Correlated Factors for Li-Ion Migration in Ionic Conductors with the fcc Anion Sublattice

The development of solid-state electrolytes (SSEs) with high lithium ionic conductivities is critical for the realization of all-solid-state Li-ion batteries. Crystal structure distortions, Li polyhedron volumes, and anion charges in SSEs are reported to affect the energy landscapes and it is paramount to investigate their correlations. In this study, we reveal that the distorted tetrahedrally occupied lithium is less energetic favorable than the distorted octahedrally occupied lithium, rationalized from the heatmap of anion charges, lattice volumes and sites distortion. Our works uncover the cooperative effect of lithium site distortions, anion charges and lattice volumes on Li ion migration energy barrier in superionic conductors of LiMS₂ (M =Sc, Ti, V, Cr, Mn, Fe, Co, Ni) and Li₂MO₃ (M =Sc, Ti, V, Cr, Mn, Fe, Co, Ni). Manipulating the distortion of tetrahedrally occupied lithium is more impelling than the adjustment of octahedrally occupied lithium distortion to lower Li ion migration barrier. The new descriptor, Li ion sites distortion, can provide new insights into the strategy for screening high conductivity solid-state electrolytes.