Nanobattery as small as it gets

Developed by researchers at Rice University, Houston, a lithium ion energy storage device packed into a single nanowire is as small as a battery can get, according to a university news release heralding the 50µm-tall power source.

The illustration above depicts nanoscale battery and supercapacitor devices in an array. Schematic courtesy Dr. Pulickel Ajayan/Rice University.

The battery-supercapacitor hybrid device, as described in a recent issue of the American Chemical Society journal Nano Letters, is a sandwich-like device comprised of three layers—nickel/tin anode, polyethylene oxide (PEO) electrolyte and polyaniline (PANI) cathode, respectively.

The Rice research team was able to tuck the cathode inside the nanowires by using PEO as a gel-like electrolyte that stores ions and serves as an insulator, explained Dr. Pulickel Ajayan, who lead the project.

"Drop-coating the widened alumina pores with PEO coats the insides, encases the anodes and leaves tubes at the top into which PANI cathodes could also be drop-coated," the news release explained. "An aluminum current collector placed on top of the array completes the circuit."

The researchers are working to increase the ability of the materials to repeatedly charge and discharge, the university reported. At the moment, such capacity is said to drop 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 separator and its thickness and an exploration of different electrode systems could lead to improvements."

The Hartley Family Foundation, Rice University, National Institutes of Health, Army Research Office and Multidisciplinary University Research Initiative supported the research.