Preparation of Electric Double Layer Capacitor depended on the effect of edge sites of grapheme structure

点击翻译按钮获取中文摘要

The following results were obtained for the past two years from April of 2005 to March of 2007.The aim of this first year from April of 2005 to March of 2006 was to prepare exfoliated mesocarbon microbeads(Ex-MCMB) to make a rectangular thin electrode.(1) Accordion-like exfoliated MCMB was obtained by rapid pyrolysis at 1000℃ of the intercalated MCMB with the mixed acid of sulfuric and nitric acids at the volume ratio of 4/1.(2) Expansion and disorder between aromatic carbon layers were observed from the results of X-ray powder diffraction profiles. The exposure of edge sites proceeded through exfoliation process of carbon layers.(3) Specific surface area and pore size distribution of the MCMB before and after exfoliation by Mercury Porosimeter showed the appearance of mesopore.The aim of the second year from April of 2006 to March of 2007 was to evaluate the performance as electric double layer capacitor by decrease of internal resistance between carbon current collector and carbon rectangular polarized electrode.(1) Exfoilation of MCMB successfully produced by use of MCMB graphitized at 2000 or 3000℃.(2) Specific surface area of MCMB graphitized at 2000℃ was largely increased from 0.8 m^2/g to 70 m^2/g by exfoliation. The adsorption isotherms of the exfoliated samples showed the behavior of type I dominated by micropore.(3) Electrostatic capacity of the electrode made from the Ex-MCMB based polarized electrode and carbon current collector showed five times as larger as the electrode made from PTFE, carbon black, and Ex-MCMB. In addition, contact resistance also decreased.(4) SEM images of the Ex-MCMB based polarized electrode showed that carbon coatings covered on the edge surface of exfoliated lamellar. The carbon coatings seemed to decrease the electrostatic capacity. Electrochemical oxidation, however, improved the electrostatic capacity up to 50 F/g.