Comments on the structural complexity of lithium-rich Li1+xM1−xO2 electrodes (M = Mn, Ni, Co) for lithium batteries

Structural features of lithium-rich Li1+x[Mn0.5Ni0.5]1−xO2 and Li1+x[Mn0.333Ni0.333Co0.333]1−xO2 electrode samples (0 ⩽ x ⩽ 0.15), prepared in-house and by an industrial company, have been determined by powder X-ray diffraction, high-resolution transmission electron microscopy imaging, convergent beam electron diffraction and nuclear magnetic resonance. The results are discussed broadly in terms of the complexity of intergrown and disordered xLi2MnO3 · (1 − x)LiMO2 systems, particularly when cobalt is combined with manganese and nickel in the transition metal layers of the LiMO2 component. It is proposed that the addition of trivalent cobalt to the transition metal layers in the Li1+x[Mn0.333Ni0.333Co0.333]1−xO2 compounds at the expense of tetravalent manganese and divalent nickel reduces the amount and size of the Li2MnO3-like regions, rendering them essentially amorphous to X-ray diffraction.