A Method and Application for Recycling and Regenerating Lithium from Power Batteries

Abstract

The present invention relates to a method and application for recycling and regenerating lithium from power batteries. Before lithium slag is leached, sodium trithiocarbonate is doped for activation and roasting, and then supercritical secondary activation is combined to effectively improve the dissolution rate of iron and lithium. In the supercritical secondary activation process, perfluoroalkyl phosphate surfactant is used for synergistic enhancement, which not only further improves the dissolution rate of iron and lithium in the subsequent acid leaching process, but also realizes the selective passivation of impurity ions and reduces Al 3+ 、Si 4+ Plasma dissolution improves the leaching purity of iron and lithium; the two-stage acid leaching purification combined with photocatalysts can achieve efficient leaching and separation of iron and lithium. The recovered lithium carbonate and iron phosphate are of high purity, meeting the production requirements of battery-grade LiFePO4, and the process is efficient and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery recycling, and specifically relates to a method and application of recycling and regenerating lithium from power batteries. Background Art

[0002] With the explosive growth of the global new energy vehicle industry, the number of retired power batteries has reached a peak. The scarcity of metal resources such as lithium, cobalt, and nickel, as well as the risk of heavy metals and electrolyte contamination in used batteries, have jointly made the waste battery recycling industry a strategic priority for green development.

[0003] Currently, the mainstream technology for recycling lithium from power batteries is centered around hydrometallurgy, supplemented by pyrometallurgy, physical methods, and biological methods, forming a "hydrometallurgical-based, multi-technical collaborative" approach. For the recovery of iron and lithium from lithium slag, the most established methods include magnetic separation, acid leaching, and grinding and calcination. Magnetic separation is only suitable for slag samples with high iron content, and its recovery rate is relatively low, resulting in low product purity. The production of battery-grade LiFePO4 requires multiple purification steps and processing, and its production capacity is low, making it unsuitable for industrialization. The grinding and calcination method currently offers the highest iron and lithium recovery rates in industrial production, but the recovery process is relatively harsh, environmentally unfriendly, and the leaching stage has low selectivity, resulting in a high number of impurities, making subsequent purification difficult and limiting product purity. While the acid leaching method has relatively mild conditions, it consumes a large amount of acid and is cumbersome to dispose of the wastewater. Our company's invention application ZL202411691103.7 developed a leaching method that effectively reduces impurity dissolution, reduces acid and alkali consumption, and achieves full recovery of phosphorus, iron, and lithium. The resulting iron phosphate and lithium carbonate produced by this process meet battery-grade requirements. However, the patent does not provide in-depth research on the dissolution rates of iron and lithium, and no breakthrough in metal recovery has been achieved. Therefore, developing a process that improves metal dissolution rates, simplifies the leaching process, increases product recovery purity, and achieves efficient and green regeneration and recovery is a key research priority in this industry. Summary of the Invention

[0004] In view of the above problems, the purpose of the present invention is to provide a method for recycling and regenerating lithium from power batteries with high iron and lithium recovery rates, high product purity, and high efficiency and environmental protection, specifically:

[0005] A method for recycling lithium from a power battery, comprising:

[0006] Discharge treatment: immerse the power battery in 5wt% NaCl solution with a liquid-to-solid ratio of 5:1 at room temperature for 24 hours;

[0007] Mechanical disassembly: The discharged batteries are frozen at -40℃ for 2h, crushed into particles ≤10mm, and then separated by vibrating screen and magnetic separation to separate the shell and electrode materials;

[0008] Pyrolysis of organic components: The electrode material was heated to 600°C at a rate of 10°C / min in a N2 atmosphere and kept at this temperature for 2 h. The pyrolysis gas was collected by activated carbon adsorption.

[0009] Calcination activation: The pyrolysis residue is mixed evenly with sodium trithiocarbonate in a mass ratio of 1:0.2, and calcined at 600-700°C for 1 hour. The tail gas is treated in an absorption tower;

[0010] Primary acid leaching: The activated residue was mixed with 25% H2SO4 at a solid-liquid ratio of 1:8, 1% H2O2 was added, and the mixture was stirred at 60°C for 4 hours, and the extract was filtered to obtain the extract; the pH of the extract was adjusted to 5.0 with NaOH, and saturated Na2CO3 was added, and the mixture was heated to 65°C-70°C for 15-20 minutes and then centrifuged. The filtrate was extracted and used as a raw material for Ni / Co / Mn ternary precursor; the filter residue was then calcined at 450°C for 2 hours to obtain regenerated lithium slag;

[0011] Fine extraction and dealumination: add the regenerated lithium slag to 20% by mass hydrochloric acid, heat in a water bath to 60°C-75°C, react for 10-15 minutes, filter, add 0.5% ascorbic acid and 0.5-1% photocatalyst according to the mass ratio of hydrochloric acid, stir at 300 rpm, irradiate with ultraviolet light for 1 hour, keep irradiating with ultraviolet light, add 2%-3% by mass fraction of 1% sodium fluoride aqueous solution, stir at 200 rpm for 10 minutes, and filter to obtain the fine extract;

[0012] Preparation of lithium iron phosphate: Add 3 times the phosphoric acid solution and 1.2 times the mass fraction of 10% hydrogen peroxide solution to the refined extract according to the mass ratio of hydrochloric acid, heat to 40℃-45℃, react for 2h, and then cool to room temperature. After vacuum filtration, the precipitate is washed twice with deionized water and dried in a vacuum oven to obtain iron phosphate. Add saturated Na2CO3 to the residual liquid obtained by vacuum filtration to make the pH reach 8-9, heat to 60℃, react for 1h, and then centrifuge to obtain lithium carbonate. After calcination at 450℃, mix with iron phosphate in a molar ratio of 0.52-0.55:1, and add ethanol for ball milling for 2h. After centrifugal drying, place it in a rotary kiln, heat to 750℃ at 2℃ / min, introduce argon, calcine for 8-10h, and cool naturally to obtain LiFePO4, which can be crushed to be used as battery-grade LiFePO4 raw material.

