Diagnosing Electrolyte Degradation in Lithium-Oxygen Batteries

The lithium–air (oxygen) battery could offer significant improvements in gravimetric energy density compared to lithium-ion technology.1 A major barrier to a practical device is the oxidative degradation of the electrolyte solution and the carbon at the positive electrode.2 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. We have investigated the reactivity of components within the lithium–oxygen cell by exposure to photochemically generated singlet oxygen both with and without an oxidising potential.3 This approach to screening electrolytes against singlet oxygen is described, where tetraglyme, lithium bis(trifluoromethanesulfonyl)imide, or carbon, standard lithium-oxygen cell components, are reviewed. The role singlet oxygen plays in degradation of the lithium–oxygen battery is discussed, as well as the perspective to refocus on the discovery of electrolyte solutions with stability against major antagonists. [1] Aurbach, D., McCloskey, B., Nazar, L. et al. Advances in understanding mechanisms underpinning lithium–air batteries., Nat. Energy., 1: 16128 (2016); [2] Jethwa, R. B., Mondal, S., Pant, B., Freunberger, S. A., To DISP or not? The Far-Reaching Reaction Mechanisms Underpinning Lithium-air batteries., Angew. Chem. Int. Ed., e202316476 (2023); [3] Zor, C, Jones, K. D., Rees, G. J., Yang, S., Pateman, A., Gao, X., Johnson, L. R., Bruce, P. G., Singlet oxygen is not the main source of electrolyte degradation in lithium oxygen batteries., Energy Environ. Sci.,17: 7355-7361 (2024) Figure 1