Co3O4 nanoparticle samples were prepared as anode materials for lithium-ion batteries by the hydrothermal synthesis method without magnetic field (Co3O4-0T), under pulsed magnetic field (Co3O4-4T), and by using an aging technique (Co3O4-Aging), respectively. The morphology and structural properties of the Co3O4 nanoparticles were investigated by field-emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD). FE-SEM measurements demonstrated that the Co3O4 sample formed under a 4T magnetic field consisted of large agglomerated spheres composed of numerous quasi-spherical nanoparticles with a typical diameter of ∼25nm and had more compact and smoother surfaces compared to a reference sample prepared without magnetic field. After the aging process, large Co3O4 hollow spheres composed of numerous spherical nanoparticles with a typical diameter of ∼20nm were formed. Electrochemical measurements showed that Co3O4 materials prepared by the aging technique (Co3O4-Aging) yielded the best electrochemical performance compared with the other samples. Capacities were maintained at 274, 348, and 407mAhg−1 up to 100 cycles for the Co3O4-0T, Co3O4-4T, and Co3O4-Aging materials, which are about 26, 27, and 30% of initial discharge capacities, respectively. The capacity loss is in the order of Co3O4-Aging<Co3O4-4T<Co3O4-0T. Thus, the morphology affects not only the discharge capacity, but also the cycling stability of Li-ion batteries.