A method for leaching retired ternary lithium battery positive electrode material based on choline chloride-leucic acid eutectic solvent

Abstract

This invention discloses a leaching method for cathode materials from retired ternary lithium batteries based on a eutectic solvent of choline chloride and levulinic acid (DES). The method includes the following steps: 1) separating cathode powder from retired ternary lithium batteries after disassembly and discharge; 2) mixing choline chloride and levulinic acid as a eutectic solvent (DES); 3) mixing the cathode powder with DES and stirring to obtain a leachate. This invention achieves efficient leaching of lithium, nickel, cobalt, and manganese from waste cathode materials under mild conditions using a low-viscosity and highly reducing DES system.

Description

Technical Field

[0001] This invention relates to the field of resource recycling technology for retired lithium-ion batteries, specifically to a leaching method for the cathode material of retired ternary lithium batteries based on a eutectic solvent of choline chloride and levulinic acid. Background Technology

[0002] With the global energy structure shifting towards cleaner energy sources, applications such as electric vehicles and electrochemical energy storage have driven the explosive growth of the lithium-ion battery (LIB) industry. According to industry data, China's total lithium battery production reached 940 GWh in 2023, with a value exceeding 1.4 trillion yuan. However, lithium-ion batteries have a limited service life (power batteries approximately 5-10 years), and large-scale application inevitably leads to a peak in their retirement. It is predicted that by 2030, the global total amount of waste LIBs will exceed 2 million tons, and the Chinese market size for retired lithium batteries is expected to reach 150 billion yuan. Improper disposal of these retired batteries will severely pollute the environment and water sources due to the heavy metals they contain (such as nickel, cobalt, and copper) and the fluorides produced by electrolyte decomposition. On the other hand, the valuable metals such as lithium, nickel, cobalt, and manganese in the cathode materials have a much higher grade than primary ores, making efficient recycling crucial for ensuring national strategic resource security and achieving a circular economy.

[0003] Currently, commercial recycling technologies for cathode materials from retired lithium-ion batteries mainly follow three technical routes: pyrometallurgy, hydrometallurgy, and direct remediation and regeneration. However, these existing technologies all have their own significant drawbacks, making it difficult to achieve an ideal balance between economic benefits, environmental friendliness, and resource recovery rates.

[0004] Pyrometallurgical processes were among the earliest to be industrialized. The core of this method involves incinerating the battery at temperatures exceeding 1200 degrees Celsius to decompose organic matter and enrich metallic components into alloys or transfer them into the slag in a molten state. While this method has a large processing capacity, it suffers from significant drawbacks: First, it consumes extremely high amounts of energy, resulting in enormous carbon emissions that contradict the principles of green recycling; second, at high temperatures, lithium enters the slag in the form of silicates, making effective recovery difficult, with actual lithium recovery rates often below 50%, leading to a severe waste of this most valuable resource; finally, the incineration process generates large amounts of harmful waste gases containing dioxins and fluorides, posing serious secondary pollution control challenges.

[0005] Hydrometallurgical processes are currently the most widely used mainstream technology. They typically dissolve valuable metal ions from cathode materials into a solution using strong inorganic acids (such as sulfuric acid and hydrochloric acid) and chemical reducing agents (such as hydrogen peroxide) at relatively low temperatures. The ions are then separated and purified one by one through complex solvent extraction and chemical precipitation steps. While hydrometallurgical processes offer high metal recovery rates and purity, they still face several challenges: First, the entire process is lengthy and complex, involving multiple stages of extraction and back-extraction, resulting in high equipment investment and operating costs. Second, the extensive use of strong acids and organic extractants can generate tens of tons of high-salinity, difficult-to-treat acidic wastewater and organic waste liquid for every ton of cathode material processed, leading to enormous environmental remediation costs. Third, separating transition metals with similar chemical properties, such as nickel, cobalt, and manganese, requires the introduction of various additives, which can easily cause cross-contamination, affecting the purity of the final product. Furthermore, lithium recovery is usually placed at the end of the process, resulting in low efficiency.

