Highly Mobile Ions: Low-Temperature NMR Directly Probes Extremely Fast Li+ Hopping in Argyrodite-Type Li6PS5Br

The development of safe and long-lasting all-solid-state lithium-ion batteries needs electrolytes with exceptionally good transport properties. Here, we report on the combination of several solid-state nuclear magnetic resonance (NMR) techniques which have been used to precisely probe short-range as well as long-range Li+ dynamics in Li6PS5Br from an atomic-scale.point of view. NMR data clearly reveal an extraordinary high Li diffusivity. This manifests in so-called diffusion-induced spin-lattice relaxation NMR rate peaks showing up at temperatures as low as 260 K. From a quantitative point of view, at ambient temperature the Li jump rate is of the order of 10(9) s(-1) which corresponds to a Li+ conductivity in order of 10(-3) to 10(-2) S/cm, thus, indicating liquid-like Li+ diffusion behavior in Li6PS5Br.