MOFs-derived nickel-cobalt sulfides on nickel foam for high-performance supercapacitor

To meet the demand for high-efficiency energy storage of supercapacitors, it is important to develop binder-free electrodes. As an electrode material, transition metal sulfides are one of the research hotspots in this field. Herein, the Ni 3 S 2 @CoS x /NF electrode has been fabricated in situ on nickel foam via a combination of electrodeposition and hydrothermal methods. SEM analysis reveals that the Ni 3 S 2 nanosheets are dispersed on the surface of CoS x with a hollow dodecahedron structure. Moreover, there is a heterogeneous interface between Ni 3 S 2 and CoS x . The electrochemical measurements with Ni 3 S 2 @CoS x /NF directly serving as the positive electrode demonstrate that the Ni 3 S 2 @CoS x /NF presents a good electrochemical energy storage performance. That is, the Ni 3 S 2 @CoS x /NF electrode exhibits a high areal capacitance of 8100 mF·cm −2 at 1 mA·cm −2 and retains 74% of its initial capacitance after 5000 cycles at 20 mA·cm −2 . An asymmetric supercapacitor using Ni 3 S 2 @CoS x /NF as the positive electrode and activated carbon (AC) as the negative electrode achieves an areal energy density of 270 μWh·cm −2 at a power density of 800 μW·cm −2 . Meanwhile, the mechanism for the improvement of the electrochemical performance of Ni 3 S 2 @CoS x /NF is further analyzed.