Facile synthesis of carbon-mediated porous nanocrystallite anatase TiO₂ for improved sodium insertion capabilities as an anode for sodium-ion batteries

Porous carbon-mediated nanocrystallite anatase TiO₂ composites are synthesized successfully via a simple dilatory hydrolysis-calcination method. The structural and morphological characterizations reveal that carbon-mediated TiO₂ with a carbon content of 9.9 wt % (C2-TiO₂) shows a combination of mesoporous and macroporous structures with a pore volume of 0.20 cm³ g⁻¹ and surface area of 40.3 m² g⁻¹. Notably, C2-TiO₂ delivered enhanced electrochemical performances of a high charge capacity of 259 mA h g⁻¹ at 0.1 C and a high rate performance of 110 mA h g⁻¹ after 150 cycles, even at 1 C. A significant decrease is also observed in the electrochemical impedance of the carbon-mediated samples, which explains superior electrochemical performance. Compared with the bare anatase TiO₂ (B-TiO₂), improved sodium storage capabilities of carbon-mediated samples are attributed to the participation of carbon to form a symbiotic structure with TiO₂, which not only increases pore volume of the samples but serves as highly conductive network to provide a Na⁺ diffusion path during the insertion/de-insertion of sodium ions. All of these encouraging results suggest that carbon-mediated TiO₂ has a great potential for improving sodium insertion capabilities with a facile and low-cost synthesis process.