Alkali metals inside bi-layer graphene and MoS2: Insights from first-principles calculations
Alkali metals inside bi-layer graphene and MoS2: Insights from first-principles calculations
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DOI：
10.1016/j.nanoen.2020.104927
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发表时间：
2020-09-01
期刊：
影响因子：
17.6
通讯作者：
Krasheninnikov, Arkady V.
中科院分区：
文献类型：
--
作者：
Chepkasov, Ilya V.;Ghorbani-Asl, Mahdi;Krasheninnikov, Arkady V.
与人们普遍认为碱金属（AM）原子嵌入层状材料中只形成单层结构的观点相反，最近的实验[Nature 564(2018) 234]表明，在双层石墨烯中，锂的多层结构是可能的。利用最先进的第一性原理计算，我们系统地研究了各种am （Li, Na， K, Rb, Cs）在双层石墨烯和二硫化钼中的插层能量。我们证明，以双层石墨烯为主体，多层结构的形成能对K、Rb和Cs为负，对Li和Na为略正。鉴于先前的锂实验数据，多层Na可能因此形成，而众所周知，单层Na在石墨基质中能量非常不利。在二硫化钼中，多层结构的能量明显高于单层结构，但仍然可以形成多层结构，特别是对于电负性最低的AMs。为了使结果合理化，我们评估了从插入剂到宿主材料的电荷转移，并分析了AM与宿主原子的离子键和共价键之间的相互作用。虽然我们的理论工作主要集中在AM嵌入的基本方面，但我们的发现可能会刺激解决多层嵌入的实验工作，以最大限度地提高AM离子电池中阳极材料的容量。
Contrary to a wide-spread belief that alkali metal (AM) atoms intercalated into layered materials form single-layer structures only, recent experiments [Nature 564 (2018) 234] showed that multi-layer configurations of lithium are possible in bi-layer graphene. Using state-of-the-art first-principles calculations, we systematically study the intercalation energetics for various AMs (Li, Na, K, Rb, Cs) in bi-layer graphene and MoS2. We demonstrate that for bi-layer graphene as host the formation energy of multi-layer structures is negative for K, Rb and Cs and only slightly positive for both Li and Na. In view of the previous experimental data on lithium, a multi-layer of Na might therefore form, while it is well-known that single-layers of Na in graphitic hosts are energetically very unfavorable. In MoS2, multi-layer structures are considerably higher in energy than the single-layer ones, but the formation of the former can still occur, especially for the AMs with the lowest electronegativity. To rationalize the results, we assess the charge transfer from the intercalants to the host material and analyze the interplay between the ionic and covalent bonding of AM and host atoms. While our theoretical effort primarily focuses on the fundamental aspects of AM intercalation, our findings may stimulate experimental work addressing multi-layer intercalation to maximize the capacity of anode materials in AM ion batteries.