Enhanced capacitance of EDLCs (electrical double layer capacitors) based on ionic liquid-added polymer electrolytes

Abstract

Ionic liquid added PVA (poly (vinyl alcohol))-based ion conductors are investigated for EDLCs (Electric Double Layer Capacitors) using electrochemical measurements. Polymer electrolytes incorporated with ammonium acetate (CH3COONH4) as salt and 1-butyl-3-methylimidazolium iodide (BmImI) as the ionic liquid exhibit VTF (Vogel–Tamman–Fulcher) relationship, which is associated with free volume theory. ATR–FTIR (Attenuated Total Reflectance–Fourier transform infrared) confirms the occurrence of complexation between PVA, CH3COONH4 and BmImI. Thermal stability of the polymer electrolytes is studied using TGA (thermogravimetry analysis). The electrochemical potential window of ionic liquid-added polymer electrolyte is extended from 3.3 V to 3.8 V. CV (Cyclic voltammetry) proves the improvement in specific capacitance of the EDLC containing ionic liquid-added polymer electrolyte. The specific capacitance is found to decrease as the scan rate increases. The specific capacitance of EDLCs obtained in CV is in good agreement with low frequency-EIS (electrochemical impedance spectroscopy) and GCD (galvanostatic charge–discharge) curve. This system is suitable for EDLC owing to its high energy and power densities.