Fabrication of Co3O4 nanoparticles in thin porous carbon shells from metal–organic frameworks for enhanced electrochemical performance

Abstract

Cobalt oxides, typically Co₃O₄, have received considerable attention due to their high theoretical capacity as anode materials for Li-ion batteries. However, their poor electron conductivity and large volume change upon the insertion/removal of Li⁺ ions limit their practical application. Carbon coating is widely used to improve the electrochemical performance of materials and release the strain during the lithiation/delithiation processes, in which the thickness of the coating carbon shell has a vital role in determining the performance of the material. In this study, Co₃O₄ nanoparticles coated with a thin carbon shell are obtained from the metal–organic framework (MOF) precursor Co-MOF-74 via a sequential two-step carbonization process, where carbon oxides, e.g., CO₂, are used as the oxidation atmosphere in the second step. The carbon content and shell thickness are controlled by changing the calcination time. The electrode containing a certain carbon content (3.17 wt%) exhibits a capacity of 1137 mA h g⁻¹ after 100 cycles tested at 100 mA g⁻¹ between 0.005 and 3.0 V. This enhanced electrochemical performance is attributed to the well-dispersed nanosized Co₃O₄ particles and thin carbon shell coating on the electrode surface, which shorten the Li⁺ ion diffusion length and enhance the electron conductivity of the hybrid.