含PVdF膠體電解質之結構超級電容複合材料研究 － 電化學性質與封裝製程探討

Abstract

本研究建立了一套儲能複合材料的標準化製程，以活化碳纖維電極、PVdF膠體電解質(gel polymer electrolyte)，製作超級電容，並透過環氧樹脂真空灌注法將超級電容嵌入至玻璃纖維複合材料中，成功開發出兼具儲電能力且能承受負載的結構超級電容複合材料。此外，本研究也針對多種碳纖維電極的活化方法與PVdF膠體電解質進行了研究。在碳纖維電極的部分使用了SEM與BET法來觀察纖維表面及分析比表面積，再以循環伏安法來測量比電容，活化纖維最高比表面積及比電容分別為22.23 m^2/g及7.36 F/g；在膠體電解質的部分則使用交流阻抗法、限制擴散、恆電流等方法在圓柱型電池系統中，分析離子導電度、擴散係數及遷移數等傳輸特性。接著使用恆電流充放電及交流阻抗法來分析結構超級電容複合材料，結果顯示在2 mA/g的電流密度下，活化碳纖維超級電容的比電容最高可達783.32 mF/g，最大功率密度與能量密度最高為62.65 W/kg及391.66 J/kg。最後將封裝後的成品置於空氣中，觀察七天之間的衰變情形，七天後其儲能表現仍保有約70%。

This thesis presents a standardized process to fabricate structural supercapacitor composites with activated carbon fiber electrodes and PVdF-based gel electrolyte. Furthermore, epoxy resin infusion package method was also used to embed the supercapacitor into glass fibers that can make it simultaneously bear mechanical loadings, store energy and prevent from deliquescence. Investigation of carbon fiber activation methods and PVdF-based gel electrolyte were demonstrated. Brunauer–Emmett–Teller(BET) surface area analysis, scanning electron microscope and cyclic voltammetry were conducted on the as-received and activated carbon fiber reinforcements. Activation method 2 had the best performance which had specific surface area of up to 22.23 m^2/g and capacitances of up to 7.36 F/g. Electrochemical impedance spectroscopy(EIS), restricted diffusion experiment and constant current method were conducted on PVdF-based gel electrolyte in a cylinder cell system to characterize the transport properties which are conductivity, diffusion coefficient and transference number. Electrochemical investigations of structural supercapacitor composites were made using constant current charge and discharge and EIS. Activated carbon fiber supercapacitor had specific capacitances up to 783.32 mF/g, power density and energy density up to 62.65 W/kg and 391.66J/kg with respect on 2 mA/g current density under charging and discharging. The electrochemical decay test after 7 days was also conducted on the epoxy-packaged supercapacitor composites. The composites kept up 70% of original performance at last.