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Thermal stability of Li1-ΔM0.5Mn1.5O4 (M = Fe, Co, Ni) cathodes in different states of delithiation Δ

2013; Royal Society of Chemistry; Linguagem: Inglês

10.1039/c3ra40356d

2046-2069

Aiswarya Bhaskar, W. Gruner, Daria Mikhailova, Helmut Ehrenberg,

Advanced Battery Technologies Research

The thermal stability of sol–gel synthesized Li1−ΔM0.5Mn1.5O4 (M = Fe, Co, Ni) electrodes with different degrees of delithiation were analyzed with TG-DSC and in situ synchrotron diffraction under an Ar atmosphere and compared. The onset temperatures for structural degradation are dependent on the amount of lithium 1−Δ in the sample. The Li1−ΔFe0.5Mn1.5O4 electrode exhibited the highest thermal stability among the three materials with different dopant M. The reason for this difference is discussed with respect to the oxidation states of the transition metals. The mechanism of degradation for M = Fe, Co was found to be through gas evolution, mainly CO2 and O2, and the carbon conductive additive was found to play a major role in the thermal degradation process. For delithiated Li1−ΔNi0.5Mn1.5O4 the temperature induced degradation includes phase separation into Mn3O4 with spinel structure and LixNi1−xO with rock-salt structure together with oxygen and carbon dioxide release.