Electrolyte instability is one of the most challenging impediments to enabling Lithium-Oxygen (Li-O2) batteries for practical use. The use of physical organic chemistry principles to rationally design new molecular components may enable the discovery of electrolytes with stability profiles that cannot be achieved with existing formulations. Here, we report on the development of sulfamide- and sulfonamide-based small molecules that are liquids at room temperature, capable of dissolving reasonably high concentration of Li salts (e.g., LiTFSI), and are exceptionally stable under the harsh chemical and electrochemical conditions of aprotic Li-O2 batteries. In particular, N,N-dimethyl-trifluoromethanesulfonamide was found to be highly resistant to chemical degradation by peroxide and superoxide, stable against electrochemical oxidation up to 4.5 VLi, and stable for > 90 cycles in a Li-O2 cell when cycled at < 4.2 VLi. This study provides guiding principles for the development of next-generation electrolyte components based on sulfamides and sulfonamides.
Keywords: (electro)chemical stability; Electrochemistry; Li-O2 batteries; electrolyte design; peroxide; singlet oxygen; sulfamide; sulfonamide; superoxide.