Résumé
For the first time, cycling capability and life analysis of the FeSb2/Na battery are tested. Thanks to anappropriate carboxymethyl cellulose/carbon formulation, this electrode exhibits excellent electrochemicalperformances as negative electrode material for Sodium-Ion Batteries (SIB), sustaining areversible capacity exceeding 540 and 440 mAh/g over more than 130 cycles at a current of 36 and300 mA/g, respectively. Such performances overtake those of Sb in terms of cyclability under high rate,one of the best negative electrodes reported to date for SIB. In situ X-ray diffraction and low temperatureM€ossbauer spectroscopy analyses indicate that the reaction mechanism of the first sodiation of FeSb2 isbased on a conversion reaction, leading to the formation of a very efficient Na3Sb/metallic Fe0 nanosizedelectrode with an excellent capacity retention at relatively high rate. The reaction mechanism after thefirst discharge is based on a reversible alloying reaction (2Na3Sb --> 2Sb + 6Na), where iron is no moreinvolved. The role of Fe appears however to be crucial in the excellent cycling performances, likely due tothe increase of the electronic conductivity brought both by its nanosized nature and its homogenousdistribution in the electrode.