Structural properties and application in lithium cells of Li(Ni sub(0.5)Co sub(0.5)) sub(1-y)Fe sub(y)O sub(2) (0 less than or equal to y less than or equal to 0.25) prepared by sol-gel route: Doping optimization

Layered Li(Co sub(0.5)Ni sub(0.5)) sub(1-y)Fe sub(y)O sub(2) (0.0 less than or equal to y less than or equal to 0.25) oxides were prepared by citric-acid assisted sol-gel method. Elemental and structural properties were investigated by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman scattering (RS) and Mossbauer spectroscopy, and magnetometry. EDX images show a homogeneous distribution of Fe ions. XRD and RS spectroscopy reveal that the materials crystallize as a LiNiO sub(2)single bond LiCoO sub(2)single bond LiFeO sub(2) solid solution with the typical rhombohedral alpha -NaFeO sub(2) structure (R View the MathML source 3[macr] m S.G.) up to y = 0.2 at which composition a secondary phase was observed. For y > 0.2 the XRD results show the appearance of the alpha -LiFeO sub(2) phase with the cubic structure (Fm3m S.G.). The degree of cation mixing investigated by XRD analysis and magnetic measurements is z < 0.04, for y < 0.2. Electrochemical tests of Li(Co sub(0.5)Ni sub(0.5)) sub(1-y)Fe sub(y) O sub(2) (0.0 less than or equal to y less than or equal to 0.1) oxides in lithium cells show the influence of iron substitution. The best results have been obtained for the composition y(Fe) = 0.05, where the electrical conductivity is maximum. A specific capacity 32 mAh g super(-1) is maintained at 8C rate.