Study On Synthesis And Electrochemical Performance Of β-NiS With Different Morphologies As Electrode Materials For Supercapacitors

In recent decades,supercapacitors have attracted main interests because they can provide higher power density than batteries and higher energy density than conventional dielectric capacitor,which probably make them the most important next generation energy storage device.Transition metal sulfides,such as Ni S、Cu S、Mo S2、Co S2,are a new type of energy storage material that have been greatly investigated and have achieved excellent electrochemical performances.Meanwhile,as one of the transition metal sulfides, Ni S has aroused interesting attention with the advantange of hige electronic conduction,low cost,ease of fabrication and low toxicity.In this thesis,different methods are used to synthesize different spatial structures β-Ni S microspheres and apply it as the electrode materials of supercapacitor.We use the physical and electrochemical testing method such as XRD、SEM、CV、GCD、EIS to study the physical characteristics and electrochemical performance of the preparred β-Ni S microspheres.The major study content is as follows:In this thesis, flower-like nickel sulfide assembled by nanoplates has been successfully synthesized via a template-free and one-step solvothermal method. At the same time, our experiment by adjusting the concentration of reactants, reaction time and concentration of the solvent, respectively explore the formation mechanism of this new structure and the synthesis conditions. CV、GCD、EIS are used to study the electrochemical performance and obtain a higher specific capacitance and more stable cycle performance,which probably make them the most important electrode materials for supercapacitor.In the third chapter of this paper, the porous β-Ni S microspheres are synthesized by a two-step hydrothermal method.The precursor is characterized by XRD and SEM.We study the influence of temperature on the evolution of this porous β-Ni S microspheres and analyze relationship between the structures and the capacitive properties of active materials. Cyclic voltammetry(CV), constant current charge-discharge(GCD) and electrochemical impedance spectroscopy(EIS) are used to study the effects of microstructure and morphology of the samples on their electrochemical performance. The porous β-Ni S microspheres(160 ℃),a capacitance of 1051.7 F g-1 is obtained at the current density of 2 A g-1.Such excellent electrochemical performance can be attributed to the porous microspheres structure.