Structure–property relationships in lithium superionic conductors having a Li10GeP2S12-type structure

The crystal structures of the superionic conductors Li 9.81 Sn 0.81 P 2.19 S 12 and Li 10.35 Si 1.35 P 1.65 S 12 , both having a Li 10 GeP 2 S 12 (LGPS)-type structure, were determined by neutron diffraction analysis over the temperature range 12–800 K. The maximum entropy method was also employed to clarify the lithium distribution in these materials. The Sn system showed one-dimensional diffusion in the c direction over a wide temperature range, even though the Ge-based system typically exhibits three-dimensional conduction at higher temperatures. The ionic conduction mechanisms of analogous Si, Ge and Sn phases with LGPS-type structures are discussed on the basis of the observed structural parameter changes.