The Improvement of Mg Plating/Stripping Reaction in Mg(N(CF₃SO₂)₂)₂/glyme Solutions by the Insoluble Additive with Oxymagnesium Halide Group

Modified silica with the oxymagnesium halide group is synthesized and used as the insoluble additive for Mg secondary battery electrolytes. The coulombic efficiency of Mg plating/stripping reaction in Mg(N(CF 3 SO 2 ) 2 ) 2 /glyme (Mg(TFSA) 2 /glyme) solution is improved from 10% to over 80% and Mg stripping overvoltage almost disappears. In addition, the open circuit potential of Mg substrate reduces to 0.2 V (vs Mg 2+ /Mg). Therefore, the modified silica will act not only as the dissociation promotor to Mg(TFSA) 2 salt, also play as the surface film remover on Mg substrate. The morphology of the plated Mg maintains to be particulate, contrary to the alumina additive cases we previously reported. From the results, we conclude that the modified silica will be the promising additive to Mg(TFSA) 2 /glyme solutions for the practical use in Mg secondary batteries.