A plastic battery from Hopkins team Promising: The plastic battery may have great commercial potential.

November 12, 1996|By Greg Schneider | Greg Schneider,SUN STAFF

It may be the age of plastic money, plastic explosives and plastic surgery, but here's something you probably hadn't thought of:

Plastic batteries.

Johns Hopkins University engineers have developed a plastic battery that is as thin as a credit card and even more flexible. The Air Force has been sponsoring the research in hopes of getting a lightweight, cheap and versatile power source for satellites and weapons.

But such a product could also have enormous commercial potential, a prospect sure to be boosted by today's announcement that Popular Science magazine deems the battery one of the top 100 new products, technology developments and scientific achievements of the year.

"The neat thing about it is that a plastic battery doesn't leak, so it doesn't pose the same environmental risks as a conventional battery," said Dawn Stover, science editor for the magazine.

"It's very lightweight, and because it's plastic the battery could actually be molded to fit the shape of a product."

Theodore O. Poehler, assistant provost for research at Johns Hopkins, has been working on the plastic battery for five years.

Earlier this summer, he and his team of researchers realized that they may finally have found the right approach.

A conventional battery uses metals for its two electrodes -- the positive anode and negative cathode -- and usually a caustic liquid for the electrolyte that carries the current between them.

The Johns Hopkins battery uses two sheets of plastic with a plastic gel in between.

Called polymers, the plastics are made of long chains of molecules that contain elements capable of carrying an electrical charge.

So far, the Hopkins team has made batteries about the size of a business card that produce 2.5 volts.

To get more capacity, they can make the sheets bigger or stack them.

A lot of research remains, but the Johns Hopkins team is patenting the process and is in early discussions with battery companies interested in licensing the technology.

"As far as we're aware, there's never been anybody who made an all-polymer or all-plastic battery," Poehler said. "We've shown we have capacities which are at least beginning to become comparable to some of the commercial battery systems."

The right polymer

It may seem like an esoteric advancement -- batteries, after all, are already pretty versatile -- but the notion of a plastic battery has been pursued for years. The trouble was finding the right kind of polymer to carry the positive charge.

"When we started five years ago, we thought, gee, that should be easy," Poehler said. "Ha! It isn't so easy."

It took about $1 million in Air Force research money, and the team tested almost endless combinations of materials.

Now that they appear to have solved the problem, the prospects for applying the technology seem almost boundless.

Strips of the plastic battery could be rolled into cylinders to replace ordinary AA batteries, for instance.

They could be recharged hundreds of times, and when discarded would put no heavy metals or harmful chemicals into the environment.

You could shape the Johns Hopkins battery into a plastic shell lining the interior of a satellite, freeing up the space and weight usually taken by a conventional battery.

"Even Walkmans, cellular phones -- you could design a battery to line the inside casing," said Peter G. Searson, a materials science and engineering professor who has been leading the research with Poehler.

The battery also has tested well at temperatures far lower than those that mean death for the average car battery.

And scientists at Johns Hopkins Applied Physics Laboratory are exploring ways to link the batteries to solar cells, so they can be recharged on spacecraft.

Long way to go

Poehler, Searson, researchers Yossef Gofer and Hari Sarker and a team of graduate assistants could see their work pay off if it hits the commercial markets in a few years -- though the university and their department would get most of any royalties. But there is a long way to go.

"I bought a package of triple-A batteries just yesterday," Poehler said.

"And I was looking on the package and it said, 'Best if used by 2001.' Now, they have some high expectations for shelf life. We have no test results on that."

Pub Date: 11/12/96

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