We here present the synthesis of a new material, Na(VO)Fe(PO)F, by the sol-gel method. Its atomic and electronic structural descriptions are determined by a combination of several diffraction and spectroscopy techniques such as synchrotron X-ray powder diffraction and synchrotron X-ray absorption spectroscopy at V and Fe K edges, Fe Mössbauer, and P solid-state nuclear magnetic resonance spectroscopy. The crystal structure of this newly obtained phase is similar to that of Na(VO)(PO)F, with a random distribution of Fe ions over vanadium sites. Even though Fe and V ions situate on the same crystallographic position, their local environment can be studied separately using Fe Mössbauer and X-ray absorption spectroscopy at Fe and V K edges, respectively. The Fe ion resides in a symmetric octahedral environment, while the octahedral site of V is greatly distorted due to the presence of the vanadyl bond. No electrochemical activity of the Fe/Fe redox couple is detected, at least up to 5 V, whereas the reduction of Fe to Fe has been observed at ∼1.5 V versus Na/Na through the insertion of 0.5 Na into Na(VO)Fe(PO)F. Comparing to Na(VO)(PO)F, the electrochemical profile of Na(VO)Fe(PO)F in the same cycling condition shows a smaller polarization which could be due to a slight improvement in Na diffusion process thanks to the presence of Fe in the framework. Furthermore, the desodiation mechanism occurring upon charging is investigated by operando synchrotron X-ray diffraction and operando synchrotron X-ray absorption at V K edge.
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