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Nanotechnology increases storage ability of capacitors

24 October 2015

Researchers report a significant improvement in the energy density of dielectric capacitors that make use of carbon nanotube embedded electrodes.

UD's Professor Bingqing Wei

In contrast to batteries, which offer high storage capacity but slow delivery of energy, capacitors provide fast delivery but poor storage capacity. A great deal of effort has been devoted to improving this feature (otherwise known as energy density) of dielectric capacitors; now, a group of researchers at the University of Delaware (UD) and the Chinese Academy of Sciences has successfully used nanotechnology to achieve this goal.

“With our approach, we achieved an energy density of about two Watts per kilogram, which is significantly higher than that of other dielectric capacitor structures reported in the literature,” says UD's Professor Bingqing Wei. 

“To our knowledge, this is the first time that 3D nanoscale interdigital electrodes have been realised in practice,” he adds. “With their high surface area relative to their size, carbon nanotubes embedded in uniquely designed and structured 3D architectures have enabled us to address the low ability of dielectric capacitors to store energy.”

One of the keys to the success of the new capacitor is an 'interdigitated' design — similar to interwoven fingers between two hands with 'gloves' — that dramatically decreases the distance between opposing electrodes and therefore increases the ability of the capacitor to store an electrical charge.

A diagram of the dielectric capacitor research

Another significant feature of the capacitors is that the new three-dimensional nanoscale electrode also offers high voltage breakdown, which means that the integrated dielectric material (alumina, Al2O3) does not easily fail in its intended function as an insulator.

“In contrast to previous versions, we expect our newly structured dielectric capacitors to be more suitable for field applications that require high energy density storage, such as accessory power supply and hybrid power systems,” Wei says. 

The work is reported in the open-access, online-only journal, Science Advances.

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