Manganese Migration in Li1-xMn2O4 Cathode Materials

•Use of DPC to identify changes in local structural by simultaneously imaging Li, Mn, and O species.•Monitor Mn migration to tetrahedral Li atomic positions in LiMn2O4.•A methodology to investigate the stability of Li-based compounds, using electron beam induced migration. LiMn2O4 has been considere...

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Bibliographic Details
Published in:Ultramicroscopy 2021-06, Vol.225, p.113285-113285, Article 113285
Main Authors: Calderon V, S., Ribeiro, R.M., Ferreira, P.J.
Format: Article
Language:English
Subjects:
Battery
cathodes
DPC
Li-ion
STEM
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Summary:•Use of DPC to identify changes in local structural by simultaneously imaging Li, Mn, and O species.•Monitor Mn migration to tetrahedral Li atomic positions in LiMn2O4.•A methodology to investigate the stability of Li-based compounds, using electron beam induced migration. LiMn2O4 has been considered one of the most promising cathode materials for Li-ion batteries due to its thermal stability, abundance, environmental affinity, and the possibility to exchange Li-ions in three-dimensions. However, it still suffers from major problems, such as capacity fading and voltage decay, which has been associated to phase transformations and dissolution of transition metals. In this report, we use scanning transmission electron microscopy, coupled with differential phase contrast (DPC), to better understand the mechanisms behind the structural transformations occurring in LiMn2O4. We use the fact that DPC has the ability to observe simultaneously light and heavy elements, as well as measure projected electric fields and charge distribution at the atomic level. This approach allows us to monitor the migration of very low amounts of Mn to the Li atomic positions, at the surface and subsurface regions, which otherwise is very challenging to observe using other techniques such as HAADF and ABF. These observations not only provide a fundamental understanding of the structure of LiMn2O4 but also reveal DPC as a novel technique to determine local structural changes in materials consisting of heavy and light elements, as well as identify the location of light elements, monitor low concentrations of substitutional species and identify phase transformations.
ISSN:0304-3991
1879-2723
DOI:10.1016/j.ultramic.2021.113285