Bio-derived N-doped porous carbon as sulfur hosts for high performance lithium sulfur batteries

Abstract

Shuttle effect, poor conductivity and large volume expansion are the main factors that hinder the practical application of sulfur cathodes. Currently, rational structure designing of carbon-based sulfur hosts is the most effective strategy to address the above issues. However, the preparation process of carbon-based sulfur hosts is usually complex and costly. Therefore, it is necessary to develop an efficient and cost-effective method to fabricate carbon hosts for high-performance sulfur cathodes. Herein, we reported the fabrication of a bio-derived nitrogen doped porous carbon materials (BNPC) via a molten-salt method for high performance sulfur cathodes. The long-range-ordered honeycomb structure of BNPC is favorable for the trapping of polysulfide (PS) species and accommodates the volumetric variation of sulfur during cycling, while the high graphitization degree of BNPC favors the redox kinetics of sulfur cathodes. Moreover, the nitrogen doping content not only enhances the electrical conductivity of BNPC, but also provides ample anchoring sites for the immobilization of PS, which plays a key role in suppressing the shuttle effect. As a result, the S@BNPC cathode exhibits a high initial specific capacity of 1189.4 mA·h/g at 0.2C. After 300 cycles, S@BNPC still maintains a capacity of 703.2 mA·h/g which corresponds to a fading rate of 0.13% per cycle after the second cycle. This work offers vast opportunities for the large-scale application of high performance carbon-based sulfur hosts.