NaFeTiO4 nanorod/multi-walled carbon nanotubes composite as an anode material for sodium-ion batteries with high performances in both half and full cells

NaFeTiO4 nanorods of high yields （with diameters in the range of 30-50 nm and lengths of up to 1-5 μm） were synthesized by a facile sol-gel method and were utilized as an anode material for sodium-ion batteries for the first time. The obtained NaFeTiO4 nanorods exhibit a high initial discharge capacity of 294 mA·h·g^-1 at 0.2 C （1 C = 177 mA·g^-1）, and remain at 115 mA·h·g^-1 after 50 cycles. Furthermore, multi-walled carbon nanotubes （MWCNTs） were mechanically milled with the pristine material to obtain NaFeTiO4/MWCNTs. The NaFeTiO4/MWCNTs electrode exhibits a significantly improved electrochemical performance with a stable discharge capacity of 150 mA·h·g^-1 at 0.2 C after 50 cycles, and remains at 125 mA·h·g^-1 at 0.5 C after 420 cycles. The NaFeTiO4/MWCNTs//Na3V2（PO4）3/C full cell was assembled for the first time; it displays a discharge capacity of 70 mA·h·g^-1 after 50 cycles at 0.05 C, indicating its excellent performances. X-ray photoelectron spectroscopy, ex situ X-ray diffraction, and Raman measurements were performed to investigate the initial electrochemical mechanisms of the obtained NaFeTiO4/MWCNTs.