Mapping the Various Li <sup>+</sup> Jump Pathways in Li <sub>10</sub> GeP <sub>2</sub> S <sub>12</sub> : From Ultraslow Exchange to High-Temperature Diffusion
Annika Marko, Katharina Hogrefe, Lukas Schweiger, Florian Stainer, Jana Königsreiter, Jonas Spychala, Jakob Schwaiger, Paul Heitjans, Bernhard Gadermaier, Martin Wilkening
Abstract
High Resolution Image Download MS PowerPoint Slide The solid electrolyte Li 10 GeP 2 S 12 is known to exhibit exceptionally fast Li + diffusion within its tetragonal crystal structure. Experimentally, however, the various Li + hopping processes remain incompletely understood. In this study, we employed 7 Li spin-alignment echo (SAE) NMR and complementary NMR techniques to resolve lithium-ion dynamics in LGPS over nearly 12 orders of magnitude in jump rates, from ultraslow local exchange at 90 K to fast long-range diffusion close to room temperature. Our data reveal a sequence of dynamic regimes and activation energies that reflect the dimensional evolution of Li + transport, from localized 1D hopping to full 3D diffusion. The SAE NMR decay rates, which directly reflect slow Li + jump rates, on the order of one jump every three seconds (0.32(2) s –1 ) at 90 K, reveal two distinct dynamic regimes with activation energies of 0.09 and 0.18 eV, suggesting a transition from 1D to 2D diffusion. At higher temperatures, a third regime emerges, characterized by an activation energy of 0.28 eV, detected by NMR relaxation and SAE NMR. This regime likely corresponds to 3D Li + transport, and the measured rates are in excellent agreement with those from pulsed field gradient NMR, quasi-elastic neutron scattering, and theoretical predictions.