[0013] Preferably, the calcination activation also includes supercritical secondary activation: the residue after calcination activation is crushed to 100-200 mesh, 0.5-0.8% fluorine-containing surfactant is added, N2 is introduced to replace the air after sealing, low-speed stirring is started at 100rpm, the temperature is raised to 55°C and maintained for 30 minutes, the mass ratio of CO2 to residue is 20:1, the critical temperature is 31°C, the pressure is 8-12MPa, the CO2 flow rate is 15L / min, liquid CO2 is injected to 18MPa through a high-pressure pump, the temperature is raised to 55°C, the heating rate is 2°C / min, and then high-speed stirring is started at 300rpm. After the CO2 is introduced, the CO2 replacement of the entire system is completed every 15 minutes, and the process lasts for 2 hours. After the treatment is completed, the pressure is slowly released to normal pressure at a rate of 0.5MPa / min.

[0014] Preferably, the fluorinated surfactant is a perfluoroalkyl phosphate.

[0015] Preferably, the photocatalyst is prepared as follows: Bi(NO3)3 and NH4VO3 are dissolved in ethylene glycol in a molar ratio of 1:1, 2-4% citric acid is added, and the mixture is stirred at 80°C for 2 hours to form an orange-red sol; twice the amount of 2-aminoterephthalic acid is added to the sol, and the mixture is transferred to a hydrothermal kettle and reacted at 180°C for 12 hours; the precipitate is collected by centrifugation, washed three times with ethanol, dried in a vacuum at 60°C, and ground to obtain a BiVO4-MOF composite photocatalyst.

[0016] Beneficial effects of the present invention:

[0017] 1. The present invention develops an efficient and environmentally friendly method for recycling and regenerating lithium from power batteries, with high iron and lithium recovery rates and high product purity, meeting the production requirements of battery-grade LiFePO4.

[0018] 2. The present invention utilizes sodium trithiocarbonate doping and calcination for activation before acid leaching. This allows sulfur doping to introduce lattice defects, such as sulfur vacancies and distorted grain boundaries, into the lithium slag. This facilitates H⁺ penetration into the particles during subsequent acid leaching, significantly improving the dissolution rate of iron and lithium ions compared to conventional processes. Furthermore, the sulfur in the sodium trithiocarbonate forms sulfur-metal coordination bonds with metal ions, weakening the binding energy of Fe-O bonds and promoting iron dissolution. Furthermore, FePO₄ and Fe₂O₃, in a sulfur-reducing atmosphere, transform into a FeS-FePO₄ composite phase, which dissolves faster than the original FePO₄, further promoting iron dissolution. The sodium trithiocarbonate co-calcination pretreatment process, through the dual reducing and coordinating effects of sulfur, achieves chemical decoupling and crystal reconstruction of the iron phase during the pretreatment stage, laying the foundation for efficient subsequent leaching and iron phosphate regeneration.

[0019] 3. After the calcination treatment, the iron phase is decoupled and the crystal is reconstructed through the reduction-coordination effect of sulfur, thereby improving the dissolution rate of iron ions. However, the residual silicon-oxygen network, such as SiO2 or silicate, will still hinder the dissolution of iron and lithium. Therefore, the supercritical treatment used in the present invention can weaken the covalent effect of the Si-O bond, while facilitating the adhesion of the microemulsion system to the lithium slag, thereby enhancing the subsequent acid permeability and further promoting the subsequent iron and lithium leaching efficiency. The addition of perfluoroalkyl phosphate in the supercritical process can not only provide a microemulsion system, but also preferentially react with Al 3+ 、Si 4+ The impurity ions are coordinated to form a hydrophobic protective layer, which inhibits their reaction with acid. By selectively passivating impurities, the dissolution of impurities is reduced, and the purity of iron and lithium in the acid leaching solution is improved.

[0020] 4. This aspect achieves high-purity and high-yield recovery of iron and lithium through two-stage acid leaching. To address the problem of simultaneous high dissolution of aluminum during the roasting process, a first-stage acid leaching is used to allow it to co-precipitate with iron and lithium, and then a second acid dissolution is performed. In this stage, the iron and lithium can be completely dissolved, and the small amount of dissolved aluminum is treated with sodium fluoride secondary precipitation and adsorption, so that the subsequently recovered iron phosphate has high purity.

[0021] 5. During the fine extraction and dealumination process, photocatalyst is used to reduce Fe 3+ Compared with conventional reducing agents, photocatalysts can simulate Fe 2+ Oxidation can effectively reduce the iron loss during the dealumination process, and the introduction of the pore structure of MOF in the photocatalyst can effectively improve the catalytic efficiency. The photocatalyst is environmentally friendly and can be recycled and reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope image of the lithium iron phosphate prepared in the present invention. DETAILED DESCRIPTION

[0023] Use the same LEP type power waste batteries for recycling.

