Li-ion and related battery technologies will be important for years to come. However, society needs energy storage that exceeds that 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 alternative is the Li-air (O₂) battery, Fig. 1; 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 oxygen redox processes at the positive electrode within the battery.^[6-15] As a result of these fundamental studies it is generally accepted that a solution growth mechanism for Li₂O₂ will be required to achieve high rates and capacities, avoiding the formation of passivating Li₂O₂ films on the electrode surface.  Recent results exploring the electrochemical mechanism of O₂ reduction to form Li₂O₂ at the positive electrode have identified new strategies to achieve this by exploiting the effect of the electrolyte solution. Moving to a solution phase discharge mechanism highlights the requirement for charge mediation between the electroactive species and the electrode, thus using solid Li₂O₂ simply as a storage material for lithium ions and electrons. The implications of this will be discussed

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