The electrochemical cycling performance of vanadium oxide nanotubes (VOx-NTs) for Mg-ion insertion/extraction was investigated in acetonitrile (AN) and tetramethylsilane (TMS)-ethyl acetate (EA) electrolytes with Mg(ClO4)2 salt. When cycled in TMS-EA solution, the VOx-NT exhibited a higher capacity retention than when cycled in AN solution. The significant degradation of capacity in AN solution resulted from increased charge-transfer resistance caused by the reaction products of the electrolyte during cycling. Mixed TMS-EA solvent systems can increase the cell performance and stability of Mg-electrolytes owing to the higher stability of TMS toward oxidation and the strong Mg-coordination ability of EA. These results indicate that the interfacial stability of the electrolyte during the charging process plays a crucial role in determining the capacity retention of VOx-NT for Mg insertion/extraction.
Keywords: capacity retention; magnesium-ion battery; mixture electrolytes; nanotube; tetramethylsilane; vanadium oxide.