Here, we provide a deeper insight into the state of sulfur confined in ultramicroporous carbon (UMC) and clarify its electrochemical reaction mechanism with lithium by corroborating the results obtained using various experimental techniques, such as X-ray photoelectron spectroscopy, electron energy loss spectroscopy, in situ Raman spectroscopy, and in situ electrochemical impedance spectroscopy. In combination, these results indicate that sulfur in UMC exists as linear polymeric sulfur rather than smaller allotropes. The electrochemical reactivity of lithium with sulfur confined in UMC (pore size ≤0.7 nm) is different from that of sulfur confined in microporous carbon (≤2 nm, or ultramicroporous carbon containing significant amount of micropores) and mesoporous carbon (>2 nm). The observed quasi-solid-state reaction of lithium with sulfur in UMC with a single voltage plateau during the discharge/charge process is due to the effective separation of solvent molecules from the active material. The size of carbon pores plays a vital role in determining the reaction path of lithium with sulfur confined in UMC.

中文翻译：

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洞悉超微孔碳中的硫

在这里，我们通过证实使用各种实验技术（例如X射线光电子能谱，电子能量损失能谱，原位拉曼光谱和原位电化学阻抗谱。综合起来，这些结果表明，UMC中的硫以线性聚合硫的形式存在，而不是较小的同素异形体。锂与限制在UMC中（孔径≤0.7 nm）的硫的电化学反应性与限制在微孔碳（≤2 nm，或含有大量微孔的超微孔碳）和中孔碳（> 2 nm）中的硫的电化学反应性不同。在UMC中，在放电/充电过程中观察到的锂与硫的准固态反应是在一个单一的电压平台上进行的，这是由于溶剂分子与活性材料的有效分离所致。碳孔的大小在决定锂与UMC中封闭的硫的反应路径中起着至关重要的作用。