Modeling of SEI Layer Growth and Electrochemical Impedance Spectroscopy Response using a Thermal-Electrochemical Model of Li-ion Batteries

Abstract

Lithium-ion batteries (LIBs) suffer severe performance degradation during their lifetime application because of the undesired chemical reactions, ageing, corrosion, structural integrity compromise, and the threat of thermal runaway. Formation of new SEI layer and its growth cause LIBs internal resistance increase and capacity loss, leading to performance degradation. In order to comprehensively investigate the effects of SEI growth on battery performance and cell electrochemical impedance spectroscopy (EIS) response, a one-dimensional thermal-electrochemical model was developed. The model is able to reveal the effects of diffusivity, kinetics, and temperature on SEI layer growth and cell capacity fade. Based on the thermal-electrochemical model developed, one more mathematical model is developed to simulate the impedance response of LIBs with considering the double layer capacitance effect. The simulated impedance response is analyzed to reveal LIBs impedance behaviors, which can be used to predict the degradation mechanism of LIBs. With the layer becoming thicker, its growth rate slows down gradually due to increased diffusion resistance. SEI grows more quickly during charge than discharge due to the difference in electron flux through the SEI layer and the temperature change during cycling. Temperature rise due to reaction and joule heating accelerates the SEI layer growth and causes more capacity loss. This work can provide us the insights of combining LIBs EIS analysis with degradation analysis.