A spreadsheet-based redox flow battery cell cycling model enabled by closed-form approximations

The complex interplay between numerous parasitic processes—voltage losses, crossover, decay—challenges interpretation of cycling characteristics in redox flow batteries (RFBs). Mathematical models offer a means to predict cell performance prior to testing and to interpret experimentally measured cycling data, however most implementations require extensive domain knowledge and computational resources. To address these challenges, we previously developed a computationally inexpensive zero-dimensional modeling approach by deriving analytical solutions to species mass balances during cell cycling. Here, we expand on this framework by deriving closed-form expressions for key performance metrics and comparing the accuracy of these simplifications to the complete analytical model. The resulting closed-form model streamlines the computational structure and allows for spreadsheet modeling of cell cycling behavior, which we highlight by developing a simulation package in Microsoft® Excel®. We then apply this model to analyze previously published experimental data from our group and others, highlighting its utility in numerous diagnostic configurations—bulk electrolysis, compositionally unbalanced symmetric cell cycling, and full cell cycling. Given the accessibility of this modeling toolkit, it has potential to be a widely deployable tool for RFB research, aiding in data interpretation, performance prediction, and electrochemistry education.