Pulickel Ajayan has packed an entire lithium ion energy storage device into a single nanowire
Rice scientists build battery in a nanowire. Hybrid energy storage device is as small as it can possibly get
The world at large runs on lithium ion batteries. New research at Rice University shows that tiny worlds may soon do the same.
The Rice lab of Professor Pulickel Ajayan has packed an entire lithium ion energy storage device into a single nanowire, as reported this month in the American Chemical Society journal Nano Letters. The researchers believe their creation is as small as such devices can possibly get, and could be valuable as a rechargeable power source for new generations of nanoelectronics.
In their paper, researchers described testing two versions of their battery/supercapacitor hybrid. The first is a sandwich with nickel/tin anode, polyethylene oxide (PEO) electrolyte and polyaniline cathode layers; it was built as proof that lithium ions would move efficiently through the anode to the electrolyte and then to the supercapacitor-like cathode, which stores the ions in bulk and gives the device the ability to charge and discharge quickly.
The second packs the same capabilities into a single nanowire. The researchers built centimeter-scale arrays containing thousands of nanowire devices, each about 150 nanometers wide. A nanometer is a billionth of a meter, thousands of times smaller than a human hair.
"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 phenomenon."
The team's experimental batteries are about 50 microns 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 increase their ability to repeatedly charge and discharge, which now drops off after a 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 separator and its thickness and an exploration of different electrode systems could lead to improvements."
Rice graduate student Xiaobo Zhan is a co-author of the paper.
The Hartley Family Foundation, Rice University, National Institutes of Health, Army Research Office and Multidisciplinary University Research Initiative supported the research.