Identification of electrolytes compatible with both electrodes of a nonaqueous Li/O-2 battery is a considerable challenge. One solvent of interest, N,N-dimethylacetamide (DMA), has been shown to be stable toward the reactions of the air electrode, but decomposes rapidly when exposed to Li metal. Herein we investigate the electrochemical behavior of lithium metal electrodes in an electrolyte consisting of DMA and lithium nitrate, a combination that has been shown to have a dramatic effect on the cycle life of Li/O-2 cells. Electrochemical impedance spectroscopy, in situ pressure analysis, mass spectrometry, scanning electron microscopy and theoretical calculations are used to study the electrode/solution interface. Remarkably efficient, long-term Li metal cycling in DMA is reported through the cooperative effect of dissolved oxygen and lithium nitrate. (C) 2013 The Electrochemical Society. All rights reserved.