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Abstract: Flexible all-solid-state supercapacitors (SCs) are fabricated using graphene/carbon black nanoparticle (GCB) film electrodes and cross-linked poly(vinyl alcohol)–H2SO4 porous gel electrolytes (gPVAP–H2SO4). The GCB composite films, with carbon black (CB) nanoparticles uniformly distributed in the graphene nanosheets, greatly improve the active surface areas and ion transportation of pristine graphene film. The porous structure of as-prepared gPVAP–H2SO4 membrane improves the equilibrium swelling ratio in electrolyte and provides interconnected ion transport channels. The chemical crosslinking solves the fluidity problem of PVA–H2SO4 gel electrolyte at high temperature. As-fabricated GCB//gPVAP(20)–H2SO4//GCB flexible SC displays an increased specific capacitance (144.5 F g−1 at 0.5 A g−1) and a higher specific capacitance retention (67.9% from 0.2 to 4 A g−1). More importantly, the flexible SC possesses good electrochemical performance at high temperature (capacitance retention of 78.3% after 1000 cycles at 70 °C). [Copyright &y& Elsevier]

Abstract: Graphene single nanosheet (GNS) is synthesized from graphite by chemical oxidation and thermal exfoliation at 1000 °C and confirmed by X-ray diffraction analysis. Scanning electron and transmission electron microscope images clearly show the lateral expansion of graphite sheet and uniform dispersion of Pt nanoparticles on GNS. Fourier transform infrared and X-ray photoelectron spectroscopy analyses are conducted for surface properties of GNS such as oxygenated functional groups. Cyclic voltammetric analysis shows that electrochemical active surface areas (ECSAs) for Pt/GNS, commercial Pt/Vulcan XC-72 carbon black and Pt-incorporated onto commercial carbon black (Pt/CB) prepared in the laboratory are 33.1 m2 g−1, 23.5 m2 g−1 and 22.5 m2 g−1, respectively. Because of significant restacking of Pt/GNS sheets, carbon black (CB) with different content is intercalated between Pt/GNS as a spacer. The ECSAs of Pt/GNS, Pt/GNS/CB20, Pt/GNS/CB30 and Pt/GNS/CB40 are evaluated to be 31.5 m2 g−1, 28.6 m2 g−1, 38.8 m2 g−1 and 30.4 m2 g−1, respectively. The cell performance highly depends on CB content and Pt/GNS/CB with 30 wt.% of CB content shows the best cell performance of 400 mA cm−2. [Copyright &y& Elsevier]