Graphene-Enveloped Poly(N-vinylcarbazole)/Sulfur Composites with Improved Performances for Lithium-Sulfur Batteries by A Simple Vibrating-Emulsification Method.

We prepared the Poly(N-vinylcarbazole)/sulfur@reduced graphene oxide (PVK/S@RGO) composites via a facile vibrating-emulsification synthesis method, which consist of the composites cores of large sulfur particles integrated into PVK conductive network and the conducting shell of reduced graphene oxide sheets. The PVK in the composites plays multiple roles in different processes. In preparation processes, PVK functions as dispersants to prevent sulfur particles from aggregating into excessively large size. And in the cycling test, PVK could play as additional electroactive binders and barriers to reinforce the electrode stability, accommodate volume change and reduce polysulfides shuttling. The resulting PVK/S@RGO composites containing 71 wt % sulfur exhibit excellent cycling performance and rate properties with a high discharge capacity of 843.5 mA h g(-1) and a charge capacity retention of 77% (only 0.07% capacity degradation per cycle) from 20th to 400th at 1 C, corresponding to an average Coulombic efficiency of over 94%.