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.