Using KOH activation of microwave exfoliated graphite oxide (MEGO), a porous carbon (activated MEGO, or a-MEGO) with a BET surface area of up to 3100 m2/g, a high electrical conductivity, and a low oxygen and hydrogen content was obtained. This sp2-bonded carbon apparently has a continuous 3D network of highly curved, atom-thick walls that form primarily 0.6- to 5-nm-width pores. Two-electrode supercapacitor cells constructed with a-MEGO yielded gravimetric capacitance of up to 200 F/g (normalized to carbon) and energy density of above 20 Wh/Kg (normalized to a typical supercapacitor device) with ionic liquid electrolytes. The energy density can be further improved to more than 50 Wh/Kg by constructing a hybrid supercapacitor using Li-ion electrolyte. In addition, this 3D graphene can act as an efficient scaffold for hosting other active materials or was made as paper-like morphology for a very high power density. However, relatively low density of 3D graphene has challenged its real application in devices. Mechanical pressure was applied to consolidate the carbon, leading to a doubled mass density while the gravimetric capacitance remained about the same. Some recent processes in the field also suggest that a supercapacitor device with high volumetric performances could be achieved by designing and controlling the dimension at the microscopic scale in the carbons. The talk will also include the recent proceedings about the research using other carbon precursors for activation and thus the design of novel 3D carbons for high-performance energy storage.

Graphene materials for high-performance supercapacitors: 2D or 3D?

248th National Meeting (2014)

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