High-Precision Battery Temperature Estimation Using the Impedance Method

<p>This paper reports a highly accurate method for estimating the internal temperature of batteries over a wide temperature range using impedance spectroscopy. Traditional methods for impedance-based temperature estimation are accurate at low and ambient temperatures, but suffer from poor accuracy at high temperatures (>50°C). In this study, we identified the problems with existing methods and significantly improved the temperature estimation accuracy over a wide temperature range, including high temperatures. We first systematically analyzed how the frequencies representing the detailed reactions inside the battery changed with temperature, using equivalent circuit analysis. It has been confirmed that the impedance signal at frequencies traditionally used for temperature estimation has been assumed to reflect only the behavior of the anode film layer, but in reality it contains signals related to charge transfer reactions especially at high temperatures (>50°C). The impedances at higher frequencies, which reflected only the film layer behavior at high temperatures, caused signal disturbances owing to an undesirable stray inductance. Therefore, in this study, we aimed to improve the accuracy of temperature estimation at high temperatures by increasing the estimation frequency and simultaneously compensating for stray inductance. Compared to existing methods, the proposed approach achieves exceptionally high accuracy in temperature estimation across a wide temperature range (–10 to 80°C), with a pronounced increase in accuracy at high temperatures.</p>