Characterization of ionic liquid added poly(vinyl alcohol)-based proton conducting polymer electrolytes and electrochemical studies on the supercapacitors

Abstract

The preparation of poly(vinyl alcohol) (PVA)/ammonium acetate (CH3COONH4)/1-butyl-3-methylimidazolium bromide (BmImBr) proton conducting polymer electrolytes is done by solution casting method. Upon inclusion of 60 wt.% of BmImBr, the maximum ionic conductivity of (9.29 ± 0.01) mScm−1 is achieved at ambient temperature. Ionic liquid added polymer electrolytes exhibit lower glass transition temperature (Tg), crystalline melting temperature (Tm) and crystallization temperature (Tc) than ionic liquid-free polymer electrolyte. The amorphous character of the most conducting polymer electrolyte has been proven using differential scanning calorimetry (DSC). Addition of ionic liquid not only extends the electrochemical potential window of the electrolyte, but also improves the thermal stability of the polymer electrolyte. Activated carbon/carbon black/carbon nanotube electrode is prepared and used in electrochemical double layer capacitors (EDLCs) fabrication. Based on the results, EDLC containing ionic liquid added polymer electrolyte exhibits better electrochemical properties. This EDLC possesses higher specific capacitance than that of supercapacitor comprising of ionic liquid free-based polymer electrolyte. The specific capacitance of 21.89 Fg−1 is obtained from cyclic voltammetry (CV). This value is in good agreement with EIS and galvanostatic charge–discharge findings. The EDLC remains stable upon 250 cycles of charging and discharging processes.