A benzene-free and vinyl-free molecule, azulene, is used to polymerize with sulfur through inverse vulcanization. The sulfur radical promoted reaction mechanism has been studied through solid-state NMR experiments combined with DFT calculations. The as produced polymer has high sulfur content and can serve as a cathode material for Li-S batteries with longer lifetime stability compared to pure sulfur, providing a new protocol to develop new cathode materials for Li-S batteries.