Investigation of electrochemical double-layer (ECDL) capacitors electrodes based on carbon nanotubes and activated carbon materials

The carbon nanotubes (CNT) show promising electrochemical characteristics particularly for electrochemical energy storage. The electrochemical double-layer (ECDL) capacitor is a new type of capacitor with features intermediate between those of a battery and a conventional capacitor. ECDL capacitors have been made using various types of CNT and activated carbon (a-C) as electrode material. The specific capacitance per surface area of the electrodes depends on the thickness and the specific surface area of the active material. The CNT electrodes show a specific capacitance from 0.8 and 280 mF cm−2 and 8 to 16 F cm−3, respectively. Increasing the mass density also helps to increase the capacitance. Commercially available activated carbon (a-C) electrodes were also tested in order to study their specific capacitance as a function of their physical properties. The various a-C electrodes have specific capacitance per surface area ranging from 0.4 to 3.1 F cm−2 and an average specific capacitance per volume of 40 F cm−3 due to their larger mass density.