Thermal Stability of Lithium Nickel Oxide Derivatives. Part II:  Li<i>_x</i>Ni_0.70Co_0.15Al_0.15O₂ and Li<i>_x</i>Ni_0.90Mn_0.10O₂ (<i>x</i> = 0.50 and 0.30). Comparison with Li<i>_x</i>Ni_1.02O₂ and Li<i>_x</i>Ni_0.89Al_0.16O₂

Abstract

The thermal degradation mechanism of Li x Ni 0.70 Co 0.15 Al 0.15 O 2 and Li x Ni 0.90 Mn 0.10 O 2 ( x = 0.50 and 0.30) was studied by thermal gravimetric analysis coupled with mass spectrometry. Correlation with in situ X-ray diffraction experiments was then achieved to determine the degradation mechanism and to explain the differences in thermal stability observed depending on the material composition. The degradation occurs in two steps: a first transition between the lamellar phase and a spinel-type phase, and then a second transition between the pseudo-spinel phase and a NiO-type phase through a highly disordered R 3̄ m phase. Comparison of the thermal stability of the four materials shows that the addition of cobalt in the aluminum partial substituted materials improves the stability, particularly during the first step. The manganese partial substitution for nickel appears to improve the stability of the pseudo-spinel-type phase in comparison with Li x NiO 2 phases. The general thermal behavior of these deintercalated materials is discussed from the solid-state chemistry point of view.