Heterostructured Carbon‐Coated Carbon Nitride Hollow Nanotubes Hybrid Microfibers for Ultra‐High Capacity/Rate Wearable Energy Storage

ABSTRACT Fiber‐based supercapacitors (FSCs) have attracted remarkable attention toward wearable applications and smart societies due to the high wearability, deformable energy‐supply, and safe stability. However, suffering from fibrous low porosity, active sites, and charge transfer, FSCs deliver unsatisfactory capacity and rate capability. Herein, we report a novel heterostructured carbon‐coated tubular carbon nitride intercalated graphene fiber (CTg‐C 3 N 4 @GF) for high‐performance FSCs. The CTg‐C 3 N 4 @GF electrode exhibits an ultra‐high areal capacitance (3,648 mF cm −2 ) and rate capability (2,488 mF cm −2 at 50 mA cm −2 ). Additionally, the assembled solid‐state FSCs deliver a large energy density (296.2 µWh cm −2 ), cycling stability, and wearable energy‐supply applications (powering a clock and wearable star light). The key to high performance arises from the carbon‐coated facilitating electron transfer; nitrogen species producing abundant active sites, and hollow nanotube enhancing transport pathways for high ion absorption ability, low ion diffusion barriers, improved electrical conductivity, fast charge‐transfer kinetics, and excellent electrochemical reversibility.