Facile and low-cost preparation of Co and N co-doped hierarchical porous carbon as a functional separator for Li-S batteries

Despite their ultrahigh theoretical capacity, the practical application of lithium-sulfur batteries (LiSBs) is still severely hindered by the shuttle effect of lithium polysulfides. Herein, we develop a Co and N co-doped carbon (CoN-CNT/HPC) as a modifying separator material to suppress this shuttle effect. The production of the material is low-cost and can be easily scaled up. The as-prepared CoN-CNT/HPC has a hybrid structure consisting of carbon nanotube (CNT) and hierarchical porous carbon sheet (HPC). This structure not only provides efficient pathways for charge transport but also encourages physical adsorption of polysulfides during the lithiation process. Additionally, the Co and N co-doping promotes the chemical adsorption of polysulfides and catalyzes polysulfide conversion. When used as a separator layer in Li-S batteries, CoN-CNT/HPC delivers excellent cycling stability with a low decay rate of 0.04% per cycle over 500 cycles at 2C. Even at high area sulfur loading of 5.5 mg/cm2, the cell using CoN-CNT/HPC separator still exhibits a high initial capacity of 646 mAh/g at 0.5 C and an outstanding cycling stability (561 mAh/g after 100 cycles). The present work provides a simple and effective design strategy of separator materials for high performance Li-S batteries.