Dual-Ligand Engineering of a Stable and High-Utilization Iron Complex Anolyte for Alkaline All-Iron Flow Batteries
- 1Department of Materials Science and Engineering, College of Design and Engineering
- 2National University of Singapore
- 3National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou, Jiangsu, China, 215123
Abstract
Alkaline all-iron flow batteries offer a low-cost and inherently safe approach to large-scale energy storage, but Fe-complex anolytes remain limited by insufficient coordination stability, solubility, and utilization at high concentrations. Here, we develop a dual-ligand Fe(TEA)(PS) anolyte using triethanolamine as the primary ligand and pyridine-3-sulfonate (PS) as the secondary ligand. The secondary ligand reinforces the Fe coordination environment through pyridyl-N coordination while introducing a hydrophilic sulfonate group. Computational calculations and Fe K-edge X-ray absorption spectroscopy reveal an enlarged molecular configuration and a more saturated coordination environment. Fe(TEA)(PS) exhibits a reversible Fe(III)/Fe(II) redox couple at -0.87 V versus SHE and a solubility of 1.41 M in 2 M NaOH. The resulting full cell achieves 95.12% electrolyte utilization at 1.0 M and a peak power density of 422.8 mW cm -2 . It retains 98.28% of its capacity over 1200 cycles at 100 mA cm -2 . Moreover, a cell containing 0.8 M Fe(TEA)(PS) maintains 96.87% capacity after 1800 cycles, corresponding to a decay rate of only 0.0017% per cycle. These results establish second-ligand engineering as an effective strategy for developing stable, highly soluble, and highly utilized Fe-complex anolytes for alkaline all-iron flow batteries.
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BibTeX
@misc{wang2026dualligand,
title = {{Dual-Ligand Engineering of a Stable and High-Utilization Iron Complex Anolyte for Alkaline All-Iron Flow Batteries}},
author = {Heng Wang and Zhiyu Wang and Tianyu Yang and Hongtao Xie and Yingjia Hu and Qing Wang},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15009967/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009967/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Dual-Ligand Engineering of a Stable and High-Utilization Iron Complex Anolyte for Alkaline All-Iron Flow Batteries
AU - Heng Wang
AU - Zhiyu Wang
AU - Tianyu Yang
AU - Hongtao Xie
AU - Yingjia Hu
AU - Qing Wang
PY - 2026
DA - 2026/10/06
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009967/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009967/v1
AB - Alkaline all-iron flow batteries offer a low-cost and inherently safe approach to large-scale energy storage, but Fe-complex anolytes remain limited by insufficient coordination stability, solubility, and utilization at high concentrations. Here, we develop a dual-ligand Fe(TEA)(PS) anolyte using triethanolamine as the primary ligand and pyridine-3-sulfonate (PS) as the secondary ligand. The secondary ligand reinforces the Fe coordination environment through pyridyl-N coordination while introducing a hydrophilic sulfonate group. Computational calculations and Fe K-edge X-ray absorption spectroscopy reveal an enlarged molecular configuration and a more saturated coordination environment. Fe(TEA)(PS) exhibits a reversible Fe(III)/Fe(II) redox couple at -0.87 V versus SHE and a solubility of 1.41 M in 2 M NaOH. The resulting full cell achieves 95.12% electrolyte utilization at 1.0 M and a peak power density of 422.8 mW cm -2 . It retains 98.28% of its capacity over 1200 cycles at 100 mA cm -2 . Moreover, a cell containing 0.8 M Fe(TEA)(PS) maintains 96.87% capacity after 1800 cycles, corresponding to a decay rate of only 0.0017% per cycle. These results establish second-ligand engineering as an effective strategy for developing stable, highly soluble, and highly utilized Fe-complex anolytes for alkaline all-iron flow batteries.
ER -