Argyrodite Sulfide Electrolytes with Dry Atmospheric Stability for All-Solid-State Lithium Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Sulfide electrolytes are crucial for all-solid-state lithium batteries but suffer from air instability and poor solvent compatibility, hindering scalable manufacturing.
• Argyrodite sulfide electrolytes, specifically Li6PS5Cl and Li5.4PS4.4Cl1.6, react with oxygen and carbon dioxide in the air.
• Li5.4PS4.4Cl1.6 demonstrates lower stability against O2 and CO2 due to a weaker P-Cl bond in the PS3Cl motif, as supported by DFT calculations.

Purpose of the Study:

• To systematically investigate the effects of major air components (N2, O2, CO2) on argyrodite sulfide electrolytes.
• To enhance the stability and processability of sulfide electrolytes for practical all-solid-state lithium battery applications.
• To develop a stable and high-performance sulfide electrolyte membrane for lithium metal batteries.

Main Methods:

• Systematic investigation of argyrodite sulfide electrolytes (Li6PS5Cl, Li5.4PS4.4Cl1.6) exposed to N2, O2, and CO2.
• Density functional theory (DFT) calculations to analyze the P-Cl bond strength in the PS3Cl motif.
• Fabrication and characterization of oxygen-doped sulfide electrolytes (Li6.05PS4.9O0.1Cl1.05, Li5.3PS4.2O0.2Cl1.5) and their performance in all-solid-state batteries.

Main Results:

• Oxygen-doped electrolytes (Li6.05PS4.9O0.1Cl1.05, Li5.3PS4.2O0.2Cl1.5) exhibit improved stability against O2 and CO2 due to enhanced free energy changes for oxidation, suppressing PS4(3-) unit decomposition.
• Li5.3PS4.2O0.2Cl1.5 demonstrates excellent tolerance to sec-butyl acetate and can be processed into a 12 µm thick membrane with high ionic conductivity (2.34 mS cm-1) via wet-coating.
• The Li5.3PS4.2O0.2Cl1.5 electrolyte enables stable cycling against lithium metal for over 10,000 hours at 0.1 mA cm-2.
• A LiNbO3@LiCoO2|Li5.3PS4.2O0.2Cl1.5|Li battery achieved 81.6% capacity retention after 1000 cycles at 1 C.
• A LiNbO3@LiCoO2||Li pouch cell utilizing the Li5.3PS4.2O0.2Cl1.5 membrane showed 86.6% capacity retention after 250 cycles at 0.1 C.

Conclusions:

• Oxygen doping significantly enhances the air stability of argyrodite sulfide electrolytes by improving resistance to O2 and CO2 oxidation.
• The developed oxygen-doped Li5.3PS4.2O0.2Cl1.5 electrolyte is suitable for scalable manufacturing via wet-coating and demonstrates excellent electrochemical performance and interfacial stability with lithium metal.
• This work presents a promising pathway for developing stable and high-performance sulfide-based solid electrolytes for next-generation all-solid-state lithium batteries.