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.