Singlet oxygen is not the main source of electrolyte degradation in lithium-oxygen batteries

The lithium-air (oxygen) battery could offer significant improvements in gravimetric energy density compared to lithium-ion technology. A major barrier to realising this goal is the oxidative degradation of the electrolyte solution and the carbon at the positive electrode. Recently, the lithium-oxygen field has been focused on the formation of singlet oxygen within the cell, its impact as a major source of degradation, and strategies to mitigate this. Here we have investigated the reactivity of components within the lithium-oxygen cell by exposure to photochemically generated singlet oxygen. We find no significant reaction between the singlet oxygen and tetraglyme, lithium bis(trifluoromethanesulfonyl)imide, or carbon, standard electrode components, and confirm that singlet oxygen is not the major source of degradation in the lithium-oxygen battery. Our studies bring into question the need for strategies to mitigate the impact of singlet oxygen in the cell and highlight the need to refocus on the discovery of electrolyte solutions with stability against lithium peroxide. The lithium-oxygen field has focused on singlet oxygen's role in cell degradation. This study shows no significant reaction between singlet oxygen and the electrolyte or carbon cathode, confirming it is not the major degradation source.