To Be or Not to Be – Is MgSc₂Se₄ a Mg‐Ion Solid Electrolyte?

Abstract

Magnesium batteries offer promising potential as next‐generation sustainable energy‐storage solutions due to the high theoretical capacity of the magnesium metal anode. Facilitating dendrite‐free operation of metal anodes necessitates the development of solid electrolytes with high magnesium‐ion conductivity. While the chalcogenide spinel MgSc2Se4 is predicted to exhibit high magnesium ion mobility, unequivocal experimental evidence for magnesium ion conduction beyond short‐range motion is still missing. This study confirms magnesium‐ion transport in MgSc2Se4 through two independent electrochemical methods: electrochemical deposition of magnesium metal and reversible magnesium plating/stripping cycling. To overcome the difficulty of measuring the ionic conductivity of the mixed conducting MgSc2Se4 spinel, a pure ion conducting interlayer is employed in a symmetric transference cell. This approach effectively suppresses the electron transport, allowing accurate characterization of the ionic conductivity. The experimental results confirm a low migration barrier of (386 ± 24) meV for magnesium ion transport in MgSc2Se4 and demonstrate one of the best performances at room temperature among the reported inorganic magnesium solid electrolytes. The findings open a new door for exploring additional mixed magnesium ion conductors and highlight the potential of magnesium chalcogenide spinels as a promising class of magnesium solid electrolytes.

Trendbericht Festkörperchemie und Materialforschung 2024

“…Erstmals haben Janek und Mitarbeitende den Mg 2+ -Transport in MgSc 2 Se 4 auf zwei Wegen nachgewiesen: durch elektrochemische Abscheidung elementaren Magnesiums und durch reversible Magnesiumgalvanisierung und -entschichtung. 23) Die beobachtete niedrige Migrationsbarriere (386 ± 24 meV) führt zu einer der besten Leistungen bei Raumtemperatur unter den bekannten anorganischen Magnesiumfestelektrolyten.…”

Fast Room‐Temperature Mg‐Ion Conduction in Clay‐Like Halide Glassy Electrolytes

“…The room temperature (RT) ionic conductivity of borohydride materials can reach up to 10 −5 S cm −1 with such ligand substitution, [ 22 ] yet further conductivity enhancement is necessary for RT battery operation. The spinel chalcogenide MgSc 2 Se 4 which was first reported in 2017 [ 17 ] and recently further confirmed, [ 23 ] has some of the highest RT Mg‐ion conductivity of 0.1 mS cm −1 , but is hampered by a high intrinsic electronic conductivity.…”