A newly developed, all-plastic battery uses polymers in place of conventional electrode materials and can generate 21/2 volts in cells that eventually may compete with existing 3-volt lithium models.
Thin, foillike plastic sheets form the cell's positive anode and negative cathode. The conductive electrolyte, a polymer gel film, is placed between the electrodes, holding the battery together.
``The gel electrolyte is based on polyacrylonitrile containing a salt called tetrabutylammonium tetrafluorborate,'' said Theodore Poehler, vice provost for research and a materials science and engineering professor at Johns Hopkins University in Baltimore. ``The polymer electrode materials are fluorophenylthiophenes polymerized on various substrates.''
Through its Rome, N.Y., laboratory, the U.S. Air Force Materiel Command initiated the project and, during five years, has invested about $1.1 million in the research at Hopkins.
The battery looks like a flat credit card, but a user can mold the cell into almost any size and shape for use in satellites and military gear and for small consumer devices such as hearing aids.
``Imagine using it in a large sheet form'' thinly covering a wall, said Peter Searson, a Hopkins materials science and engineering professor, ``or you could roll it up into a tube, like AA-size batteries.''
The cells can withstand hundreds of charges without degradation, but do not use hazardous liquids or the heavy metals found in nickel-cadmium rechargeables. Extreme temperatures do not change the battery's properties.
In a collaborative effort, Hopkins' Applied Physics Laboratory is linking the batteries with a solar-cell charging system.
While the battery technology lacks a military or commercial application now, the university owns the intellectual property rights and expects to negotiate licenses with manufacturers.