(229e) Mechanistic Studies of Nonaqueous Li-O2 Electrochemistry

This presentation will highlight mechanistic studies of electrochemistry occurring at the cathode of a Li-O₂ battery.  Quantitative Differential Electrochemical Mass Spectrometry (DEMS) and electrochemical measurements on flat, nonporous glassy carbon electrodes were coupled with ex-situ chemical analysis of electrodes to better understand the active chemistry within the cell.  Our results indicate that solid Li₂O₂ formation and oxidation are the only active reversible electrochemical reactions occurring at the cathode and that both of these processes occur at low kinetic overpotentials, particularly compared to aqueous oxygen reduction and evolution.  Furthermore, no solution-soluble intermediates, such as O₂^-, exist in a reasonably stable solvent (such as dimethoxyethane).  Given the low overpotentials observed in the cell and the limited diffusion rates that are implied from no intermediate solubility, heterogeneous catalysis (beyond the catalytic effect observed from carbon) for oxygen reduction and evolution in the Li-O₂ cell may be unnecessary.