Unlocking Li Superionic Conductivity in Fcc-Type Oxides via Face-Sharing Configurations

Li metal oxides with a face-centered cubic (<i>fcc</i>) anion sublattice have been generally excluded from the search for solid-state Li superionic conductors, as the structural framework is thought to be unfavorable for Li superionic conduction. Herein, we demonstrate a face-sharing design strategy that turns <i>fcc</i>-type oxides into superionic conductors, with a Li ionic conductivity of 3.38×10⁻⁴ S cm⁻¹ at room temperature and a low migration barrier of 255 meV. The combination of experimental and theoretical investigations reveals that the high Li-ion conductivity is attributed to the facile Li-ion diffusion pathways comprising the face-sharing polyhedra. Our work unlocks the great potential of designing Li superionic conductors in a prototypical structural framework with vast chemical flexibility, providing a fertile ground for discovering new solid-state electrolytes for all-solid-state batteries.