Clean Electrocatalysis in a Li₂O₂ Redox-Based Li-O₂ Battery Built with a Hydrate-Melt Electrolyte

The electrocatalysis of the oxygen reduction reaction and oxygen evolution reaction in nonaqueous Li-O₂ batteries suffers from severe side reactions and high charge potential. Herein, we design an unreported hydrate-melt Li-O₂ battery without use of an unstable organic solvent. Its redox reaction depends on the formation of Li₂O₂ in high yield (96%) and its full decomposition. The designed battery shows an ultralow charge potential of ∼3.16 V, a high discharge capacity of 38 mAh cm^-2, and stable cycling ability. After careful comparison of the discharge and charge products by XRD, SEM, Raman, FTIR, NMR, and quantitative titration, the great improvement in performance is attributed to the efficient avoidance of side reactions related to organic solvent degradation, which may be the primary cause of the high charge potential in a nonaqueous Li-O₂ battery. These results should initiate a deep understanding of Li-O₂ batteries and indicate another strategy toward practical Li-air batteries with moisture-proof properties and high safety.