Structural and Electrochemical Study of New LiNi_0.5Ti<i>_x</i>Mn_1.5-<i>_x</i>O₄ Spinel Oxides for 5-V Cathode Materials

Abstract

New LiNi0.5TixMn1.5-xO4 (0.05 ≤ x ≤ 0.6) spinel oxide materials have been obtained. The cubic unit cell parameter increases with the substitution of manganese by titanium in the octahedrally coordinated 16d sites, as evidenced by X-ray and neutron diffraction studies. For Ti-free LiNi0.5Mn1.5O4 up to x = 0.10, a decrease in the line broadening of the X-ray diffraction profiles is observed. For x > 0.1, X-ray line broadening and a progressive loss of resolution in the FTIR spectral profiles are observed. The presence of small amounts of Ti (x = 0.05 and 0.1) yields a net improvement of the electrochemical performance, whereas a deterioration of the reversible capacity is observed for large Ti contents. The electrochemical oxidation mechanism involves the appearance of two or three cubic phases with different lattice parameters, as evidenced by ex situ XRD of electrodes prepared at different depths of the first charge.