Fabrication of Supercapacitors from NiCo2O4 Nanowire/Carbon-Nanotube Yarn for Ultraviolet Photodetectors and Portable Electronics

Linear flexible supercapacitors are of considerable interest for future wearable electronics and photodetectors. Inorganic metallic oxide-based electrochemical pseudocapacitors have a high energy density whereas supercapacitors based on carbon-nanotube (CNT) yarns show high flexibility and high power densities. Besides high power density and energy density, fabrication of linear supercapacitors with excellent flexibility is still a challenge. Here, we report a linear supercapacitor architecture obtained by integrating CNT yarn and a Cu filament with NiCo 2 O 4 nanowires. NiCo 2 O 4 nanowires grow in situ on the surface of CNT yarn intertwined with the Cu filament. Due to the high electrochemical performance of both NiCo 2 O 4 nanowires and CNT yarn and the high charge-transport efficiency of the Cu filament as current collector, the supercapacitor demonstrates a specific areal capacitance as high as 277.3 mF cm 2 and an energy density of 35.76 μWh cm −2 coupled with a power density 0.154 mW cm −2 . The linear supercapacitor is very flexible and can be woven into a fabric without losing its capacity to store energy. Its capacitance remains at 89 % after 5000 charge/discharge cycles. The linear supercapacitor may be used as an ultraviolet photodetector with good stability in response to the UV light signal and also to power light-emitting diodes (LEDs).