Li–O2 cell is considered as an ideal choice for the electric vehicles due to its high energy density, but is now suffering from the large charge polarization and low practical capacity. In this context, three-dimensional network macro-porous CoO synthesized via a sol–gel method is applied as an efficient catalyst in Li–O2 cells to alleviate this situation. Compared to KB (Ketjen black EC600JD) based cells, the CoO/KB based cell exhibits much improved electrochemical performance at various current densities, including flatter discharge/charge plateau, lower polarization and higher specific capacity. In addition, the CoO/KB based cell maintains the discharge capacity up to 4500 mAh g−1 CoO/KB after being cycled at 0.1 mA cm−2 for 16 days under O2 atmosphere. This excellent electrochemical performance is attributed to the high catalytic activity and abundant macro-pores of our home-made CoO. This strategy of designing CoO might be a feasible way to obtain the Li–O2 cell with low polarization and high capacity.