Equivalent Circuit Modeling from Electrochemical Impedance Spectroscopy for Aqueous Redox Flow Battery Characterization and Performance

Electrochemical equivalent circuit models for redox flow batteries are key in assessing current state of charge and predicting overall charge-discharge performance. The electrochemical characterization and performance analysis of separators and porous carbon felts for their application in redox flow batteries will help inform the selection of components based on properties such electronic and ionic resistance and capacitance associated with the charge transfer and the mass transfer. From analysis of the Nyquist plots obtained with electrochemical impedance spectroscopy (EIS), an RLC model is developed to identify the ohmic and ionic resistance along with capacitance in both flow and no-flow conditions in symmetric full flow cell hardware with hydrogel coatings onto Celgard^TM. A fundamental understanding of the contributions of each component will also allow for further experimentation in electrolyte chemistries with specific permeable electrode and composite separator combination for redox flow battery applications.