Advances of graphene-based aerogels and their modifications in lithium-sulfur batteries

Lithium-sulfur (Li–S) batteries are the current focus of attention as candidates for next-generation energy storage systems due to their high energy density, low cost and environmental friendliness. However, their commercialization is hampered by various issues, including poor electrical conductivity of sulfur and its reduction products, low utilization of active material, limited sulfur loading and severe lithium polysulfides (LiPSs) shuttling effect. To solve these problems, various 0D, 1D and 2D nanostructured carbon materials with developed surface morphology, electrochemical stability and electrical conductivity have been examined for immobilizing sulfur, mitigating its volume variation and enhancing its electrochemical kinetics. Here we review the recent progress in design and fabrication of carbon-based sulfur hosts, free-standing cathodes, interlayers and functional separators for Li–S batteries using 3D graphene networks presented by graphene aerogels (GAs). The main characteristics of GAs and their synthesis routes are overviewed first. Further, the fabrication of both conventional slurry-casted cathodes and binder and current collector-free self-supporting sulfur composite cathodes based on pure and modified GAs acting as highly porous matrix for sulfur are discussed. In-depth analysis of the mechanisms of electrochemical reactions depending on the modifier type are provided. The advances of modified GAs in the design and preparation of interlayers and functional separators for Li–S batteries are deliberated as well. Finally, the conclusion and perspectives for future development of 3D nanostructured carbons for Li–S battery technology are offered.