Enhanced electrochemical performance of a crosslinked polyaniline-coated graphene oxide-sulfur composite for rechargeable lithium-sulfur batteries

Due to the extraordinarily high theoretical capacity of sulfur (1675 mAh g−1), the lithium-sulfur (Li-S) battery has been considered a promising candidate for future high-energy battery applications. Li-S batteries, however, have suffered from limited cycle lives, mainly due to the formation of soluble polysulfides, which prevent the practical application of this attractive technology. The encapsulation of sulfur with various conductive materials has addressed this issue to some extent. Nevertheless, most approaches still present partial encapsulation of sulfur and moreover require a large quantity of conductive material (typically, >30 wt%), making the use of sulfur less desirable from the viewpoint of capacity. Here, we address these chronic issues of Li-S cells by developing a graphene oxide-sulfur composite with a thin crosslinked polyaniline (PANI) layer. Graphene oxide nanosheets with large surface area, high conductivity and a uniform conductive PANI layer, which are synthesized by a layer-by-layer method, have a synergetic interaction with a large portion of the sulfur in the active material. Furthermore, a simple crosslinking process efficiently prevents polysulfide dissolution, resulting in unprecedented electrochemical performance, even with a high sulfur content (∼75%): a high capacity retention of ∼80% is observed, in addition to 97.53% of the average Coulombic efficiency being retained after 500 cycles. The performance we demonstrate represents an advance in the field of lithium-sulfur batteries for applications such as power tools.