Amide- and Urea-Based Solvents for Li–O2Batteries. Part I: Experimental Evaluation

Nonaqueous Li–O₂ batteries have the potential to aid in the electrification of our society due to their relatively high theoretical energy density. Unfortunately, the technology suffers from large degrees of irreversibility due to the aggressive chemical environment associated with the oxidation of the discharge product lithium peroxide. Herein, we present a study of a range of linear and cyclic amides and ureas as aprotic electrolyte solvents for the Li–O₂ battery, some of which show slight increases in reversibility relative to the well-established pseudo-stable glymes, although we find that none provide reversibility necessary to enable a rechargeable system. Using quantitative differential electrochemical mass spectrometry, acid titrations, and isotopic labeling of O₂ and carbon in the positive electrode, we provide insight into the degradation pathways for these solvents. In the companion article, we compare our experimental results presented here to solvent decomposition pathways including a Baeyer–Villiger oxidation mechanism.