All-solid-state flexible asymmetric supercapacitors with high energy and power densities based on NiCo2S4@MnS and active carbon

Abstract

Electrode material based on a novel core–shell structure consisting of NiCo2S4 (NCS) solid fiber core and MnS (MS) sheet shell (NCS@MS) in situ grown on carbon cloth (CC) has been successfully prepared by a simple sulfurization-assisted hydrothermal method for high performance supercapacitor. The synthesized NiCo2S4@MnS/CC electrode shows high capacitance of 1908.3 F g−1 at a current density of 0.5 A g−1 which is higher than those of NiCo2S4 and MnS at the same current density. A flexible all-solid-state asymmetric supercapacitor (ASC) is constructed by using NiCo2S4@MnS/CC as positive electrode, active carbon/CC as negative electrode and KOH/poly (vinyl alcohol) (PVA) as electrolyte. The optimized ASC shows a maximum energy density of 23.3 Wh kg−1 at 1 A g−1, a maximum power density of about 7.5 kw kg−1 at 10 A g−1 and remarkable cycling stability. After 9000 cycles, the ASC still exhibited 67.8% retention rate and largely unchanged charge/discharge curves. The excellent electrochemical properties are resulted from the novel core–shell structure of the NiCo2S4@MnS/CC electrode, which possesses both high surface area for Faraday redox reaction and superior kinetics of charge transport. The NiCo2S4@MnS/CC electrode shows a promising potential for energy storage applications in the future.