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Influence of nickel content on the chemical bonding character of LiMn2-xNixO4 spinel oxides

Title
Influence of nickel content on the chemical bonding character of LiMn2-xNixO4 spinel oxides
Authors
Park D.H.Lim S.T.Hwang S.-J.Choy J.-H.Choi J.H.Choo J.
Ewha Authors
최진호황성주
SCOPUS Author ID
최진호scopus; 황성주scopus
Issue Date
2006
Journal Title
Journal of Power Sources
ISSN
0378-7753JCR Link
Citation
vol. 159, no. 2, pp. 1346 - 1352
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
A relationship between the chemical bonding nature of LiMn2-xNixO4 and 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 ∼620 cm-1, indicating enhancement of the average Mn oxidation states and reinforcement of the Mn{single bond}O bonds. This was confirmed by Mn K-edge X-ray absorption spectroscopic (XAS) analysis. Also, a new phonon line appeared at ∼495 cm-1 after 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 3 V 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 NiO6 octahedra. © 2006 Elsevier B.V. All rights reserved.
DOI
10.1016/j.jpowsour.2005.12.018
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자연과학대학 > 화학·나노과학전공 > Journal papers
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