Bui, Trung Tuyen Park, Sungmin Shin, Mingyu Ikhsan, Muhammad Mara Kwon, Yongchai Henkensmeier, Dirk 2025-05-07T07:00:28Z 2025-05-07T07:00:28Z 2025-05-07 2025-08 1614-6832 https://pubs.kist.re.kr/handle/201004/152375 Poly(4,4′-diphenylether-5,5′-bibenzimidazole), OPBI, is sulfonated at different conditions to reach different degrees of sulfonation (DOS of 35, 54, 102, and 133%). The membrane with a DOS of 102% shows the most balanced properties. The tensile strength is 55 MPa and the elongation at break is 130%. Conductivity in 3 m sulfuric acid exceeds that of Nafion 212 (58 mS cm−1) and reaches 70 mS cm−1. The resistance of a 23 µm thick membrane is 33 mΩ cm2, and energy efficiencies of 91.8% at 80 mA cm−2 and 90.4% at 100 mA cm−2 are achieved. OPBI showed the highest stability in contact with VO2+, because the ions cannot enter the membrane. Sulfonated OPBI swells more in sulfuric acid, and therefore has a lower stability. However, it is found that the stability increases with the DOS. This indicates that attack by VO2+ occurs preferentially at positions that are activated for electrophilic aromatic substitution reactions. English Wiley-VCH Verlag Sulfonated Polybenzimidazole Membranes: How Sulfonation Affects Properties, Stability, and Performance in Vanadium Redox Flow Batteries Article 10.1002/aenm.202500440 1 Advanced Energy Materials, v.15, no.30 Advanced Energy Materials 15 30 N scie scopus 001478806400001 Chemistry, Physical Energy & Fuels Materials Science, Multidisciplinary Physics, Applied Physics, Condensed Matter Chemistry Energy & Fuels Materials Science Physics Article chemical stability energy efficiency OPBI sulfonated polybenzimidazoles VRFB