Development of electrolyte thermodynamic studies for vanadium flow battery

Vanadium flow battery is being attracted more and more attentions because it can be used for large-scale electrical energy storage. Different from other types of secondary batteries, the electrolyte of vanadium flow battery (VLB) is not only the ion conductor, but also serves as the electrochemical active substances for storing energy. In order to make the batteries more stable and more efficient, it is indispensable to understand thermodynamic properties of the electrolyte. The thermodynamics of vanadium solution can provide us useful information including the ion existing form in the solution, activity of vanadium ions and their disassociation constants etc. In this review, we will summarize the recent development of thermodynamic studies of vanadium flow batteries including experimental methods such as calorimetry, densimetry and conductivity methods. The Pitzer's theory is also introduced to describe the vanadium electrolyte. Besides, the future work on thermodynamic studies for vanadium flow battery has been put forward.