Cobalt Deposition from Ionothermally Dissolved Cobalt Oxides

Owing to the environmental problems of numerous metal production processes, there is a growing need for more energy-efficient approaches. Cobalt is considered a strategic element that is extracted not only from ores but also from spent Li-ion batteries. One promising new approach is ionometallurgy, which is the extraction of metal oxides by ionic liquids (ILs). This study concerns new investigations into ionometallurgical processing of CoO, Co3O4, and LiCoO2 in the IL betainium bis(trifluoromethylsulfonyl)imide, [Hbet][NTf2]. Three crystal structures of cobalt-betaine complex compounds and combined spectroscopic and diffraction studies provide insights into the dissolution process. In addition, an optimized dissolution procedure for metal oxides is presented, avoiding the previously reported decomposition of the IL. Subsequent cobalt electrodeposition is only possible from cationic complex species, highlighting the importance of a thorough understanding of the complex equilibria. The presented method is also compared to other recently reported approaches.

Automated summary

Due to environmental concerns with current metal production processes, more energy-efficient methods are needed. Cobalt, extracted from ores and spent Li-ion batteries, is a strategic element. Ionometallurgy, using ionic liquids (ILs) to extract metal oxides, presents a promising approach. This research focuses on ionometallurgical processing of CoO, Co3O4, and LiCoO2 in the IL [Hbet][NTf2], providing insights into the dissolution process and optimizing the dissolution procedure to avoid IL decomposition. The importance of understanding complex equilibria is highlighted for successful cobalt electrodeposition.