Stabilizing effect of ion complex formation in lithium-oxygen battery electrolytes

Glyme-based electrolytes with various lithium bis(trifluoromethane) sulfonamide (LiTFSI) salt concentrations have been investigated for their use in Li‑oxygen battery applications. Charge/discharge cycling with a cycle capacity of 500 mAh·g−1 showed an improvement as high as 300% for electrolytes containing higher LiTFSI concentrations. Electrochemical impedance spectroscopy (EIS) studies of Li-O2 full cells and Raman spectroscopy studies on the discharged cathodes revealed that the superior cyclability at higher LiTFSI contents was due to a decrease in the rate of growth of glyme degradation products (lithium carbonate species). Raman spectroscopy analyses of the electrolytes also suggested that the increase in LiTFSI concentration afforded the formation of cationic and anionic complexes that helped mitigate the tetraglyme degradation.