A Comprehensive Investigation of Ag₇P₃X₁₁ (X={O, S, and Se}) Solid-State Silver Superionic Conductors

Abstract

This study carefully analyzes and proposes a new class of high-performance inorganic solid-state electrolytes with the composition Ag₇P₃X₁₁ (X = {O, S, and Se}), using ab initio calculations. The structural and electronic properties, as well as electrochemical stability, were evaluated and discussed. Ionic conductivity of Ag⁺ was determined through ab initio molecular dynamics simulations at various temperatures. The results indicate that the room-temperature ionic conductivity of Ag₇P₃Se₁₁ is approximately 13.98 mS cm⁻¹, which is higher than that of most other solid-state electrolytes. The calculated activation energy is relatively low at 0.197 eV. The phenomenon of Ag⁺ ion transport was systematically studied by analyzing the diffusion minimum-energy pathways using the nudged elastic band (NEB) method. The electronic band gaps of the materials studied, calculated using the HSE06 method, ranged from 1.47 to 2.34 eV. Finally, the feasibility of synthesizing these proposed superionic materials was explored through phase stability calculations, including phonon analysis based on density functional perturbation theory (DFPT), thermodynamic stability, radial distribution function, and Gibbs free energy calculations. The results presented provide a guide for designing stable and safe superionic conductors.