Redox Flow Batteries: Electrolyte Chemistries Unlock the Thermodynamic Limits

Chen, Ruiyong

doi:10.1002/asia.202201024

Cited by 9 publications

(3 citation statements)

References 166 publications

(416 reference statements)

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“…However, compared with an organic solvent, an aqueous electrolyte provides lower cell voltage due to the relatively narrow thermodynamic stability window of water (1.23 V under standard conditions). The HER and the OER of water can be significantly suppressed by using suitable electrode materials and electrolyte composition 92,93 . Because of the slow kinetics of HER and OER, the electrochemical stability window of aqueous electrolytes can be substantially larger than their thermodynamic limits.…”

Section: Current Concepts and Strategiesmentioning

confidence: 99%

“…The HER and the OER of water can be significantly suppressed by using suitable electrode materials and electrolyte composition. 92,93 Because of the slow kinetics of HER and OER, the electrochemical stability window of aqueous electrolytes can be substantially larger than their thermodynamic limits. Similarly, the electron transfer kinetics of redox molecules for the redox reaction is always much faster than those of water-splitting reactions, which is why the redox molecules remain electrochemically stable.…”

Section: Strategies For Building High-voltage Aorfbsmentioning

confidence: 99%

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Development of organic redox‐active materials in aqueous flow batteries: Current strategies and future perspectives

Pan

Shao

Jin³

2023

SmartMat

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Aqueous redox flow batteries, by using redox‐active molecules dissolved in nonflammable water solutions as electrolytes, are a promising technology for grid‐scale energy storage. Organic redox‐active materials offer a new opportunity for the construction of advanced flow batteries due to their advantages of potentially low cost, extensive structural diversity, tunable electrochemical properties, and high natural abundance. In this review, we present the emergence and development of organic redox‐active materials for aqueous organic redox flow batteries (AORFBs), in particular, molecular engineering concepts and strategies of organic redox‐active molecules. The typical design strategies based on organic redox species for high‐capacity, high‐stability, and high‐voltage AORFBs are outlined and discussed. Molecular engineering of organic redox‐active molecules for high aqueous solubility, high chemical/electrochemical stability, and multiple electron numbers as well as satisfactory redox potential gap between the redox pair is essential to realizing high‐performance AORFBs. Beyond molecular engineering, the redox‐targeting strategy is an effective way to obtain high‐capacity AORFBs. We further discuss and analyze the redox reaction mechanisms of organic redox species based on a series of electrochemical and spectroscopic approaches, and succinctly summarize the capacity degradation mechanisms of AORFBs. Furthermore, the current challenges, opportunities, and future directions of organic redox‐active materials for AORFBs are presented in detail.

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Section: Current Concepts and Strategiesmentioning

confidence: 99%

Section: Strategies For Building High-voltage Aorfbsmentioning

confidence: 99%

Development of organic redox‐active materials in aqueous flow batteries: Current strategies and future perspectives

Pan

Shao

Jin³

2023

SmartMat

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“…However, the contribution of configurational entropy is hard to describe accurately with the implicit solvation model in DFT calculations, and the predicted redox potentials would differ from the experimental values considerably for some organic molecules . On the other hand, complex supporting electrolytes, such as water-in-ionic liquid, − water-in-salt electrolytes, , and hybrid electrolytes − and so on, cannot be treated easily due to the complex parametrization of the implicit solvation model . To take these into consideration, ab initio molecular dynamics (AIMD) has been applied. − By treating the solvents at the same level of electronic structure theory and sampling the configurational space with molecular dynamics (MD), the reorganization of solvent molecules during redox reaction can be captured.…”

Section: Introductionmentioning

confidence: 99%

Accelerating Computation of Acidity Constants and Redox Potentials for Aqueous Organic Redox Flow Batteries by Machine Learning Potential-Based Molecular Dynamics

Wang,

Ma,

Cheng

2024

J. Am. Chem. Soc.

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Due to the increased concern about energy and environmental issues, significant attention has been paid to the development of large-scale energy storage devices to facilitate the utilization of clean energy sources. The redox flow battery (RFB) is one of the most promising systems. Recently, the high cost of transition-metal complex-based RFB has promoted the development of aqueous RFBs with redox-active organic molecules. To expand the working voltage, computational chemistry has been applied to search for organic molecules with lower or higher redox potentials. However, redox potential computation based on implicit solvation models would be challenging due to difficulty in parametrization when considering the complex solvation of supporting electrolytes. Besides, although ab initio molecular dynamics (AIMD) describes the supporting electrolytes with the same level of electronic structure theory as the redox couple, the application is impeded by the high computation costs. Recently, machine learning molecular dynamics (MLMD) has been illustrated to accelerate AIMD by several orders of magnitude without sacrificing the accuracy. It has been established that redox potentials can be computed by MLMD with two separated machine learning potentials (MLPs) for reactant and product states, which is redundant and inefficient. In this work, an automated workflow is developed to construct a universal MLP for both states, which can compute the redox potentials or acidity constants of redox-active organic molecules more efficiently. Furthermore, the predicted redox potentials can be evaluated at the hybrid functional level with much lower costs, which would facilitate the design of aqueous organic RFBs.

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Organic Electroactive Materials for Aqueous Redox Flow Batteries

et al. 2023

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Organic electroactive materials take advantage of potentially sustainable production and structural tunability compared to present commercial inorganic materials. Unfortunately, traditional redox flow batteries based on toxic redox‐active metal ions have certain deficiencies in resource utilization and environmental protection. In comparison, organic electroactive materials in aqueous redox flow batteries (ARFBs) have received extensive attention in recent years for low‐cost and sustainable energy storage systems due to their inherent safety. This review aims to provide the recent progress in organic electroactive materials for ARFBs. The main reaction types of organic electroactive materials are classified in ARFBs to provide an overview of how to regulate their solubility, potential, stability, and viscosity. Then, the organic anolyte and catholyte in ARFBs are summarized according to the types of quinones, viologens, nitroxide radicals, hydroquinones, etc, and how to increase the solubility by designing various functional groups is emphasized. The research advances are presented next in the characterization of organic electroactive materials for ARFBs. Future efforts are finally suggested to focus on building neutral ARFBs, designing advanced electroactive materials through molecular engineering, and resolving problems of commercial applications.

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Redox Flow Batteries: Electrolyte Chemistries Unlock the Thermodynamic Limits

Cited by 9 publications

References 166 publications

Development of organic redox‐active materials in aqueous flow batteries: Current strategies and future perspectives

Development of organic redox‐active materials in aqueous flow batteries: Current strategies and future perspectives

Accelerating Computation of Acidity Constants and Redox Potentials for Aqueous Organic Redox Flow Batteries by Machine Learning Potential-Based Molecular Dynamics

Organic Electroactive Materials for Aqueous Redox Flow Batteries

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