Lithium Superoxide Hydrolysis and Relevance to Li-O-2 Batteries

Abstract

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.