Extensive EIS characterization of commercially available lithium polymer battery cell for performance modelling

Electrochemical Impedance Spectroscopy (EIS) has become a popular analytical technique for research and development of battery cells´ chemistries, due to the established, high precision computer controlled equipment, that are capable of direct, on-line monitoring of performance parameters or degradation of an electrochemical system. Used for Lithium-ion (Li-ion) batteries, this method allows for a fast and accurate assessment of the battery´s impedance at any working point, without modifying the state of the battery. The influence of the operating conditions, state of charge (SOC) and temperature on the performance of a commercially available 53 Ah Lithium polymer battery cell, manufactured by Kokam Co. Ltd., is investigated in laboratory experiments, at its beginning of life, by means of EIS. A data fitting algorithm was used to obtain the parameter values for the proposed equivalent electrical circuit, which was further selected for the development of an accurate EIS based performance model for the chosen Li-ion battery cell.