Synergistic effects of dual nano-type electrode of NiCo-nanowire/NiMn-nanosheet for high-energy supercapacitors

A unique three-dimensional hybrid NiCo(CO3)(OH)(2) nanowire/NiMn(CO3)(OH)(2) nanosheet composite was fabricated using a facile hydrothermal method as a binder-free electrode directly grown on Ni foam for supercapacitors. We examined the synergistic effect by fabricating Ni-Co-Mn ternary electrodes that used Ni-Co with a large specific surface area and Mn with a very high theoretical capacity. The new hybrid electrode had good electrochemical characteristics, exhibiting remarkably high specific capacitances of 1673.3 and 453.0 Fg(-1) at 3 and 15 Ag-1, respectively. Compared with other samples, the capacitance showed less reduction as the current density increased. This result indicates stable electrode properties with increasing voltage. The cycling stability of the hybrid NiCo(CO3)(OH)(2)/NiMn(CO3)(OH)(2) composite was measured as 82.1% after 5000 cycles. Additionally, we fabricated an asymmetric supercapacitor employing the NiCo(CO3)(OH)(2)/NiMn(CO3)(OH)(2) composite as the positive electrode and graphene as the negative electrode, which exhibited a high energy density of 27.2 W h kg(-1) at a power density of 702.7 W kg(-1) and a remarkable cycling stability, with 89.4% capacitance retention after 5000 cycles. Thus, for the first time, we investigated the dual nano-type structure of an NiCo(CO3)(OH)(2) nanowire/NiMn(CO3)(OH)(2) nanosheet electrode for supercapacitors and obtained satisfactory results. (C) 2019 Elsevier B.V. All rights reserved.