Asymmetric porous polybenzimidazole membrane with tunable morphology for vanadium flow battery (VFB)

• Published in: Journal of membrane science 2025-01, Vol.713, p.123281, Article 123281
• Main Authors: Yang, Erqiang, Wang, Yixin, Guo, Tiegen, Chao, Ge, Zhou, Xiaowei, Zhang, Yuchen, Hu, Bin, Lv, Zixin, Qian, Huidong, Geng, Kang, Li, Nanwen
• Format: Article
• Language: English
• Subjects: Adjustable and disconnected porous membrane; Phthalates; Polybenzimidazole; Ultrathin-dense layers; Vanadium flow battery
• ISSN: 0376-7388
• DOI: 10.1016/j.memsci.2024.123281

Polybenzimidazole (PBI) membranes have attracted much attention for flow batteries due to their good chemical stability. However, the high area resistance (AR) of dense PBI limits its further development in VFBs. Herein, we design a sintering method to remove the phthalates with different molecular structures in the ternary system (PBI as polymer, N-methylpyrrolidone as solvent, and phthalates as non-solvent). Asymmetric PBI membranes with adjustable and disconnected pores, as well as ultrathin-dense layers, are prepared. This series of porous membranes shows excellent overall performance in VFBs. Among them, the porous NPBI-DBP-200 membrane (0.139 Ω cm2) with DBP as the non-solvent exhibits a lower AR compared to the dense NPBI (0.489 Ω cm2). At a current density of 200 mA cm−2, the energy efficiency (EE) of a single cell assembled with the NPBI-DBP-200 membrane (EE = 78.26 %) has improved by 26.37 % compared to the dense NPBI membrane (EE = 61.93 %). In addition, the porous NPBI-DBP-200 membrane has excellent in-situ stability, and the single cell can operate stably for 1800 cycles at the current density of 120 mA cm−2. This work presents a novel, easy-to-use technique for preparing high-performance porous PBI membranes with adjustable pore morphology. [Display omitted] •The morphology of the porous membrane was tuned by different phthalates.•The phthalates were removed by sintering avoiding the use of organic solvent.•Asymmetric porous PBI membrane has disconnected pores and an ultrathin-dense layer.•EE of the single cell assembled with NPBI-DBP-200 showed a 26.37 % improvement.