A high performance flexible gel polymer electrolyte incorporated with suberonitrile as additive for quasi-solid carbon supercapacitor

We report a novel composition of a free-standing, flexible gel polymer electrolyte (GPE) film comprising a polymer poly(vinylidine fluoride-co-hexafluoropropylene) (PVdF-HFP), immobilizing a solution of lithium bis (trifluoromethane sulfonyl)imide in suberonitrile for use in quasi-solid-state carbon supercapacitor. Physicochemical properties, characterized by SEM, X-ray diffraction, FTIR, and TGA/DSC along with its high ionic conductivity (sigma(RT) -1.2 x 10(-3) S cm(-1)) and wide electrochemical stability window (similar to 4.23 V versus Ag) make the GPE a potential electrolyte/separator for supercapacitors. Quasi-solid-state symmetrical supercapacitor has been assembled using the suberonitrile-based-GPE and activated carbon electrodes derived from a waste -biomass (pinecone). The supercapacitors are tested by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge. The capacitor offers specific capacitance of 220-230 F g(-1), which corresponds to high specific energy and power (27-32 Wh kg(-1) and 12.5-13.5 kW kg(-1), respectively). The device shows excellent cyclic performance for similar to 20000 charge-discharge cycles with similar to 10% initial fading and a safe performance over a wide temperature range.