Study on the preparation and electrochemical performance of nickel sulfide for the application in an electrochemical capacitor

NiS as an electrode material for electrochemical capacitors has been synthesized by chemical and hydrothermal methods. The results show that the synthesized NiS is in amorphous form, increasing the reaction temperature or hydrothermal time tends to reduce the porosity of the materials. NiS synthesized by hydrothermal method exhibits better electrochemical properties than those synthesized by chemical method. NiS synthesized at the optimal condition of a hydrothermal temperature of 140 oC in 5h has a specific capacitance of 1592 F\g (265 mAh\g) and 1567 F\g (261 mAh\g) at a scan rate of 5 mV\s and a current density of 5 A\g, respectively. This value is about 88% of the theoretical value of NiS and is maintained after 25 continuous charge-discharge cycles at different current densities ranging from 5 to 40 A\g.