Redox-Targeting Synergy With Dual Mediators for Prussian Blue Analogue Flow Batteries.
basic_science · Level V
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- Record sourced from PubMed, PMID 42467178.
- Also identified by DOI 10.1002/adma.74155.
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Abstract
Aqueous redox-targeting flow batteries (RTFBs) are highly promising electrochemical energy storage systems due to their high energy density, long cycle life, and high safety. Dual-molecule redox-targeting (DMRT) system simplifies the matching between redox mediators (RMs) and solid materials. However, the interaction between RMs and solid material is not well clarified in reported works. Here, a 4-OH-TEMPO/[Fe(CN)<sub>6</sub>]<sup>3-/4-</sup>-NiHCF||Zn DMRT flow battery is developed in this work, delivering an outstanding energy density of 75.04 Wh L<sup>-1</sup> (9.09 times higher than that of blank flow battery), excellent coulombic efficiency (99.9%), solid material utilization (82.9%), and capacity retention (99.7% per cycle) at 10 mA cm<sup>-2</sup>. Importantly, a redox-targeting synergy mechanism of two RMs is elucidated through various experimental and theoretical validations, wherein [Fe(CN)<sub>6</sub>]<sup>3-/4-</sup> facilitates Fe-Fe electronic delocalization and Na<sup>+</sup> extraction, while 4-OH-TEMPO accelerates Fe-N interfacial charge exchange. The dual-mediator design exhibits distinct SOC-dependent contributions, quantitatively revealed by time-resolved operando ultraviolet-visible (UV-Vis) spectroscopy. Meanwhile, frequency-resolved operando distribution of relaxation times-electrochemical impedance spectroscopy (DRT-EIS) clarifies that direct NiHCF-mediator interfacial coupling governs the redox-targeting resistance. This work deepens the mechanistic understanding of redox-targeting chemistry in DMRT systems, advancing high-energy-density aqueous flow batteries.