Construction of hierarchical polypyrrole coated copper-catecholate grown on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) fibers for high-performance supercapacitors.

Fiber-shaped supercapacitors (FSCs) are considered as the optimal candidate for wearable energy devices, due to their high safety, excellent electrochemical stability, workability and body adaptability. However, the specific capacitances of today's FSCs such as carbon nanotube fibers and graphene fibers, are still not high enough for practical applications due to the limitation of their energy storage mode. So, we design a ternary composite fiber-shaped electrode: First, a kind of metal organic framework (MOF), copper-catecholate (Cu-CAT) nanorods, are in-situ grown on a wet-spun poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) fiber at the ambient temperature. Second, polypyrrole (PPy) is electrodeposited on the surface of the Cu-CAT/PEDOT:PSS fiber to obtain PPy@Cu-CAT@PEDOT:PSS fiber (PPy@Cu-CAT@PF). The growing Cu-CAT with high porosity anchored on the fiber surface provides electrochemical activate sites and the encapsulation of PPy effectively provides a continuous charge transfer path and improve its cycling stability. Notably, the PPy@Cu-CAT@PF electrode exhibits a satisfactory areal capacitance of 669.93 mF cm at 2 mA cm, which remains 61.66% even at a high current density of 20 mA cm. Furthermore, the assembled symmetric FSC displays excellent electrochemical properties and outstanding mechanical flexibility, demonstrating its feasibility as a wearable supercapacitor.