[0024] Example 1

[0025] Discharge treatment: immerse the power battery in 5wt% NaCl solution with a liquid-to-solid ratio of 5:1 at room temperature for 24 hours;

[0026] Mechanical disassembly: The discharged batteries are frozen at -40℃ for 2h, crushed into particles ≤10mm, and then separated by vibrating screen and magnetic separation to separate the shell and electrode materials;

[0027] Pyrolysis of organic components: The electrode material was heated to 600°C at a rate of 10°C / min in a N2 atmosphere and kept at this temperature for 2 h. The pyrolysis gas was collected by activated carbon adsorption.

[0028] Calcination activation: The pyrolysis residue was mixed with sodium trithiocarbonate in a mass ratio of 1:0.2 and calcined at 650°C for 1 h;

[0029] Primary acid leaching: The activated residue was mixed with 25% H2SO4 at a solid-liquid ratio of 1:8, 1% H2O2 was added, and the mixture was stirred at 60°C for 4 hours, and the extract was filtered to obtain the extract. The pH of the extract was adjusted to 5.0 with NaOH, and saturated Na2CO3 was added. The mixture was heated to 65°C for 20 minutes and then centrifuged. The filter residue was then calcined at 450°C for 2 hours to obtain the regenerated lithium slag.

[0030] Photocatalyst preparation: Bi(NO3)3 and NH4VO3 were dissolved in ethylene glycol at a 1:1 molar ratio, 3% citric acid was added, and the mixture was stirred at 80°C for 2 hours to form an orange-red sol. Twice the amount of 2-aminoterephthalic acid was added to the sol, and the mixture was transferred to a hydrothermal autoclave and reacted at 180°C for 12 hours. The precipitate was collected by centrifugation, washed three times with ethanol, dried in a vacuum at 60°C, and ground to obtain a BiVO4-MOF composite photocatalyst.

[0031] Fine extraction and dealumination: add the regenerated lithium slag to 20% hydrochloric acid by mass, heat to 70°C in a water bath, react for 10 minutes, filter, add 0.5% ascorbic acid and 1% photocatalyst, stir at 300 rpm, irradiate with ultraviolet light for 1 hour, keep irradiating with ultraviolet light, add 3% of 1% sodium fluoride aqueous solution by mass, stir at 200 rpm for 10 minutes, and filter to obtain the fine extract;

[0032] Iron lithium recovery: add 3 times the amount of phosphoric acid solution and 1.2 times the amount of 10% hydrogen peroxide solution by mass to the refined extract, heat to 45°C for 2 hours, and then cool to room temperature. Vacuum filter the precipitate, wash it twice with deionized water, and dry it in a vacuum oven to obtain iron phosphate. Add saturated Na2CO3 to the residual liquid obtained by vacuum filtration to make the pH reach 8.5, heat to 60°C for 1 hour, and then centrifuge. The precipitate is then calcined at 450°C to obtain lithium carbonate.

[0033] Example 2

[0034] Discharge treatment: immerse the power battery in 5wt% NaCl solution with a liquid-to-solid ratio of 5:1 at room temperature for 24 hours;

[0035] Mechanical disassembly: The discharged batteries are frozen at -40℃ for 2h, crushed into particles ≤10mm, and then separated by vibrating screen and magnetic separation to separate the shell and electrode materials;

[0036] Pyrolysis of organic components: The electrode material was heated to 600°C at a rate of 10°C / min in a N2 atmosphere and kept at this temperature for 2 h. The pyrolysis gas was collected by activated carbon adsorption.

[0037] Calcination activation: The pyrolysis residue was mixed with petroleum sulfonate in a mass ratio of 1:0.2 and calcined at 650°C for 1 h;

[0038] Primary acid leaching: The activated residue was mixed with 25% H2SO4 at a solid-liquid ratio of 1:8, 1% H2O2 was added, and the mixture was stirred at 60°C for 4 hours, and the extract was filtered to obtain the extract; the pH of the extract was adjusted to 5.0 with NaOH, and saturated Na2CO3 was added, and the mixture was heated to 70°C for 15 minutes and then centrifuged; the filter residue was then calcined at 450°C for 2 hours to obtain the regenerated lithium slag;

[0039] Photocatalyst preparation: Bi(NO3)3 and NH4VO3 were dissolved in ethylene glycol at a 1:1 molar ratio, 4% citric acid was added, and the mixture was stirred at 80°C for 2 hours to form an orange-red sol. Twice the amount of 2-aminoterephthalic acid was added to the sol, and the mixture was transferred to a hydrothermal autoclave and reacted at 180°C for 12 hours. The precipitate was collected by centrifugation, washed three times with ethanol, dried in a vacuum at 60°C, and ground to obtain a BiVO4-MOF composite photocatalyst.

