Extraction of Cobalt from Lithium-Ion Battery Scrap via Selective Sulfation Roasting

Extraction of cobalt from secondary resources has become crucial as cobalt has been identified as strategically important and critical raw material due to high risks in supply chain disruptions. In this work, a novel route has been investigated for selective extraction of cobalt from spent industrial lithium cobalt oxide (LCO) - rich battery scrap. In the first set of experiments, the sieved black mass fraction containing both cathode and anode materials is directly roasted at 850 °C in a predetermined composition of gas mixture of SO2, O2 and argon for 1 hour. The gas composition is determined from Kellogg’s diagram to allow selective sulfation of cobalt. In another set of experiments, carbon present in the black mass is removed separately – material is firstly roasted in argon for 2 hours and then in argon and oxygen gas mixture for 5 hours at 600 °C. Afterwards, selective sulfation is performed in SO2, O2 and Argon gas mixture similar to the previous set of experiments. The sulfation roasted black mass is leached in water to study the efficiency of cobalt extraction. For comparison, similar experiments are performed at 800 °C. Interestingly, presence of carbon from anode was found to be beneficial for cobalt extraction. The cobalt extraction efficiency for the first case (with carbon present in the raw material) was observed to be more than three times higher when compared to the second case (with carbon removal) for sulfation at 850 °C. The extraction efficiency and purity of extracted cobalt were found to be better for higher temperature sulfation roasting conditions due to faster reaction kinetics. These results suggest that cobalt can be selectively extracted from black mass by roasting pre-treatment followed leaching in water thus avoiding acid leach used in hydrometallurgical processes. In holistic processing, the leach residue can then be further subjected for battery metal processing by the state-of-the-art methods.