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

Abstract 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.