Amaryllis-like NiCo2S4 nanoflowers for high-performance flexible carbon-fiber-based solid-state supercapacitor

Low-cost dynamic materials for Faradaic redox reactions are needed for high-energy storage supercapacitors. A simple and cost-effective hydrothermal process was employed to synthesize amaryllis-like NiCo2S4 nanoflowers. The sample was characterized by X-ray powder diffraction, Brunauer–Emmett–Teller method, scanning electron microscopy, and transmission electron microscopy. NiCo2S4 nanoflowers were coated onto carbon fiber fabric and used as a binder-free electrode to fabricate a solid-state supercapacitor compact device. The solid-state supercapacitor exhibited excellent electrochemical performance, including high specific capacitance of 360 F g−1 at scan rate of 5 mV s−1 and high energy density of 25 W h kg−1 at power density of 168 W kg−1. In addition, the supercapacitor possessed high flexibility and good stability by retaining 90% capacitance after 5000 cycles. The high conductivity and Faradic-redox activity of NiCo2S4 nanoflowers resulted in high specific energy and power. Thus, NiCo2S4 nanoflowers are promising pseudocapacitive materials for low-cost and lightweight solid-state supercapacitors.