Exploring Ion Dynamics in Solid-State Electrolytes of Lithium- and Sodium-Ion Batteries through Solid-State Nuclear Magnetic Resonance

Abstract

This body of work applies various solid-state nuclear magnetic resonance (ssNMR) techniques to study the ion transport phenomena within different solid-state electrolytes (SSEs) for energy storage devices. The investigation covers length scales ranging from atomic-level ion hopping to microscale ion diffusion, extending further to macroscopic electrode-electrolyte interfacial stability. 7Li NMR diffusometry was employed to probe the Li+ transport in polymer electrolytes upon structural modifications. Additionally, pressure-treated crystalline electrolytes were analyzed with diffusometry and relaxometry, to explore how mechanical stress impacts ion transport as a result of micromorphological changes of the crystalline materials. Furthermore, with the combination of ssNMR and computational methods, the crystallographic Na+ site exchange mechanism in a novel crystalline sodium ion conductor was also explored. Finally, in situ 7Li ssNMR spectroscopy and magnetic resonance imaging (MRI) were employed to correlate stack pressure with metallic Li microstructures formed at the Li-electrolyte interface in a hybrid electrolyte. In summary, the work presented in this thesis demonstrates the robustness of ssNMR in delivering detailed insights into ion dynamics and molecular structures, from molecular scale to macroscopic interface stability. It provides valuable information for battery research, enhancing our understanding of material properties and performance in energy storage applications.