Investigation of Capacity Decay due to Ion Diffusion in Vanadium Redox Flow Batteries

Redox flow batteries are becoming prominent in the purview of grid-scale energy storage. Among the present RFB technologies, Vanadium Redox Flow Battery is the most promising mainly because cross-contamination of electrolytes is avoided. However, diffusion of vanadium ions through the membrane causes capacity decay. In this paper, the issue of capacity decay is investigated. The capacity loss due to vanadium ion diffusion is simulated for 10000 cycles of operation. The effect of flow rate on concentration flux in the cell is studied since concentration difference between two half cells is one of the major reasons for species crossover. As a consequence of diffusion, the charge transfer current density in the electrode varies. The relationship between charge transfer current density and the concentration of one species of vanadium is analyzed at different temperatures.