Enhanced Dual‐Directional Sulfur Redox via a Biotemplated Single‐Atomic Fe–N2 Mediator Promises Durable Li–S Batteries

The lithium-sulfur (Li-S) battery is considered as an appealing candidate for next-generation electrochemical energy storage systems because of high energy and low cost. Nonetheless, its development is plagued by the severe polysulfide shuttling and sluggish reaction kinetics. Although single-atom catalysts (SACs) have emerged as a promising remedy to expedite sulfur redox chemistry, the mediocre single-atom loading, inferior atomic utilization, and elusive catalytic pathway handicap their practical application. To tackle these concerns, in this work, unsaturated Fe single atoms with high loading capacity (≈6.32 wt%) are crafted on a 3D hierarchical C3 N4 architecture (3DFeSA-CN) by means of biotemplated synthesis. By electrokinetic analysis and theoretical calculations, it is uncovered that the 3DFeSA-CN harnesses robust electrocatalytic activity to boost dual-directional sulfur redox. As a result, S@3DFeSA-CN can maintain a durable cyclic performance with a negligible capacity decay rate of 0.031% per cycle over 2000 cycles at 1.0 C. More encouragingly, an assembled Li-S battery with a sulfur loading of 5.75 mg cm-2 can harvest a high areal capacity of 6.18 mAh cm-2 . This work offers a promising solution to optimize the carbonaceous support and coordination environment of SACs, thereby ultimately elevating dual-directional sulfur redox in pragmatic Li-S batteries.