Interfacial Dirac-Modulated TiN/MXene Heterostructure Enables Decoupled Ion-Electron Transport for Ultrafast...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Aqueous ammonium-ion hybrid pseudocapacitors (AAI-HPCs) require anodes with excellent conductivity, rapid ion kinetics, and durability.
• Conventional 2D materials face challenges like restacking, hindering performance.
• Atomic-precision heterostructure design is crucial for overcoming these limitations.

Purpose of the Study:

• To develop novel anode materials for AAI-HPCs with improved performance.
• To investigate the role of nitrogen engineering and interfacial confinement in heterostructure design.
• To enhance ion diffusion and electrochemical stability in AAI-HPCs.

Main Methods:

• In situ nitrogen engineering of TiN/MXene cascades via hexamine-derived NH₃ nitridation.
• Integration of ultrathin Ag-Bi₂Te₃ nanoplates using polyvinylpyrrolidone (PVP)-directed interfacial confinement.
• Ex-situ and operando analysis to confirm electrochemical mechanisms and structural integrity.
• Fabrication and testing of full-cell AAI-HPCs using the developed heterostructure anodes.

Main Results:

• Successfully synthesized Ag-Bi₂Te₃@TiN/MXene heterostructures with prevented MXene restacking and expanded ion diffusion highways.
• Achieved a 33.3% reduction in NH₄ ⁺ diffusion barriers through dual hydrogen-bonded coordination sites.
• Demonstrated exceptional cycling stability with 98.1% capacity retention over 5,000 cycles.
• Full cells delivered a record energy density of 79.2 Wh kg^-1, powering commercial electronics.

Conclusions:

• The developed Ag-Bi₂Te₃@TiN/MXene heterostructure is a promising anode material for high-performance AAI-HPCs.
• Interfacial electron modulation is a viable strategy for decoupling ion and electron transport in pseudocapacitors.
• This work paves the way for next-generation aqueous ion energy storage systems with enhanced performance and stability.