Multiwalled Carbon Nanotube Electrodes for Electrical Double Layer Capacitors with Ionic Liquid Based Gel Polymer Electrolytes

Multiwalled carbon nanotube (MWCNT) based electrical double-layer capacitors (EDLCs) using ionic liquid incorporated magnesium ion conducting gel polymer electrolytes were constructed and characterized. For comparison, three electrolytes were used to fabricate EDLCs comprised of a room-temperature ionic liquid 1-ethyl-3-methyl-imidazolium trifluoromethanesulfonate (EMITf) or a solution of magnesium salt (magnesium trifluoromethanesulfonate or Mg triflate) in EMITf or a solution of magnesium salt in the mixture of EMITf and a cosolvent of ethylene carbonate (EC):propylene carbonate (PC), immobilized with poly(vinylidene fluoride-hexafluoropropylene). The comparative performance characteristics of the EDLCs based on impedance analysis, cyclic voltammetry, and galvanostatic charge–discharge tests for numerous cycles were presented. The role of magnesium ions and the EC:PC cosolvent incorporated in the gel electrolytes was important in the dramatic improvement of the EDLCs' performance. The optimum capacitance value of (equivalent to the single electrode specific capacitance of of MWCNTs) was achieved for the EC:PC and the ionic liquid incorporated gel electrolyte based EDLCs. This corresponded to the specific energy of and the high value of power density of . The EDLCs showed excellent cyclic performances for or even more.