<i>In situ</i> growth of carbon nanotubes in biomass carbon for energy storage: The denser the better?

Abstract

Carbon nanotubes (CNTs) and their allotropes have been regarded as promising materials for electric double-layer supercapacitors (EDLCs). It is well accepted that the higher surface area of carbon will enable a higher capacity of energy storage. An interesting question is what could happen if the half channel size is less than the Stern layer spacing. In this study, we grew CNTs into carbonized basswood for EDLCs, in which the CNT density varied in bass carbon sheets with different thicknesses, eventually giving various pore/channel sizes. Electrochemical analyses revealed that the bass carbon with a higher CNT density exhibits inferior performance compared to specimens with lower CNT densities. Further investigation through electrochemical impedance spectroscopy suggests that such anomalous behavior in energy storage is attributed to the restricted ion diffusion within the densely packed CNTs in bass carbon channels.