Structure variation of nickel cobalt sulfides using Ni foam and nickel salt as the nickel source and the application on the supercapacitor electrode

Abstract The nickel cobalt sulfide is one of the promising electroactive materials for energy storage devices. The morphology of the nanomaterial has been widely designed with high surface area and high conductivity to enhance the charge storage ability. Based on the hydrothermal reaction and using the nickel foam which releases nickel ions during the reaction as the substrate, the influences of the nickel source on the morphology of the nickel cobalt sulfide and the pertinent supercapacitor (SC) performance are worthy to be discussed. In this study, the nickel ions are provided by the nickel foam and the nickel salt in the hydrothermal reaction for synthesizing the nickel cobalt sulfide, and the morphology variations as well as the corresponding electrochemical performance are investigated. The aggregation of the nickel cobalt sulfide is obtained at different regions in the nanosheets when different nickel sources are used. The optimized SC electrode shows a specific capacitance (C F ) of 2206 F/g measured by using the galvanic charge/discharge (GC/D) technique at the current density of 4 A/g, and the high-rate charge/discharge capacity is attained with a large C F value of 1655.8 F/g at the current density of 128 A/g. The excellent cycling stability of the 94.6% retention on the C F value after 2000 cycles repeated charge/discharge process and the Coulombic efficiency higher than 96% for the entire measurement are also achieved for this system.