Nickel metal-organic framework microspheres loaded with nickel-cobalt sulfides for supercapacitor electrode materials

Metal-organic frameworks (MOFs) are commonly used for template and precursor for supercapacitor electrodes. MOFs are interesting due to excellent specific surface areas and pore structures. Two-dimensional nanosheets suffer from the disadvantages of random growth and easy agglomeration, which significantly limit their applications. In this study, NiCo sulfides with unique morphology were designed using a simple in situ sulfidation method, with Ni-MOF used as the substrate material. The unique three-dimensional structures can offer many reaction sites to guarantee electron transfer. The samples obtained (Ni7S6@NiCo2S4) exhibited good electrochemical performance. The composite electrode material had a capacity value of 1636 F g−1 in a 3 M KOH. In addition, devices comprising with activated carbon had a specific energy of 53 Wh kg−1 and a specific power of 810 W kg−1. The asymmetric supercapacitor (ASC) exhibited outstanding cycling of 87 % after 5000 cycles. This study demonstrates a flexible method for activating MOFs to enhance the capabilities of supercapacitor materials. Thus, this method maintains a well-defined stacking structure of nanosheets while enriching the active sites, it is promising for the applications of MOF derivatives. •Polysulfide composites synthesized on Ni-MOF substrate.•Solvothermal and anion exchange methods were used.•High specific capacitance and high current densities achieved.•After 5000 cycles, capacity remained at 87 % of original value.•Activated carbon devices have 53 Wh g−1 energy density and 810 w g−1 power density.