Abstract: As a cathode material for lithium ion batteries, Co₃O₄ has attracted much attention due to its high theoretical specific capacity of 890 mA·h/g. In this paper, Co₃O₄ and expanded graphite self-assembled polyhedral composites (Co₃O₄-EG) were prepared by simple chemical solution method and heat treatment. When used as the anode material of lithium ion battery, the reversible capacity of Co₃O₄-EG composite electrode with the mass ratio of EG to Co₃O₄ of 1∶3 after 400 cycles at the current rate of 0.1 C is still as high as 418 mA·h/g, which is higher than that of other Co₃O₄-EG composite materials (The capacity is 273 mA·h/g after 190 cycles with a mass ratio of 1∶4 and 329 mA·h/g after 135 cycles with a mass ratio of 1∶5). And the discharge capacity of all Co₃O₄-EG composites is higher than that of pure Co₃O₄ (The capacity is 40 mA·h/g after 400 cycles). The nanostructure of Co₃O₄, the excellent electrical conductivity of expanded graphite and the synergistic effect of self-assembled polyhedron structure make Co₃O₄-EG composites have excellent lithium storage properties.