Low-viscosity acidic deep eutectic solvent for extraction of valuable metals from spent NCM

In this study, a low-viscosity and reducing acidic deep eutectic solvent is synthesized from ethylene glycol and malonic acid for leaching valuable metals from spent lithium-ion battery cathode materials. The influence of various experimental parameters on the efficiency of metal leaching is systematically investigated. Under optimal conditions, the leaching efficiency of Li, Ni, Co, and Mn is ca. 100%. In addition, the mechanism and leaching kinetics of the system are investigated. The transition metal ions are reduced to a lower valence state in the presence of the tested deep eutectic solvent; resulting in efficient leaching, which is controlled by the chemical reaction. Separating Li+ from transition metal ions is then achieved by recovering the transition metal ions from the leaching solution by co-precipitation. The co-precipitated products are used as precursors for preparing cathode materials and producing NCM523 coin cells with good electrochemical performance.