Chemical Synthesis And Performance Study Of Supercapacitors Electrode Materials

To deal with the growing energy crisis and environmental problems,the development of clean and sustainable energy sources with high powerdensity and low cost is extremely urgent. In the past years,supercapacitors (also called electrochemical capacitors) with high powerdensity, long cycling life and low cost have attracted much attention, andhas show great potential applications in areas such as uninterruptiblepower supplies, hybrid electrical vehicle systems and renewable energies.In general, supercapacitors can be classified into two types based on thecharge-storage mechanism. One is the electrical double-layer capacitors,and the other is the pseudocapacitors.The key factor that determines the electrochemical capacitorperformance is the choice of electrode materials. Therefore, thedevelopment of appropriate electrode materials can increase thecapacitance of supercapacitors. In this paper, we have studied thechemical synthesis of several different kinds of supercapacitors electrodematerials, and tested their electrochemical energy storage properties. Themain contents are summarized as follows:1. Through the control over hydrothermal conditions (reaction time andtemperature), ternary nickel cobaltite with four different morphologyincluding hexapods, hexagonal prisms, nanowires and hexagon piecewere prepared by using different cobalt source, nickel source and alkalinesubstances. The products were investigated by X-ray powder diffraction(XRD), X-ray photoelectron spectra (XPS), thermogravimetric analysis(TDA), scanning electron microscopy (SEM) and transmission electronmicroscopy (TEM). According to the nitrogen adsorption desorption testand electrochemical performance test, the influence of specific surfacearea and pore size distribution on the capacitive behaviors were studied.2. NiCo2S4hollow hexagonal nanoplates with an average diameter ofabout200nm, thickness of about50nm, and the shell thickness of about 10nm were successfully prepared through a two steps hydrothermalmethod by using Ni-Co double hydroxide precursor nanoplates as thesacrificial templates. The samples were characterized by XRD, XPS,EDX, SEM and TEM. The electrochemical capacitance of the as-obtainedNiCo2S4samples was also examined.3. By using the waste biomass–lotus seedpod shells as raw materials,porous carbon material was obtained through directl carbonization. Thecarbon materials were characterized by means of XRD, XPS, N2adsorption desorption test, SEM and TEM. It can been found that theas-obtained carbon materials which prepared under600°C have a highBET surface area of563.4m2g1, and the average pore size is2.2nm.When act as the electrode materials for supercapacitors, the specificcapacitance is165Fg1, indicating the high ratestability.4. Co9S8nanotube arrays with hexagonal cross sections weresuccessfully grown on Ni foam through Kirkendall effect. Thecomposition of the products was characterized by XRD and XPS. Themorphology was investigated by SEM and TEM. The results show thatthe diameter of the Co9S8nanotubes is about120–200nm and the wallthickness is of40–60nm. When act as supercapacitors electrodematerials, it shows a specific capacitance of1775Fg1, and a retention of91.4%of the initial capacitance after2000cycles.5. The interlaced Ni-Co LDHs nanosheets arrays were grown on nickelfoam by a hydrothermal method. The samples were characterized byXRD, XPS, SEM, and TEM. The nanosheets are uniform, with anaverage size of about20nm. As the electrode materials forsupercapacitors, it showed a high capacitance of1735Fg1.