Analysis of vanadium species(V(IV)/V(III) in the electrolyte manufacturing process for vanadium redox flow battery using digital image

It is important to analyze concentrations of vanadium species with different valences in the electrolyte for vanadium redox flow battery (VRFB) for production of electrolytes and stable operation of the batteries. Herein, we proposed an analytical method by digital imaging to determine the vanadium species (V(IV)/V(III)) concentrations in the vanadium electrolyte manufacturing process. Standard electrolytes with different V(IV):V(III) ratios underwent digital imaging and the RGB values were extracted from the obtained images, and then the calibration curve was plotted based on these values. The data obtained from the blue channel were used as the analytical signal because it showed the best sensitivity and linearity (R2 = 0.9836, 0.9909). Precisions were determined using electrolyte samples with 50% and 100% V(III), respectively, and their RSDs were 2.18% and 1.01%, respectively. The accuracy of the digital imaging analysis method was evaluated by comparison with potentiometric titration, and the agreement was well made within the error limit. The results showed that this simple analytical method might be very suitable for real-time analysis of vanadium electrolyte.