First-Principles Study on the Peculiar Water Environment in a Hydrate-Melt Electrolyte
First-Principles Study on the Peculiar Water Environment in a Hydrate-Melt Electrolyte
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DOI：
10.1021/acs.jpclett.9b02207
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发表时间：
2019-10-17
影响因子：
5.7
通讯作者：
Yamada, Atsuo
中科院分区：
文献类型：
--
作者：
Miyazaki, Kasumi;Takenaka, Norio;Yamada, Atsuo
水性电解质在提高锂离子电池的安全性和生产成本方面具有巨大的潜力。我们最近的材料探索导致了锂盐二水合物熔体Li（TFSI）（0.7）（BETI）（0.3）中心点2H（2）O的发现，其具有非常宽的电势窗口。为了阐明这种独特的水溶液体系的详细的液体结构和电子状态，第一性原理分子动力学研究已经进行。我们发现，水合物熔体中的水分子以孤立的单体或仅由几个（最多五个）H2O分子组成的簇存在。无论是单体和集群的电子结构在很大程度上偏离在散装水，其中最低的未占状态是更高的能量比锂盐阴离子，这优先导致阴离子还原导致形成的阴离子衍生的稳定solidelectrolyte interphase。这清楚地表明了特有的水环境所固有的特征电子结构对于水合物熔体的非凡电化学稳定性的作用。
Aqueous electrolytes have great potential to improve the safety and production costs of Li-ion batteries. Our recent materials exploration led to the discovery of the Li-salt dihydrate melt Li(TFSI)(0.7)(BETI)(0.3)center dot 2H(2)O, which possesses an extremely wide potential window. To clarify the detailed liquid structure and electronic states of this unique aqueous system, a first-principles molecular dynamics study has been conducted. We found that water molecules in the hydrate melt exist as isolated monomers or clusters consisting of only a few (at most five) H2O molecules. Both the monomers and the clusters have electronic structures largely deviating from that in bulk water, where the lowest unoccupied states are higher in energy than that of the Li-salt anions, which preferentially cause anion reduction leading to formation of an anion-derived stable solidelectrolyte interphase. This clearly shows the role of characteristic electronic structure inherent to the peculiar water environment for the extraordinary electrochemical stability of hydrate melts.