Hydrothermal synthesis of nanostructured Co3O4 materials under pulsed magnetic field and with an aging technique, and their electrochemical performance as anode for lithium-ion battery

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 4 T magnetic field consisted of large agglomerated spheres composed of numerous quasi-spherical nanoparticles with a typical diameter of ∼25 nm 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 ∼20 nm 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 407 mAh g⁻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.