Structural Characterization of Layered LixNi0.5Mn0.5O2 (0 < x

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• 作者：Christopher S. Johnson ; Jeom-Soo Kim ; A. Jeremy Kropf ; Arthur J. Kahaian ; John T. Vaughey ; Linda M. L. Fransson ; Kristina Edströ ; m ; and Michael M. Thackeray
• 刊名：Chemistry of Materials
• 出版年：2003
• 出版时间：June 17, 2003
• 年：2003
• 卷：15
• 期：12
• 页码：2313 - 2322
• 全文大小：212K
• 年卷期：v.15,no.12(June 17, 2003)
• ISSN：1520-5002

文摘

X-ray diffraction and X-ray absorption spectroscopy experiments were used to studychemical and electrochemical Li insertion and extraction reactions of LiNi_0.5Mn_0.5O₂. Theseresults, along with galvanostatic cycling data, suggest that LiNi_0.5Mn_0.5O₂ layered electrodesin lithium batteries operate predominantly off two-electron redox couples, Ni⁴⁺/Ni²⁺, betweenapproximately 4.5 and 1.25 V and Mn⁴⁺/Mn²⁺ between 1.25 and 1.0 V versus metallic Li,respectively. The retention of a stable layered framework structure and the apparent absenceof Jahn-Teller ions Ni³⁺ and Mn³⁺ in the high- or low-voltage region is believed to beresponsible for the excellent structural and electrochemical stability of these electrodes. TheLiNi_0.5Mn_0.5O₂ layered oxide reversibly reacts chemically or electrochemically with Li to forman air-sensitive, dilithium compound, Li₂Ni_0.5Mn_0.5O₂, with a hexagonal structure analogousto Li₂MnO₂. The cycling behavior of Li/LiNi_0.5Mn_0.5O₂ cells over a large voltage window (4.6-1.0 V) and with very slow rates shows that rechargeable capacities >500 mA·h/g can beobtained.