| Autor: |
Palomares, Verónica, Iturrondobeitia, Amaia, Sanchez-Fontecoba, Paula, Goonetilleke, Damian, Sharma, Neeraj, Lezama, Luis, Rojo, Teófilo |
| Zdroj: |
Inorganic Chemistry; January 2020, Vol. 59 Issue: 1 p854-862, 9p |
| Abstrakt: |
The sodium–vanadium fluorophosphate family has been actively investigated recently, but few examples tackle chemical doping or the substitution of vanadium. This work presents a series of iron-doped compounds Na3V2–yO2–yFey(PO4)2F1+y(y≤ 0.3) prepared by hydrothermal synthesis with low iron content. The amount of iron in the structure is confirmed by X-ray and neutron powder diffraction, electronic paramagnetic resonance, magnetic susceptibility measurements, and solid-state nuclear magnetic resonance (ssNMR). The degree of vanadium substitution, together with the solubility limit for iron in sodium–vanadium fluorophosphates, has been calculated by ssNMR and magnetic susceptibility measurements to be y= 0.3 based on the synthetic route used here. The introduction of small amounts of Fe3+to the structure leads to the reduction of a fraction of V4+to V3+, and the voltage profiles do not change with the introduction of iron to the structure. In situ synchrotron X-ray diffraction demonstrates that the electrochemical–structural changes during charge and discharge are very similar to those observed in the V3+/V4+mixed-valent Na3V2O1.6(PO4)2F1.4, which could be related to the existence of both iron dopant and V3+in the phase. |
| Databáze: |
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