Symmetry-breaking design of an organic iron complex catholyte for a long cyclability aqueous organic redox flow battery

Li, Xiang; Gao, Peiyuan; Lai, Yun Yu; Bazak, J. David; Hollas, Aaron; Lin, Heng Yi; Vijayakumar, M.; Zhang, Shuyuan; Cheng, Chung Fu; Tung, Wei Yao; Lai, Yueh Ting; Feng, Ruozhu; Wang, Jin; Wang, Chien‐Lung; Wang, Wei; Zhu, Yu

doi:10.1038/s41560-021-00879-6

Cited by 89 publications

(86 citation statements)

References 47 publications

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“…Achieved capacity and voltage efficiency follow their typical trend with current density (Figure 6C). 58 The capacity percentage of high-voltage discharge, that is, that related to the monomer, increases from 30 to 80% at high current densities. Higher currents result in shorter charging cycles, giving the dimer less time to form in the battery.…”

Section: +mentioning

confidence: 99%

“…Ultraviolet -visible spectroscopy (UV-vis) was utilized to study the solubility of the iron complexes according to literature procedures. 24,58 First, a calibration curve with a suitable linear dynamic range was made from Fe(bpy) 3 SO 4 solutions of different concentrations to establish an experimental A vs [Fe(bpy) 3 2+ ] relationship for the characteristic 299 nm peak. Samples of various additives and salts were then saturated with Fe(bpy) 3 SO 4 , vortexed, ultrasonicated for 20 minutes, and centrifuged.…”

Section: Characterization Of Fe(bpy) 3 Somentioning

confidence: 99%

“…At 2.1 Â 10 À6 (control) and 1.6 Â 10 À6 cm 2 s À1 (IPA), the diffusion coefficients of Fe(bpy) 3 2+ are on par with the common ferrocyanide catholyte and should thus support highcurrent density RFBs. 58 The electron transfer rate constant for Fe(bpy) 3…”

Section: +mentioning

confidence: 99%

“…Long-term performance of Fe(bpy) 3 2+/3+ -based batteries is especially promising due to their large molecular size, which virtually eliminates membrane crossover, a major issue for the smaller and lower-potential ferrocyanide catholyte. 58 We attribute the observed capacity decay to incomplete regeneration of the Fe(bpy) 3 2+ species from sluggish dimer reduction (Scheme S1), thereby allowing a small amount of dimer species to accumulate with each cycle. Thus, it should be possible to completely refresh the catholyte solutions to full capacity by performing a periodic bulk electrolysis/rebalancing step, as is commonly done in other RFBs.…”

Section: +mentioning

confidence: 99%

“…Detailed fundamental investigations studying the exact mechanism of battery enhancement by CuHCF and the effectiveness of other PBAs are underway in our laboratory. such as direct functionalization of charged moieties 58 and/or metathesis to alternative counter-anions 39 ; however, the cost and practicality of such strategies should be weighed in guiding this exploration. Given the performance enhancements reported here for 1 M IPA as an additive, there may be an optimal binary solvent-electrolyte system between completely aqueous, non-aqueous that are traditionally studied.…”

Section: Cuhcfmentioning

confidence: 99%

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Isopropyl alcohol and copper hexacyanoferrate boost performance of the iron tris‐bipyridine catholyte for near‐neutral pH aqueous redox flow batteries

Bui

Holubowitch

2021

Intl J of Energy Research

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Aqueous redox flow batteries (ARFBs) are poised to be a major energy storage technology when coupled with rapidly proliferating renewable wind and solar power generation. The iron (II/III) tris-bipyridine redox couple, Fe(bpy) 3 2+/3+ , possesses several highly attractive properties for its use as a catholyte in ARFBs: high redox potential, low cost, mild pH operation, and negligible irreversible chemical degradation. Nevertheless, its main drawbacks -low solubility and poor voltage efficiency -remain to be improved. In this work, we report on the success of isopropyl alcohol (IPA) and copper hexacyanoferrate (CuHCF) electrolyte additives that address these shortcomings and ultimately lead to improved ARFB performance. IPA affords a nearly 3-fold increase in solubility (energy density) and longer cycle lifetimes (lower capacity fade rate), without sacrificing voltage efficiency against the control case. CuHCF dramatically enhances Fe(bpy) 3 2+/3+ -based ARFB voltage efficiency by 15 + % through an apparent catalytic mechanism not observed before. We showcase these additives in a novel, near-neutral pH ARFB system, 2,7-AQDS-Fe (bpy) 3 2+/3+ , that affords the highest energy density and efficiency to-date for this catholyte. In addition, unlike most previous studies, multiple batteries were constructed to reproduce and confirm the results. The findings open avenues for further improvement of this promising catholyte through the tuning of additive structure, composition, and battery integration.

