Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for elucidating the molecular-level chemical, structural, and electronic changes that battery materials undergo upon electrochemical cycling. However, battery materials are often challenging to characterize by NMR: composite battery electrodes are highly heterogeneous solids, often including inactive components (e.g., conducting carbon) and residual liquid electrolyte signals, while the electroactive material may exhibit significant disorder, be or become paramagnetic, and contain quadrupolar nuclei of interest. Meanwhile, polymer electrolytes can be affected by magic-angle-spinning (MAS), while liquid electrolytes may contain small but important quantities of species associated with deleterious electrochemical side reactions. Here, I will present case studies of how such obstacles can be overcome, focusing on practical aspects, tips, tricks, and pitfalls of acquiring solid-state, liquid-state, and pulsed-field-gradient (PFG) NMR measurements of battery electrodes and electrolytes. Examples will be presented from advanced aluminum and lithium battery systems with applications ranging from robotic spacecraft to electric vehicles. Overall, the results contain practical experimental methods for acquiring quantitative and high-resolution NMR measurements on complex, heterogeneous materials, while yielding new molecular-level insights into emerging battery systems and concepts.
