Nanowire battery

Proving that batteries have a little juice left in them yet, researchers at Rice University have built a rechargeable battery inside a single nanowire that’s 150nm (0.15 micron) in diameter. The researchers haven’t built just one, either: they’ve created an entire centimeter-scale array of thousands of nanowire batteries. Each nanowire is a completely discrete battery, consisting of all the usual elements: anode, cathode, and electrolyte.

The best way to understand how a nanowire battery works is to look at the image below, and then read the following words. They started with a layer of copper (the golden layer at the bottom). Using electrodeposition (electroplating) nickel/tin anodes are “grown” from the bottom copper plate, and then drop-coated with a polymer gel (polyethylene oxide) that both acts as an insulator between the nanowires and as the electrolyte. A second polymer (polyaniline) is then drop-coated to create the cathode, and a layer of aluminium is placed on top to complete the circuit. All in all the entire battery is about 50 microns tall; the width of a human hair, and almost invisible side-on.

Nanowire battery

For now this nanowire battery shows “good capacity” (though no exact figures are given), but it can only be recharged 20 times until its capacity starts to drop off. In theory though, the ultra-thin gap between cathode and anode should make for very strong and efficient batteries. The nanowire device is also very scalable; there’s no theoretical limit on how large a sheet of nanowire batteries you can string together — and given they’re only 50 microns thick, you could stack hundreds of layers together to create batteries of unrivaled power density.

This news comes just a few days after Yi Cui of Stanford University showed off a transparent battery — and curiously, Yi Cui is also one of the pre-eminent researchers when it comes to nanowire batteries. While transparent batteries will be useful for consumer-oriented gadgets, nanowire batteries are more significant because they can power nanobots. To power tiny devices you need tiny batteries, and that’s exactly what nanowire batteries are. If you like the concept of whole fleets of nanobots fixing and cleaning bridges and buildings (and spaceships), then nanowire batteries are what we need. Likewise, if you one day want a swarm of nanobots coursing through your blood and acting as platelets, white blood cells, and generally acting as groundskeepers, then this invention from Rice University is very exciting indeed.

Read more at PhysOrg