Performance of ionic liquid–based quasi‐solid‐state hybrid battery supercapacitor fabricated with porous carbon capacitive cathode and proton battery anode

Abstract The present paper reports preparation, characterization, and application of proton‐conducting ionic liquid–based gel polymer electrolyte (ILGPE) obtained by immobilizing liquid electrolyte solution (0.3M NH 4 Tf in EMIMTf) to the polymer PVdF‐HFP. These ILGPE offer excellent ionic conductivity ~1.30 × 10 −2 S/cm at room temperature and used as separator membrane in the hybrid BatCap. DSC study confirms glass transitions and melting temperatures ( T g 's and T m 's) of PVdF‐HFP/EMIMTF/NH 4 Tf decrease with increasing content of liquid electrolyte to the host polymer matrix PVdF‐HFP which, in turn, is responsible for increasing flexibility of membranes. Ionic transport number measurements ( t ion ~0.99, ~0.27) reveal that ions are the principal charge carriers in the present electrolyte system. The linear sweep voltammetry analysis shows the electrochemical stability window (ESW) of ILGPE film “PVdF‐HFP/EMIMTf/NH 4 Tf” is ~3.35 V. Two different hybrid BatCap cells are prepared with activated carbon and MWCNTs as a capacitive electrode (cathode) and ZnSO 4 ·7H 2 O battery anode. The performance of the BatCaps is estimated using cyclic voltammetry and galvanostatic charge‐discharge techniques. The discharge capacity was observed ~2.4 and 17.2 mAh/g for Cell#1 and Cell#2, respectively, at the current load of 0.5 mA/cm 2 . After the initial fading (~20%), BatCap cells show stable performance up to 100 cycles.