Reversible deposition and dissolution of magnesium from BMIMBF4 ionic liquid

In this paper, we reported for the first time the highly reversible magnesium deposition and dissolution processes on silver substrate in the ionic liquid of BMIMBF4 with 1 M Mg(CF3SO3)2. Stable-state cycles with several millivolts against magnesium at 0.1 mA/cm2 can be obtained during repeated charge-discharge cycling at room temperature. The cyclic voltammograms also demonstrated reversible magnesium deposition-dissolution processes. Impedance measurements during steady-state Mg deposition represented low electrochemical impedance, though this resistance was high during the initial cycling. Scanning electron microscopy (SEM) results showed that porous Mg deposition became compact and crystalline and the deposited magnesium could be completely dissolved electrochemically, leaving clean and film free surface. The high reversibility of the electrochemical magnesium deposition will inspire us to speculate about the feasibility of secondary magnesium batteries with the electrolyte.