Abstract: The invention relates to a process for preparing a core-shell structured lithiated manganese oxide, comprising the steps of providing spinel LiMxMn2-xO4 particles, where M is one or more metal ions selected from the group consisting of Li, Mg, Cr, Al, Co, Ni, Zn, Cu, and La, and 0?x<1, as core particles, and subjecting the spinel particles to a heat-treatment with a reactive chemical reagent in the form of liquid or gas to form a shell layer on the surface of the core particles, and to the prepared core-shell structured lithiated manganese oxide, and its use as a cathode material for a lithium ion battery