Electrochemical behaviors of binder-free CoFe-layered double-hydroxide-decorated hexagonal-flower-like NiCo2O4 as electrode for supercapacitors

To enhance the capacitance of an inorganic electrode material, CoFe-layered double hydroxide (LDH) was grafted on the surface of hexagonal-flower-like NiCo2O4. Composites with different Co/Fe ratios were directly grown on Ni foam by using the hydrothermal method. The composite with the Co/Fe molar ratio of 1:2 (NiCo2O4 @Co1Fe2-LDH) exhibited the best electrochemical performance, with a specific capacitance of 2595 F g-1 at a current density of 1 A g-1. The composite prevented the aggregation of CoFe-LDH and induced reversible redox reactions, thus showing high specific capacitance and good stability. The application of the electrode on a packaging asymmetric capacitor consisting of NiCo2O4 @Co1Fe2-LDH as the anode, activated carbon as the cathode yielded a maximum energy density of 27.33 Wh kg-1 at a power density of 800 W kg-1 and an excellent capacitive retention of 96% even after 5000 charge-discharge cycles.