Graphene–Pure Sulfur Sandwich Structure for Ultrafast, Long-Life Lithium-Sulfur Batteries

Lithium-sulfur (Li–S) batteries have high specific capacities and are considered as next-generation batteries for large-scale energy storage and electric vehicles. However, rapid capacity fade and low sulfur utilisation inhibit their use. We designed a unique sandwich structure with pure sulfur between two graphene membranes, which are continuously produced over a large area, as a very simple but effective approach for the fabrication of Li–S batteries with ultrafast charge/discharge rates and long-life. One membrane was used as a graphene current collector (GCC) to replace the conventional aluminium foil current collector, and sulfur was coated onto this membrane as the active material. The other membrane was coated onto a conventional polymer separator (G-separator). This electrode showed a high specific capacity of 1340 mA h g−1 at 300 mA g−1, a Coulombic efficiency approaching 100%, excellent high-rate performance and long cyclic stability. The GCC and G-separator not only effectively reduce the internal resistance of the sulfur cathode but also function as buffer layers to trap/immobilise and reuse the dissolved lithium polysulfides. Furthermore, for the first time, three-dimensional X-ray microtomography was used to investigate sulfur diffusion during electrochemical charge/discharge.