Grain‐Boundary‐Rich Triphasic Artificial Hybrid Interphase Toward Practical Magnesium Metal Anodes.

Magnesium metal anodes have attracted widespread attention for their high volumetric capacity and natural abundance, but are precluded from practical applications by poor rate capability and limited lifespan due to sluggish ion‐transfer kinetics and uneven deposition behavior. Herein, for the first time a grain‐boundary‐rich triphasic artificial hybrid interphase, consisting of Sb metal, Mg3Sb2 alloy, and MgCl2, is designed on Mg anode surface by a facile solution treatment method, enabling high‐rate and long‐cycle Mg plating/stripping behavior. The triphasic artificial hybrid interphase affords high magnesiophilicity and ionic conductivity to reduce the energy barriers for Mg2+ desolvation and deposition. Meanwhile, the abundant grain boundaries redistribute Mg2+ flux at the electrode‐electrolyte interface and guide uniform Mg deposition. Accordingly, the as‐designed Mg metal anode achieves ultralong cycling life of 350 h at a high current density of 5 mA cm−2 and a large areal capacity of 5 mAh cm−2, outperforming previously reported Mg metal anodes with artificial interphases. Full cells with Mo6 cathode also show extraordinary stability over a long lifespan of 8000 cycles at a high rate of 5 C. The rational artificial interphase design and the understanding of composition‐structure‐function relationships shed deep insights into the development of fast‐charging and long‐cycling Mg metal batteries. [ABSTRACT FROM AUTHOR]