Design tremella-like Ni-Co selenide with wonderful electrochemical performances as supercapacitor cathode material

Structure design and elements doping are two common ways to promote the electrochemical performances of supercapacitors. Herein, we successfully prepared a new tremella-like nickel-cobalt selenide with porous and ultra-thin nanosheets through a simple two-step hydrothermal method using SiO2 template ((Ni,Co)Se2-T). Tremella-like structure can augment the electrode material's active surface area , that is propitious to the rapid transmission of ions. At the same time, selenization can reduce the resistance and elevate the conductivity. The (Ni,Co)Se2-T electrode shows a specific capacity of 636.2 C g−1 during 1 A g−1 and 420.5 C g−1 at 20 A g−1, showing magnificent capacity as well as rate performance. Furthermore, the assembled hybrid supercapacitor shows an uncommon energy density of 53.7 Wh kg−1 which exceeds most of the nickel cobalt selenide devices during the power density of 822.5 W kg−1. After 10,000 times charge and discharge processes, the capacitor retention still maintains 86.1%. Impressively, fifteen red light emitting diode (LED) bulbs could illuminate for more than 30 min, which fully proves the great potential of this capacitor material in practical application.