Disproportionation of stoichiometric LiMn2O4 on annealing in oxygen |
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Authors: | P Strobel G Rousse C Masquelier |
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Institution: | a Laboratoire de Cristallographie CNRS, BP 166, 38042 Grenoble Cedex 9, Franceb Laboratoire de Physique des Milieux Condensés, Université P; et M. Curie, 75252Paris cedex 05, Francec Laboratoire de Réactivité et Chimie des Solides, Université de Picardie Jules Verne, 80039 Amiens cedex 9, France |
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Abstract: | The evolution of stoichiometric LiMn2O4 upon annealing under oxygen pressures in the range 0.2-5 atm at moderate temperature (450°C) was studied with a combination of thermogravimetry, X-ray and neutron diffraction. It is shown that such treatments result in a slight, but significant mass increase. Structural analyses show that the resulting spinel is a manganese-deficient spinel phase with lower cell parameter and higher manganese valence, and that the expelled manganese forms Mn2O3. The presence of this second phase, which was not identified in a recent study of oxygen annealing on this compound (Nakamura and Kajiyama, Solid State Ionics 133 (2000) 195), is compatible with the initial stoichiometry and does not require any oxygen vacancies in the initial LiMn2O4, as supposed earlier. The most likely formula of the resulting lithium-rich spinel with increased manganese valence is Li(Mn2−ε□ε)O4 with ε in the range 0.02-0.03 at 5 atm O2. |
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Keywords: | Li-Mn-O system Spinel Oxygen annealing |
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