Flexible fiber-shaped supercapacitor based on nickel-cobalt double hydroxide and pen ink electrodes on metallized carbon fiber

Flexible fiber-shaped supercapacitors (FSSCs) recently are of extensive interest for portable and wearable electronic gadgets. Yet the lack of industrially flexible and cost-effective fibers with high conductivity and capacitance tremendously limits its civil practical application. To this end, here, we present pristine twisting carbon fibers (CFs) thread coated with a thin metallic layer via electroless deposition (ED) route, which exhibits exceptional conductivity with ～300% enhancement and superior mechanical strength (1.8 GPa). Subsequently, the commercial available conductive pen ink modified high conductive composite fiber uniformly covered with ultrathin nickel-cobalt double hydroxides (Ni-Co DHs) was introduced to fabricate flexible FSSC. The synthesized functionalized hierarchical flexible fiber exhibits high specific capacitance up to 1.39 F·cm-2 in KOH aqueous electrolyte. The asymmetric solid-state FSSC show maximum specific capacitance of 28.67 mF·cm-2 and energy density of 9.57 uWh·cm-2 at corresponding power density as high as 492.17 uW·cm-2 in PVA/KOH gel electrolyte, demonstrating its great potential in flexible electronic devices.