Binary Mixtures of Highly Concentrated Tetraglyme and Hydrofluoroether as a Stable and Nonflammable Electrolyte for Li-O2 Batteries.

Developing a long-term stable electrolyte is one of the most enormous challenges for Li-O2 batteries. Equally, the high flammability of frequently used solvents seriously weakens the electrolyte safety in Li-O2 batteries, which inevitably restricts their commercial applications. Here, a binary mixture of highly concentrated tetraglyme electrolyte (HCG4) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) was used for a novel electrolyte (HCG4/TTE) in Li-O2 batteries, which exhibit good wettability, enhanced ionic conductivity, considerable nonflammability, and high electrochemical stability. Being a co-solvent, TTE can contribute to increasing ionic conductivity and to improving flame retardance of the as-prepared electrolyte. The cell with this novel electrolyte displays an enhanced cycling stability, resulting from the high electrochemical stability during cycling and the formation of electrochemically stable interfaces prevents parasitic reactions occurring on the Li anode. These results presented here demonstrate a novel electrolyte with a high electrochemical stability and considerable safety for Li-O2 batteries.