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A new family of sulfur-rich phosphorus sulfide molecules (P S ) and their electrochemical reaction mechanism with metallic Li has been explored. These P S molecules are synthesized by the reaction between P S and S. For Li batteries, the P S molecule in the series of P S molecules provides the highest capacity, which has a first discharge capacity of 1223 mAh g at 100 mA g and stabilizes at approximately 720 mAh g at 500 mA g after 100 cycles. This new class of sulfur-rich P S molecules and its electrochemical behavior for room-temperature Li storage could provide novel insights for phosphorus sulfide molecules and high-energy batteries.

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energy density (2600 Wh kg −1 ) and theoretical capacity (1675 mAh g −1 ). [1][2][3][4][5] Nevertheless, the sluggish reaction kinetics and notorious lithium polysulfide (LiPS) shuttling have markedly hindered its commercialization. [6][7][8][9][10][11] In the past decade, metal-based electrocatalysts, encompassing various compounds and alloys, have been widely explored as the LiPSs regulator in Li-S realm. [12][13][14] Despite their favorable regulation over the adsorptiondiffusion-conversion of LiPSs to a certain extent, the introduction of excessive metals would curtail the energy density of the entire cell, thereby handicapping practical applications. [15] In this sense, singleatomic catalyst (SAC) has a much smaller mass than that of traditional metal-based electrocatalysts, when using SACs (even with an elevated metal content of 10 wt%), the catalyst weight ratio in an entire sulfur electrode would still be quite tiny. SAC as an efficient sulfur redox mediator is hence expected to realize high-energydensity Li-S batteries. Recently, SACs supported on conductive carbon skeletons have attracted growing attention because of their unique size effect, maximized atom availability, and impressive catalytic activity. [16][17][18][19] These features have readily enabled them to promote dual-directional sulfurThe 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 C 3 N 4 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.