High Energy Density Carbons for Electrochemical Capacitors

The development of compact, light-weight, highly portable power sources with improved energy and power densities represent an ongoing challenge for the mission requirements of the U.S. Marine Corps. Current research by the Office of Naval Research is geared towards the development of a lighter weight alternative to the standard BA-5590 military primary battery, employing standard metal/air technology. However, the power density of the metal/air battery technology remains too low to meet all mission requirements which require high power pulses. The combination of a energy-dense metal/air battery with a high power density electrochemical double layer capacitor (EDLC) or asymmetric EDLC could provide the necessary pulse power requirements to overcome the peak power limitations of the metal/air system. Research performed at CAER has focused on the development of energy-dense mesoporous activated carbons with size-calibrated pores for double layer charge storage. The proposed approach is to increase surface roughness and create usable external surface area by catalytic drilling of metal or metal oxide nanoparticles from the surface into the interior of the carbon precursor (i.e. pore formation) prior to or during activation. Preliminary results support the validity of this experimental approach, as various carbons have been prepared with a gravimetric capacitance of ~ 80-100 F/g, along with SBET < 1100 m2/g, approximately half of the typical total surface area of commercial EDLC carbons. Further exploration and development of this approach will yield energy-dense activated carbons suitable for symmetric and/or asymmetric EDLCs to alleviate power limitations of the metal/air battery.