Lithium Insertion Mechanism in Iron‐Based Oxyfluorides with Anionic Vacancies Probed by PDF Analysis

ChemistryOpen

Dr. Damien Dambournet¹  Dr. Karena W. Chapman²  Dr. Mathieu Duttine³  Dr. Olaf Borkiewicz²  Dr. Peter J. Chupas² 

[1] E-mail address: 关键词: anionic partitioning;    cathode materials;    ferric fluoride;    pair distribution function;   

DOI  :  10.1002/open.201500031

来源: Wiley

【 摘 要 】

Abstract

The mechanism of lithium insertion that occurs in an iron oxyfluoride sample with a hexagonal–tungsten–bronze (HTB)-type structure was investigated by the pair distribution function. This study reveals that upon lithiation, the HTB framework collapses to yield disordered rutile and rock salt phases followed by a conversion reaction of the fluoride phase toward lithium fluoride and nanometer-sized metallic iron. The occurrence of anionic vacancies in the pristine framework was shown to strongly impact the electrochemical activity, that is, the reversible capacity scales with the content of anionic vacancies. Similar to FeOF-type electrodes, upon de-lithiation, a disordered rutile phase forms, showing that the anionic chemistry dictates the atomic arrangement of the re-oxidized phase. Finally, it was shown that the nanoscaling and structural rearrangement induced by the conversion reaction allow the in situ formation of new electrode materials with enhanced electrochemical properties.

【 授权许可】

CC BY-NC   
© 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

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