Atomic-Scale Dynamics and Storage Performance of Na/K on FeF₃ Nanosheet

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Sodium-ion (Na-ion) and potassium-ion (K-ion) batteries are crucial for next-generation energy storage.
• Developing efficient cathode materials with long cycle life and high rate performance is essential.
• Iron fluoride (FeF₃)-based materials are candidates, but their performance needs optimization.

Purpose of the Study:

• To design and investigate a two-dimensional (2D) FeF₃ nanosheet as a cathode material for Na-ion and K-ion batteries.
• To understand the Na and K ion storage mechanism on the FeF₃(012) nanosheet using first-principles calculations.
• To evaluate the potential of this 2D FeF₃ material for flexible battery applications.

Main Methods:

• First-principles calculations were employed to simulate Na and K ion adsorption and diffusion on the FeF₃(012) nanosheet.
• Calculations assessed adsorption energies, preferred adatom configurations (dimer/tetramer), energy barriers, and diffusion coefficients.
• Electrochemical properties such as initial discharge voltage and voltage stability were analyzed.

Main Results:

• The FeF₃(012) nanosheet demonstrated strong Na and K adsorption energies (-3.55 eV for Na, -3.98 eV for K).
• Na and K adatoms formed dimers and tetramers, respectively, with favorable diffusion kinetics (K tetramer: 0.43 eV barrier, 4.22 × 10^-10 cm²·s^-1 diffusion).
• High initial discharge voltages (4.10 V for K, 3.74 V for Na) and stable discharge curves were observed, indicating good electrochemical performance.

Conclusions:

• The 2D FeF₃ nanosheet exhibits excellent Na and K ion mobility and electrochemical stability.
• It shows potential as a flexible cathode material, particularly for K-ion batteries.
• The designed 2D FeF₃ nanosheet is a promising candidate for high-performance Na/K-ion batteries.