Evaluation and Development of a 3-Electrode Measuring System for Flow Batteries

This thesis presents the development, validation, and evaluation of an advanced three-electrode measurement system designed for in-depth half-cell testing of flow batteries. The research addresses a gap in the setup by enabling more precise investigation of electrode processes and mass transport phenomena under realistic operating conditions.
Two innovative half-cell test setups - a modular “Flex-Cell” and a comparative “Flow-Frame” - were designed and constructed, allowing for systematic control of electrolyte flow and effective integration of various electrode and reference electrode configurations. A set of redox chemistries, including AQDS, potassium ferrocyanide/ferricyanide, and zinc sulfate, were tested to explore the electrochemical behavior and reproducibility across different systems. Special emphasis was placed on cyclic voltammetry (CV) as a principal diagnostic technique, with a focus on mass transport, reaction kinetics, and the influence of hydrodynamics on electrochemical signals.
The primary findings indicate that limiting currents in CV measurements consistently rise with flow rate, attributable to augmented convective transport, thereby validating the essential function of electrolyte movement in operational flow battery systems. The behavior of oxidation and reduction peak currents, on the other hand, is complicated and hard to predict. This is because of local diffusion, kinetic interactions, and factors that are specific to each electrode. A direct comparison of flow and non-flow conditions, as well as different electrode plate designs, showed how important it is to standardize measurement protocols for reliable, comparable results.
Validation was guaranteed through repeated testing and comparison with non-flow baselines, confirming the reproducibility and dependability of the established configurations. The study delineates a definitive methodology for subsequent researchers, proffers recommendations for optimal practices in the electrochemical testing of flow batteries and underscores the significance of diagnostic adaptability in the interpretation of dynamic systems.
Overall, this work delivers both a reliable methodological foundation and a practical guide for next-generation redox flow battery studies. By enabling more precise, reproducible assessment of new materials, flow designs, and electrode technologies, this work helps close the gap between theory and commercial practice.