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在二复合溶液中的Mg离子的溶解结构来自第一原理分子动力学和模拟的X射线吸收光谱

Liwen F Wan¹, David Prendergast

¹Joint Center for Energy Storage Research (JCESR), The Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.

Journal of the American Chemical Society

|September 23, 2014

概括

了解 (Mg) 离子溶解结构是可充电Mg离子电池的关键. 模拟显示Mg2+) 在THF电解质中主要是四协调的,而不是六协调的.

科学领域:

电化学电化学电化学
材料科学材料科学材料科学
计算化学计算化学

背景情况:

(Mg) 离子溶解结构对于理解Mg离子电池运输和接口机制至关重要.
现有的可充电Mg离子电池系统使用二复合物 (DCC) 解决方案,目前关于Mg2+) 协调 (四相对六相协调) 的争论仍在进行中.
精确的溶解知识对于优化Mg离子电池性能至关重要.

研究的目的:

提供对二复合物 (DCC) 溶液中Mg离子的溶解复合物的理论见解.
为了澄清四二 (THF) 电解质中的Mg2+的协调状态 (四与六).
建立一种实验验证Mg溶解结构的方法.

主要方法:

采用第一原理分子动力学模拟 (FPMD) 来研究Mg溶解结构.
在中性和充电状态下被认为是Mg单体和二元物种.
在Mg K边缘使用FPMD轨迹模拟的X射线吸收光谱 (XAS).

主要成果:

发现Mg2+) 离子在室温THF溶液中主要表现出四协调,与固态阶段的六协调形成鲜明对比.
预测,从四度到六度协调的转移会导致X射线吸收开始时至少1 eV的蓝色转移.
证明了XAS在区分不同Mg溶解状态的实用性.

结论:

在DCC/THF电解质中占主导地位的Mg2+) 溶解结构是四协调的.
射线吸收光谱 (XAS) 可以作为一个敏感的探测器来监测溶解球变化.
这种方法可以阐明在电解质/电极接口上的Mg溶解/沉积机制.

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