Recycling valuable metals from spent lithium-ion battery cathode materials based on microwave-assisted hydrogen reduction followed by grind-leaching and magnetic separation

The efficient and clean recycling of spent lithium-ion batteries (LIBs) is essential for resource conservation and environmental protection. This work proposes a facile and clean process for recovering of valuable metals based on microwave-assisted hydrogen reduction of spent cathode materials followed by grind-leaching and magnetic separation. After hydrogen reduction, the spent cathode material was transformed into water-soluble LiOH, Ni–Co alloy and MnO, wherein LiOH was preferentially dissolved by grind-leaching, while Ni–Co alloy was recycled by magnetic separation. Compared with the traditional carbothermal reduction, lithium was converted into LiOH instead of Li2CO3, and the Li leaching efficiency was significantly improved. Ni–Co alloy can be separated with MnO via simple magnetic separation without acid leaching. Effects of roasting (roasting temperature and time) and grind-leaching (grinding time and liquid-to-solid ratio) parameters on the recoveries of Li, Ni, Co and Mn were investigated. Under the conditions of roasting temperature of 973 K, roasting time of 60 min, grinding time of 30 min and liquid-to-solid ratio of 5 mL/g, the grind-leaching efficiency of Li was 98.17%. Ni and Co were enriched in the magnetic material with recoveries of 99.71% and 98.52%, respectively. Moreover, the coupling mechanism between Li dissolution and particle dissociation during the grind-leaching process was revealed.