Revisiting the attenuation mechanism of alkaline all-iron ion redox flow batteries

Yang, Wendong; Liu, Pei; Wang, Linfeng; Meng, Jintao; Jiang, Hua; Gui, Shuangyan; Guo, Jinhua; Wang, Jun; Zhou, Jun; Duan, Jiangjiang

doi:10.1016/j.cej.2024.150491

Cited by 5 publications

(10 citation statements)

References 46 publications

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“…Therefore, this result reconfirms the excellent stability of Fe(EDTS). Additionally, according to our previous research, this slight capacity fade (0.13%/day) can be attributed to the trace amounts of ligand crossover . Notably, this decay is fully recoverable by a simple rebalance method.…”

supporting

confidence: 63%

“…Furthermore, some TEA derivatives, such as 3-[bis(2-hydroxyethyl) amino]-2-hydroxypropanesulfonic acid (DIPSO), triisopropanolamine (TIPA), and bis(2-hydroxyethyl)amino-tris(hydroxymethyl)methane (BIS-TRIS), have also been designed as negative iron ligands to improve the performance of alkaline all-iron ion RFBs. − However, the unsaturated coordination (penta-coordination) makes Fe(TEA) and Fe(TEA-derivatives) easily dissociated, and the dissociative ferrous ions are substantially reduced to metallic iron, which results in HER issue and irreversible capacity decay (Figure a) . Additionally, according to our previous research and other reports, the ligands crossover issue presents another critical challenge in alkaline all-iron ion RFBs (Figure b). , It has been observed that Fe(CN) 6 3– exhibits strong oxidizing capability in the alkaline medium and can rapidly oxidize the free ligands (TEA or TEA-derivatives) migrated from the negative electrolyte. Moreover, the chemical reaction between Fe(CN) 6 3– and free ligands is intermediated by the hydroxyl radical ( • OH) .…”

mentioning

confidence: 99%

“…As illustrated in the Figure S16, providing a significant excess of ligands can increase the equilibrium constant to mitigate the decomposition issue of the iron-ligand complexes . However, the excess ligand would accelerate the ligands crossover issue and the side reaction in the positive electrolyte …”

mentioning

confidence: 99%

“…The crossover of active species (metallic ion) used to be a challenge in all-iron RFB systems. − To overcome the easy crossover issue of single ions, metal-ligand complexes instead of metal ions are suggested as active materials . Some studies have indicated that the crossover of large-volume metal-ligand complexes is negligible, which uses the Donnan effect and the size exclusion effect. , However, our previous research has revealed that the crossover of free ligands from the negative electrolyte poses another challenging problem . A rapid side reaction occurs between the migrating free ligands and the positively active species (Fe(CN) 6 3– ), resulting in continuous capacity decay.…”

mentioning

confidence: 99%

“…In comparison, the permeabilities of large-volume BIS-TRIS and negatively charged DIPSO – are reduced by 4.89- and 9.13-times, respectively. However, such crossover rate of ligands still limits the long-term cycling performance of alkaline all-iron ion RFBs. , …”

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confidence: 99%

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Sulfonated-Ligand Engineering Enables a Stable Alkaline All-Iron Ion Redox Flow Battery

Yang,

Jiang,

Wang

et al. 2024

ACS Energy Lett.

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Alkaline all-iron ion redox flow batteries (RFBs) are considered promising devices for large-scale energy storage due to their remarkable resistance to dendrite formation and the hydrogen evolution reaction. However, the decomposition of negative complexes and ligand crossover issues have limited their stable operation. Herein, we have developed a tetrasulfonated ethylenediamine derivative ligand (EDTS) to chelate with iron ions to serve as the negative active species (Fe(EDTS)). Benefiting from its stable hexa-coordinated structure, the Fe(EDTS) chelate exhibits unprecedented stability during long-term cycling. Additionally, the EDTS ligand with high charge density and large volume effectively mitigates crossover through size exclusion and Donnan effects. Paired with the Fe(CN) 6 electrolyte, the Fe(CN) 6 /Fe(EDTS) RFB demonstrates a formal cell voltage of 1.25 V, a high energy density of 25.04 Ah L −1 , and an unprecedented durability among reported capacity-symmetric all-iron RFBs, achieving a Coulombic efficiency of 99.93% and capacity retention of 96.08% after 3000 cycles.

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confidence: 63%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Sulfonated-Ligand Engineering Enables a Stable Alkaline All-Iron Ion Redox Flow Battery

Yang,

Jiang,

Wang

et al. 2024

ACS Energy Lett.

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Highly Stable Alkaline All‐Iron Redox Flow Batteries Enabled by Disulfonated Ligands Chelation

Jiang,

Yang,

Liu

et al. 2024

Advanced Energy Materials

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Alkaline all‐iron flow batteries possess intrinsic safety and low cost, demonstrating great potential for large‐scale and long‐duration energy storage. However, their commercial application is hindered by the issue of capacity decay resulting from the decomposition of iron complexes and ligand crossovers. In this paper, an robust anolyte Fe(TEA‐2S) is reported, which is formed by chelating iron ions with the sulfonate‐enriched ligand (TEA‐2S) in alkaline environment. By skillfully designing the ligands, the binding energy of the iron complexes increases and ligand crossovers are suppressed, making the iron complexes highly stable in the charge–discharge cycles. Alkaline all‐iron flow batteries coupling with Fe(TEA‐2S) and the typical iron‐cyanide catholyte perform a minimal capacity decay rate (0.17% per day and 0.0014% per cycle), maintaining an average coulombic efficiency of close to 99.93% over 2000 cycles along with a high energy efficiency of 83.5% at a current density of 80 mA cm−2. In addition, Fe(TEA‐2S) exhibits high solubility of up to 1.85 м (with a theoretical capacity of up to 49.58 Ah L−1), even at low temperatures as extreme as −30 °C. This work demonstrates a promising pathway toward achieving long‐duration and large‐scale energy storage.

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Progress in Profitable Fe‐Based Flow Batteries for Broad‐Scale Energy Storage

Huan,

Sun,

2024

WIREs Energy & Environment

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The development of an affordable, environmentally acceptable alternative energy storage devices are required to address the present energy problem and offer a viable solution for renewable energy sources with intermittency. As a broad‐scale energy storage technology, redox flow battery (RFB) has broad application prospects. However, commercializing mainstream all‐vanadium RFBs is slow due to the high cost. Owing to the environmental friendliness and affordable iron‐based raw materials the interest on iron‐based RFBs are increasing. The aim of the perspective is to offer a quick overview on research progress of iron‐based RFBs, including their research status, history, and development of essential components. Influencing factors such as conductivity, solubility, hydrogen evolution, reaction kinetics, etc. are summarized comprehensively. Further research was identified on reducing the hydrogen evolution on the electrodes, exploring economical and easy‐to‐recycle solutions for active materials, improving the stability of electrodes, and developing new electrode structures.

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Revisiting the attenuation mechanism of alkaline all-iron ion redox flow batteries

Cited by 5 publications

References 46 publications

Sulfonated-Ligand Engineering Enables a Stable Alkaline All-Iron Ion Redox Flow Battery

Sulfonated-Ligand Engineering Enables a Stable Alkaline All-Iron Ion Redox Flow Battery

Highly Stable Alkaline All‐Iron Redox Flow Batteries Enabled by Disulfonated Ligands Chelation

Progress in Profitable Fe‐Based Flow Batteries for Broad‐Scale Energy Storage

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