TiO₂-Sn/C composite nanofibers with high-capacity and long-cycle life as anode materials for sodium ion batteries

The novel TiO₂-Sn/C composite nanofibers have been successfully fabricated by a simple and facile electrospinning process. A small amount of metal tin interacts with TiO₂ nanoparticles in a carbon matrix, which makes TiO₂-Sn/C nanofibers have the stability of TiO₂ and the high capacity of Sn. At the same time, the TiO₂-Sn/C nanofibers reveal an improved diffusion coefficient of sodium ions due to a small amount of Sn nanoparticles incorporation. Compared with TiO₂/C nanofibers, the TiO₂-Sn/C nanofibers electrode shows significantly improved specific capacity, substantial cycling stability, and remarkable rate capability. It delivers high reversible capacity of 255 mA h g⁻¹ at current densities of 0.05 A g⁻¹ in the range of 0.01–2.5 V vs. Na/Na⁺, and has specific capacities of 214 and 147 mA h g⁻¹ at current densities of 0.5 and 4 A g⁻¹, respectively. Furthermore, TiO₂-Sn/C nanofibers electrode demonstrates a discharge capacity 190.8 mA h g⁻¹ with 95.4% retention after 1000 cycles at 1 A g⁻¹ (the initial and second discharge capacity is 483 and 201 mA h g⁻¹, respectively). Even up to 5 A g⁻¹, the discharge capacity of 134.3 mA h g⁻¹ with 83.9% retention is obtained after 1000 cycles. Outstanding electrochemical performance makes TiO₂-Sn/C nanofibers as a hopeful anode material for sodium-ion batteries and to be applied in the field of large-scale energy storage.