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標題: | 利用高分子設計以優化離子傳導膜及其在次世代能量系統中的應用 Optimization in Polymer Design for Ion Conduction Membranes Used in Next-generation Energy Conversion Systems |
其他標題: | Optimization in Polymer Design for Ion Conduction Membranes Used in Next-generation Energy Conversion Systems |
作者: | 黃紹齊 Shao-Chi Huang |
指導教授: | 戴子安 Chi-An Dai |
關鍵字: | 燃料電池,陰離子交換膜,鋰金屬電池,枝晶鋰,膠態電解質,聚乙二醇,小角度X光散射, Anion exchange membrane,fuel cells,lithium metal battery,lithium dendrite,gel polymer electrolyte,poly(ethylene oxide),small angle X-ray scattering (SAXS), |
出版年 : | 2022 |
學位: | 碩士 |
摘要: | 本論文主要開發電池所用之離子傳導膜,內容分成兩部分,第一部分在於開發燃料電池(fuel cell)中之陰離子交換膜(anionic exchange membrane),第二部分則為製備鋰金屬電池(lithium metal battery)中之膠態電解質膜(gel electrolytic membrane)。
論文的第一部分為開發應用於燃料電池之陰離子交換膜。近年來陰離子交換膜受到廣泛關注,主要是此類電池不需要使用貴金屬催化劑,大幅降低了燃料電池之組裝與成本。並由於陰離子交換膜為重要的組件,大幅影響電池之產電效率。因此性能良好之陰離子交換膜需具備高機械性質、高導電率與高鹼穩定性。為此,於本研究中我們利用聚苯乙烯-b-聚丁二烯-b-聚苯乙烯嵌段共聚物(styrene-butadiene-styrene block copolymer, 又簡稱 SBS)作為陰離子交換膜之基材,並進行化學改質以製備陰離子交換膜。SBS為價格便宜之商業化材料並具備自組裝特性,因此藉由化學改質之SBS陰離子交換膜會產生親水/疏水微相分離結構進而構建離子通道使導電率上升。同時,作為彈性體之SBS亦賦予陰離子交換膜良好之機械性質使其能在燃料電池中穩定運作。在本研究中,我們分別使用均相接枝法與非均相接枝法製備陰離子交換膜,並探討此兩種不同方法對陰離子交換膜性能之影響。最後我們發現利用非均相接枝法所製備之陰離子交換膜具有良好的機械性質及熱穩定性且其導電率可以達到7.3 ms/cm,並具備良好之熱穩定性、鹼穩定性與低溶脹率,顯示未來之應用性。 論文第二部分為製備下世代鋰金屬電池之膠態電解質。近來使用傳統液態電解液之鋰金屬電池通常會面臨電解液洩漏、乾涸與枝晶鋰(lithium dendrite)問題。然而膠態電解質能利用自身高分子交聯網絡把有機溶劑固定於膜內,故被認為是能有效解決電解液洩漏之最佳手段,同時膜內之有機溶劑亦能幫助傳導使膠態電解質之導電率不亞於液態電解液,若是能利用良好的高分子設計使膠態電解質具備合適之機械強度,同時亦達成抑制枝晶鋰的目的,將使鋰金屬電池之耐久性及安全性更佳。本研究欲開發以聚乙二醇(poly(ethylene oxide,或簡稱PEO))為基材之膠態電解質膜,雖然PEO膠態膜已受到廣泛研究,不過以PEO為基材所製備之膠態膜通常延展性不佳,易受到電極充放電時體積的變化而碎裂,使鋰沉積變得不均勻,預防枝晶鋰之效果受大打影響。在本研究中,我們透過添加不同含量之長短鏈交聯劑,利用簡易的光聚合交聯法調整膠態電解質中物理交聯與化學交聯之比例,以調控膠態膜之機械強度;同時也通過改變膜內有機溶劑之添加量以調控膠態電解質之導電率。最後所製備出之膠態電解質其延展性最高可以來到125%,且導電率達0.63 ms/cm,這使得電池以0.5 mA/cm2 之電流進行充放電循環時,於100圈後仍能有效抑制枝晶鋰之生成。 最後,透過小角度X光散射實驗分析膠態電解質於奈米尺度下之結構,通過小角散射的特徵峰可得知膠態膜之交聯網絡為非均質之星狀網絡而非均質之網狀網絡,且該星狀網絡會於膜內呈現階級性聚集結構。更進一步藉由聚集結構之碎形維度(fractal dimension)與碎形網絡區域(fractal network region)大小之分析以預測膠態電解質之導電率。實驗結果顯示,當膠態電解質內之階級性聚集結構其碎形維度達到3時,整個結構是較不利於離子傳導,且導電率會有大幅地下降。 In this thesis, two different types of ionic transporting membranes are developed. One is anion exchange membrane (AEM) for fuel cells (AEMFCs) application and the other is gel electrolytic membrane for lithium metal battery. Since AEM based fuel cells do not require the use of precious metals like platinum as catalyst, they have recently attracted widespread attention. Therefore, for the first part of the thesis, high efficient and mechanically robust AEMs are developed. In addition, AEMs are important component used in AEMFCs with their performance strongly affecting the power efficiency. Therefore, an optimized AEM must have high ionic hydroxide conductivity, adequate mechanical property, and superior stability in alkaline solution for long service time. To this end, we propose to use a triblock copolymer of polystyrene-b-polybutadiene-b-polystyrene (SBS) as the main AEM material used in this study. The commercially available and inexpensive SBS forming self-assembled structure can be used as a structural template of ionic