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Language: English

Conflict of Interest: In relation to this article, we declare that there is no conflict of interest.

Publication history: Received March 18, 2026
Revised March 18, 2026
Accepted April 5, 2026
Available online August 25, 2026

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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All-Iron Redox Flow Batteries Using a DABCO-PPO Anion Exchange Membrane

Taejoon Byun Jae Bin Park¹ Kyunghan Lee^{2 4} Seongbin Kang³ Seungwon Kang^{4 5} Ah Reum Choi¹ Jin Hong Lee¹ Myungeun Seo^2† Jinhee Lee^5† Minjoon Park^3†

Reliability Assessment Center for Chemical Materials, Korea Research Institute of Chemical Technology (KRICT) ¹School of Chemical Engineering, Pusan National University ²Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST) ³Department of Nano Fusion Technology, Advanced Energy Major, School of Transdisciplinary Engineering, Research Center of Energy Convergence Technology, Pusan National University ⁴Department of Research and Development ⁵Department of Applied Chemical Engineering, University of Science and Technology (UST)

seomyungeun@kaist.ac.kr, jinhee@krict.re.kr, mjpark@pusan.ac.kr

Korean Journal of Chemical Engineering, August 2026, 43(10), 2683-2692(10)
https://doi.org/10.1007/s11814-026-00719-x

Abstract

All-iron redox flow batteries (AIRFBs) have attracted increasing attention as cost-effective and sustainable large-scale

energy storage systems due to the natural abundance and low cost of iron. However, their performance is often hindered

by the crossover of iron species through the membrane, leading to electrolyte contamination, capacity decay, and reduced

coulombic efficiency. In this study, we report a reinforced anion exchange membrane based on poly(phenylene oxide)

(PPO) functionalized with 1,4-diazabicyclo[2.2.2]octane (DABCO) for AIRFBs. The membrane was modified through

vinylbenzyl functionalization followed by thermal crosslinking and integrated with a porous polyethylene support to fabricate

a reinforced composite membrane (DAB-PPO-RX). Structural characterization confirmed functionalization, crosslinking,

and integration with the support layer while maintaining mechanical robustness and stability. When applied in

AIRFBs, DAB-PPO-RX exhibited improved electrochemical performance compared with the non-reinforced membrane

and commercial Selemion DSV membrane. The cells using DAB-PPO-RX delivered a coulombic efficiency of 93.7% and

an energy efficiency of 64.9% with stable cycling over repeated charge–discharge cycles. The improved performance is

attributed to the reinforced membrane structure, which suppresses iron crossover while maintaining efficient ion transport.

These results demonstrate that DAB-PPO-RX provides an effective strategy for improving membrane selectivity and stability

in AIRFBs, highlighting its potential for large-scale energy storage.

Keywords

All-iron redox flow batteries · Anion exchange membrane · Reinforced composite membrane · Iron crossover suppression · Thermal crosslinking