It is important to note that the capacity decay over long-term cycling is cumulative and therefore, capacity decay due to vanadium crossover and degradation are combined in cycling experiments making it challenging to distinguish the contribution from these two sources independently.
In this work, we will present our latest experimental data focused on delineating contributions from vanadium crossover and electrode degradation. The data include two ion-exchange membranes and two electrodes with different degradation behavior.
To this end, we have designed and built a unique facility utilizing multiple electrochemical and flow cells equipped with UV/Vis spectroscopy to measure the vanadium ion crossover in real-time 2-6. To assess the capacity decay due to combined degradation effect of all components, we have developed another diagnostic in which we use a symmetric cell set-up for negative (V(II)/V(III)) and positive (V(IV)/V(V)) sides separately. The degradation diagnostics utilize electrochemical impedance spectroscopy to quantify the contributions of cell overpotential during cycling stemming from charge-transfer, ohmic and mass transport.
The results of this study should provide more in-depth insight to optimize VRFBs with enhanced performance and reduced ion-crossover and degradation.
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