Unveiling the Thermal Behavior of SnS2 Anodes Across Delithiation Stages

This study investigates the thermal behavior of SnS2 anodes for lithium-ion batteries at seven different states of charge (fully discharged (lithiated) at 0 mAh/g, partially charged at 100, 200, 300, 400, and 500 mAh/g, and fully charged (delithiated) at 550 mAh/g) using differential scanning calorimetry (DSC). To better understand the observed thermal behavior, complementary XRD and XPS analyses were performed. Generally, in all electrodes, the thermal decomposition of the electrode material is initiated by the exothermic decomposition of the SEI followed by a binder decomposition reaction around 265 °C. Interestingly, with increased states of delithiation from 400 mAh/g, endothermic peaks in the heat-flow signal of the DSC measurements are observed, which can be correlated with the structural and compositional changes in the electrode material as determined by XRD and XPS, respectively. These analyses confirmed the progressive formation of metallic tin on advanced delithiation. Additionally, the total heat generation from the electrodes decreased with increased delithiation. The results of this study serve as the basis for better understanding the thermal decomposition of SnS2-based anodes, which are considered promising for advanced lithium-ion battery chemistries.