A novel lithium–oxygen battery exploiting PYR14TFSI–LiTFSI as ionic liquid-based electrolyte medium is reported. The Li/PYR14TFSI–LiTFSI/O2 battery was fully characterized by electrochemical impedance spectroscopy, capacity-limited cycling, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The results of this extensive study demonstrate that this new Li/O2 cell is characterized by a stable electrode–electrolyte interface and a highly reversible charge–discharge cycling behavior. Most remarkably, the charge process (oxygen oxidation reaction) is characterized by a very low overvoltage, enhancing the energy efficiency to 82%, thus, addressing one of the most critical issues preventing the practical application of lithium–oxygen batteries.