In-Channel and In-Plane Li Ion Diffusions in the Superionic Conductor Li10GeP2S12 Probed by Solid-State NMR

Li10GeP2S12 (LGPS) is a new solid electrolyte of the highest Li ionic conductivity reported as of now. An anisotropic 3D Li ionic transport network consisting of an ultrafast Li 1D diffusion tunnel and fast in-plane 2D pathways was previously predicted by molecular dynamics simulations. In this paper, we have studied in detail the Li ion dynamics in LGPS by multiple solid-state NMR methods. Two different Li motion processes, characterized by apparently different activation energies of 0.16 eV and 0.26 eV, were unambiguously probed by both 7Li and 31P solid-state NMR and assigned to Li ion diffusions in the 1D tunnel and in the 2D plane, respectively. 31P spin-locking relaxation measurement further reveals that interstitial position Li(4) is active for in-plane Li migration.