Membrane-Induced Vanadium Crossover-Blocking Polybenzimidazole Copolymer with Exceptional Proton Selectivity

Saheed Bukola, Ashlee Vise, Yuanshun Li, Gabriel Goenaga, Thomas Zawodzinski, Jeffrey Blackburn, Bryan Pivovar

Research output: Contribution to journalArticlepeer-review

6 Scopus Citations


Broad deployment of redox flow batteries is hindered, in part, due to the lack of highly selective ion-exchange membranes with high proton conductivity. We report a post-functionalization strategy for polybenzimidazole copolymer (PBI-co) membranes by a reacting mixture of concentrated sulfuric and phosphoric acids that led to improved membrane selectivity while retaining high proton conductivity. Fourier-transform infrared spectroscopy confirmed successful sulfonation and protonation of benzimidazole functionalities. PBI-co exhibits a very high room-temperature proton conductivity of 0.138 S cm–1, as measured by electrochemical impedance spectroscopy. PBI-co also demonstrates electromigration crossover mitigation under applied current densities up to 500 mA cm–2, and voltage pulses up to 1.4 V, while also inhibiting diffusion-driven vanadium crossover for over 20 days. Single-cell vanadium flow battery testing on post-functionalized PBI-co further confirms state-of-the-art battery performance with an ∼99.5% Coulombic efficiency at 100 mA cm–2 and an area-specific resistance of ∼20 mΩ cm2 lower than Nafion-212 membrane.

Original languageAmerican English
Pages (from-to)381-393
Number of pages13
JournalACS Applied Polymer Materials
Issue number1
StatePublished - 14 Jan 2022

Bibliographical note

Publisher Copyright:
© 2021 American Chemical Society

NREL Publication Number

  • NREL/JA-5900-80770


  • batteries
  • membrane
  • polybenzimidazole copolymer
  • proton transport
  • vanadium crossover


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