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 CoOx (H–CoOx) nanowires as the conducting scaffold to support Ni(OH)2 nanosheets. Benefiting from the H–CoOx nanowire core to provide the effective pathway for charge transport and the core–shell heterostructures with synergistic effects, the H–CoOx@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–CoOx@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.