Realization of Mg²⁺ intercalation in a thermodynamically stable layer-structured oxide

Magnesium batteries have emerged as one of the considerable choices for next-generation batteries. Oxide compounds have attracted great attention as cathodes for magnesium batteries because of their high output voltages and ease of synthesis. However, a majority of the reported results are based on metastable nanoscale oxide materials. This study puts forward a thermodynamically stable layer-structured oxide K_0.5MnO₂ with an enlarged lattice spacing as a model cathode material employing optimized electrolytes, enabling Mg²⁺ intercalation into the K_0.5MnO₂ framework in a real magnesium battery directly using Mg foil as the anode. First-principles calculations implied that the enlarged layer spacing could decrease the migration energy barrier of Mg²⁺ in the layered oxide. This work can pave the way to understanding the fundamental intercalation behavior of Mg²⁺ in magnesium batteries.