State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
Nanoscale. 2019 Oct 10;11(39):18090-18098. doi: 10.1039/c9nr04854e.
Endowing separators with the polysulfide-blocking function is urgently needed for high-performance lithium-sulfur (Li-S) batteries. Thus far, most of the reported research has focused on modifying conventional polyolefin separators but with poor thermal stability and low ionic conductivity. To address these issues, herein we report a Janus separator based on a thermally stable polymeric nanofabric designed with abilities to trap polysulfides and facilitate the transport of Li+ simultaneously. This Janus separator possesses a configuration of a carbon nanofiber (CNF) layer toward the sulfur cathode and the polyimide (PI) nanofabric toward the Li metal anode. It is demonstrated that the conductive CNF layer can effectively anchor and convert the polysulfides; meanwhile, the excellent wettability with liquid electrolytes and the highly porous structure of the PI nanofiber layer significantly promote the Li+-transport. In addition, the Janus separator presents notable advantages in thermal dimensional stability benefiting from the PI nanofabric. As a result, the Li-S battery armed with the Janus separator shows a high initial capacity (1393 mA h g-1 at 0.1 A g-1), stable cycling performance (822 mA h g-1 at 1 A g-1) and high coulombic efficiency of 99.6%.
为了实现高性能的锂硫（Li-S）电池，给隔板赋予多硫化物阻断功能是当务之急。迄今为止，大多数报道的研究都集中在改性传统的聚烯烃隔板上，但它们存在热稳定性差和离子电导率低的问题。针对这些问题，本文报告了一种基于具有同时捕获多硫化物和促进 Li+传输能力的热稳定聚合物纳米纤维设计的 Janus 隔板。这种 Janus 隔板具有朝向硫阴极的碳纤维（CNF）层和朝向 Li 金属阳极的聚酰亚胺（PI）纳米纤维的构型。结果表明，导电 CNF 层可以有效地固定和转化多硫化物；同时，与液体电解质的优异润湿性和 PI 纳米纤维层的高度多孔结构显著促进了 Li+的传输。此外，Janus 隔板由于 PI 纳米纤维的存在而表现出优异的热尺寸稳定性优势。因此，装备有 Janus 隔板的 Li-S 电池表现出高初始容量（在 0.1 A g-1 时为 1393 mA h g-1）、稳定的循环性能（在 1 A g-1 时为 822 mA h g-1）和高达 99.6%的库仑效率。
