Bifunctional carbon nanofibrous interlayer embedded with cobalt single atoms for polysulfides trapping and catalysis in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are in the spotlight as one of the most promising energy storage systems, specifically suitable for electric vehicles and intelligent electronic devices. However, Li-S batteries still suffer from the shuttle effect of intermediate polysulfides, inducing the loss of active materials and slow redox reaction kinetics. Herein, a freestanding functional nanofibrous membrane with cobalt single atoms supported by porous carbon nanofiber skeletons is fabricated using a one-step carbonization process. The flexible nanofiber structure can provide the characteristics of good conductivity and lightweight, helping the polysulfides trapped in the porous structure of the fibrous skeleton. Moreover, the results of electrocatalytic characterization and theoretical calculation demonstrate the existence of the metal coordinate center Co-N-x sites, and their functions of reducing polarization voltage and accelerating polysulfide conversion. Using this functional nanofiber membrane as an interlayer with the Co-N-x coordination structure (Co@N-PCNFs), the assembled Li-S batteries exhibit a high initial specific capacity (1522 mAh.g(-1) at 0.1C) and outstanding rate performance (905 mAh.g(-1) at 2C). Especially, the specific capacity of the Li-S batteries can achieve 786 mAh.g(-1) at 0.5C with a sulfur loading of 4 mg.cm(-2) after 100 cycles. This effective method of fabricating nanofibrous interlayers can effectively promote the development of advanced Li-S batteries and the application of electrospun materials in energy storage fields.