26

nanotimes News in Brief

and leaves tubes at the top into which PANI cathodes could also be drop-coated. An aluminum current collector placed on top of the array completes the circuit.

“The idea here is to fabricate nanowire energy storage devices with ultrathin separation between the electrodes,” said Arava Leela Mohana Reddy, a research scientist at Rice and co-author of the paper. “This affects the electrochemical behavior of the device. Our devices could be a very useful tool to probe nanoscale phenomena.”

The team‘s experimental batteries are about 50 mi- crons tall -- about the diameter of a human hair and almost invisible when viewed edge-on, Reddy said. Theoretically, the nanowire energy storage devices can be as long and wide as the templates allow, which makes them scalable.

The nanowire devices show good capacity; the researchers are fine-tuning the materials to incre- ase their ability to repeatedly charge and discharge, which now drops off after about 20 cycles.

“There‘s a lot to be done to optimize the devices in terms of performance,” said the paper‘s lead author, Sanketh Gowda, a chemical engineering graduate student at Rice. “Optimization of the polymer sepa- rator and its thickness and an exploration of different electrode systems could lead to improvements.”

Sanketh R. Gowda, Arava Leela Mohana Reddy, Xiaobo Zhan, and Pulickel M. Ajayan: Building Energy Storage Device on a Single Nanowire, In: NANO Letters, Vol. 11(2011), Issue 8, August 10, 2011, Pages 3329-3333, DOI:10.1021/nl2017042: http://dx.doi.org/10.1021/nl2017042

11-09 :: September 2011

An ultrathin battery / supercapacitor hybrid contains thousands of nano- wires, each of which is a fully functio- nal battery.

The Rice University lab of Pulickel Ajayan developed the device. © Jeff Fitlow