Impact of Electrical and Thermal Abuse on the Internal Temperature Estimation of Li-Ion Cells Using Electrochemical Impedance Spectroscopy
Various battery-related fires have been reported in the recent years. To improve the safety of battery users, it is important to be able to predict a potential thermal runaway event well ahead of time. Since such battery fires are typically preceded by a spontaneous increase in the cells' temperature, the estimation of the cell's internal temperature could be one of the methods to predict the onset of thermal runaway. In a previous work, the present authors proposed a cell temperature estimation method using electrochemical impedance spectroscopy, and validated it under different normal operating conditions. However, under abuse conditions, the cell's EIS spectra can be altered significantly, consequently affecting the accuracy of this method. This work, therefore, focuses on the assessment of the applicability of this method in the event of such a cell abuse.It is found that in the case of an electrical abuse, an abnormal spike in the estimated temperature is observed, which may indicate that the cell is under a form of abuse. Moreover, the real part of the cell's impedance also increases significantly, which can also be used as an indicator for cell abuse. For thermal abuse, the temperature estimation is accurate until 60 °C, which is greater than the maximum operating temperature of the cell (55 °C). Hence, the estimation of this temperature itself can indicate that the cell is under thermal abuse. Moreover, it is shown that the real part of the cell's impedance (Re(Z)) can be estimated from the phase of its impedance. Under normal operating conditions, the error between the measured and estimated value of Re(Z) should be within a certain threshold. Therefore, if this error is higher than this threshold, a warning can be triggered, notifying the user that the cell is not under normal operating conditions. Finally, it is observed that after 60 °C, the real part of the cell's impedance increases with temperature. This is an abnormal event, since the cell's resistance typically decreases with temperature. Hence, this can also be used as an indicator of the cell's thermal abuse.
2025
Elsevier BV
EPFL