The high-energy-density lithium-sulfur (Li-S) batteries (2600 Wh kg) are seriously hampered by the slow redox reaction kinetics and obnoxious shuttle effects of sulfur cathode. Introducing a catalytic host to promote sulfur redox kinetics is a promising way to inhibit polysulfide shuttling. Previous studies mainly focus on the unidirectional catalysis conversion from S to LiS, and usually ignore the inverse reaction. Herein, defective vanadium nitride (VN) is designed to promote the conversion of sulfur. The catalytic analysis suggests that introducing nitrogen vacancies effectively improves the nucleation and decomposition kinetics of LiS, and prefers to promote the nucleation process, leading to superior capacity. Benefit from the bidirectional enhanced sulfur redox kinetics, the VN/S composite electrode presents an impressively high capacity of 1417 mAh g at 0.1 C at the first charge/discharge process, which is very close to the theoretical capacity of sulfur cathode (1675 mAh g). The Coulombic efficiency of the composite electrode reaches 99.89% even after 1000 cycles, showing reversible redox reactions. The pouch cell using VN/S cathode shows a high initial discharge capacity (1180.3 mAh g) and can stably cycle over 100 cycles. This work can support the development of bidirectional catalytic host design for high-loading Li-S batteries.

中文翻译：

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通过氮空位增强的双向催化改善硫阴极的氧化还原动力学

高能量密度锂硫（Li-S）电池（2600 Wh kg）受到硫阴极缓慢的氧化还原反应动力学和令人讨厌的穿梭效应的严重阻碍。引入催化主体来促进硫氧化还原动力学是抑制多硫化物穿梭的一种有前途的方法。以往的研究主要集中在S到LiS的单向催化转化上，通常忽略逆反应。在此，有缺陷的氮化钒（VN）被设计来促进硫的转化。催化分析表明，引入氮空位可以有效改善LiS的成核和分解动力学，并有利于促进成核过程，从而获得优异的容量。得益于双向增强的硫氧化还原动力学，VN/S复合电极在0.1 C下的首次充放电过程中呈现出令人印象深刻的高容量1417 mAh g，这非常接近硫正极的理论容量（1675 mAh g） ）。即使经过1000次循环，复合电极的库仑效率仍达到99.89%，表现出可逆的氧化还原反应。使用VN/S正极的软包电池表现出较高的初始放电容量（1180.3 mAh g），并且可以稳定循环超过100次。这项工作可以支持高负载锂硫电池双向催化主体设计的开发。