Simple pyrolysis of cobalt alginate fibres into Co₃O₄/C nano/microstructures for a high-performance lithium ion battery anode

Cobalt tetroxide (Co₃O₄) has attracted much attention as a promising anode material for rechargeable lithium-ion batteries (LIBs) owing to its high theoretical capacity (890 mA h g^-1). However, its poor electronic conductivity and weak ability to accommodate large volume changes during a repeated charging-discharging process, which results in the poor cycling performance, have hindered the practical application of Co₃O₄. In this article, Co₃O₄/C fibres were prepared by simple pyrolysis of wetspun cobalt alginate fibres. The composites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). It was found that the resulting material possesses a unique hierarchical nano/microstructure in which Co₃O₄ nanoparticles (NPs) are capsulated in a micro-sized carbonaceous fibrous matrix. This nano/microstructure can combine the merits of the Co₃O₄ nanostructure and the carbonaceous microfibre matrix, and thus exhibits a high reversible capacity of 780 mA h g^-1 at 89 mA g^-1 after 100 cycles as well as excellent cycling stability and rate performance when used as an anode material. This finding could open up a new direction in sustainable use of natural seaweed resources as new energy storage materials.