Lithium sulfur (Li–S) batteries are considered as promising energy storage systems for the next generation of batteries due to their high theoretical energy densities and low cost. Much effort has been made to improve the practical energy densities and cycling stability of Li–S batteries via diverse designs of materials nanostructure. However, achieving simultaneously good rate capabilities and stable cycling of Li–S batteries is still challenging. Herein, we propose a strategy to utilize a dual effect of metal carbide nanoparticles decorated on carbon nanofibers (MC NPs-CNFs) to realize high rate performance, low hysteresis, and long cycling stability of Li–S batteries in one system. The adsorption experiments of lithium polysulfides (LiPS) to MC NPs and corresponding theoretical calculations demonstrate that LiPS are likely to be adsorbed and diffused on the surface of MC NPs because of their moderate chemical bonding. MC NPs turn out to have also an electrocatalytic role and accelerate electrochemical redox reactions of LiPS, as proven by cyclic voltammetry analysis. The fabricated Li–S batteries based on the W₂C NPs-CNFs hybrid electrodes display not only high specific capacity of 1200 mAh/g at 0.2C but also excellent rate performance and cycling stability, for example, a model setup can be operated at 1C for 500 cycles maintaining a final specific capacity of 605 mAh/g with a degradation rate as low as 0.06%/cycle.

中文翻译：

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低成本金属碳化物纳米晶体作为高性能Li–S电池的结合和电催化位点

锂硫（Li–S）电池由于其较高的理论能量密度和低成本而被认为是下一代电池的有前途的能量存储系统。通过材料纳米结构的多种设计，已经做出了很多努力来提高Li-S电池的实际能量密度和循环稳定性。然而，同时实现良好的速率能力和稳定的Li-S电池循环仍是挑战。本文中，我们提出一种策略，利用装饰在碳纳米纤维（MC NPs-CNFs）上的金属碳化物纳米颗粒的双重作用，在一个系统中实现Li-S电池的高倍率性能，低滞后性和长循环稳定性。LiPS对MC NPs的吸附实验和相应的理论计算表明，由于LiPS具有中等的化学键合作用，因此很可能被MC NPs吸附和扩散。循环伏安法分析证明，MC NP还具有电催化作用，并加速LiPS的电化学氧化还原反应。基于W的Li-S人造电池₂ C NPs-CNFs混合电极不仅在0.2C时显示1200 mAh / g的高比容量，而且还具有出色的速率性能和循环稳定性，例如，模型设置可在1C下操作500个循环，保持最终比容量为605 mAh / g，降解率低至0.06％/循环。