Vertically Aligned Binder-Free TiO2 Nanotube Arrays Doped with Fe, S and Fe-S for Li-ion Batteries

Vertically aligned Fe, S, and Fe-S doped anatase TiO2 nanotube arrays are prepared by an electrochemical anodization process using an organic electrolyte in which lactic acid is added as an additive. In the electrolyte, highly ordered TiO2 nanotube layers with greater thickness of 12 mu m, inner diameter of approx. 90 nm and outer diameter of approx. 170 nm are successfully obtained. Doping of Fe, S, and Fe-S via simple wet impregnation method substituted Ti and O sites with Fe and S, which leads to enhance the rate performance at high discharge C-rates. Discharge capacities of TiO2 tubes increased from 0.13 mAh cm(-2)(bare) to 0.28 mAh cm(-2) for Fe-S doped TiO2 at 0.5 C after 100 cycles with exceptional capacity retention of 85 % after 100 cycles. Owing to the enhancement of thermodynamic and kinetic properties by doping of Fe-S, Li-diffusion increased resulting in remarkable discharge capacities of 0.27 mAh cm(-2) and 0.16 mAh cm(-2) at 10 C, and 30 C, respectively.

Automated summary

Vertically aligned Fe, S, and Fe-S doped anatase TiO2 nanotube arrays were successfully prepared by electrochemical anodization, with doping leading to enhanced rate performance and improved discharge capacities. The addition of Fe-S resulted in remarkable discharge capacities at high discharge rates, showcasing exceptional capacity retention after multiple cycles.