Enhancement of the Li Conductivity in LiF by Introducing Glass/Crystal Interfaces

For a variety of purposes, solid electrolytes with high ionic conductivity are believed to be an alternative to widely used liquid electrolytes. Most of them are developed based on the exploration of crystalline or amorphous structures. As a very rare example of the beneficial influence of glass/ceramic interfaces, we report the conductivity of LiF films on SiO₂. The LiF thin films are surprisingly found to be structurally disordered on the silica (0001) surface, leading to a remarkable enhancement of the Li‐ion conductivity (6 × 10^?6 S cm^?1 at 50 °C, with an activation energy of 0.55 eV) of three orders of magnitude. The resulting conductivity is not exceedingly high, but is comparable with that of the current, best thin‐film solid electrolyte (Li_{(3 + x)}PO_{(4 ‐ x)}N_x). The conductivity is highest if a significant density of glass/ceramic interfaces is achieved and percolation of the interfaces guaranteed.