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 1675 mA h g-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 oxid 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 76 wt% exhibits high initial capacity of 1295 mA h g-1 and reversible capacity of 744 mA h g-1 after the 100th cycle at 0.2 C 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 510 mA h g-1 after the 100th cycle due to the irreversible loss of polysulfide.