Mechanistic Insights Into Mineral-Assisted Sulfation Roasting for Selective Lithium Recovery

Although sulfation roasting shows great potential in the recycling of spent lithium-ion batteries, the reaction pathways and kinetic mechanisms in complex multicomponent systems remain unclear. In this work, a mineral-assisted sulfation roasting strategy is proposed, in which pyrite (FeS₂) is used to generate sulfur species in situ, enabling preferential lithium sulfation and directional transformation of transition metals. Under roasting at 800 °C, the lithium leaching efficiency reached 95.76%, while the leaching efficiencies of Fe, Co, Ni, and Mn were all below 0.6%, demonstrating highly selective lithium recovery. Nonisothermal thermogravimetric kinetic analysis revealed that the activation energy first decreased and then increased with increasing conversion, indicating that the roasting process follows a distinct two-stage reaction mechanism. The low-temperature stage is dominated by FeS₂ decomposition and lithium sulfation, whereas the high-temperature stage corresponds to the solid-state reaction between Co₃O₄ and Fe₂O₃ to form CoFe₂O₄. Further analysis using the Popescu multiple-scan method identified the most probable kinetic mechanism function as the Mampel power-law model, with a mechanism function of f(α) = 2/3α^-1/2. This study elucidates the reaction mechanism of mineral-assisted sulfation roasting from both reaction pathway and kinetic perspectives.