Ionic Liquid as an Effective Additive for Rechargeable Magnesium Batteries

The effect of the addition of an ionic liquid DEME·TFSI to an electrolyte solution of Mg(HMDS)2-MgCl2 in THF was studied electrochemically and spectroscopically. Reversible magnesium deposition/dissolution was achieved with the DEME·TFSI-modified electrolyte. This electrolyte shows higher ionic conductivity, and a linear relationship was observed between the ionic conductivity and the concentration of DEME·TFSI in THF solution of Mg(HMDS)2-MgCl2. Mg-Mo6S8 coin cells have also been successfully cycled using Mg(HMDS)2-MgCl2 electrolyte with the addition of DEME·TFSI. Raman and NMR spectroscopy suggest that DEME·TFSI facilitates magnesium deposition/dissolution by improving ionic conductivity of the electrolyte.