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Oxide ions in transition metal oxide cathodes can store charge at high voltage offering a route towards higher energy density batteries. However, upon charging these cathodes, the oxidized oxide ions condense to form molecular O₂ trapped in the material. Consequently, the discharge voltage is much lower than charge, leading to undesirable voltage hysteresis. Here we capture the nature of the electron holes on O²⁻ before O₂ formation by exploiting the suppressed transition metal rearrangement in ribbon-ordered Na_0.6[Li_0.2Mn_0.8]O₂. We show that the electron holes formed are delocalized across the oxide ions coordinated to two Mn (O–Mn₂) arranged in ribbons in the transition metal layers. Furthermore, we track these delocalized hole states as they gradually localize in the structure in the form of trapped molecular O₂ over a period of days. Establishing the nature of hole states on oxide ions is important if …