Batteries of the Future: Thin and Bendable

Thin, bendable batteries have become a hotly competitive area as more electronic products requiring their use emerge, such as E-paper, RFID tags and smart cards.

"Wow, will you look at that application! We've been concentrating on just boosting capacity for use in mobile gear and bicycles. That's really thinking outside the box! " Battery researchers were astounded recently at an eye wrinkle correcting patch with an onboard battery, announced recently by cosmetics manufacturer Estee Lauder Inc of the US. It applies a minute electrical current to help effective agents permeate the skin in the corner of the eye, smoothing out wrinkles. Battery researchers were surprised by the fact that the new application was achieved with a battery offering characteristics inferior to existing batteries, such as lower energy density, but which is thin and bendable.

Development of storage devices has been emphasizing increased output (output density) and capacity (energy density), but a new dimension for competition is developing: Bendable and extremely thin batteries, only several um to several hundred um thick (Fig 1). A Li-polymer rechargeable battery was developed some time ago, using a gel battery electrolyte in a bendable package only several mm in thickness, but it was unable to find an application that really utilized its characteristics. The primary application was merely fitting into narrow spaces in equipment, without requiring any bending.

Now there are a number of products searching for thin, bendable batteries, and not only in cosmetics. Engineers involved in electronic paper, for example, are beginning to worry because while they are developing thin, bendable E-paper with a target of a few years from now, they haven't started work on batteries yet. They are searching for a thin, bendable battery, hoping that someone will develop one in time for commercial release.