phosphate batteries will have important significance for eliminating negative environmental impacts and alleviating the crisis of resource shortage. Summary of the invention
[0004] The object of the present invention is to provide a method for resource recovery of lithium iron phosphate and re-preparation of lithium iron phosphate positive electrode.
[0005] The purpose of the present invention can be achieved through the following technical solutions.
[0006] A method for recycling lithium iron phosphate and re-preparing a lithium iron phosphate positive electrode comprises the following steps:
[0007] S1. After the lithium iron phosphate waste residue is ground, a powder is obtained; the powder is placed in a muffle furnace and heated at 300-500° for 2 hours to obtain lithium iron phosphate powder with organic components removed.
[0008] S2. The solid powder obtained in step S1, phosphoric acid and deionized water are mixed and added into a beaker, reacted at room temperature for 6-8 hours, and then filtered to obtain a mixed solution.
[0009] Lithium iron phosphate has a high solubility in phosphoric acid solution and exists in the form of solution. However, in addition to Fe and P, lithium iron phosphate waste residue is also accompanied by impurity metals such as Na, Ni, Mn, Cu, and Al.
[0010] S3. Use ICP-OES instrument to detect the concentration of each metal ion in the mixed solution; according to the detected iron concentration in the acid leaching solution, add phosphoric acid to make the content ratio of iron and phosphate ion 1:1, then let it stand for 2-3 hours and filter to obtain a secondary acid leaching solution.
[0011] S4. Add hydrogen peroxide to the secondary acid leaching solution, adjust the reaction temperature to 70 - 80 °C for 2 - 3 h to obtain a mixed solution; filter the mixed solution to obtain a filter residue and a filtrate.
[0012] S5. Dropwise add NaOH solution to the filtrate obtained in S4, adjust the pH value of the solution to 1 - 3, then let it stand for 2 - 3 h and filter to obtain a hydrated iron phosphate precipitate and an alkali leaching solution.
[0013] S6. Dry the hydrated iron phosphate precipitate to a constant weight, then add a certain amount of lithium carbonate and a conductive agent, and calcine at 700 - 800 °C for 10 - 12 h in an inert atmosphere or a vacuum atmosphere.
[0014] Further, the concentration of the phosphoric acid solution is of high purity grade, and the dosage ratio of the lithium iron phosphate waste residue, the phosphoric acid solution and deionized water is 4 g : 2 mL : 10 - 20 mL.
[0015] Further, the concentration of the NaOH solution is 0.5 - 2 mol / L, the concentration of hydrogen peroxide is 2 - 5% wt, and the addition amount of hydrogen peroxide is 20 mL.
[0016] Further, the conductive agent is one or more of Carbon SP, glucose, sucrose, carbon nanotubes, graphene, and the addition amount is 1 - 15% of the mass of the iron phosphate waste residue.
[0017] Further, the inert atmosphere is nitrogen, helium, or argon.
[0018] The present invention has the following beneficial effects:
[0019] Both the O - P bond and the O - Fe bond in the lithium iron phosphate waste residue have strong bond energies and are not easily broken; however, using inorganic strong acids such as sulfuric acid, hydrochloric acid, and sulfuric acid will produce a large amount of polluting reducing gases and waste liquids; the present invention uses concentrated phosphoric acid to improve the leaching rate of various valuable metals in the lithium iron phosphate waste residue powder; in addition, hydrogen peroxide, as a strong oxidant, can oxidize all valuable metals to the highest valence, facilitating subsequent alkali leaching and extraction.
[0020] The present invention leaches the lithium iron phosphate waste residue with concentrated phosphoric acid, transferring impurity metals such as Na, Ni, Mn, Cu, and Al in the lithium iron phosphate waste residue into the acid leaching solution; the acid leaching solution adjusts the ratio of iron and phosphate radicals, then drops NaOH solution to adjust the pH value of the acid leaching solution, adds hydrogen peroxide to oxidize ferrous ions, and thus obtains anhydrous iron phosphate without crystal water after filtration and heating. Avoiding waste of valuable metal resources. Description of the Drawings
[0021] Figure 1 is the XRD pattern of the hydrated iron phosphate prepared in Example 1 of the present invention.
[0022] Figure 2 XRD pattern of the lithium iron phosphate prepared in Example 1 of the present invention.
