Advanced asymmetric supercapacitors based on CNT@Ni(OH)2 core–shell composites and 3D graphene networks

Asymmetric supercapacitors (ASCs) with carbon nanotube@nickel hydroxide nanosheet (CNT@Ni(OH)2) core–shell composites as positive electrodes and three-dimensional (3D) graphene networks (3DGNs) as negative electrodes were reported in aqueous KOH electrolyte. The CNT@Ni(OH)2 core–shell composites were prepared through a facile chemical bath deposition method, while 3DGNs were obtained by freeze-drying of graphene hydrogels. By virtue of their unique microstructures, superb electrochemical properties were achieved in a three-electrode system, e.g., 1136 F g−1 at 2 A g−1 for the CNT@Ni(OH)2 electrode within 0–0.5 V and 203 F g−1 at 1 A g−1 for the 3DGN electrode within −1–0 V. Benefiting from these merits, the as-fabricated CNT@Ni(OH)2//3DGN ASC showed a maximum energy density of 44.0 W h kg−1 at a power density of 800 W kg−1 and even retained 19.6 W h kg−1 at 16 000 W kg−1 in the voltage region of 0–1.6 V.