The main disadvantage of using transition metal oxides for Na<sup>+</sup>-ion batteries is the sluggish kinetics of insertion of Na<sup>+</sup> ions into the structure. Here, we introduce nanosized anatase TiO<inf>2</inf> that is partially doped with fluorine (TiO<inf>2-δ</inf>F<inf>δ</inf>) to form electro-conducting trivalent Ti<sup>3+</sup> as an ultrafast Na<sup>+</sup> insertion material for use as an anode for sodium-ion batteries. In addition, the F-doped TiO<inf>2-δ</inf>F<inf>δ</inf> is modified by electro-conducting carbon nanotubes (CNTs) to further enhance the electric conductivity. The composite F-doped TiO<inf>2</inf> embedded in CNTs is produced in a one-pot hydrothermal reaction. X-ray diffraction and microscopic studies revealed that nanocrystalline anatase-type TiO<inf>2-δ</inf>F<inf>δ</inf> particles, in which fluorine is present with TiO<inf>2</inf> particles, are loaded on the CNTs. This yields a high electric conductivity of approximately 5.8Scm<sup>-1</sup>. The first discharge capacity of the F-doped TiO<inf>2</inf> embedded in CNTs is approximately 250mAh (g-oxide)<sup>-1</sup>, and is retained at 97% after 100 cycles. As expected, a high-rate performance was achieved even at the 100C discharging rate (25Ag<sup>-1</sup>) where the composite material demonstrated a capacity of 118mAhg<sup>-1</sup> under the 0.1C-rate charge condition. The present work also highlights a significant improvement in the insertion and extraction of Na<sup>+</sup> ions when the material was charged and discharged under the same rate of 35C (8.75Ag<sup>-1</sup>), delivering approximately 90mAh (g-oxide)<sup>-1</sup>.
- Anatase TiO<inf>2</inf>
- Carbon nanotubes
- Sodium batteries
ASJC Scopus subject areas
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)
- Electrical and Electronic Engineering