In-situ growth of vertically aligned nickel cobalt sulfide nanowires on carbon nanotube fibers for high capacitance all-solid-state asymmetric fiber-supercapacitors

Abstract

Fiber-supercapacitors (FSCs) are promising power sources for miniature portable and wearable electronic devices. However, the development and practical application of these FSCs have been severely hindered by their low volumetric capacitance and narrow operating voltage. In this work, vertically aligned nickel cobalt sulfide (NiCo 2 S 4 ) nanowires grown on carbon nanotube (CNT) fibers were achieved through an in-situ two-step hydrothermal reaction method. The as-prepared NiCo 2 S 4 @CNT fiber electrode exhibits a high volumetric capacitance of 2332 F cm−3, benefiting from its superior electric conductivity, large surface area, and rich Faradic redox reaction sites. Furthermore, a NiCo 2 S 4 @CNT//VN@CNT (vanadium nitride nanosheets grown on CNT fibers) asymmetric fiber-supercapacitor (AFSC) was successfully fabricated. The device exhibits an operating voltage up to 1.6 V and a high volumetric energy density of 30.64 mWh cm−3. The device also possesses outstanding flexibility as evidenced by no obvious performance degradation under various bending angles and maintaining high capacitance after 5000 bending cycles. This work promotes the practical application of flexible wearable energy-storage devices. © 2019 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences