Flat Battery: It Works On Paper

By Mark Halper

If saving bits of energy and environment here and there add up, then Finland's Enfucell has a battery that will help people make a difference by cutting down on all the metal, lithium and alkaline that leaks from conventional cells. "Our battery doesn't have to go to the battery-recycle bin. It's disposable as household waste," says Jaako Happonen, 50, Enfucell's chief executive.

Enfucell, based outside Helsinki, builds batteries out of paper. Its SoftBattery works much the same way as ordinary "button" batteries (like the one in your watch) and "finger" batteries (think AA). Ions travel from an anode, pass through a solution called an electrolyte to a cathode and emerge as an electrical charge. Instead of running ions through metal casings full of toxic and corrosive substances like lithium and alkaline, Enfucell uses a thin paper sheet as a conduit. It pastes one side with zinc and the other side with manganese dioxide. Ions flow through an electrolyte solution of water and zinc chloride within the paper.

The batteries are not only environmentally friendly but they're also cheap. Happonen says he will be able to sell his SoftBatterys for about a penny each once he hits mass production. Today's button batteries sell in bulk for about 20-c- each. Because the 0.4-mm-thin SoftBattery is made from paper, Enfucell can make sheets of the stuff and size them to specific applications. An average size would be about 2 in. by 2 in.

Enfucell batteries won't power your digital camera, your flashlight or your watch. At 1.5 volts they might be sufficiently powerful, but they don't last long enough. Rather, Happonen hopes first to sell large quantities to the makers of RFID (radio frequency identification) tags, which don't draw constant power and lend themselves to the battery's thinness. RFID tags are the tiny chips that are replacing bar codes. They wirelessly transmit information about themselves, making it easier to track, say, what's in stock in a store. Battery-powered RFID tags can transmit farther than non-battery-powered versions and push RFID signals through liquid and aluminum cans--two common signal stoppers in supermarkets. The market potential is in the billions if RFID technology expands as predicted.

Happonen is also targeting musical greeting cards and LED-adorned marketing brochures. Another market: makers of cosmetic and medical patches. Happonen notes that battery-powered antiwrinkle and stop-smoking patches are more effective than those without a power boost. With a nicotine patch, "in the morning when you need a bigger dose of nicotine, you push a button," he says.

For now, the four-year-old company is getting by on $900,000 in financing from the Finnish government and venture-capital backers. Happonen envisions a day when his paper battery could power electronic paper. Ironically, one paper product, the SoftBattery, would undermine the future of another, traditional writing and print paper. The world could then hold onto a few more of its trees. That would be no little thing.