Effect of cotton fiber addition and carbonization temperature to the structural-and-surface-property change of C/C composite xerogels as electrodes for electric double layer capacitors

Abstract

Carbon/carbon (C/C) composites containing micropores, mesopores and macropores as trimodal structure are a class of promising electrode materials for electric double layer capacitors. The existence of cotton fibers can change pore structure, electrical resistance and surface properties of C/C composites by the increase of carbonization temperature. In this work, C/C composite xerogel electrodes possessing trimodal structure were prepared from resorcinol, formaldehyde, and cotton fibers. Sufficiently high carbonization temperatures had to be reached to obtain electrodes possessing high electrical double layer capacitance. The addition of cotton fibers lowered effective carbonization temperatures and created macropores, which facilitated transport of carbonization gases and heat transfer in pores located deep in the samples. Cotton fibers also prevented collapse of mesopores during vacuum drying. Samples with cotton fibers added had 27–40% more mesopore volume. The highest specific capacitance obtained was 175 F g−1 during discharge at 0.5 A g−1.