An electrochemical–thermal model based on dynamic responses for lithium iron phosphate battery

• A model based on dynamic responses for LiFePO4 battery is developed.
• Effects of current collectors on LiFePO4 battery are considered in this model.
• Dynamic analysis for pulse behavior and electrochemical rates are conducted.
• Endothermic and exothermic phenomena in different discharge rates are discussed.

An electrochemical–thermal model is developed to predict electrochemical and thermal behaviors of commercial LiFePO4 battery during a discharging process. A series of temperatures and lithium ion concentrations dependent parameters relevant to the reaction rate and Li+ transport are employed in this model. A non-negligible contribution of current collectors to the average heat generation of the battery is considered. Simulation results on rate capability and temperature performance show good agreement with the literature data. The behavior of Li+ distribution at pulse-relaxation discharge, the variation of electrochemical reaction rate and thermal behavior at a constant current discharge are studied. Results of pulse-relaxation discharge describe the dynamic change of Li+ concentration distribution in liquid and solid phases, which is helpful to analysis the polarization of the battery. In constant current discharge processes, the electrochemical reaction rate of positive electrode has a regular change with the time and the position in the electrode. When discharge finished, there is still a part of the LiFePO4 material has not been adequately utilized. At low rate, the discharge process accompanies endothermic and exothermic processes. With the rate increasing, the endothermic process disappears gradually, and only exothermic process left at high rate.