Graphene and its derivatives in lithium-sulfur batteries

On the edge of impending energy and environmental crisis, electrochemical energy storage has rapidly gained momentum. Among all the candidates in the beyond lithium-ion battery arena, lithium-sulfur (Li-S) battery has attracted extensive attention due to its ultrahigh theoretical capacity and the abundance of sulfur. However, the development of Li-S battery is hindered by its quick capacity decay and short lifespan because of the insulating nature of sulfur/Li2S and the high solubility of lithium polysulfides. Under this scenario, graphene and its derivatives have been explored to overcome the shortcomings of Li-S batteries. Graphene is mechanically robust, highly flexible, and exceptionally conductive, enabling abundant porosity for high sulfur loading, expeditious electron/ion transfer, and effective polysulfide encapsulation. Graphene oxide (GO), on the other hand, is often attached with various functional groups which are able to chemically bond with polysulfides, rendering GO a strong polysulfide entrapping ability. The graphene/GO enabled physical confinements and chemical interactions can be further enhanced via constructing graphene-sulfur configurations and doping functional groups or heteroatoms. In addition to the intrinsic advantages, graphene and GO are highly compatible with many engineering materials, making graphene-based composite electrodes promising for low-cost, high-performance Li-S batteries. This review article sequentially illustrates the interaction between sulfur/polysulfides and graphene, sulfur infiltration methods, sulfur/graphene configurations, applications of graphene and its derivatives in Li-S batteries, and presents state of the art and future outlook. (C) 2018 Elsevier Ltd. All rights reserved.