(70i) Spherical Carbon Nanotube Assemblies and Their Supercapacitor Application
Macroscopic morphology of carbon nanotubes (CNTs) was designed using emulsion droplet confinement. Spherical CNT assemblies, were produced by the evaporation of CNT-dispersed aqueous emulsion droplets in oil. CNT was packed by the capillary pressure. With changing the concentration of CNT dispersion, the size of spherical CNT assemblies could be controlled. Average size of spherical CNT assemblies ca. 10 μm with BET specific area of 200m2/g. The spherical CNT assemblies were heat-treated to remove residual solvent. When heat-treat at high temperature, the surface oxygenated groups were decomposed. CNT spherical particle-assembled film was applied to a supercapacitor. The specific capacitance of 500°C treated sample was 80F/g, a higher temperature decreased the capacitance with decreasing the pseudo-capacitance. Comparing with CNT films, the spherical CNT particle electrode showed 40% higher specific capacitance with higher rate performance, attributed to the compact packing of CNTs and spherical particles and the hierarchical porous structures in the assemblies.