Hierarchically hollow structured NiCo2S4@NiS for high-performance flexible hybrid supercapacitors.

Hierarchical nanostructures with outstanding electrochemical properties and mechanical stability are ideal for constructing flexible hybrid supercapacitors. Herein, hierarchically hollow NiCo2S4@NiS nanostructures were designed and synthesized by sulfurizing the hierarchical NiCo double hydroxides (DHs) coated with nickel hydroxide nanostructures on carbon fabrics (NiCo-DHs@Ni(OH)2/CF), which trigger excellent electrochemical performances. The NiCo2S4@NiS/CF exhibits a high specific capacity of 1314.0 C g-1 at a current density of 1 A g-1, and maintains the rate performance at about 79.2% of the initial capacity at 30 A g-1. The hybrid supercapacitors of NiCo2S4@NiS//AC display a high energy density of 62.4 W h kg-1 at a power density of 800 W kg-1 with a remarkable cycling stability (96.2% of initial capacitance after 5000 cycles) and robust mechanical flexibility (no obvious decay of specific capacitance during various deformations). Consequently, NiCo2S4@NiS electrodes are expected to be a promising candidate for new smart energy storage devices with high security, stability and flexibility.