channels for efficient hydroxide ion transport due to its microphase-separated structure. In addition, elastomeric SBSs may further provide improved mechanical strength as long-term durable AEMs. In this study, the AEM membranes were made by two methods, homogeneous and heterogeneous reactions. We will discuss the performance differences between the thus chemically modified SBS membranes using the two methods. The resulting AEM (SBS-QA) made by heterogeneous method shows not only good mechanical properties and hydroxide conductivity (7.3 ms/cm) but also exhibit excellent thermal stability at high temperatures. These superior properties demonstrated in this study indicate that SBS-QA is a promising AEM material for future application for AEMFCs. In the second part of the thesis, gel electrolytic membranes are designed and fabricated for lithium metal battery. Lithium metal is regarded as one of the optimal anode materials for next-generation lithium ion batteries because of its high energy density. However, problems of lithium dendrite, solvent leakage and dried-up of liquid electrolyte are the common problem in lithium metal batteries. Gel polymer electrolytes (GPEs) is considered to be one of the best solutions to effectively solve the leakage of solvent due to its ability to keep the organic solvent within the cross-linked network of the gel. Also, the conductivity of GPEs is can be nearly equal to that of liquid electrolyte depending on its concentration. At the meantime, if GPEs exhibit sufficient mechanical properties, lithium dendrites growth can be suppressed further, enhancing the durability and safety of lithium metal batteries. In this study, a highly malleable PEO-based gel polymer electrolyte is developed to prevent GPEs from structural degradation due to volume change of electrodes. We control the degree of crosslinking of GPEs by adding different amount of long-chain and short-chain cross-linkers to synergistically adjust their mechanical properties as well as conductivity of the GPEs. The optimized GPE exhibits an ionic conductivity of 0.63ms/cm and an break strain of 125%. The ability to suppress lithium dendrite is demonstrated by experimenting 100 cycles of galvanostatic test at 0.5 mA/cm2. Finally, we analyze the nanoscale structure of the GPEs by small angle X-ray scattering (SAXS). A network structure of star-like hard sphere with its radius in one nanometer range along with a hierarchical aggregation structure in the membrane are modelled. Furthermore, the conductivity of the GPE can be correlated with the structural parameters of the aggregate, e.g. its fractal dimension and the size of the cluster network. It is found that highly compact cluster network with fractal dimension of ~3, the conductivity of the GPEs is significantly reduced, indicating a designing guideline for future GPE used in lithium metal batteries. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/83152 |
DOI: | 10.6342/NTU202203923 |
全文授權: | 同意授權(限校園內公開) |
電子全文公開日期: | 2025-09-24 |
顯示於系所單位: | 化學工程學系 |
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