The electrochemical sodiation of sb investigated by Operando X-ray absorption and 121 sb mössbauer spectroscopy
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Ali Darwiche (Université de Montpellier)
Marcus Fehse (Dutch-Belgian (DUBBLE), TU Delft - RST/Storage of Electrochemical Energy, Universite de Picardie Jules Verne)
Abdelfattah Mahmoud (Université de Liège)
Camille La Fontaine (DiffAbs Beamline Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin)
Bernard Fraisse (Université de Montpellier)
R. P. Hermann (Oak Ridge National Laboratory)
Marie Liesse Doublet (Université de Montpellier, CNRS FR3459, Universite de Picardie Jules Verne)
Laure Monconduit (Université de Montpellier, Universite de Picardie Jules Verne, CNRS FR3459)
Moulay T. Sougrati (CNRS FR3459, Universite de Picardie Jules Verne, Université de Montpellier)
G.B. More authors (External organisation)
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Abstract
In this study, we want to highlight the assets and restrictions of X-ray absorption spectroscopy (XAS) and Mössbauer spectroscopy for investigating the mechanism of the electrochemical reaction of antimony electrode materials vs. Na. For this, operando XAS was carried out during the first one and a half cycles, and the whole set of measured data was analysed using a statistical-chemometric approach, while low temperature Mössbauer spectroscopy measurements were carried out ex situ on selected samples stopped at different points of the electrochemical reaction. Complementary ab initio calculations were performed to support the experimental findings. Both techniques show that, upon the first sodiation, most Sb reacts with Na to form disordered Na
3
Sb. This step is accompanied by the formation of amorphous Sb as an intermediate. Upon inversion of the current Na
3
Sb is desodiated and an amorphous Sb phase, distinct from the pristine bulk Sb state, is gradually formed. However, both XAS and Mössbauer spectroscopy were unable to spot the formation of intermediate Na
x
Sb phases, which were evinced in previous works by operando Pair Distribution Function analyses. The results shown here clearly assign such failure to the intrinsic inability of both techniques to identify these intermediates.
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