Rapid Low-Dimensional Li Ion Hopping Processes in Synthetic Hectorite-Type Li[MgLi]SiOF.

Understanding the origins of fast ion transport in solids is important to develop new ionic conductors for batteries and sensors. Nature offers a rich assortment of rather inspiring structures to elucidate these origins. In particular, layer-structured materials are prone to show facile Li transport along their inner surfaces. Here, synthetic hectorite-type Li[MgLi]SiOF, being a phyllosilicate, served as a model substance to investigate Li translational ion dynamics by both broadband conductivity spectroscopy and diffusion-induced Li nuclear magnetic resonance (NMR) spin-lattice relaxation experiments. It turned out that conductivity spectroscopy, electric modulus data, and NMR are indeed able to detect a rapid 2D Li exchange process governed by an activation energy as low as 0.35 eV. At room temperature, the bulk conductivity turned out to be in the order of 0.1 mS cm. Thus, the silicate represents a promising starting point for further improvements by crystal chemical engineering. To the best of our knowledge, such a high Li ionic conductivity has not been observed for any silicate yet.