Muon Spectroscopy for Investigating Diffusion in Energy Storage Materials

We review recent applications of positive muon spin relaxation (mu SR) spectroscopy as an active probe of ion diffusion in energy storage materials. mu SR spectroscopy allows the study of ionic diffusion in solid-state materials on a time scale between 10-5 and 10-8 s where most long-range and consecutive short-range jumps of ions between interstitial sites occur. mu SR also allows one to probe and model ionic diffusion in materials that contain magnetic ions, since both electronic and nuclear contributions to the muon depolarization can be separated, making mu SR an excellent technique for the microscopic study of the ionic motions in crystalline materials. We highlight a series of battery materials for which mu SR has provided insight into intrinsic ionic conduction and magnetic properties without interference of external factors, such as the presence of magnetic ions, macroscopic particle morphologies, or elaborate measurement setups.