The transition to low-carbon energy requires radical infrastructure changes and an expansion in the use of low-carbon technologies. The expansion of these systems also comes with increasing complexity in the materials used to make them, with more and more specialised materials being needed. This brief examines the critical materials cobalt, copper, graphite, lithium, nickel and rare earth elements (REEs). The material supply risks and geopolitical concerns are assessed and strategies to address them are proposed. The brief was reviewed and edited by Simon Patterson (CCG, Loughborough University) and was designed by Sarel Greyling (Sarel Greyling Creative). This material has been produced under the Climate Compatible Growth programme (which is funded by UK aid from the UK government), and Chatham House. However, the views expressed herein do not necessarily reflect the UK government's official policies.