Bimetallic Alloy Air Cathode Promoting Superoxide Formation for High-Performance Na-Air Batteries

Sodium superoxide is considered the preferred discharge product for sodium-air batteries (SABs) due to the reversible electrochemistry of the O₂/O₂ ^- redox pair and the consequent low charge overpotential. However, air cathodes of SABs based on mono-metal systems have not yet achieved optimal adsorption of the discharge products, leading to suboptimal performance of SABs. In this study, we present FeCo bimetallic alloy particles anchored on carbon nanotubes (FeCo/C) as a demonstration of a bimetal-based air cathode for SABs. Na-air batteries with FeCo/C cathode can achieve a low overpotential gap of 500 mV, a high discharge capacity of 3392.20 mAh g^-1, and excellent cyclic stability over 200 cycles (800 h). Ex-situ spectroscopy confirms the successful formation of sodium superoxide as the main discharge product, establishing a clear correlation between excellent performance and discharge product composition and verifying the effectiveness of the bimetallic alloy cathode. Theoretical calculations further reveal that the bimetallic-based air cathode exhibits improved adsorption of sodium superoxide, significantly enhancing the performance of SABs. This work pioneers the use of bimetal alloy strategies to optimize discharge products in SABs, paving the way for their practical application.