Well-dispersed sulfur wrapped in reduced graphene oxide nanoscroll as cathode material for lithium–sulfur battery

Abstract

For large scale batteries, sulfur is an attractive cathode active material for lithium batteries because of high theoretical capacity of 1675mAhg−1. However, severe capacity fading and low conductivity of sulfur are significant challenges for its practical application. Here, we report a facile approach to prepare reduced graphene oxide nanoscroll embedded with well-dispersed sulfur (S/GNSC) through a one-pot oxidation of sulfide and reduction of graphene oxide followed by freeze-casting process to generate graphene nanoscroll. The S/GNSC takes the novel shape of reduced graphene oxide sheet spirally wrapped into one-dimensional tubular structure, which enhances electrochemical performance by acting as physical barrier to prevent polysulfide from dissolving and an effective network to promote electron and Li+ transport during reaction. Therefore, the S/GNSC composite with high sulfur loading of 76wt% exhibits high initial capacity of 1295mAhg−1 and reversible capacity of 744mAhg−1 after the 100th cycle at 0.2C when it is used as a cathode material for lithium-sulfur battery, while the capacity of sulfur loaded on reduced graphene oxide sheet (S/rGO) is continuously fading to 510mAhg−1 after the 100th cycle due to the irreversible loss of polysulfide.