Na2Fe2F7: a fluoride-based cathode for high power and long life Na-ion batteries

Despite the high energy density of layered-type cathode materials for Na-ion batteries, their two-dimensional crystal structure suffers a large volume change and phase transition during Na+ de/intercalation, which often results in their poor cycling performances. Thus, a robust three-dimensional fra...

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Bibliographic Details
Published in:Energy & environmental science 2021-03, Vol.14 (3), p.1469-1479
Main Authors: Park, Hyunyoung, Lee, Yongseok, Min-kyung Cho, Kang, Jungmin, Ko, Wonseok, Jung, Young Hwa, Jeon, Tae-Yeol, Hong, Jihyun, Kim, Hyungsub, Seung-Taek Myung, Kim, Jongsoon
Format: Article
Language:English
Subjects:
Batteries
Cathodes
Crystal structure
Cycles
Diffusion
Dimensional changes
Dimensional stability
Electrochemistry
Electrode materials
First principles
Fluorides
Flux density
Intercalation
Lithium
Phase transitions
Rechargeable batteries
Sodium
Sodium-ion batteries
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Summary:Despite the high energy density of layered-type cathode materials for Na-ion batteries, their two-dimensional crystal structure suffers a large volume change and phase transition during Na+ de/intercalation, which often results in their poor cycling performances. Thus, a robust three-dimensional framework with minimal structural change is required for stable electrochemical sodium storage. Here, we introduce an earth-abundant element-based trigonal-type Na–Fe–F compound (Na2Fe2F7) with three-dimensionally interconnected FeF6 octahedra and three-dimensional Na+ diffusion pathways. Through combined studies using first-principles calculations and experiments, we confirm that Na2Fe2F7 delivers excellent power-capability due to large three-dimensional Na+ diffusion pathways as well as ultra-long cycling performance due to negligible structural change during Na+ de/intercalation. These results will guide new insights for material discovery for high performance rechargeable batteries.
ISSN:1754-5692
1754-5706
DOI:10.1039/d0ee02803g