The Effect of Insoluble Oxide Additives on a Magnesium Plating/ Stripping Reaction in Mg(N(CF3SO2)2)2/Glyme Solutions

Mg(N(CF3SO2)2)2/glyme solutions are attractive as the electrolyte solution for Mg secondary batteries. However, the solutions are suffering from the poor reversibility and large overpotential of the Mg negative electrode. In the present study, we studied the effect of oxide particles on the Mg plating/ stripping reaction, aiming at the use as insoluble additives for Mg secondary batteries. By placing Al2O3 particles on the substrate, the Coulombic efficiency was improved from 5% to 33%. In addition, the overpotential for Mg stripping reaction drastically decreased from 1.5 to 0.2 V. The open circuit potential of the plated Mg maintained 0.2 V for 24 h. We applied Al2O3 additives on the cell consisting of Mg/V2O5 and achieved the discharge profile over 1.7 V, which was about 0.7 V higher than the similar report without additives. From the results, we first confirmed that Al2O3 functioned as insoluble additives for the Mg electrode reaction.