Performance of electric double-layer capacitors using carbons prepared from phenol-formaldehyde resins by KOH etching

Phenol-formaldehyde resins were used to produce carbons with different poro sities by KOH etching. Through the introduction of a binder, carbon-binder composites were prepared to serve as electrodes in electric double-layer ca pacitors. Nitrogen adsorption was used to characterize the porous structure of the carbons and electrodes. The performance of the capacitors in 1 M H2 SO4 was investigated with charge-discharge cycling experiments. The faradai c leakage current and the specific capacitance of the electrodes were found to increase with the specific surface area, while the resistance determine d from the IR drop showed an opposite trend. The increased electrode resist ance, which would probably result from the increased diffusion path in the pores upon etching, has caused a decrease in the capacitance per unit carbo n area. A specific capacitance larger than 100 F/g was achieved with an ele ctrode consisting of 80% carbon particles with a specific surface area of 1 900 m(2)/g and 20% polyvinylidenefluoride as the binder. (C) 2001 Elsevier Science Ltd. All rights reserved.