Atomic Structure of a Lithium-Rich Layered Oxide Material for Lithium-Ion Batteries: Evidence of a Solid Solution

Li[Li 0.2 Ni 0.2 Mn 0.6 ]O 2, which is a cathode material for Li-ion batteries with enhanced capacity, has been examined, for the first time, with a combination of aberration-corrected scanning transmission electron microscopy (STEM), STEM computer simulations, and diffraction scanning transmission electron microscopy (D-STEM). These techniques, in combination with X-ray diffraction (XRD) and conventional electron diffraction (ED), indicate that this material is composed of a solid solution with C 2/ m monoclinic symmetry and multiple planar defects. In addition, we show that XRD and ED alone can give misleading information and cannot resolve the structure of these materials without the additional use of the aforementioned techniques.