Research On Supercapacitor’s Preparation And Properties

Energy strategy is an important topic in the sustainable development, and energy storage devices play an important role in that area. As a new kind of green energy storage devices, supercapacitor has a broad application prospect in the new energy storage, power weapons, electric cars and other fields. This paper has carried out the research on the fabrication of electrode materials, design of electrical structure, electrical properties, thermal behivors and matched measurement system.Electrode materials determine the storage properties of supercapacitor. As a result, the research on supercapacitor’s storage properties should be based on the appropriate fabrication route of electrodes. In the research of electrode materials preparation methods, with sodium hydroxide as precipitant and nickel sulfate as the precursor, this paper proposes a dilution strategy to prepare nickel hydroxide (Ni(OH)2) as the electrode materials. This method is carried out by adjusting the precipitation concentration, namely adjust both the thickness of quartz sands in the isolation dilution and heating temperature in the reaction chamber to control the reaction rate. Through optimizing experiment parameters, the opitimal results appear at the condition that the thickness of the quartz sand control is2cm and the main reaction chamber heating temperature is115℃. X-ray diffraction (XRD) shows that the obtained sample is pure phase α-Ni(OH)2. Scanning electron microscope (SEM) shows the Ni(OH)2materials presents designed morphology. Electrochemical performance test shows that at the current of10mA, the first charge-discharge specific capacity is1000F/g. After200times, it stabilizes at930F/g (93%of the first cycle specific capacity). Experimental studies have shown that nickel hydroxide has high specific capacity and good retention capacity. Based on the above nickel hydroxide sample, we have also fabricated the nickel oxide (NiO) sample at300℃under N2atmosphere. The corresponding analysis shows that nickel oxide also has high specific capacity and good retention capacity. The nickel compound performance is not stable, and the practical applications require stable performance and easy making electrode materials. As a result, we have also fabricated the ordered mesoporous carbon taking hydrochloric acid as the catalyst, resorcinol and formaldehyde as the body, and F127as the template agent. XRD shows that the material has small crystal forms. SEM shows that the particle size is about10μm. Transmission electron microscopy (TEM) shows that its carbon wall with ordered pore structure is10nm. Electrochemical performance test shows that at the current of10mA, the first charge-discharge specific capacity is125F/g. After450times, it stabilizes at113F/g (90.5%of the first cycle specific capacity), indicating that the electrode material has good electrochemical performance.To promote the storage properties, both of stackable and spiral supercapacitors have been studied. For stackable supercapacitor, Ta/Ta2O5and ordered mesoporous carbon are employed as anode and cathode, respectively. The mass ratio of ordered mesoporous carbon, graphite and teflon is85:10:5. The simulation adopts two-dimensional asymmetric model with three units in parallel. The diameter is35mm, the height is15mm, working voltage is100V, capacitance value is5.1mF and internal resistance is0.45Ω. For the spiral supercapacitor, ordered mesoporous carbon is employed as the electrode material with symmetric structure. By optimizing the ratio of electrolyte, the electrolyte adopts1.5mol/L Et4NBF4/AN. The diameter is11mm, the height is22mm, working voltage is2.7V, capacitance value is12.38F and internal resistance is0.03Ω.Thermal behaviors have significant information in the application area of supercapacitor. Based on the temperature variation and distribution field of supercapacitor in the charge-discharge process at large currents, the finite element model is established according to stackable and spiral supercapacitors to analyze the thermal behaviors. Furthermore, the corresponding experiments are also employed to verify the simulation results. Simulation and experiment results in the stackable supercapacitor show that at the current of3A, the maximum temperature is37.5℃and appears at30times, and then it stabilizes. When the current is5A, the highest temperature is53.2℃with a sharp rise due to the current increasement. Simulation and experimental results in the spiral supercapacitor show that at the current of2A, the maximum temperature is42.5℃and appears at35times, and then it stabilizes. When the current is4A, the highest temperature is up to60℃. We have improved the porous model of supercapacitor to study the influence of temperature variation in the storage properties. Through the simulation analysis and experimental research we discuss the changing rule of impedance and self-discharge performance under different temperature gradient.In order to overcome the problem of low experiment current and power and improve experimental research method, we design a constant current charge-discharge and constant power discharge test system. The system adopts Buck-Boost converter circuit as the main circuit, DSP as the control core, through the voltage and current double closed-loop control to achieve constant current charge-discharge and constant power discharge. The voltage test range is0～100V. Current test range is100mA～10A, and the accuracy is0.9%. Constant power test range is0～500W.