A High‐Rate and Ultrastable Ammonium Ion‐Air Battery Enabled by the Synergy of ORR and NH4+ Storage

Abstract Ammonium ion batteries (AIBs) offer cost‐effectiveness, nontoxicity, and eco‐friendly attributes in energy storage technology. However, the constrained capacity and poor stability of conventional cathode materials have impeded their widespread adoption. Herein, a synergistic approach is introduced to overcome these challenges, by enhancing the air cathode with NH 4 + and simultaneously leveraging atmospheric oxygen as a reservoir for NH 4 + storage. Notably, NH 4 + significantly enhances the oxygen reduction reaction (ORR) performance in neutral environments. Through in situ Raman spectroscopy and quantum density functional theory calculations, it is elucidated how NH 4 + can act as a proton donor, replacing H 2 O in neutral media and reducing energy barriers in the protonation of * O 2 − and * O, thereby accelerating ORR kinetics. The resulting ammonium ion‐air battery, comprising an air cathode and a polymer (PNP) anode, showcases impressive metrics: high energy density of 78 Wh kg −1 and power density of 9369 W kg −1 at 1 A g −1 , an initial capacity of 94.3 mAh g −1 and exceptional cycling stability (70.4% capacity retention after 12 500 cycles) at 10 A g −1 . This pioneering research highlights the synergistic relationship between ORR and NH 4 + storage and opens up new avenues for the design and advancement of innovative, sustainable, and environment‐friendly AIBs.