[0006] To overcome the drawbacks of traditional metallurgical methods, direct regeneration technology has emerged. This technology does not aim to completely decompose the cathode material into metal salts, but rather to restore its electrochemical performance through "lithium replenishment" and structural repair, allowing it to be directly returned to the battery production line. This method is conceptually advanced and can maximize the preservation of the material's added value. However, its industrialization faces an extremely stringent prerequisite: near-perfect separation of the cathode active material from the aluminum foil current collector and polyvinylidene fluoride (PVDF) binder is essential. Any residual aluminum or binder degradation products will become "impurities," severely impairing the cycle life and safety performance of the regenerated cathode material. Existing pre-separation processes (such as organic solvent dissolution and pyrolysis) themselves require complex steps, increasing energy consumption and cost, and causing wear and structural damage to the cathode material itself during separation. This contradicts the high efficiency and low-loss principle of "direct regeneration."

[0007] In recent years, deep eutectic solvent (DES) technology, as a green branch of hydrometallurgy, has received widespread attention. This type of solvent system, composed of hydrogen bond acceptors such as choline chloride and hydrogen bond donors such as organic acids and polyols, is considered a viable alternative to traditional strong acids for environmentally friendly leaching. It boasts advantages such as high designability, environmental friendliness, and recyclability, and has shown potential in the field of metal recycling in recent years. However, existing DES systems still face the following problems when recycling ternary cathode materials: 1. Reaction Kinetics and Energy Efficiency Bottlenecks: Existing DES leaching systems often require long reaction times and high reaction temperatures to achieve high leaching rates. This not only increases process energy consumption and time costs but also limits throughput. The fundamental reason lies in the high viscosity of the DES system, which leads to large mass transfer resistance between reactants and products, thus limiting the rate of interfacial chemical reactions.

[0008] 2. The Challenge of Selective Separation of Complex Components: Decommissioned ternary cathode materials (such as NCM) are composite oxides of multiple metals, including lithium, nickel, cobalt, and manganese. These transition metal ions have similar properties and readily form eutectic systems in the leachate. Achieving high-purity and highly selective separation is the ultimate key and major challenge of the recovery process. Traditional methods rely on introducing multiple chemical precipitants or performing multi-stage solvent extraction, which is cumbersome and generates new pollution. How to utilize the inherent tunability of DES to achieve preferential lithium extraction and precise separation of transition metals with minimal or no external reagents is one of the core challenges currently being researched.

[0009] 3. Mass Transfer Limitations and High Viscosity Challenges: Degraded esters (DES) are typically formed by strong interactions between hydrogen bond donors and acceptors, resulting in a dense internal hydrogen bond network and high overall viscosity. High viscosity not only significantly reduces the diffusion rate of the solute in the solvent but also weakens the mass transfer efficiency at the solid-liquid interface, thus limiting the leaching kinetics of metals in degraded ternary cathode materials. In actual leaching processes, the reaction often exhibits a rapid initial reaction rate followed by a slow phase, making it difficult to achieve high leaching rates in a short time. Traditional control methods often rely on increasing temperature or introducing diluents to reduce system viscosity, but this may weaken the complexing ability of DES or alter its structural properties, affecting leaching selectivity and stability. Therefore, how to achieve synergistic optimization of low viscosity and high mass transfer performance through molecular structure design or system control while maintaining the excellent solubility and selectivity characteristics of DES is one of the key bottlenecks currently facing the application of DES in the battery recycling field. 4. Process Integration and Industrialization Barriers: An ideal recycling process should aim for the shortest possible flow and complete resource recycling. Currently, most research focuses on the single "leaching" stage, failing to effectively couple multiple stages such as the efficient separation of cathode materials from current collectors / binders, the selective leaching of valuable metals, and the recycling of the leaching agent (DES). For example, incomplete pre-separation can contaminate subsequent recycled materials; and the performance degradation and recycling issues caused by changes in the viscosity and composition of DES after use also limit its economic feasibility.

[0010] In summary, developing a low-viscosity, high-efficiency, highly selective, and environmentally friendly DES system can achieve efficient leaching and recovery of valuable metals from retired ternary lithium battery cathode materials, which has significant industrial application value. Furthermore, this process can improve economic and environmental benefits, reduce resource waste and environmental pollution, and achieve efficient recycling of materials. Summary of the Invention

[0011] The purpose of this invention is to provide a leaching method for retired ternary lithium battery cathode materials based on a choline chloride-levulinic acid eutectic solvent. Through a low-viscosity and high-reducibility DES system, lithium, nickel, cobalt and manganese in waste cathode materials can be efficiently leached under mild conditions.

[0012] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A leaching method for retired ternary lithium battery cathode materials based on a choline chloride-levulinic acid eutectic solvent, the method comprising the following steps: 1) The positive electrode powder is separated from the retired ternary lithium battery after disassembly and discharge; 2) Choline chloride and levulinic acid are mixed and used as a eutectic solvent, DES; 3) Mix the positive electrode powder with DES and stir to obtain the leachate.

