Comparative study on the sulfation of spent lithium-ion battery under different sulfur inputs: Extraction efficiency, SO2 emission and mechanism

The recovery of valuable metals from spent lithium-ion batteries (LIBs) is of utmost significance for environmental protection and alleviating resource shortages. Traditional sulfation roasting techniques were accused of their unsustainability and negative environmental impact, such as the consumption of expensive sulfation reagents and the emission of SO2. This study compared the performance of cobalt-lithium co-sulfation and selective sulfation processes under high and low sulfur input conditions with waste ferrous sulfate as sulfation reagent. The results revealed that selective roasting can efficiently achieve lithium separation without SO2 emission. Additionally, a sulfation roasting mechanism for SO2 emission-free conditions under low sulfur input was proposed. At 650 °C, spent lithium cobaltate (LCO) was sulfated via ion exchange with FeSO4 and gas-solid reactions with SO2, and the lithium in the outer layer was selectively sulfated. Partially sulfated CoSO4 was then served as a sulfation agent to sulfate the unreacted LCO at 800 °C, allowing the sulfur element to be fully recovered and recycled in the form of Li2SO4. By comparing the co-sulfation and selective sulfation processes, an efficient and eco-friendly method for recovering metals from spent lithium-ion batteries was established.