Understanding Moisture and Carbon Dioxide Involved Interfacial Reactions on Electrochemical Performance of Lithium–Air Batteries Catalyzed by Gold/Manganese-Dioxide

Lithium–air (Li–air) battery works essentially based on the interfacial reaction of 2Li + O₂ ↔ Li₂O₂ on the catalyst/oxygen-gas/electrolyte triphase interface. Operation of Li–air batteries in ambient air still remains a great challenge despite the recent development, because some side reactions related to moisture (H₂O) and carbon dioxide (CO₂) will occur on the interface with the formation of some inert byproducts on the surface of the catalyst. In this work, we investigated the effect of H₂O and CO₂ on the electrochemical performance of Li–air batteries to evaluate the practical operation of the batteries in ambient air. The use of a highly efficient gold/δ-manganese-dioxide (Au/δ-MnO₂) catalyst helps to understand the intrinsic mechanism of the effect. We found that H₂O has a more detrimental influence than CO₂ on the battery performance when operated in ambient air. The battery operated in simulated dry air can sustain a stable cycling up to 200 cycles at 400 mA g^–1 with a relatively low polarization, which is comparable with that operated in pure O₂. This work provides a possible method to operate Li–air batteries in ambient air by using optimized catalytic electrodes with a protective layer, for example a hydrophobic membrane