Entropy-Engineered Multi-Metallic MOFs Unlock High-Performance Ammonium-Ion Storage

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous ammonium ion batteries (AAIBs) are promising sustainable energy technologies but face limitations in energy density and stability.
• Existing AAIBs struggle with low energy density, narrow potential windows, and poor cycling stability, hindering practical application.

Purpose of the Study:

• To develop a high-performance cathode material for AAIBs.
• To investigate the potential of entropy-engineered, amino group-functionalized metal-organic frameworks (EnMOF-NH2) for improved ammonium ion storage.

Main Methods:

• Synthesis of an entropy-engineered, multi-metallic metal-organic framework (MOF) incorporating amino groups (EnMOF-NH2) using five metal nodes (Co, Ni, Fe, Mn, Mo) and an amino-functionalized benzene dicarboxylic acid linker (BDC-NH2).
• Electrochemical characterization of EnMOF-NH2 as a cathode material in aqueous ammonium sulfate electrolyte.
• Fabrication and testing of a full cell using EnMOF-NH2 cathode and perylene tetracarboxylic dianhydride (PTCDA) anode.

Main Results:

• EnMOF-NH2 demonstrated a high reversible capacity of 130.8 mAh g⁻¹ at 0.3 A g⁻¹.
• The material exhibited excellent rate capability and capacity activation, reaching 162% after 2500 cycles.
• A full cell achieved 83% capacity retention over 1000 cycles, showcasing significant cycling stability.

Conclusions:

• Entropy-engineered, amino-group-functionalized MOFs are effective cathode materials for high-performance AAIBs.
• The multi-metallic composition and amino functionalization contribute to enhanced structural stability and efficient NH4+ storage.
• This work presents a promising strategy for advancing sustainable aqueous ammonium-ion battery technology.