Synergistic effect of sodium ions and fluoride ions on synthesis of pure-phase TiO₂(B) nanorings

TiO₂(B) has received growing interest as negative electrode materials for Li-ion batteries in recent years. However, its metastability is an intrinsic obstacle for obtaining highly pure-phase TiO₂(B). In this study, we reported the synthesis of pure-phase TiO₂(B) nanorings with high crystallinity via one-pot hydrothermal method in the presence of sodium fluoride (NaF) solution. The as-prepared TiO₂(B) nanorings were systematically characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The TiO₂(B) nanorings had an outer diameter of about 400 nm and inner diameter of about 150 nm. Sodium fluoride was used as phase and morphology control agent. The growth mechanism revealed that sodium ions (Na⁺) and fluoride ions (F⁻) had a synergistic effect on the synthesis of pure-phase TiO₂(B) nanorings. The morphologies and crystalline phases were easily tailored by tuning the concentration of NaF. The effect of hydrothermal condition on growth of TiO₂(B) nanorings was investigated in detail. The as-prepared TiO₂(B) nanorings displayed high performance as negative electrode materials in Li-ion batteries.