Invited Presentation: The Effect of Solvation on Li-O2 Redox Reactions

Non-aqueous Li-O₂ batteries are estimated to deliver gravimetric energies two to three times that of conventional Li-ion batteries at comparable gravimetric power. Fundamentally understanding reaction mechanisms and associated intermediates during Li-O₂ cell operation is critical for implementing practical Li-O₂ batteries with high reversibility and long cycle life. In particular, the role of superoxide-related reaction intermediates generated during oxygen reduction on the overall electrochemical reaction is not well understood. Such knowledge is crucial for designing highly efficient Li-O₂ batteries since superoxides are thought to be potentially chemically unstable against the electrolyte solvent, reaction surface and cell components, leading to high overpotentials during charge, and short cycle life. We use the rotating disk electrode (RDE) technique coupled with theoretical calculations to probe redox potentials of superoxide formation reactions in different electrolyte solvents. These results highlight the importance of solvating ability on oxygen reactions with and without Li⁺ ions, and yield insights into potential criteria for selecting Li-O₂ cell configurations. Implications for the growth mechanisms and chemistries of Li-O₂ discharge products will also be addressed.