Characteristics of twins in Li(Ni0.67Co0.33)O2 as a cathode material for lithium-ion batteries

Based on XRD, SEM and TEM studies of the obtained Li (Ni0.67Co0.33) O2 phase from sintering, the results show that the space group of the phase is R 3 ¯ m , which belongs to the rhombohedral lattice, and there are observed many twins with 1 1 ¯ 0 4 ¯ as twining plane in the crystal. When Li (Ni0.67Co0.33) O2 phase is forming twins with 1 1 ¯ 0 4 ¯ as twinning plane, the octahedrons in the twinning plane need not to make any adjustment. At the same time, the 1 1 ¯ 0 4 ¯ interface f is close-packed plane for Li, (Ni, Co) and O atoms, moreover, the interface energy maybe the lowest if the 1 1 ¯ 0 4 ¯ plane is used as an interface. Crystallographic analysis showed that when the twins with 1 1 ¯ 0 4 ¯ as twinning plane were formed in Li (Ni0.67Co0.33) O2 phase, orientation relationship between the two twin sub-grains can also be considered as two variants of the orientation domain.