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

ABSTRACT Aqueous ammonium ion batteries (AAIBs) are an emerging sustainable energy technology owing to their high ionic conductivity, safety, low cost, and non‐metallic charge carrier. However, their practical applicability is restricted by low energy density, a narrower potential window, and poor cycling stability. An entropy‐engineered amino group‐functionalized metal–organic framework (EnMOF‐NH 2 ) is reported as a promising cathode for high‐performance AAIBs. EnMOF‐NH 2 consists of five metal nodes (Co, Ni, Fe, Mn, Mo) and an amino‐functionalized benzene dicarboxylic acid linker (BDC‐NH 2 ), which provides multiple redox centers, enhanced structural stability, and abundant hydrogen bonding sites for efficient NH 4 + storage. The incorporation of Mo metal nodes into the multi‐metallic MOF can strengthen the metal‐ligand interaction and suppress the metal dissolution, while amino‐functionalized BDC provides polarity to the framework and enables fast NH 4 + storage through hydrogen bonding. EnMOF‐NH 2 achieves a high reversible capacity of 130.8 mAh g − 1 at 0.3 A g − 1 in 1.0 M (NH 4 ) 2 SO 4 , outperforming the non‐amino‐functionalized EnMOF‐BDC. It exhibits excellent rate capability, and capacity activation to 162% after 2500 cycles. A full cell coupled with an EnMOF‐NH 2 cathode and perylene tetracarboxylic dianhydride (PTCDA) anode retains 83% capacity over 1000 cycles. Such entropy‐engineered, amino‐group‐functionalized MOF materials represent a promising cathode for future aqueous ammonium‐ion batteries.