Promoting performance of lithium–sulfur battery via in situ sulfur reduced graphite oxide coating

Activated graphene/sulfur structure sheathed in a flexible graphene layer is presented as the cathode material of lithium–sulfur battery. The surface coating graphite oxide sheets are reduced by a one-step in situ sulfur reduction method under vacuum at 600 °C without any additional reductant. The high reduction degree of in situ sulfur reduced graphite oxide (RGO) coating layer will facilitate the rapid charge transfer at high current rate. The flexible encapsulated RGO structure will retard the diffusion of polysulfides and adjust the volume change of sulfur in cycling. As a result, the electrochemical evaluation of the RGO–activated graphene (AG)/S electrode demonstrates superior capacity, cycling and rate performance. The RGO–AG/S electrode with 60 wt% sulfur loading achieves a stable cyclability over 2000 galvanostatic charge/discharge process (capacity-fade rate of only 0.03% per cycle at 1600 mA·g⁻¹). The average Coulombic efficiency remains at ~ 96% with no electrolyte additives (such as LiNO₃). The outstanding property of RGO–AG/S electrode is attributed to the distinctive in situ sulfur RGO-coated hierarchical texture.