Reference : Sodium Iron Sulfate Alluaudite Solid Solution for Na-ion Batteries: Moving Towards St...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
http://hdl.handle.net/2268/234342
Sodium Iron Sulfate Alluaudite Solid Solution for Na-ion Batteries: Moving Towards Stoichiometric Na2Fe2(SO4)3
English
Jungers, Thomas mailto [Université de Liège - ULiège > Département de chimie (sciences) > Chimie inorganique structurale >]
Mahmoud, Abdelfattah mailto [Université de Liège - ULiège > Département de chimie (sciences) > LCIS - GreenMAT >]
Malherbe, Cédric mailto [Université de Liège - ULiège > Département de chimie (sciences) > Chimie analytique inorganique >]
Boschini, Frédéric mailto [Université de Liège - ULiège > > Plateforme APTIS >]
Vertruyen, Bénédicte mailto [Université de Liège - ULiège > Département de chimie (sciences) > Chimie inorganique structurale >]
11-Mar-2019
Journal of Materials Chemistry A
Royal Society of Chemistry
7
8226-8233
Yes (verified by ORBi)
International
2050-7488
2050-7496
United Kingdom
[en] Alluaudites ; Na-ion batteries ; Sulfates ; Stoichiometry ; Solid solutions ; Precipitation ; Mössbauer spectroscopy
[en] Thanks to the inductive effect of the sulfate groups, sodium iron sulfate alluaudites display the highest electrode potential amongst the Fe-based compounds studied in sodium-ion batteries. Here, we report the synthetic strategy that has allowed us to obtain the elusive Na2Fe2(SO4)3 stoichiometric compound through a reverse-strike coprecipitation method in organic medium. We experimentally confirm the hypothesis that the stoichiometric compound transforms upon further heat treatment into the previously reported sodium-rich solid solution and an iron sulfate secondary phase. X-ray diffraction and 57Fe Mössbauer spectroscopy do not reveal any striking structure difference between the stoichiometric and Na-rich compounds, in agreement with the current understanding that the instability of the stoichiometric phase is due to the repulsion between Fe2+ ions in the Fe2O10 dimers bridged by sulfate groups. Despite less-than-optimal powder microstructure, electrochemical activity of the stoichiometric phase could be demonstrated through operando X-ray diffraction. These findings are expected to shift attention towards the (near)-stoichiometric compositions, which offer the highest theoretical specific capacities thanks to their optimal Na/Fe ratio.
Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS
Researchers ; Professionals
http://hdl.handle.net/2268/234342
10.1039/C9TA00116F
https://pubs.rsc.org/en/Content/ArticleLanding/2019/TA/C9TA00116F

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