MOF derived in-situ carbon-encapsulated Fe3O4@C to mediate polysulfides redox for ultrastable Lithium-sulfur batteries

In view of the low sulfur utilization and poor cycle stability of lithium-sulfur (Li-S) batteries, an effective strategy is widely used by introducing strong polar materials into the sulfur host. Herein, metal organic frameworks (MOFs) derived in-situ carbon encapsulated transition metal oxides (Fe3O4@C) is proposed to mediate the polysulfides redox reaction, based on rapid charge transfer behavior, strong interaction with the intermediates of sulfur reduction and high electrochemical activation for polysulfides transformation. As expected, together with the hierarchical porous structure inheriting from the MIL-53 template, the Fe3O4@C incorporated in the sulfur cathode contributes to the apparently enhanced specific capacity, improved rate performance as well as super high cycling stability (extremely low capacity fading of 0.002% per cycle over 300 cycles at 1 C). This work provides a concise yet effective strategy to design a sulfur cathode for application of Li-S batteries with high rate performance and super high cycling stability.

鉴于锂硫（Li - S）电池存在硫利用率低和循环稳定性差的问题，一种有效的策略是通过在硫主体中引入强极性材料而被广泛应用。在此，提出了原位碳包覆过渡金属氧化物（Fe₃O₄@C）衍生的金属有机框架（MOFs）来调节多硫化物的氧化还原反应，这是基于其快速的电荷转移行为、与硫还原中间体的强相互作用以及对多硫化物转化的高电化学活性。正如预期的那样，结合从MIL - 53模板继承的分级多孔结构，掺入硫正极中的Fe₃O₄@C有助于显著提高比容量、改善倍率性能以及超高的循环稳定性（在1C下循环300次，每次循环的容量衰减极低，为0.002%）。这项工作为设计用于锂硫电池的具有高倍率性能和超高循环稳定性的硫正极提供了一种简洁而有效的策略。