Fabrication process and characterization of carbon nanotube/carbon nanocomposite for energy storage and conversion

Abstract

Over the past several decades, porous carbon has been recognized as a promising electrode material due to its low density, high electrical conductivity, mechanical stability, high surface area, chemical inertness, and relatively low cost. Previously, porous carbon was prepared from organic precursors, either natural or synthetic, which were carbonized and activated through a gasification process. However, these materials consisted of complex, intricate assemblies of distorted graphite-like nanocrystallites, with the consequent disadvantage that pore size uniformity and shape were typically difficult to control. An ideal electrochemical electrode requires both a large surface area for charge accumulation and an interconnected porous network with pores that are sufficiently accessible for electrolyte wetting and rapid ionic transport. Unfortunately, current commercially available activated carbon electrodes are microporous (less than 2 nm in pore diameter) and are not easily accessed by electrolyte ions. While microporous structures contribute to the charge storage capacity, mesoporous structures are more accessible to electrolytes and allow greater ion mobility. The mesoporous structure therefore allows for the delivery of a large quantity of energy at a high rate. Template-based methods have been considered the best for the synthesis of porous carbon materials with designed pore architecture and control over the pore size distribution. Activated carbon materials produced using this technique exhibit well ordered mesoporous structures with large specific volumes. However, the aggressive chemicals employed limit this approach to the production of stable graphitic carbon. Therefore, my research objective is a fabrication of highly mesoporous carbon nanofibers reinforced with carbon nanotubes and their applications for supercapacitor and Li-ion battery electrodes with high capacities. The strategy to obtain mesoporous carbon materials without using template m...