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.