Structure and ion diffusion of hexagonal Li5(PS4)Cl2 superionic conductor from molecular dynamics simulations

Abstract

All-solid-state battery technology is considered a promising candidate for next-generation batteries. Sulfide-based materials, particularly lithium thiophosphates, show great potential due to their Li-superionic conductivity at room temperature. We have performed a study of the structure and Li-ion diffusion in Li5(PS4)Cl2 using molecular dynamic simulations at various temperatures. Our research proposed a new hexagonal structure with space group P63mc for this material. We find that the Li sublattice is disordered over four crystallographic positions in this structure, which provides favorable conditions for fast Li-ion diffusion, ~10−7 cm2/s, leading to a superionic conductivity of ~2 × 10−2 S/cm with an activation energy of ~0.3 eV at room temperature. Our simulations indicate that the Li-ion conductivity of Li5PS4Cl2 is almost isotropic. This predicted conductivity is among the highest reported for known solid electrolytes. Based on our computational findings, we proposed a mechanism for the Li-ion diffusion in the hexagonal Li5PS4Cl2 and discussed it in detail. This research shows the potential of computational tools to guide the rational design of next-generation solid-state electrolytes and how predictive modeling can accelerate innovation in materials development.