Comparison of Lithium Salt Effect on Negative Electrodes and Lithium–Air Cell Performance

The cycle stability of lithium negative electrodes for Li–air secondary batteries was studied under oxygen atmosphere using Li∣Li symmetric cells with three organic electrolyte solutions: 1.0 M LiCF3SO3/tetraglyme (G4), 1.0 M LiN(SO2CF3)2/G4, and 1.0 M LiNO3/G4. Of these, 1.0 M LiNO3/G4 showed excellent stability without dendrite deposition, even for increased dissolution/deposition capacity from 0.50 to 2.0 mAh cm−2. These results are considered to be due to the stable Li2O passivation layer that was formed, not only by the direct reaction with oxygen, but also by the action of NO3 − as an oxidant, which released NO2 − as a redox mediator. Li–O2 cells with 1.0 M LiNO3/G4 showed a clear charging voltage plateau at 3.7 V, which evidenced the redox mediator effect of NO2 −, and cell cycleability was enhanced to 25 cycles.