Surface Fluorination Shielding of Sulfide Solid Electrolytes for Enhanced Electrochemical Stability in...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Sulfide solid electrolytes offer high ionic conductivity but lack electrochemical stability, hindering all-solid-state battery (ASSB) development.
• Limited electrochemical stability of sulfide electrolytes restricts the full potential of ASSBs.

Purpose of the Study:

• To develop a facile surface fluorination strategy for Li6PS5Cl solid electrolytes.
• To enhance the electrochemical stability and performance of ASSBs.

Main Methods:

• Surface fluorination of Li6PS5Cl using XeF2, a scalable dry process.
• Characterization using X-ray photoelectron spectroscopy, X-ray Rietveld refinement, nuclear magnetic resonance, and DFT calculations.
• Electrochemical testing in LiNi0.90Co0.05Mn0.05O2||(Li-In) half cells and pouch-type ASSBs.

Main Results:

• A uniform ≈37.3 nm fluorinated layer was formed on Li6PS5Cl, preserving 82.8% of its initial Li+ conductivity.
• Fluorination mechanism involves surface oxidative byproducts and F substitution, creating a robust cathode electrolyte interphase.
• Fluorinated Li6PS5Cl significantly improved discharge capacities, capacity retention, and safety in ASSBs.

Conclusions:

• Surface fluorination is an effective strategy to enhance the electrochemical stability of Li6PS5Cl electrolytes.
• The developed method offers a scalable approach for improving ASSB performance and safety.
• This work demonstrates the potential for practical, high-performance ASSBs using modified sulfide electrolytes.