As a new approach to the development of advanced Li/air batteries, a carbon-sphere/Co3O4 nanocomposite is introduced as a catalyst for the air electrode. Co3O4 nanoparticles are dispersed homogeneously on the surface of carbon spheres in an attempt to increase the carbon/catalyst contact area acting as the catalytic active site during the electrochemical reaction. A high discharge capacity, relatively stable reversibility, and low overpotential are observed in electrochemical tests of an electrode containing this carbon-sphere/Co3O4 nanocomposite. This indicates that the carbon-sphere/Co3O4 composite is a promising catalyst for the air electrode of Li/air batteries.