Rationally designed nickel oxide ravines@iron cobalt-hydroxides with largely enhanced capacitive performance for asymmetric supercapacitors†
Prominent energy and power densities play crucial roles in supercapacitor devices because of their potential practical application in various electronic devices. Herein, an asymmetric supercapacitor (ASC) with high capacitive performance was manufactured by combining rationally designed NiO@FeCo-layered double hydroxide (LDH), which has enhanced areal capacitance and rate capability, with commercially available pen ink composites as the positive and negative electrodes, respectively. Strikingly, the FeCo-LDHs with ultra-stable rate capability (retaining 94% from 4 to 25 mA cm−2) reported for the first time in this study can be employed to modify other transition metal oxides/hydroxides to achieve balanced performance. The constructed ASC surprisingly delivers an ultrahigh energy density of 64.1 W h kg−1 and a power density of 15 kW kg−1 as well as a robust cyclability (90% capacitance retention after 3000 cycles). In addition, the ASC is capable of readily driving patterned commercial light-emitting diodes (LEDs), motor propellers, and even a toy car, demonstrating its application potential in future nano-energy storage devices.