Sustainable Recovery of Critical Metals from Spent Lithium-Ion Batteries Using Deep Eutectic Solvents

The surging demand for lithium-ion batteries (LIBs) has intensified the need for sustainable recovery of critical metals such as lithium, manganese, cobalt, and nickel from spent cathodes. While conventional hydrometallurgical and pyrometallurgical methods are widely used, they involve high energy consumption, hazardous waste generation, and complex processing steps, underscoring the urgency of developing eco-friendly alternatives. This study presents a novel, water-enhanced deep eutectic solvent (DES) system composed of choline chloride and D-glucose for the efficient leaching of valuable metals from spent LiMn-based battery cathodes. The DES was synthesized under mild conditions and applied to dissolve cathode powder, with leaching performance optimized by varying temperature and duration. Under optimal conditions (100 °C, 24 h), exceptional recovery efficiencies were achieved: 98.9% for lithium, 98.4% for manganese, and 71.7% for nickel. Material characterization using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and inductively coupled plasma mass spectrometer (ICP-MS) confirm effective phase dissolution and metal release. Although this DES system requires relatively higher temperature and longer reaction time compared to traditional acid leaching, it offers clear advantages in terms of non-toxicity, biodegradability, and elimination of strong oxidizing agents. These results demonstrate the potential of water-enhanced choline chloride–glucose DES as a green alternative for future development in sustainable battery recycling, supporting circular economy objectives.