Christian Punckt - Supercapacitor Electrodes Produced through Evaporative Consolidation of Graphene Oxide-Water-Ionic Liquid Gels

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      Publication Details (including relevant citation   information):

      Pope, Michael A., Korkut, Sibel, Punckt, Christian, Aksay, Ilhan   A. 160 A1653-A1660-

      Abstract: We use colloidal gels of graphene   oxide in a water-ethanol-ionic liquid solution to assemble   graphene-ionic liquid laminated structures for use as electrodes   in electrochemical double layer capacitors. Our process involves   evaporation of water and ethanol yielding a graphene oxide/ionic   liquid composite, followed by thermal reduction of the graphene   oxide to electrically conducting functionalized graphene. This   yields an electrode in which the ionic liquid serves not only as   the working electrolyte but also as a spacer to separate the   graphene sheets and to increase their electrolyte-accessible   surface area. Using this approach, we achieve an outstanding   energy density of 17.5 Wh/kg at a gravimetric capacitance of 156   F/g and 3 V operating voltage, due to a high effective density of   the active electrode material of 0.46 g/cm(2). By increasing the   ionic liquid content and the degree of thermal reduction, we   obtain electrodes that retain >90% of their capacitance at a   scan rate of 500 mV/s, illustrating that we can tailor the   electrodes toward higher power density if energy density is not   the primary goal. The elimination of the electrolyte infiltration   step from manufacturing makes,this bottom-up assembly approach   scalable and well-suited for combinations of potentially any   graphene material with ionic liquid electrolytes. (C) 2013 The   Electrochemical Society. All rights reserved.

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