Three-Dimensional Magnesiophilic Scaffolds for Reduced Passivation toward High-Rate Mg Metal Anodes in a Noncorrosive Electrolyte

Magnesium ion batteries are a promising alternative of the lithium counterpart; however, the poorly ion-conductive passivation layer on Mg metal makes plating/stripping difficult. In addition to the generally recognized chemical passivation, the interphase is dynamically degraded by electrochemical side reactions. Especially under high current densities, the interphase thickens, exacerbating the electrode degradation. Herein, we adopt 3D Mg₃Bi₂ scaffolds for Mg metal, of which the high surface area reduces the effective current density to avoid continuous electrolyte decomposition and the good Mg affinity homogenizes nucleation. The greatly alleviated passivation layer could serve as a stable solid/electrolyte interface instead. The symmetric cell delivers a low overpotential of 0.21 and 0.50 V at a current density of 0.1 and 4 mA cm^–2, respectively, and a superior cycling performance over 300 cycles at 0.5 mA cm^–2 in a noncorrosive conventional electrolyte. This work proves that the control of dynamic passivation can enable high-power density Mg metal anodes.