Effect of Mg doping and dopant-vacancy arrangement on the structural stability, electronic structure, and Li-ion migration of anti-perovskite Li3ClO: A first-principles study

Abstract

Lithium-rich anti-perovskites have attracted considerable attention as potential solid electrolytes for all-solid-state lithium batteries because of their structural versatility and defect-mediated Li-ion transport. Among them, Li 3 ClO has emerged as a promising model system for investigating the relationship between defect chemistry and ionic conductivity. In the present work, first-principles density functional theory (DFT) calculations combined with climbing-image nudged elastic band (CI-NEB) simulations were employed to investigate the effects of Mg doping and dopant-vacancy arrangement on the structural stability, defect energetics, electronic structure, and Li-ion migration behavior of Li 3 ClO. Mg-doped configurations containing one, two, and three Mg substitutions were examined, and for each concentration, both near and far Li-vacancy arrangements were considered. The results reveal a concentration-dependent evolution of defect stability. At low Mg concentration, the near dopant-vacancy arrangement is energetically preferred, whereas spatially separated (far) configurations become more stable at higher Mg contents. Local structural analysis further shows that defect arrangement strongly influences lattice distortion and defect accommodation within the anti-perovskite framework. Electronic structure calculations indicate that all investigated configurations retain a wide band gap, confirming preservation of the electronically insulating character required for solid-electrolyte applications. Li-ion migration calculations demonstrate a strong dependence of transport behavior on both Mg concentration and vacancy arrangement. While pristine Li 3 ClO exhibits a migration barrier of 0.361 eV, the M2-far configuration shows the lowest limiting barrier of 0.257 eV among the configurations examined, indicating enhanced Li-ion mobility. In contrast, the M1-near, M2-near and M3-far configurations exhibit higher limiting barriers and strongly asymmetric, less favorable transport characteristics. Overall, the results identify the M2-far configuration, among the configurations examined, as the most favorable balance between thermodynamic stability, preserved electronic insulation, and improved Li-ion transport. These findings highlight the importance of controlling both dopant concentration and defect arrangement in the design of high-performance anti-perovskite solid electrolytes.