Electric Double Layer and Interface Chemistry Regulated by Silicon Trifluoromethanesulfonate for Magnesium Electrolyte at High Current Density of 20 mA cm –2

To address the practicality of MgCl 2 -based electrolytes, the multifunctional additives trifluoromethanesulfonic esters are for the first time proposed to cooperatively improve the solubility, and regulate the electric double layer and interface chemistry through the strong electronegativity of the leaving group -OTf, the adsorption mechanism, and favorable Si–C SEI layer. With the additive of (trimethylsilylmethyl) trifluoromethanesulfonate, the MgCl 2 -based electrolyte exhibits outstanding cycling performance and rate capability. The as-assembled Mg||Mg cell displays a very low overpotential of 90 mV and a long lifespan of 2100 h at 0.5 mA cm –2 and 0.25 mAh cm –2 . Remarkably, it can operate at an ultrahigh current density and a medium areal capacity of 20 mA cm –2 and 1 mAh cm –2 . This work affords an effective strategy of regulating electric double layer and interface chemistry for designing a low-cost, high-power magnesium battery electrolyte by Si–C-containing trifluoromethanesulfonic esters.