The effect of tetravalent titanium substitution in LiNi1-xTixO2 (0.025 ≤ x ≤ 0.2) system

Layered LiNi1-xTixO2 (0.025 less than or equal to x less than or equal to 0.2) containing tetravalent titanium ions was prepared by solid-state reaction at 750 degreesC under an oxygen stream. The products show highly ordered and phase-pure layered compounds. The structural integrity of the materials could be preserved by substituting Ti4+ ions to prevent impurity Ni2+ migration into lithium sites. The LiNi1-xTixO2 (0.025 less than or equal to x less than or equal to 0.2) cathode exhibits high reversible capacities (up to 240 mA h/g) and excellent cyclability (over 100 cycles) in the range 4.3-2.8 V at a current density of 0.2 mA/cm(2) (C/5 rate). One composition, LiNi0.975Ti0.025O2 showed the highest reversible capacity and energy density of all known layered LiNiO2 or LiCoO2 materials. The novel concept of substitution of tetravalent titanium is proven to be promising. (C) 2001 Elsevier Science B.V. All rights reserved.