Effect of Cl-Doping on K₃PS₄ as a Superionic Solid Electrolyte for K-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Solid-state K-ion batteries (KIBs) are promising alternatives to Li-ion batteries.
• Sulfide solid-state electrolytes (SSEs) face challenges with low ionic conductivity and poor moisture stability.
• K3PS4 is a cost-effective SSE candidate needing improved performance.

Purpose of the Study:

• Investigate the impact of Cl-doping on K-ion diffusion in K3PS4.
• Enhance ionic conductivity and moisture resistance of K3PS4 for KIB applications.
• Provide theoretical insights for developing stable and conductive sulfide SSEs.

Main Methods:

• Utilized DeepMD simulations to study K-ion diffusion mechanisms.
• Employed Metadynamics simulations to assess electrolyte stability against water.
• Calculated activation energy and ionic conductivity.
• Analyzed band gap for electronic properties.

Main Results:

• Cl-doping creates potassium vacancies, facilitating K+ transport and cooperative hopping.
• Optimized cubic K2.9375PS3.9375Cl0.0625 shows low activation energy (0.22 eV) and conductivity (1.11 × 10^-4 S cm^-1 at 300 K).
• Cl-doping increases the water-dissociation barrier, enhancing hydrolytic stability.
• Band gap remains largely unchanged (2.76 eV), preserving electronic insulation.

Conclusions:

• Cl-doping is an effective strategy to improve ionic conductivity and stability of K3PS4 SSEs.
• The findings support the development of advanced sulfide SSEs for practical KIBs.
• This study provides a theoretical foundation for optimizing K3PS4-based solid electrolytes.