Electronic Design

Printing Paper Batteries

There are paper cups, paper napkins, and even paper airplanes. So why not paper batteries?

Although not powerful enough to drive everyday products like cell phones and digital cameras, an emerging generation of thin, flexible, paper-based batteries could soon find a home powering tiny label displays, smart cards, RFID tags, and other mobile devices requiring only modest amounts of power.

“It’s for devices that are typically very low current—things that you would throw away,” says Rob Enderle, principal analyst with the Enderle Group, a technology research firm located in San Jose, Calif. “It’s not a reusable technology, though it does appear to be relatively environmentally friendly.”

Two companies have already developed paper batteries: Enfucell, located in Espoo, Finland, and Power Paper, based in Kiryat Aryeh, Israel. While Power Paper is already marketing its product, Enfucell is still refining its device.

The Enfucell paper battery, which the company calls a “SoftBattery,” utilizes traditional battery technology tucked inside a paper wrapping. Based on traditional paper printing, the manufacturing process places zinc, nickel, or other metal onto one side of a sheet of paper and manganese oxide, or other oxide, on the opposite side. The paper, which contains an electrolyte, is used as a separator.

Jaakko Happonen, Enfucell’s CEO, claims the 1.5-V battery generates electricity at a stable rate across a wide temperature and humidity range without any environmentally harmful byproducts. “It is disposable with household wastes,” he says.

Different voltages for various applications can be achieved by using multiple batteries in series or by using different materials. The battery’s prime advantage is that it is cheap, thin, and flexible. “The customer will decide the size and shape,” says Happonen. Enfucell, a spinoff from the Helsinki University of Technology’s Automation Laboratory, has raised about $715,000 in financing and hopes to have a commercial product ready within two years.

Israel’s Power Paper, on the other hand, has the distinction of being the only paper battery maker with an actual commercial product line. The company’s batteries are composed of zinc-anode-based and manganese-dioxide-based cathode layers. Like Enfucell, Power Paper’s batteries are printed and require no metal case. The company claims that it can apply battery components onto virtually any substrate to create a power source that’s thin and flexible.

By using industry-standard printing, drying, and laminating equipment and processes, Power Paper maintains that it can create batteries that are price competitive, on a per square inch basis, with conventional mobile power technologies. “The cost is similar to paper,” says Enderle. “It’s something you can actually use for labels and throw away.”

Power Paper offers four versions of its 1.5-V paper battery technology, covering a range of capacities and discharge rates. The STD-1 version has an outline dimension of 39 mm and a 0.6-mm thickness. It offers 0.5 mA in continuous current, a 15-mAh capacity, 15-Ω internal resistance, and a nominal peak pulse discharge current of 15 mA at 1 ms. The beefier STD-2 has an outline dimension of 55 mm and a 0.6-mm thickness. It offers 1 mA in continuous current, a 30-mAh capacity, 15-Ω internal resistance, and a nominal peak pulse discharge current of 30 mA at 1 ms. All of the models offer a 25-mm bending radius and a shelf life of around three years.

Power Paper says it can also custom-design batteries that can be mass-produced to fit the size, thickness, and form factors required for the design of any product. The firm’s current customers include RFID card manufacturers and toy makers.

Down the road, paper batteries could lead to the development of new and innovative electronic devices. “Things like smart blood sample bags,” says Enderle. “A paper battery label could power a thermostat and display that would show if the bag had been exposed to detrimental heat or cold.”

At least one offbeat application has already surfaced. Power Paper is targeting cosmetic businesses with tiny, flat, and flexible batteries that are designed for wrinkle reduction (see the figure). “It’s an inexpensive electrical device you stick on your face, and when you’re done you peel it off and toss it away,” says Enderle. “Sort of like a non-toxic Botox on a label.”

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