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Tailoring Li-Al-O Interphases in Garnet-Type Solid-State Electrolytes via Powder Atomic Layer Deposition
Michael K Steinhoff1,2, Anna Domgans1,2, Jehad Ahmed1,2
1Institute of Energy Technologies─Fundamental Electrochemistry (IET-1), Forschungszentrum Jülich, 52428 Jülich, Germany.
ACS Applied Materials & Interfaces
|March 25, 2026
Summary
Atomic layer deposition (ALD) of Al2O3 coatings on garnet-type solid-state electrolytes (SSEs) creates a tunable Li-Al-O interphase. Optimized coatings enhance ionic conductivity and critical current density for solid-state batteries.
Area of Science:
- Materials Science
- Electrochemistry
- Nanotechnology
Background:
- Garnet-type solid-state electrolytes (SSEs), like Li6.4La3Zr1.4Ta0.6O12 (LLZTO), are crucial for solid-state lithium metal batteries but suffer from high interfacial resistance and lithium dendrite issues.
- Atomic Layer Deposition (ALD) provides precise control over nanoscale surface modifications, offering a potential solution for improving SSE performance.
- Understanding the interfacial evolution and its impact on ion transport is key to designing advanced SSEs.
Purpose of the Study:
- To investigate the effects of Al2O3 ALD powder coatings on the structural, chemical, and electrochemical properties of LLZTO SSEs.
- To elucidate the formation mechanism of the interphase layer and its influence on sintering behavior and ion transport.
- To establish design principles for ALD-guided interphase engineering for enhanced solid-state battery performance.
Main Methods:
- Coating LLZTO powders with varying thicknesses of Al2O3 using Atomic Layer Deposition (ALD).
- Characterization using 27Al magic angle spinning NMR, X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy (STEM) to analyze structural and chemical changes.
- High-temperature sintering followed by electrochemical evaluation, including ionic conductivity and critical current density measurements.
Main Results:
- ALD coating induces lithium diffusion, forming a nanocrystalline, compositionally graded Li-Al-O interphase.
- High-temperature sintering of coated LLZTO results in a multiphase microstructure (LiAlO2, Li2ZrO3, LaAlO3) whose phase fractions are controlled by ALD coating thickness.
- Medium-thickness ALD coatings (~6.8 nm, 25 cycles) optimize densification and ion transport, yielding the best electrochemical performance (0.39 mS cm-1 ionic conductivity, 0.35 mA cm-2 critical current density).
Conclusions:
- ALD-guided modification of LLZTO surfaces provides mechanistic insights into interphase formation and sintering control.
- Tailoring interphase properties through ALD coating thickness offers a scalable strategy to enhance the performance of garnet-type SSEs.
- This approach advances the development of safer and more efficient solid-state lithium metal batteries.
