The rapid developments in the field of electrochemistry, enabled lithium-ion batteries to achieve a very good position among all the other types of energy storage devices. Therefor they became an essential component in most of the modern portable and stationary energy storage applications, where the specific energy plays an important role. In order to analyze and optimize lithium-ion batteries an accurate battery model for the dynamic behavior is required. This paper presents a comparison between equivalent circuit diagrams and fractional rational functions with the complex variable s for lithium-ion battery modeling. It is described how to identify the parameters of the models in both time and frequency domains. The validation of the different models is done for high and low dynamic current profiles. In the first step the dependency of all model parameters on the temperature and on the battery age is neglected
