An antimony based anode material for a rechargeable battery comprises nanoparticles of composition SbM x Oy wherein M is a further element selected from the group 5 consisting of Sn, Ni, Cu, In, Al, Ge, Pb, Bi, Fe, Co, Ga, with 0 ‰¤ x < 2 and 0 ‰¤ y ‰¤ 2.5+2x. The nanoparticles form a substantially monodisperse ensemble with an average size not exceeding a value of 30 nm and by a size deviation not exceeding 15%. A method for preparing the antimony based anode material is carried out in situ in a non-aqueous solvent and starts by reacting an antimony salt and an organometallic amide reactant and oleylamine.