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 NH₄ ⁺ and simultaneously leveraging atmospheric oxygen as a reservoir for NH₄ ⁺ storage. Notably, NH₄ ⁺ 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 NH₄ ⁺ can act as a proton donor, replacing H₂O in neutral media and reducing energy barriers in the protonation of ^*O₂ ^- 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 NH₄ ⁺ storage and opens up new avenues for the design and advancement of innovative, sustainable, and environment-friendly AIBs.