Fundamental Understanding of Water-Induced Mechanisms in Li-O₂ Batteries: Recent Developments and Perspectives

Modern sustainability challenges in recent years have warranted the development of new energy storage technologies. Practical realization of the lithium-O₂ battery holds great promise for revolutionizing energy storage as it holds the highest theoretical specific energy of any rechargeable battery yet discovered. However, the complete realization of Li-O₂ batteries necessitates ambient air operations, which presents quite a few challenges, as carbon dioxide (CO₂ ) and water (H₂ O) contaminants introduce unwanted byproducts from side reactions that greatly affect battery performance. Although current research has thoroughly explored the beneficial incorporation of CO₂ , much mystery remains over the inconsistent effects of H₂ O. The presence of water in both the cathode and electrolyte has been observed to alter reaction mechanisms differently, resulting in a diverse range of effects on voltage, capacity, and cyclability. Moreover, recent preliminary research with catalysts and redox mediators has attempted to utilize the presence of water to the battery's benefit. Here, the key mechanism discrepancies of water-afflicted Li-O₂ batteries are presented, concluding with a perspective on future research directions for nonaqueous Li-O₂ batteries.