Tracking the Diffusion-Controlled Lithiation Reaction of LiMn2O4 by In Situ TEM,ACS Applied Energy Materials

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Tracking the Diffusion-Controlled Lithiation Reaction of LiMn2O4 by In Situ TEM
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2020-05-18 00:00:00 , DOI: 10.1021/acsaem.0c00380
Torben Erichsen ₁ , Björn Pfeiffer ₁ , Vladimir Roddatis ₁ , Cynthia A. Volkert _{1,

2}

Affiliation

Spinel lithium manganese oxide (Li_xMn₂O₄) is used as an active material in battery cathodes. It is a relatively inexpensive and environmentally friendly material but suffers from capacity fade during use. The capacity losses are generally attributed to the formation of the tetragonal phase (x > 1) due to overpotentials at the surfaces of the micrometer-sized particles that are used in commercial electrodes. In this study, we investigate the mechanisms of tetragonal phase formation by performing electrochemical lithiation (discharging) in situ in the transmission electron microscope (TEM) utilizing diffraction and high resolution imaging as well as spectroscopy. We observe a sharp interface between the cubic spinel (x = 1) and the tetragonal phase (x = 2) that moves under lithium diffusion control. The tetragonal phase forms as a complex nanotwinned microstructure, presumably to relieve the stresses due to expansion during lithiation. We propose that the twinned microstructure stabilizes the tetragonal phase, adding to capacity loss upon deep discharge.

中文翻译：

原位透射电子显微镜跟踪LiMn ₂ O ₄的扩散控制的锂化反应

尖晶石锂锰氧化物（Li _x Mn ₂ O ₄）被用作电池阴极中的活性材料。它是一种相对便宜且环保的材料，但在使用过程中会遭受容量衰减的影响。容量损失通常归因于用于商用电极的微米级颗粒表面上的超电势，形成了四方相（x > 1）。在这项研究中，我们通过在透射电子显微镜（TEM）中利用衍射和高分辨率成像以及光谱学方法进行电化学锂化（放电）研究了四方相形成的机理。我们观察到立方尖晶石（x= 1）和在锂扩散控制下移动的四方相（x = 2）。四方相形成为复杂的纳米孪晶微观结构，大概是为了缓解由于锂化过程中的膨胀引起的应力。我们建议孪生的微观结构稳定四方相，增加深放电时的容量损失。

更新日期：2020-05-18

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