Reactive O species from O-loss from TM oxide cathodes are recognized as major reason of electrolyte instability^{1, 2}. However, onset/extent of instability, bulk and surface reconstruction, and O₂ and CO₂ evolution are inconclusive. Particularly, the generation/deactivation mechanism of excited O₂ species under the prevailing conditions in these cathodes are unknown. Based on our experience with ¹O₂ in electrochemistry^3-7 we want to fill this knowledge gap.

We will discuss recent work on excited O₂ species and linked surface reactions in the context of high voltage TM cathodes. This requires newly developed methods and expands the knowledge more generally on O₂ electrochemistry at highly polarized conductors with relevance beyond battery chemistry.

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