Renewing bonds to recharge batteries.

Renewing bonds to recharge batteries

Building a better mousetrap isn't the only way to get the world to beat a path to your door. A better battery might do it, too.

The Lawrence Berkeley (Calif.) Laboratory last week announced efforts to develop a new energy-cell technology that it says could become the basis for rechargeable, lightweight batteries that outlast, outpower and underprice any battery commercially available or under development.

Battery researchers elsewhere call the new technology inventive and promising, but caution it still could fall short of its makers' rosy projections. "These things are witches' brews," says electrochemist Gregory C. Farrington of the University of Pennsylvania in Philadelphia in describing the uncertainties of new battery technologies.

Most batteries have positive (anode) and negative (cathode) electrodes at which electrochemical reactions transform chemicals into electrical energy. Crucial differences lie in the materials that make up the electrodes and in the chemical reactions these materials dictate. These differences affect manufacturing costs, energy output and other measures of battery performance.

Like the anodes of existing "coin cells" used in watches, the new battery's anode is made of lithium. Its cathode, however, resembles no other. Rather than using inorganic cathode materials as do most lithium-battery makers, Lutgard C. De Jonghe and his colleagues use carbon-based chemicals known as organosulfur polymers. When the battery produces current, the anode sheds positively charged lithium ions that travel through a membrane within the battery to the polymer-loaded cathode, and simultaneously releases electrons that get to the same place through an external loop. The electrons progressively break the sulfur-sulfur bonds linking the chain-like polymers' molecular subunits, and the lithium ions stick to each newly formed, negatively charged end. Running electricity through the cell backwards recharges the battery by regenerating the polymer and pushing lithium ions and electrons back into the anode. De Jonghe says his group has run small prototype batteries through hundreds of such cycles. Commercially available lithium batteries are not rechargeable.

"The impact is potentially very broad and even could make electric vehicles practical," he says. But before the batteries becomes a big item, someone has to figure out how to mass-produce them, he adds.