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Direct imaging of oxygen shifts associated with the oxygen redox of Li-rich layered oxides
Joule ( IF 39.8 ) Pub Date : 2022-05-06 , DOI: 10.1016/j.joule.2022.04.008
Weixin Song , Miguel A. Pérez-Osorio , John-Joseph Marie , Emanuela Liberti , Xiaonan Luo , Colum O’Leary , Robert A. House , Peter G. Bruce , Peter D. Nellist

Li-rich metal oxides, such as Li1.2Ni0.13Mn0.54Co0.13O2, can deliver high specific capacities because of the redox of lattice O2− in addition to the cations. Observing oxygen distortions is key to understand the redox process. Electron ptychography is a phase-reconstruction method in 4D scanning transmission electron microscopy, providing atomic-resolution phase images with high signal-to-noise ratio and dose efficiency. Herein, we use electron ptychography to image the oxygen shift in Li1.2Ni0.13Mn0.54Co0.13O2 during the first cycle. The picometer-scale precision measurement shows distinct oxygen shifts in the bulk and surface after charging and compares with various theoretical anionic redox models. The shift after discharging is not seen to recover in the bulk accounting for voltage hysteresis; however, it recovers close to the surface, although with a phase change. We suggest that Li1.2Ni0.13Mn0.54Co0.13O2 proceeds distinct oxygen redox in the bulk and surface. The altered oxygen sublattice after first cycle potentially explains the changed voltage profiles of following cycles.



中文翻译:

与富锂层状氧化物的氧氧化还原相关的氧位移的直接成像

富锂金属氧化物,例如 Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2 ,​​由于除了阳离子之外晶格 O 2-的氧化还原,可以提供高比容量。观察氧畸变是了解氧化还原过程的关键。Electron ptychography 是 4D 扫描透射电子显微镜中的一种相位重建方法,可提供具有高信噪比和剂量效率的原子分辨率相位图像。在此,我们使用电子平面成像技术对 Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2中的氧位移进行成像在第一个周期。皮米级精确测量显示充电后体积和表面中明显的氧位移,并与各种理论阴离子氧化还原模型进行比较。考虑到电压滞后,放电后的偏移在整体上没有恢复;然而,它在接近地表的地方恢复,尽管有相变。我们认为 Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2在本体和表面进行明显的氧氧化还原。第一次循环后改变的氧亚晶格可能解释了后续循环的电压分布变化。

更新日期:2022-05-06
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