Resource utilization method for positive electrode material of waste lithium iron phosphate battery

Abstract

The invention belongs to the technical field of waste battery resource utilization, and particularly relates to a waste lithium iron phosphate battery positive electrode material resource utilization method, which comprises: crushing and screening a waste lithium iron phosphate battery positive electrode material, uniformly mixing with pyrite, placing in a tubular furnace, and heating and calcining in an air environment to obtain a solid A; pulping the solid A and water for reaction, and filtering after reaction to obtain filtrate B and solid B; drying and grinding the solid B, taking out the solid B, adding a copper sulfate solution, performing ultrasonic treatment to obtain a solution C, adding a NaOH solution into the solution C, adjusting the pH value of the solution, performing ultrasonic treatment, performing hydrothermal reaction on the solution C after ultrasonic treatment, and centrifuging and drying the solution C after hydrothermal treatment to obtain a solid C; the solid C obtained by the method is used as a catalyst for degrading antibiotics in a water body, and the filtrate B is separated and purified to prepare battery-grade lithium carbonate which is a raw material required for preparing a lithium battery, so that resource utilization of all elements of the positive electrode material of the waste lithium iron phosphate battery is realized.

Description

Technical Field

[0001] The invention relates to the technical field of resource utilization of waste batteries, and in particular to a method for resource utilization of positive electrode materials of waste lithium iron phosphate batteries. Background Art

[0002] Lithium iron phosphate has an olivine structure and good safety performance. The cost of making lithium iron phosphate batteries with it is low. It has been put into use in large quantities and occupies a huge market share in the battery industry. The service life of lithium iron phosphate batteries is 8-10 years. In the near future, a large number of lithium iron phosphate batteries will be scrapped, forming a "retirement wave". If these "retired" waste lithium iron phosphate batteries cannot be effectively recycled, it will not only pollute the environment, but also cause a large amount of valuable metal resources to be lost.

[0003] At present, the recycling methods for waste lithium iron phosphate battery positive electrode materials include traditional element recovery methods, including pyrometallurgy and hydrometallurgy. During the metallurgical process, a large amount of polluted gases, polluted wastewater and other substances that are not conducive to environmental protection will be generated, aggravating global environmental problems. In addition, there will be lithium loss during the metallurgical process, resulting in waste of resources. There are also emerging recycling methods in recent years, including direct repair and regeneration and selective lithium extraction. Direct repair and regeneration cannot be used industrially at present. This method can only repair a small part of lithium iron phosphate with low impurities and high concentration. Although selective lithium extraction uses less leaching agent and has a high lithium recovery rate, the cost is also high, and only lithium resources are recycled. The recycling of remaining substances remains to be explored. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the main purpose of the present invention is to propose a method for resource utilization of waste lithium iron phosphate battery positive electrode materials.

[0005] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions: A method for resource utilization of waste lithium iron phosphate battery positive electrode materials, comprising the following steps: S1, the waste lithium iron phosphate battery positive electrode material is crushed and sieved, and then mixed with pyrite, and heated and calcined in an air environment to obtain solid A; S2, solid A is slurried with water for reaction, and after the reaction, filtrate is filtered to obtain filtrate B and solid B; S3, solid B is dried and ground, taken out, and copper sulfate solution is added to obtain solution C by ultrasonication, and then NaOH solution is added to solution C to adjust the pH of solution C and then ultrasonication is performed, and solution C after ultrasonication is subjected to hydrothermal reaction, and solution C after hydrothermal reaction is centrifuged and dried to obtain solid C; S4. Solid C is added into a solution containing antibiotics, and the antibiotics are degraded through dark adsorption and light reaction. The filtrate B is enriched and impurities are removed, and then precipitated and separated to extract lithium.

[0006] As a preferred embodiment of the method for resource utilization of waste lithium iron phosphate battery positive electrode materials described in the present invention, wherein: in the step S1, the particle size of the waste lithium iron phosphate battery positive electrode material powder after crushing and sieving is ≤50 mesh; the molar ratio of iron in the waste lithium iron phosphate battery positive electrode material after crushing and sieving to iron in pyrite is 1:(1.8-2.6).

