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Coordination chemistry in advanced redox-active electrolyte designs

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Abstract

Coordination chemistry is central to the development of redox-active electrolytes for various applications, including electroplating, molecular screening, biomedicine, artificial synthesis and energy storage. This Review focuses on the role of coordination chemistry in the design of redox-active electrolytes for aqueous redox flow batteries. We analyse the key thermodynamic and kinetic properties of electrolytes through the framework of crystal-field theory, emphasizing how ligand properties, ligand-field effects and entropy influence redox potential, solubility and structural stability. We also discuss how coordination chemistry fine-tunes microscopic dynamic properties, thereby influencing electrochemical performance. In addition, we discuss characterization techniques that enable deep insight into the structure–function relationships of coordination-based electrolytes. Finally, we outline future directions for rational electrolyte design guided by coordination chemistry principles, with the aim to produce next-generation aqueous redox flow batteries with enhanced performance and tunability.

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Fig. 1: Evolution of coordination chemistry and its application in aqueous redox flow batteries.
Fig. 2: Electron configuration of central metal ions and their coordination properties.
Fig. 3: Three factors affecting metal-ion properties.
Fig. 4: Thermodynamic properties of redox-active metal–ligand complexes.
Fig. 5: Kinetic properties of aqueous redox flow batteries.
Fig. 6: Structural and operando characterization techniques for coordination complexes.

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Acknowledgements

The work described in this paper was supported by grants from the Research Grant Council of the Hong Kong Special Administrative Region, China (project nos RFS2223-4S03, CUHK 14308622 and CUHK 14302823). Y.-C.L. acknowledges the support from Xplorer Prize by New Cornerstone Science Foundation.

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    Fei Ai & Yi-Chun Lu

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Ai, F., Lu, YC. Coordination chemistry in advanced redox-active electrolyte designs. Nat Rev Mater (2025). https://doi.org/10.1038/s41578-025-00833-y

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