Ionic Liquid Enhanced Polymer Elcetrolytes for Environmental Friendly Electric Double Layer Capacitors

In this study we perform the preparation and characterization of poly (vinyl alcohol) (PVA)–added ionic liquid based ion conductors. The polymer electrolyte is incorporated with magnesium triflate [Mg(CF3SO3)2 or MgTf] as salt and 1–butyl–3–methylimidazolium bromide (BmImBr) as an environmental friendly ionic liquid. Differential scanning calorimetry (DSC) is carried out to investigate the glass transition temperature (Tg ), which is used to study the plasticizing effect of the ionic liquid. The polymer electrolyte with the lowest Tg gives the highest ionic conductivity value of (1.64±0.01) x 10-3 S cm-1 at 60 wt.% of BmImBr. This is attributed to the plasticizing effect of the ionic liquid, which increases the flexibility of the polymer backbone, hence increasing the ionic mobility and segmental motion of the ions. The highest conducting ionic liquid based polymer electrolyte is used to fabricate electrical double layer capacitors (EDLC). The electrochemical potential window is evaluated using linear sweep voltammetry (LSV). Electrochemical capacitance of the EDLC is evaluated through cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD). The electrochemical potential window of ionic liquid–added polymer electrolyte is extended from 1.35 V to 2.6 V. Cyclic voltammetry (CV) proves the improvement in specific capacitance of the electrical double layer capacitors (EDLCs) containing ionic liquid–added polymer electrolyte by increasing the specific capacitance from 1.41 Fg-1 in the ionic liquid free polymer electrolyte to 45.95Fg-1 for the 60 wt% ionic liquid added polymer electrolyte. Keywords: Poly(vinyl alcohol); Ionic liquid; Mg(CF3SO3)2 , EDLC; Capacitance