[0040] Fine extraction and dealumination: add the regenerated lithium slag to 20% hydrochloric acid by mass, heat to 75°C in a water bath, react for 15 minutes, filter, add 0.5% ascorbic acid and 1% photocatalyst, stir at 300 rpm, irradiate with ultraviolet light for 1 hour, keep irradiating with ultraviolet light, add 3% of 1% sodium fluoride aqueous solution by mass, stir at 200 rpm for 10 minutes, and filter to obtain the fine extract;

[0041] Iron lithium recovery: add 3 times the amount of phosphoric acid solution and 1.2 times the amount of 10% hydrogen peroxide solution by mass to the refined extract, heat to 45°C for 2 hours, and then cool to room temperature. Vacuum filter the precipitate, wash it twice with deionized water, and dry it in a vacuum oven to obtain iron phosphate. Add saturated Na2CO3 to the residual liquid obtained by vacuum filtration to make the pH reach 8.5, heat to 60°C for 1 hour, and then centrifuge. The precipitate is then calcined at 450°C to obtain lithium carbonate.

[0042] Example 3

[0043] Discharge treatment: immerse the power battery in 5wt% NaCl solution with a liquid-to-solid ratio of 5:1 at room temperature for 24 hours;

[0044] Mechanical disassembly: The discharged batteries are frozen at -40℃ for 2h, crushed into particles ≤10mm, and then separated by vibrating screen and magnetic separation to separate the shell and electrode materials;

[0045] Pyrolysis of organic components: The electrode material was heated to 600°C at a rate of 10°C / min in a N2 atmosphere and kept at this temperature for 2 h. The pyrolysis gas was collected by activated carbon adsorption.

[0046] Calcination activation: the pyrolysis residue and sodium trithiocarbonate were mixed in a mass ratio of 1:0.2 and calcined at 600 ° C for 1 hour; the calcined and activated residue was crushed to 100-200 mesh, sealed and introduced into the air to replace N2, low-speed stirring was started at 100 rpm, the temperature was raised to 55 ° C and maintained for 30 minutes, the mass ratio of CO2 to residue was 20:1, the critical temperature was 31 ° C, the pressure was 10 MPa, the CO2 flow rate was 15 L / min, liquid CO2 was injected to 18 MPa through a high-pressure pump, the temperature was raised to 55 ° C, the heating rate was 2 ° C / min, and then high-speed stirring was started at 300 rpm. After the CO2 was introduced, the CO2 replacement of the entire system was completed every 15 minutes for 2 hours. After the treatment was completed, the pressure was slowly released to normal pressure at a rate of 0.5 MPa / min;

[0047] Primary acid leaching: The activated residue was mixed with 25% H2SO4 at a solid-liquid ratio of 1:8, 1% H2O2 was added, and the mixture was stirred at 60°C for 4 hours, and the extract was filtered to obtain the extract; the pH of the extract was adjusted to 5.0 with NaOH, and saturated Na2CO3 was added, and the mixture was heated to 70°C for 15 minutes and then centrifuged; the filter residue was then calcined at 450°C for 2 hours to obtain the regenerated lithium slag;

[0048] Photocatalyst preparation: Bi(NO3)3 and NH4VO3 were dissolved in ethylene glycol at a 1:1 molar ratio, 3% citric acid was added, and the mixture was stirred at 80°C for 2 hours to form an orange-red sol. Twice the amount of 2-aminoterephthalic acid was added to the sol, and the mixture was transferred to a hydrothermal autoclave and reacted at 180°C for 12 hours. The precipitate was collected by centrifugation, washed three times with ethanol, dried in a vacuum at 60°C, and ground to obtain a BiVO4-MOF composite photocatalyst.

[0049] Fine extraction and dealumination: add the regenerated lithium slag to 20% hydrochloric acid by mass, heat to 60°C in a water bath, react for 15 minutes, filter, add 0.5% ascorbic acid and 1% photocatalyst, stir at 300 rpm, irradiate with ultraviolet light for 1 hour, keep irradiating with ultraviolet light, add 2% of 1% sodium fluoride aqueous solution by mass, stir at 200 rpm for 10 minutes, and filter to obtain the fine extract;

[0050] Iron lithium recovery: add 3 times the amount of phosphoric acid solution and 1.2 times the amount of 10% hydrogen peroxide solution by mass to the refined extract, heat to 45°C, react for 2 hours, and then cool to room temperature. Vacuum filter the precipitate, wash it twice with deionized water, and dry it in a vacuum oven to obtain iron phosphate. Add saturated Na2CO3 to the residual liquid obtained by vacuum filtration to make the pH reach 9, heat to 60°C, react for 1 hour, and then centrifuge. The precipitate is then calcined at 450°C to obtain lithium carbonate.

[0051] Example 4

[0052] Discharge treatment: immerse the power battery in 5wt% NaCl solution with a liquid-to-solid ratio of 5:1 at room temperature for 24 hours;

[0053] Mechanical disassembly: The discharged batteries are frozen at -40℃ for 2h, crushed into particles ≤10mm, and then separated by vibrating screen and magnetic separation to separate the shell and electrode materials;

[0054] Pyrolysis of organic components: The electrode material was heated to 600°C at a rate of 10°C / min in a N2 atmosphere and kept at this temperature for 2 h. The pyrolysis gas was collected by activated carbon adsorption.

