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Dislocation and oxygen-release driven delithiation in Li2MnO3
Kei Nakayama1, Ryo Ishikawa1,2, Shunsuke Kobayashi3
1Institute of Engineering Innovation, University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan.
Nature Communications
|September 9, 2020
Summary
Lithium-excess cathode materials like Li2MnO3 undergo irreversible oxygen release and cation mixing during delithiation. These defects and dislocations at the interface control delithiated region growth and material degradation.
Area of Science:
- Materials Science
- Electrochemistry
- Nanotechnology
Background:
- Lithium-excess layered cathode materials, such as Li2MnO3, are promising for high-energy-density batteries.
- Delithiation in these materials can lead to oxygen release and cation mixing, but the growth mechanisms of these defects remain unclear.
Purpose of the Study:
- To directly observe the atomic structures at the interface between pristine and delithiated regions in partially delithiated Li2MnO3 single crystals.
- To elucidate the mechanisms governing the growth of delithiated regions and associated performance degradation.
Main Methods:
- Atomic-resolution scanning transmission electron microscopy (STEM).
- Electron energy-loss spectroscopy (EELS).
Main Results:
- Direct observation of irreversible defects, including oxygen release and Mn/Li cation mixing, in delithiated regions.
- Formation of a partially cation-disordered structure at the interface with Mn migration confined to specific layers.
- Generation of dislocations at the interface to accommodate lattice mismatch between pristine and delithiated areas.
Conclusions:
- Oxygen release and dislocations are key factors influencing the growth of delithiated regions in Li2MnO3.
- These phenomena play a critical role in the performance degradation of lithium-excess layered cathode materials.
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