Dong Qin, Shen Runping, Li Cunpu, Gan Ruiyi, Ma Xiaotong, Wang Jianchuan, Li Jing, Wei Zidong
School of Chemistry and Chemical Engineering, Chongqing University, Shapingba 174, Chongqing, 400044, China.
Small. 2018 Dec;14(52):e1804277. doi: 10.1002/smll.201804277. Epub 2018 Nov 26.
Rechargeable lithium-sulfur batteries, which use sulfur as the cathode material, promise great potentials to be the next-generation high-energy system. However, higher-order lithium polysulfides, Li S (x = 4, 6, and 8), regardless of in charge or in discharge, always form first, dissolve subsequently in the electrolyte, and shuttle to the cathode and the anode, which is called "shuttle effect." The polysulfides shuttle effect leads to heavy loss of the active-sulfur materials. Literature works mostly "cover or fill" the pores to block polysulfides from shuttling, which also hinder the lithium ion transfer. Here a protocol is invented to grasp polysulfides based on the "soft and hard acid-base" theory. Tertiary amine layer (TAL) polymerized on a polypropylene separator selectively coordinates with the dissolved high-order Li S in the cathode. Meanwhile, the transportation of lithium cations is not interrupted because of enough pores left for their transportation. After 400 cycles of charge/discharge at 0.5C, the TAL modified separator battery still possesses a capacity of 865 mAh g , which is among the best of the state-of-the-art performances of lithium-sulfur batteries. The flexible "polysulfides tongs" construction method paves a new way for Li-S batteries to reach desired performances with less worry about polysulfides shuttle.
以硫作为阴极材料的可充电锂硫电池，有望成为下一代高能量系统。然而，高阶多硫化锂Li₂Sₓ（x = 4、6和8），无论在充电还是放电过程中，总是首先形成，随后溶解在电解质中，并穿梭到阴极和阳极，这被称为“穿梭效应”。多硫化物穿梭效应导致活性硫材料大量损失。文献工作大多是“覆盖或填充”孔隙以阻止多硫化物穿梭，这也阻碍了锂离子传输。在此，基于“软硬酸碱”理论发明了一种捕获多硫化物的方法。在聚丙烯隔膜上聚合的叔胺层（TAL）与阴极中溶解的高阶Li₂Sₓ选择性配位。同时，由于留下了足够的孔隙供锂阳离子传输，所以锂阳离子的传输不会中断。在0.5C下进行400次充放电循环后，TAL改性隔膜电池仍具有865 mAh g⁻¹的容量，这在锂硫电池的当前最佳性能中名列前茅。这种灵活的“多硫化物夹钳”构建方法为锂硫电池实现理想性能且减少对多硫化物穿梭的担忧开辟了一条新途径。
