Real-Time Study of the Disequilibrium Transfer in Vanadium Flow Batteries at Different States of Charge via Refractive Index Detection

Studying the disequilibrium transfer of the electrolyte in vanadium redox flow batteries is essential for the application of the batteries. Due to the lack of proper detection techniques, the real-time study of the disequilibrium transfer is difficult. In this paper, a real-time refractive index detector with high resolution is developed to study the material transfer in the positive electrolyte at different states of charge. It is found that the rapid imbalance of the electrolyte occurs at the initial state of battery operation, and the disequilibrium transfer rate of materials in the electrolyte accelerates with an increase of the state of charge. During the charge/discharge process, the disequilibrium transfers of vanadium and sulfate show different behaviors. This real-time refractive index detector is beneficial for studying the electrochemical process of vanadium flow batteries and helpful to the optimization of the operational parameter.