Abstract: The grains of LiMn₂O₄ and LiM_xMn_2-xO₄ (M=Li, Ni) were coated with LiCoO₂ by using sol-gel
process. XRD and EPMA studies confirme the presence of a Co-rich spinel LiMn_2-xCo_xO₄ layer on the surface of Li_xMn_2-xO₄ grains
and the content of Co decreases gradually from the surface to the core of spinel grains. Furthermore, the amount of Mn³⁺ in the surface layer is less than in the core, so
the possibility of Mn dissolution decreases. The surface treatment is effective in reducing the rate of Mn dissolution into electrolyte and
improving cyclability of spinel LiM_xMn_2-xO₄ cathode materials. After bulk Ni-doped spinel LiNi_0.1Mn_1.9O₄ coated with
LiCoO₂, the cyclability of the material is better than that of pure spinel LiMn₂O₄and just only cations doped.

Key words: lithium ion batteries, cathode materials, LiM_xMn_2-xO₄, surface modification