Carbon nanotube-based supercapacitors: Technologies and markets

Electrochemical double-layer capacitors (also known as supercapacitors or ultracapacitors) have tremendous potential as high-energy and high-power sources for use in low weight hybrid systems. Commercial applications for such devices include uninterruptible power applications, telecommunications, and public transportation. Electrodes based on carbon nanotubes (CNTs) offer exceptional power and energy performance due to the high surface area, high conductivity, and the ability to functionalize the CNTs to optimize capacitor properties. In this article, a team of researchers at Georgia Tech Research Institute report on the preparation of electrochemical capacitors incorporating CNT electrodes and their performance compared with existing commercial technology. Preliminary results indicate that substantial increases in both power and energy density are possible with further development. The authors discuss the effects of nanotube growth and processing methods, including purification and functionalization, on electrochemical capacitor performance. Finally, the authors review the compatibility of different CNTs and electrolytes by summarizing research focused on varying the type of electrolyte ions that accumulate on the high surface area electrodes.