Probing the Local Structure and the Role of Protons in Lithium Sorption Processes of a New Lithium-Rich Manganese Oxide

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• 作者：Marí ; a J. Ariza ; Deborah J. Jones ; Jacques Roziè ; re ; Ramesh Chitrakar ; and Kenta Ooi
• 刊名：Chemistry of Materials
• 出版年：2006
• 出版时间：April 4, 2006
• 年：2006
• 卷：18
• 期：7
• 页码：1885 - 1890
• 全文大小：133K
• 年卷期：v.18,no.7(April 4, 2006)
• ISSN：1520-5002

文摘

Lithium exchange mechanisms, local structure, and its possible evolutions on lithium extraction andreinsertion are studied in Li_1.6Mn_1.6O₄, a new lithium-rich manganese oxide showing improved lithiumsorption. The parent Li_1.6Mn_1.6O₄ and its lithium-extracted and lithium-reinserted forms are characterizedby X-ray absorption (EXAFS and XANES) and incoherent inelastic neutron scattering (IINS)spectroscopies. Lattice hydroxyl groups are detected in the lithium-extracted sample; the chemicalreinsertion of lithium removes most of the hydroxyl groups, but some protons remain in the structuremainly as structural water. X-ray absorption spectroscopy at the manganese K-edge indicates a localspinel structure of Li_1.6Mn_1.6O₄ with manganese in oxidation state 4+. The structural arrangement andMn oxidation state remain unchanged when lithium is extracted and reinserted. The lithium sorptionoccurs by Li⁺/H⁺ ion exchange process, as for Li_1.33Mn_1.67O₄, the previously considered end member ofthe Li_1+xMn_2-xO₄ spinel lithium-rich series. Since the cation-to-anion ratio of Li_1.6Mn_1.6O₄ is not thatwhich is typical for a spinel, the new lithium-rich manganese oxide has a spinel structure with the extraLi⁺ probably in interstitial sites, although lithium cannot be located unequivocally from these results.