Reversible superdense ordering of lithium between two graphene sheets
Reversible superdense ordering of lithium between two graphene sheets
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DOI：
10.1038/s41586-018-0754-2
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发表时间：
2018-12-13
期刊：
影响因子：
64.8
通讯作者：
Smet, Jurgen H.
中科院分区：
文献类型：
--
作者：
Kuehne, Matthias;Boerrnert, Felix;Smet, Jurgen H.
许多碳同素异形体可以作为可逆锂吸收的主体材料（1，2），从而为现有和未来的电化学能量储存奠定基础。然而，从一个工作系统中很难了解锂在这些宿主中的排列方式。例如，使用原位透射电子显微镜（3-5）来探测轻元素（特别是锂）（6，7）受到它们对撞击电子的低散射截面和它们对撞击损伤的敏感性（8）的严重阻碍。在这里，我们通过原位低电压透射电子显微镜研究锂可逆嵌入双层石墨烯，使用球面和色差校正（9）将对比度和分辨率提高到所需水平。显微镜得到了电子能量损失谱和密度泛函理论计算的支持。在它们从覆盖长而窄的双层的一端的电化学电池远程插入时，我们观察到锂原子在两个碳片之间呈现多层紧密堆积的顺序。与该超致密相相关的锂储存容量远远超过由LiC 6的形成所预期的锂储存容量，LiC 6的形成是在本体石墨碳（10）内锂嵌入的正常条件下已知的致密构型。因此，我们的研究结果指出，可能存在不同的存储安排的离子在二维层状材料相比，其散装母体化合物。
Many carbon allotropes can act as host materials for reversible lithium uptake(1,2), thereby laying the foundations for existing and future electrochemical energy storage. However, insight into how lithium is arranged within these hosts is difficult to obtain from a working system. For example, the use of in situ transmission electron microscopy(3-5) to probe light elements (especially lithium)(6,7) is severely hampered by their low scattering cross-section for impinging electrons and their susceptibility to knock-on damage(8). Here we study the reversible intercalation of lithium into bilayer graphene by in situ low-voltage transmission electron microscopy, using both spherical and chromatic aberration correction(9) to enhance contrast and resolution to the required levels. The microscopy is supported by electron energy-loss spectroscopy and density functional theory calculations. On their remote insertion from an electrochemical cell covering one end of the long but narrow bilayer, we observe lithium atoms to assume multi-layered close-packed order between the two carbon sheets. The lithium storage capacity associated with this superdense phase far exceeds that expected from formation of LiC6, which is the densest configuration known under normal conditions for lithium intercalation within bulk graphitic carbon(10). Our findings thus point to the possible existence of distinct storage arrangements of ions in two-dimensional layered materials as compared to their bulk parent compounds.