Because of their high theoretical energy density and low cost, lithium-sulfur (Li-S) batteries are promising next-generation energy storage devices. The electrochemical performance of Li-S batteries largely depends on the efficient reversible conversion of Li polysulfides to Li2S in discharge and to elemental S during charging. Here, we report on our discovery that monodisperse cobalt atoms embedded in nitrogen-doped graphene (Co-N/G) can trigger the surface-mediated reaction of Li polysulfides. Using a combination of operando X-ray absorption spectroscopy and first-principles calculation, we reveal that the Co-N-C coordination center serves as a bifunctional electrocatalyst to facilitate both the formation and the decomposition of Li2S in discharge and charge processes, respectively. The S@Co-N/G composite, with a high S mass ratio of 90 wt %, can deliver a gravimetric capacity of 1210 mAh g-1, and it exhibits an areal capacity of 5.1 mAh cm-2 with capacity fading rate of 0.029% per cycle over 100 cycles at 0.2 C at S loading of 6.0 mg cm-2 on the electrode disk.

中文翻译：

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氮掺杂石墨烯中的钴作为高硫含量锂硫电池的单原子催化剂

由于理论能量密度高、成本低，锂硫（Li-S）电池是有前途的下一代储能装置。Li-S 电池的电化学性能很大程度上取决于多硫化锂在放电时向 Li2S 和充电时向元素 S 的有效可逆转化。在这里，我们报告了我们的发现，即嵌入氮掺杂石墨烯（Co-N/G）中的单分散钴原子可以触发多硫化锂的表面介导反应。结合操作 X 射线吸收光谱和第一性原理计算，我们揭示了 Co-NC 配位中心作为双功能电催化剂，分别促进了 Li2S 在放电和充电过程中的形成和分解。S@Co-N/G 复合材料，具有 90 wt% 的高 S 质量比，