Cobalt blues: An overview of the thermodynamics of a critical element in short supply

The demand for cobalt has increased substantially in recent decades because of increased use in technology. The battery industry especially has generated an enormous increase in demand, and projected shortages loom within the next decade. Cobalt is relatively scarce in the Earth's crust and is considered a strategic material by many nations. Its ore supply is dominated by Central Africa, and political instability and unethical mining practices are risks to global supply. Alternative sources of cobalt, as well as the development of new production and processing routes, are needed but require an understanding of the thermodynamic stability of the involved phases. The thermodynamic data for these materials are remarkably incomplete and scattered in literature within different disciplines. In this review, we survey the available thermodynamic data for cobalt minerals and ores, as well as inorganic synthetic compounds. We discuss gaps in the data and suggest avenues for further research. To provide a resource for future thermodynamic studies and encourage discussion of new research and ideas for cobalt materials, we have surveyed, compiled, and systematized the extant thermodynamic data for cobalt-bearing compounds. The overall goals of this review are to make available data more readily accessible and to identify needs for future research.