Understanding the Initial Stages of Reversible Mg Deposition and Stripping in Inorganic Nonaqueous Electrolytes
Understanding the Initial Stages of Reversible Mg Deposition and Stripping in Inorganic Nonaqueous Electrolytes
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DOI：
10.1021/acs.chemmater.5b00389
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发表时间：
2015-05-12
影响因子：
8.6
通讯作者：
Ceder, Gerbrand
中科院分区：
文献类型：
--
作者：
Canepa, Pieremanuele;Gautam, Gopalakrishnan Sai;Ceder, Gerbrand
基于Mg金属阳极与高压（类似于3 V）插入阴极配对的多价（MV）电池架构为显着超越传统锂离子电池的储能性能提供了现实的设计途径，但目前只有少数电解质系统支持可逆的Mg沉积。本文采用静态第一性原理计算和从头算分子动力学方法，在四氢呋喃（THF）液体中，以Mg2+和Cl-为电解质，对几种盐和溶剂在Mg金属界面上的吸附进行了全面的研究。我们的发现不仅提供了界面上稳定物质的图片，而且还解释了该系统如何支持可逆的Mg沉积，因此，我们为如何设计其他用于Mg电镀和剥离的电解质提供了见解。活性沉积物质是由THF配位的（MgCl+）单体，与可能的钝化物质（如THF溶剂或中性MgCl2配合物）相比，它们对Mg具有优先吸附。沉积后，这些吸附配合物脱溶和促进电荷转移的能量很小（从最强的吸附配合物中去除3个THF的能量约为61-46.2 kJ mol(-1)），并且吸附但脱溶的（MgCl）（+）配合物的稳定取向似乎有利于电荷转移。最后，在非常低的THF配位（0和1）下，Mg-Cl在Mg表面解离的观察表明，在电镀时可能会发生有害的Cl掺入阳极。在汽提过程中，这有利于进一步促进脱镁反应。
Multivalent (MV) battery architectures based on pairing a Mg metal anode with a high-voltage (similar to 3 V) intercalation cathode offer a realistic design pathway toward significantly surpassing the energy storage performance of traditional Li-ion-based batteries, but there are currently only few electrolyte systems that support reversible Mg deposition. Using both static first-principles calculations and ab initio molecular dynamics, we perform a comprehensive adsorption study of several salt and solvent species at the interface of Mg metal with an electrolyte of Mg2+ and Cl- dissolved in liquid tetrahydrofuran (THF). Our findings not only provide a picture of the stable species at the interface but also explain how this system can support reversible Mg deposition, and as such, we provide insights in how to design other electrolytes for Mg plating and stripping. The active depositing species are identified to be (MgCl+) monomers coordinated by THF, which exhibit preferential adsorption on Mg compared to possible passivating species (such as THF solvent or neutral MgCl2 complexes). Upon deposition, the energy to desolvate these adsorbed complexes and facilitate charge transfer is shown to be small (similar to 61-46.2 kJ mol(-1) to remove three THF from the strongest adsorbing complex), and the stable orientations of the adsorbed but desolvated (MgCl)(+) complexes appear to be favorable for charge transfer. Finally, observations of Mg-Cl dissociation at the Mg surface at very low THF coordinations (0 and 1) suggest that deleterious Cl incorporation in the anode may occur upon plating. In the stripping process, this is beneficial by further facilitating the Mg removal reaction.