Revealing the Reconstructed Surface of Li[Mn2]O4

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• 作者：Charles D. Amos ; Manuel A. Roldan ; Maria Varela ; John B. Goodenough ; Paulo J. Ferreira
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：May 11, 2016
• 年：2016
• 卷：16
• 期：5
• 页码：2899-2906
• 全文大小：593K
• 年卷期：0
• ISSN：1530-6992

文摘

The spinel Li[Mn₂]O₄ is a candidate cathode for a Li-ion battery, but its capacity fades over a charge/discharge cycle of Li_1–x[Mn₂]O₄ (0 < x < 1) that is associated with a loss of Mn to the organic-liquid electrolyte. It is known that the disproportionation reaction 2Mn³⁺ = Mn²⁺ + Mn⁴⁺ occurs at the surface of a Mn spinel, and it is important to understand the atomic structure and composition of the surface of Li[Mn₂]O₄ in order to understand how Mn loss occurs. We report a study of the surface reconstruction of Li[Mn₂]O₄ by aberration-corrected scanning transmission electron microscopy. The atomic structure coupled with Mn-valence and the distribution of the atomic ratio of oxygen obtained by electron energy loss spectroscopy reveals a thin, stable surface layer of Mn₃O₄, a subsurface region of Li_1+x[Mn₂]O₄ with retention of bulk Li[Mn₂]O₄. This observation is compatible with the disproportionation reaction coupled with oxygen deficiency and a displacement of surface Li⁺ from the Mn₃O₄ surface phase. These results provide a critical step toward understanding how Mn is lost from Li[Mn₂]O₄, once inside a battery.