Effect of surface microstructure on electrochemical performance of garnet solid electrolytes

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• Cubic garnet phases, specifically Al-substituted Li7La3Zr2O12 (LLZO), offer high ionic conductivity and stability with metallic lithium.
• High interfacial impedances have limited the practical application of LLZO in next-generation rechargeable batteries.
• Controlling surface microstructure, particularly grain boundaries, is crucial for reducing interfacial resistance.

Purpose of the Study:

• To fabricate LLZO heterostructured solid electrolytes.
• To correlate surface microstructure with interfacial electrochemical characteristics.
• To identify microstructural features that minimize interfacial resistance for stable battery cycling.

Main Methods:

• Fabrication of LLZO heterostructured solid electrolytes.
• High-resolution synchrotron polychromatic X-ray Laue microdiffraction for mapping grain orientations and distributions.
• Electrochemical characterization to determine interfacial properties.

Main Results:

• Electrochemical characteristics are highly dependent on surface microstructure.
• Small-grained LLZO samples exhibited significantly lower interfacial resistances compared to large-grained samples.
• Achieved low area specific resistances of 37 Ω cm(2), facilitating stable cycling with minimal polarization.

Conclusions:

• Microstructure engineering, especially grain size control, is key to overcoming interfacial impedance in LLZO solid electrolytes.
• The developed LLZO heterostructures demonstrate potential for practical implementation in high energy density batteries.
• Reduced interfacial resistance removes a major obstacle for solid electrolytes in advanced battery systems.