Enhancing Moisture Stability of Sulfide Solid-State Electrolytes by Reversible Amphipathic Molecular Coating

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state batteries (ASSBs) offer high energy density and safety advantages.
• Sulfide solid-state electrolytes (SSEs) exhibit desirable properties like high ionic conductivity but suffer from poor moisture stability, hindering mass production.
• Existing oxide ceramic and polymer electrolytes have limitations compared to sulfides.

Purpose of the Study:

• To develop a novel surface modification strategy to enhance the moisture stability of sulfide SSEs.
• To investigate the effectiveness of amphipathic organic molecules for protecting SSEs from water degradation.
• To ensure the surface treatment is reversible and does not impede battery performance.

Main Methods:

• A reversible surface coating strategy using amphipathic organic molecules was employed.
• Ultrathin layers of 1-bromopentane were coated onto sulfide SSEs (e.g., Li₇P₂S₈Br_0.5I_0.5) via Van der Waals force.
• First-principles calculations were used to determine adsorption energies of 1-bromopentane and water on SSE surfaces.

Main Results:

• The 1-bromopentane coating significantly enhanced the moisture stability of sulfide SSEs by repelling water molecules.
• First-principles calculations confirmed a more negative adsorption energy for 1-bromopentane than water, indicating stronger binding to the SSE surface.
• The amphipathic molecular layer minimally impacted ionic conductivity and was reversibly removable at low temperatures (160 °C).

Conclusions:

• A novel and effective reversible surface coating strategy using 1-bromopentane enhances the moisture stability of sulfide SSEs.
• This approach addresses a critical challenge for the mass production and processing of moisture-sensitive SSEs.
• The findings open new avenues for surface engineering of energy materials, accelerating the deployment of ASSBs.