Understanding the Surface Regeneration and Reactivity of Garnet Solid-State Electrolytes

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Garnet solid-electrolytes offer high energy density and thermal stability for lithium-metal batteries.
• Surface reactions with ambient atmosphere (CO2, H2O) create lithium hydroxide and carbonate, hindering processing.

Purpose of the Study:

• Investigate garnet surface layer decomposition under various gas conditions.
• Determine optimal processing parameters for stable garnet-based lithium-metal batteries.

Main Methods:

• Near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS).
• Grazing incidence X-ray diffraction (GIXRD).

Main Results:

• Heating to 500 °C in >= 1 mbar oxygen yields a clean garnet surface.
• Low oxygen partial pressures (Ar, vacuum) result in graphitic carbon deposition.
• Garnet surfaces react with moisture below 400 °C and CO2 below 500 °C.

Conclusions:

• Controlled oxygen atmosphere and exclusion of H2O/CO2 are essential for processing garnets.
• Symmetric cells with < 10 Ωcm² interface resistance achieved without interlayers.
• Demonstrated plating currents > 1 mA cm⁻² without dendrite formation.