Unravelling high volumetric capacity of Co3O4 nanograin-interconnected secondary particles for lithium-ion battery anodes

Abstract

The development of high-tap density electrode materials that can simultaneously achieve stable electrochemical performance at high charge/discharge rates is critically in demand. Herein, we propose an innovative material design that can offer high tap density and excellent rate capabilities by using Co₃O₄ nanograin-interconnected secondary particles (Co₃O₄ NISPs). By taking advantage of a conversion reaction that forms Co from Co₃O₄, we demonstrate that Co₃O₄ NISPs are capable of creating a number of metallic Co sites along with a number of vacant sites in-between nanograins. Electrochemical tests that reveal reduced internal cell resistance and more accessible Li diffusion are achieved for Co₃O₄ NISPs compared with Co₃O₄ nanoparticles (NPs). Additionally, in situ X-ray diffraction (XRD) analyses, electron energy loss spectroscopy (EELS), and density functional theory (DFT) calculations reveal that the insulating intermediate product (CoO) is formed less on the Co₃O₄ NISPs, which can enhance the charge transport. Attributed to the combinatorial effects of Co₃O₄ nanograins that form metallic Co upon conversion and secondary particles that enable high tap density, Co₃O₄ NISPs show the most outstanding volumetric capacity (2167.3 mA h cm⁻³ at a current density of 500 mA g⁻¹) among spinel-type metal oxide electrode materials researched so far.