Nickel-Cobalt Sulfide Nonwoven Cloth with UltraHigh Areal Capacitance for Flexible Supercapacitors

Supercapacitors represent a promising energy storage technology for flexible, miniaturized, and wearable electronic devices in the future. At present, to achieve high mechanical flexibility, many available flexible supercapacitors are constructed into thin electronic devices. However, the thin thickness of the whole supercapacitor electrode will greatly limit the mass loading of active materials and lower the energy density, which as a result, substantially hindering the application of supercapacitors for wearable electronic devices. Herein, we report a magnetic field induced fabrication of threedimensional nonwoven cloth consists of cross-linked ultra-long NiCo sulfide nanowires as a high-performance supercapacitor cathode. Due to the stress release by slippage between the cross- linked nanowires under external force, the NiCo sulfide nonwoven cloth electrode with the thickness up to 0.5 mm can achieve ultra-high flexibility, even foldability and arbitrarily deformable properties. Most importantly, the thick threedimensional architecture enables the high mass loading of active materials, which is crucial for high energy density flexible supercapacitors. The NiCo sulfide nonwoven cloth electrode demonstrates an ultra-high areal capacitance over 4.91 F cm-2, with negligible capacitance decay after 10000 cycles, outperforming most of reported flexible supercapacitors and revealing its great potential for practical application in wearable electronic device.