Interfacial Dirac‐Modulated TiN/MXene Heterostructure Enables Decoupled Ion‐Electron Transport for Ultrafast Ammonium‐Ion Storage
Inaam Ullah, Ayesha Irfan, Mai Li, Chenxi Li, Haotian Hu, Dajun Wu, Qinglin Deng, Yifeng Cheng, Chunrui Wang, Limin Wu, Renchao Che
Abstract
Abstract Aqueous ammonium‐ion hybrid pseudocapacitors (AAI‐HPCs) demand anodes that unify metallic conductivity, ultrafast NH 4 + kinetics, and robust cycling, a feat unattainable with conventional 2D materials due to irreversible restacking, necessitating atomic‐precision heterostructure design. Herein, in situ nitrogen‐engineered TiN/MXene cascades are developed through hexamine‐derived NH 3 nitridation, inducing spontaneous N‐vacancy formation and epitaxial TiN nucleation, simultaneously preventing MXene restacking while creating expanded ion diffusion highways. Polyvinylpyrrolidone (PVP)‐directed interfacial confinement precisely integrates ultrathin Ag‐Bi 2 Te 3 nanoplates into the TiN/MXene matrix, where topological Dirac states ensure metallic conductivity while enhancing mechanical robustness. The resulting Ag‐Bi 2 Te 3 @TiN/MXene heterostructure establishes dual hydrogen‐bonded NH 4 + coordination sites, combining stable Ti─N─H─N anchoring with Ag‐enhanced Te─H─N interactions, collectively reducing diffusion barriers by 33.3% (from 36 to 24 eV). Ex‐situ/operando analysis confirms reversible Bi 3+ /Bi 0 and Ag + /Ag 0 redox couples operating in concert with strain‐adaptive MXene frameworks, achieving exceptional 98.1% capacity retention over 5,000 cycles. Full‐cell Ag‐Bi 2 Te 3 @TiN/MXene//AC (AAI‐HPCs) deliver record energy density 79.2 Wh kg −1 (at 800 W kg −1 ) capable of powering commercial electronics for >100 s, with flexible pouch cells reaching 96.5 Wh kg −1 under mechanical stress—surpassing reported MXene‐based NH 4 + systems. This work establishes interfacial electron modulation as a universal design paradigm for decoupled ion‐electron transport in next‐generation AAI‐HPCs.