Solid-state materials with high ionic conduction are necessary for many technologies, including all-solid-state lithium (Li)-ion batteries. Understanding how crystal structure dictates ionic diffusion is at the root of the development of fast ionic conductors. Here, we show that LiTi2(PS4)3 exhibits a Li-ion diffusion coefficient about an order of magnitude higher than that of current state-ofthe-art Li superionic conductors. We rationalize this observation by the unusual crystal structure of LiTi2(PS4)3, which offers no regular tetrahedral or octahedral sites for Li to favorably occupy. This creates a smooth, frustrated energy landscape resembling the energy landscapes present in liquids more than those in typical solids. This frustrated energy landscape leads to a high diffusion coefficient, combining low activation energy with a high pre-factor.
Di Stefano, D., Miglio, A., Robeyns, K., Filinchuk, Y., Lechartier, M., Senyshyn, A., Ishida, H., Spannenberger, S., Prutsch, D., Lunghammer, S., Rettenwander, D., Wilkening, M., Roling, B., Kato, Y., & Hautier, G. (2019). Superionic Diffusion through Frustrated Energy Landscape. Chem, 5(9), 2450-2460. https://doi.org/10.1016/j.chempr.2019.07.001 (Original work published 2019)