[0007] As a preferred embodiment of the method for resource utilization of waste lithium iron phosphate battery positive electrode materials described in the present invention, wherein: in the step S1, heating and calcination are carried out in a tubular furnace, the reaction temperature is 200-600°C, the reaction time is 1.5-5.0h, and the air flow rate is 1-2L / min.

[0008] As a preferred embodiment of the method for resource utilization of waste lithium iron phosphate battery positive electrode materials described in the present invention, wherein: in the step S2, the reaction time is 0.5-2.5h, and the reaction temperature is 25-90°C.

[0009] As a preferred embodiment of the method for resource utilization of waste lithium iron phosphate battery positive electrode materials described in the present invention, wherein: in the step S2, the filtrate B is a lithium-containing solution, the lithium element leaching rate is ≥98%, and the lithium element is extracted by precipitation separation after enrichment, and the lithium can be used as a raw material for lithium-ion batteries, catalysts, ceramics, and glass to achieve resource utilization.

[0010] As a preferred embodiment of the method for resource utilization of waste lithium iron phosphate battery positive electrode materials described in the present invention, wherein: in the step S3, the solid-liquid ratio of solid B to copper sulfate solution is (1-5) g / 50 mL; the concentration of copper sulfate solution is 0.008-0.020 mol / L.

[0011] As a preferred embodiment of the method for resource utilization of waste lithium iron phosphate battery positive electrode materials described in the present invention, wherein: in the step S3, the concentration of the NaOH solution is 0.01-1.00 mol / L, the pH is 7.00-8.00, the hydrothermal reaction time is 2-5h, and the hydrothermal reaction temperature is 100-150°C.

[0012] As a preferred embodiment of the method for resource utilization of waste lithium iron phosphate battery positive electrode materials described in the present invention, wherein: in the step S4, the antibiotics are a series of electron-rich antibiotics.

[0013] As a preferred embodiment of the method for resource utilization of waste lithium iron phosphate battery positive electrode materials described in the present invention, wherein: in the step S4, the degradation rate of the antibiotic is ≥50%.

[0014] The beneficial effects of the present invention are as follows: The invention provides a method for resource utilization of waste lithium iron phosphate battery positive electrode materials. The waste lithium iron phosphate battery positive electrode materials are crushed and screened, mixed evenly with pyrite, and then put into a tubular furnace, and heated and calcined in an air environment to obtain solid A; solid A is slurried with water for reaction, and filtered after reaction to obtain filtrate B and solid B; solid B is dried and ground, taken out, and added with copper sulfate solution for ultrasonication to obtain solution C, and then NaOH solution is added to solution C to adjust the pH value of the solution, and then ultrasonication is performed, the ultrasonicated solution C is hydrothermally reacted, the hydrothermal solution C is centrifuged, and the solid C is dried to obtain solid C; the solid C obtained by the method is used as a catalyst for degrading antibiotics in water bodies, and the filtrate B is separated and purified to obtain battery-grade lithium carbonate required as a raw material for preparing lithium batteries, thereby realizing resource utilization of all elements of waste lithium iron phosphate battery positive electrode materials. DETAILED DESCRIPTION

[0015] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] According to one aspect of the present invention, the present invention provides the following technical solution: A method for resource utilization of waste lithium iron phosphate battery positive electrode materials, comprising the following steps: S1, the waste lithium iron phosphate battery positive electrode material is crushed and sieved, mixed with the crushed pyrite and put into a tubular furnace, and heated and calcined in an air environment to obtain solid A; heating and calcining in air, the main substance FeS2 in pyrite reacts with oxygen in the air at high temperature to generate iron oxide and sulfur dioxide. In this process, Fe (II) and S in FeS2 - As well as Fe (II) in lithium iron phosphate, they are all used as reducing agents. The sulfur element in pyrite combines with oxygen to form sulfur trioxide, which is beneficial to the leaching of lithium ions in the second step. In addition, the iron in pyrite can also be used as a raw material for iron-based catalysts, which helps to achieve the recycling of resources. The chemical reaction equation that may occur during this period is as follows: 6LiFePO4+ 1.5O2= 2Li3Fe2(PO4)3+ Fe2O3 (1) 2LiFePO4+ 2FeS2+8O2= Li2O + Fe2O3+ 2FePO4+ 4SO3 (2) 4FeS2+ 11O2= 2Fe2O3+ 8SO2 (3) 2SO2+O2= 2SO3 (4) S2, solid A is slurried with water for reaction, and after the reaction, filtrate is filtered to obtain filtrate B and solid B; S3, after drying and grinding solid B, take it out and add copper sulfate solution to ultrasonic for 0.5h to obtain solution C (ultrasound helps solution reaction), add NaOH solution to solution C to adjust the pH of solution C to neutral or alkaline, and then ultrasonic for 1h (alkaline environment is conducive to the reaction and precipitation of iron ions and copper ions), subject the ultrasonic solution C to hydrothermal reaction, centrifuge the hydrothermal solution C three times (hydrothermal reaction can accelerate the reaction rate, improve the purity and crystallinity of the reactants, and centrifugal separation is conducive to impurity removal), and dry to obtain solid C; S4. Solid C is added to solutions containing antibiotics of different concentrations for dark adsorption and light reaction to achieve degradation of the antibiotics. The filtrate B is enriched and impurities are removed, and then precipitated and separated to extract lithium.

