Ultra-thin NiS nanosheets as advanced electrode for high energy density supercapacitors

Low energy density of supercapacitors is one of the major downsides for their practical applications. Here, a simple hydrothermal method was developed to synthesize NiS nanosheets on Ni foam. NiS nanosheets with a rough surface promise large electroactive surface area for energy storage, and show an ultra-high capacitance of 2587 F g^-1 at a scan rate of 0.2 A g^-1 (corresponding to the discharge time of 5563 s). The NiS nanosheets also present an outstanding cycling stability of 95.8% after 4000 cycles. As a positive electrode material for hybrid supercapacitors (HSC), NiS nanostructures provide a broad voltage window of 1.7 V. Our device also shows a high energy density of 38 W h kg^-1 at a power density of 1.5 kW kg^-1.