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The vanadium flow batteries that employ the vanadium element as active couples for both half-cells, thus avoiding cross-contamination, are promising large-scale energy storage devices. In this work, the flow rate is optimized by incorporating the temperature effects, attempting to realize a more accurate flow control and subsequently enhance the performance of vanadium flow batteries. This work starts with the development of a comprehensive dynamic model on the basis of mass conservation, followed by a modeling validation and a thorough investigation of the temperature effects on electrolyte viscosity and internal resistance. After that, the flow rate is optimized to incorporate such effects. It is found that the flow rate strategy needs to be regulated with the variation of temperature due to the variations of electrolyte viscosity and internal resistance. Moreover, a relatively low flow rate is preferable for low-temperature applications, while for the high-temperature use, a relatively high flow rate is encouraged. Such in-depth investigation can not only provide a cost-effective method to optimize the flow rate and predict the behaviors of vanadium flow batteries, but can also be of great benefit to the management, application, and promotion of vanadium flow batteries.

A vanadium flow battery employing vanadium elements of different valences as the active substances for both sides is a promising device for large-scale energy storage applications. Here, a vanadium flow battery dynamic model incorporating the variable vanadium ion permeabilities and cell resistance is proposed, and the cell performance is subsequently analyzed and optimized. The variation of permeability and resistance is tested, and a laboratory flow cell is engaged for simulation. The results demonstrated that: i) the proposed model provides superior prediction precision compared to existing models with constant permeability and resistance; ii) operation in a temperature range of 25-35°C is favored to achieve an improved energy efficiency; iii) low and high operating temperatures are respectively preferred for vanadium flow batteries operated at low and high current densities. Such in-depth analysis can not only be highly beneficial to the operation and optimization of vanadium flow batteries to realize an enhanced performance, but offer a cost-effective modeling method with high accurate prediction precision to understand the characteristic and behavior of vanadium flow batteries within a wide operating temperature as well, thus avoiding large amounts of experimental testing that expends extensive materials and time.