MG2+ ION BEHAVIOR IN IONIC LIQUIDS

The behavior of the Mg ion in ionic liquids is characterized in this paper. High ionic conductivity and electrochemical stability is observed for ionic liquids composed of a 1,2-dimethyl-3-n-R-imidazolium cation (R = propyl (MMPI) and butyl (MMBI)) and a bis(trifluoromethanesulfonyl)-imide (TFSI) anion containing Mg(TFSI)(2). The ionic liquids containing the Mg ion are also used to create solid polymer gel electrolytes using PVdF-HFP. The ionic conductivity of the TFSI-based ionic liquids, in both liquid form and solid gel, ranges from 1-3 mS/cm at room temperature. Electrochemical measurements indicate that the Mg ion is readily intercalated and de-intercalated from graphite, with charge/discharge efficiencies typically above 80%. X-ray diffraction analysis indicates a difference of only 1 angstrom in the c-axis expansion of the graphite when intercalated with the imidazolium cation or the Mg ion and the imidazolium cations. This indicates that co-intercalation of the Mg ion and the imidazolium cation is occurring.