Fluoride-ion conversion alloy for fluoride-ion batteries

To realize the full potential of fluoride-ion batteries with a significantly high energy density (larger than 1000 W h kg −1 ), it is a prerequisite to develop another conceptual cathode material beyond the current pure metals. This is because pure metals can only be fluorinated on the surface with...

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Bibliographic Details
Published in:Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2022-02, Vol.10 (7), p.3743-3749
Main Authors: Nakayama, Kei, Ishikawa, Ryo, Tojigamori, Takeshi, Miki, Hidenori, Iba, Hideki, Shibata, Naoya, Ikuhara, Yuichi
Format: Article
Language:English
Subjects:
Alloying elements
Alloys
Batteries
Cathodes
Crystals
Electrode materials
Fluorides
Fluorination
Flux density
Hydrogen storage materials
Intermetallic compounds
Lanthanum fluorides
Metals
Nanocrystals
Scanning transmission electron microscopy
Thickness
Transmission electron microscopy
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Summary:To realize the full potential of fluoride-ion batteries with a significantly high energy density (larger than 1000 W h kg −1 ), it is a prerequisite to develop another conceptual cathode material beyond the current pure metals. This is because pure metals can only be fluorinated on the surface with typically less than 10 nm depth. To overcome this issue, we show here that well-established hydrogen storage alloys such as LaNi 5 could be promising candidates for cathode materials in fluoride-ion batteries, where the reversible capacity of LaNi 5 is 396 A h kg −1 . By using atomic-resolution scanning transmission electron microscopy, we elucidate that LaNi 5 particles are first decomposed into LaF 3 and Ni nanocrystals in the charge process. A nano-scale network is formed by LaF 3 and Ni nanocrystals during the charge process, which maintains F − -ion and electric conductivities in the particles. Furthermore, Ni – one of the most difficult elements to fluorinate – can be fluorinated and defluorinated in the subsequent charge and discharge processes, because of the spontaneous formation of Ni nanocrystals which are smaller than the passivation layer thickness and LaF 3 nano-scale network. Our results suggest that an intermetallic alloy containing two function-sharing elements could be useful to explore higher capacity cathodes in fluoride-ion batteries.
ISSN:2050-7488
2050-7496
DOI:10.1039/D1TA09324J