Synthesis\nof Highly Cyclized Polyacrylonitrile via\nLiquid-Phase Cyclization for Advanced Cathode Materials

Sulfurized\npolyacrylonitrile (SPAN) based on a solid–solid\nreaction has attracted wide attention due to its advantages of no\nshuttle effect. However, the solid-state polyacrylonitrile raw material\nis used during the preparation of SPAN and results in a low vulcanization\nefficiency. Meanwhile, a series of side reactions such as the formation\nof cyclic polyamines and conjugated polyenes, cross-linking side reactions,\nand polymer degradation prevent an ideal trapezoidal conjugated main-chain\nstructure. In this work, a liquid-phase cyclization method is proposed\nto prepare SPAN materials (SPAN-L). The reaction temperature is significantly\nlowered by leveraging the high reactivity characteristics under liquid-phase\nconditions, thereby inhibiting a series of side reactions caused by\nhigh temperature and improving the structural regularity of SPAN.\nThe SPAN-L cathode has good structural regularity and a uniform sulfur\ndistribution, which contribute to its enhanced electrical conductivity\nand high sulfur utilization ratio. Additionally, ex situ Raman and\nXPS analyses reveal stable C–S bonds in SPAN-L during cycling,\nindicating enhanced electrode stability. This study synthesizes SPAN\ncathode materials with enhanced performance by adjusting the reaction\nenvironment, showing better electronic conductivity, sulfur utilization,\nand cycle stability than the solid-phase methods.