Enhancing sodium ionic conductivity in tetragonal-Na₃PS₄ by halogen doping: a first principles investigation

Area of Science:

• Materials Science
• Solid-State Chemistry
• Computational Materials Science

Background:

• Tetragonal sodium thiophosphate (t-Na3PS4) is a promising solid-state electrolyte for sodium-ion batteries.
• High Na ionic conductivity is crucial for efficient solid-state electrolytes.

Purpose of the Study:

• To investigate the effect of halogen doping on the Na ionic conductivity of t-Na3PS4.
• To identify the optimal halogen dopant for enhancing ionic conductivity.

Main Methods:

• First-principles calculations were employed to systematically study pristine and halogen-doped t-Na3PS4.
• Calculations focused on Na ionic conductivity, activation energy, and defect binding energies.

Main Results:

• Pristine t-Na3PS4 exhibits low Na ionic conductivity (0.01 mS cm-1).
• Halogen doping, particularly with chlorine (1.56% Cl), significantly increases conductivity (1.07 mS cm-1).
• Bromine-doped t-Na3PS4 demonstrates the highest Na ionic conductivity (2.37 mS cm-1 at 300 K) and lowest activation energy due to reduced defect binding energy.

Conclusions:

• Halogen doping, especially with bromine, is an effective strategy to enhance Na ionic conductivity in t-Na3PS4.
• Br-doped t-Na3PS4 shows excellent potential as a solid-state superionic conductor for sodium-ion applications.