Influences of various factors on the electrochemical performance of vanadium electrolytes

Vanadium flow battery systems consist mainly of membrane separators, electrode plates,electrodes, electrolyte storage tanks and circulation pumps. Energy storage is realized through changes to vanadium ion valence states in the charge and discharge processes. In this study, effects of vanadium electrolyte concentration and temperature on the electrochemical cyclic voltammetric behavior are investigated. The results show that, for a given temperature, the number of ions participating in the electrochemical reactions increases with increasing vanadium ion concentrations, leading to an increased output current. However, the reversibility of electrochemical reaction becomes poorer with increasing vanadium ion concentration. For a given vanadium concentration in the electrolyte, the peak current due to oxidation and reduction reactions increases with increasing temperature. The results also show that the current density of the electrochemical reactions could be increased by increasing the temperature of vanadium electrolyte within a certain range. For a given vanadium concentration in the electrolyte, the sulfuric acid concentration is also an important factor with 3 mol/L giving a good performance of vanadium electrolyte.