Aqueous battery fiber with high volumetric and areal power density for flexible electronics

The performance of small wearable or robotic devices is limited by the energy and power density of batteries. We present a rechargeable aqueous gel-type AgO-Zn battery, with a power density of 17.9 W/cm 3 and an energy density of 624 mWh/cm 3 at 0.2C and 358 mWh/cm 3 at 50C. We designed a multilayered fractal ion-channel structure for the long, fibrous AgO electrode using a twisting method. A prototype headband of 2 cm × 25 cm woven with the fibrous batteries was tested. With a power output of >4 W, the headband battery can extend the operation time of commercial augmented reality glasses from 2 h to over 12 h. Prototype batteries of different shapes using this design were made, including a carrying bag that works as a power bank for a phone and batteries for a small robotic spider and a robotic bird.