Design of sodium superionic conductors based on multiple crystal structure prediction methods.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• All-solid-state sodium-ion batteries (ASSSIBs) offer enhanced safety and lower costs compared to conventional batteries.
• Sodium superionic conductors (SICs) are crucial solid-state electrolytes (SSEs) for efficient Na-ion transport in ASSSIBs.
• Sulfide-based SICs containing chloride ions are particularly promising due to their high ionic conductivity and stability.

Purpose of the Study:

• To explore novel sulfide sodium SICs within the Na-P-S-Cl quaternary system using advanced computational methods.
• To evaluate the potential of newly identified materials as solid-state electrolytes for ASSSIBs.

Main Methods:

• Integrated data mining structure prediction (DMSP) and crystal structure analysis by particle swarm optimization (CALYPSO) for crystal structure prediction.
• Employed first-principles calculations to assess ionic conductivity, diffusion pathways, and electrode compatibility.
• Investigated electronic conductivity to confirm suitability as SSEs.

Main Results:

• Identified two novel sodium SICs: Na6PS5Cl (NPSC1) with space group P213 and Na5PS4Cl2 (NPSC2) with space group Amm2.
• NPSC1 exhibits a high room-temperature conductivity (σRT) of 0.67 mS cm−1, significantly exceeding previously known Na6PS5Cl structures.
• Both NPSC1 and NPSC2 demonstrate three-dimensional ion diffusion, good electrode compatibility with rapid passivation layer formation, and low electronic conductivity.

Conclusions:

• The study successfully identified two promising sodium SIC materials, NPSC1 and NPSC2, for ASSSIBs.
• The integration of diverse crystal structure prediction methods proves effective for discovering novel SIC materials.
• These findings offer innovative strategies for the rational design of next-generation sodium superionic conductors.