Abstract: A lithium and vanadium oxide is described having the formula Li1+xV3O8, wherein 0.1?x?0.25. The oxide has a monoclinic crystalline structure and comprises non-agglomerated grains in the form of monocrystalline pellets having a length L of between 1 and 100 ?m, a width I such that 4<L/I<100, and a thickness e such that 4 L/e<100, with e<1, the elongation axis of said pellets being axis b of the monoclinic cell. The oxide may be prepared by mixing the Li and V precursors, without grinding or compression, heating said mixture to 565° C.-585° C. and deagglomerating the product obtained. The oxide is suitable for use as an active material for the positive electrode of a lithium battery.