Holistic Investigation of the Inert Thermal Treatment of Industrially Shredded NMC 622 Lithium-Ion Batteries and Its Influence on Selective Lithium Recovery by Water Leaching

Abstract

The thermal treatment of lithium-ion batteries is an already industrially implemented process step in some recycling chains. It provides the advantages of controlled organic removal and conditioning of the black mass for further process steps, such as water-based early-stage lithium recovery. Therefore, a deep understanding of ongoing reactions and the influence of the process parameters on the reaction products is crucial. This study investigates the inert thermal treatment of an industrial end-of-life NMC 622 battery shredder in a 200 g scale regarding the influence of process parameters on the reaction products, separation of black mass, and its water leaching. Therefore, the off-gas produced during the thermal treatment was analyzed by FTIR, and afterwards, a sieve classification of the shredder was carried out. The separated black mass was further analyzed for residual organics by pyrolysis GC-MS and for its phase composition by XRD. A water leaching of the different thermally treated black masses was carried out for Li recovery. Occurring reactions during the thermal treatment process, such as the different stages of organic removal and reduction reactions in the active material, were derived based on the collected data. These reactions mainly affect the water-based Li recovery, which is related to Li2CO3 generation. The maximum pyrolysis temperature has the greatest effect on the Li recovery. After a treatment at 642 °C, 62.4% of Li was leached. Reactions of the co-elements F, P and Al with Li during the thermal treatment were identified as the limiting factors regarding Li recovery.