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Section: +mentioning

confidence: 99%

Section: Characterization Of Fe(bpy) 3 Somentioning

confidence: 99%

Section: +mentioning

confidence: 99%

Section: +mentioning

confidence: 99%

Section: Cuhcfmentioning

confidence: 99%

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Isopropyl alcohol and copper hexacyanoferrate boost performance of the iron tris‐bipyridine catholyte for near‐neutral pH aqueous redox flow batteries

Bui

Holubowitch

2021

Intl J of Energy Research

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Organic Electrolytes for pH‐Neutral Aqueous Organic Redox Flow Batteries

Chen

Yuan

et al. 2021

Adv Funct Materials

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Due to decoupled energy and power, the aqueous organic redox flow battery (AORFB) represents a promising energy storage technology that stores energy in redox‐active organic compounds dissolved in aqueous electrolytes. The organic compounds are composed of earth‐abundant elements and are therefore potentially cost‐effective. Their structures are diverse and highly tunable, rendering it possible to regulate the redox potential, water solubility, and cycling lifespan. Therefore, the adoption of redox‐active organics greatly expands the space for enabling exceeding performance merits compared to their inorganic counterparts. Herein, this work reviews the molecular design and engineering scheme of organic electrolytes, focusing exclusively on pH‐neutral AORFB that uses non‐corrosive and nonflammable pH‐neutral aqueous electrolytes with inexpensive inorganic salts as supporting electrolytes and features high safety, low corrosivity, low cost, and environmental benignity. Some comments on the present challenges and prospects of this ascendant domain are also presented.

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Liquid‐State Cathode Enabling a High‐Voltage and Air‐Stable Fe‐Al Hybrid Battery

Yang

Liu

et al. 2023

Adv Funct Materials

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Aluminum (Al) is an ideal anode material in low‐cost battery system for energy storage, with high theoretical capacities. However, the sluggish Al3+‐involved kinetics challenges the selection of common cathode materials (Al3+ intercalation or conversion). Herein, a redox‐active Fe–Cl complex serves as the liquid‐state cathode to couple with a low‐cost Al anode, which synergizes the advantages of redox flow batteries and Al rechargeable batteries. The interplay of Fe‐Cl coordinated formula and electrochemical properties are revealed for the first time. It is found that [Fe2Cl7]− molecule has a high voltage versus Al anode (1.3 V), and the novel Fe‐Al hybrid battery fulfills a capacity of 1.6 mAh cm−2 (20 Ah L−1) record high in a coin cell among Al‐based batteries. Furthermore, the energy efficiency, which is a vital parameter to evaluate the energy cost of the energy storage technology, reaches 85% (superior to most Al‐based batteries) and an average of 70% over ≈900 h cycling. Particularly, the unique air‐stable character enables normal operation of the battery assembled in ambient air. This work establishes a new application scenario for Al anode toward low‐cost large‐scale energy storage.

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Symmetry-breaking design of an organic iron complex catholyte for a long cyclability aqueous organic redox flow battery

Cited by 89 publications

References 47 publications

Isopropyl alcohol and copper hexacyanoferrate boost performance of the iron tris‐bipyridine catholyte for near‐neutral pH aqueous redox flow batteries

Isopropyl alcohol and copper hexacyanoferrate boost performance of the iron tris‐bipyridine catholyte for near‐neutral pH aqueous redox flow batteries

Organic Electrolytes for pH‐Neutral Aqueous Organic Redox Flow Batteries

Liquid‐State Cathode Enabling a High‐Voltage and Air‐Stable Fe‐Al Hybrid Battery

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