Implications of CO2 Contamination in Rechargeable Nonaqueous Li–O2 Batteries

Abstract

In this Letter, the effect of CO₂ contamination on nonaqueous Li–O₂ battery rechargeability is explored. Although CO₂ contamination was found to increase the cell’s discharge 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 was found to occur only at very high potentials (>4 V) compared to O₂ evolution from Li₂O₂ (∼3–3.5 V), and as a result, the presence of CO₂ during discharge dramatically reduced the voltaic efficiency of the discharge–charge cycle. These results emphasize the importance of not only completely removing CO₂ from air fed to a Li-air battery, but also developing stable cathodes and electrolytes that will not decompose during battery operation to form carbonate deposits.