Experimental Study on the Effect of Operating Conditions on the Efficiency of Vanadium Redox Flow Battery

The operating conditions can have a negative impact on the efficiency of a vanadium redox flow battery (VRFB), and it is therefore important to systematically study how these conditions affect battery efficiency. In the experiment, various operating parameters such as charge/discharge cut-off voltage, flow rate, membrane thickness, current density, and shelving time are selected to evaluate their impact on battery efficiency. The experimental results indicate that increasing the range of the cut-off voltage reduces the battery's energy efficiency. Additionally, both coulomb efficiency and energy efficiency improve as flow rate increases, but these efficiencies decline after reaching a critical value. Increasing the thickness of the ion conduction membrane enhances its effectiveness in preventing the crossing of vanadium ions, resulting in lower capacity loss. Furthermore, an increase in current density intensifies ohmic polarization and concentration polarization, leading to a decrease in energy efficiency.