Chen Yu, Li Yanyan, Xu Jiaqi, Chen Shaoyun, Chen Dongyang
College of Materials Science and Engineering, Fuzhou University, Fuzhou 350116, China.
College of Chemical Engineering and Materials Science, Quanzhou Normal University, Quanzhou 362000, China.
ACS Appl Mater Interfaces. 2021 Apr 28;13(16):18923-18933. doi: 10.1021/acsami.1c04250. Epub 2021 Apr 14.
Cationic group distribution and elemental composition are two key factors determining the conductivity and stability of anion exchange membranes (AEMs) for vanadium redox flow batteries (VRFBs). Herein, fluorinated tetra-dimethylaminomethyl-poly(fluorenyl ether)s (TAPFE)s were designed as the polymer precursors, which were reacted with 6-bromo-,,-trimethylhexan-1-aminium bromide to introduce di-quaternary ammonium (DQA) containing side chains. The resultant DQA-TAPFEs with a rigid fluorinated backbone and flexible multi-cationic side chains exhibited distinct micro-phase separation as probed by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). DQA-TAPFE-20 with an ion exchange capacity (IEC) of 1.55 mmol g exhibited a SO conductivity of 10.1 mS cm at room temperature, much higher than that of a control AEM with an identical backbone but spaced out cationic groups, which had a similar IEC of 1.60 mmol g but a SO conductivity of only 3.2 mS cm. Due to the Donnan repulsion effect, the DQA-TAPFEs exhibited significantly lower VO permeability than Nafion 212. The VRFB assembled with DQA-TAPFE-20 achieved an energy efficiency of 80.4% at 80 mA cm and a capacity retention rate of 82.9% after the 50th cycling test, both higher than those of the VRFB assembled with Nafion 212 and other AEMs in the literature. Therefore, the rationally designed DQA-TAPFEs are promising candidates for VRFB applications.
阳离子基团分布和元素组成是决定钒氧化还原液流电池（VRFB）阴离子交换膜（AEM）导电性和稳定性的两个关键因素。在此，设计了氟化四二甲基氨基甲基聚（芴基醚）（TAPFE）作为聚合物前体，使其与6-溴-，，-三甲基己-1-铵溴化物反应，引入含二季铵（DQA）的侧链。通过小角X射线散射（SAXS）和原子力显微镜（AFM）探测，所得具有刚性氟化主链和柔性多阳离子侧链的DQA-TAPFE表现出明显的微相分离。离子交换容量（IEC）为1.55 mmol g的DQA-TAPFE-20在室温下的SO电导率为10.1 mS cm，远高于具有相同主链但阳离子基团间隔开的对照AEM，后者的IEC相似，为1.60 mmol g，但SO电导率仅为3.2 mS cm。由于唐南排斥效应，DQA-TAPFE的VO渗透率明显低于Nafion 212。用DQA-TAPFE-20组装的VRFB在80 mA cm下的能量效率为80.4%，在第50次循环测试后的容量保持率为82.9%，均高于用Nafion 212组装的VRFB和文献中的其他AEM。因此，合理设计的DQA-TAPFE是VRFB应用的有前途的候选材料。
