Double-Layer MnCo₂S₄@Ni-Co-S Core/Shell Nanostructure on Nickel Foam for High-Performance Supercapacitor

A double-layer MnCo₂S₄@Ni-Co-S (MCS@NCS) core/shell nanocomposite is successfully deposited on nickel foam using a facile and simple method which includes a hydrothermal treatment and an electrochemical deposition and exhibits excellent electrochemical performance. With the introduction of sulfur via a sulfurization process, the MnCo₂S₄ nanorods have larger specific surface area compared to the MnCo₂O₄ nanorods and can serve as porous scaffolds for loading a large amount of additional active materials, facilitating electron transport and ion diffusion. The deposited Ni-Co-S nanosheet on MnCo₂S₄ can further increase the electro-active surface area and electrical conductivity as well as reinforce the mechanical stability of the whole electrode. Combining both structural and electrochemical advantages, the electrode with MCS@NCS heterostructures has high areal capacitance (10.14 F cm⁻² at 1 mA cm⁻²). An asymmetric supercapacitor with Ni foam-activated carbon as the negative electrode and Ni foam-MCS@NCS as the positive electrode is fabricated and shows remarkable high areal capacitance (1.92 F cm⁻² at 1 mA cm⁻²) and good cycling stability (72% capacitance retention after 5000 cycles), demonstrating its great potential as an efficient energy storage device for electronic systems.