Preparation And Super Capacitor Performance Of Mesoporous Electrode Materials

In this paper, based on the review of the research and development of supercapacitors, mespouse materials were studied as supercapacitor electrode material.These materials were synthesized by hard-method.And their structural, morphological,and specific area were characterized by means of X-ray diffraction (XRD),transmission electron microscopy (TEM), and nitrogen adsorption-desorption, while galvanostatic charge/discharge, cyclic voltammetry and AC (alternating current) impedance were performed to investigate the electrochemical performance.In chapterⅡ,ultrasonic-dipping method was used to prepared mesoporous MnO2 from SBA-15 as "hard template" and Mn (NO3)2 as Mn source. The product showed BET surface of 282 m2·g-1 and pore diameter of 2.79 nm and exhibited a specific capacitance of 298.3 F·g-1,which maintained 243.6 F·g-1 after 500 cycles.Then mesoporous carbon was fabricated via an impregnation process combined with carbonization treatment and SBA-15 as "hard template".The resultant carbon had average pore of 3.05 nm,surface area of 578 m3g·g-1.The material performed good electrochemical double-layer abilities in the potential range of-0.2～1.0 V. The specific capacitance were 86,78,60,53,48 F·g-1, corresponding the scanning rate of 5,15,30,50,100 mV·s-1.At the current density of 0.3A·g-1,its specific capacitance maintained 96.4 F·g-1 with litter than 10% attenuation after 1000 cycle times.In the preparation of mesoporous manganese dioxide process,calcination temperature is the key factor. We detailed study the impacts of calcination temperatures on the structure/phase, and the electrochemical capacitance in chapterⅢ.The sample calcined at 200℃was not completely, and partly decomposited of manganese dioxide at 500℃.And the MnO2 samples were more pure at the calcinaion tempreture of 300℃and 400℃.With calcination temperature increasing, the amorpphous samples reduced.The ESR of these samples obtained at different tempretures were 1.41,0.79,1.16,1.91Ω, respectively,and their initial discharge capacity were 260.7,298.3,289.9,185.9 F·g-1.Asymmetrical-supercapacitor was assembled used mesoporous MnO2 as positive electrode, and mesoporous carbon as negative. Cell voltage of the supercapacitor was up to 1.8 V at a current density of 100 mA·g-1.In this voltage, the specific capacitance and energy density all reached maximum.Besides, with the increasing of charge/discharge current density, specific capacitance and energy density all decreased.On the contrary, resistance and power density all increased greatly. At conditon of 100 mA·g-1 and 1.8 V, the power density and energy density of the mesoporous carbon/MnO2 asymmetric supercapacitor were 89.0 W·kg-1,31.3 Wh·kg-1.It also had a specific capacitance of 76.7F·g-1 and retained 69.5 F·g-1 after 1000 cycles.