Li-Mn-O oxides were synthesized by mechanochemistry from a stoichiometric mixture of Li2O and MnO2 using various grinding times (0 < t(milling) < 15 h). X-ray diffraction patterns of the ground samples (t(milling) < 10h) exhibit the same features as LiMn2O4 spinel structure (SG: Fd3m) with, however, a slight discrepancy in the lattice parameter (a(cub)) suggesting a non-stoichiometry of the Li-Mn-O oxides. a(cub) increases with milling time to reach for 8 h of grinding a value of 8.24 Angstrom similar to stoichiometric LiMn2O4. As a matter of fact, after 8 h of milling, mechanosynthesized Li-Mn-O spinel-type oxide shows quasi-identical electrochemical performances as high temperature LiMn2O4 ground for 1 h.