Hierarchical Core/Shell NiCo(2)O(4)@NiCo(2)O(4) Nanocactus Arrays with Dual-functionalities for High Performance Supercapacitors and Li-ion Batteries

We report the synthesis of three dimensional (3D) NiCo(2)O(4)@NiCo(2)O(4) nanocactus arrays grown directly on a Ni current collector using a facile solution method followed by electrodeposition. They possess a unique 3D hierarchical core-shell structure with large surface area and dual-functionalities that can serve as electrodes for both supercapacitors (SCs) and lithium-ion batteries (LIBs). As the SC electrode, they deliver a remarkable specific capacitance of 1264 F g(−1) at a current density of 2 A g(−1) and ~93.4% of capacitance retention after 5000 cycles at 2 A g(−1). When used as the anode for LIBs, a high reversible capacity of 925 mA h g(−1) is achieved at a rate of 120 mA g(−1) with excellent cyclic stability and rate capability. The ameliorating features of the NiCo(2)O(4) core/shell structure grown directly on highly conductive Ni foam, such as hierarchical mesopores, numerous hairy needles and a large surface area, are responsible for the fast electron/ion transfer and large active sites which commonly contribute to the excellent electrochemical performance of both the SC and LIB electrodes.