MgSc₂Se₄—A Magnesium Solid Ionic Conductor for All‐Solid‐State Mg Batteries?

Abstract

Recently, the ternary spinel selenide MgSc₂ Se₄ was proposed to have high magnesium ion mobility and is therefore an interesting potential candidate as a solid electrolyte in magnesium secondary batteries. To test the properties of the material, a modified solid-state reaction was used to synthesize pure MgSc₂ Se₄ . Electrochemical characterizations identified detrimental high electronic conductivities, which limit its application as a Mg-conducting solid electrolyte. Two methods were attempted to lower electronic conductivities, including the implementation of Se-rich phases and aliovalent doping, however, with no sufficient improvement. Based on the mixed conducting properties of MgSc₂ Se₄ , a reversible insertion/extraction of Mg²⁺ into the spinel structure could be demonstrated.