Synergistic Dynamic Hydrogen-Bond Engineering in COF Cathode and Hydrogel Electrolyte for Durable NH₄ ⁺ Storage

Area of Science:

• Materials Science
• Electrochemistry
• Sustainable Energy

Background:

• Aqueous ammonium-ion batteries (AAIBs) offer sustainable energy storage due to fast ion kinetics.
• Challenges include electrolyte instability and cathode degradation, limiting practical applications.

Purpose of the Study:

• To develop a durable AAIB by integrating a specialized hydrogel electrolyte and a redox-active covalent organic framework (COF) cathode.
• To overcome limitations of conventional electrolytes and inorganic cathodes in AAIBs.

Main Methods:

• Designed a pH-modulated polyacrylamide-based hydrogel electrolyte with a 3D network to prevent salting-out and aid ion transport.
• Utilized a hexaazatrinaphthalene (HATN)-based COF cathode with hydrogen-bonding sites for stable ammonium storage.
• Assembled and tested the AAIB cell performance.

Main Results:

• The hydrogel electrolyte facilitated dynamic NH4+ migration via hydrogen bonds.
• The HATN-COF cathode demonstrated stable NH4+ storage capabilities.
• The assembled AAIB achieved a high initial capacity (420 mAh g-1) and maintained 126 mAh g-1 at 2 A g-1 after 1300 cycles (70.8% retention).

Conclusions:

• The dual-zone design strategy effectively enhances durability and performance in AAIBs.
• This approach shows significant potential for advancing high-performance and stable aqueous ammonium-ion battery technology.