Preparation And Supercapacitor Performance Of NiS/nitrogen-doped Carbon Nanotubes

Ni S/NCNTs composites are prepared by hydrothermal synthesis method or high-temperature pyrolysis method, which NCNTs is a raw material. X-ray diffraction(XRD), Scanning electron microscopy(SEM), Transmission Electron Microscope(TEM) and specific surface area analyzer are used to characterize the surface morphology, structure and composition of material. Cyclic voltammetric(CV) measurements, electrochemical impedance spectrum(EIS) and constant current charge-discharge are used to discuss the electrochemical performance of the composite materials. The main results of this paper are as follows:Ni S/NCNTs composite was successfully synthesized by a hydrothermal method, which NCNTs is used as a matrix material. Ni S contained α-Ni S and β-Ni S. It was found that the surface morphology of composite material and electrochemical properties are controlled by the weight ratio of nickel salt and NCNTs. α-Ni S and β-Ni S are deposited on the surface tubes uniformly with smaller grain size and composite material has a high surface area under the weight ratio of nickel salt and NCNTs is one to four, because NCNTs can provide more active sites for electrochemical redox reaction and modify the charge transfer. Therefore, it can contribute a high specific capacitance of 102 F·g-1 in the discharge current of 0.1 A·g-1, and the specific capacitance remains 80.5% of the initial after 1000 cycles.α-Ni S/NCNTs composite was synthesized by a high-temperature pyrolysis method, using NCNTs and nickel diethyl dithiocarbamate as raw material. The results show that the pyrolysis temperature effects the composition, surface morphology and the electrochemical performance of composite. α-Ni S are deposited on the surface tubes uniformly with smaller grain size. The composite prepared at the temperature of 500℃(named as α-Ni S/NCNTs-500) has the highest surface area, proper porosity, high α-Ni S loading amount and uniform distribution. One the one hand, α-Ni S can provide pseudocapacitance, and on the other hand, NCNTs can modify the hydrophility of the electrode material, and also provide more active sites for electrochemical redox reaction and modify the charge transfer and further enhance pseudocapacitive behavior and cycling stability, so as to improve the electrochemical performance of electrode materials. The specific capacitance is 133 F·g-1 in the discharge current of 0.1 A·g-1, and it remains 76% of the initial capacitance after 1000 cycles, which contain a good application in the field of supercapacitor, due to satisfied structure characteristics, excellent electrochemical performance and relative stable cycle performance.