Coordination chemistry in advanced redox-active electrolyte designs

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.