The Effect on Cathode Performance of Oxygen Non-Stoichiometry and Interlayer Mixing in Layered Rock Salt LiNi0.8Mn0.1Co0.1O2-δ

Abstract

Oxygen non-stoichiometry in layered rock salt structure cathodes can have a major deleterious effect on their performance in Li batteries. The effect of preparation conditions - temperature, atmosphere and cooling rate - on oxygen non-stoichiometry and consequent interlayer cation mixing in the layered rock salt material LiNi0.8Mn0.1Co0.1O2-δ has been investigated using a combination of X-Ray powder diffraction, including Rietveld refinement and thermogravimetry. Oxygen content varies over the approximate range ∼0≤ δ ≤ ∼ 0.23; oxygen deficiency is greatest in samples fired at high temperatures in N2. Interlayer mixing occurs as a direct consequence of oxygen deficiency and leads to reduced cathode capacity and performance; samples with least oxygen deficiency and most cation order were obtained on firing in O2 at ∼900–950°C. Attention to the optimisation of oxygen stoichiometry should be an important generic consideration during cathode preparation.