Nanotechnology promises to enable tiny, intricate circuits powering devices on any surface. But unless they’re harvesting energy from something like a heartbeat, the devices can only be as small as the smallest battery.
Now researchers at Rice University have combined the two, packing an entire lithium-ion battery into a single nanowire. The developers say it’s as small as such a device can possibly get.
Researchers led by Rice professor Pulickel Ajayan built a hybrid energy storage device, which serves as a battery and a supercapacitor. The first version sandwiched an electrolyte between a nickel/tin anode and a cathode made of a polymer called polyaniline. The cathode also served as a supercapacitor, storing lithium ions in bulk, as this writeup by Rice University explains. The prototype proved that lithium ions would move through the electrolyte and into the cathode.
Then Ajayan and colleagues incorporated this structure into a single nanowire, through a complicated process of etching and chemical washing. The goal is to make nanowires with ultra-thin separation between electrodes, so the device can remain as small as possible.
The completed wire-batteries are about 50 microns tall, which is roughly the diameter of a human hair, according to Rice.
For now, they can only charge and discharge about 20 times before they die, but researchers are trying to optimize them to last longer. The research is published in the journal ACS Nano Letters.