Monolayer\nNickel Cobalt Hydroxyl Carbonate for High Performance All-Solid-State\nAsymmetric Supercapacitors

Abstract

The emergence of\natomically thick nanolayer materials, which feature a short ion diffusion\nchannel and provide more exposed atoms in the electrochemical reactions,\noffers a promising occasion to optimize the performance of supercapacitors\non the atomic level. In this work, a novel monolayer Ni–Co\nhydroxyl carbonate with an average thickness of 1.07 nm is synthesized\nvia an ordinary one-pot hydrothermal route for the first time. This\nunique monolayer structure can efficiently rise up the exposed electroactive\nsites and facilitate the surface dependent electrochemical reaction\nprocesses, and thus results in outstanding specific capacitance of\n2266 F g^–1. Based on this material, an all-solid-state\nasymmetric supercapacitor is developed adopting alkaline PVA (poly­(vinyl\nalcohol)) gel (PVA/KOH) as electrolyte, which performs remarkable\ncycling stability (no capacitance fade after 19 000 cycles)\ntogether with promising energy density of 50 Wh kg^–1 (202 μWh cm^–2) and high power density of\n8.69 kW kg^–1 (35.1 mW cm^–2). This\nas-assembled all-solid-state asymmetric supercapacitor (AASC) holds\ngreat potential in the field of portable energy storage devices.