Hydrothermal Synthesis Of Metal Sulfides Nanosheets As Supercapacitors Electrode

The electrochemical capacitor (supercapacitor) is a new type of energy storage device. Compared with the traditional capacitor, it displays high power density, environmentally friendly, low cost, excellent transient charge and discharge performance, and the advantages of long cycle life. It can be applied in the beginning of the hybrid power supply and power supply application and has attracted the great attention of people. Key factors influencing the performances of supercapacitor is the electrode material. In order to improve the performance of supercapacitor, the most important is to develop novel materials.2D transition metal sulfide has unique nanostructure and electrical properties. It has attracted great attention in of the field of energy storage. In this article, we used simple hydrothermal method to prepare layered molybdenum disulfide (MoS2), cobalt sulfide (CoS) and copper sulfide (CuS). Their morphologies were characterized through X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscope (SEM) and transmission electron microscopy (TEM), and their electrochemical properties were test by cyclic voltammograms, constant current charge and discharge, and electrochemical impedance. The experimental results showed that this kind of metal sulfide nanosheets have good electrochemical performance and cycle stability, which was due to their unique layered structure, large specific surface area and fast electron transfer rate. The main works are listed as follows:(1) A simple hydrothermal method was used to prepare layered molybdenum disulfide (MoS2) nanosheets, and their morphologies were characterized through the X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscopy. The electrochemical properties of the material were tested by cyclic voltammograms, constant current charge and discharge, and electrochemical impedance. At current density of1A g-1, the MoS2nanosheets showed the specific capacitance of129.27F g-1. In addition, MoS2electrodes still kept85.1%in specific capacitance after500circles of charge and discharge, which indicated its good application in the construction of supercapacitor. (2) Under the aid of1-cysteine, one-step synthesis of layered CoS was performed. The cobalt sulfide sample has a microstructure of interconnected nanosheets. As electrode material for supercapacitors, the layered cobalt sulfide film exhibits superior performances with high specific capacitances (1314F g-1at3A g-1) as well as excellent cycle life (less than8.3%decrease in specific capacitance after500cycles at3A g-1), making it suitable for high-performance supercapacitor application. These excellent performance was due to CoS unique layered structure, large specific surface area and fast electron ion transfer rate.(3) CuS nanosheets were prepared with a hydrothermal method by using CuCl2-6H2O as copper source and thiourea as sulfur source, and were used as a novel supercapacitor electrode material. Layered CuS showed good electrochemical performance with specific capacitance of437.1F g-1at3A g-1. Also a good cycle stability was obtained. These were due to their large specific surface area and good electrical conductivity.