[0023] Figure 3 Charge-discharge capacity curve of the lithium iron phosphate prepared in Example 7 of the present invention at 0.1C.
[0024] Figure 4 Charge-discharge capacity curve of the lithium iron phosphate prepared in Example 7 of the present invention at 0.1C.
[0025] Figure 5 Scanning electron microscope (SEM) image of the lithium iron phosphate prepared in Example 1 of the present invention. Detailed implementation manners
[0026] To make the technical solutions of the present invention clearer, the following further describes the present invention in detail with reference to the accompanying drawings and specific embodiments.
[0027] Example 1:
[0028] 1. After grinding the lithium iron phosphate waste residue, powder was obtained; the powder was placed in a muffle furnace and heated at 300°C for 2 h to obtain lithium iron phosphate powder with organic components removed.
[0029] 2. Weigh 4 g of the lithium iron phosphate powder with organic components removed and add it to a beaker, then add 2 mL of concentrated phosphoric acid and 10 mL of deionized water, react at room temperature for 6 h, and then filter to obtain a mixed solution.
[0030] 3. Use an ICP-OES instrument to detect the concentrations of various metal ions in the mixed solution:
[0031]
[0032] Then, according to the iron content in the acid leaching solution, add concentrated phosphoric acid to make the content ratio of Fe to phosphate radical 1:1, then let it stand for 2 h and filter to obtain a secondary acid leaching solution.
[0033] 4. Add 20 mL of 2 wt% hydrogen peroxide to the secondary acid leaching solution, then place the beaker in an oil bath and react at 70°C for 2 h, and then filter the solution to obtain a filter residue and a filtrate.
[0034] 5. Drop 0.5 mol / L NaOH solution into the filtrate to adjust the pH value of the acid leaching solution to 1.0, let it stand for 2 h, and then filter to obtain a solid and a filtrate respectively. The solid was washed three times with deionized water and then dried at 80°C for 30 min to obtain a hydrated iron phosphate precipitate
[0035] 6. Add the precipitated hydrated iron phosphate, 1.1 g of lithium carbonate, and 0.8 g of sucrose to a mortar. After mixing and stirring evenly, transfer them into a tubular furnace. Heat to 700 °C in an argon atmosphere and continue calcining for 10 hours to obtain lithium iron phosphate at the battery grade.
[0036] Example 2
[0037] 1. Grind the lithium iron phosphate waste residue to obtain powder; place the powder in a muffle furnace and heat at 300 °C for 2 h to obtain lithium iron phosphate powder with organic components removed.
[0038] 2. Weigh 4 g of the lithium iron phosphate powder with organic components removed and add it to a beaker. Then add 2 mL of concentrated phosphoric acid and 10 mL of deionized water. React at room temperature for 6 h, and then filter to obtain a mixed solution.
[0039] 3. Use an ICP-OES instrument to detect the concentrations of various metal ions in the acid leaching solution:
[0040]
[0041] Then, according to the iron content in the acid leaching solution, add phosphate radicals so that the content ratio of Fe to phosphate radicals is 1:1. Then let it stand for 2 h and filter to obtain a secondary acid leaching solution.
[0042] 4. Add 20 mL of 2 wt% hydrogen peroxide to the secondary acid leaching solution. Then place the beaker in an oil bath and react at 70 °C for 2 h. Then filter the solution to obtain a filter residue and a filtrate.
[0043] 5. Drop 0.5 mol / L NaOH solution into the filtrate to adjust the pH value of the acid leaching solution to 1.6. Let it stand for 2.5 h, and then filter to obtain a solid and a filtrate respectively. Wash the solid three times with deionized water and then dry it at 80 °C for 30 min to obtain the precipitated hydrated iron phosphate
[0044] 6. Add the precipitated hydrated iron phosphate, 1.1 g of lithium carbonate, and 0.8 g of sucrose to a mortar. After mixing and stirring evenly, transfer them into a tubular furnace. Heat to 700 °C in an argon atmosphere and continue calcining for 10 hours to obtain lithium iron phosphate at the battery grade.
[0045] Example 3
[0046] 1. Grind the lithium iron phosphate waste residue to obtain powder; place the powder in a muffle furnace and heat at 300 °C for 2 h to obtain lithium iron phosphate powder with organic components removed.
