Atomic force microscopy study of surface morphology change in spinel LiMn2O4: Possibility of direct observation of Jahn-Teller instability |
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Authors: | K Kuriyama A Onoue K Kushida |
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Institution: | a College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584, Japan b Department of Arts and Sciences, Osaka Kyoiku University, Kashiwara, Osaka 582-8582, Japan |
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Abstract: | Surface morphology in 3.5 × 3.5 μm2 area of spinel LiMn2O4, which is a typical cathode material for Li ion secondary batteries, is studied using an atomic force microscopy (AFM) with a conductive probe. Negative bias voltage is applied to the probe to attract Li+ ions toward LiMn2O4 surface during the AFM observation. Before applying the voltage (0 V), the whole LiMn2O4 surface is covered with scale-shaped grains. Under the negative voltage of 5.5 V, electric current abruptly increases, indicating Li+ ionic conduction. Simultaneously, part of the scale-shaped grains expand and flatten. Jahn-Teller phase transition, which is induced by the repulsive interaction between the Mn-eg and O-2p electrons in Li accumulated layer, is proposed as a possible origin of these results. |
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Keywords: | Atomic force microscopy Surface morphology In situ observation Jahn-Teller phase transition LiMn2O4 Li secondary batteries |
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