Fast‐Charging MXene/TiN‐Confined In2Se3 Anode with Dual Hydrogen‐Bonding Synergy for High‐Capacity Ammonium‐Ion Storage

Aqueous ammonium‐ion (NH4+) based hybrid pseudocapacitors (NH‐HPCs) integrate sustainability and cost‐effectiveness, yet their cycling stability is critically challenged by sluggish NH4+ transport, particularly in MXene‐based anodes. Herein, NH3‐induced N‐functionalization fabricates a MXene/TiN conductive substrate, enabling confined rotary hydrothermal growth of indium selenide (In2Se3) nanoparticles into an In2Se3@MXene/TiN heterostructure. Directional Ti─N bonds suppress MXene stacking and In2Se3 agglomeration while synergizing charge‐redistribution‐induced lattice strain with hierarchical 2–5 nm pore channels, enabling ultrafast NH4+ migration. Density functional theory (DFT) calculations confirm electron‐deficient Ti sites and dual Se···H─N/Ti─N···H hydrogen bonds enhance NH4+ adsorption, where intensified charge polarization and optimized orbital hybridization boost ion storage kinetics and structural stability. The heterostructure anode delivers 1776.1 F g−1 at 1 A g−1 with 98.84% capacitance retention over 6000 cycles. In full‐cell configuration (In2Se3@MXene/TiN//AC), the NH‐HPC achieves 85.45 Wh kg−1 at 800 W kg−1—powering a commercial mini‐fan for >4 min after 30 s charging. A modular pouch‐cell version reaches 98.2 Wh kg−1 (800 W kg−1), demonstrating exceptional stability during bending/flame tests while operating light emitting diodes array (LEDs). This work highlights interfacial charge synergy in confined heterostructures for unprecedented NH4+ storage capacity and stability, advancing high‐performance ammonium‐ion energy storage.