Structural studies of Li_1.2Mn_0.55Ni_0.15Co_0.1O₂ electrode material

A pristine Li-rich layered electrode material with composition Li_1.2Mn_0.55Ni_0.15Co_0.1O₂ was characterized by X-ray diffraction, transmission electron microscopy, and scanning transmission electron microscopy to determine whether it is a coherent mixture of monoclinic C2/m Li₂MO₃ and trigonal [Formula: see text] LiMO₂ phases or a solid solution of the monoclinic phase. Contradictory results have been previously reported which can be attributed to the complexity and structural similarity of the monoclinic and trigonal phases. We resolved this uncertainty by combining diffraction and imaging techniques that probe complimentary length scales. Our results demonstrate that the structure is primarily monoclinic, supporting the solid solution model, although near surface structural alterations were also observed.