Preparation And Electrochemical Performance Of Light Graphene/Carbon Aerogels

Supercapacitor is a new interesting energy-storage component with high energy density,fast charge-discharge speed and long cycle lifetime.Due to the high specific surface area,good electrical conductivity,good chemical inertness,controllable cellular structure of carbon aerogel（CA）,it show better application potential in energy storage than other electrical candidates.In this study,we optimized the safe and facial ambient drying process to prepare CA,studied the modification method of conductive graphene oxide（GO）and influence of GO on sol in order to promote the dispersion salability of GO,and KOH chemical activation which adjust pores of CA to improve its properties.The relationship of preparation,structure and electrochemical properties of CA and RGO/CAs is identified.A cheap safe process for the preparation of high specific capacitance RGO/CAS is invented.The research results are as follows:（1）The elaborate pores of CA affect its electrochemical performance significantly.Resorcinol（R）and formaldehyde（F）with a molar ratio of 0.64 were used as precursors,distilled water was the solvent,and Na₂CO₃（C）was the catalyst.The influence of precursor content and R/C on the apparent density,microstructure morphology and electrochemical properties of CA were studied.The apparent density of CA increased from 0.41 g/cm³ to 0.54g/cm³ as the precursor content increases from 20%to 40%,and the colloidal particles of aerogel is denser.As increasing R/C from 200 to 1000,the linear shrinkage of CA decreases and its density decreases from 1.13 g/cm³ to 0.41 g/cm³.When the precursor content is 20%and the R/C is 1000,the prepared CA has 583m²/g specific surface area and shows the best specific capacitance of 102.95F/g（0.5A/g）.（2）Due to the high specific surface and excellent conductivity of two-dimensional GO,theoretically introducing GO into CA can improve its specific capacitance.However,experimental results show that the stability of GO in water was quite poor,and GO without modification actually reduces the specific capacitance of CA.By comparing the effect of hexadecyl trimethyl ammonium bromide（CTAB）and sodium dodecyl benzene sulfonate（SDBS）surfactants on the dispersion stability of GO,20g/L GO solution modified by CTAB show better stability.The influence of modified GO 0.5wt%～2wt%contents on the apparent density,specific capacitance were discussed.The introduction of modified GO can inhibit the shrinkage of CA during the ambient drying,and made low apparent density samples.With the increase of GO content,the linear shrinkage rate and apparent density of CA first decreased and then increased.The linear shrinkage rate of RGO/CAs with 1.5wt%modified GO was 24%and apparent density was as low as 0.13 g/cm³.The addition of appropriate and dispersed GO in the sol-gel process separate gel,relieve the stress and inhibit the shrinkage.The specific capacitance of the CA electrode sharply increased to 177.8F/g（1A/g）.（3）Chemical activation can make new pores and enlarge the nano pores of CA.The effect of different mass ratios of KOH to carbon on the microstructure,specific surface area and specific capacitance of Ca and RGO/CAs was studied.When the mass ratio of KOH to carbon is 4:1,the specific surface of the activated CA and RGO/CAs increase to 1014m²/g and875m²/g,respectively.KOH activation can increase the micropores and small mesopores in aerogel,which lead to improve the energy storage of materials and promote the transport of electrolyte ions.The specific capacitance of the activated CA electrode and RGO/CAs electrode was improved by 61.3%to 159F/g（current density 1A/g）and by 33.9%to 238F/g（current density 1A/g）,respectively.