A critical raw material provides essential properties to an engineered material or system, has few if any easy substitutes and is subject to supply-chain risks or concerns about long-term availability. In lithium-ion batteries, cobalt, lithium and graphite frequently are cited as possible critical materials. In addition, for emerging energy storage technologies, manganese, magnesium, vanadium and others are possible critical materials. In some cases, supply-chain risks relate to geopolitical concerns about nations mining or processing a raw material. In other cases, risks are due to a material's being produced largely as a by-product or companion to other major or host materials - in which case, a material's availability depends on developments in the markets for both the companion and host materials. Over the longer term, society is not in danger of running out of any single raw material. Rather, it faces the prospect of mining lower quality mineral resources, implying higher costs and greater environmental disturbances unless offset by process innovations. This talk reviews the nature and degree of 'criticality' for those raw materials with actual or possible important roles in energy storage.