Long-Cycle-Life Na-Ion Anodes Based on Amorphous Titania Nanotubes--Interfaces and Diffusion

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Titania nanotubes are promising materials for energy storage applications.
• Understanding sodium storage mechanisms in titania is crucial for developing advanced sodium-ion batteries.

Purpose of the Study:

• To fabricate amorphous self-assembled titania nanotube layers.
• To investigate their sodium insertion properties and electrochemical behavior.
• To determine the mechanism of sodium storage and chemical diffusion coefficients.

Main Methods:

• Fabrication of titania nanotube layers via anodization.
• Electrochemical characterization using galvanostatic cycling and cyclic voltammetry in Na-ion test cells.
• Determination of chemical diffusion coefficients for Na(+) ions.

Main Results:

• Titania nanotube layers exhibited high cycling stability, enduring over 300 cycles with minimal capacity loss.
• Sodium storage primarily occurs in the interfacial layer between titania and the electrolyte, exhibiting pseudocapacitive behavior.
• Chemical diffusion coefficients of Na(+) were determined for the first time, ranging from 4 × 10(-20) to 1 × 10(-21) cm(2)/s.

Conclusions:

• Amorphous titania nanotubes are resilient electrode materials for sodium-ion batteries.
• The dominant sodium storage mechanism is interfacial and pseudocapacitive, differing from typical insertion reactions.
• The determined low diffusion coefficients support the proposed interfacial storage mechanism.