[0055] Calcination activation: the pyrolysis residue and sodium trithiocarbonate were mixed in a mass ratio of 1:0.2 and calcined at 700 ° C for 1 hour; the calcined and activated residue was crushed to 100-200 mesh, 0.5% perfluoroalkyl phosphate was added, and N2 was introduced to replace the air after sealing. Low-speed stirring was started at 100 rpm, and the temperature was raised to 55 ° C and maintained for 30 minutes. The mass ratio of CO2 to residue was 20:1, the critical temperature was 31 ° C, the pressure was 8 MPa, the CO2 flow rate was 15 L / min, and liquid CO2 was injected to 18 MPa through a high-pressure pump. The temperature was raised to 55 ° C at a heating rate of 2 ° C / min, and then high-speed stirring was started at 300 rpm. After CO2 was introduced, CO2 replacement of the entire system was completed every 15 minutes for 2 hours. After the treatment was completed, the pressure was slowly released to normal pressure at a rate of 0.5 MPa / min.

[0056] Primary acid leaching: The activated residue was mixed with 25% H2SO4 at a solid-liquid ratio of 1:8, 1% H2O2 was added, and the mixture was stirred at 60°C for 4 hours, and the extract was filtered to obtain the extract; the pH of the extract was adjusted to 5.0 with NaOH, and saturated Na2CO3 was added, and the mixture was heated to 65°C for 20 minutes and then centrifuged; the filter residue was then calcined at 450°C for 2 hours to obtain the regenerated lithium slag;

[0057] Photocatalyst preparation: Bi(NO3)3 and NH4VO3 were dissolved in ethylene glycol at a 1:1 molar ratio, 2% citric acid was added, and the mixture was stirred at 80°C for 2 hours to form an orange-red sol. Twice the amount of 2-aminoterephthalic acid was added to the sol, and the mixture was transferred to a hydrothermal autoclave and reacted at 180°C for 12 hours. The precipitate was collected by centrifugation, washed three times with ethanol, dried in a vacuum at 60°C, and ground to obtain a BiVO4-MOF composite photocatalyst.

[0058] Fine extraction and dealumination: add the regenerated lithium slag to 20% hydrochloric acid by mass, heat to 75°C in a water bath, react for 15 minutes, filter, add 0.5% ascorbic acid and 1% photocatalyst, stir at 300 rpm, irradiate with ultraviolet light for 1 hour, keep irradiating with ultraviolet light, add 3% of 1% sodium fluoride aqueous solution by mass, stir at 200 rpm for 10 minutes, and filter to obtain the fine extract;

[0059] Iron lithium recovery: add 3 times the amount of phosphoric acid solution and 1.2 times the amount of 10% hydrogen peroxide solution by mass to the refined extract, heat to 40°C, react for 2 hours, and then cool to room temperature. Vacuum filter the precipitate, wash it twice with deionized water, and dry it in a vacuum oven to obtain iron phosphate. Add saturated Na2CO3 to the residual liquid obtained by vacuum filtration to make the pH reach 8, heat to 60°C, react for 1 hour, and then centrifuge. The precipitate is then calcined at 450°C to obtain lithium carbonate.

[0060] Example 5

[0061] Discharge treatment: immerse the power battery in 5wt% NaCl solution with a liquid-to-solid ratio of 5:1 at room temperature for 24 hours;

[0062] Mechanical disassembly: The discharged batteries are frozen at -40℃ for 2h, crushed into particles ≤10mm, and then separated by vibrating screen and magnetic separation to separate the shell and electrode materials;

[0063] Pyrolysis of organic components: The electrode material was heated to 600°C at a rate of 10°C / min in a N2 atmosphere and kept at this temperature for 2 h. The pyrolysis gas was collected by activated carbon adsorption.

[0064] Calcination activation: the pyrolysis residue and sodium trithiocarbonate were mixed in a mass ratio of 1:0.2 and calcined at 650 ° C for 1 hour; the calcined and activated residue was crushed to 100-200 mesh, 0.8% sodium lauryl sulfate was added, and the air was replaced by N2 after sealing. The low-speed stirring was started at 100 rpm, and the temperature was raised to 55 ° C and maintained for 30 minutes. The mass ratio of CO2 to residue was 20:1, the critical temperature was 31 ° C, the pressure was 10 MPa, and the CO2 flow rate was 15 L / min. Liquid CO2 was injected to 18 MPa through a high-pressure pump, and the temperature was raised to 55 ° C at a heating rate of 2 ° C / min. Then, high-speed stirring was started at 300 rpm. After the CO2 was introduced, the CO2 replacement of the entire system was completed every 15 minutes for 2 hours. After the treatment was completed, the pressure was slowly released to normal pressure at a rate of 0.5 MPa / min.

[0065] Primary acid leaching: The activated residue was mixed with 25% H2SO4 at a solid-liquid ratio of 1:8, 1% H2O2 was added, and the mixture was stirred at 60°C for 4 hours, and the extract was filtered to obtain the extract; the pH of the extract was adjusted to 5.0 with NaOH, and saturated Na2CO3 was added, and the mixture was heated to 70°C for 15 minutes and then centrifuged; the filter residue was then calcined at 450°C for 2 hours to obtain the regenerated lithium slag;

[0066] Photocatalyst preparation: Bi(NO3)3 and NH4VO3 were dissolved in ethylene glycol at a 1:1 molar ratio, 3% citric acid was added, and the mixture was stirred at 80°C for 2 hours to form an orange-red sol. Twice the amount of 2-aminoterephthalic acid was added to the sol, and the mixture was transferred to a hydrothermal autoclave and reacted at 180°C for 12 hours. The precipitate was collected by centrifugation, washed three times with ethanol, dried in a vacuum at 60°C, and ground to obtain a BiVO4-MOF composite photocatalyst.

