NOVELTY - Non-aqueous electrolyte solution comprises a lithium salt, and solvent comprises ethylene carbonate, propylene carbonate, gamma-butyrlactone, N-methylpyrrolidinone, tetramethylene sulfone, triethylene glycol dimethyl ether, tetraethylene glycol, and/or dimethyl ether.    USE - As non-aqueous electrolyte solution, used for metal/oxygen battery (claimed).    ADVANTAGE - The non-aqueous electrolyte lithium/oxygen battery that has a higher discharge voltage than the prior art; and has the advantage of protecting a non-aqueous electrolyte battery from cathodic overcharge exotherms.    DETAILED DESCRIPTION - A non-aqueous electrolyte solution comprises a lithium salt with molecular formula LiBF3X, and a solvent mixture which comprises: (a) a first solvent and a second solvent; (b) where the first solvent comprises ethylene carbonate, propylene carbonate, gamma-butyrlactone, N-methylpyrrolidinone, tetramethylene sulfone, triethylene glycol dimethyl ether, tetraethylene glycol, and/or dimethyl ether; (c) where the first solvent has a dielectric constant of greater than 30, a boiling point of greater than 200 degrees C, and a viscosity of greater than 1.5 centipoises at 25 degrees C; (d) where the second solvent comprises cyclic ethers, linear ethers having a molecular formula CmH2m+1OCnH2n+1, and linear carbonates having a molecular formula CxH2x+1OC(O)OCyH2y+1; (e) further second solvent has viscosity of less than 0.8 centipoises at 25 degrees C, a boiling point of less than 90 degrees C, and a dielectric constant of less than 10; (f) the ratio of the first solvent in the solvent mixture varies from 10-90 vol.%; (g) the ratio of the second solvent in the solvent mixture varies from 10-90% vol.%; and (h) where the concentration of the lithium salt is 0.1-1.5 (preferably 0.5-1) molal.    X=F, Cl, Br, or I;    m and n=1-4;    x and y=1-4.    An INDEPENDENT CLAIM is included for metal/oxygen battery comprising (a) a lithium anode; (b) an air cathode, (c) a non-aqueous electrolyte solution; and (d) a microporous separator placed between the lithium anode and the air cathode.