Bulk-to-interface fluorination for stable and low-pressure all-solid-state lithium metal batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state lithium metal batteries offer high energy and safety but face challenges with stack pressure and performance.
• Mechanochemical failures and interface instability hinder practical application.

Purpose of the Study:

• To design a core-shell structured sulfide electrolyte with enhanced thermodynamic diffusion of fluorine.
• To improve the structural robustness and electrochemical performance of all-solid-state lithium metal batteries.

Main Methods:

• Developed a Li$_{5.4}$PS$_{4.4}$Cl$_{1.4}$F$_{0.2}$-0.2LiF core-shell sulfide electrolyte with a LiF nanoshell.
• Investigated fluorine atom diffusion into the positive electrode and its effect on interfaces.
• Fabricated and tested full cells and all-solid-state pouch cells under low stack pressure.

Main Results:

• The LiF nanoshell and F-enriched bulk stabilized electrode interfaces.
• Fluorine diffusion enhanced positive electrode structural integrity and mitigated failure.
• Full cells showed long cycle life, high-voltage stability, and wide temperature operation.
• Pouch cells achieved 85% capacity retention over 350 cycles at 2.5 MPa and >400 Wh/kg specific energy.

Conclusions:

• The bulk-to-interface fluorination strategy effectively addresses mechanochemical failures.
• This approach offers a viable pathway for developing low-pressure, long-life, high-energy all-solid-state batteries.