First-principles insights into NaMgPO₃S oxysulfide solid electrolyte

The development of high-performance solid electrolytes is pivotal for advancing solid-state battery technologies. In this work, we design an oxysulfide-based solid electrolyte NaMgPO₃S by combining bond valence theory and density functional theory calculations. The material features a wide band gap of 4.0 eV and a considerable reduced Na⁺ migration barrier of 0.44 eV, a 1.26-eV decrease compared to pristine NaMgPO₄ (∼ 1.70 eV). Ab initio molecular dynamics simulations further reveal significantly enhanced ionic conductivity in the oxysulfide-based system compared to the pristine oxide structure. In addition, the calculated decomposition energy indicates that the modified material exhibits good moisture stability. Our findings suggest that sulfur-doping strategy can simultaneously achieve improved ionic conductivity and high moisture stability in oxide solid electrolytes, which could pave the way for designing high-performance solid electrolytes.