Thermal issues of vanadium redox flow batteries

Vanadium redox flow batteries (VRFBs) are one of the most promising technologies for renewable energy storage. However, complex thermal issues caused by excessive heat generation during high-rate operations and various heat transfer behaviors in diverse climates dramatically affect the efficiency and stability of VRFBs. In this review, we summarize the thermal issues of VRFBs reported in the literature. First, the fundamental mechanisms of heat generation and heat transfer are elaborated. Thermal effects on electrochemical reactions and critical components in VRFBs are then presented. An operating temperature range of 10∼40 °C for VRFBs with high efficiency, weak side reactions, high electrolyte stability, and low crossover is suggested. Furthermore, thermal models including two-dimensional models, three-dimensional models, and lumped models are summarized. Moreover, existing thermal management methods are analyzed. Employing titanium heat exchangers with anti-corrosive properties to adjust the temperature of electrolytes is recommended. Finally, the remaining challenges to enhance the efficiency and stability of VRFBs under harsh thermal conditions are provided. This review offers an in-depth insight into the thermal issues of VRFBs, facilitating the design of next-generation VRFBs with high-power density.