We request 4 days on Vesuvio to study the crystal Li2S and Li2Se. This is supported by EPSRC grant number EP/K002546/1 and will demonstrate further the ability of VESUVIO in studies of lithium-containing materials.A number of unique factors will be able to be determined by DINS of the 7Li2S / 7Li2Se systems:1)Is there a measurable difference in Li mean kinetic energy and ground state momentum distribution between the low conductivity 7Li2S and higher conductivity and isostructural 7Li2Se.2)Can average kinetic energies for the three masses Li, S and Se be determined simultaneously, separated from the sample can environment, and compared with that calculated from ab initio or molecular dynamics calculations.