[0013] The core technical idea of ​​this invention is to create a highly efficient synergistic reaction system that integrates interface stripping, reduction leaching and in-situ complexation by designing a low eutectic solvent with a "proton-electron-ligand" triple supply function. This will transform the traditional multi-step, highly polluting and complex recycling process into a one-step or two-step green, efficient and integrated process, ultimately achieving efficient and low-carbon recycling of valuable metal resources from retired lithium batteries.

[0014] In step 2), the molar ratio of choline chloride to acetylpropionic acid is 1:2-6.

[0015] Preferably, the molar ratio of choline chloride to levulinic acid is 1:2-3. By optimizing the molar ratio, the leaching rates of lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) can be significantly improved.

[0016] In step 3), the leaching time is 2-12 hours. Preferably, the leaching time is 6-12 hours. This invention improves the leaching rate of lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) by adjusting the leaching time.

[0017] In step 3), the leaching temperature is 120-140℃. Under these conditions, high leaching rates of lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) can be achieved.

[0018] In step 3), the solid-liquid ratio of the positive electrode powder mixed with DES is 10-20 g / L. Under these conditions, high leaching rates of lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) can be achieved.

[0019] The method includes post-treatment of the leachate to separate and recover Li, Ni, Co, and Mn.

[0020] The method further includes diluting the leachate with water, precipitation, extraction, or electrodeposition to achieve selective recovery of valuable metals. Specifically: Extractant was added to the leachate, and multi-stage countercurrent extraction was performed in the pH range of 1.5-3.0 to obtain an oil phase loaded with Ni, Co, and Mn and a DES phase loaded with Li. After clarification and separation of the oil phase, back-extraction was performed using a dilute sulfuric acid solution with a concentration of 0.5-2.0 mol / L to transfer Ni, Co, and Mn to the aqueous phase, and the pH was adjusted to 5.0-8.0. A precipitant was added to obtain Ni precipitate. The pH was then adjusted to 3.0-4.5, and Mn was extracted using an extractant to obtain a manganese-loaded organic phase, which was then back-extracted with dilute sulfuric acid to obtain manganese salt. The aqueous phase after manganese extraction was then extracted with an extractant at a pH range of 4.5-6.0 to extract cobalt. The cobalt-loaded organic phase was also back-extracted with dilute acid to obtain cobalt salt. Controlling the pH of the DES phase to neutral or weakly alkaline, sodium phosphate (Na3PO4) solution is added under heating conditions, causing lithium ions to precipitate out as lithium phosphate.

[0021] The green leaching and recycling method for retired lithium-ion battery cathode materials based on a eutectic solvent of choline chloride and levulinic acid provided by this invention has a series of significant and verifiable advantages compared to traditional pyrometallurgical, hydrometallurgical, and existing direct regeneration or DES leaching technologies. These beneficial effects are reflected in multiple dimensions such as technical performance, economic benefits, environmental friendliness, and process universality. Compared with the prior art, this invention has the following beneficial effects: (1) The choline chloride-levulinic acid DES system (hydrogen bond donor and hydrogen bond acceptor synthesized eutectic solvent) designed in this invention can achieve efficient extraction of key valuable metals in ternary cathode materials (NCM523) under optimized mild conditions; for example, the leaching rates of lithium (Li), nickel (Ni), cobalt (Co) and manganese (Mn) can reach 96.19%, 97.39%, 98.27% and 93.41%, respectively. This efficiency is comparable to or even better than that of traditional wet processes that require strong acids and additional reducing agents, but the process is greener and milder.

[0022] (2) This invention overcomes the bottleneck of existing DES technology which generally requires high temperature and long reaction time: by selecting and optimizing the ratio of low viscosity components (such as levulinic acid), the mass transfer efficiency of the system is greatly improved, so that efficient leaching can be completed at medium and low temperature (100-140℃) and in a short time (2-12 hours); compared with the energy consumption of pyrometallurgy exceeding 1200℃ and the reaction requirement of some DES systems up to 24 hours, the energy consumption and time cost of this invention are significantly reduced.

[0023] (3) The chloride ions (Cl) in the DES system used in this invention - It forms stable complexes with transition metal ions such as cobalt and manganese (e.g., [CoCl4]). 2-This process not only promotes leaching but also allows different metals to exist in differentiated forms in the leachate. This lays an ideal foundation for subsequent stepwise extraction methods to separate different metals, which is beneficial for obtaining high-purity single-metal products and enhancing the value of resource-based products.

