Hydrated molybdenum-trioxides MoO3 . nH(2)O were synthesized via the condensation of molybdic acid in aqueous solutions. These hydrated oxides are studied by thermal analysis, X-ray diffraction and FTIR spectroscopy. The electrochemical properties, i.e. thermodynamics and kinetics, of lithium-intercalated MoO3 . nH(2)O cathodes are investigated in relation to their structure and morphology. These compounds show good charge-discharge cyclic behaviour at a capacity of below 1.5 e(-)/Mo. The electrochemical features of these materials are compared with those of other molybdic acids, i.e. MoO3 . (2/3)H2O, MoO3 . 1H(2)O and MoO3 . 2H(2)O. The chemical diffusion coefficient of Li+ ions reaches a value 3 X 10(-9)cm(2) s(-1) in MoO3 . (1/2)H2O materials.