Synergistic Dynamic Hydrogen‐Bond Engineering in COF Cathode and Hydrogel Electrolyte for Durable NH ₄ ⁺ Storage

Abstract

ABSTRACT Aqueous ammonium‐ion batteries (AAIBs) have garnered considerable attention for sustainable energy storage, leveraging the rapid diffusion kinetics of NH 4 + ions enabled by Grotthuss‐type proton transport through reversible hydrogen‐bonding interactions. Nevertheless, their practical deployment is often constrained by irreversible side reactions and structural degradation from conventional liquid electrolytes and inorganic cathodes. Herein, we report a dual‐zone design strategy of integrating a tailored hydrogel electrolyte with a redox‐active covalent organic framework (COF) cathode to promote durable NH 4 + storage in AAIBs. In the electrolyte, a pH‐modulated polyacrylamide‐based hydrogel electrolyte with a uniform 3D network suppresses anion‐induced salting‐out effects and facilitates dynamic hydrogen‐bond‐enabled NH 4 + migration. Complementarily, a hexaazatrinaphthalene (HATN)‐based COF (HATN‐COF) cathode with abundant C═O/C═N groups provides multiple reversible hydrogen‐bonding sites for stable NH 4 + storage. As expected, the assembled cell achieves a high initial capacity of 420 mAh g −1 at 0.05 A g −1 and retains a high reversible capacity of 126 mAh g −1 at 2 A g −1 with 70.8% capacity retention after 1300 cycles. This work demonstrates that the dual‐zone design strategy holds great potential for advancing high‐performance AAIBs.