Rechargeable Li-O-2 batteries are promising candidates for electric vehicles due to their high energy density. However, the current development of Li-O-2 batteries demands highly efficient air cathode catalysts for high capacity, good rate capability, and long cycle life. In this work, a hydrothermal-calcination method is presented to prepare a composite of Co3O4 hollow nanoparticles and Co organic complexes highly dispersed on N-doped graphene (Co-NG), which acts as a bifunctional air cathode catalyst to optimize the electrochemical performances of Li-O-2 batteries. Co-NG exhibits an outstanding initial discharge capacity up to 19 133 mAh g(-1) at a current density of 200 mA g(-1). In addition, the batteries could sustain 71 cycles at a cutoff capacity of 1000 mAh g(-1) with low overpotentials at the current density of 200 mA g(-1). Co-NG composites are attractive as air cathode catalysts for rechargeable Li-O-2 batteries.