Free-standing 3D core-shell architecture of Ni₃S₂@NiCoP as an efficient cathode material for hybrid supercapacitors

The design and discovery of free-standing hybrid electrode materials with large absolute capacity and high cycling stability for energy storage become desirable and are still challenging. In this work, we demonstrate that the hybrid supercapacitor (HSC) device is assembled by 3D core-shell hierarchical nanorod arrays of Ni₃S₂@NiCoP nanocomposite for the first time. The Ni₃S₂@NiCoP nanocomposite is successfully synthesized through a facile stratagem containing hydrothermal process and the subsequent electrodeposition method. The 3D architecture of Ni₃S₂@NiCoP hybrid electrode composed of vertically aligned "hyperchannel" 1D Ni₃S₂ nanorods and highly conductive interconnected 2D nanosheets of NiCoP is beneficial to fast electron transfer kinetics, thus leading to enhancing the ionic and electronic conductivity, kinetics of redox reaction, and synergistic behavior of active species. The fabricated HSC device with Ni₃S₂@NiCoP electrode delivers outstanding areal capacity of 109 µAh cm^-2 at a current density of 1 mA cm^-2, brilliant energy density of 74.9 Wh kg^-1 at a power density of 700 W kg^-1, and prominent cyclic performance of 92% capacity retention even after 144-h floating test. This work demonstrates that the core-shell hierarchical nanorod arrays of Ni₃S₂@NiCoP can be viewed as one of the novel battery-type electrode materials for high-performance HSCs.