Li-ion and related battery technologies will be important for years to come. However, society needs energy storage that exceeds the capacity of Li-ion batteries. We must explore alternatives to Li-ion if we are to have any hope of meeting the long-term needs for energy storage. One such alternative is the Li-air (O₂) battery; its theoretical specific energy exceeds that of Li-ion, but many hurdles face its realization.^[1-5] One spin-off of the recent interest in rechargeable Li-O₂ batteries, based on aprotic electrolytes is that it has highlighted the importance of understanding the fundamental electrochemistry at the positive electrode within the battery.^[6-15]

The challenges of obtaining efficient, reversible charge and discharge are well-documented in the field.  Here, we describe how our recent studies into the electrochemical mechanism of O₂ reduction to form Li₂O₂ at the positive electrode might allow us to design new strategies to overcome these limitations;^[16]For example, exploiting the effect of solvent donor number, Fig. 1. We will describe our resent results using redox mediators to facilitate the electrochemistry along with the implications of the results for the future of rechargeable Li-O₂ batteries.

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