Effect of ionic liquid 1-butyl-3-methylimidazolium bromide on ionic conductivity of poly(ethyl methacrylate) based polymer electrolytes

Polymer electrolyte films comprising poly(ethyl methacrylate) (PEMA) as host, Magnesium Triflate [Mg(CF3SO3)(2) or MgTfj as salt and 1-butyl-3-methylimidazolium bromide (BmlmBr) as the ionic liquid are prepared. Upon addition of BmlmBr, the ionic conductivity shows a perceptible increase. Highest ionic conductivity of (1.80 +/- 0.01) x 10(-4) S cm(-1) is obtained for the polymer electrolyte with 40 wt% ionic liquid at ambient temperature. Temperature dependent ionic conductivity studies are performed to elucidate the mechanism of ion transport and it is found that the system obeys the Vogel-Tamman-Fulcher (VTF) mechanism. Differential Scanning Calorimetry (DSC) is carried out to investigate the glass transition temperature (T-g) and as expected, ionic liquid added polymer electrolytes exhibit lower glass transition temperature (T-g), than ionic liquid-free polymer electrolyte, proving the amorphous nature of the ionic liquid added polymer electrolyte. The sample with the highest ionic conductivity is used to fabricate Electrical Double Layer Capacitors (EDLC). Cyclic Voltammetry analysis shows that specific capacitance of the ionic liquid added polymer electrolyte is found to be higher than the polymer electrolyte without ionic liquid, which proves the plasticizing effect of ionic liquid on the polymer electrolyte.