Lithium Superoxide Hydrolysis and Relevance to Li-O₂ Batteries

Fundamental understanding of reactions of lithium peroxides and superoxides is essential for the development of Li-O₂ batteries. In this context, an investigation is reported of the hydrolysis of lithium superoxide, which has recently been synthesized in a Li-O₂ battery. Surprisingly, the hydrolysis of solid LiO₂ is significantly different from that of NaO₂ and KO₂. Unlike KO₂ and NaO₂, the hydrolysis of LiO₂ does not produce H₂O₂. Similarly, the reactivity of Li₂O₂ toward water differs from LiO₂, in that Li₂O₂ results in H₂O₂ as a product. The difference in the LiO₂ reactivity with water is due to the more exothermic nature of the formation of LiOH and O₂ compared with the corresponding reactions of NaO₂ and KO₂. We also show that a titration method used in this study, based on reaction of the discharge product with a Ti(IV)OSO₄ solution, provides a useful diagnostic technique to provide information on the composition of a discharge product in a Li-O₂ battery.