[0017] Preferably, in the step S1, the particle size of the crushed and sieved waste lithium iron phosphate battery positive electrode material powder is ≤50 mesh; the molar ratio of iron in the crushed and sieved waste lithium iron phosphate battery positive electrode material powder to iron in pyrite is 1:(1.8-2.6); heating and calcining reaction is carried out in a tubular furnace, the heating and calcining reaction temperature is 200-600°C, the reaction time is 1.5-5.0h, and the air flow rate is 1-2L / min.

[0018] Preferably, in step S2, the reaction time is 0.5-2.0h, the reaction temperature is 20-90°C; the solid B is iron phosphate; the filtrate B is a lithium-containing solution, and the lithium leaching rate is ≥98%. After enrichment, the lithium element is extracted by precipitation separation, and the lithium can be used as a raw material for lithium-ion batteries, catalysts, ceramics, and glass to achieve resource utilization.

[0019] Preferably, in step S3, the solid-liquid ratio of solid B to copper sulfate solution is (1-5) g / 50 mL; the concentration of copper sulfate solution is 0.008-0.020 mol / L, the concentration of NaOH solution is 0.01-1.00 mol / L, the pH is 7.00-8.00, the hydrothermal reaction time is 2-5 hours, and the hydrothermal reaction temperature is 100-150° C.

[0020] Preferably, in step S3, the solid C is copper ferrite, which is used as a catalyst for degrading antibiotics in water to achieve resource utilization.

[0021] Preferably, in step S4, the amount of solid C added to the solution containing the antibiotic can be adjusted according to the concentration of the antibiotic, and the higher the concentration, the more solid C is added. The antibiotic is a series of electron-rich antibiotics, and the degradation rate of the antibiotic is ≥50%. More preferably, the degradation rate of the antibiotic is 50-92%.

[0022] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0023] The iron content in the waste lithium iron phosphate positive electrode material powder used in each embodiment and comparative example is 27wt%, and the iron content in the pyrite is 35wt%.

