Figure : The migration barriers obtained from NEB calculations against the site preference E oct -E tet for various spinel compounds: Al (blue), Mg (red), Ca (green), Zn (orange), Li (yellow), and Na-based (brown) materials. Data are obtained and replotted from Refs. Sulfide and selenide spinels have garnered attention due to their potential as solid electrolytes in solid-state batteries. Among these compounds, MgSc 2 Se 4 has emerged as a promising contender with a remarkably low migration barrier of E a = 0.37 eV. 2,28-30 Nevertheless, its suitability as a solid electrolyte is impeded by a significant partial electronic conductivity. Moreover, studies have indicated that the mobility of magnesium in chalcogenide spinels that include lanthanoids escalates proportionally with the lanthanoid's size.