David Halat, Ph.D
Abstract
Understanding the fundamental mechanisms of ion transport in energy storage and conversion devices is key to advancing next-generation, beyond-Li technologies less reliant on critical minerals. Novel and emerging magnetic resonance methods, including quadrupolar and electrophoretic NMR (eNMR), are premier local structure probes that can provide sensitive mechanistic insights into ion mobility in electrochemical systems that are often unattainable by other techniques. NMR measurements of quadrupolar nuclei present challenges due to extremely broad NMR lineshapes, but also confer unique sensitivity to motional averaging processes. We show how 23Na and 25Mg NMR techniques applied to beyond-Li antiperovskite solid-state electrolytes yield temperature-dependent quadrupolar powder patterns that reveal local ion-hopping mechanisms, as well as quantitative exchange rates of ion motion, leading to the development of more advanced solid-state electrolytes. In the second part of this work, we show how eNMR experiments quantify ion and solvent mobilities in multicomponent liquid electrolyte systems under applied electric field, thereby directly measuring transference numbers and obtaining mechanistic insights into solvation. We report 1H, 7Li, and 19F eNMR studies in LiTFSI/tetraglyme electrolytes, where solvent velocity trends highlight solvation-mediated transport. Further, diffusion NMR and eNMR experiments in POSS-based electrolytes reveal cases of negative transference numbers, where cations move the “wrong way” under application of an electric field. These results demonstrate how NMR techniques can offer a comprehensive framework for understanding ion dynamics and optimizing chemical and materials systems for energy applications.
When: October 31, 2025
Where: North Classroom
Time: 11:00 am - 12:00pm