All-solid-state wire-shaped asymmetric supercapacitor based on binder-free CuO nanowires on copper wire and PPy on carbon fiber electrodes

A wire-shaped asymmetric supercapacitor based on CuO and polypyrrole (PPy) is developed in this work. The fiber-shaped positive electrode composed of CuO nanowires (CuO NWs) on Cu wire (Cu wire/CuO NWs) is successfully prepared via anodization of copper wire followed by thermal treatment. Meanwhile, conductive polymer PPy is grown on carbon fiber bundle (CF/PPy) by electrodeposition as a negative electrode. Subsequently, an all-solid-state wire-shaped asymmetric supercapacitor is assembled with Cu wire/CuO NWs, CF/PPy and PVA-KOH gel electrolyte. Benefiting from the efficient pseudocapacitive properties of the binder-free positive electrode with CuO nanowires directly grown on the copper wire surface and the negative electrode with PPy tightly covered on the carbon fibers, the all-solid-state wire-shaped asymmetric supercapacitor assembled exhibits a high energy density (9.31 μWh cm⁻²) and specific capacitance (39.67 mF cm⁻², 24.91 mF cm⁻¹). Moreover, this device also shows an excellent stability of electrochemical performance at different bending conditions, demonstrating its potential to serve as a flexible power source for portable/wearable electronics.