ABSTRACT
Electrical energy can be stored either chemically, for example, batteries, or physically, for example, capacitors. Great efforts have been made in the last few decades to combine the high energy-storage capability of conventional batteries and the high-power-delivery capability of conventional solid-state capacitors, resulting in the invention of electrochemical double-layer capacitors (EDLCs). Among diverse types of carbon nanotubes (CNTs), vertically aligned CNTs oriented perpendicularly to the current collectors are considered to be well suited to be used as active electrode materials in EDLCs. Capacitors, including EDLCs, in principle, have an excellent stability to be used for millions of cycles at a very high charge/discharge rate. The performance of vertically aligned carbon nanotubes (VACNT)-based EDLCs can be improved by an effective utilization of the oxidation process. The performance of VACNT-based EDLCs can be further improved by incorporating pseudocapacitive materials onto the CNTs.
