Wearable electronics are exploding in popularity as more and more people discover the delights of fitness trackers and Google Glass. However, in order to be useful all day long, these devices require batteries that can last a long time without compromising size and weight. Researchers at Fudan University in Shanghai have designed and fabricated carbon nanotube (CNT) composite yarns that are wound onto a cotton fiber to create a high performance Li-ion battery. The super thin fibers (their diameter is only 1 millimeter) can be woven into a cloth to be used in wearable electronics.

“A power source that can be directly and seamlessly integrated with the wearable electronics is highly needed,” Weng said. “Therefore, a power source in a fiber shape is desired because it is flexible and easily woven into a textile. We fabricated a fiber full Li-ion battery based on carbon nanotube fibers for the first time, and the fiber battery can be easily woven into an energy textile with a high performance.”

The CNT fiber Li-ion battery has a high energy density and can retain 87 percent of its capacity after 100 cycles. In the future, the researchers hope to improve upon the performance of the battery, increasing the capacity and the cycle life.