Performance Studies of Activated Charcoal Based Electrical Double Layer Capacitors with Ionic Liquid Gel Polymer Electrolytes

Symmetric electrical double layer capacitors (EDLCs) with ionic liquid based magnesium ion conducting gel polymer electrolytes and activated charcoal (AC) electrodes have been constructed and characterized. Comparative studies have been performed employing three different electrolytes to fabricate EDLCs consisting of ionic liquid l-ethyl-3-methyl-imidazolium trifluoromethanesulfonate (EMITf) or a solution of magnesium trifluoromethanesulfonate [Mg-triflate or Mg(Tf)(2)] in EMITf or solution of Mg-triflate in the mixture of EMITf and ethylene carbonate (EC)-propylen:, carbonate (PC) cosolvent, immobilized with poly(vinylidenefluoride-hexafluoropropylene) (PVdF-HFP) matrix. The performance characteristics of EDLCs based on impedance spectroscopy, cyclic voltammetry, and constant current charge discharge technique are presented. The incorporation of magnesium salt and EC PC cosolvent in gel polymer electrolytes play a significant role in the dramatic improvement of the EDLCs' characteristics. The optimum capacitance value of 136 F g(-1) of AC, which correspond to the specific energy of similar to 18.8 Wh kg(-1) and power density of similar to 6.67 kW kg(-1) have been achieved. The EDLCs show almost stable cyclic performance, after initial fading in capacitance, for 5000 charge-discharge cycles.