Unveiling the polysulfide-PPY interaction for enhanced lithium–sulfur battery performance

Understanding the processes in lithium-sulfur (Li-S) batteries is critical to advancing this promising energy storage technology. To this end, a 3D polypyrrole-based sponge (PPY) was synthesized as a sulfur host for positive electrodes in (Li-S). Through optimization, the PPY:S8 composite showed interesting electrochemical performance, including a cycle lifetime of over 200 cycles and remarkable specific capacitances at 0.2 A g−1. Electrochemical impedance spectroscopy (EIS) data provided valuable insights. In addition to the unchanged solution resistance indicating a minimal shuttle effect, the capacitance of the PPY film remains robust due to its bipolaronic state and shows strong sulfur retention, especially at the LiPSs/S8 potential. Operando Raman spectroscopy revealed the stability of the bipolaronic state and the “neutralization” of the lithium polysulfides (LiPSs) by the incorporation of sulfur. Moreover, UV-Vis analysis confirmed the efficient absorption of LiPS within the PPY matrix. These results highlight the potential of PPY as an effective sulfur host that minimizes the shuttle effect and improves the charge storage capability of Li-S batteries. This research contributes to the development of advanced materials for energy storage systems and highlights the importance of using positively charged materials as carriers for sulfur in Li-S batteries.