Research On Carbon Based Double Layer Capacitor Of Low Internal Resistance

Double layer capacitor is a new type of energy storage component in recent years, it integrates the advantages, such as the high power density characterized by conventional capacitors, the energy density characterized by rechargeable batteries, the fast charge/discharge performance and the long life. So the component is expected to be a power source with high efficiency and practicability. However it may take a long time to employ it in practical application because of its low operating voltage and high equivalent series resistance. The double layer capacitor will have good performance of discharge with low equivalent series resistance, and be likely to achieve high load current discharge. Therefore low equivalent series resistance was already one of the most important characteristic which a double layer capactior with excellent capability should have. This research on reducing the equivalent series resistance of double layer capacitor brings abroad application foreground and has great significance and applied merit. We used activated carbon to make up the double layer capacitors in this paper,analyzed the formation mechanic of its equivalent series resistance, and searched how to reduce the equivalent series resistance of double layer capacitor in order to show its excellent capability.The most important factors influencing the equivalent series resistance of the double layer capacitors are the resistance of polarize electrode and collector electrode themselves, the resistance of electrolyteand,the hole and the thickness of separator material, the contact resistance among the polarize electrode, the collector electrode and the down-lead. This paper designed various experiments to study double layer capacitor's electric performance .These experiments are basing some different methods such as constant current method, cyclic voltammograms, electrochemical impedance spectroscopy. Summarized the effective measures to reduce the equivalent series resistance of the double layer capacitors through theoretically analysis and experimental validation: Using low resistance ratio and high-powered material to make polarize electrode with well manufacture technics, the polarize electrode which was manufactured by ourselves has the optimal performance; Using the right electrolyte with appropriate material and concentration, for instance using the KOH liquor of 6～8mol/L concentration was the best; Using the separator material which is lacunaris, rigid and super filmy. Making several inner cell parallel connection and take the air out from the container during the assemble process,also can reduce the equivalent series resistance of the double layer capacitors effectively.In the end, we manufactured the polarize electrode with high capacitance and low resistance by using the industrial activated carbons with high specific surface area as the main material. The single polarize electrode with high ratio capacitance up to 116.065F/g was manufactured, and the single capacitor with capacitance up to 7.962F and the equivalent series resistance up to 0.113Ωwere manufactured. The prototype product of double layer capacitor with capacitance up to 101F and equivalent series resistance up to 0.030Ωwas prepared.