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

Abstract

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.