Production and characterization of co-containing nis-based films for supercapacitor applications

NiS is promising as a supercapacitor electrode with its high electrical conductivity, mechanical/thermal durability and high theoretical specific capacitance. However, its semiconductor nature, which limits its charge storage properties, poor cyclic performance/stability, and stacking/clumping problems resulting from manufacturing during the transition from powder form to electrode form limit device performance. Therefore, it is necessary to improve the supercapacitor electrode performances by producing NiS electrodes in the form of coatings containing nanostructures. In this context, it is also important to increase the limited studies on the metal adding process. In this thesis, high amounts of Co element were added into NiS to minimize the factors limiting the supercapacitor applications of NiS electrodes. All electrodes were grown directly onto Ni foam substrates by hydrothermal method. NiS, CoS and Co containing NiS electrodes were produced in 2-dimensional nanoleaf structures and by adding high amounts of Co, the goal of developing NiS-CoS binary sulfur systems as unique supercapacitor electrodes was achieved. Structural and surface properties of all electrodes were examined in detail by taking XRD patterns and FESEM images. Additionally, their charge transfer kinetics were determined by EIS technique. Their potential use as a supercapacitor electrode was investigated from cyclic voltammetry and galvanostatic charge-discharge measurements. The contributions of capacitive effects and diffusion controlled processes to the current were determined by the Dunn method. As a result of all analyses, it was determined that NiS electrode had high specific capacitance and CoS electrode had high cyclic stability. It was concluded that the 75% Co-added NiS electrode produced as NiS-CoS binary sulfur system is a more suitable material for supercapacitor applications due to its high areal specific capacitance and high stability compared to other Co-containing electrodes.