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Electron Microscopy Investigation of the Cycling-Induced Phase Transformation in LiMnO2 Compounds
Published online by Cambridge University Press: 10 February 2011
Abstract
Lithium transition metal oxides used as intercalation electrodes for rechargeable lithium batteries are widely studied in search of structural stability and improved electrochemical performance. Recent studies showed that the orthorhombic and monoclinic LiMnO2 compounds, unlike LiMn204 spinels, could be cycled on both the 4 V and 2.9 V plateaus with high and stable discharge capacity. In this study, we have performed direct high resolution observations of electrochemically cycled LiMnO2 particles in the fully discharged state. Extensive damage including local strain variation, nanodomain formation, and changes in cation ordering, has been observed. Individual particles retain overall single crystallinity despite having differing structures at the nanodomain level. While cycling causes a macroscopic transformation to spinel cation ordering, the formation of nanodomains differing in cation ordering and/or composition appears to accommodate or prevent the destructive Jahn-Teller distortion that normally occurs at high lithium concentration, thereby resulting in cycling stability.
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- Copyright © Materials Research Society 1999
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