Direct growth of mesoporous Sn-doped TiO2 thin films on conducting substrates for lithium-ion battery anodes

Abstract

We demonstrate the controlled doping of Sn into mesoporous TiO₂ thin films, by a facile direct growth on conducting substrates (e.g. Ti) using the ligand-assisted evaporation-induced self-assembly method. The obtained Sn-doped mesoporous TiO₂ thin films are polycrystalline with an anatase structure. The mesoporous TiO₂ frameworks provide efficient ion transport pathways and structural stability for Li⁺ insertion. The in situ incorporation of Sn dopants into the mesoporous frameworks improves the charge transfer efficiency and the theoretical Li⁺ storage capacity of the electrode. In addition, the obtained mesoporous structures on Ti substrates provide close contact between the active material and the current collector, thus reducing the contact resistance and enhancing the charge transfer. As proof-of-concept, lithium-ion battery measurements of the Sn-doped mesoporous TiO₂ thin film anodes with different Sn doping ratios show that the specific reversible capacity increases to a maximum with ∼6% Sn doping ratio (∼252.5 mA h g⁻¹ at 0.5 C) compared to our best pristine mesoporous TiO₂ thin film anodes (100.8 mA h g⁻¹ at 0.5 C), and then decreases at higher Sn doping ratios. Moreover, the Sn-doped mesoporous TiO₂ thin films exhibit an excellent cycling stability, thus suggesting a potential approach for fabricating mesoporous oxide thin films with controlled doping for stable LIB storage.