New insights into the reaction mechanism of sulfurized polyacrylonitrile cathode material for Li-S batteries

Sulfurized polyacrylonitrile (SPAN) is a prospective cathode candidate for Li-S batteries due to capable of solving polysulfides dissolution and shuttle effect and presenting stable electrochemical performance. Despite the extensive research conducted on the synthetic conditions and pathways for SPAN modification, details of the molecular structure of SPAN and electrochemical reaction mechanism of SPAN electrode remain controversial. Herein, the formation of conjugate aromatic radical and new C-S bond during discharge process is proposed for the first time. During charge process, the S atom prioritize to combine with C radical on the aromatic ring, resulting in avoiding the generation of polysulfides over long cycles, which potentially account for the remarkable cycling stability observed in the SPAN cathode. This study offers novel insights into the underlying reaction mechanisms, thereby providing valuable guidance for further development of sulfurized cathode materials applied in advanced Li-S battery.