In Situ Measurement of the Effect of Stress on the Chemical Diffusion Coefficient of Li in High-Energy-Density Electrodes
In Situ Measurement of the Effect of Stress on the Chemical Diffusion Coefficient of Li in High-Energy-Density Electrodes
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DOI：
10.1149/2.0641810jes
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发表时间：
2018
影响因子：
3.9
通讯作者：
R. Tripuraneni;S. Rakshit;S. Nadimpalli
中科院分区：
文献类型：
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作者：
R. Tripuraneni;S. Rakshit;S. Nadimpalli
以锂箔为对/参比电极，1MLiPF6为电解液，在EC、DEC、DMC溶液(1：1：1，wt%)中制备了溅射沉积的Ge薄膜。用恒电位间歇滴定技术(PITT)和恒流间歇滴定技术(GITT)对Ge薄膜进行了测试，同时测量了电极中的应力演化。在Gitt实验中观察到电极应力在单步滴定过程中变化很大，这违反了通常忽略电极应力的简单Fickian输运模型的假设。因此，只对PIT数据进行了分析，得到了Li在Ge中的化学扩散系数D̃。正如预期的那样，扩散系数值随着Li浓度的增加而显著增加；然而，在任何给定的Li浓度下，脱氢过程所获得的D̃值都至少比锂化过程中的值大两倍，并且随着Li浓度的升高，差异变得更大。这种差异归因于应力状态，即脱氢过程中的拉应力导致D̃值高于脱锂过程中的压应力。本文提供的数据和观察结果将有助于开发和使用电化学机械模型来产生优化的电极微结构。©作者(S)2018年。由ECS出版。本文是根据知识共享署名非商业性非衍生品4.0许可证(CC BY-NC-ND，http://creativecommons.org/licenses/by-nc-nd/4.0/)，)的条款分发的开放获取文章，该许可证允许在任何介质中非商业性地重复使用、分发和复制，前提是原始作品未以任何方式更改并被正确引用。要获得商业再利用的许可，请发送电子邮件至：OA@Electric Chem.org。[DOI：10.1149/2.0641810jes]
Sputter deposited germanium thin films were assembled in a half-cell configuration with lithium foil as counter/reference electrode and 1M LiPF6 in EC, DEC, DMC solution (1:1:1, wt%) as electrolyte. The Ge films were subjected to potentiostatic intermittent titration technique (PITT) and galvanostatic intermittent technique (GITT) conditions while simultaneously measuring the stress evolution in the electrodes. It was observed that the electrode stresses varied significantly in a single titration step during a GITT experiment, which violates the assumptions of simple Fickian transport model where the electrode stresses are usually neglected. Therefore, only the PITT data was analyzed to obtain the chemical diffusion coefficient D̃ of Li in Ge. As expected, the diffusion coefficient value increased considerably with Li concentration; however, the D̃ values obtained during delithiation are at least two times greater than those obtained during lithiation at any given Li concentration, with the difference becoming significantly higher at higher Li concentration. This difference is attributed to the stress state, i.e., tensile stress during delithiation leads to higher D̃ values compared to the compressive stresses during lithiation. The data and observations presented here will be helpful in developing and using electrochemomechanical models in producing optimized electrode microstructures. © The Author(s) 2018. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0641810jes]