Technology for flexible batteries rechargable by solar power

Solar-powered electronics could be could soon be woven into clothing fibres or incorporated into watches. Professors Jang-Wook Choi and Jung-Yong Lee from the Graduate School of EEWS and Taek-Soo Kim from the Department of Mechanical Engineering at KAIST have developed technology for flexible and foldable batteries which are rechargeable using solar energy.

Taek-Soo Kim, Jung-Yong Lee, Jang Wook Choi and colleagues explain that electronic textiles have the potential to integrate smartphone functions into clothes, eyeglasses, watches and materials worn on the skin. The bottleneck slowing progress towards development of a wider range of flexible e-fabrics and materials is the battery technology required to power them. Current wearable electronics, such as smart watches and Google Glass, require a charger with a cord, and already-developed textile batteries are costly and impractical. To unlink smart technology from the wall socket, the team had to rethink what materials are best suited for use in a flexible, rechargeable battery that’s also inexpensive.

They tested unconventional materials and found that they could coat polyester yarn with nickel and then carbon, and use polyurethane as a binder and separator to produce a flexible battery that kept working, even after being folded and unfolded many times. They also integrated lightweight solar cells to recharge the battery without disassembling it from clothing or requiring the wearer to plug in.

Trial versions of flexible and wearable electronics are being developed and introduced in the market such as Galaxy Gear, Apple’s i-Watch and Google Glass. Research is being conducted to make the batteries softer and more wearable and to compete in the fast-growing market for flexible electronics.

This new technology is expected to be applied to the development of wearable computers as well as winter outdoor clothing since it is flexible and light. The research group expects that the new technology can be applied to current battery production lines without additional investment.

Professor Choi said, “It can be used as a core-source technology in the rechargeable battery industry in the future. Various wearable mobile electronic products can be developed through cooperation and collaboration within the industry.”

The authors acknowledge funding from the National Research Foundation of Korea.