Flexible fiber-shaped energy storage devices: principles, progress, applications and challenges

The boom in portable and wearable electronics has increased the high demand for suitable energy storage devices. To satisfy these requirements, new strategies for fiber-shaped supercapacitors (SCs) and lithium ion batteries (LIBs) have been put forward. A state-of-the-art fiber-shaped device displays a unique flexible one-dimensional configuration and superior miniaturization, adaptability, and weavability. In this review, the design principles (e.g., materials and structure) and recent progress (e.g., multifunction and integration) of fiber-shaped SCs and LIBs are firstly described. Then their potential applications in smart textiles, biomedical and implantable electronic systems are highlighted. Lastly, perspectives and challenges on their future development are summarized with the hope of enlightening future research.