Influence of the Mechanism of Discharge Product Formation on the Electrochemical Performance and Cyclability of Aprotic Na-O₂ Batteries

Na-O-2 batteries have emerged as potential alternatives to state-of-the-art lithium-ion batteries due to their high specific energy density. However, challenges related to poor overall efficiency and long-term stability have hindered their practical application. Understanding the deactivation mechanisms at the electrode/electrolyte interfaces is critical to overcoming these challenges. Herein, we investigate the effect of the cathode/electrolyte interface on the discharge mechanism by varying the glyme-ether electrolyte solvent and the nature of the carbon cathode. We report that discharge-charge energetics at carbon/electrolyte interfaces driven by surface-mediated discharge are sensitive to the nature of the carbon cathode. Their main deactivation mechanism involves the formation of undesired discharged products, which can be mitigated by tuning the cathode surface. Conversely, discharge-charge energetics and deactivation of Na-O-2 cells driven by a solution-mediated discharge process have limited dependence on the carbon cathode. These findings have implications for effectively designing efficient and stable Na-O-2 batteries.