Publication date: 10th April 2024
Solid electrolytes (SE) are essential for building all-solid-state batteries with improved electrochemical performance and safety. However, understanding their structural complexities and ion dynamics is crucial for developing and tailoring SEs with desired properties, a task that can be effectively addressed by solid-state nuclear magnetic resonance (NMR) spectroscopy. Here, we present recent work focusing on structural investigations and cation dynamics experiments conducted using solid-state NMR techniques. Structural insights, such as the experimental distinction of octahedral and tetrahedral Li-position in sulfide-type Li-SEs and the effects of stacking faults on lithium environments in lithium halide-based substitution series, are revealed through magic angle spinning (MAS) NMR experiments. Cation dynamics experiments, including static variable-temperature NMR experiments for motional narrowing of NMR signals and T1-relaxation measurements, provide valuable information about ion mobility (kHz/MHz dynamics) and activation energies. Furthermore, two-dimensional exchange spectroscopy (EXSY) can be utilized to observe the exchange of cations between different crystallographic sites and quantitatively extract site-specific ion jump rates (kHz/Hz dynamics). Thus, the insights on local coordination and ion dynamics in SE highlight solid-state NMR as a powerful tool for unraveling the complex interplay between SE structure and cation dynamics, facilitating the development of improved SE materials for future battery technologies.
B.S. is a member of the International Graduate School for Battery Chemistry, Characterization, Analysis, Recycling and Application (BACCARA), which is funded by the Ministry for Culture and Science of North Rhine Westphalia, Germany.