Investigations On The Carbon Based Supercapacitor And Its Electrical Performance

As a novel kind of energy storage component, supercapacitor has high energy density, power density and cycle life. It has a wide application in the fields such as new kinds of electricity generation, pulse power system, electric vehicles and electromagnetism weapons.Firstly, in this paper, the supercapacitor was regarded as the research object. On the basis of the formation mechanism for the double layer capacity, the structure and properties of the electrode-solution was thoroughly studied. At the same time, the distribution and transmission characteristics of ions in the solution were discussed. After a summary of the models for supercapacitor, the matrix model of the double layer capacitor was proposed. On the basis of this mathematical model, the charges and voltage distribution in the inner side of the double layer capacitor was investigated. Meanwhile, the factors that influence the energy storage and self discharge mechanism of the doule layer supercapacitor was also discussed.Secondly, as regard to the field of the supercapacitor electrode, the electrochemical properties of carbon nanotubes (CNT) electrode and actived carbon/carbon nanotubes (AC/CNT) electrode, manganese dioxide/carbon nanotubes (MnO2/CNT) electrode, polyaniline/carbon nanotubes (PANI/CNT) electrode were studied. The influence of the electrode component on the capacitance was deeply investigated, and the PANI/CNT electrode had the best performance, which specific capacitance is245F·g-1, equivalent series resistance (ESR) was0.811Ω. In order to enhance the energy stroage character of the electrode material, the modification based on the oxygen plasma was proposed, and the modification was carried out on the electrode materials. Next, the comparison of different modification time on the electrode materials was investigated, and the results of lOmin modification treatment revealed that the hydroxyl functional group was introduced on the electrode materials, the micro morphology was uniformly distributed. Furthermore, as regard to the electrochemical properties, the impedance of each electrode was improved, the specific capacitance of PANI/CNT and MnO2/CNT electrode were320F·g-1and260.9F·g-1respectively, which were1.3and1.27times of the electrodes before modification. The ESR of PANI/CNT and MnO2/CNT electrode were0.32Ω and0.35Ω, which were reduced by60.5%and60.7%respectively after10min modification. This demonstrates that the plasma modification is suitable to the optimized preparation of the electrode material. Thirdly, the polyvinyl chloride (PVC) was used as the packaging material and the electrodes as prepared were stackingly assembled in the037mm×10mm cylinder PVC package. The charge-discharge tests were conducted. The results revealed that the best capacitance maintaince of the three series connected module was98%after1000cycles.Finally, in the fields of energy storage system, pulsed power system and other high power sources, especially the system based on the supercapacitor, the capacitors need to be series connected in order to fulfill the need of the load due to its low unit voltage. Actually, each unit of the series is inconformity owing to the manufacture technique and operating environment, so the voltage between the units is also imbalanced during the charge process. The voltage balance system based on the PIC microchip unit was designed in this paper in order to solve this problem. The balance system consisted of voltage acquisition unit, controlling unit and main circuit, which in order to achieve the balanced voltage of each unit during the charging process and the maximum efficiency of the energy storage system. As regard to the energy storage system consists of10series connected55V9F supercapacitor module, the experiment results demonstrated that this system could realize the balanced charging in the range of0-20A,0-550V.