An electrochemical‐thermal coupled model for aqueous redox flow batteries

•An electrochemical-thermal coupled model is developed for thermal analysis of ARFBs.•The ohmic resistance varies with temperature and state of charge.•All key components are integrated into the heat transfer network.•Simulation results of multi-cycle operations of VRFBs system are first validated. The performance and reliability of aqueous redox flow batteries (ARFBs) are closely related to the operating temperature. Therefore, it is essential to build a robust method to predict their thermal behaviours. In this work, an electrochemical-thermal coupled model is developed to predict the heat generation and temperature variation of ARFBs system. Specifically, the ohmic resistance of ARFBs stack in this model changes with the temperature and state of charge, and all key components (electrolytes, tanks, pipes, etc.) of ARFBs system are considered in the overall heat transfer network. Resultantly, such electrochemical-thermal coupled model is first validated by multi-cycle experimental results of vanadium redox flow batteries (VRFBs) stack under different current densities (100 and 400 mA cm−2). Based on this model, the thermal behaviours of VRFBs system can be accurately simulated. Specifically, the heat generation of electrochemical reaction and overpotential contributes a lot compared with that of shunt current and crossover reaction, meanwhile the temperature of electrolytes is at least 3.0 °C higher than that of other key components. This work not only offers an accurate method to predict the heat generation and temperature variation of ARFBs, but also provides a theoretical guidance for the operation and maintenance of ARFBs system.