A sulfur-polyacrylonitrile/graphene composite cathode for lithium batteries with excellent cyclability

A sulfur-polyacrylonitrile/reduced graphene oxide (SPAN/RGO) composite with unique electrochemical properties is prepared via deposition of PAN on the surface of RGO sheets followed by ball milling with sulfur and heat treatment. Infrared spectroscopy and microscopy studies indicate that the composite consists of RGO decorated by SPAN particles of 100 nm average size. The SPAN/RGO composite shows good overall electrochemical performance when used in Li-S batteries. It exhibits ∼85% retention of the initial reversible capacity of 1467 mAh g−1 over 100 cycles at a constant current rate of 0.1C and retains 1100 mAh g−1 after 200 cycles. In addition, the composite displays excellent Coulombic efficiency and rate capability, delivering up to 828 mAh g−1 reversible capacity at 2C. The improved performance stems from the composition and structure of the composite, wherein RGO renders a robust electron transport framework and PAN matrix help suppresses the shuttle effect by absorbing sulfur/polysulfides.