Electrochemical properties of micron-sized, spherical, meso- and macro-porous Co3O4 and CoO-carbon composite powders prepared by a two-step spray drying process.

Micron-sized, spherical, meso- and macro-porous Co3O4 and CoO-carbon composite powders were prepared via a simple two-step spray drying process. The CoO-carbon composite powders, in which homogeneous mixing of the metal oxide and carbon components was achieved using the first spray drying process, were wet milled to produce the slurry for the second spray drying process. Co3O4 and CoO-carbon composite powders with mean particle sizes of 4.4 and 4.7 μm were respectively obtained by spray-drying the slurry after post-treatment at 400 °C under air and nitrogen atmospheres. Meso- and macro-pores were uniformly distributed inside the Co3O4 and CoO-carbon composite powders. The CoO-carbon composite powders exhibited discharge capacities of 882 and 855 mA h g(-1) at a high constant current density of 1400 mA g(-1) for the 2(nd) and 100(th) cycles. The discharge capacities of the Co3O4 powders at the 2(nd) and 100(th) cycles were 970 and 644 mA h g(-1). With stepwise increment in the current density from 500 to 5000 mA g(-1), the discharge capacities of the CoO-carbon composite powders decreased slightly from 985 to 698 mA h g(-1). The superior rate and cycling performances of the CoO-carbon composite powders are ascribed to their meso- and macro-porous structures and carbon components.