Planting Repulsion Centers for Faster Ionic Diffusion in Superionic Conductors

The successful launch of solid-state batteries relies on the discovery of solid electrolytes with remarkably high ionic conductivity. Extensive efforts have identified several important superionic conductors (SICs) and broadened our understanding of their superionic conductivity. Herein, we propose a new design strategy to facilitate ionic conduction in SICs by planting immobile repulsion centers. Our ab initio molecular dynamics simulations on the model system Na₁₁Sn₂PS₁₂ demonstrate that the sodium ionic conductivity can be increased by approximately one order of magnitude by simply doping large Cs ions as repulsion centers in the characteristic vacant site of Na₁₁Sn₂PS₁₂. Planting immobile repulsion centers locally induces the formation of high-energy sites, leading to a fast track for ionic conduction owing to the unique interactions among mobile ions in SICs. Seemingly non-intuitive approaches tailor the ionic diffusion by exploiting these immobile repulsion centers.