This is an extract of an article originally published in AMMRF News, Vol. 25, March 2014.
Supercapacitors to fuel the future
Supercapacitors are an emerging technology that can store far more energy than traditional capacitors yet release it quickly. They can repeat this many times without loss of storage capacity. One disadvantage of state-of-the-art supercapacitors is their relatively high fabrication cost compared with lithium-ion batteries.
Researchers at the University of New South Wales (UNSW) are investigating a new material for superconductors: exceptionally thin sheets of cobalt oxide (Co3O4).
It is known that only the surface-most atoms of active electrode materials play a key role in the supercapcitor function, and that the electrochemical activities of electrodes are closely related to their microstructures. Therefore manipulating those microstructures enables the design of better materials specifically for energy conversion and storage. A range of different Co3O4 morphologies, including nano-spheres, nano-needle and nano-sheets, have been successfully fabricated and reported so far. However, among such morphologies, it is the porous Co3O4 nano-sheets, attached to their supporting material by their edges, which show the greatest capacitive behavior.
The high fabrication cost of current super-capacitors is due primarily to their graphene support. Although carbon is cheap and available, it is demanding and costly to make it into graphene, a single-atom layer form of carbon. Porous carbon foam, with the same excellent electric properties as other carbon-based materials, could therefore be an ideal replacement. Owing to its network of tiny holes all through the structure, similar to a sponge, porous carbon foam provides large surface area on which the supercapacitive material can be deposited.