Résumé
With the aim of developing 3V all-solid-state lithium microbatteries, Fe$_2$(MoO$_4)_3$ thin films were prepared by radiofrequency magnetron sputtering from a home-madeFe$_2$(MoO$_4)_3$ target using optimized sputtering conditions. In addition to elemental analyses, Mössbauer spectroscopy and XPS analyses, showing that Mo$^{6+}$ and Fe$^{3+}$ are the main detected species, confirmed the stoichiometric character of the films. Post-deposition annealing was necessary to form well-crystallized thin films. The best electrochemical performance was obtained with those annealed at 500 °C which were able to deliver a stable reversible capacity close to the theoretical one, i.e. 2 Li$^+$ per Fe$_2$(MoO$_4)_3$ formula unit. The corresponding voltage curve displays a plateau with a low hysteresis located at 3.0 V/Li$^+$/Li and related to the Fe$_2$(MoO$_4)_3$ – Li$_2$Fe$_2$(MoO$_4)_3$ two-phase system. Therefore, it was demonstrated for the first time the possible use of Fe2(MoO4)3 thin films as positive electrodes for 3 V lithium microbatteries.