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Batteries based on sodium superoxide and on potassium superoxide have recently been reported^,,. However, there have been no reports of a battery based on lithium superoxide (LiO₂), despite much research^,,,, into the lithium–oxygen (Li–O₂) battery because of its potential high energy density. Several studies^,,,,,,, of Li–O₂ batteries have found evidence of LiO₂ being formed as one component of the discharge product along with lithium peroxide (Li₂O₂). In addition, theoretical calculations have indicated that some forms of LiO₂ may have a long lifetime. These studies also suggest that it might be possible to form LiO₂ alone for use in a battery. However, solid LiO₂ has been difficult to synthesize in pure form because it is thermodynamically unstable with respect to disproportionation, giving Li₂O₂ (refs , ). Here we show that crystalline LiO₂ can be stabilized in a Li–O₂ battery by using a suitable graphene-based …