Conjugated polyfluorene imidazolium ionic liquids intercalated reduced graphene oxide for high performance supercapacitor electrodes

We report a new concept of using conjugated polyfluorene imidazolium ionic liquids (PILs) intercalated reduced graphene oxide for high performance supercapacitor electrode materials. Two polyfluorene homo-polymer (hoPIL) and co-polymer (co-PIL) carrying hexyl imidazolium bromide side chains were designed and synthesized. Their corresponding intercalated reduced graphene oxide materials hoPIL-RGO and coPIL-RGO exhibited good electrochemical performance in aqueous electrolytes as well as in ionic liquid electrolyte 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4). High specific capacitances of 222 F g(-1) at a current density of 0.2 A g(-1) and 132 F g(-1) at 0.5 A g(-1) were obtained for coPIL-RGO in 6 M KOH and BMIMBF4 accordingly. When assembled into a symmetric two-electrode cell with graphene materials as electrodes and BMIMBF4/acetonitrile (1:1) as electrolyte, an energy density of 14.7 Wh kg(-1) was obtained for coPIL-RGO at a current density of 0.5 A g(-1), and a maximum power density of 347 kW kg(-1) was achieved for hoPIL-RGO at a current density of 5 A g(-1) with good cycling stability. (C) 2014 Elsevier Ltd. All rights reserved.