Thermal treatment process for the recovery of valuable metals from spent lithium-ion batteries

In this paper, a process based on reducing thermal treatment before acid leaching for the recovery of valuable materials from spent lithium-ion batteries is developed. The thermodynamic behavior of the active cathode materials is investigated through analyzing the gases evolved from the thermal treatment with a thermogravimetric–mass spectrometry (TG–MS) instrument. Scanning electron microscopy (SEM) with energy dispersive x-ray (EDX) spectroscopy analyses are also performed on the solid cathode and anode materials to determine their physicochemical changes from the thermal treatment. The results show that the thermal treatment significantly improves the clean separation of the active materials from the current collectors and the complete removal of the binder and carbonaceous conductor. It also alters the molecular structures of, and partially reduces the transition metals in, the active cathode materials, which increases the leaching efficiency of the transition metals in the subsequent leaching step. After thermal treatment, the leaching efficiency of nickel, cobalt and manganese from the active cathode materials has reached over 98%, 99% and 84%, respectively.