Electron diffraction study of the layered liy (Ni0.425 Mn0.425 Co0.15) 0.88 O2 materials reintercalated after two different states of charge

Abstract

A long and irreversible plateau is observed for Li1.12 (Ni0.425 Mn0.425 Co0.15) 0.88 O2. The layered Liy (Ni0.425 Mn0.425 Co0.15) 0.88 O2 (y=0.93 and 0.73) materials were prepared by discharging to 3.2 V Li Liy (Ni0.425 Mn0.425 Co0.15) 0.88 O2 cells charged up to 4.4 V (beginning of the plateau) and 4.8 V (end of the plateau), respectively. The structure was investigated using the combination of X-ray and electron diffraction experiments to study a possible structural evolution upon cycling of the superstructure observed for the pristine material. The disappearance of the superlattice lines in the 19.5-34° (2 θCu) range in the X-ray diffraction pattern as well as that of the diffuse disorder scattering lines (or the extra spots) in the electron diffraction patterns were clearly observed for Li0.73 (Ni0.425 Mn0.425 Co0.15) 0.88 O2. These results revealed the loss of the 3 ahex. ×3 ahex. superstructure and thus of the cation ordering within the slabs when the Li Li1.12 (Ni0.425 Mn0.425 Co0.15) 0.88 O2 cells are charged to the end of the plateau. Moreover, other new diffuse disorder scattering lines were observed along the c* axis itself for the Li0.73 (Ni0.425 Mn0.425 Co0.15) 0.88 O2 material that has seen the plateau, which were attributed to local interslab space thickness variations. © 2007 The Electrochemical Society.