Urchin-like NiCo2O4 nanoneedles grown on mesocarbon microbeads with synergistic electrochemical properties as electrodes for symmetric supercapacitors

Abstract

Here, we report a facile method to fabricate NiCo₂O₄ nanoneedles on mesocarbon microbeads (MCMB) and form a unique urchin-like core–shell structure. In this composite, the MCMB not only provided high conductivity to benefit effective electron transfer, but also offered abundant adsorption points to load the NiCo₂O₄ nanoneedles. The aggregation of the NiCo₂O₄ nanoneedles was therefore alleviated and each NiCo₂O₄ grain was unfolded to gain easy access to the electrolyte for efficient ion transfer. When the NiCo₂O₄@MCMB composite was evaluated as an electrode material for supercapacitors, a synergistic effect was exerted with high specific capacitance (458 F g⁻¹ at 1 A g⁻¹) and large reversibility (116% capacitance retention after 3000 cycles), both of which were of great advantage over individual MCMB and NiCo₂O₄ nanoneedles. The NiCo₂O₄@MCMB was also used to construct a symmetric supercapacitor, which showed enlarged voltage profiles and could light the LED device for a few minutes, further confirming its excellent electrochemical performance.