Investigation of the Effect of Temperature on Lithium‐Sulfur Cell Cycle Life Performance Using System Identification and X‐Ray Tomography

In this study, cycle life performance of a prototype lithium‐sulfur (Li−S) pouch cell is investigated using system identification and X‐ray tomography methods. Li−S cells are subjected to characterization and ageing tests while kept inside a controlled‐temperature chamber. After completing the experimental tests, two analytical approaches are used: i) The parameter variations of an equivalent‐circuit model due to ageing are determined using a system identification technique. ii) Physical changes of the aged Li−S cells are analyzed using X‐ray tomography. The results demonstrate that Li−S cell's degradation is significantly affected by temperature. Comparing to 10 °C, Li−S cell capacity fade happens 1.4 times faster at 20 °C whereas this number increases to 3.3 at 30 °C. In addition, X‐ray results show a significant swelling when temperature rises from 10 to 20 °C, correspondingly the gas volume increases from 13 to 62 mm3. The effect of temperature on lithium‐sulfur cell cycle life performance is investigated by performing characterization and ageing tests on 19 Ah pouch cells. Firstly, the parameter variations of an equivalent‐circuit model due to ageing are calculated using a system identification technique. Secondly, the physical changes of the cells due to cycling at different temperatures are analyzed using X‐ray tomography. The results demonstrate that lithium‐sulfur cell's performance and cycle life are significantly affected by temperature variation.