Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States.
Nano Lett. 2013;13(11):5534-40. doi: 10.1021/nl403130h. Epub 2013 Oct 24.
Lithium sulfur batteries have brought significant advancement to the current state-of-art battery technologies because of their high theoretical specific energy, but their wide-scale implementation has been impeded by a series of challenges, especially the dissolution of intermediate polysulfides species into the electrolyte. Conductive polymers in combination with nanostructured sulfur have attracted great interest as promising matrices for the confinement of lithium polysulfides. However, the roles of different conductive polymers on the electrochemical performances of sulfur electrode remain elusive and poorly understood due to the vastly different structural configurations of conductive polymer-sulfur composites employed in previous studies. In this work, we systematically investigate the influence of different conductive polymers on the sulfur cathode based on conductive polymer-coated hollow sulfur nanospheres with high uniformity. Three of the most well-known conductive polymers, polyaniline (PANI), polypyrrole (PPY), and poly(3,4-ethylenedioxythiophene) (PEDOT), were coated, respectively, onto monodisperse hollow sulfur nanopsheres through a facile, versatile, and scalable polymerization process. The sulfur cathodes made from these well-defined sulfur nanoparticles act as ideal platforms to study and compare how coating thickness, chemical bonding, and the conductivity of the polymers affected the sulfur cathode performances from both experimental observations and theoretical simulations. We found that the capability of these three polymers in improving long-term cycling stability and high-rate performance of the sulfur cathode decreased in the order of PEDOT > PPY > PANI. High specific capacities and excellent cycle life were demonstrated for sulfur cathodes made from these conductive polymer-coated hollow sulfur nanospheres.
锂硫电池因其具有高的理论比能量而使当前的电池技术取得了重大进展，但由于一系列挑战，特别是中间多硫化物物种溶解在电解质中，其广泛应用受到了阻碍。导电聚合物与纳米结构硫结合，作为限制锂多硫化物的有前途的基质引起了极大的兴趣。然而，由于之前研究中使用的导电聚合物-硫复合材料的结构配置有很大的不同，不同导电聚合物对硫电极电化学性能的作用仍然难以捉摸，也没有得到很好的理解。在这项工作中，我们系统地研究了不同导电聚合物对基于导电聚合物涂覆的高度均匀空心硫纳米球的硫阴极的影响。三种最著名的导电聚合物，聚苯胺（PANI）、聚吡咯（PPY）和聚（3,4-亚乙基二氧噻吩）（PEDOT），分别通过简便、通用和可扩展的聚合过程涂覆在单分散空心硫纳米球上。这些具有明确定义的硫纳米颗粒的硫阴极作为理想的平台，从实验观察和理论模拟两个方面研究和比较了涂层厚度、化学键合和聚合物的电导率如何影响硫阴极的性能。我们发现，这三种聚合物提高硫阴极长期循环稳定性和高倍率性能的能力按 PEDOT>PPY>PANI 的顺序降低。这些导电聚合物涂覆的空心硫纳米球制成的硫阴极表现出高的比容量和优异的循环寿命。
