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

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.