Influence of nickel content on the chemical bonding character of LiMn2-xNixO4 spinel oxides
Influence of nickel content on the chemical bonding character of LiMn2-xNixO4 spinel oxides
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DOI：
10.1016/j.jpowsour.2005.12.018
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发表时间：
2006-09
影响因子：
9.2
通讯作者：
D. Park;Seung Tae Lim;Seong‐Ju Hwang;J. Choy;Junghyun Choi;J. Choo
中科院分区：
文献类型：
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作者：
D. Park;Seung Tae Lim;Seong‐Ju Hwang;J. Choy;Junghyun Choi;J. Choo
系统地研究了LiMn 2 − xNixO 4的化学键性质与Ni含量之间的关系。根据X射线衍射分析，镍取代的锰酸锂以立方尖晶石结构结晶，在0≤x≤0.4的本取代范围内没有形成任何杂质相如NiO。显微拉曼光谱分析表明，Ni的取代导致两条主要声子谱线的强度和能量增加，分别位于580和620 cm −1，这表明Mn的平均氧化态增强，MnO键增强。这通过Mn K边X射线吸收光谱（XAS）分析证实。此外，在Ni取代后，出现了一条新的声子线，位于495 cm − 1处，这可以被认为是LiMn 2 O 4的Ni-O振动模式，而不是T2 g（2）模式。Ni K边XAS和显微拉曼分析清楚地表明，二价镍离子存在于立方尖晶石晶格的八面体位置，而没有显着的变化，在化学环境中的Ni含量。在这方面，严重Ni取代的化合物的3V区域的电化学性能差是不是由于在局部环境中的Ni离子与Ni含量的变化，但取代的NiO 6八面体的结构稳定性低。
A relationship between the chemical bonding nature of LiMn2−xNixO4and the Ni content has been systematically investigated. According to X-ray diffraction analysis, nickel-substituted lithium manganates crystallize with a cubic spinel structure without the formation of any impurity phase such as NiO in the present substitution range of 0≤x≤0.4. Micro-Raman analysis showed that Ni substitution gave rise to an increase in the intensities and energies of the two main phonon lines at ∼580 and ∼620cm−1, indicating enhancement of the average Mn oxidation states and reinforcement of the MnO bonds. This was confirmed by Mn K-edge X-ray absorption spectroscopic (XAS) analysis. Also, a new phonon line appeared at ∼495cm−1after the Ni substitution, which can be assigned as an Ni–O vibration mode rather than as a T2g(2) mode of LiMn2O4. Ni K-edge XAS and micro-Raman analyses clearly demonstrate that divalent nickel ions existed in the octahedral sites of the cubic spinel lattice without a significant change in the chemical environment with the Ni content. In this regard, the poor electrochemical performance of heavily Ni-substituted compounds for the 3V region is not attributable to the variation in the local environment of Ni ions with the Ni content, but to the low structural stability of the substituted NiO6octahedra.