Selective lithium extraction by chemical vapor reduction from spent lithium-ion batteries cathode materials under carbon dioxide atmosphere

The booming new energy industry has led to the rapid growth of electric vehicles, resulting in the generation of large quantities of spent lithium-ion batteries (LIBs). The abundant lithium resources contained therein urgently need to be recycled for its significant strategic value. Here, a new chemical vapor reduction (CVR) approach is proposed for the leaching of lithium from the ectopic roasting of pyrite (FeS2) and spent LIBs cathode materials (SLCM) in CO2 atmosphere, achieving selective extraction of lithium and carbon neutral by consuming CO2. By systematically adjusting the pyrite and SLCM dosage, roasting temperature and time, it is possible to realize more than 97.7% lithium extraction without introducing any other metals into the leaching solution. The thermodynamic values of a series of reactions are calculated and their reaction trends are analyzed. The mechanism of the process has been studied in depth with thermodynamic analysis and density functional theory calculation as well as various ex-/in-situ testing methods. Namely, FeS2 decomposes volatile sulfur at high temperatures on the front-end, which reacts with CO2 to produce SO2, CO, enhancing the reduction process of high valence metals on the back end, thus allowing lithium to be extracted smoothly without residual reducing agent in transition metal (TM) residue. In addition, the proposed CVR method is evaluated from various perspectives including economic and environmental protection. The present work suggests a new idea of the combined pyro-hydrometallurgical process for spent cathode recycling, which is more efficient and cost effective as well as more environmentally friendly.