支化磺化聚酰亚胺膜的制备及其在全钒液流电池中的降解机理研究

Perfluorinated sulfonated membranes currently widely used in all vanadium redox flow batteries (VRFBs) have shortcomings such as high vanadium ion permeabilities and cost. Development of novel non-perfluorinated polymer membranes is an important method to overcome such problems. However, the long-term stabilities in VRFBs are big challenges for most non-perfluorinated polymer membranes, and there are few reports about their degradation mechanisms. Based on the reactions including substitution, nitration, ring-opening, etherification, etc., the monomers such as non-sulfonated diamines, non-sulfonated triamines, sulfonated diamines are designed and synthesized in this project. A series of non-perfluorinated branched sulfonated polyimides are also synthesized to prepare novel membranes for VRFB application. The as-prepared non-perfluorinated branched sulfonated polyimide membranes have low vanadium ion permeabilities (the vanadium ion permeability coefficients are around 1.0×10-7 cm2/min), excellent proton conductivities (the proton conductivities are higher than 0.05 S cm-1) and reasonable cost. Taking non-perfluorinated branched sulfonated polyimide membranes as representatives, their in-situ and ex-situ degradation mechanisms in VRFBs are systematically studied and revealed. Further, the obtained degradation mechanisms are related with the preparation processes of membranes. The research acheivements in this project will give effective strategies to improve the stabilities of novel non-perfluorinated polymer membranes. And important theoretical and technical supports will be also provided for the industrial application of novel non-perfluorinated polymer membranes in VRFBs and the further development of energy storage field.

全钒液流电池（VRFB）中广泛使用的全氟磺酸膜钒渗透高且价格昂贵，研发新型非全氟高分子膜是克服这些缺点的重要途径。然而，绝大多数非全氟高分子膜在VRFB中的长期稳定性均存在挑战，而其降解机理却鲜见报道。本课题基于取代、硝化、开环、醚化等反应原理，设计并合成非磺化二胺、非磺化三胺、磺化二胺单体；通过缩聚合成一系列非全氟支化磺化聚酰亚胺，以制备钒渗透低（VO2+渗透系数 ≈ 1.0×10-7cm2/min）、质子电导优良（质子电导率 > 0.05 S cm-1）、价格合理的新型VRFB隔膜。以所制备的非全氟支化磺化聚酰亚胺膜为代表，通过在线和离线两种方式，系统研究并揭示膜在VRFB中的降解机理，将其与膜的制备过程相关联。本研究的顺利开展，将为提高新型非全氟高分子膜的稳定性提供有效策略，从而为其在VRFB中的工业化应用和储能领域的进一步发展提供关键理论依据和技术支撑。

全钒液流电池（VRFB）中广泛使用的全氟磺酸膜如进口Nafion膜的钒渗透高且价格昂贵，研发新型非全氟高分子膜是克服这些缺点的重要途径。然而，绝大多数非全氟高分子膜在VRFB中的稳定性均存在挑战，而其降解机理却鲜见报道。基于此，本项目采用单体合成及分子结构调控策略，制备了支化、离子/共价交联等系列磺化聚酰亚胺隔膜，并优化其支化度、磺化度、交联度等关键参数，较深入阐明了其结构-制备-性能关系。所制备的支化磺化聚酰亚胺膜钒渗透低（VO2+渗透系数 ≈ 1.0×10-7cm2/min）、质子电导率与Nafion膜相当、价格仅为Nafion膜的六分之一~四分之一，为其商业化开发提供了可能。此外，该项目的单体及聚合物合成工艺也可为其他磺化芳香高分子的研发提供借鉴思路。通过在线和离线实验研究及理论计算相结合的方式，详细研究了支化磺化聚酰亚胺膜在VRFB中的降解行为，深入揭示了膜的形貌、结构、理化性能等随使用时间的演变行为，并提出了可能的降解机理，为非全氟芳香高分子膜在全钒液流电池中的稳定性研究提供了理论和实验参考。以自主合成的聚酰亚胺为基材，采用多孔化策略，创制出多孔化聚酰亚胺膜，有效地强化了聚酰亚胺骨架的化学稳定性和质子电导率。此外，利用理论计算深入地解释了其稳定性优异的内在原因，为后续开发出无功能传质基团的超高稳定性全钒液流电池隔膜奠定了基础。将增强剂（例如：甲基纤维素、氨基化多壁碳纳米管、全氟磺酸聚合物）进行修饰后或直接引入支化/线型磺化聚酰亚胺中，制备出系列支化/线型磺化聚酰亚胺基复合膜，有效提升了支化/线型磺化聚酰亚胺膜的质子电导率及化学稳定性。此外，深入研究了增强剂引入量对复合膜性能的影响，以及支化/线型磺化聚酰亚胺与增强剂之间的相互作用机制。本项目的顺利开展，可为VRFB提供新型非全氟高分子膜，为提高新型非全氟高分子膜的稳定性提供有效策略，从而为其在VRFB中的工业化应用和储能领域的进一步发展提供关键理论依据和技术支撑。在本项目资助下，项目团队共发表论文13篇，其中Chem. Eng. J. 期刊论文2篇、J. Mater. Chem. A 期刊论文1篇、 J. Membrane Sci.期刊论文3篇；获授权发明专利3项、申请发明专利1项。