Jodlbauer Anna, Hogrefe Katharina, Gadermaier Bernhard, Wilkening H Martin R
Institute of Chemistry and Technology of Materials Graz University of Technology Stremayrgasse 9 A-8010 Graz Austria.
Small Sci. 2024 Jul 30;4(10):2400199. doi: 10.1002/smsc.202400199. eCollection 2024 Oct.
The enormous interest in developing powerful Li-based batteries leads to a boost in materials research. Though Li-sulfur batteries offer very high energy densities, the nature of Li-ion dynamics in the final discharge product has not been fully understood yet. While nanocrystalline shows enhanced ion dynamics compared to its coarse-grained counterpart, the interaction of with another binary such as LiI seems to be rather unexplored. Herein, an equimolar mixture of and LiI is treated in a high-energy ball mill, and both the overall and local structural changes are studied by X-ray powder diffraction and nuclear magnetic resonance (NMR), respectively . Besides the formation of amorphous regions, evidences are found for the generation of anion-mixed sites that give rise to facile Li exchange on the 2D exchange NMR timescale. Compared to a coarse-grained reference sample, the overall (bulk) ionic conductivity of nanocrystalline -LiI increases by two orders of magnitude. Besides the anion-mixing effect, this increase benefits from nanosize effects that include the formation of defect-rich interfacial regions. NMR relaxation measurements fully support this result and reveal heterogeneous dynamics with lower activation energies for both the localized hopping processes and long-range ion transport in nm-sized -LiI.
对开发高性能锂电池的巨大兴趣推动了材料研究的发展。尽管锂硫电池具有很高的能量密度，但最终放电产物中锂离子动力学的本质尚未完全被理解。虽然纳米晶与其粗晶对应物相比表现出增强的离子动力学，但它与另一种二元化合物如碘化锂的相互作用似乎尚未得到充分探索。在此，将纳米晶与碘化锂的等摩尔混合物在高能球磨机中处理，并分别通过X射线粉末衍射和核磁共振（NMR）研究其整体和局部结构变化。除了形成非晶区域外，还发现了阴离子混合位点产生的证据，这些位点在二维交换核磁共振时间尺度上导致了容易的锂交换。与粗晶参考样品相比，纳米晶 - 碘化锂的整体（体相）离子电导率提高了两个数量级。除了阴离子混合效应外，这种增加还受益于纳米尺寸效应，包括形成富含缺陷的界面区域。核磁共振弛豫测量完全支持这一结果，并揭示了纳米尺寸的 - 碘化锂中局部跳跃过程和长程离子传输的具有较低活化能的非均匀动力学。
