Three-Dimensional Interconnected Binder-Free Mn–Ni–S Nanosheets for High Performance Asymmetric Supercapacitor Devices with Exceptional Cyclic Stability

A facile one-step method was demonstrated for the electrodeposition of manganese–nickel sulfide (Mn–Ni–S) 3D interconnected sheets on nickel foam substrates. The as-synthesized materials were characterized using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) techniques. Upon their use as supercapacitor electrodes, the electrodeposited Mn–Ni–S showed exceptionally high specific capacitance (2849 and 1986 F/g at 1 and 5 A/g, respectively) and an excellent rate capability. Using Fe 3 O 4 -GR as the negative electrode and the Mn–Ni–S 3D interconnected sheets as the positive electrode to assemble an asymmetric supercapacitor device revealed high power density (800 W kg –1 ) and energy density (40.44 Wh kg –1 ) with 90% capacitance retention and a Columbic efficiency of 100% after 11 000 cycles, indicating the high potential of the fabricated materials for practical energy storage devices.