Mapping Long-Range 3D Lithium Diffusion in Solid Electrolytes Using PGSE NMR, XRD, and MD Simulations: From Model Hydrides to Advanced LGPS Superionic Conductorsat Osborne Center for Science and Engineering

Solid-state lithium electrolytes are critical to the development of safe and efficient electrochemical cells. They eliminate flammable organic solvents, physically suppress dendrite growth, and significantly extend battery life for long-duration energy storage applications. Macroscopic ion transport in these materials is strictly governed by the topology, dimensionality, and local anisotropy of diffusion pathways within the crystal lattice. This lecture presents a comprehensive, multiscale research approach that integrates ⁷Li pulsed-field gradient NMR (PGSE NMR) spectroscopy, molecular dynamics (MD) simulations, and X-ray diffraction (XRD) with Rietveld refinement. The first part of the talk will discuss results for model hydride systems: the high-temperature hexagonal phase of LiBH₄ and LiBH₄–LiBr composites. XRD-Rietveld analysis confirmed the P6₃mc space group symmetry, providing a structural basis for MD simulations, which revealed intertwined lithium migration channels along the [001] direction with zig-zag jumps across the (001) planes. PGSE NMR experiments quantified the diffusion tensor components, demonstrating distinct transport anisotropy (D∥ > D⊥). By modeling the powder-averaged diffusion tensor based on Euclidean space rotation schemes, we derived analytical equations linking the measured spin-echo attenuation to the principal tensor components, allowing for a precise correlation between experimental activation barriers and MD energy landscapes. The focus of the lecture will be the extension of this methodology to advanced superionic sulfide conductors with an argyrodite-type structure and top-tier all-solid-state battery conductors, specifically, the LGPS (Li₁₀GeP₂S₁₂) family. New structural (XRD) and dynamic (⁷Li PFG-NMR) results for LGPS phases will be juxtaposed with theoretical models to map 3D ionic percolation pathways. This integrated framework effectively opens the "black box" of macroscopic conductivity measurements, providing materials scientists with precise guidelines for optimizing crystallographic texture, lattice strain, and grain boundaries to achieve ultrafast charging in modern solid-state batteries. Hosted by: Department of Physics & Energy Science, UCCS Physics Club Additional Information can be found at: https://mlc.uccs.edu/event/12648517