Nakayama Kei, Ishikawa Ryo, Kobayashi Shunsuke, Shibata Naoya, Ikuhara Yuichi
Institute of Engineering Innovation, University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan.
PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama, 332-0012, Japan.
Nat Commun. 2020 Sep 8;11(1):4452. doi: 10.1038/s41467-020-18285-z.
Lithium-excess layered cathode materials such as LiMnO have attracted much attention owing to their high energy densities. It has been proposed that oxygen-release and cation-mixing might be induced by delithiation. However, it is still unclear as to how the delithiated-region grows. Here, by using atomic-resolution scanning transmission electron microscopy combined with electron energy-loss spectroscopy, we directly observe the atomic structures at the interface between pristine and delithiated regions in the partially delithiated LiMnO single crystal. We elucidate that the delithiated regions have extensive amounts of irreversible defects such as oxygen-release and Mn/Li cation-mixing. At the interface, a partially cation disordered structure is formed, where Mn migration occurred only in the specific Mn/Li layers. Besides, a number of dislocations are formed at the interface to compensate the lattice mismatch between the pristine and delithiated regions. The observed oxygen-release and dislocations could govern the growth of delithiated-regions and performance degradation in LiMnO.
诸如LiMnO之类的富锂层状阴极材料因其高能量密度而备受关注。有人提出，脱锂可能会导致氧释放和阳离子混合。然而，脱锂区域如何生长仍不清楚。在这里，通过使用原子分辨率扫描透射电子显微镜结合电子能量损失谱，我们直接观察了部分脱锂的LiMnO单晶中原始区域和脱锂区域之间界面处的原子结构。我们阐明，脱锂区域有大量不可逆缺陷，如氧释放和Mn/Li阳离子混合。在界面处，形成了部分阳离子无序结构，其中Mn迁移仅发生在特定的Mn/Li层中。此外，在界面处形成了许多位错以补偿原始区域和脱锂区域之间的晶格失配。观察到的氧释放和位错可能控制LiMnO中脱锂区域的生长和性能退化。