[0024] (4) The main components of the DES used in this invention are choline chloride and levulinic acid, which are inexpensive and readily available. More importantly, the system does not require additional purchase and use of expensive strong acids (such as sulfuric acid and hydrochloric acid), strong oxidants (such as hydrogen peroxide) and organic extractants, which significantly reduces the cost of direct chemical reagents per treatment from the source.

[0025] (5) The DES system used in this invention has low viscosity and good stability, which is beneficial to heat and mass transfer during leaching and subsequent separation processes. It can also be efficiently recovered and regenerated by simple distillation, membrane separation and other methods. The recovered DES can be recycled multiple times for the leaching process, further reducing solvent costs and making the whole process more economically sustainable and competitive. Attached Figure Description

[0026] Figure 1 A detailed flowchart of a green leaching and recycling method for retired ternary lithium battery cathode materials based on a choline chloride-levulinic acid eutectic solvent is provided for the embodiments. Figure 2 This is a comparison chart of the leaching rates of valuable metals from waste ternary lithium batteries under different DES systems obtained in Example 1. Figure 3 This is a viscosity comparison chart of different DES systems obtained in Example 1; Figure 4 The curves showing the changes in the leaching rate of valuable metals from waste ternary lithium batteries at different times obtained in Example 2; Figure 5 The curves showing the leaching rate of valuable metals from waste ternary lithium batteries at different temperatures obtained in Example 3 are shown. Figure 6 The difference obtained in Example 4 is the change curve of the leaching rate of valuable metals from waste ternary lithium batteries under the molar ratio of DES components; Figure 7 The curves showing the variation of the leaching rate of valuable metals from waste ternary lithium batteries under different solid-liquid ratios obtained in Example 5 are shown. Detailed Implementation

[0027] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1 like Figure 1 As shown, the green leaching method for retired ternary lithium battery cathode materials provided in this embodiment specifically includes the following steps: (1) Discharge and disassembly: The waste lithium battery was discharged using a charge-discharge tester at a current of 1A until the voltage dropped to 2V. Then, the battery was placed in a glove box for disassembly, the positive electrode material strip was peeled off, and the positive electrode strip was rinsed twice with dimethyl carbonate (purity >99%) to remove residual electrolyte on the surface. N-methylpyrrolidone (NMP) was used to dissolve the polyvinylidene fluoride (PVDF) binder, and the mixture was stirred or ultrasonically treated at 80°C to 100°C for 2 to 6 hours. The mixture was initially separated by passing it through a stainless steel sieve, and the remaining suspension was centrifuged and dried to obtain positive electrode material powder.

[0029] (2) Synthesis of eutectic solvent: Choline chloride (ChCl) was mixed with ethylene glycol (EG), urea, and levulinic acid (LevA) in a 1:2 molar ratio, and betaine hydrochloride (BeCl) was mixed with levulinic acid (LevA) in a 1:2 molar ratio. The mixtures were stirred at 80°C until a uniform and transparent liquid was formed to obtain the eutectic solvent. The viscosity of each eutectic solvent system was obtained by viscosity analysis using a rotational viscometer. (3) Solvent leaching reaction: Weigh the positive electrode powder treated in step (1), add it to the eutectic solvent synthesized in step (2) at a concentration of 10 g / L, pour it into a reaction vessel, and react at 120°C with stirring for 6 h. After the reaction is completed, cool to room temperature, filter and separate the leachate and residual solids; (4) Metal recovery: Add the extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507) to the DES leaching solution described in step (3), and perform multi-stage countercurrent extraction within a pH range of 1.5-3.0. Ni 2+ Co 2+ Mn 2+ Transition metal ions are extracted into the oil phase, while Li... + The Ni, Co, and Mn are largely retained in the DES phase. After clarification and separation, the P507 organic phase loaded with Ni, Co, and Mn is back-extracted using a 0.5-2.0 mol / L dilute sulfuric acid solution to remove most of the Ni. 2+ Co 2+ Mn 2+ The nitrogen was efficiently transferred to the aqueous phase. The pH of the solution was then adjusted to 5.0-8.0, and under heating and stirring, an ethanol or alkaline solution of dimethylglyoxime (DMG) was slowly added. The precipitate of Ni was obtained by filtration. The pH of the solution was then adjusted to 3.0-4.5, and Mn was extracted using di(2-ethylhexyl) phosphate (P204). 2+The manganese-loaded organic phase was back-extracted with dilute sulfuric acid to obtain a pure manganese salt solution. The aqueous phase after manganese extraction was then used to extract cobalt using heptamethylphosphonate monoheptyl ester (C272) at a pH range of 4.5-6.0. The cobalt-loaded organic phase was also back-extracted with dilute acid to obtain a high-purity cobalt salt solution. The pH of the lithium-rich DES solution was controlled to neutral or weakly alkaline, and sodium phosphate (Na3PO4) solution was added at 80°C. Lithium ions precipitated as lithium phosphate (Li3PO4). After filtration, washing, and drying, pure lithium phosphate was obtained.

