An Ultrastable Aqueous Ammonium‐Ion Battery Using a Covalent Organic Framework Anode

Abstract Aqueous ammonium ion batteries have garnered significant research interest due to their safety and sustainability advantages. However, the development of reliable ammonium‐based full batteries with consistent electrochemical performance, particularly in terms of cycling stability, remains challenging. A primary issue stems from the lack of suitable anode materials, as the relatively large NH 4 + ions can cause structural damage and material dissolution during battery operation. To address this challenge, an Aza‐based covalent organic framework (COF) material is introduced as an anode for aqueous ammonium ion batteries. This material exhibits superior ammonium storage capabilities compared to existing anode materials. It operates effectively within a negative potential range of 0.3 to‒1.0 V versus SCE, achieves high capacity even at elevated current densities (≈74 mAh g −1 at 10 A g −1 ), and demonstrates exceptional stability, retaining a capacity over 20 000 cycles at 1.0 A g −1 . Furthermore, by pairing this COF anode with a Prussian blue cathode, an ammonium rocking‐chair full battery is developedd that maintains 89% capacity over 20 000 cycles at 1.0 A g −1 , surpassing all previously reported ammonium ion full batteries. This study offers insights for the design of future anodes for ammonium ion batteries and holds promise for high‐energy storage solutions.