结构化诱导的LiCoO2正极中Co离子的电荷梯度分布,The Journal of Physical Chemistry Letters

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结构化诱导的LiCoO2正极中Co离子的电荷梯度分布
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2019-11-25 , DOI: 10.1021/acs.jpclett.9b02711
Shuai Li _{1,

2,

3} , Kaili Li _{1,

2} , Jieyun Zheng ₄ , Qinghua Zhang ₄ , Bin Wei ₁ , Xia Lu ₁

Affiliation

层状LiCoO2作为锂离子电池的阴极模型已经引起了极大的关注，而其结构不稳定性，尤其是在高去磁化区域中的结构不稳定性仍未得到解决。为了揭示结构的基本原理，使用了原位和非原位技术对LiCoO2电极在较长的脱锂范围内进行了研究。在高度去锂化的LiCoO2电极中，独特的电荷补偿过程导致Co2 + / Co3 + / Co4 +离子从表面到整个空间的空间电荷梯度，可以通过结构变形，Li提取和表面副反应进一步控制该电荷梯度。配位的表面氧被证明具有电化学活性，并且在循环期间参与电荷补偿时是完全可逆的。而且，通过引入不需要的表面Li-Co反位点，可以使活性晶格O显着稳定，这在适应由体积变化引起的内部应力方面也起着有效的作用。这些发现有效地将结构变化与Li + / e-迁移动力学联系起来，阐明了去锂化时LiCoO2阴极的降解，为改善LiCoO2本身的电化学性能以及开发用于电池社区的高能量密度阴极提供了有益的途径。

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Structural Distortion-Induced Charge Gradient Distribution of Co Ions in Delithiated LiCoO2 Cathode.

Layered LiCoO2 has drawn tremendous attention as a modeling cathode for Li-ion batteries, while its structural instability, especially in the high delithiation region, remains unsolved. With the aim of revealing the structural fundamentals, LiCoO2 electrodes are investigated at a long delithiation range using both in situ and ex situ techniques. In the highly delithiated LiCoO2 electrode, the unique charge compensation process leads to a spatial charge gradient of Co2+/Co3+/Co4+ ions from surface to bulk, which can be further manipulated by structural distortion, Li extraction, and surface side reactions. The coordinated surface oxygen is shown to be electrochemically active and fully reversible in participating in the charge compensation during cycling. Moreover, the active lattice O can be significantly stabilized by introducing the undesired surface Li-Co antisites, which also play an effective role in accommodating the internal stress induced by volume changes. These findings effectively bridge the structural changes with the Li+/e- migration kinetics to elucidate the degradation of LiCoO2 cathode upon delithiation, demonstrating a rewarding avenue for improving the electrochemical performance of LiCoO2 itself and developing high energy density cathodes for the battery community as well.

更新日期：2019-11-28

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