Recently interest in the Na-O2 battery has grown due to the relatively low polarization during cycling and the high rates.[13, 14] This is despite the lower specific energy of this battery chemistry. A number of groups have shown promising results with this system.[16-18] An important area of contention is the nature of the discharge product, which, unlike the lithium system that forms Li2O2, may form the superoxide, peroxide or oxide. The discharge product in the metal-O2 battery directly influences the specific capacity and ease of charge. Therefore, it is important to understand the mechanism such that this can be controlled.
We have combined a range of electrochemical, spectroscopic and microscopy methods to investigate the mechanism of electrochemical O2 reduction. The results of these studies will be presented, along with the implications for the future of rechargeable metal-O2 batteries.
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