The sulfuric acid (SA) doped dense polybenzimidazole (PBI) membrane exhibits low vanadium crossover, and is of great interest as the separator in vanadium redox flow battery (VRFB) applications. However, further reducing the area resistance is needed to increase the voltage efficiency. Towards this target, a series of quaternary ammonium groups grafted PBI membranes are designed and synthesized by using 2,3-epoxypropyltrimethylammonium chloride (EPTMA-Cl) as the grafting agent. The membranes were prepared through a gentle and facile heating curing method without the usage of catalyst, and physicochemical properties and single cell performance of SA doped PBI-EPTMA membranes are systematically investigated. The results indicate that grafted EPTMA groups increase the hydrophilicity and free volume of membranes, resulting in enhanced SA doping content and decreased area resistance. Ultimately, VRFB assembled with the PBI-21%EPTMA membrane displays higher energy efficiencies (87.6%–75.3%) at current densities of 50–150 mA cm⁻², comparing with Nafion115 (81.7–61.2%). The stable performance over 450 charge-discharge cycles of VRFB demonstrates the good stability of the PBI-EPTMA membrane.

掺杂有硫酸（SA）的致密聚苯并咪唑（PBI）膜显示出较低的钒交叉，并作为钒氧化还原液流电池（VRFB）应用中的隔膜而引起了广泛的关注。但是，需要进一步减小面积电阻以提高电压效率。为此，以2,3-环氧丙基三甲基氯化铵（EPTMA-Cl）为接枝剂，设计合成了一系列季铵基接枝的PBI膜。该膜是通过温和而简便的加热固化方法制备的，无需使用催化剂，并且系统地研究了掺SA的PBI-EPTMA膜的理化性质和单电池性能。结果表明，接枝的EPTMA基团增加了膜的亲水性和自由体积，导致增加的SA掺杂含量和降低的区域电阻。最终，VRFB与PBI-21％EPTMA膜组装后，在电流密度为50-150 mA cm时显示出更高的能量效率（87.6％–75.3％）⁻²，与Nafion115（81.7–61.2％）比较。VRFB在450个充放电循环中的稳定性能证明了PBI-EPTMA膜的良好稳定性。