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Intergrowth Fluorite Slabs Modulate Interstitial Fluorine to Enhance Fluoride-Ion Conductivity
Daichi Kato1, Yosuke Matsuzaki1, Kohei Miyazaki1,2
1Department of Chemical Science and Engineering, Graduate School of Engineering, Kyoto University, Kyoto, Japan.
Angewandte Chemie (International Ed. in English)
|July 24, 2026
Summary
Researchers developed new layered fluoroiodide materials with intergrown triple and quadruple fluorite slabs. These novel structures exhibit enhanced fluoride-ion conductivity by optimizing fluorine concentration without doping, paving the way for advanced solid electrolytes.
Area of Science:
- Solid-state chemistry
- Materials science
- Ion conductivity
Background:
- Layered fluorite-type compounds are crucial for ion conductivity but thicker layers are challenging to synthesize and understand.
- Existing quadruple-layer compounds show high conductivity, but their complex structures hinder detailed analysis of ion transport mechanisms.
Purpose of the Study:
- To synthesize and characterize novel intergrowth fluoroiodide materials with controlled layered structures.
- To investigate the fluoride-ion conductivity of these new materials and compare them with simple layered analogs.
- To elucidate the structure-property relationships governing ion transport in these complex layered systems.
Main Methods:
- Synthesis of intergrowth fluoroiodides: Sn2Pb5F12I2 (n = 3 + 4) and Sn5Pb5F17I3 (n = 3 + 4 + 3).
- Evaluation of fluoride-ion conductivity for synthesized intergrowth phases and simple layered compounds (PbFI, Pb2BaF5I, Pb4F7I).
- Analysis of structural features, including slab thickness and intergrowth stacking, to correlate with conductivity.
Main Results:
- Two novel intergrowth fluoroiodides, Sn2Pb5F12I2 and Sn5Pb5F17I3, were successfully synthesized.
- These intergrowth phases exhibit enhanced fluoride-ion conductivity compared to simple quadruple-layer compounds, reaching up to ~0.8 × 10^-3 S cm^-1 at room temperature.
- The improved conductivity is attributed to modulated octahedral-site occupancy and tuned interstitial fluorine concentration via intergrowth stacking, avoiding detrimental doping effects.
Conclusions:
- Intergrowth stacking in layered fluorite-type materials is a viable doping-free strategy to enhance fluoride-ion conductivity.
- Controlling fluorite-slab thickness and intergrowth patterns offers a unified approach to tune anion carrier density and mobility.
- These findings provide new insights into designing advanced solid electrolytes for energy storage applications.
