Implications of CO₂ Contamination in Rechargeable\nNonaqueous Li–O₂ Batteries

Abstract

In this Letter, the effect of CO₂ contamination\non nonaqueous\nLi–O₂ battery rechargeability is explored. Although\nCO₂ contamination was found to increase the cell’s\ndischarge capacity, it also spontaneously reacts with Li₂O₂ (the primary discharge product of a nonaqueous Li–O₂ battery) to form Li₂CO₃. CO₂ evolution from Li₂CO₃ during battery charging\nwas found to occur only at very high potentials (>4 V) compared\nto\nO₂ evolution from Li₂O₂ (∼3–3.5\nV), and as a result, the presence of CO₂ during discharge\ndramatically reduced the voltaic efficiency of the discharge–charge\ncycle. These results emphasize the importance of not only completely\nremoving CO₂ from air fed to a Li-air battery, but also\ndeveloping stable cathodes and electrolytes that will not decompose\nduring battery operation to form carbonate deposits.