[0047] 2. Weigh 4 g of the lithium iron phosphate powder with organic components removed and add it to a beaker. Then add 2 mL of concentrated phosphoric acid and 15 mL of deionized water. React at room temperature for 7 h, and then filter to obtain a mixed solution.
[0048] 3. Detect the concentrations of various metal ions in the acid leaching solution using an ICP-OES instrument:
[0049]
[0050] After that, according to the iron content in the acid leaching solution, phosphate is added to make the content ratio of Fe to phosphate 1:1. Then, it is left standing for 2 h and filtered to obtain the secondary acid leaching solution.
[0051] 4. Add 20 mL of 2 wt% hydrogen peroxide to the secondary acid leaching solution. Then, place the beaker in an oil bath and react at 70 °C for 2 h. After that, filter the solution to obtain the filter residue and the filtrate.
[0052] 5. Drop 0.5 mol / L NaOH solution into the filtrate to adjust the pH value of the acid leaching solution to 1.0. Let it stand for 3 h and then filter to obtain the solid and the filtrate respectively. The solid is washed three times with deionized water and then dried at 80 °C for 30 min to obtain the hydrated iron phosphate precipitate.
[0053] 6. Add the hydrated iron phosphate precipitate, 1.1 g of lithium carbonate, and 0.8 g of sucrose to a mortar. After mixing and stirring evenly, load them into a tube furnace and heat to 700 °C in an argon atmosphere and continue to calcine for 10 hours to obtain lithium iron phosphate at the battery grade.
[0054] Example 4
[0055] 1. Grind the lithium iron phosphate waste residue to obtain powder; place the powder in a muffle furnace and heat at 450 °C for 2 h to obtain lithium iron phosphate powder with organic components removed.
[0056] 2. Weigh 4 g of lithium iron phosphate powder with organic components removed and add it to a beaker. Then, add 2 mL of concentrated phosphoric acid and 10 mL of deionized water, react at room temperature for 7 h, and then filter to obtain the mixed solution.
[0057] 3. Detect the concentrations of various metal ions in the acid leaching solution using an ICP-OES instrument:
[0058]
[0059]
[0060] After that, according to the iron content in the acid leaching solution, phosphate is added to make the content ratio of Fe to phosphate 1:1. Then, it is left standing for 2 h and filtered to obtain the secondary acid leaching solution.
[0061] 4. Add 20 mL of 2 wt% hydrogen peroxide to the secondary acid leaching solution. Then, place the beaker in an oil bath and react at 70 °C for 2 h. After that, filter the solution to obtain the filter residue and the filtrate.
[0062] 5. Add 0.5 mol / L NaOH solution dropwise to the filtrate to adjust the pH value of the acid leaching solution to 1.0. Let it stand for 3 h, then filter to obtain a solid and a filtrate respectively. The solid is washed three times with deionized water and then dried at 70 °C for 30 min to obtain the hydrated iron phosphate precipitate.
[0063] 6. Add the hydrated iron phosphate precipitate, 1.1 g of lithium carbonate and 0.8 g of sucrose to a mortar. After mixing and stirring evenly, transfer them into a tube furnace. Heat to 800 °C in an argon atmosphere and continue to calcine for 10 hours to obtain the lithium iron phosphate at the battery grade.
[0064] Example 5
[0065] 1. Grind the lithium iron phosphate waste residue to obtain a powder; place the powder in a muffle furnace and heat at 300 °C for 2 h to obtain the lithium iron phosphate powder with organic components removed.
[0066] 2. Weigh 4 g of the lithium iron phosphate powder with organic components removed and add it to a beaker. Then add 2 mL of concentrated phosphoric acid and 10 mL of deionized water. React at room temperature for 8 h, then filter to obtain a mixed solution.
[0067] 3. Use an ICP-OES instrument to detect the concentrations of various metal ions in the acid leaching solution:
[0068]
[0069] Then, according to the iron content in the acid leaching solution, add phosphate so that the content ratio of Fe to phosphate is 1:1. Then let it stand for 3 h and filter to obtain the secondary acid leaching solution.
[0070] 4. Add 20 mL of 2 wt% hydrogen peroxide to the secondary acid leaching solution. Then place the beaker in an oil bath and react at 80 °C for 3 h. Then filter the solution to obtain a filter residue and a filtrate.
