The Effect on Cathode Performance of Oxygen Non-Stoichiometry and Interlayer Mixing in Layered Rock Salt LiNi_0.8Mn_0.1Co_0.1O_2-δ

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 LiNi 0.8 Mn 0.1 Co 0.1 O 2-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 N 2 . 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 O 2 at ∼900–950°C. Attention to the optimisation of oxygen stoichiometry should be an important generic consideration during cathode preparation.