[0067] Fine extraction and dealumination: add the regenerated lithium slag to 20% hydrochloric acid by mass, heat to 65°C in a water bath, react for 15 minutes, filter, add 0.5% ascorbic acid and 1% photocatalyst, stir at 300 rpm, irradiate with ultraviolet light for 1 hour, keep irradiating with ultraviolet light, add 3% of 1% sodium fluoride aqueous solution by mass, stir at 200 rpm for 10 minutes, and filter to obtain the fine extract;

[0068] Iron lithium recovery: add 3 times the amount of phosphoric acid solution and 1.2 times the amount of 10% hydrogen peroxide solution by mass to the refined extract, heat to 45°C, react for 2 hours, and then cool to room temperature. Vacuum filter the precipitate, wash it twice with deionized water, and dry it in a vacuum oven to obtain iron phosphate. Add saturated Na2CO3 to the residual liquid obtained by vacuum filtration to make the pH reach 9, heat to 60°C, react for 1 hour, and then centrifuge. The precipitate is then calcined at 450°C to obtain lithium carbonate.

[0069] Example 6

[0070] Discharge treatment: immerse the power battery in 5wt% NaCl solution with a liquid-to-solid ratio of 5:1 at room temperature for 24 hours;

[0071] Mechanical disassembly: The discharged batteries are frozen at -40℃ for 2h, crushed into particles ≤10mm, and then separated by vibrating screen and magnetic separation to separate the shell and electrode materials;

[0072] Pyrolysis of organic components: The electrode material was heated to 600°C at a rate of 10°C / min in a N2 atmosphere and kept at this temperature for 2 h. The pyrolysis gas was collected by activated carbon adsorption.

[0073] Calcination activation: the pyrolysis residue and sodium trithiocarbonate were mixed in a mass ratio of 1:0.2 and calcined at 700 ° C for 1 hour; the calcined and activated residue was crushed to 100-200 mesh, 0.5% perfluoroalkyl phosphate was added, and N2 was introduced to replace the air after sealing. Low-speed stirring was started at 100 rpm, and the temperature was raised to 55 ° C and maintained for 30 minutes. The mass ratio of CO2 to residue was 20:1, the critical temperature was 31 ° C, the pressure was 8 MPa, the CO2 flow rate was 15 L / min, and liquid CO2 was injected to 18 MPa through a high-pressure pump. The temperature was raised to 55 ° C at a heating rate of 2 ° C / min, and then high-speed stirring was started at 300 rpm. After CO2 was introduced, CO2 replacement of the entire system was completed every 15 minutes for 2 hours. After the treatment was completed, the pressure was slowly released to normal pressure at a rate of 0.5 MPa / min.

[0074] Primary acid leaching: The activated residue was mixed with 25% H2SO4 at a solid-liquid ratio of 1:8, 1% H2O2 was added, and the mixture was stirred at 60°C for 4 hours, and the extract was filtered to obtain the extract; the pH of the extract was adjusted to 5.0 with NaOH, and saturated Na2CO3 was added, and the mixture was heated to 65°C for 20 minutes and then centrifuged; the filter residue was then calcined at 450°C for 2 hours to obtain the regenerated lithium slag;

[0075] Fine extraction and dealumination: add the regenerated lithium slag to 20% hydrochloric acid by mass, heat to 75°C in a water bath, react for 15 minutes, filter, add 0.5% ascorbic acid and 1% oxalic acid, stir at 300 rpm, irradiate with ultraviolet light for 1 hour, keep irradiating with ultraviolet light, add 3% of 1% sodium fluoride aqueous solution by mass, stir at 200 rpm for 10 minutes, and filter to obtain the fine extract;

[0076] Iron lithium recovery: add 3 times the amount of phosphoric acid solution and 1.2 times the amount of 10% hydrogen peroxide solution by mass to the refined extract, heat to 40°C, react for 2 hours, and then cool to room temperature. Vacuum filter the precipitate, wash it twice with deionized water, and dry it in a vacuum oven to obtain iron phosphate. Add saturated Na2CO3 to the residual liquid obtained by vacuum filtration to make the pH reach 8, heat to 60°C, react for 1 hour, and then centrifuge. The precipitate is then calcined at 450°C to obtain lithium carbonate.

[0077] Example 7

[0078] Discharge treatment: immerse the power battery in 5wt% NaCl solution with a liquid-to-solid ratio of 5:1 at room temperature for 24 hours;

[0079] Mechanical disassembly: The discharged batteries are frozen at -40℃ for 2h, crushed into particles ≤10mm, and then separated by vibrating screen and magnetic separation to separate the shell and electrode materials;

[0080] Pyrolysis of organic components: The electrode material was heated to 600°C at a rate of 10°C / min in a N2 atmosphere and kept at this temperature for 2 h. The pyrolysis gas was collected by activated carbon adsorption.

