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Transient Ruddlesden-Popper-Type Defects and Their Influence on Grain Growth and Properties of Lithium Lanthanum
Petruša Borštnar1,2, Goran Dražić3, Martin Šala4
1Advanced Materials Department, Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia.
ACS Nano
|April 9, 2024
Summary
This study presents a novel self-seeded grain growth method for fabricating coarse-grained lithium lanthanum titanate (LLTO) ceramics, crucial for enhancing all-solid-state battery performance by reducing grain boundary limitations.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Electrochemistry
Background:
- Lithium lanthanum titanate (LLTO) is a promising solid electrolyte for all-solid-state batteries.
- Grain boundaries (GBs) in LLTO ceramics limit ionic conductivity.
- Reducing GB fraction via coarse-grained structures is key to improving battery performance.
Purpose of the Study:
- To develop an alternative fabrication method for coarse-grained LLTO ceramics.
- To investigate microstructure evolution and grain growth mechanisms in LLTO.
- To correlate microstructure with ionic conductivity.
Main Methods:
- Synthesis of LLTO ceramics with high Li excess (Li:La:Ti = 11:15:25).
- Microstructural analysis using techniques like HAADF-STEM.
- Theoretical calculations to understand phase formation energetics.
- Measurement of total ionic conductivity.
Main Results:
- A self-seeded grain growth mechanism was identified, starting with a layered RP-type Li2La2Ti3O10 phase.
- Large, platelet-like grains (up to 10 μm thick, >100 μm long) of the RP phase formed initially.
- LLTO perovskite crystallized epitaxially on RP platelets, followed by recrystallization to defect-free LLTO via Ostwald ripening at higher temperatures.
- Achieved coarse-grained LLTO with total ionic conductivity of ~1 × 10^-4 S/cm.
Conclusions:
- The self-seeded grain growth approach effectively produces coarse-grained LLTO ceramics.
- Understanding RP phase formation and transformation is critical for controlling LLTO microstructure.
- The developed method offers a pathway to enhanced LLTO electrolytes for solid-state batteries.
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