The current cutting edge of battery power for mobile devices
is with lithium polymer batteries, thanks to flexibility in different packaging
shapes. The battery of tomorrow, however, may not only be lightweight, thin and
flexible, but may also appear to be a plain sheet of paper.
Researchers at Rensselaer Polytechnic Institute recently published finding of a new energy storage device made almost entirely of the same
cellulose found in ordinary paper. What sets this new device apart from the
everyday item is that the paper is infused with carbon nanotubes, which act as
electrodes.
Details of the paper battery are explained in the article “Flexible
Energy Storage Devices Based on Nanocomposite Paper” published August 13 in the
Proceedings
of the National Academy of Sciences.
“It’s essentially a regular piece of paper, but it’s made in
a very intelligent way,” said the paper’s co-author, Robert Linhardt. “We’re
not putting pieces together – it’s a single, integrated device. The components
are molecularly attached to each other: the carbon nanotube print is embedded
in the paper, and the electrolyte is soaked into the paper. The end result is a
device that looks, feels, and weighs the same as paper.”
The battery’s physical attributes make it an attractive
technology for mobile devices such as cell phone, or for weight-sensitive applications
such as aircraft. The battery may be shaped into different forms without
affecting efficiency, and sheets may be stacked to boost capacity.
As the battery’s electrolyte, the researchers used a liquid
salt. As an alternative, the battery may also be activated by the electrolytes
found in human secretions and fluids, making the paper-thin battery a prime
candidate for being implantable inside the body.
“It’s a way to power a small device such as a pacemaker
without introducing any harsh chemicals – such as the kind that are typically
found in batteries – into the body,” noted co-author Victor Pushparaj.
As proof of their concept, the researchers have manufactured
a postage stamp-sized paper battery that can power a small fan or LED light.