[0081] Calcination activation: the pyrolysis residue and sodium trithiocarbonate were mixed in a mass ratio of 1:0.2 and calcined at 700 ° C for 1 hour; the calcined and activated residue was crushed to 100-200 mesh, 0.5% perfluoroalkyl phosphate was added, and N2 was introduced to replace the air after sealing. Low-speed stirring was started at 100 rpm, and the temperature was raised to 55 ° C and maintained for 30 minutes. The mass ratio of CO2 to residue was 20:1, the critical temperature was 31 ° C, the pressure was 8 MPa, the CO2 flow rate was 15 L / min, and liquid CO2 was injected to 18 MPa through a high-pressure pump. The temperature was raised to 55 ° C at a heating rate of 2 ° C / min, and then high-speed stirring was started at 300 rpm. After CO2 was introduced, CO2 replacement of the entire system was completed every 15 minutes for 2 hours. After the treatment was completed, the pressure was slowly released to normal pressure at a rate of 0.5 MPa / min.

[0082] Primary acid leaching: The activated residue was mixed with 25% H2SO4 at a solid-liquid ratio of 1:8, 1% H2O2 was added, and the mixture was stirred at 60°C for 4 hours, and the extract was filtered to obtain the extract; the pH of the extract was adjusted to 5.0 with NaOH, and saturated Na2CO3 was added, and the mixture was heated to 65°C for 20 minutes and then centrifuged; the filter residue was then calcined at 450°C for 2 hours to obtain the regenerated lithium slag;

[0083] Photocatalyst preparation: Bi(NO3)3 and NH4VO3 were dissolved in ethylene glycol at a molar ratio of 1:1, heated in a hydrothermal autoclave, and reacted at 180°C for 12 h. The precipitate was collected by centrifugation, washed three times with ethanol, dried in a vacuum oven at 60°C, and ground to obtain the BiVO4 photocatalyst.

[0084] Fine extraction and dealumination: add the regenerated lithium slag to 20% hydrochloric acid by mass, heat to 75°C in a water bath, react for 15 minutes, filter, add 0.5% ascorbic acid and 1% photocatalyst, stir at 300 rpm, irradiate with ultraviolet light for 1 hour, keep irradiating with ultraviolet light, add 3% of 1% sodium fluoride aqueous solution by mass, stir at 200 rpm for 10 minutes, and filter to obtain the fine extract;

[0085] Iron lithium recovery: add 3 times the amount of phosphoric acid solution and 1.2 times the amount of 10% hydrogen peroxide solution by mass to the refined extract, heat to 40°C, react for 2 hours, and then cool to room temperature. Vacuum filter the precipitate, wash it twice with deionized water, and dry it in a vacuum oven to obtain iron phosphate. Add saturated Na2CO3 to the residual liquid obtained by vacuum filtration to make the pH reach 8, heat to 60°C, react for 1 hour, and then centrifuge. The precipitate is then calcined at 450°C to obtain lithium carbonate.

[0086] Test 1:

[0087] The 5 recovery control groups were treated as follows:

[0088] Discharge: Immerse the power battery in 5wt% NaCl solution with a liquid-to-solid ratio of 5:1 at room temperature for 24 hours;

[0089] Activation: The positive electrode sheet is crushed and ground into particles ≤ 10 mm; the positive electrode sheet particles are placed in a resistance furnace, nitrogen is introduced into the resistance furnace, the air in the resistance furnace is exhausted, and then the temperature is heated to 225°C, kept at this temperature for 35 minutes, then the temperature is increased to 520°C at 20°C / s, kept at this temperature for 31 minutes, then the temperature is decreased to 370°C at 15°C / s, kept at this temperature for 25 minutes, and cooled to room temperature with the furnace;

[0090] Acid leaching: The calcined positive electrode particles were added to a mixed acid solution of 4% nitric acid and 7% sulfuric acid at a solid-liquid ratio of 2:30, stirred and dissolved for 4 hours to obtain a mixed solution, and then the mixed solution was filtered to obtain a filtrate; a mixed alkaline agent of sodium hydroxide and potassium hydroxide at a mass ratio of 3:1.2 was added to the filtrate to react, the temperature was adjusted to 53°C, and the mixture was stirred for 1 hour, and then the temperature was adjusted to 83°C, and the mixture was kept warm for 35 minutes, and then filtered to obtain a secondary reaction solution and a precipitate;

[0091] Lithium extraction: adding the secondary reaction liquid to the reactor, and then adding sodium carbonate to the secondary reaction liquid twice, the mass ratio of sodium carbonate to the secondary reaction liquid is 1:10, and the amount of sodium carbonate added for the second time is twice the amount of sodium carbonate added for the first time; after the first addition of sodium carbonate, stirring for 10 minutes, then adjusting the pressure in the reactor to 8.5MPa and the temperature to 73°C, stirring at this temperature for 35 minutes, and then adding sodium carbonate for the second time, maintaining the pressure and temperature in the reactor, continuing to stir and react for 1 hour, and then filtering, washing, drying, and then calcining at 450°C to obtain lithium carbonate;

[0092] Iron recovery: add the precipitate to 20% hydrochloric acid by mass, heat to 75°C in a water bath, react for 15 minutes, filter, add 0.5% ascorbic acid and 1% photocatalyst, stir at 300 rpm, irradiate with ultraviolet light for 1 hour, keep irradiating with ultraviolet light, add 3% of 1% sodium fluoride aqueous solution by mass, stir at 200 rpm for 10 minutes, and filter to obtain a refined extract; add 3 times of phosphoric acid solution and 1.2 times of 10% hydrogen peroxide solution by mass to the refined extract, heat to 40°C for 2 hours, then cool to room temperature, filter by vacuum filtration, wash the precipitate twice with deionized water, and dry in a vacuum oven to obtain iron phosphate.