[0024] Example 1 A method for resource utilization of waste lithium iron phosphate battery positive electrode materials, comprising the following steps: S1. Put 2 g of waste lithium iron phosphate positive electrode material powder with a particle size of ≤50 mesh and 4 g of crushed pyrite powder (the molar ratio of iron in lithium iron phosphate to iron in pyrite is 1:1.9) into a porcelain boat and place it in the middle of a tube furnace. Let air flow in at a flow rate of 1 L / min. Heat and calcine at 400° C. for 3 h to obtain 5.78 g of calcined lithium iron phosphate. S2, the calcined lithium iron phosphate was slurried with 50 mL of water for a reaction time of 0.5 h at a temperature of 60 ° C. After the reaction, a lithium-containing solution, iron phosphate, iron oxide and carbon were obtained by filtration. The Li content in the solution was detected by ICP. The lithium leaching rate was calculated to be 99%; S3, weighing 0.8 g of the iron phosphate in step S2, adding 40 mL of 0.012 mol / L copper sulfate solution and ultrasonicating for half an hour to obtain a solution containing an iron-copper complex, adding 0.1 mol / L NaOH to the solution of the iron-copper complex to adjust the pH of the solution to 7.50, and then ultrasonicating for one hour, subjecting the ultrasonic solution to a hydrothermal reaction, centrifuging the hydrothermal solution three times, and drying to obtain a mixed solid of the iron-copper complex and carbon; S4, weighing 200 mg of the iron-copper complex and carbon mixed solid of step S3, adding it to 100 mL of a 25 mg / L tetracycline hydrochloride aqueous solution, adsorbing it in the dark for 0.5 h, irradiating it with simulated sunlight to degrade the antibiotic, testing the absorbance of the reaction solution, and calculating that the degradation rate of tetracycline hydrochloride reached 90.23%; Example 2 A method for resource utilization of waste lithium iron phosphate battery positive electrode materials, comprising the following steps: S1. Put 2 g of waste lithium iron phosphate positive electrode material powder with a particle size of ≤50 mesh and 5 g of crushed pyrite powder (the molar ratio of iron in lithium iron phosphate to iron in pyrite is 1:2.4) into a porcelain boat and place it in the middle of a tube furnace. Let air flow in at a flow rate of 1.5 L / min. Heat and calcine at 400° C. for 4 hours to obtain 5.86 g of calcined lithium iron phosphate. S2, the calcined lithium iron phosphate was slurried with 50 mL of water for a reaction time of 1.0 h at a temperature of 60 ° C. After the reaction, lithium sulfate solution, iron phosphate, iron oxide and carbon were obtained by filtration. The Li content in the solution was 5.315 wt % by ICP detection. The lithium leaching rate was calculated to be 99%; S3, weighing 2 g of the iron phosphate in step S2, adding 40 mL of 0.009 mol / L copper sulfate solution and ultrasonicating for half an hour to obtain a solution containing an iron-copper complex, adding 0.1 mol / L NaOH to the solution of the iron-copper complex to adjust the pH of the solution to 7.45, and then ultrasonicating for one hour, subjecting the ultrasonic solution to a hydrothermal reaction, centrifuging the hydrothermal solution three times, and drying to obtain a mixed solid of the iron-copper complex and carbon; S4, weighing 100 mg of the iron-copper complex and carbon mixed solid of step S3, adding it to 100 mL of a 25 mg / L tetracycline hydrochloride aqueous solution, adsorbing it in the dark for 0.5 h, irradiating it with simulated sunlight to degrade the antibiotic, testing the absorbance of the reaction solution, and calculating that the degradation rate of tetracycline hydrochloride reached 58.56%; Example 3 A method for resource utilization of waste lithium iron phosphate battery positive electrode materials, comprising the following steps: S1. Put 2 g of waste lithium iron phosphate positive electrode material powder with a particle size of ≤50 mesh and 4 g of crushed pyrite powder (the molar ratio of iron in lithium iron phosphate to iron in pyrite is 1:1.9) into a porcelain boat and place it in the middle of a tube furnace. Let air flow in at a flow rate of 2 L / min. Heat and calcine at 400° C. for 5 h to obtain 5.87 g of calcined lithium iron phosphate. S2, the calcined lithium iron phosphate was slurried with 50 mL of water for 1.5 h at a temperature of 60 ° C. After the reaction, lithium sulfate solution, iron phosphate, iron oxide and carbon were obtained by filtration. The Li content in the solution was 5.39 wt % by ICP detection. The lithium leaching rate was calculated to be 99%; S3, weighing 3.5 g of the iron phosphate in step S2, adding 40 mL of 0.011 mol / L copper sulfate solution and ultrasonicating for half an hour to obtain a solution containing an iron-copper complex, adding 0.1 mol / L NaOH to the solution of the iron-copper complex to adjust the pH of the solution to 7.40, and then ultrasonicating for one hour, subjecting the ultrasonic solution to a hydrothermal reaction, centrifuging the hydrothermal solution three times, and drying to obtain a mixed solid of the iron-copper complex and carbon; S4, weighing 50 mg of the iron-copper complex and carbon mixed solid of step S3, adding it to 100 mL of a 25 mg / L tetracycline hydrochloride aqueous solution, adsorbing it in the dark for 0.5 h, irradiating it with simulated sunlight to degrade the antibiotic, and testing the absorbance of the reaction solution. It was calculated that the degradation rate of tetracycline hydrochloride reached 50.11%; Comparative Example 1 The difference from Example 1 is that the material calcination time in step S1 is 0.5 h.

