Triethylene glycol dimethyl ether (G3) is evaluated as an electrolyte solvent for non-aqueous lithium-oxygen (Li-O-2) batteries. A liquid electrolyte of 1 M LiTFSI in G3 shows lower viscosity, higher oxygen solubility and diffusion, higher ionic conductivity and lithium ionic transference number compared to the conventional liquid electrolyte of 1 M LiTFSI in tetraethylene glycol dimethyl ether (G4). Then the Li-O-2 battery using the G3-based electrolyte shows better cycling stability and higher rate capability compared to the battery using the G4-based electrolyte. At a higher current density of 2.5 A g(carbon)(-1), the discharge capacity of the battery using the G3-based electrolyte is about 1472 mAh g(carbon)(-1), which is about four times higher than that of the battery using the G4-based electrolyte. At current density of 1 A g(carbon)(-1) with a fixed capacity of 1000 mAh g(carbon)(-1), the battery using the G3-based electrolyte can be operated stably for 80 cycles, while only 20 cycles are achieved by using the G4-based electrolyte. Therefore, we think the G3-based electrolyte could be a proper alternative electrolyte to the conventional G4-based electrolyte for the development of Li-O-2 batteries. (C) 2017 The Electrochemical Society. All rights reserved.