Monitoring dynamic thermal behavior of the carbon anode in a lithium-ion cell using a four-probe technique

We describe a four-probe electrical technique that enables real-time temperature monitoring of the carbon anode in a 53 Ah lithium-ion rechargeable cell during charging and discharging. This technique uses only electrical contacts to the positive and negative terminals of the cell, eliminating the need to insert temperature sensors inside the cell. Our method is based on the intrinsic relationship of anode temperature with phase shift between an applied sinusoidal current and the resulting voltage, valid within the 5% and 95% range of the state-of-charge (SoC) of the cell. Using this technique, we demonstrate that the anode temperature (Tanode) can deviate from the temperature measured at the outside surface (Tsurf) of the cell during charge and discharge. Additionally, we show that anode temperature is primarily determined by entropy change at the anode or by resistive impedance of the anode, depending on the environment temperature (Tenv).

► A technique to monitor on-line the temperature of the carbon anode in Li-ion cell is described.
► It is based on correlation between the anode temperature and the impedance of the anode.
► It finds charging at room temperature environment causes the cell to cool and the anode to heat.
► Discharging heats the anode in low-temp. environment, and cools it in high-temp. environment.
► Entropy or impedance determines the anode temp., depending on the temperature of the environment.