Comparative Study on Li Depletion for Li-O2 Batteries Using Carbonate and Ether Solvents

Recently, many researchers have interest on the Li-O₂ rechargeable battery as a promising energy storage system because of its extremely large theoretical energy density. Due to its highly negative redox potential and an extremely large specific capacity, Li metal is essential for this system. However, Li metal has some drawbacks as an anode material for rechargeable batteries such as dendrite formation in charging process, surface passivation layer formation resulting in a loss of Li amount. Li loss by dendrites and SEI layers attribute depletion of energy sources, and therefore, significantly deteriorate cycleability of cells. In spite of its high importance, in previous studies, researches about Li metal are not studied in details especially in Li-O₂ batteries. In this study, we investigate the Li depletion and its influence on cyclestability of cells depending on solvents including EC/DEC and TEGDME which is representative solvents in Li‒O₂ batteries. Although ether based solvent is considered for good candidates as it has a fairly low vapor pressure with higher stability against oxidation, we confirmed serious dendrites with newly developed SEI layer of ROLi by XPS and ATR-FTIR analysis. This indicates increased Li depletion for TEGDME based cells and consequently influence on cycle stability.