Magnesiophilic Black Phosphorus Interphase Enabling Planar Electrodeposition and High-Rate Long-Cycling Magnesium Metal Anodes

Abstract

Magnesium metal anode is considered a promising alternative to lithium metal anode due to its high volumetric/gravimetric energy density, natural abundance, and high safety property. However, its practical application remains limited by detrimental three-dimensional (3D) deposition behavior, leading to shallow deposition/stripping capability and rapid short-circuit with low current density and restricted deposition capacity tolerance. In this study, a magnesiophilic black phosphorus interface is introduced onto a magnesium metal anode to homogenize the spatial distributions of ion flux and electric field near the deposition sites. Simultaneously, the intermediate phase and black phosphorus matrix effectively balance the charge transfer and ion diffusion during the electrodeposition process, enabling flat magnesium deposition rather than detrimental 3D hemispherical growth. As a result, the black phosphorus-modified magnesium anode demonstrated an extended stable cycle life of 1700 h at 2 mA cm-2 and 2 mAh cm-2 and increased specific areal current/capacity tolerance to 60 mA cm-2/60 mAh cm-2. Magnesium full cells assembled with the black phosphorus-modified magnesium anode and Mo6S8 cathode exhibited stable cycling performance with a low-capacity decay rate of 0.03% per cycle over 800 cycles at 5 C.