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The booming development of electric vehicles and mobile electronic devices has placed increasing demands on high-energy-density secondary batteries. [1] Li-S batteries afford a theoretical energy density of 2600 Wh kg À1 and are promising candidates as next-generation high-energy-density energy storage devices. [2] Typical Li-S batteries employ a sulfur cathode, a Li metal anode, and ether-based electrolyte. Multiphase and multielectron sulfur redox reactions take place at the sulfur cathode during charge and discharge. [3] Specifically, during the discharge process, solid sulfur is first reduced to lithium polysulfides (LiPSs) through solid-liquid conversion, then LiPSs undergo liquid-liquid reduction reactions in the electrolyte, and eventually liquid-solid conversion occurs to form Li 2 S 2 /Li 2 S precipitates from LiPS reduction. [4] The cathode sulfur redox reactions provide a high specific capacity of 1672 mAh g À1 that greatly exceeds the intercalation cathodes of Li-ion batteries and promises a high energy density of Li-S batteries. However, the sluggish kinetics of sulfur redox reactions leads to low utilization of active materials and severe polarization, which consequently result in low discharge capacity and poor rate performance of Li-S batteries and severely limit the practical implementation of Li-S batteries. [5] Therefore, facilitating the sulfur redox kinetics is essential for the construction of highperformance Li-S batteries.Introducing electrocatalysts is regarded as a promising solution to promote the sluggish sulfur redox kinetics. [6] Previous works have established that electrocatalysts such as metal oxides, [7] nitrides, [8] sulfides, [9] and carbides [10] can accelerate the sulfur redox kinetics and improve the performance of Li-S batteries. Among the various electrocatalysts, single-atom catalysts (SACs) are able to make efficient use of almost every transition metal atom as active site and the unsaturated coordinated transition metal atoms are more likely to interact with the active species over traditional catalyst particles. [11] As a result, Cobased, [12] Fe-based, [13] Ni-based, [14] and Mn-based [15] SACs have been massively reported as electrocatalysts for Li-S batteries to accelerate the sulfur redox kinetics. For example, Du et al. reported that atomic Co embedded in nitrogen-doped graphene could trigger the surface-mediated reaction and reduce the activation energy for the conversion from Li 2 S 4 to Li 2 S 2 /Li 2 S. [16] Ye et al. reported Fe-N and Co-N co-doped SACs that could catalyze the conversion reactions for both long-chain and short-chain LiPSs.

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