Green Deep Eutectic Solvents for Lithium-Ion Battery Cathode Black Powder Impurity Removal and Precious Metal Recovery

As the electric vehicle market grows rapidly and the number of used lithium-ion batteries (LIBs) continues to increase, it is important to recycle precious metals in used LIBs in a green way. Deep eutectic solvents (DESs), which are biodegradable and green solvents, have great potential for the recovery of precious metals from LIBs. In this paper, a method is proposed for extracting precious metals in the cathode black powder of LIBs while removing aluminum impurities, which can effectively avoid the pollution and high energy consumption of traditional hydrometallurgy. Based on a novel DES consisting of betaine hydrochloride and glycerol, we integrated the extraction and removal of impurities from LIBs into one step, which greatly simplified the recovery process. By adjusting the leaching parameters, the extraction rates of Li, Ni, Co, and Mn were 99.49%, 97.23%, 97.41%, and 99.72%, respectively. The leaching process is consistent with the chemical reaction process in the shrinking nucleus model, and the synergistic effect of strong coordination ability (Cl–), acidity (H+), and reduction ability (GIy) in the DES is the key to realize the high efficiency of leaching of valuable metals. Finally, transition metals were recovered as Ni1/3Co1/3Mn1/3(OH)2, and Li was also successfully recovered as lithium oxalate. This study provides a novel, efficient, and environmentally friendly method for the recovery of precious metals from the spent LIB cathode black powder.