Unlike conventional Li-ion batteries with metal foils used in wearable electronics, our flexible batteries developed with conductive textiles achieve high energy storage performance, remarkable flexibility and excellent cyclic stability simultaneously. They are thin, lightweight, foldable, bendable, durable, washable and have been proved to be penetration and impact safe. These flexible batteries are also customizable in size and energy capacity, allowing a high degree of flexibility for product design. They can be used to power portable and wearable electronics for the applications of healthcare treatment and monitoring, Internet of Things and human-interface interactions.