Since 2009, lithium-sulfur (Li-S) batteries have been attracting much research interest, ascribed to their high energy density and cost-effectiveness. However, their S cathodes are harassed by the poor conductivity, shuttling of lithium polysulfides (LPSs), and large volume change. In improving conductivity of S cathodes, carbon materials are widely used as conductive additives. However, there still lacks a comparative study on their geometric and structural effects in Li-S batteries. To this end, a systematic investigation is conducted on two different typical conductive additives, carbon black (CB)¹ and nitrogen-doped graphene nanosheets (N-GNS)². This work reveals that, compared to the zero-dimensional (0D) CB nanoparticles, the two-dimensional (2D) N-GNS is structurally less defective and has a larger surface area. As a result, the 2D structure of the N-GNS helps achieve higher capacity retention but inhibits Li-ion transportation. In comparison, the 0D structure of the CB facilitates the transportation of Li-ions with a higher initial capacity but exposed to a severer shuttling behavior of LPSs. It is also found that a combination of the CB and N-GNS enables better performance of Li-S batteries, in terms of sustainable capacity, Coulombic efficiency, and rate capability. This study is inspiring for designing better S cathodes for Li-S batteries.

自2009年以来，锂硫（Li-S）电池因其高能量密度和成本效益而吸引了许多研究兴趣。但是，它们的S阴极因导电性差，多硫化锂（LPS）的穿梭以及体积变化大而受到干扰。在提高S阴极的电导率中，碳材料被广泛用作导电添加剂。然而，在锂-硫电池中它们的几何和结构效应仍缺乏比较研究。为此，对两种不同的典型导电添加剂，炭黑（CB）¹和氮掺杂石墨烯纳米片（N-GNS）^{2进行了系统研究。}。这项工作表明，与零维（0D）CB纳米粒子相比，二维（2D）N-GNS在结构上缺陷较少，并且具有较大的表面积。结果，N-GNS的2D结构有助于实现更高的容量保持能力，但会抑制锂离子的运输。相比之下，CB的0D结构便于运输具有更高初始容量但暴露于LPS更严重的穿梭行为的锂离子。还发现，在可持续容量，库仑效率和倍率容量方面，CB和N-GNS的组合可使Li-S电池具有更好的性能。这项研究启发了人们设计出用于Li-S电池的更好的S阴极。