Dual-Ligand Engineering of a Stable and High-Utilization Iron Complex Anolyte for Alkaline All-Iron Flow Batteries
Year: 2026
Type: preprint
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.
Source: ChemRxiv
Institutions: National University of Singapore, Suzhou Research Institute
Language: English
Topic: Aqueous and Flow Batteries
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7220672733