Nickel sulfide nanostructures for high performance supercapattery applications

Abstract

In this study, we engineered Nickel Sulfide (NiS) nanosheets using the Hydrothermal method by optimizing various parameters such as concentration, temperature, and time. X-ray diffraction confirmed the synthesis of crystalline nickel sulfide in two phases- namely millerite and hexagonal. We used Rietveld refinement to quantify the two phases, and it showed that Millerite and Hexagonal phases were present at 96.97 and 3.03 percent, respectively. BET showed the surface area for the synthesized NiS to be 9.7 m2 /g. The synthesized Nickel Sulfide was drop cast on Ni foam with the Nafion binder and tested for energy storage in a three-electrode pattern. Cyclic voltammetry showed that the NiS behaves like a battery-type electrode. Galvanostatic charge-discharge studies revealed that the NiS possesses a high specific capacity of 219 mAh/g at 1 A/g and excellent specific capacitance of 2693 F/g at 1 A/g. We also studied the cyclic stability at the current density of 2 A/g, and capacitance retained after 2,500 cycles was 73.6%. Corrosion studies showed that the corrosion rate was higher initially but reduced and became almost constant after 200 cycles. Hence, NiS nanosheets should be promising electrode materials for futuristic supercapatteries.