In Situ Neutron Powder Diffraction of Li6C60 for Hydrogen Storage

Li6C60 is the best performing fullerene-derived hydrogen storage material. We report the thermal evolution of Li6C60 upon deuterium absorption up to 330 °C and under 60 bar D2 using in situ neutron powder diffraction. We are able to discern between the hydrogenation of Li6C60 and the segregation of lithium hydride (LiD) during absorption from a mechanistic point of view. During absorption, Li6C60 undergoes several phase transitions, involving the partial segregation of Li in form of hydride and the expansion of the fcc lattice followed by a bcc rearrangement of the deuterated fullerenes. The amount of absorbed deuterium was determined by the analysis of the variation in the scattered neutron intensity and confirmed by a desorption measurement.