Anisotropic Co3O4 porous nanocapsules toward high-capacity Li-ion batteries

Abstract

Anisotropic column-shaped porous Co₃O₄ nanocapsules were successfully synthesized via a solvothermal route using poly(vinyl pyrrolidone) (PVP) as capping reagent and final heat treatment in air. These anisotropic polycrystalline nanocapsules with the length of ∼1 μm and the diameter of ∼400 nm were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. Detailed proof indicated that the process of CoCO₃ precursor growth was dominated by a nucleation and growth, self-organization, and then Ostwald ripening growth mechanism. These column-shaped Co₃O₄ nanocapsules integrate two beneficial features: hollow cavity and porous shell. When evaluated for Li-ion batteries, they exhibit high reversible capacity (over 1000 mA h g⁻¹) and good cycle performance.