Supercapacitors, also known as an electrochemical capacitor, is attracting considerable attention because of properties like high power density, rapid charge-discharge rate, long cycle life (&gt;100000 cycles) and low maintenance cost. It can be an excellent candidate for energy storage in future flexible and stretchable electronic devices. However, designing freestanding binder-free electrodes with superior mechanical strength and suitable capacitance is still in the development stage. Graphene is one of the best candidates for supercapacitor electrode material, because of its properties, like, plentiful availability, high specific surface area (~2630 m2 g-1), high intrinsic electrical conductivity, and chemical stability. Vertically oriented graphene (VOG) sheets on conductive substrate can be a useful electrode for supercapacitor application. Exposed graphene sheets on the surface of graphite, increases the surface area of the electrode by order of magnitude and reduces the contact resistance since graphene sheets remain attached to the substrate. Here, we demonstrate a two-step, intercalation followed by exfoliation of graphite, synthesis route to directly grow vertically oriented graphene on the graphite substrate. Intercalation process increases interlayer spacing causing more and easy access to the electrode surface by electrolyte ions, thus reducing diffusion resistance. Anodization of graphite in 1 M H2SO4 leads to the growth of VOGs on a graphite substrate, a configuration called as exfoliated graphite (EG). EG not only act as a current collector but also has much higher surface area. The electroactive surface area, measured in aqueous solution with [Fe(CN)6]3-/4- as an electroactive probe, increases by more than three times compared to pristine graphite. EG shows superior capacitive performance in 1 M sodium sulfate aqueous solution. The capacitance increased from 0.05 F cm-2 for pristine graphite, to 1.34 F cm-2 (calculated from Cyclic voltammetry at a scan rate of 5 mV s-1) for EG.

Exfoliated graphite sheet with superior supercapacitive performance

256th National Meeting (2018)

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