Li-ion Battery Internal Temperature Estimation using Electrochemical Impedance Spectroscopy

Thermal runaway is a growing concern in the field of Lithium ion batteries. To address this, temperature measurement is the most direct method. However, placing temperature sensors on each cell of a battery pack may be impractical. An alternative is to estimate temperature of a cell by using Electrochemical Impedance Spectroscopy (EIS). Literature has shown that the phase of the impedance of the cell can be correlated to its internal temperature, but a simple procedure to identify the frequency at which the phase should be calculated has not been reported. In this work, a methodology is developed to identify the frequency at which the phase of the impedance of the cell should be calculated by using the Distribution of Relaxation Times (DRT) technique. The methodology has also been validated on cells of different form factors (cylindrical and pouch) and also for cells under load.