Brown engineers build a better battery -- with plastic
It's thin, light, flexible -- and plastic. Brown University engineers
have created a prototype polymer-based battery that packs more power than a
standard alkaline battery and more storage capacity than a double-layered
A description of the prototype is published in Advanced Materials.
"Batteries have limits," said Tayhas Palmore, an associate
professor in Brown's Division of Engineering. "They have to be recharged.
They can be expensive. Most of all, they don't deliver a lot of power.
In their experiments, Palmore and Song took a thin strip of gold-coated plastic film and covered the tip with polypyrrole and a substance that alters its conductive properties. The process was repeated, this time using another kind of conduction-altering chemical. The result: Two strips with different polymer tips. The plastic strips were then stuck together, separated by a papery membrane to prevent a short circuit.
The result is a hybrid. Like a capacitor, the sandwich of thin layers
of different materials including PPy and plastic can be rapidly charged then
discharged to deliver power. Like a battery, this copolymer sandwich can store
and deliver that charge over long periods of time. During performance testing,
the new battery performed like a hybrid, too. It had twice the storage capacity
of an electric double-layer capacitor. And it delivered more than 100 times the
power of a standard alkaline battery.
Palmore said the new battery's form, as well as its function, is exciting. In width and height, it is smaller than an iPod Nano. And it's thinner, about as slim as an overhead transparency.
"You start thinking about this polymer and you start thinking that you can create batteries everywhere out of it," Palmore said. She went on to speculate that this material could be used to wrap cell phones and other electronic devices. Conceivably, you could even make fabric out of this composite," she suggested, without specifying what uses such material might have.
Palmore admitted that some performance problems such as decreased storage capacity after repeated recharging must be overcome before the device is marketable. But she expects strong interest. Battery makers are always looking for new ways to store and deliver power more efficiently. NASA and the U.S. Air Force are also exploring polymer-based batteries.
"What we've got is a good concept," Palmore said. "Put
electroactive molecules into conducting polymers and you can come up with all
sorts of interesting materials that store energy."
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