[0030] (5) Testing and characterization: The product obtained in step (4) was analyzed by inductively coupled plasma mass spectrometry (ICP) to calculate the leaching rates of Li, Ni, Gu and Mn.

[0031] Example 2 like Figure 1 As shown, the green leaching method for retired ternary lithium battery cathode materials provided in this embodiment specifically includes the following steps: (1) Discharge and disassembly: The waste lithium battery was discharged using a charge-discharge tester at a current of 1A until the voltage dropped to 2V. Then, the battery was placed in a glove box for disassembly, the positive electrode material strip was peeled off, and the positive electrode strip was rinsed twice with dimethyl carbonate (purity >99%) to remove residual electrolyte on the surface. N-methylpyrrolidone (NMP) was used to dissolve the polyvinylidene fluoride (PVDF) binder, and the mixture was stirred or ultrasonically treated at 80°C to 100°C for 2 to 6 hours. The mixture was initially separated by passing it through a stainless steel sieve, and the remaining suspension was centrifuged and dried to obtain positive electrode material powder.

[0032] (2) Synthesis of eutectic solvent: Choline chloride and ethylene glycol levulinic acid were mixed at a molar ratio of 1:2 and stirred at 80°C until a uniform transparent liquid was formed to obtain the eutectic solvent; (3) Solvent leaching reaction: Weigh the positive electrode powder treated in step (1), add it to the eutectic solvent synthesized in step (2) at a concentration of 10 g / L, pour it into a reaction vessel, and react at 120 °C with stirring for 2-12 h. After the reaction is completed, cool to room temperature, filter and separate the leachate and residual solids; (4) Metal recovery: Add the extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507) to the DES leaching solution described in step (3), and perform multi-stage countercurrent extraction within a pH range of 1.5-3.0. Ni 2+ Co 2+ Mn 2+ Transition metal ions are extracted into the oil phase, while Li... +The Ni, Co, and Mn are largely retained in the DES phase. After clarification and separation, the P507 organic phase loaded with Ni, Co, and Mn is back-extracted using a 0.5-2.0 mol / L dilute sulfuric acid solution to remove most of the Ni. 2+ Co 2+ Mn 2+ The nitrogen was efficiently transferred to the aqueous phase. The pH of the solution was then adjusted to 5.0-8.0, and under heating and stirring, an ethanol or alkaline solution of dimethylglyoxime (DMG) was slowly added. The precipitate of Ni was obtained by filtration. The pH of the solution was then adjusted to 3.0-4.5, and Mn was extracted using di(2-ethylhexyl) phosphate (P204). 2+ The manganese-loaded organic phase was back-extracted with dilute sulfuric acid to obtain a pure manganese salt solution. The aqueous phase after manganese extraction was then used to extract cobalt using heptamethylphosphonate monoheptyl ester (C272) at a pH range of 4.5-6.0. The cobalt-loaded organic phase was also back-extracted with dilute acid to obtain a high-purity cobalt salt solution. The pH of the lithium-rich DES solution was controlled to neutral or weakly alkaline, and sodium phosphate (Na3PO4) solution was added at 80°C. Lithium ions precipitated as lithium phosphate (Li3PO4). After filtration, washing, and drying, pure lithium phosphate was obtained.

[0033] (5) Testing and characterization: The product obtained in step (4) was analyzed by inductively coupled plasma mass spectrometry (ICP) to calculate the leaching rates of Li, Ni, Gu and Mn.

[0034] (6) Eutectic solvent regeneration: The eutectic solvent after metal recovery in step (4) is placed in a reactor and heated at 100°C to remove the water, thus obtaining regenerated eutectic solvent (r-DES).

