Plasma Treatment for Nitrogen-Doped 3D Graphene Framework by a Conductive Matrix with Sulfur for High-Performance Li-S Batteries

Carbon materials have received considerable attention as host cathode materials for sulfur in lithium-sulfur batteries; N-doped carbon materials show particularly high electrocatalytic activity. Efforts are made to synthesize N-doped carbon materials by introducing nitrogen-rich sources followed by sintering or hydrothermal processes. In the present work, an in situ hollow cathode discharge plasma treatment method is used to prepare 3D porous frameworks based on N-doped graphene as a potential conductive matrix material. The resulting N-doped graphene is used to prepare a 3D porous framework with a S content of 90 wt% as a cathode in lithium-sulfur cells, which delivers a specific discharge capacity of 1186 mAh g(-1) at 0.1 C, a coulombic efficiency of 96% after 200 cycles, and a capacity retention of 578 mAh g(-1) at 1.0 C after 1000 cycles. The performance is attributed to the flexible 3D structure and clustering of pyridinic N-dopants in graphene. The N-doped graphene shows high electrochemical performance and the flexible 3D porous stable structure accommodates the considerable volume change of the active material during lithium insertion and extraction processes, improving the long-term electrochemical performance.