Modelling thermal behavior of carbon-sulphur composite cathode in lithium-sulphur batteries

Lithium sulphur (Li-S) batteries are strong candidates for advanced energy storage systems, but their practical application is limited by the poor conductivity and complex reaction pathways of the sulphur cathode. This study presents a thermal model of the sulphur cathode of a Li-S battery, incorporating a resistance model that explicitly relates composite resistivity to the carbon-to-sulphur (C/S) ratio. An equivalent C/S-ratio-dependent resistivity model for carbon-coated sulphur is developed based on experimental resistivity measurements at different C/S ratios. The model predicts dynamic resistivity, heat generation, and temperature during charge-discharge cycling and evaluates the impact of varying C/S ratios, charging rates, and cycling on thermal and electrochemical behavior of Li-S cells. The results indicate that a lower C/S ratio increases composite resistivity, resulting in greater heat accumulation and a corresponding rise in cell temperature. While a higher C/S ratio improves thermal response, it compromises the sulphur loading, leading to reduced cell capacity. At a C/S ratio of 0.8372, the sulphur loading and cell capacity at 1C, with the given cell dimension, were found to be 2.7 g and 1053.91 mAh/g of sulphur. At the same C/S ratio, the maximum heat generation and temperature were observed at 4C, which were 13.85 MW/m 3 and 315.6 K, respectively.