[0035] Example 3 like Figure 1 As shown, the green leaching method for retired ternary lithium battery cathode materials provided in this embodiment specifically includes the following steps: (1) Discharge and disassembly: The waste lithium battery was discharged using a charge-discharge tester at a current of 1A until the voltage dropped to 2V. Then, the battery was placed in a glove box for disassembly, the positive electrode material strip was peeled off, and the positive electrode strip was rinsed twice with dimethyl carbonate (purity >99%) to remove residual electrolyte on the surface. N-methylpyrrolidone (NMP) was used to dissolve the polyvinylidene fluoride (PVDF) binder, and the mixture was stirred or ultrasonically treated at 80°C to 100°C for 2 to 6 hours. The mixture was initially separated by passing it through a stainless steel sieve, and the remaining suspension was centrifuged and dried to obtain positive electrode material powder.

[0036] (2) Synthesis of eutectic solvent: Choline chloride and levulinic acid are mixed at a molar ratio of 1:2 and stirred at 80°C until a uniform transparent liquid is formed to obtain the eutectic solvent; (3) Solvent leaching reaction: Weigh the positive electrode powder treated in step (1), add it to the eutectic solvent synthesized in step (2) at a concentration of 10 g / L, pour it into a reaction vessel, and react for 6 h at 60~140℃ with stirring. After the reaction is completed, cool to room temperature, filter and separate the leachate and residual solids; (4) Metal recovery: Add the extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507) to the DES leaching solution described in step (3), and perform multi-stage countercurrent extraction within a pH range of 1.5-3.0. Ni 2+ Co 2+ Mn 2+ Transition metal ions are extracted into the oil phase, while Li... + The Ni, Co, and Mn are largely retained in the DES phase. After clarification and separation, the P507 organic phase loaded with Ni, Co, and Mn is back-extracted using a 0.5-2.0 mol / L dilute sulfuric acid solution to remove most of the Ni. 2+ Co 2+ Mn 2+ The nitrogen was efficiently transferred to the aqueous phase. The pH of the solution was then adjusted to 5.0-8.0, and under heating and stirring, an ethanol or alkaline solution of dimethylglyoxime (DMG) was slowly added. The precipitate of Ni was obtained by filtration. The pH of the solution was then adjusted to 3.0-4.5, and Mn was extracted using di(2-ethylhexyl) phosphate (P204). 2+ The manganese-loaded organic phase was back-extracted with dilute sulfuric acid to obtain a pure manganese salt solution. The aqueous phase after manganese extraction was then used to extract cobalt using heptamethylphosphonate monoheptyl ester (C272) at a pH range of 4.5-6.0. The cobalt-loaded organic phase was also back-extracted with dilute acid to obtain a high-purity cobalt salt solution. The pH of the lithium-rich DES solution was controlled to neutral or weakly alkaline, and sodium phosphate (Na3PO4) solution was added at 80°C. Lithium ions precipitated as lithium phosphate (Li3PO4). After filtration, washing, and drying, pure lithium phosphate was obtained.

[0037] (5) Testing and characterization: The product obtained in step (4) was analyzed by inductively coupled plasma mass spectrometry (ICP) to calculate the leaching rates of Li, Ni, Gu and Mn.

[0038] (6) Eutectic solvent regeneration: The eutectic solvent after metal recovery in step (4) is placed in a reactor and heated at 100°C to remove the water, thus obtaining regenerated eutectic solvent (r-DES).

[0039] Example 4 like Figure 1 As shown, the green leaching method for retired ternary lithium battery cathode materials provided in this embodiment specifically includes the following steps: (1) Discharge and disassembly: The waste lithium battery was discharged using a charge-discharge tester at a current of 1A until the voltage dropped to 2V. Then, the battery was placed in a glove box for disassembly, the positive electrode material strip was peeled off, and the positive electrode strip was rinsed twice with dimethyl carbonate (purity >99%) to remove residual electrolyte on the surface. N-methylpyrrolidone (NMP) was used to dissolve the polyvinylidene fluoride (PVDF) binder, and the mixture was stirred or ultrasonically treated at 80°C to 100°C for 2 to 6 hours. The mixture was initially separated by passing it through a stainless steel sieve, and the remaining suspension was centrifuged and dried to obtain positive electrode material powder.

