Cycling Stability of a VO Nanotube Cathode in Mixture of Ethyl Acetate and Tetramethylsilane-Based Electrolytes for Rechargeable Mg-Ion Batteries.

The electrochemical cycling performance of vanadium oxide nanotubes (VO-NTs) for Mg-ion insertion/extraction was investigated in acetonitrile (AN) and tetramethylsilane (TMS)-ethyl acetate (EA) electrolytes with Mg(ClO) salt. When cycled in TMS-EA solution, the VO-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 VO-NT for Mg insertion/extraction.