Issue 7, 2024

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

Abstract

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.

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

Supplementary files

Article information

Article type
Paper
Submitted
19 Oct 2023
Accepted
09 Jan 2024
First published
17 Jan 2024
This article is Open Access
Creative Commons BY license

J. Mater. Chem. A, 2024,12, 3989-3996

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

N. Matsui, M. Murakami, K. Mori, T. Saito, K. Shimizu, K. Suzuki and R. Kanno, J. Mater. Chem. A, 2024, 12, 3989 DOI: 10.1039/D3TA06367D

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