Construction of ZnCo2S4@Ni(OH)2 core–shell nanostructures for asymmetric supercapacitors with high energy densities†
ZnCo2S4 nanoneedle clusters are uniformly grown as a core on foamed nickel and then are coated with Ni(OH)2 nanosheets as shell layers. The formed ZnCo2S4@Ni(OH)2 core–shell structures as electrode materials exhibit high specific capacitance (1193 C g−1 at 1 A g−1) and superior cycle rate performance (a capacity retention rate of 92% after 8000 cycles). The ZnCo2S4@Ni(OH)2//AC asymmetric supercapacitor composed of AC//NF as the negative electrode, ZnCo2S4@Ni(OH)2 as the positive electrode, porous glass fiber paper as the separator and 3 mol L−1 KOH as the electrolyte shows a specific capacitance of 215 F g−1 at 1 A g−1 with 70% capacitance retention and 100% coulombic efficiency even after 5000 cycles at a scan rate of 5 A g−1, evidencing the excellent energy storage capacitance and electrochemical performance. Besides, the ZnCo2S4@Ni(OH)2//AC device exhibits an exceptional energy density of ∼44 W h kg−1 at a power density of ∼0.83 kW kg−1.