Recently, Sungkyunkwan University in South Korea proved that nano Na5Ti3F14/ carbon nanocomposites as the negative electrode of sodium ion batteries have excellent electrochemical properties. The results show that the Na5Ti3F14 phase can store ~8.33 mol Na ions through the following conversion reaction.

Na5Ti3F14 + 9Na + 9e-⇔3Ti + 14NaF

This reaction has been clearly confirmed by X-ray diffraction, synchrotron X-ray adsorption spectroscopy and other out-of-situ analyses.

By X-ray diffraction, X-ray absorption near edge structure and X-rayphotoelectron spectroscopy, it was confirmed that Na5Ti3F14 underwent a reversible transformation/reverse transformation reaction  during charging and discharging. Thus, Na5Ti3F14 shows that despite the conversion reaction, at 1000 mA g-1, with an acceptably low operating voltage and a high coulomb efficiency of more than 99%, the capacity retention rate remains around 78% over 300 cycles.