On the origin of the 3.3 and 4.5 V steps observed in LiMn2O4-based spinels

Citation
Mr. Palacin et al., On the origin of the 3.3 and 4.5 V steps observed in LiMn2O4-based spinels, J ELCHEM SO, 147(3), 2000, pp. 845-853
Citations number
48
Categorie Soggetti
Physical Chemistry/Chemical Physics","Material Science & Engineering
Journal title
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
ISSN journal
00134651 → ACNP
Volume
147
Issue
3
Year of publication
2000
Pages
845 - 853
Database
ISI
SICI code
0013-4651(200003)147:3<845:OTOOT3>2.0.ZU;2-P
Abstract
Different series of LiMn2O4-based spinels were studied, all presenting two reduction steps at 4.5 and 3.3 V in addition to the "normal" spinel plateau s around 4 V. A correlation was found between the capacity recovered on the se additional steps, the manganese oxidation degree, and the cell parameter of a given spinel. By means of in situ synchrotron diffraction we were abl e to detect the appearance of a new set of diffraction peaks upon oxidation of the 3.3 V step at 3.95 V, that disappeared on subsequent reduction at 3 .3 V. Electron diffraction and high resolution electron microscopy studies on partially delithiated samples revealed the formation of double hexagonal layers upon oxidation, consistent with the additional peaks observed in th e in situ experiments. Finally, a model to explain the existence of the red ox steps at 4.5 and 3.95/3.3 V based on the creation of these double hexago nal layers is proposed. (C) 2000 The Electrochemical Society. S0013-4651(99 )07-060-3. All rights reserved.