A Sustainable Leaching-Separation-Regeneration Strategy for Cathode Recovery Using a Low-Viscosity Deep Eutectic Solvent

Efficient recycling of spent lithium-ion batteries (LIBs) is crucial for resource sustainability and environmental protection. However, existing hydrometallurgical recycling processes generally rely on strong acids and large amounts of chemicals, which easily cause secondary pollution. Therefore, this study developed a green, efficient, and low-viscosity deep eutectic solvent (DES) system for the selective recovery of valuable metals from ternary cathode materials (NCM). A novel DES based on tetramethylammonium chloride-aconitic acid (TMA–AC) was designed and synthesized. The leaching of NCM333 materials was carried out under mild conditions at 90 °C, and ethanol was introduced as a precipitant to realize the selective separation of metal ions and the recycling of DES. Experimental results showed that the leaching rates of Li, Ni, Co, and Mn all exceeded 99%. By regulating the metal coordination environment with ethanol, efficient homogeneous coprecipitation of Ni, Co, and Mn and the separation of Li were achieved, and the DES could be regenerated and reused after simple treatment. This work confirms that the TMA–AC-based DES system is a highly promising green leaching reagent, and the constructed “leaching-separation-regeneration” integrated process provides a new strategy for the clean and low-cost recycling of spent lithium-ion batteries, with important industrial application prospects.