[0071] 5. Add 0.5 mol / L NaOH solution dropwise to the filtrate to adjust the pH value of the acid leaching solution to 1.0. Let it stand for 3 h, then filter to obtain a solid and a filtrate respectively. The solid is washed three times with deionized water and then dried at 80 °C for 30 min to obtain the hydrated iron phosphate precipitate.
[0072] 6. Add the hydrated iron phosphate precipitate, 1.1 g of lithium carbonate and 0.8 g of sucrose to a mortar. After mixing and stirring evenly, transfer them into a tube furnace. Heat to 700 °C in an argon atmosphere and continue to calcine for 12 hours to obtain the lithium iron phosphate at the battery grade.
[0073] Example 6
[0074] 1. Grind the lithium iron phosphate waste residue to obtain a powder; place the powder in a muffle furnace and heat at 300 °C for 2 h to obtain the lithium iron phosphate powder with organic components removed.
[0075] 2. Weigh 4 g of lithium iron phosphate powder after removing organic components and add it to a beaker. Then add 2 mL of concentrated phosphoric acid and 10 mL of deionized water, react at room temperature for 8 h, and then filter to obtain a mixed solution.
[0076] 3. Use an ICP-OES instrument to detect the concentrations of various metal ions in the acid-leaching solution:
[0077]
[0078] Then, according to the iron content in the acid-leaching solution, add phosphate so that the content ratio of Fe to phosphate is 1:1. Then let it stand for 2 h and filter to obtain a secondary acid-leaching solution.
[0079] 4. Add 20 mL of 2 wt% hydrogen peroxide to the secondary acid-leaching solution. Then place the beaker in an oil bath and react at 70 °C for 2 h. Then filter the solution to obtain a filter residue and a filtrate.
[0080] 5. Drop 1.5 mol / L NaOH solution into the filtrate to adjust the pH value of the acid-leaching solution to 1.6. Let it stand for 3 h and then filter to obtain a solid and a filtrate respectively. The solid is washed three times with deionized water and then dried at 80 °C for 30 min to obtain a hydrated iron phosphate precipitate.
[0081] 6. Add the hydrated iron phosphate precipitate, 1.1 g of lithium carbonate, and 0.8 g of sucrose to a mortar. After mixing and stirring evenly, load it into a tube furnace and heat it to 700 °C in an argon atmosphere and continue to calcine for 10 hours to obtain battery-grade lithium iron phosphate.
[0082] Example 7
[0083] 1. Grind the lithium iron phosphate waste residue to obtain a powder; place the powder in a muffle furnace and heat it at 300 °C for 2 h to obtain lithium iron phosphate powder after removing organic components.
[0084] 2. Weigh 4 g of lithium iron phosphate powder after removing organic components and add it to a beaker. Then add 2 mL of concentrated phosphoric acid and 20 mL of deionized water, react at room temperature for 8 h, and then filter to obtain a mixed solution.
[0085] 3. Use an ICP-OES instrument to detect the concentrations of various metal ions in the acid-leaching solution:
[0086]
[0087] Then, according to the iron content in the acid-leaching solution, add phosphate so that the content ratio of Fe to phosphate is 1:1. Then let it stand for 2 h and filter to obtain a secondary acid-leaching solution.
[0088] 4. Add 20 mL of 5 wt% hydrogen peroxide to the secondary acid-leaching solution. Then place the beaker in an oil bath and react at 80 °C for 2 h. Then filter the solution to obtain a filter residue and a filtrate.
[0089] 5. Add 2 mol / L NaOH solution dropwise to the filtrate to adjust the pH value of the acid-leached solution to 3.0, let it stand for 2 h, and then filter to obtain a solid and a filtrate respectively. The solid is washed three times with deionized water and then dried at 80 °C for 30 min to obtain a hydrated iron phosphate precipitate.
[0090] 6. Add the hydrated iron phosphate precipitate, 1.1 g of lithium carbonate, and 0.8 g of sucrose to a mortar. After mixing and stirring evenly, load them into a tube furnace and heat to 800 °C in an argon atmosphere and then continue to calcine for 10 hours to obtain lithium iron phosphate at the battery grade.