[0040] (2) Synthesis of eutectic solvent: Choline chloride and levulinic acid are mixed in a molar ratio of 1:2 to 1:6 and stirred at 80°C until a uniform transparent liquid is formed to obtain the eutectic solvent; (3) Solvent leaching reaction: Weigh the positive electrode powder treated in step (1), add it to the eutectic solvent synthesized in step (2) at a concentration of 10 g / L, pour it into a reaction vessel, and react at 120°C with stirring for 6 h. After the reaction is completed, cool to room temperature, filter and separate the leachate and residual solids; (4) Metal recovery: Add the extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507) to the DES leaching solution described in step (3), and perform multi-stage countercurrent extraction within a pH range of 1.5-3.0. Ni 2+ Co 2+ Mn 2+ Transition metal ions are extracted into the oil phase, while Li... + The Ni, Co, and Mn are largely retained in the DES phase. After clarification and separation, the P507 organic phase loaded with Ni, Co, and Mn is back-extracted using a 0.5-2.0 mol / L dilute sulfuric acid solution to remove most of the Ni. 2+ Co 2+ Mn 2+ The nitrogen was efficiently transferred to the aqueous phase. The pH of the solution was then adjusted to 5.0-8.0, and under heating and stirring, an ethanol or alkaline solution of dimethylglyoxime (DMG) was slowly added. The precipitate of Ni was obtained by filtration. The pH of the solution was then adjusted to 3.0-4.5, and Mn was extracted using di(2-ethylhexyl) phosphate (P204). 2+ The manganese-loaded organic phase was back-extracted with dilute sulfuric acid to obtain a pure manganese salt solution. The aqueous phase after manganese extraction was then used to extract cobalt using heptamethylphosphonate monoheptyl ester (C272) at a pH range of 4.5-6.0. The cobalt-loaded organic phase was also back-extracted with dilute acid to obtain a high-purity cobalt salt solution. The pH of the lithium-rich DES solution was controlled to neutral or weakly alkaline, and sodium phosphate (Na3PO4) solution was added at 80°C. Lithium ions precipitated as lithium phosphate (Li3PO4). After filtration, washing, and drying, pure lithium phosphate was obtained.

[0041] (5) Testing and characterization: The product obtained in step (4) was analyzed by inductively coupled plasma mass spectrometry (ICP) to calculate the leaching rates of Li, Ni, Gu and Mn.

[0042] (6) Eutectic solvent regeneration: The eutectic solvent after metal recovery in step (4) is placed in a reactor and heated at 100°C to remove the water, thus obtaining regenerated eutectic solvent (r-DES).

[0043] Example 5 like Figure 1 As shown, the green leaching method for retired ternary lithium battery cathode materials provided in this embodiment specifically includes the following steps: (1) Discharge and disassembly: The waste lithium battery was discharged using a charge-discharge tester at a current of 1A until the voltage dropped to 2V. Then, the battery was placed in a glove box for disassembly, the positive electrode material strip was peeled off, and the positive electrode strip was rinsed twice with dimethyl carbonate (purity >99%) to remove residual electrolyte on the surface. N-methylpyrrolidone (NMP) was used to dissolve the polyvinylidene fluoride (PVDF) binder, and the mixture was stirred or ultrasonically treated at 80°C to 100°C for 2 to 6 hours. The mixture was initially separated by passing it through a stainless steel sieve, and the remaining suspension was centrifuged and dried to obtain positive electrode material powder.

[0044] (2) Synthesis of eutectic solvent: Choline chloride and levulinic acid are mixed at a molar ratio of 1:2 and stirred at 80°C until a uniform transparent liquid is formed to obtain the eutectic solvent; (3) Solvent leaching reaction: Weigh the positive electrode powder treated in step (1), add it to the eutectic solvent synthesized in step (2) at a concentration of 10~50 g / L, pour it into a reaction vessel, and react at 120℃ with stirring for 6 h. After the reaction is completed, cool to room temperature, filter and separate the leachate and residual solids; (4) Metal recovery: Add the extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507) to the DES leaching solution described in step (3), and perform multi-stage countercurrent extraction within a pH range of 1.5-3.0. Ni 2+ Co 2+ Mn 2+ Transition metal ions are extracted into the oil phase, while Li... + The Ni, Co, and Mn are largely retained in the DES phase. After clarification and separation, the P507 organic phase loaded with Ni, Co, and Mn is back-extracted using a 0.5-2.0 mol / L dilute sulfuric acid solution to remove most of the Ni. 2+ Co 2+ Mn 2+The nitrogen was efficiently transferred to the aqueous phase. The pH of the solution was then adjusted to 5.0-8.0, and under heating and stirring, an ethanol or alkaline solution of dimethylglyoxime (DMG) was slowly added. The precipitate of Ni was obtained by filtration. The pH of the solution was then adjusted to 3.0-4.5, and Mn was extracted using di(2-ethylhexyl) phosphate (P204). 2+ The manganese-loaded organic phase was back-extracted with dilute sulfuric acid to obtain a pure manganese salt solution. The aqueous phase after manganese extraction was then used to extract cobalt using heptamethylphosphonate monoheptyl ester (C272) at a pH range of 4.5-6.0. The cobalt-loaded organic phase was also back-extracted with dilute acid to obtain a high-purity cobalt salt solution. The pH of the lithium-rich DES solution was controlled to neutral or weakly alkaline, and sodium phosphate (Na3PO4) solution was added at 80°C. Lithium ions precipitated as lithium phosphate (Li3PO4). After filtration, washing, and drying, pure lithium phosphate was obtained.

