Carbon-Based Supercapacitors Produced by Activation of Graphene

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Science  12 May 2011:
DOI: 10.1126/science.1200770


Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high surface area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a BET surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low O and H content. This sp2-bonded carbon has a continuous three-dimensional network of highly curved, atom thick walls that form primarily 0.6- to 5-nm-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.