The AC Impedance Characteristic of High Power Li 4 Ti 5 O 12 -based Battery Cells

This paper studies the impedance characteristics of a fresh 13 Ah high-power lithium titanate oxide (LTO) battery cell and analyses its dependence on the temperature and state-of-charge. The impedance of the battery cell was measured by means of the electrochemical impedance spectroscopy (EIS) technique for the entire state-of-charge (SOC) interval and considering five temperatures between 5°C and 45°C. By analyzing the measured impedance spectra of the LTO-based battery cell, it was found out that the cell's impedance is extremely dependent on the operating conditions. By further processing the measurements data by means of curve fitting, it was found that the parameters of the equivalent electrical circuit (and the corresponding electro-chemical processes) are following different dependencies on the SOC, which in most of the cases are only slightly changing with the measurement temperature