Structural Insights and 3D Diffusion Pathways within the Lithium Superionic Conductor Li₁₀GeP₂S₁₂

Inspired by the ongoing debate about the ion dynamics in the lithium superionic conductor Li 10 GeP 2 S 12 (LGPS), we present neutron powder diffraction data in combination with analyses of differential bond valence and nuclear density maps to elucidate the underlying diffusion pathways in Li 10 GeP 2 S 12 . LGPS exhibits quasi-isotropic three-dimensional lithium diffusion pathways, which is a combination of one-dimensional diffusion channels crossing two diffusion planes. Furthermore, ultrasonic speeds of sound measurements are used to understand the lattice dynamics and obtain the Debye temperature of LGPS. Temperature dependent X-ray diffraction is performed in order to understand the local temperature-dependent behavior of the prevalent structural backbone, as well as the thermal stability of the material. At elevated temperatures, the superionic conducting Li 10 GeP 2 S 12 phase partially decomposes into Li 4 P 2 S 6, explaining the deterioration of the ionic conductivity upon heating.