• Achieved 95% selective lithium dissolution with minimal co-leaching of Ni, Co, and Mn (<1%) using a novel acid-free sulphation roasting process.
• The process operates at a moderate temperature of 600°C with sodium bisulfate as a roasting reagent, offering a more sustainable alternative to traditional acid leaching.
• Mechanistic insights reveal that roasting collapses the NCM layered structure, converting lithium to LiNaSO4 and transition metals to Ni6MnO8 and MnCo2O4, enabling selective extraction.
• The method simplifies downstream purification, allowing direct production of Li2CO3 from the lithium-rich leach solution, potentially improving overall lithium recovery rates.