This report examines the current and future outlook for critical materials used in sustainable energy applications. These are materials that have the capacity to transform the way we capture, transmit, store or conserve energy. Its conclusions are based in part on facilitated discussions among domain experts on how to set a research and development agenda across the supply chain to mitigate the effects of material criticality on achieving a sustainable energy future. Those discussions were, in turn, informed by several recent reports on this issue.