Multiphysical modeling for life analysis of lithium-ion battery pack in electric vehicles

With the continuous improvement in battery life requirements, the modeling, analysis and management of battery pack life become an important topic in the design of electric vehicles. A more realistic and generic modeling method coupling the electrochemical, thermal, SEI formation model of cells, fluid dynamics and the series-parallel circuit model is proposed to accurately describe the coupling relationships and quantify the inconsistencies, including temperature and current. A life model including capacity fade and reliability is established to evaluate the life of lithium-ion battery pack system (LIBPs). And a model implementation method is established to raise the computational accuracy and efficiency, then, it is validated from the perspective of electrochemical, degradation, thermal performance and coupling effect using experiments. Moreover, the multiphysical behavior and life of LIBPs in different situations are analyzed and predicted, followed by the analysis of coupling effect, inconsistency, reliability and economy. The results show the degradation rate of LIBPs first decreases and then accelerates in the whole life. Furthermore, adding series cells is uneconomical to extend the life of LIBPs. Finally, a SoH balanced management method of changing the airflow direction is proposed to extend the life of LIBPs, and the optimal strategy for different SoH inconsistency are obtained.