First-Principles Insight into the Antiperovskite c-Na3HS Solid-State Electrolyte

Abstract

We explore the potential of the novel antiperovskite c-Na₃HS to be a solid-state electrolyte for sodium-ion batteries. To investigate the dynamical stability, phase stability, thermal stability, mechanical stability, and ionic, electronic, and diffusive properties of c-Na₃HS, first-principles methods based on density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations have been employed. c-Na₃HS has no imaginary phonon modes, indicating its dynamical stability. Key findings include a small energy above the hull, a wide band gap of 4.25 eV, and a mechanical stability analysis that indicates the moderately hard and a little brittle nature of c-Na₃HS. The activation energy of Na in c-Na₃HS is calculated to be ∼300 meV, which reduces to ∼100 meV upon introducing Na vacancy. The ionic conductivity can be enhanced by up to ∼3 orders of magnitude by vacancy and halogen doping in the c-Na₃HS structure. Thus, the obtained results indicate that c-Na₃HS can be a viable option to be utilized as a solid-state electrolyte in sodium-ion batteries.