Exploring the electrochemical reaction mechanism of carbonate oxidation in Li–air/CO2 battery through tracing missing oxygen

Abstract

As energy storage systems with great prospects, both Li–air and Li–CO₂ batteries possess low energy efficiency and poor cycle performance, which is caused by the accumulation of Li₂CO₃ during cycling. Therefore, the complete electrochemical decomposition of Li₂CO₃ during charging will greatly improve the performance of Li–air and Li–CO₂ batteries. However, our understanding of the electrochemical decomposition mechanism of Li₂CO₃ is very limited. In this work, we report that CO₂ is released during the electrochemical decomposition of Li₂CO₃ while O₂ is not detected throughout the whole process. Mass spectra and FTIR results show that the electrolyte solvent undergoes degradation during charging. We further demonstrate that this degradation is caused by superoxide radicals, which are generated from Li₂CO₃.