Controllable synthesis of ZnCo2O4@NiCo2O4 heterostructures on Ni foam for hybrid supercapacitors with superior performance

Abstract

The hierarchical core-shell heterostructures ZnCo2O4@NiCo2O4 on Ni foam (NF) for supercapacitors were prepared via two-step hydrothermal and electrodeposition reactions followed by two post-annealing treatments. The effect of deposition time on its morphology and electrochemical performance was investigated in detail. Combining high electric conductivity of ZnCo2O4 with high stability of NiCo2O4 as well as synergistic effect, the NF/ZnCo2O4@NiCo2O4-100 (NF/ZCO@NCO-100) integrated electrode exhibited high specific capacitance of 1728.1 F g−1 (240.0 mAh g−1) at 1 A g−1, and excellent long-term stability with 97.8% capacitance retention after 10,000 cycles. The assembled hybrid supercapacitor (HSC) delivered the specific capacitance of 133.6 F g−1 (55.7 mAh g−1) at 1 A g−1 and high energy density of 40.58 Wh kg−1 at 745.62 W kg−1 as well as the outstanding long-term stability of 91.3% capacitance retention after 10,000 cycles. These results provide insights into the rational design of transition metal compound composite materials to construct integrated electrodes for high performance supercapacitors.