(Invited) A Route to High Energy Density Co-free Cathode Materials

Cobalt resources may not be able to keep up with the rapidly growing demand for Li-ion energy storage. Disordered rocksalt cathodes present a Co-free alternative to the layered NMC-style cathode materials, used today in much of Li-ion technology. The flexibility of working with a cation-disordered structure creates the option to use a much broader set elements, many of which are abundant and inexpensive. More than a dozen novel cation-disordered cathode materials have been synthesized and tested, most of which contain one or more of either Ti 4+ , Nb 5+ , Zr 4+ , Mo 6+ and a redox active elements from the group of Mn, Fe, V, Ni. In addition, these materials can be fluorinated through simple solid state reactions for enhanced safety and stability at high potential. Bu substituting a large amount of F substitution for O the metal valence can be lowered enough to activate unconventional redox couples, such as Mn2+/Mn4+ leading to very high capacities. Besides the large chemical freedom one has in designing and optimizing these materials, structural features can also be used to optimize the materials. I will show that short-range cation order, which can be influenced by the composition as well as the heat treatment can have a profound influence on performance.