[0091] Performance test:
[0092] The electrochemical performance of the re-synthesized lithium iron phosphate cathode material was studied using CR2025 coin cells. The working electrode was prepared by mixing lithium iron phosphate prepared in Examples 1-3 and Comparative Examples 1-2 as the cathode material with polyvinylidene fluoride (PVDF) and conductive carbon black (Super P) in a mass ratio of 80:10:10 in NMP, coating it on an aluminum foil, drying it in a vacuum drying oven at 80 °C for 12 h, and then cutting it into a circular electrode sheet with a diameter of 10 mm. The loading capacity of the active material was about 2 mg·cm -2 . The battery was assembled in a glove box filled with argon (H2 O , O2 < 1 ppm). On a NEWARE BTS battery tester (Neware BTS-XWJ-6.44S-00057), the cyclic performance of the lithium iron phosphate cathode material was tested using the constant current charge-discharge method at room temperature. The initial discharge specific capacity of the battery was detected
[0093] The specific test results are shown in the following table:
[0094] Table 1
[0095]
[0096] Data analysis:
[0097] By comparing and analyzing the data in the above table, the batteries prepared from the battery-grade iron phosphate obtained in Examples 1-7 of the present invention all have good electrochemical performance. Specifically, the initial discharge specific capacity of the batteries prepared in each example exceeds 145 mAhg- 1 .
Claims
1. A method for resourcefully recycling and preparing a lithium iron phosphate battery using the positive electrode of a lithium iron phosphate battery, characterized in that, It includes the following steps: S1. After grinding the lithium iron phosphate waste residue, powder is obtained; the powder is placed in a muffle furnace and heated at 300 - 500 °C for 2 h to obtain lithium iron phosphate powder with organic components removed. S2. The solid powder obtained in step S1, phosphoric acid and deionized water are mixed and added to a beaker, and reacted at room temperature for 6 - 8 h, and then filtered to obtain a mixed solution. S3. An ICP - OES instrument is used to detect the concentrations of various metal ions in the mixed solution; according to the iron concentration in the detected acid leaching solution, phosphoric acid is added to make the content ratio of iron to phosphate radical 1:1, and then it is left standing for 2 - 3 h and filtered to obtain a secondary acid leaching solution. S4. Hydrogen peroxide is added to the secondary acid leaching solution, and the reaction is carried out at 70 - 80 °C for 2 - 3 h to obtain a mixed solution; the mixed solution is filtered to obtain a filter residue and a filtrate. S5. NaOH solution is added dropwise to the filtrate obtained in S4 to adjust the pH value of the solution to 1 - 3, and then it is left standing for 2 - 3 h and filtered to obtain hydrated iron phosphate precipitate and an alkali leaching solution. S6. The hydrated iron phosphate precipitate is dried to a constant weight, and then a certain amount of lithium carbonate and a conductive agent are added, and calcined at 700 - 800 °C for 10 - 12 h in an inert atmosphere or a vacuum atmosphere.
2. A method for resource recovery of lithium iron phosphate and re-preparation of lithium iron phosphate cathode according to claim 1, characterized in that, In step S2, the concentration of the phosphoric acid solution is of super pure grade, and the dosage ratio of the lithium iron phosphate waste residue, the phosphoric acid solution and deionized water is 4 g:2 mL:10 - 20 mL.
3. The method for resource recovery of iron phosphate waste residue to prepare lithium iron phosphate battery according to claim 1, characterized in that, In step S4, the concentration of the hydrogen peroxide is 2 - 5% wt, and the addition amount of the hydrogen peroxide is 20 mL.
4. The method for resourcefully recycling phosphoric iron waste residue to prepare a lithium iron phosphate battery according to claim 1, characterized in that, In step S5, the concentration of the NaOH solution is 0.5 - 2 mol / L.
5. The method for resourcefully recycling phosphoric iron waste residue to prepare a lithium iron phosphate battery according to claim 1, characterized in that, In step S6, the conductive agent is one or several of Carbon SP, glucose, sucrose, carbon nanotubes, graphene, and the addition amount is 1 - 15% of the mass of the lithium iron phosphate waste residue.
6. A method for resource recovery of iron phosphate waste residue to prepare lithium iron phosphate battery according to claim 1, characterized in that In step S6, the inert atmosphere is nitrogen, helium, neon or argon.