[0025] The lithium leaching rate in this comparative example dropped to 63.5%.

[0026] Comparative Example 2 The difference from Example 1 is that the concentration of copper sulfate in step S3 is 0.003 mol / L.

[0027] The degradation rate of tetracycline hydrochloride in this comparative example is 45%.

[0028] Comparative Example 3 The difference from Embodiment 1 is that step S3 is not performed.

[0029] The degradation rate of tetracycline hydrochloride in this comparative example is 0.

[0030] It can be seen from the above embodiments and comparative examples that the present invention crushes and sieves waste lithium iron phosphate battery positive electrode materials, mixes them evenly with pyrite, and puts them into a tubular furnace, and obtains solid A after heating and calcining in an air environment; solid A is slurried with water for reaction, and filtered after the reaction to obtain filtrate B and solid B; solid B is dried and ground, taken out, and added with copper sulfate solution for ultrasonication to obtain solution C, and then NaOH solution is added to solution C to adjust the pH of the solution and then ultrasonicated, the ultrasonicated solution C is hydrothermally reacted, the hydrothermal solution C is centrifuged, and dried to obtain solid C; the solid C obtained by the method is used as a catalyst for degrading antibiotics in water bodies, and the filtrate B is separated and purified to prepare battery-grade lithium carbonate required as a raw material for lithium batteries, thereby realizing the resource utilization of all elements of waste lithium iron phosphate battery positive electrode materials.

[0031] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for resource utilization of waste lithium iron phosphate battery positive electrode materials, characterized in that: The steps include: S1, the waste lithium iron phosphate battery positive electrode material is crushed and sieved, and then mixed with pyrite, and heated and calcined in an air environment to obtain solid A; S2, solid A is slurried with water for reaction, and after the reaction, filtrate is filtered to obtain filtrate B and solid B; S3, solid B is dried and ground, taken out, and copper sulfate solution is added to obtain solution C by ultrasonication, and then NaOH solution is added to solution C to adjust the pH of solution C and then ultrasonication is performed, and solution C after ultrasonication is subjected to hydrothermal reaction, and solution C after hydrothermal reaction is centrifuged and dried to obtain solid C; S4. Solid C is added into a solution containing antibiotics, and the antibiotics are degraded through dark adsorption and light reaction. The filtrate B is enriched and impurities are removed, and then precipitated and separated to extract lithium.

2. The method for resource utilization of waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: In the step S1, the particle size of the crushed and sieved waste lithium iron phosphate battery positive electrode material powder is ≤50 mesh; the molar ratio of iron in the crushed and sieved waste lithium iron phosphate battery positive electrode material powder to iron in pyrite is 1:(1.8-2.6).

3. The method for resource utilization of waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: In the step S1, heating and calcination are carried out in a tubular furnace, the reaction temperature is 200-600° C., the reaction time is 1.5-5.0 h, and the air flow rate is 1-2 L / min.

4. The method for resource utilization of waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: In step S2, the reaction time is 0.5-2.5 hours, and the reaction temperature is 25-90°C.

5. The method for resource utilization of waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: In step S2, the filtrate B is a lithium-containing solution, and the lithium leaching rate is ≥98%. After enrichment, the lithium element is separated and extracted by precipitation. The lithium can be used as a raw material for lithium-ion batteries, catalysts, ceramics, and glass to achieve resource utilization.

6. The method for resource utilization of waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: In step S3, the solid-to-liquid ratio of solid B to copper sulfate solution is (1-5) g / 50 mL; and the concentration of copper sulfate solution is 0.008-0.020 mol / L.

7. The method for resource utilization of waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: In step S3, the concentration of the NaOH solution is 0.01-1.00 mol / L, the pH is 7.00-8.00, the hydrothermal reaction time is 2-5 h, and the hydrothermal reaction temperature is 100-150° C.

8. The method for resource utilization of waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: In the step S4, the antibiotics are a series of electron-rich antibiotics.

9. The method for resource utilization of waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: In step S4, the degradation rate of the antibiotic is ≥50%.