Seo Hyeon Kook, Hwa Yoon, Chang Joon Ha, Park Jae Yeol, Lee Jae Sang, Park Jungjae, Cairns Elton J, Yuk Jong Min
Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.
Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Nano Lett. 2020 Mar 11;20(3):2080-2086. doi: 10.1021/acs.nanolett.0c00058. Epub 2020 Feb 28.
Understanding of lithium polysulfide (Li-PS) formation and the shuttle phenomenon is essential for practical application of the lithium/sulfur (Li/S) cell, which has superior theoretical specific energy (2600 Wh/kg). However, it suffers from the lack of direct observation on behaviors of soluble Li-PS in liquid electrolytes. Using in situ graphene liquid cell electron microscopy, we have visualized formation and diffusion of Li-PS simultaneous with morphological and phase evolutions of sulfur nanoparticles during lithiation. We found that the morphological changes and Li-PS diffusion are retarded by ionic liquid (IL) addition into electrolyte. Chronoamperometric shuttle current measurement confirms that IL addition lowers the experimental diffusion coefficient of Li-PS by 2 orders of magnitude relative to that in IL-free electrolyte and thus suppresses the Li-PS shuttle current, which accounts for better cyclability and Coulombic efficiency of the Li/S cell. This study provides significant insights into electrolyte design to inhibit the polysulfide shuttle phenomenon.
理解多硫化锂（Li-PS）的形成和穿梭现象对于锂硫（Li/S）电池的实际应用至关重要，该电池具有卓越的理论比能量（2600 Wh/kg）。然而，它存在缺乏对液体电解质中可溶性Li-PS行为的直接观察的问题。利用原位石墨烯液体池电子显微镜，我们在锂化过程中可视化了Li-PS的形成和扩散，同时观察到了硫纳米颗粒的形态和相演变。我们发现，向电解质中添加离子液体（IL）会阻碍形态变化和Li-PS扩散。计时电流法穿梭电流测量证实，相对于无IL电解质，添加IL使Li-PS的实验扩散系数降低了2个数量级，从而抑制了Li-PS穿梭电流，这解释了Li/S电池具有更好的循环稳定性和库仑效率的原因。这项研究为抑制多硫化物穿梭现象的电解质设计提供了重要见解。
