高性能高稳定咪唑型阴离子交换膜连续离子传输通道构筑机理及性能研究

As the core component, anion exchange membrane (AEMs) has always been the focus and difficulty in the development of anion exchange membrane fuel cell (AEMFC). However, there are two severe challenges: the conflict between ionic exchange capacity (IEC) and mechanical properties and the conflict between ionic exchange capacity (IEC) and mechanical properties. Crosslinking structure can improve dimensional stability of AEMs, but the loss of conductivity is serious. This project aims to study the substitution of C4 and C5 imidazolium with good stability, and PBI/PVBC with excellent stability is used as the polymer framework. And by "anchoring" the crystalline materials containing small molecular conducting groups of imidazolium salts in AEMs, abundant and orderly ion transport channels are constructed in the membrane by using the inherent channel crystal rules to reduce the ion transport resistance. And then, the microstructure, electrochemical characterization and cell performance of composite AEMs are researched by spectroscopy, electrochemical technology and single cell test. Besides, through theoretical calculation, the construction and regulation mechanism of continuous ion transport channel in macromolecular crosslinked structure will studied. Based on this project, it provides experimental support and theoretical guidance on the design of high-performance AEMs, promoting the development and application of AEMFCs.

作为碱性膜燃料电池的核心部件，碱性膜（AEMs）的开发一直是该领域研究的重点与难点，但该类膜存在离子交换容量与机械性能间此消彼长的矛盾，及低离子电导率和差的化学稳定性等问题。交联结构可以提升膜尺寸稳定性，但电导率损失严重。本项目拟以稳定性较好的咪唑鎓盐为对象展开研究，以稳定性优异的聚苯并咪唑/聚乙烯基苄基氯为高分子骨架，通过在膜内“锚定”载有游离咪唑鎓盐小分子传导基团的晶体材料，利用固有孔道晶体规则在膜内构建丰富有序的离子传输通道，减少离子传输阻力，突破膜内共价结合的官能团数量限制，构建广泛高效氢键网络体系和离子传递通道，以提高膜的电导率及稳定性。然后，利用现代谱学显微技术、电化学方法及单电池测试手段，研究膜的微观结构、电化学特性及电池性能；并通过理论计算，研究大分子交联型AEMs中连续离子传输通道的构建与调控机制。本项目的完成将在分子水平上为高性能AEMs的开发提供实验依据和理论指导。

本基金项目通过合成C4、C5取代咪唑鎓盐，分别通过共价交联引入AEMs中，提高膜内官能团的数量；同时采用不含有醚键等不稳定端基的聚苯并咪唑/聚乙烯基苄基氯为分子骨架，通过共价交联，提升离子交换膜的稳定性、防止离子交换膜的过度溶胀，以达到提升强化膜离子传递特性、化学稳定性的目的，制备了厚度仅为15微米以下的超薄复合增强膜，结果显示，复合膜的电导率有所增加，20 ℃时达到了26.0 mS cm-1，并且80 ℃时，高达116.2 mS cm-1，组装单池，单池极化曲线测试，单池的峰值功率密度在0.542V处达到了379 mW cm-2。同时，为了提高膜中水的反扩散，以低密度聚乙烯为基膜制备了具有高离子交换容量的聚离子液体增强膜，制备得到具有高离子交换容量的超薄的聚离子液体增强膜。膜厚度17 µm微米，在60oC下电导率为32.9 mS/cm，断裂拉伸强度大于80 MPa。经过碱交换后，该膜的离子交换容量高达2.89 mmol/g，其中叔胺贡献了1.22 mmol/g，季胺贡献了1.67 mmol/g。合成的高离子交换容量聚离子液体膜的最大水扩散率为0.032 g/(min cm2)（50oC），扣除厚度因素后，相同温度下约为A201膜的1.8倍。采用该聚离子液体增强膜，氢氧为反应气、在1000 mA/cm2下功率密度可达到545 mW/cm2。