We report a novel configuration of symmetrical electric double-layer capacitors (EDLCs) comprising a plastic crystalline succinonitrile (SN) based flexible polymer gel electrolyte, incorporated with sodium trifluoromethane sulfonate (NaTf) immobilised in a host polymer poly (vinylidine fluoride-co-hexafluoropropylene) (PVdF-HFP). The cost-effective activated carbon powder possessing a specific surface area (SSA) of ? 1700 m2g-1 containing a large proportion of meso-porosity has been derived from tea waste to use as supercapacitor electrodes. The high ionic conductivity (?3.6�10-3 S cm-1 at room temperature) and good electrochemical stability render the gel polymer electrolyte film a suitable candidate for the fabrication of EDLCs. The performance of the EDLCs has been tested by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge-discharge studies. The performance of the EDLC cell is found to be promising in terms of high values of specific capacitance (?270 F g-1), specific energy (? 36 Wh kg-1), and power density (? 33 kW kg-1).

Binderless electrodes of activated carbon monoliths (ACMs) and its composites with graphene are prepared by carbonization and activation of green monoliths consisting of self-adhesive carbon grains and 0�10�wt% KOH-treated graphene. Compared with ACMs, the optimized composite containing 6�wt% graphene exhibits more ordered micro-structures with increased crystallite height, and graphitic sp2 carbons (ID/IG�=�0.49 vs. 0.91) along with enhanced porosity; as revealed by X-ray diffraction, Raman, and N2 adsorption-desorption studies. These modifications lead to increased electrical conductivity (13 vs. 9�S�cm?1) through improved interconnections of carbon particles by graphene, and surface area�~�(800 vs. 456�m2�g?1) due to increased inter-particle spacing. Further, contrary to ACMs, the composite electrodes can offer faster delivery of energy in almost 50% less response time (5 vs. 8�s) due to reduced equivalent series resistance (1.67 vs. 2.65�?) and charge transfer resistance (0.55 vs. 1.33�?). � 2017, Springer-Verlag GmbH Germany.