A Passivation-Free Solid Electrolyte Interface Regulated by Magnesium Bromide Additive for Highly Reversible Magnesium Batteries.

Highly reversible Mg battery chemistry demands a suitable electrolyte formulation highly compatible with currently available electrodes. In general, conventional electrolytes form a passivation layer on the Mg anode, requiring the use of MgCl additives that lead to severe corrosion of cell components and low anodic stability. Herein, for the first time, we conducted a comparative study of a series of Mg halides as potential electrolyte additives in conventional magnesium bis(hexamethyldisilazide)-based electrolytes. A novel electrolyte formulation that includes MgBr showed unprecedented performance in magnesium plating/stripping, with an average Coulombic efficiency of 99.26% over 1000 cycles at 0.5 mA/cm and 0.5 mAh/cm. Further analysis revealed the formation of a robust Mg anode-electrolyte interface, which leads to dendrite-free Mg deposition and stable cycling performance in a Mg-MoS battery over 100 cycles. This study demonstrates the rational formulation of a novel MgBr-based electrolyte with high anodic stability of 3.1 V for promising future applications.