Changes in the structure and physical properties of Li1−yNi0.5Mn0.4Ti0.1O2 (y=0 and 0.5)

Li1−yNi0.5Mn0.4Ti0.1O2 (y=0 and 0.5) was synthesized and characterized using X-ray diffraction, XAFS, and SQUID measurements. The samples were single-phase and adopted the α-NaFeO2 structure. Li1−yNi0.5Mn0.4Ti0.1O2 (y=0 and 0.5) can be represented as Li(Ni2+0.5Mn4+0.4Ti4+0.1)O2 and Li0.5(Ni3+0.5Mn4+0.4Ti4+0.1)O2, respectively. Structural analysis demonstrated that the lattice parameter a decreased from 2.895 to 2.856 Å, the lattice parameter c increased from 14.317 to 14.509 Å, and the Ni–O bond length decreased from 2.06 to 1.94 Å with de-lithiation. The low occupation of Ni on the 3a site was confirmed from the ferromagnetic behavior caused by the 180° Ni2+(3a)–O–Mn4+(3b)–O–Ni2+ (3a) superexchange interaction. These results indicated that lithium de-intercalation from LiNi0.5Mn0.4Ti0.1O2 was controlled mainly by changing the valence state of Ni from 2+ to 3+.