Advances in Understanding Oxygen Reduction in the Metal-O2 Battery
Authors: Jovanov Zarko P , Chen Yuhui , Johnson Lee , Bruce Peter G. 
Published: February 2020

Li-ion and related battery technologies will be important for years to come. However, we must explore alternatives if we are to have any hope of meeting the long-term needs for energy storage. One such alternative is the metal-O2 battery; the theoretical specific energy of typical aprotic metal-O2batteries exceeds that of Li-ion, but many obstacles hinder realization of this technology.[1-4] Overcoming these hurdles will require an understanding of the fundamental electrochemistry at the positive electrode within aprotic metal-air batteries.[5-12]
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.[15] 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.

References:

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Figure 1