Sulfation Roasting Mechanism for Spent Lithium-Ion Battery Metal Oxides Under SO₂-O₂-Ar Atmosphere

Sulfation roasting followed by water leaching has been proposed as an alternative route for recycling valuable metals from spent lithium-ion batteries (LIBs). In the present work, the reaction mechanism of the sulfation roasting of synthetic LiCoO₂ was investigated by both thermodynamic calculations and roasting experiments under flowing 10% SO₂-1% O₂-89% Ar gas atmosphere at 700°C. The products and microstructural evolution processes were characterized by x-ray diffraction, scanning electron microscope and energy dispersive x-ray spectrometer, and atomic absorption spectroscopy. It was confirmed that Co₃O₄ was formed as an intermedia product, and the final roasted products were composed by Li₂SO₄, Li₂Co(SO₄)₂, and CoO. The leaching results indicated that 99.5% Li and 17.4% Co could be recovered into water after 120 min of roasting. The present results will provide the basis and solid guidelines for recycling of Li and Co from spent LIBs.