Surface Charge Engineering for Covalently Assembling Three-Dimensional MXene Network for All-Climate Sodium Ion...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• MXenes are promising anode materials for sodium ion batteries (SIBs).
• Surface functional groups on MXenes cause sluggish ion diffusion, limiting SIB performance.
• Developing strategies to improve ion kinetics in MXene-based anodes is crucial.

Purpose of the Study:

• To engineer a 3D conductive polyaniline (PANI)/Ti3C2Tx MXene network for enhanced SIB anode performance.
• To investigate the role of PANI in improving ion diffusion kinetics and surface charge properties of Ti3C2Tx.
• To evaluate the electrochemical performance and stability of the PANI/Ti3C2Tx composite across a wide temperature range.

Main Methods:

• Self-assembly of Ti3C2Tx MXenes with positively charged PANI to form a 3D network.
• Characterization of the network structure, including interlayer spacing and surface charge.
• Electrochemical testing to assess sodium storage capacity, rate performance, and cycling stability.
• X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) to confirm covalent Ti-N bonding.

Main Results:

• The 3D PANI/Ti3C2Tx network demonstrates significantly improved ion diffusion kinetics.
• PANI intercalation enlarges interlayer spacing and transitions Ti3C2Tx surface charge from negative to positive.
• A stable Ti-N covalent interaction was confirmed between PANI and Ti3C2Tx.
• The PANI/Ti3C2Tx composite exhibits high specific capacity, superior rate capability, and an ultralong lifespan.
• Good electrochemical performance was maintained at temperatures ranging from -30 to +50 °C.

Conclusions:

• The PANI/Ti3C2Tx composite offers a viable strategy for high-performance SIB anodes.
• The 3D network structure effectively overcomes the kinetic limitations of pristine MXenes.
• This approach enables high-rate sodium storage and all-climate energy storage device applications.