Effect of carbon particle size on electrochemical performance of EDLC

The effect of particle size on the electrochemical performance of electrical double-layer capacitors (EDLCs) has been studied using carbon derived from silicon carbide powders with 20 nm to 20 mu m grains at temperatures from 800 to 1200 degrees C. For the same synthesis temperature, similar pore texture and microstructure of carbide-derived carbons produced from different powders have been observed. Nanoparticles exhibited a slight porosity modification with a larger pore volume (1.8 cc/g) and surface area (1300 m(2)/g) as compared to micrometer particles (0.4 cc/g and 1100 m(2)/g). Capacitances as high as 135 F/g associated with a small resistance and time constant have been reached for nano- and sub-micrometer particles synthesized at low temperatures and tested in a tetraethylammonium tetrafluoroborate in acetonitrile solution. This result suggests that small particles facilitate the migration of the ions inside the porous electrodes, allowing them to reach the whole pore volume due to a shorter transport distance within the particle. (c) 2008 The Electrochemical Society.