Investigation of Li-O₂ Battery Performance Integrated with RuO₂ Inverse Opal Cathodes in DMSO

The development of electrocatalysts has emerged as an important aspect of rechargeable lithium-oxygen (Li-O₂) batteries due to the fact that they facilitate the formation and decomposition of discharge products, leading to a higher capacity and cyclability. Herein, we demonstrate that ruthenium oxide (RuO₂) inverse opal (IO), which possesses a three-dimensionally ordered porous network, has been developed and applied to the Li-O₂ battery as a cathode. The RuO₂ IO cathode contributes to the reduction of charge overpotential by up to ∼120 mV in lithium nitrate/dimethyl sulfoxide (LiNO₃/DMSO), which corresponds to an ∼670 mV decrease as compared with that of a carbon cathode, Ketjen black (KB). Differential electrochemical mass spectrometer (DEMS) monitoring and magic angle spinning nuclear magnetic resonance (MAS NMR) measurement reveal the origin of the extremely low charge overpotential obtained from the RuO₂ IO cathode by confirming the formation of lithium hydroxide (LiOH) as the main discharge product. The incorporation of RuO₂ also remarkably reduces the formation of byproducts such as lithium carbonate (Li₂CO₃) by substantially lowering the charge overpotential. A mechanistic explanation of the device operation is provided in this study as well.