A Semi-Empirical Capacity Degradation Model of EV Li-Ion Batteries Based on Eyring Equation

Abstract

To ensure a reliable application of li-ion batteries on electric vehicles (EVs), life prediction of li- ion cells is very essential. The main objective of the present study is to propose a semi-empirical capacity fading model of li-ion batteries being practical for predicting the degradation of battery capacity under real working conditions. The capacity fading of li-ion cells is considered to be mainly caused by side reaction, which consumes the active materials. The main contribution of the study is that the model is not founded only empirically based on the experiment results, but also with the theoretical description of side reaction based on Eyring equation. By this combined model, it is expected to get an accurate and meanwhile practical model for performance prediction. The model takes DOD, temperature and current rate as three main factors affecting ageing process. The ageing tests were designed and implemented to get the parameters of the capacity fading model, and one validation experiment was used to evaluate the prediction performance of the model. There is a good agreement between the actual capacity degradation and predicted capacity degradation.