In nonaqueous Mg batteries, inactive adsorbed species and the passivation layer formed from the reactive Mg with impurities in the electrolyte seriously affect the Mg metal/electrolyte interface. These adlayers can impede the passage of Mg2+ ions, leading to a high Mg plating/stripping overpotential. Herein, we report the properties of a new additive, bismuth triflate (Bi(OTf)3), for synthesizing a chlorine-free Mg electrolyte to enhance Mg plating/stripping from initial cycles. The beneficial effect of Bi(OTf)3 can be ascribed to Bi/Mg3Bi2 formed in situ on the Mg metal surface, which increases the charge transfer during the on-off transition by reducing the adsorption of inactive species on the Mg surface and enhancing the resistance of the reactive surface to passivation. This simple method provides a new avenue to improve the compatibility between the Cl-free Mg electrolyte and the Mg metal anode.
Keywords: Mg interface; conditioning free; low overpotential; magnesium battery; magnesium−bismuth.