Estimation of activity coefficients for aqueous organic redox flow batteries: Theoretical basis and equations

• Published in: iScience 2022-09, Vol.25 (9), p.104901-104901, Article 104901
• Main Authors: Mourouga, Gaël, Chery, Déborah, Baudrin, Emmanuel, Randriamahazaka, Hyacinthe, Schmidt, Thomas J., Schumacher, Juergen O.
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Chemistry; Computational chemistry; Electrochemical energy storage; Electrochemistry; Material chemistry
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2022.104901

The field of aqueous organic redox flow batteries (AORFBs) has been developing fast in recent years, and many chemistries are starting to emerge as serious contenders for grid-scale storage. The industrial development of these systems would greatly benefit from accurate physics-based models, allowing to optimize battery operation and design. Many authors in the field of flow battery modeling have brought evidence that the dilute solution hypothesis (the assumption that aqueous electrolytes behave ideally) does not hold for these systems and that calculating cell voltage or chemical potentials through concentrations rather than activities, while serviceable, may become insufficient when greater accuracy is required. This article aims to provide the theoretical basis for calculating activity coefficients of aqueous organic electrolytes used in AORFBs to provide tools to predict the concentrated behavior of aqueous electrolytes, thereby improving the accuracy of physics-based models for flow batteries. [Display omitted] •This article reviews the use of concentrated solution theory in flow batteries•The virial matrix method for estimating activity coefficients is proposed•Its high accuracy and experimental costs are underlined•A novel method, the reduced virial matrix, is proposed Chemistry; Electrochemistry; Electrochemical energy storage; Computational chemistry