Understanding and modeling the electrochemical behavior of redox flow batteries is essential for evaluating state of charge and predicting charge–discharge characteristics. In this research, we focus on the role of separators and porous carbon felts by examining their resistive and capacitive properties, which directly affect charge transfer and mass transport processes. To enhance separator performance, Celgard™ membranes were modified with polyvinyl alcohol (PVA) and treated with methanol, allowing us to investigate electrolytic environments both with and without metal-based species. Electrochemical impedance spectroscopy (EIS) was employed to generate Nyquist plots, from which equivalent RLC circuit models were derived. These models distinguish ohmic resistance, ionic resistance, and capacitance contributions under flow and no-flow conditions in symmetric full-cell hardware. By coupling material modifications with circuit-level analysis, we aim to establish a clearer connection between separator design, electrolyte composition, and electrochemical response. This framework also lays the groundwork for upcoming iron crossover experiments, which will further assess how permeable electrodes and composite separators influence performance and long-term viability of redox flow battery systems.
