Role of s-p Orbital Hybridization in Enhancing the Lithium-Ion Conductivity of Antiperovskite Li3–xOHxCl Solid Electrolytes

Li₃OCl-type antiperovskites have gained significant attention as solid-state electrolytes due to their high lithium-ion conductivity. Recent studies found that H is inevitably incorporated into the Li₃OCl structure in humid environments, resulting in increased ionic conductivity. However, the role of H in enhancing ionic conductivity remains poorly understood. Herein, we employ density functional theory calculations to investigate how H incorporation affects the electronic structure of Li_3–xOH_xCl (0 ≤ x ≤ 1). Our results reveal that Li_2.1OH_0.9Cl (x = 0.9) exhibits the highest lithium-ion conductivity (4.40 × 10^–5 S/cm). Electronic structure analyses indicate that the enhancement in conductivity arises from strong s-p orbital hybridization between the Li-s orbital and the Cl/O-p orbitals, which reduces the energy barrier for lithium-ion migration by enhancing electron cloud overlaps. These findings clarify the critical role of H in modifying the electronic structure to enhance the ionic conductivity of Li₃OCl-type antiperovskites, providing an effective modulation strategy for the development of high-performance solid-state electrolytes.