Published online by Cambridge University Press: 10 May 2016
In this work, ionic liquid gel polymer electrolyte is used to fabricate solid-state hybrid supercapacitors with microporous PEDOT and graphene asymmetric electrodes. The PEDOT electrode was prepared by ultra-short pulsed current electro-polymerization over flexible graphite sheets. The graphene electrode of 600 m2g-1 surface area was formed by slurry coating using graphene platelets of thickness 8 nm and size <2 μm. The ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4) was mixed with poly(vinylidene fluoride-hexafluoropropylene) P(VdF-HFP) to form gel electrolyte. The quasi rectangular cyclic voltammetry (CV) plots in the voltage range -0.2 to +2.0V and the charge-discharge (CD) curves show highly capacitive behavior. The optimized 0.1M LiClO4 doping of IL gel electrolyte increases specific capacitance to 70.4 mF.cm-2. Increase in IL electrolyte thickness from 30 to 54 µm improves discharge capacitance from 10.6 to 23.3 mF.cm-2 and energy density from 2.90 to 5.86 Wh.kg-1. Hybrid solid-state supercapacitor has a flat stackable platform which easily integrates with solar cell module for direct storage of solar electricity. This paper describes the electrode synthesis, design and electrochemical properties of PEDOT/graphene hybrid supercapacitor and the charging characteristics by solar cells for evaluating energy storage performance in backing up the solar cell generated electricity.