On the 4th October, Panasonic revealed a 0.6mm thick bendable battery at a technology fair in Japan, which they claim can bend to 25 degrees, and will not degrade after repeated use. Bendable batteries are, generally speaking, the same as any everyday battery. However, the battery’s components are altered in order to allow them to twist and be bent, and usually will only add up to a total thickness of less than a millimeter. The concept of a bendable battery can be applied to either a primary or secondary (rechargeable) battery, and work is currently in progress to develop other flexible power sources.
A normal battery comprises a cathode, anode, separator, and a current collector. There are a number of ways in which these individual components can be adapted to allow them to twist and bend. The two most common approaches either use ultra-thin forms of commonly used conducting materials, or novel solution-based conductors that can be applied to a thin membrane or polymer binder. Recent research has also shown that it is possible to filter an electrode solution to make a free-standing film without a binding matrix. Rechargeable lithium-ion batteries have been made flexible by the use of flexible nanocarbons, such as graphene, and even self-rechargeable batteries have been developed with the use of very fine solar cell films, which charge with exposure to light.
A vast range of applications for flexible power sources have already been identified, in a variety of industries. Flexible batteries in watches, fitness bands, and other wearable technologies would be great for reducing the bulk of these items. Thus making them more comfortable and practical to use. The US Air Force is in the process of developing a flexible lithium-ion battery to use in battlefield devices and sensors, with promising results so far showing that the battery can be completely bent without loss of power. It has even been suggested that these batteries could have applications in medicine, for example in transdermal drug delivery.
Unfortunately, no flexible batteries currently store enough energy to power a smartphone for any length of time, although this area is still being investigated. But when combined with other novel materials and technologies, bendable batteries may be used in fully-flexible smartphones in the future.