Parameter identification of electrochemical-thermal coupling model for high-capacity LiFePO4 battery over wide temperature range

In recent years, research on high-capacity lithium-ion batteries has become increasingly active. Due to the significant influence of temperature on the electrochemical reaction process of batteries, a single electrochemical model is no longer able to describe the behavior of high-capacity batteries. Therefore, the coupling effect of temperature factors needs to be considered in the modeling process. A multi-step parameter identification method for the electrochemical-thermal coupling model of lithium-ion batteries was proposed, taking 198Ah LiFePO4/graphite batteries as the research object. This method first designed short-term pulse experiments at different temperatures to identify the reaction rate constants and SEI membrane impedance by using genetic algorithms. Next, different charging multiplicity experiments were designed at different temperatures, and a method was proposed to identify the solid-phase diffusion coefficients by dividing the SOC intervals according to the characteristics of electrode active materials. Meanwhile, the Arrhenius formula was modified. Finally, the activation energies of the relevant parameters were obtained by fitting with the Arrhenius formula. The obtained model parameters were introduced into the proposed model, and the accuracy of the identified battery parameters and the coupling model was verified by comparing the simulation results and experimental results of the model under different temperatures and operating conditions.