Effect of Pb 6s2 lone pair on the potential flattening of fluoride-ion conduction in perovskite-type fluoride

Materials containing ns2 lone pairs exhibit superior fluoride-ion conductivity, acting as promising candidates for solid electrolytes in all-solid-state fluoride-ion batteries. However, the effect of lone pairs on fluoride-ion conduction remains unclear, especially for 6s2 in Pb2+. This study invest...

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Published inJournal of materials chemistry. A, Materials for energy and sustainability Vol. 12; no. 7; pp. 3989 - 3996
Main Authors Matsui, Naoki, Murakami, Miwa, Mori, Kazuhiro, Saito, Takashi, Shimizu, Keisuke, Suzuki, Kota, Kanno, Ryoji
Format Journal Article
LanguageEnglish
Published Cambridge Royal Society of Chemistry 13.02.2024
Subjects
Anions
Conduction
Conductivity
Crystal structure
Electronic structure
Fluorides
Ion currents
Ions
Lead
Magnetic resonance spectroscopy
Molten salt electrolytes
NMR
NMR spectroscopy
Nuclear magnetic resonance
Perovskites
Saddle points
Solid electrolytes
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Summary:Materials containing ns2 lone pairs exhibit superior fluoride-ion conductivity, acting as promising candidates for solid electrolytes in all-solid-state fluoride-ion batteries. However, the effect of lone pairs on fluoride-ion conduction remains unclear, especially for 6s2 in Pb2+. This study investigated the relationships between the ionic conductivity, crystal structure, and electronic structure of CsPb0.9K0.1F2.9. Cubic CsPb0.9K0.1F2.9 exhibited a low activation energy of 7.9 kJ mol−1, resulting in high conductivity at 223 K (1.0 × 10−3 S cm−1, bulk conductivity). 19F nuclear magnetic resonance spectroscopy confirmed facile local migration of the fluoride ions with a low activation barrier of 3.8 kJ mol−1. Theoretical calculations revealed that the fluoride ions migrated with a low migration energy via an exchange reaction between the Pb 6s lone pairs and fluoride ions. The localised lone pair in the PbF5 polyhedron stabilised the saddle-point structure and mitigated the migration barrier. These findings are beneficial for material design, providing superionic conductivity with a low migration barrier for fluoride ions as well as other anions, such as oxide and chloride.
ISSN:2050-7488
2050-7496
DOI:10.1039/d3ta06367d