Imidazole based ionenes, their blends with PBI-OO and applicability as membrane in a vanadium Redox flow battery

Title
Imidazole based ionenes, their blends with PBI-OO and applicability as membrane in a vanadium Redox flow battery
Authors
남석우김형준장종현헨켄스마이어디억정미나김상원Izabela Struzynska-PironArtjom MaljuschOliver ConradiYongchai Kwon
Keywords
Vanadium Redox Flow Battery (VRFB); anion exchange membrane (AEM); PBI-OO; Ionenes; 2-Mesityl-benzimidazole
Issue Date
2017-11
Publisher
European polymer journal
Citation
VOL 96-392
Abstract
A new cationic ionene was synthesised from dibromoxylene and 2-(2,4,6-trimethylphenyl)benzimidazole. Even though the weight average molecular weight Mw reached values around 40,000 g/mole, no membranes could be prepared from this ionene, probably because of its rigid backbone. Blending with 33, 41 and 50 wt% PBI-OO gave access to self-supporting membranes. In comparison with pure PBI-OO, these membranes have a higher water uptake (30– 50%) and show a chloride conductivity around 0.5 mS/cm at 60 °C. In the VRFB, the membranes absorb sulfuric acid, which increases the conductivity. Nevertheless, the voltage efficiency (VE) of PBI-OO was surprisingly low. Further analysis suggests that the polymer gets easily sulfonated, leading to ionic crosslinking and thus reduced conductivity. At OCV, the PBI-OO based membrane showed a very low potential degradation rate of 0.19 mV/h even over 280 h, while the OCV decreased 60% within 60 h for Nafion 212. Charge/discharge curves revealed that the coulomb efficiency (CE) decreases with increasing amount of the ionene, while the VE increases. This indicates a potential for improved membranes by blending PBI or its derivatives (responsible for high CE) with highly conducting ion exchange materials to increase the VE in comparison to the pure polymer.
URI
http://pubs.kist.re.kr/handle/201004/66257
ISSN
0014-3057
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