Study On Activated Carbon Electrode Materials Based On Phenolic Formaldehyde Resin For Electric Double Layer Capacitor

An electric double layer capacitor(EDLC) is an electrochemical energy storage device with high power density, high energy density, long cycling life and environment friendly, which could be used in applications such as memory back-up devices or electric vehicle, and so on. The EDLC's performance highly depends on the electrodes materials. Among the various of electrode materials, activated carbon materials have significant advantages for preparing the electrodes, due to their low cost, high surface area and perfect chemical stability. They have been received great attention as electrode materials in the fabrication of EDLC.In this paper, the high specific surface area activated carbon for double layer capacitors was prepared by NaOH activation. The effect of activation temperature on the structure and capacitance performance of phenolic resin carbon was investigated systematically. The phenolic resin based micropore carbon prepared under the alkaline/carbon=2:1 had the specific surface area of 1864m2/g and the pore size of 0.5～2nm. The EDLC in the 30wt% KOH aqueous solution showed high specific capacitace. The cyclic vatammetry was indicated that activated carbon prepared by different activated temperature electrodes exhibited excellent cycle performance.Secondly, activated carbon for electric double layer capacitor application was prepared by steam activation of resole phenolic formaldehyde resin under the temperature of 900℃through changing the activating time. It was found that the BET specific surface area and the mesopore ratio of the activated carbon were increased with the activating time, 1819m2/g and 12.6% respectively for PFR5H. The electrochemical test indicated that the model EDLC showed the highest specific capacitance of 106.5F/g in organic system with the current of 50mA/g. When the current was 1000mA/g, the specific capacitance remained 99.7F/g and only decreased 6.4% in the same system. It showed good rate characteristics. AC impedance analysis also exhibited the lowest resistance, resulting in remarkable specific capacitance and good power capability.AC-Ni composite electrode materials were prepared by doping nickel acetate into phenolic resin followed by proper carbonization-activation process under the temperature of 900℃with CO2 as activating agent. Constant current charge-discharge cycling indicated that the AC-Ni composite electrodes had higher capacitance of 162.8F/g, which was 20.4% more than that of the AC electrodes of 129.6F/g. X-ray diffraction suggested that the metallic nickel was well dispersed in the composite electrode materials.