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Thin, Flexible, Rechargeable Battery Ready for Use

July 1, 1997

Wide Range of Application
A large electronics manufacturer has developed a new type of flexible battery only 0.5 millimeters thick. The battery, which can be recharged multiple times, is formed by hardening an electrolytic solution into a gelatin. This allows the use of a flexible, ultra-thin plastic casing to house the battery, which is expected to promote further miniaturization of such products as personal computers and cellular telephones.

The new rechargeable cell is a polymer lithium ion battery; its electrolytic substance is contained in a case about the size of a credit card. Previous batteries had used only liquid electrolytes, but the manufacturer succeeded in congealing the solution by mixing it with an absorbent material. The technology is similar to the adding of flour to milk to solidify the mixture.

Batteries until now have had to rely on metallic cases to prevent their electrolytic solution from leaking out, but this new technology has made possible the use of plastic for the battery shell. This means a new type of battery that can be twisted and bent without breaking it.

Moreover, due to limitations imposed by the welding techniques used in their manufacture, metal-shell cells cannot be made thinner than five millimeters. The new plastic construction enables the production of batteries only one-tenth as thick. And the increased ease with which engineering on a minute scale can be carried out should bring the costs of the new cells to about half of the price of existing ones. The batteries can be made any size from only five millimeters on a side to the area of an A5 sheet of paper (about 210 by 150 mm).

The battery is expected to be used widely in products that are growing ever smaller, such as portable computers and telephones, as well as in memory cards for use with personal computers. It should prove a hit with both manufacturers and consumers.

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