By Fred Vogelstein

(FORTUNE Magazine) – Mountain View, Calif. Founded 2000

Batteries have long been the high-tech world's weakest link. While processors, memory, and screens in cellphones, PDAs, and laptops all get cheaper and better at exponential rates, battery life in some devices is actually getting worse. There's a reason for that. Better processors, memory, and screens require more power, but the chemicals that generate that power inside today's batteries simply can't produce any more. PolyFuel, a startup spawned four years ago by SRI International and run by 45-year-old fuel-cell veteran Jim Balcom, thinks it has the answer. It makes fuel-cell membranes: plastic-wrap-like sheets that combine with methanol from replaceable cartridges to generate enough electricity to power a cellphone, iPod, or laptop roughly three times longer than batteries. What PolyFuel lacks in sales (it has none to date) it makes up in big backers and buzz. Based on nearly two decades of work at SRI, the company has raised $21.6 million from Intel Capital and Mayfield, among others. Toshiba, Samsung, NEC, and other manufacturing giants are testing its technology in battery prototypes for laptops and cellphones. --F.V.