Boosting Charge Storage in Ferri/Ferrocyanide‐Based Alkaline Redox Flow Batteries
- 1School of Mechanical Engineering Purdue University Indianapolis Indiana USA
- 2Department of Materials Science and Chemical Engineering Stony Brook University Stony Brook New York USA
- 3Physical and Computational Sciences Directorate Pacific Northwest National Laboratory Richland Washington USA
Abstract
The ferri/ferrocyanide redox couple has long served as a benchmark catholyte in aqueous redox flow batteries (RBFs), particularly under highly alkaline conditions. However, the limited alkaline solubilities of commercially available Na+ and K+ forms constrain the attainable energy density of these systems. Here, we demonstrate that Li+ substitution substantially boosts the alkaline solubility of ferri/ferrocyanide, offering a promising route to overcome the long‐standing energy density limitation. Complementary spectroscopic and computational analyses reveal a distinct solubilization mechanism in which Li+ promotes mixed‐solvation and aggregate‐rich solution structures that sustain highly concentrated, fully dissolved electrolytes beyond the saturation behavior of Na+ and K+ analogs. When Li3/4Fe(CN)6 is paired with polysulfide or organic anolytes, the resulting flow cells demonstrate exceptional cycling stability and energy density in alkaline environments. Using symmetric flow cell configurations, we further elucidate the stability and decomposition mechanisms of the corresponding redox materials, revealing contrasting effects of electrolyte alkalinity: it compromises ferri/ferrocyanide stability while substantially enhancing polysulfide stability. These findings establish complementary molecular insights into redox materials solubilization and stabilization, providing a mechanistic foundation for developing energy‐dense and durable alkaline RBFs.
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BibTeX
@article{khabbaz2026boosting,
title = {{Boosting Charge Storage in Ferri/Ferrocyanide‐Based Alkaline Redox Flow Batteries}},
author = {Mahla Sarfaraz Khabbaz and Kuldeepsinh Raj and Lucas Zhang and Sepideh Biabanialitappeh and J. David Bazak and Nav Nidhi Rajput and Xiaoliang Wei},
journal = {Angewandte Chemie (International Ed. in English)},
year = {2026},
month = sep,
doi = {10.1002/anie.3588313},
url = {https://doi.org/10.1002/anie.3588313},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Boosting Charge Storage in Ferri/Ferrocyanide‐Based Alkaline Redox Flow Batteries
AU - Mahla Sarfaraz Khabbaz
AU - Kuldeepsinh Raj
AU - Lucas Zhang
AU - Sepideh Biabanialitappeh
AU - J. David Bazak
AU - Nav Nidhi Rajput
AU - Xiaoliang Wei
PY - 2026
DA - 2026/09/22
JO - Angewandte Chemie (International Ed. in English)
DO - 10.1002/anie.3588313
UR - https://doi.org/10.1002/anie.3588313
AB - The ferri/ferrocyanide redox couple has long served as a benchmark catholyte in aqueous redox flow batteries (RBFs), particularly under highly alkaline conditions. However, the limited alkaline solubilities of commercially available Na+ and K+ forms constrain the attainable energy density of these systems. Here, we demonstrate that Li+ substitution substantially boosts the alkaline solubility of ferri/ferrocyanide, offering a promising route to overcome the long‐standing energy density limitation. Complementary spectroscopic and computational analyses reveal a distinct solubilization mechanism in which Li+ promotes mixed‐solvation and aggregate‐rich solution structures that sustain highly concentrated, fully dissolved electrolytes beyond the saturation behavior of Na+ and K+ analogs. When Li3/4Fe(CN)6 is paired with polysulfide or organic anolytes, the resulting flow cells demonstrate exceptional cycling stability and energy density in alkaline environments. Using symmetric flow cell configurations, we further elucidate the stability and decomposition mechanisms of the corresponding redox materials, revealing contrasting effects of electrolyte alkalinity: it compromises ferri/ferrocyanide stability while substantially enhancing polysulfide stability. These findings establish complementary molecular insights into redox materials solubilization and stabilization, providing a mechanistic foundation for developing energy‐dense and durable alkaline RBFs.
SN - 1433-7851
SN - 1521-3773
ER -