Hydrogenated CoOx nanowire@Ni(OH)2 nanosheet core–shell nanostructures for high-performance asymmetric supercapacitors

Abstract

We report a facile strategy to prepare 3D core–shell nanowire heterostructures with microporous hydrogenated CoO_x (H–CoO_x) nanowires as the conducting scaffold to support Ni(OH)₂ nanosheets. Benefiting from the H–CoO_x nanowire core to provide the effective pathway for charge transport and the core–shell heterostructures with synergistic effects, the H–CoO_x@Ni(OH)₂ core–shell nanowire electrode achieved the specific capacitance of 2196 F g⁻¹ (areal capacitance of 5.73 F cm⁻²), which is approximately a 1.4-fold enhancement compared with the Co₃O₄@Ni(OH)₂ core–shell nanowires. An aqueous asymmetric supercapacitor (ASC) device was fabricated by using H–CoO_x@Ni(OH)₂ nanowires as the positive electrode and reduced graphene oxide @Fe₃O₄ nanocomposites as the negative electrode. The ASCs achieved high energy density (∼45.3 W h kg⁻¹ at 1010 W kg⁻¹), high power density (∼7080 W kg⁻¹ at 23.4 W h kg⁻¹) and high cycling stability. Furthermore, after charging for ∼1 min, one such 22 cm² ASC device demonstrated to be able to drive a small windmill (0.8 V, 0.1 W) for 20 min. Two such ASCs connected in series can power up a seven-color LED (3.2 V) efficiently.