Evaluation of the orientation impact on thermal behavior of cylindrical Li-ion batteries in different cycling conditions using fiber Bragg grating sensors

In this work, optical fiber Bragg grating (FBG) sensors were used to evaluate the thermal performance of an 18650 Li-ion battery (LiB) operating under normal and abusive conditions while positioned in horizontal and vertical orientations. In total, three FBG sensors were used to track in real-time the temperature variation of the cathode, middle, and anode of the LiB. Tests for each orientation were performed, where each of them consisted of two cycles: the first one with normal charge/discharge conditions, operating between 2.75 V and 4.20 V, and another in abusive conditions, operating between 2.00 V and 4.95 V. The battery was submitted to constant current charge and discharge steps, with rest intervals between each operation. The results suggest that, in general, the temperature variation while operation in vertical orientation is lower when compared to the horizontal one, mainly in the anode, while the LiB is submitted to the abusive charge procedure, where the temperature variation difference achieved 3.4 ± 0.2 °C. In addition, the FBG sensors were able to track in real-time the temperature variation of three different locations of the battery simultaneously. The temperature variation registered for each sensor is shown and discussed.