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 C3N4 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. An Fe–N2 single‐atomic catalyst accommodated by a biomorphic hierarchical C3N4 support from a biomass template readily boosts the dual‐directional conversion kinetics of lithium sulfide and realizes high‐performance Li−S batteries.