Investigations On The Modeling And Preparation Of Hybrid Supercapacitors

Supercapacitor has been developed as a new type of energy-storage component following the development of material science. It has the ability both of fast charging-discharging as traditional capacitor, and of high energy-storage density as battery. It has got many applications, such as in electric vehicles, pulse power system, electromagnetism arms, UPS and forklift, and becomes a hotspot in energy technology.Hybrid supercapacitor has appeared in USA in recent years. Based on this new kind of supercapacitor, the relevant research for its modeling, preparation and testing are accomplished in deep. The first, a model of the composite electrodes with RuO2·xH2O/active carbon is set up based on the Conway model and electrode physical construction, the discharge characteristic at constant current is specially analyzed, and the regularity for change of the impedance and capacitance for composite electrodes at different mass ratios is explored. At the same time, the model for the typical pressed electrode is modified and improved, the characteristics of supercapacitor composed by pressed electrodes are analyzed, and the effect factors of inner resistance, capacitance and phase angle are discussed in theory.The key technology of supercapacitors is the preparation of their electrodes, the physical characteristics of porous electrodes determines the electrochemistry behaviors of the electrodes directly. The electrostatic fields of different apertures and shapes are simulated by finite element method to obtain the electrostatic fields distribution of the porous electrodes. The simulation results show that the electrostatic field and capacitance of porous electrodes will be improved by changing the apertures and shapes of the electrodes.In order to raise the working voltage of supercapacitor for pulse power system, a hybrid super-capacitor unit, which is composed of the anode of electrolytic capacitor and the cathode of supercapacitor, has been designed and studies. It has the merits of the electrolytic capacitor and supercapacitor, and enhances the working voltage of supercapacitor to improve energy density. The experiment results indicate the working voltage of the hybrid supercapacitor unit can achieve to 100V, energy density is 0.37J/g and power density is 8250W/g. Based on the hybrid supercapacitor unit, the hybrid supercapacitor module that has 100 parallel units is designed, and the simulation results validate that the module can satisfy the demand of fast charging and discharging at large current. When the load of 0.38 mΩ/10 mH inductance is discharged, the discharging current can be achieved to 2kA and the discharging power 200kW. Based on this simulated results, the hybrid super-capacitor module of 0.06F/3mΩ/0.3kJ is designed and studied on the experiments. The test results show that the hybrid super-capacitor module can fulfill the needs of pulse power system.At present, the performance of RuO2 is the best in the all materials, but the finite resource and dear price limit its more extended usage. In this work, two methods that mixed other material into RuO2·xH2O and prepared RuO2·xH2O by microwave have been used to improve the performance and usage of RuO2. According to the international foreland research, the composite electrodes of RuO2·xH2O, MnO2 and active carbon with different mass ratios were prepared and tested. The results show that the performance of composite electrodes is the best, when the mass ratio of RuO2·xH2O, MnO2 and active carbon is 20%:20%:60%. RuO2-xH2O which exhibits the super performance is prepared by the Sol-gel method improved by microwave and tested their electrochemical performances to make sure the process parameter, such as heating times. The experiment results exhibit that the performance of RuO2·xH2O is the best when the power is the mid-range output (power of 972W) and the heating time is 8min. The specific capacitance of this electrode is 806F/g, the inner impedance is 0.41Ω, and the maximum power density and energy density are 1.785kW/kg and 29.09Wh/kg, respectively.In order to research the charge and discharge performance of supercapacitors, in this paper, the constant current test system based on PIC microcontroller as the controller is designed. The software and hardware tests make further proving the maneuverability and stability of the system. Through the charging and discharging experiment for the hybrid super-capacitor, the results show that the system can obtain good constant current to satisfy the charging and discharging experiments for super-capacitor at large current.This work is supported by National Natural Science Foundation of China (No.50577075).