Selective Recovery of Lithium from Spent Lithium-Ion Batteries via Sulfite-Assisted Reduction Roasting

Green sustainable development has become a critical focus in the recycling of spent lithium-ion batteries. This study introduces a novel and efficient method for the selective extraction of lithium from cathode materials of spent lithium-ion batteries, operating at a significantly milder roasting temperature (650 °C). The process involves the homogeneous mixing of recovered cathode materials with sodium sulfite, followed by oxygen-free roasting and subsequent water leaching. By controlling the structural evolution of the products, the process achieves highly efficient lithium recovery. The phase transformations of the cathode materials are investigated by advanced characterization techniques during the reaction and elucidate the selective leaching mechanism: through precise control of sodium sulfite dosage and roasting temperature, nickel, cobalt, and manganese remained stable in the solid residue as low-valence oxides, notably preserving nickel’s original valence state, while lithium was converted to water-soluble sulfate, thereby achieving efficient selective leaching. Under optimized conditions, i.e., a sodium sulfite-to-cathode material molar ratio of 3:1, roasting time of 150 min, and roasting temperature of 650 °C, the cathode materials were predominantly transformed into LiNaSO₄ and other metal oxides. The roasting process, conducted under an inert atmosphere to prevent the formation of gaseous sulfur oxides, demonstrated environmental sustainability with negligible emissions, while the subsequent water leaching phase was performed under mild conditions, yielding an exceptional lithium extraction efficiency of 96%. Furthermore, Ni, Co, and Mn elements remained in the water leaching residue in the form of oxides, simplifying their subsequent recovery. The proposed process offers significant advantages of low energy consumption and environmental sustainability, thereby presenting a promising pathway for selective lithium extraction and resource recovery from spent lithium-ion batteries.