Fig. 3: Crystal structure of Li-rich Mn oxide-based layered cathode materials.

In situ XRD of the pristine Li1.2Mn0.6Ni0.2O2 (a) and Li1.2Mn0.6Ni0.2O2-δ (M-LRO) samples (b) in the first cycle. The left patterns are 2D contours, and the asterisk label indicates the diffraction peaks of Be in the battery window. The vertical dotted lines illustrate the reversible and irreversible change of the (101) peak for the M-LRO and pristine samples. The right spectra show the initial charge–discharge curves. The term a.u. means arbitrary units.