Targeted metals extraction from spent LiNi_0.5Co_0.2Mn_0.3O₂ batteries via thermochemical-induced sulfation roasting: Thermodynamics & kinetics

To alleviate the energy crisis and control environmental pollution raised by spent lithium-ion batteries (LIBs), the development of efficient and economic methods for their recycling is crucial for sustainable development of new energy industry. Herein, a combined pyro - hydrometallurgical process was adopted for recovery of valuable metal elements for spent LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523). Different from conventional pyrometallurgical methods with high temperature and energy consumption, the NH₄HSO₄ roasting strategy works at 400 °C and achieves remarkable leaching efficiencies of Li, Co, Mn, and Ni achieved 97.5 %, 91.4 %, 91.3 %, and 95.50 %, respectively. Under the ideal conditions, abundant water-soluble metal-ammine-sulfates and metal-sulfates were revolved from NCM523. The process factors, including sulfation-roasting temperature, reagent mass ratio, roasting time, are intensively studied. Furthermore, a plausible reaction mechanism was deeply investigated with assistance of macro-micro scale, thermodynamic and kinetic analysis. Wherein, the Li of the NCM523 first react sufficiently with NH₄HSO₄ owing to higher thermodynamic/kinetic motivation at the primary stage during the sulfation-roasting procedure. Subsequently, the transition metal (Ni, Co, and Mn) from the lithium-depleted NCM523 would revolve to corresponding metal-ammine-sulfates or metal sulfates, and their sulfation-roasting kinetics conformed to the unreacted nuclear model. This study proposed an alternative green route of low energy consumption and acid-free procedure for recovering spent NCM batteries, which is conducive to industrial-scale recycling of waste LIBs in the future.