Formation of Type II Silicon Clathrate with Lithium Guests through Thermal Diffusion
Formation of Type II Silicon Clathrate with Lithium Guests through Thermal Diffusion
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DOI：
10.1021/acs.inorgchem.2c03703
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发表时间：
2023-01-30
影响因子：
4.6
通讯作者：
Collins，Reuben T.
中科院分区：
文献类型：
--
作者：
Liu，Yinan;Briggs，Joseph P.;Collins，Reuben T.
在低客体原子浓度下，Si笼形物可以被视为半导体，客体原子充当掺杂剂，可能产生具有令人兴奋的光电和自旋特性的金刚石Si的替代品。研究具有不同客体原子的Si笼形物不仅可以深入了解Si笼形物的电子结构，还可以深入了解每个客体可以为Si笼形物结构带来的独特性质。然而，与钠以外的客人合成硅包合物具有挑战性。在这项研究中，我们已经开发了一种替代方法，使用热扩散到II型硅笼形物与极低的钠浓度，创造硅笼形物与锂客人。使用飞行时间二次离子质谱，X射线衍射，和拉曼散射，热扩散到几乎空的硅笼形物框架的锂检测和其特征在于作为一个函数的扩散温度和时间。有趣的是，Si笼形物在Li的存在下表现出降低的结构稳定性，在起始Na客体Si笼形物相当稳定的温度下退火转化为多晶或无序相。插入到Si笼形晶格中的Li原子贡献自由载流子，其可以通过它们对骨架中的Si-Si键强度的影响在拉曼散射中检测到。这些载体也可以在电子顺磁共振（EPR）中观察到。EPR表明，然而，Li客人不是简单的类似物Na客人。特别是，我们的研究结果表明，锂原子，其较小的尺寸，往往双重占据笼，形成“分子”对与其他锂或钠原子。这一工作的结果提供了一个更深入的了解锂客体原子的硅笼合物。这些发现也与理解锂离子电池中锂如何移动并与硅笼形阳极相互作用有关。此外，在这项工作中提出的技术展示了一种新的方法，用于填充的硅笼形物笼，使广泛的其他客人在硅笼形物的研究。
At low guest atom concentrations, Si clathrates can be viewed as semiconductors, with the guest atoms acting as dopants, potentially creating alternatives to diamond Si with exciting optoelectronic and spin properties. Studying Si clathrates with different guest atoms would not only provide insights into the electronic structure of the Si clathrates but also give insights into the unique properties that each guest can bring to the Si clathrate structure. However, the synthesis of Si clathrates with guests other than Na is challenging. In this study, we have developed an alternative approach, using thermal diffusion into type II Si clathrate with an extremely low Na concentration, to create Si clathrate with Li guests. Using time-of-flight secondary-ion mass spectroscopy, X-ray diffraction, and Raman scattering, thermal diffusion of Li into the nearly empty Si clathrate framework is detected and characterized as a function of the diffusion temperature and time. Interestingly, the Si clathrate exhibits reduced structural stability in the presence of Li, converting to polycrystalline or disordered phases for anneals at temperatures where the starting Na guest Si clathrate is quite stable. The Li atoms inserted into the Si clathrate lattice contribute free carriers, which can be detected in Raman scattering through their effect on the strength of Si–Si bonds in the framework. These carriers can also be observed in electron paramagnetic resonance (EPR). EPR shows, however, that Li guests are not simple analogues of Na guests. In particular, our results suggest that Li atoms, with their smaller size, tend to doubly occupy cages, forming “molecular-like” pairs with other Li or Na atoms. Results of this work provide a deeper insight into Li guest atoms in Si clathrate. These findings are also relevant to understanding how Li moves through and interacts with Si clathrate anodes in Li-ion batteries. Additionally, techniques presented in this work demonstrate a new method for filling the Si clathrate cages, enabling studies of a broad range of other guests in Si clathrates.