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

Abstract

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 R3¯m, which belongs to the rhombohedral lattice, and there are observed many twins with 11¯04¯ as twining plane in the crystal. When Li (Ni0.67Co0.33) O2 phase is forming twins with 11¯04¯ as twinning plane, the octahedrons in the twinning plane need not to make any adjustment. At the same time, the 11¯04¯ interface f is close-packed plane for Li, (Ni, Co) and O atoms, moreover, the interface energy maybe the lowest if the 11¯04¯ plane is used as an interface. Crystallographic analysis showed that when the twins with 11¯04¯ 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.