The Li-O₂ battery provides the highest energy density among all rechargeable battery systems. To date, the large over-potentials during the oxygen reduction reaction and oxygen evolution reaction lead to low round-trip efficiency and short cycle life. Herein, we report a Li-O₂ battery with outstanding performance. Application of a bi-functional organic catalyst, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA), significantly lowered the charge potential to 3.73 V and increased the discharge potential to 2.75 V. PTMA facilitates both efficient formation and oxidation of Li₂O₂ through its n- and p-doping ability coupled with superior catalytic activity. Furthermore, PTMA effectively coats the surface of the carbon electrodes, which suppresses side-reactions between carbon and the electrolyte leading to enhanced lifetimes.