Engineers at Brown University have built a prototype of an hybrid plastic battery that uses a conductive polymer. The system, which marries the power of a capacitor with the storage capacity of a battery, can store and deliver power efficiently. For example, during performance testing, "it delivered more than 100 times the power of a standard alkaline battery." Still, it's unlikely that such a device can appear on the market before several years. But read more...
Here is how the idea of such an hybrid battery came from.
"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. Another option is capacitors. These components, found in electronic devices, can deliver that big blast of power. But they don't have much storage capacity. So what if you combined elements of both a battery and a capacitor?"
Palmore, who worked with Hyun-Kon Song, a former postdoctoral research associate at Brown, decided to use polypyrrole, a conductive polymer which led to the 2000 Nobel Prize in Chemistry.
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.
Below is a picture of the prototype of this new hybrid battery (Credit: John Abromowski/Brown University).
And how does this prototype deliver?
Like a capacitor, the battery can be rapidly charged then discharged to deliver power. Like a battery, it 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.
Still, this new battery, which is smaller than an iPod Nano, suffers from some performance problems -- "such as decreased storage capacity after repeated recharging" -- which need to be solved before such batteries arrive on the market.
For more information, this research work has been published by Advanced Materials under the title "Redox-Active Polypyrrole: Toward Polymer-Based Batteries" (Volume 18, Issue 13, Pages 1764-1768). Here is a link to the article if you're a registered reader of Wiley InterScience.
Sources: Brown University news release, September 13, 2006; and various web site
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