Blending polybenzimidazole with an anion exchange polymer increases the efficiency of Vanadium Redox Flow Batteries

Title
Blending polybenzimidazole with an anion exchange polymer increases the efficiency of Vanadium Redox Flow Batteries
Authors
헨켄스마이어디억이규성아나스타시아Mina JungWonmi LeeChanho NohSangwon KimYongchai Kwon
Keywords
VRFB; Polybenzimidazole; FAA3; Blend membranes
Issue Date
2019-06
Publisher
Journal of membrane science
Citation
VOL 580-116
Abstract
PBI membranes are recently discussed as stable, well performing membranes for vanadium redox flow batteries (VRFB). Blending meta-PBI with an anion exchange polymer (FAA3i) slightly reduces the coulomb efficiency from 99.7 to 97.8%, but strongly increases the voltage efficiency from 82.5 to 88.2%, leading to an increased energy efficiency (86.2% at 80  mA  cm− 2), exceeding that of meta-PBI (82.2%) and N212 (83%). Apparently, since the conductivity of sulfuric acid has a maximum around a concentration of 3.8  M, the concentration of the absorbed acid has a dominant influence on the conductivity. Addition of FAA3i decreases the concentration of the acid absorbed by PBI membranes. Furthermore, an ex-situ stability test in 1.5  M V5+ solutions in 2  M sulfuric acid for 87 days showed a very high stability for meta-PBI and Nafion 212, while the commercial FAA3 membrane disintegrated into pieces. Blending of meta-PBI and FAA3 decreased the stability, as proven by formation of V4+, but all tested blend membranes retained their membrane shape and could still be handled. Blending with FAA3 reduces the tensile strength and Young's modulus of meta-PBI, and doping with sulfuric acid leads to a further decrease in the mechanical strength. However, an acid doped PF-21 still showed a tensile strength of 37  MPa and a Young's modulus of 0.7  GPa.
URI
http://pubs.kist.re.kr/handle/201004/69139
ISSN
0376-7388
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KIST Publication > Article
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