Synthesis of Antiperovskite Solid Electrolytes: Comparing LiSI, NaSI, and AgSI.

Prior calculations have predicted that chalcohalide antiperovskites may exhibit enhanced ionic mobility compared to oxyhalide antiperovskites as solid-state electrolytes. Here, the synthesis of Ag-, Li-, and Na-based chalcohalide antiperovskites is investigated using first-principles calculations and synchrotron X-ray diffraction. These techniques demonstrate that the formation of AgSI is facilitated by the adoption of a common body centered cubic packing of S and I in the reactants and products at elevated temperatures, with additional stabilization achieved by the formation of a solid solution of the anions. The absence of these two features appears to hinder the formation of the analogous Li and Na antiperovskites.