Abstract: Life prediction and performance state estimation online are important in the life stage for each lithium-ion battery in electrical vehicles (EVs). The battery capacity and internal resistance were used to compare the model structure and the chemical meaning of eigen-parameters of two basic approaches; one is the identification of specific parameters based on the Equivalent Circuit Model (ECM) in the time domain and the other is Electrochemical Impedance Spectroscopy (EIS) analysis in the frequency domain. The results show that the common inherent conflict between the nonlinearity of batteries and the linearization of the identification algorithm constrains the development of lithium-ion battery in EV. Therefore, proposals such as aging mechanism, new life modeling approach, hardware structures and algorithm improvement are given to resolve the difficulties encountered in the implementation of battery life estimation online for lithium-ion systems.

Key words:  lithium-ion battery, battery life, internal resistance, electrochemical impedance spectroscopy (EIS), equivalent  circuit model (ECM)