Hierarchical α-MnO 2 nanowires@Ni1-xMnxOy nanoflakes core-shell nanostructures for supercapacitors

• Main Authors: Lou, David Xiong Wen, Wang, Hsin-Yi, Xiao, Fang-Xing, Yu, Le, Liu, Bin
• Other Authors: School of Chemical and Biomedical Engineering
• Format: Article
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Materials::Nanostructured materials
• Online Access: https://hdl.handle.net/10356/105234; http://hdl.handle.net/10220/20514; http://dx.doi.org/10.1002/smll.201303836
• Institution: Nanyang Technological University

A facile two-step solution-phase method has been developed for the preparation of hierarchical α-MnO2 nanowires@Ni1-xMnxOy nanoflakes core–shell nanostructures. Ultralong α-MnO2 nanowires were synthesized by a hydrothermal method in the first step. Subsequently, Ni1-xMnxOy nanoflakes were grown on α-MnO2 nanowires to form core–shell nanostructures using chemical bath deposition followed by thermal annealing. Both solution-phase methods can be easily scaled up for mass production. We have evaluated their application in supercapacitors. The ultralong one-dimensional (1D) α-MnO2 nanowires in hierarchical core–shell nanostructures offer a stable and efficient backbone for charge transport; while the two-dimensional (2D) Ni1-xMnxOy nanoflakes on α-MnO2 nanowires provide high accessible surface to ions in the electrolyte. These beneficial features enable the electrode with high capacitance and reliable stability. The capacitance of the core–shell α-MnO2@Ni1-xMnxOy nanostructures (x = 0.75) is as high as 657 F g−1 at a current density of 250 mA g−1, and stable charging-discharging cycling over 1000 times at a current density of 2000 mA g−1 has been realized.