Nitrogen-Doped Carbon Encapsulated Mesoporous Vanadium Nitride Nanowires as Self-Supported Electrodes for Flexible All-Solid-State Supercapacitors

Flexible 3D nanoarchitectures have received tremendous interest recently because of their potential applications in flexible/wearable energy storage devices. Herein, 3D intertwined nitrogen-doped carbon encapsulated mesoporous vanadium nitride nanowires (MVN@NC NWs) are investigated as thin, lightweight, and self-supported electrodes for flexible supercapacitors (SCs). The MVN NWs have abundant active sites accessible to charge storage, and the N-doped carbon shell suppresses electrochemical dissolution of the inner MVN NWs in an alkaline electrolyte, leading to excellent capacitive properties. The flexible MVN@NC NWs film electrode delivers a high areal capacitance of 282 mF cm(-2) and exhibits excellent long-term stability with 91.8% capacitance retention after 12 000 cycles in a KOH electrolyte. All-solid-state flexible SCs assembled by sandwiching two flexible MVN@NC NWs film electrodes with alkaline poly(vinyl alcohol) (PVA), sodium polyacrylate, and KOH gel electrolyte boast a high volumetric capacitance of 10.9 F cm(-3), an energy density of 0.97 mWh cm(-3), and a power density of 2.72 W cm(-3) at a current density of 0.051 A cm(-3) based on the entire cell. By virtue of the excellent mechanical flexibility, high capacitance, and large energy/power density, the self-supported MVN@NC NWs paper-like electrodes have large potential applications in portable and wearable flexible electronics.