Impedance model of lithium ion polymer battery considering temperature effects based on electrochemical principle: Part I for high frequency

• Modeled double layer behavior on electrode surface of Li-ion battery.
• Employed modified Gouy-Chapman-Stern method in the model.
• Improved ion transport equation in electrolyte bulk.
• Analyzed the performance of separated sub-models as well as integrated model.

Measurement of impedance is one of well-known methods to experimentally characterize electrochemical properties of Li-ion batteries. The measured impedance responses are generally fitted to an equivalent circuit model that is composed of linear and nonlinear electric components that mimic behaviors of different layers of a battery. However, the parameters do not provide quantitative statements on charge dynamics considering material properties. Therefore, electrochemical models are widely employed to study the charge dynamics, but have not included high frequency responses predominantly determined by double layers. Thus, we have developed models for the double layer and bulk that are integrated into the electrochemical model for a pouch type Li-ion battery. The integrated model is validated against the frequency response obtained from EIS equipment at different temperatures as well as the time response. The results show that the proposed model is capable of representing the responses at charging and discharging in time and frequency domain.