[0093] The groups treated by the recovery control group were excluding the groups with the highest and lowest recovery rates. The average value of lithium carbonate and iron phosphate recovery in the remaining three groups was used as the theoretical recovery rate. The results of each embodiment are compared in the following table:

[0094]

[0095] Test 2:

[0096] The lithium carbonate prepared in Example 4 was mixed with iron phosphate in a molar ratio of 0.55:1, and ethanol was added and ball-milled for 2 h. After centrifugal drying, the mixture was placed in a rotary kiln and heated to 750 ° C at 2 ° C / min. Argon was introduced and the mixture was calcined for 9 h and then naturally cooled to obtain LiFePO4 (scanning electron microscopy shows Figure 1 ), the product performance was tested, and the results are as follows:

[0097]

Claims

1. A method for recycling regenerated lithium from a power battery, characterized in that: The preparation process is: Discharge treatment: immerse the power battery in 5wt% NaCl solution with a liquid-to-solid ratio of 5:1 at room temperature for 24 hours; Mechanical disassembly: The discharged batteries are frozen at -40℃ for 2h, crushed into particles ≤10mm, and then separated by vibrating screen and magnetic separation to separate the shell and electrode materials; Pyrolysis of organic components: The electrode material was heated to 600°C at a rate of 10°C / min in a N2 atmosphere and kept at this temperature for 2 h. The pyrolysis gas was collected by activated carbon adsorption. Calcination activation: The pyrolysis residue was mixed with sodium trithiocarbonate in a mass ratio of 1:0.2 and calcined at 600-700°C for 1 hour; Primary acid leaching: The above-mentioned calcined activated residue was mixed with 25% H2SO4 by mass at a solid-liquid ratio of 1:8, 1% H2O2 was added, and the mixture was stirred at 60°C for 4 hours, and the extract was filtered to obtain a leachate; the pH of the leachate was adjusted to 5.0 with NaOH, and saturated Na2CO3 was added, and the mixture was heated to 65°C-70°C for 15-20 minutes and then centrifuged; the filter residue was then calcined at 450°C for 2 hours to obtain a regenerated lithium slag; Refined extraction and dealumination: add the regenerated lithium slag to 20% hydrochloric acid by mass, heat in a water bath to 60°C-75°C, react for 10-15 minutes, filter, add 0.5% ascorbic acid and 0.5-1% photocatalyst, stir at 300 rpm, irradiate with ultraviolet light for 1 hour, keep irradiating with ultraviolet light, add 2%-3% of 1% sodium fluoride aqueous solution by mass, stir at 200 rpm for 10 minutes, and filter to obtain refined extract; Preparation of lithium iron phosphate: add 3 times of phosphoric acid solution and 1.2 times of 10% hydrogen peroxide solution by mass to the refined extract, heat to 40℃-45℃ for reaction for 2h, then cool to room temperature, filter by vacuum, wash the precipitate twice with deionized water, and dry in a vacuum oven to obtain iron phosphate. Add saturated Na2CO3 to the residual liquid obtained by vacuum filtration to make the pH reach 8-9, heat to 60℃ for reaction for 1h, and centrifuge to obtain lithium carbonate. After calcination at 450℃, mix with iron phosphate in a molar ratio of 0.52-0.55:1, add ethanol and ball mill for 2h, centrifuge and dry, place in a rotary kiln, heat to 750℃ at 2℃ / min, introduce argon, calcine for 8-10h, and cool naturally to obtain LiFePO4, which is then crushed.

2. The method for recycling lithium from a power battery according to claim 1, wherein: The calcination activation also includes supercritical secondary activation: the calcined activated residue is crushed to 100-200 mesh, 0.5-0.8% of a fluorine-containing surfactant is added, N2 is introduced to replace the air after sealing, low-speed stirring is started at 100 rpm, the temperature is raised to 55°C and maintained for 30 minutes, liquid CO2 is injected to 18 MPa through a high-pressure pump, the temperature is raised to 55°C, the heating rate is 2°C / min, and then high-speed stirring is started at 300 rpm. After the treatment is completed, the pressure is slowly released to normal pressure at a rate of 0.5 MPa / min.

3. The method for recycling lithium from a power battery according to claim 2, wherein: The fluorine-containing surfactant is perfluoroalkyl phosphate.

4. The method for recycling lithium from a power battery according to claim 1, wherein: The photocatalyst is prepared as follows: Bi(NO3)3 and NH4VO3 are dissolved in ethylene glycol in a molar ratio of 1:1, 2-4% citric acid is added, and the mixture is stirred at 80°C for 2 hours to form an orange-red sol; twice the amount of 2-aminoterephthalic acid is added to the sol, and the mixture is transferred to a hydrothermal kettle and reacted at 180°C for 12 hours; the precipitate is collected by centrifugation, washed three times with ethanol, dried in a vacuum at 60°C, and ground to obtain a BiVO4-MOF composite photocatalyst.

5. Use of the method for recycling and regenerating lithium from power batteries according to any of the above claims in recycling waste power lithium batteries to prepare battery-grade LiFePO4.

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