Self-templating synthesis of prismatic-like N-doped carbon tubes embedded with Fe3O4 as a high-efficiency polysulfide-anchoring-conversion mediator for high performance lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries are promising the next generation energy storage system due to their high energy density of ~2600 Wh kg−1. However, the shuttling and sluggish reaction kinetics of the polysulfides severely hinders the development of Li-S batteries. To overcome these issues, a prismatic-like N-doped carbon tubes embedded with Fe3O4 nanoparticles (Fe3O4-PNCT) as an efficient sulfur host for advanced Li-S batteries is rationally designed and prepared by a self-templating method in this work. With the high conductivity and hollow structure, the Fe3O4-PNCT can effectively accelerate electron and ion transfer rate, relieve volume expansion and anchor polysulfides intermediates. More importantly, polar Fe3O4 as electrocatalysts uniformly distributed embedding in hollow N-doped carbon shell can not only efficiently adsorb polysulfides on the conductive sulfur host surface, but also significantly promote catalyze transformation of polysulfides, which has been actually revealed by experiments and DFT results. Benefiting from these merits, the sulfur cathode with Fe3O4-PNCT delivers excellent electrochemical performances including high sulfur utilization (1375 mAh g−1 at 0.1C), superior rate performance (685 mAh g−1 at 5C) and remarkable cycling stability up to 1000 cycles at 5C with a super low capacity-fade rate of 0.03% per cycle. This work illustrates the importance of desired design and anchoring-conversion in sulfur electrode, offering some lights on the construction of multifunctional sulfur hosts for high-performance Li-S batteries.