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首页> 外文会议>NATO Advanced Study Institute on New Trends in Intercalation Compounds for Energy Storage, Sep 22-Oct 2, 2001, Sozopol, Bulgaria >LATTICE DYNAMICS OF MANGANESE OXIDES AND THEIR INTERCALATED COMPOUNDS
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LATTICE DYNAMICS OF MANGANESE OXIDES AND THEIR INTERCALATED COMPOUNDS

机译：锰氧化物及其嵌入化合物的晶格动力学

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摘要

Manganese oxides with tunnel and layered crystal structures constitute a large family of porous materials from ultramicropore to mesopore. Most of the structural frameworks of the manganese dioxides (MD) consist of MnO_6 octahedral units shared by corners and/or edges. The excellent electrochemical properties of several MD phases have attracting much attention for positive electrode materials in lithium batteries. MnO_2 was originally developed as electrode in Leclanche cells and, recently as positive electrode for a primary Li cell, but extensive research has been undertaken during the last decade to develop rechargeable Li//MnO_2 cells. There is a wide variety of manganese dioxides, whose structures have been extensively investigated including natural (NMD) manganese dioxides. Among the MD, most attention has been focused on synthetic manganese dioxides prepared by either electrolytic (EMD) or chemical (CMD) method that belong to the nsutite (γ-MnO_2) group. The electrochemical behaviour of EMD compounds has been investigated by Ohzuku et al.[8]. Besides the γ-MnO_2 form, particular attention has been paid to other stoichiometric compounds. As an example, the sodium-free birnessite, MnO_(1.85)-0.7H_2O, displays a layered structure with larger interlayer distance and trigonal prismatic sites favourable for easy lithium insertion. Vibrational spectroscopy such as Raman scattering (RS) and Fourier transform infrared (FTIR) have proved valuable for the characterisation of lithiated transition-metal oxides used as electrode materials in rechargeable lithium batteries. Bulk manganese dioxides were analysed using Raman spectroscopy and infrared. A careful examination of the results published earlier by different authors and those that have more recently appeared shows discordance regarding the Raman spectra of oxides. This is mainly due to the fact that, under the laser beam, manganese compounds were unstable and suffered reduction reactions. It has been noticed that most of the manganese dioxides can be reduced to the stable phase Mn_3O_4 (hausmannite) with the formation of spinel zones at the laser impact point evidenced by the appearance of a strong RS peak at 650 cm~(-1). More reproducible results were obtained within IR results but the lack of careful examination of the structure makes useless some results. In this paper, the lattice dynamics of lithium manganese dioxides having various crystal structure are presented. The vibrational spectra of the LiMn_2O_4 are also studied using RS and FTIR techniques, which are capable of probing directly the near-neighbour environment of oxygen co-ordination around the lithium and manganese cations. Using the spectroscopic symmetry O_h~7, the normal modes of the spinel LiMn_2O_4 are discussed with the identification of the vibrations of Li cations with their oxygen neighbours.
机译：具有隧道和层状晶体结构的氧化锰构成了从超微孔到中孔的大量多孔材料。二氧化锰（MD）的大多数结构框架由角和/或边共享的MnO_6八面体单元组成。几种MD相的优异电化学性能已引起锂电池正极材料的广泛关注。 MnO_2最初是作为Leclanche电池的电极开发的，最近作为原Li电池的正极使用，但是在过去的十年中，已经进行了广泛的研究以开发可充电的Li // MnO_2电池。存在各种各样的二氧化锰，其结构已被广泛研究，包括天然（NMD）二氧化锰。在MD中，最受关注的焦点是通过电解（EMD）或化学（CMD）方法制备的合成二氧化锰，它们属于nsutite（γ-MnO_2）族。 Ohzuku等人[8]研究了EMD化合物的电化学行为。除了γ-MnO_2形式以外，还特别注意了其他化学计量的化合物。例如，无钠水钠锰矿MnO_（1.85）-0.7H_2O表现出层间距离较大的层状结构和有利于锂容易插入的三角形棱柱形部位。诸如拉曼散射（RS）和傅立叶变换红外（FTIR）之类的振动光谱已被证明对表征可充电锂电池中用作电极材料的锂化过渡金属氧化物具有重要意义。使用拉曼光谱和红外分析大块二氧化锰。仔细检查不同作者先前发表的结果以及最近发表的结果，发现关于氧化物的拉曼光谱不一致。这主要是由于以下事实：在激光束下，锰化合物不稳定且发生还原反应。已经注意到，大多数二氧化锰可以还原成稳定相Mn_3O_4（菱锰矿），并在激光冲击点形成尖晶石区，这在650 cm〜（-1）处会出现强RS峰。在IR结果中获得了更多可重复的结果，但是缺乏仔细检查结构的结果使得一些结果毫无用处。在本文中，提出了具有各种晶体结构的二氧化锂锰的晶格动力学。还使用RS和FTIR技术研究了LiMn_2O_4的振动光谱，该技术能够直接探测锂和锰阳离子周围氧配位的近邻环境。利用光谱对称性O_h〜7，讨论了尖晶石LiMn_2O_4的正态模，并确定了Li阳离子及其氧邻域的振动。

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