Two-dimensional TiCl₂: a high-performance anode material for Na-ion batteries with high capacity and fast diffusion

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Sodium-ion batteries (NIBs) are crucial for large-scale energy storage due to safety, resource abundance, and cost.
• Developing effective anode materials remains a key challenge for NIB advancement.

Purpose of the Study:

• To systematically investigate the potential of two-dimensional (2D) TiCl2 as an electrode material for NIBs using first-principles calculations.
• To evaluate the stability, storage capacity, ion diffusion, and structural changes of TiCl2 in NIBs.

Main Methods:

• First-principles calculations were employed to study monolayer and bilayer TiCl2.
• Exfoliation energy, cohesive energy, phonon modes, and thermal stability were assessed to determine material stability.
• Na adsorption strength, diffusion energy barriers, open-circuit voltage, and lattice changes were calculated to evaluate electrochemical performance.

Main Results:

• Monolayer TiCl2 is easily exfoliated with low energy (0.64 J m⁻²) and exhibits high stability.
• It demonstrates a high storage capacity (451.3 mA h g⁻¹), low diffusion barrier (0.02–0.14 eV), moderate voltage (0.81 V), and minimal lattice change (2.37%).
• Bilayer TiCl2 enhances Na adsorption but slightly hinders Na-ion diffusion.

Conclusions:

• TiCl2 is a promising anode material for NIBs due to its favorable electrochemical properties and stability.
• Further research into TiCl2-based anodes could advance NIB technology for energy storage.