Structure and chemical composition of the Mg electrode during cycling in a simple glyme electrolyte
Structure and chemical composition of the Mg electrode during cycling in a simple glyme electrolyte
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DOI：
10.1016/j.ensm.2024.103280
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发表时间：
2024-02
影响因子：
20.4
通讯作者：
Konstantinos Dimogiannis;Andrzej Sankowski;Conrad Holc;C. Parmenter;Graham N. Newton;Darren A. Walsh;James O'Shea;Andrei N. Khlobystov;Lee R. Johnson
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文献类型：
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作者：
Konstantinos Dimogiannis;Andrzej Sankowski;Conrad Holc;C. Parmenter;Graham N. Newton;Darren A. Walsh;James O'Shea;Andrei N. Khlobystov;Lee R. Johnson
镁的体积能量密度超过了锂，使得镁电池特别有希望成为下一代储能电池。然而，镁电极在普通电池电解质中的电化学循环在库仑上是低效的，并且观察到显著的充电和放电过电位。已经提出了几种基于Mg（TFSI）2-甘醇二甲醚电解质的添加剂和电解质制剂作为这些问题的解决方案。然而，这些进步的影响和价值通常难以辨别，这是由于缺乏对下面的Mg（TFSI）2-甘醇二甲醚电解质中的Mg电极的组成和性能的了解。本文首次描述了Mg在Mg（TFSI）2-甘醇二甲醚电解质溶液中电化学循环过程中发生的化学和结构变化。使用聚焦离子束扫描电子显微镜，我们表明，在循环过程中沉积的镁由一个壳的降解产物，这反过来又包围了一个活跃的镁核心。这些结构在循环过程中由于Mg结合到芯中而经历膨胀和收缩，导致沉积物的结构变形和降解。使用这个结构模型，我们讨论了镁电极的电化学循环过程中观察到的复杂性，并阐明了充电过程中观察到的过电位的起源。本文提出的新理解和方法将使电解质添加剂对镁电极性能的影响得以解决。
The volumetric energy density of magnesium exceeds that of lithium, making magnesium batteries particularly promising for next-generation energy storage. However, electrochemical cycling of magnesium electrodes in common battery electrolytes is coulombically inefficient and significant charging and discharging overpotentials are observed. Several additives and electrolyte formulations based on Mg(TFSI)2-glyme electrolytes have been proposed as solutions to these problems. However, the impact and value of these advances is often hard to discern due to a lack of knowledge of the composition and performance of the Mg electrode in the underlying Mg(TFSI)2-glyme electrolyte. In this paper, the chemical and structural changes that occur during electrochemical cycling of Mg in Mg(TFSI)2-glyme electrolyte solutions are described for the first time. Using focused ion beam-scanning electron microscopy, we show that the Mg deposited during cycling consists of a shell of degradation products, which in turn surrounds an active Mg core. These structures undergo expansion and contraction during cycling due to incorporation of Mg into the core, resulting in structural deformation and degradation of the deposits. Using this structural model, we discuss the complexities observed during electrochemical cycling of Mg electrodes and elucidate the origins of the overpotentials observed during charging. The new understanding and methodology presented here will allow the impact of electrolyte additives on the performance of the Mg electrode to be resolved.