Hierarchically structured Co9S8@NiCo2O4 nanobrushes for high-performance flexible asymmetric supercapacitors

Hierarchically structured Co9S8@NiCo2O4 nanobrushes constructing by NiCo2O4 nanosheets grown on Co9S8 hollow nanoneedles are first fabricated on carbon cloth substrates via a multi-step route. Remarkably, such Co9S8@NiCo2O4 electrode processes multiplied electrochemical performance as compared to single Co9S8 and NiCo2O4 electrodes. It displays high-performance electrochemical behavior, achieving a specific capacitance of 1966 F g(-1) at 1 A g(-1) while maintaining excellent stability with about 92.9% capacitance retention after 5000 cycles. The flexible solid-state asymmetric supercapacitor based on this Co9S8@NiCo2O4 electrode exhibits a high specific capacitance of over 250 F g(-1) at 1 A g(-1), and delivers a high energy density of 86Wh kg(-1) at 792 W kg(-1) and a maximum specific power of 11360 W kg(-1) at 64 Wh kg(-1). Moreover, the supercapacitor holds more than 84.2% capacitance retention after 10,000 cycles at 10 A g(-1) and demonstrates good durability after different deformation, suggesting its outstanding cycle stability and flexibility. Thus, the Co9S8@NiCo2O4 electrode with special heterogeneous structures shows the potential application in wearable energy storage devices.