以活化碳纖維電極及PVdF膠體聚合物製備嵌入式多功能儲能複合材料-電化學與力學性能探討

Abstract

本研究成功開發出一套儲能複合材料的標準化製程，其中以活化碳纖維電極、PVdF膠體電解質(gel polymer electrolyte)，製作超級電容，並透過氟碳樹脂與環氧樹脂兩步驟的封裝方式將超級電容嵌入至玻璃纖維複合材料中，達到能同時承受負載與儲能的結構超級電容複合材料。此外，本研究首先針對碳纖維電極的活化方法與PVdF膠體電解質進行了研究，接著進行碳纖維電容器的製備與與封裝，利用恆電流充放電、循環伏安法及交流阻抗法來分析相關的電學性質，結果顯示在10 mA/g電流密度充放電下，具有167 mF/g的電容值及實際能量密度140 J/kg，相比於封裝前分別提升了約20%與30%，這是由於灌注時的真空壓力所影響。以拉伸試驗探討將超級電容器嵌入至玻璃纖維複合材料前後的力學性質，嵌入後平均應力仍有350.1 MPa，楊氏模數為14 GPa。為了解多功能儲能複合材料電學性質隨拉伸負載的變化，建立兩種負載變化的情形，觀察與分析電學性質。研究結果表明，兩種情形下，多功能儲能複合材料隨拉伸負載增加，相比於未受任何負載前，能量密度最大的變化率約為10%與12%，這是由於伯松比的效應，當材料受軸向拉伸時軸向伸長，側向收縮，使內部電容器受擠壓，電極距離改變，電性提升。而在玻璃纖維複合材料失效破壞前，超級電容器仍正常運作。最後將封裝後的成品置於空氣中，觀察十四天之間的衰變情形，儲能表現仍保有約96%。

This study demonstrates a standardized process to fabricate embedded multifunctional energy storage composites. Using Activated carbon fiber electrodes and PVdF-based gel electrolyte as building materials for supercapacitors. Two-step packaging method is used to fabricate glass-fiber reinforced polymer (GFRP) composites that can make it simultaneously bear mechanical loadings and store energy. Carbon fabric with three different activation methods and PVdF-based gel electrolyte are characterized by an electrochemical test. In addition, the electrochemical properties of the multifunctional energy storage composites are determined by galvanostatic charge-discharge (GCD), cyclic voltammetry and AC impedance method (EIS). The result shows that specific capacitance and energy density of supercapacitor with GFRP have 142 mF/g and 15.7 Wkg^(-1) provide 20% and 30% enhancement performance than a bare cell, respectively. The mechanical properties of the supercapacitor embedding of GFRP are investigated by tensile test; the result shows the average stress of 350.1 MPa and Young’s modulus of 14 GPa. Furthermore, to understand the electrical properties of multifunctional energy storage composites with external load changes, two different situations were also established. With the tensile load increase, the supercapacitor energy density is increased by around 10%, and the structural supercapacitor undergoing cyclic tensile is still functioning normally before the GFRP failure load.