Alkali metal-oxygen batteries promise high gravimetric energy densities but suffer from low rate capability, poor cycle life and safety hazards associated with metal anodes. Here we describe a safe, high-rate and long-life oxygen battery that exploits a potassium biphenyl complex anode and a dimethylsulfoxide-mediated potassium superoxide cathode. The proposed potassium biphenyl complex-oxygen battery exhibits an unprecedented cycle life (3,000 cycles) with a superior average coulombic efficiency of more than 99.84% at a high current density of 4.0 mA cm-2. We further reduce the redox potential of biphenyl by adding the electron-donating methyl group to the benzene ring, which successfully achieved a redox potential of 0.14 V versus K/K+. This demonstrates the direction and opportunities to further improve the cell voltage and energy density of the alkali-metal organic-oxygen batteries.