Preparation And Modification Of Carbon Aerogel As Supercapacitor Electrode Material

Supercapacitor is a new kind of energy storage device, between conventionalcapacitor and second battery. It was wildely applied in military and civil fields. Theelectrode is a key factor influcing the performance of capacitor. Therefore, theresearch of high performance electrode materials has great signficance.The purpose of this study is to prepare high performance carbon aerogelelectrode materials for supercapacitor. The FTIR spectroscopy was used to study thefunctional group of organic aerogel precursors, the SEM was used to study themorphology of carbon aerogels. The properties of supercapacitor, such as specificcapacity, and charge-discharge stability were studied by electrochemical methods,including, cyclic voltammetry, constant current charge-discharge, etc. in 6mol/LKOH aqueous solution. This work was carried out as following:Carbon aerogels were prepared by the sol-gel polymerization of resorcinol (R)with formaldehyde (F), then followed by ambient drying process and carbonisation.Using metal hyoxide as catalysts, the effect of catalyst and ratio of resorcinol tocatalyst(R/C ratio) on morphology and electrochemical property of carbon aerogelswas investigated. It was found that, the R/C ratio is the key factor in controlling thestructure of carbon aerogel. The reactant pH difference with respect to catalyst andR/C affects the morphology and specific capacitance. As the pH decreasing, themorphology of carbon aerogel changed greatly, from bulk structure to spherical ones,and the specific capacitance of carbon aerogels firstly increased then decreased.When Mg(OH)2 used as catalyst, among the samples, the carbon aerogel prepared atR/C ratio of 5087 showed the highest specific capacitance, the discharge specificcapacitance was 119.4F/g at 10mA. The carbon aerogels prepared using Al(OH)3 ascatalyst at R/C ratio of 2.69×109 exhibited highest specific capacitance about129.2F/g at 10mA. In the case of Ca(OH)2, the sample was prepared at R/C ratio of74 which showed highest specific capacitance about 132.9F/g at 10mA. In the case ofNaOH, prepared at R/C ratio of 1000 show highest specific capacitance about124.1F/g at 10mA. Their performance for supercapacitor electrode was investigatedby cycle life test, and showed stable cyclability after 500 cycles of constant currentcharge-discharge at 10mA.In order to improve the electrochemical property of carbon aerogels, weprepared organic polymer-modified and metal-doped carbon aerogels. In the case ofthe organic polymer (Span80, PEG, F127)-modified carbon aerogels, with anincrease of additive content, the capacitance increased. It reached a maximumcapacitance when 0.5 wt.% was added. When additive content was higher than 0.5 wt.%, however, the electrochemical activity decreased. Among additive-modifiedcarbon aerogels, F127-modified carbon aerogel showed the highest capacitance(146.7F/g), and stable cyclability. Various metal (Ni, Co, and Mn)-doped carbonaerogels with a variation of resorcinol to metal ratio (R/T ratio=5, 10, 100) were thenprepared and their electrochemical performance for super-capacitor was examined.With an increase of metal content, the capacitance increased. Among the metaldopedcarbon aerogels, Mn-doped carbon aerogel exhibited the higher capacitance,the sample prepared at R/T ratio of 100 show highest specific capacitance about140.8F/g at 10mA, 125.6 F/g at 50mA and stable cyclability.