Ultrathin Magnesium Metal Anode – An Essential Component for High‐Energy‐Density Magnesium Battery Materialization

Abstract The practical loading, i. e., thickness, of metal anodes predominates the practical energy density of batteries that incorporate elemental metals as anode active materials. Despite its significance for achieving high‐energy‐density rechargeable magnesium batteries (RMBs), the application of ultrathin magnesium foils remains a challenge because of the brittleness and unworkability of magnesium. This work provides a critical component of a geometric size applicable to laminate‐type cells of dimensions 42×32 mm² or larger. Ultrathin magnesium foil without cracked edges can be fabricated by controlling the initial microstructure. Furthermore, the rolling temperature determines the resulting microstructure and thus the electrochemical properties. The optimal sample, a warm‐rolled magnesium foil, exhibited excellent electrochemical characteristics owing to its favorable microstructure, which facilitated a homogeneous distribution of reaction sites. Battery performance using such ultrathin magnesium anodes was investigated with MgMn₂O₄ and α‐MnO₂ cathodes. Considering the weights of both the cathodes and anodes, the gravimetric energy density of primitive [α‐MnO₂ || pMg] cells was estimated to be 72 Wh kg_electrode⁻¹.