[0045] (5) Testing and characterization: The product obtained in step (4) was analyzed by inductively coupled plasma mass spectrometry (ICP) to calculate the leaching rates of Li, Ni, Gu and Mn.

[0046] (6) Eutectic solvent regeneration: The eutectic solvent after metal recovery in step (4) is placed in a reactor and heated at 100°C to remove the water, thus obtaining regenerated eutectic solvent (r-DES).

[0047] Figures 2 to 7 Examples 1 through 5 respectively demonstrate the leaching rates of Li, Ni, Gu, and Mn from the metal products recovered from the leachate under different conditions, calculated by inductively coupled plasma mass spectrometry (ICP). Data shows that under optimized conditions, the leaching rates of all four metals can reach high levels. This indicates that the green leaching and recovery method for retired ternary lithium battery cathode materials used in this invention can effectively extract metal materials from retired lithium battery cathode materials, fully verifying the effectiveness and practicality of the leaching technology.

[0048] The above embodiments are only used to explain the inventive concept of the present invention, and are not intended to limit the protection of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical and methodological essence of the present invention shall still fall within the scope of the technical and methodological solutions of the present invention.

Claims

1. A leaching method for retired ternary lithium battery cathode materials based on a choline chloride-levulinic acid eutectic solvent, characterized in that, The method includes the following steps: 1) The positive electrode powder is separated from the retired ternary lithium battery after disassembly and discharge; 2) Choline chloride and levulinic acid are mixed and used as a eutectic solvent, DES; 3) Mix the positive electrode powder with DES and stir to obtain the leachate.

2. The method according to claim 1, characterized in that, In step 2), the molar ratio of choline chloride to acetylpropionic acid is 1:2-6.

3. The method according to claim 2, characterized in that, The molar ratio of choline chloride to levulinic acid is 1:2-3.

4. The method according to claim 1, characterized in that, In step 3), the leaching time is 2-12 hours.

5. The method according to claim 4, characterized in that, In step 3), the leaching time is 6-12 hours.

6. The method according to claim 1, characterized in that, In step 3), the leaching temperature is 120-140℃.

7. The method according to claim 1, characterized in that, In step 3), the solid-liquid ratio of the positive electrode powder and DES after mixing is 10-20 g / L.

8. The method according to claim 1, characterized in that, The method includes post-treatment of the leachate to separate and recover Li, Ni, Co, and Mn.

9. The method according to claim 8, characterized in that, The separation and recovery method includes: Extractant was added to the leachate, and multi-stage countercurrent extraction was performed in the pH range of 1.5-3.0 to obtain an oil phase loaded with Ni, Co, and Mn and a DES phase loaded with Li. After clarification and separation of the oil phase, back-extraction was performed using a dilute sulfuric acid solution with a concentration of 0.5-2.0 mol / L to transfer Ni, Co, and Mn to the aqueous phase, and the pH was adjusted to 5.0-8.

0. A precipitant was added to obtain Ni precipitate. The pH was then adjusted to 3.0-4.5, and Mn was extracted using an extractant to obtain a manganese-loaded organic phase, which was then back-extracted with dilute sulfuric acid to obtain manganese salt. The aqueous phase after manganese extraction was then extracted with an extractant at a pH range of 4.5-6.0 to extract cobalt. The cobalt-loaded organic phase was also back-extracted with dilute acid to obtain cobalt salt. Controlling the pH of the DES phase to neutral or weakly alkaline, sodium phosphate (Na3PO4) solution is added under heating conditions, causing lithium ions to precipitate out as lithium phosphate.

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