Lee, Wonmi Jung, Mina Serhiichuk, Dmytro Noh, Chanho Gupta, Gaurav Harms, Corinna Kwon, Yongchai Henkensmeier, Dirk 2024-01-19T18:34:04Z 2024-01-19T18:34:04Z 2021-09-04 2019-12 0376-7388 https://pubs.kist.re.kr/handle/201004/119290 A commercial porous polyvinylidene fluoride membrane (pore size 0.65 mu m, nominally 125 mu m thick) is spray coated with 1.2-4 mu m thick layers of polybenzimidazole. The area resistance of the porous support is 36.4 m Omega cm(2) in 2 M sulfuric acid, in comparison to 540 m Omega cm(2) for a 27 mu m thick acid doped polybenzimidazole membrane, and 124 m Omega cm(2) for PVDF-P20 (4 mu m thick blocking layer). Addition of vanadium ions to the supporting electrolyte increases the resistance, but less than for Nafion. The expected reason is a change in the osmotic pressure when the ionic strength of the electrolyte is increased, reducing the water contents in the membrane. The orientation of the composite membranes has a strong impact. Lower permeability values are found when the blocking layer is oriented towards the vanadium-lean side in ex-situ measurements. Cells with the blocking layer on the positive side have significantly lower capacity fade, also much lower than cells using Nafion 212. The coulombic efficiency of cells with PVDF-PBI membranes (98.4%) is higher than that of cells using Nafion 212 (93.6%), whereas the voltage efficiency is just slightly lower, resulting in energy efficiencies of 85.1 and 83.3%, respectively, at 80 mA/cm(2). English ELSEVIER Layered composite membranes based on porous PVDF coated with a thin, dense PBI layer for vanadium redox flow batteries Article 10.1016/j.memsci.2019.117333 1 JOURNAL OF MEMBRANE SCIENCE, v.591 JOURNAL OF MEMBRANE SCIENCE 591 N scie scopus 000482553600027 2-s2.0-85073254817 Engineering, Chemical Polymer Science Engineering Polymer Science Article ANION-EXCHANGE MEMBRANES POLYBENZIMIDAZOLE MEMBRANES PERFORMANCE EFFICIENCY STABILITY ACID Porous PVDF Polybenzimidazole blocking layer Composite membranes Vanadium redox flow batteries