Flexible CuO nanotube arrays composite electrodes for wire-shaped supercapacitors with robust electrochemical stability

Abstract

Flexible all-solid-state wire-shaped supercapacitors (WSSCs) attracted tremendous attention as power sources for portable and wearable electronics. However, WSSCs usually require excellent electrochemical stability because of the complex functioning environment of wearable electronics. In this work, hierarchical porous nanoarchitectures, consisting of vertically-aligned CuO nanotube arrays/Co(OH)2 nanosheets/reduced graphene oxide composite (CuO/Co(OH)2/rGO), with high electrochemical stability were successfully prepared on Cu wires using in-situ wet-chemical approach. Co(OH)2 nanosheets were utilized to increase charge storage capacity and enlarge electroactive surface area, while supplying abundant faradic active sites. rGO deposition on the nanostructures provides an omnidirectional conductive pathway to optimize electron/ion transfer kinetics and alleviate the exfoliation and dissolution of the active materials into electrolyte. As a flexible battery-type electrode, binder-free CuO/Co(OH)2/rGO hierarchical porous nanostructures demonstrated significantly improved charge storage (22.3 mC cm−1) and excellent long-term cycling performance (with 139% retention after 10,000 cycles). Flexible all-solid-state asymmetric WSSC device matched with CuO/Co(OH)2/rGO and activated carbon (AC) electrodes exhibited wide potential window (equal to 1.45 V), high energy density and long lifetime stability (114% retention after 10,000 cycles). Moreover, flexible WSSC device demonstrated excellent mechanical stability with the charge retention of 109% at 180° bending angle. These devices could be randomly connected to achieve various current and voltage outputs, demonstrating their suitability for wearable electronics.