A Study of Stacking Faults and Superlattice Ordering in Some Li-Rich Layered Transition Metal Oxide Positive Electrode Materials

Li-rich layered transition metal oxides such as Li[Li 0.2 Ni 0.2 Mn 0.6 ]O 2 have in-plane ordering between the excess Li atoms and the transition metal (TM) atoms in the transition metal layer. The √3a × √3a superlattice in the TM layer causes superlattice Bragg peaks in their X-ray diffraction patterns. This article describes the relation between the metal composition of the materials, stacking faults and superlattice ordering. The XRD patterns were fitted with a program called FAULTS, which treats the effect of stacking faults on the superlattice peak shapes. The superlattice peak positions of Li[Li 1/3-2x/3 Ni x Mn 2/3-x/3 ]O 2 materials changed monotonically with Ni content (x), as did the positions of the main diffraction peaks of the base structure. This proves that the superlatices peaks originate from the Li[Li 1/3-2x/3 Ni x Mn 2/3-x/3 ]O 2 solid solution and are not caused by any domains of second phase such as Li 2 MnO 3 . Fitting the XRD patterns with FAULTS revealed that the stacking fault probability increased monotonically with Ni content.