Sulfur-Doped Anatase Titanium Dioxide Induced by Polysulfide Chemistry for Enhanced Lithium-Ion Storage Performance

The substitutional anion doping for lattice oxygen in titanium dioxide (TiO₂) is an effective strategy for introducing oxygen vacancies and improving the conductivity, thereby enhancing the ion storage properties. Herein, sulfur-doped anatase titanium dioxide (S-TiO₂(A)) prepared by the annealing of a composite of sulfur/amorphous TiO₂ (S/TiO₂(a)), which is in situ formed through the simultaneous hydrolysis of titanium tetrachloride (TiCl₄) and disproportionation of polysulfide anions at an elevated temperature of 80 °C, is applied for high-performance lithium-ion storage. Meanwhile, three control samples are prepared. S/TiO₂(a) is treated with CS₂ to obtain TiO₂(a), which is then annealed to get TiO₂(A); rutile TiO₂ (TiO₂(R)) is prepared through the hydrolysis of TiCl₄ at 80 °C and the following annealing process. Compared to each of the undoped amorphous, anatase, and rutile TiO₂, S-TiO₂(A) shows superior electrochemical performance in terms of the capacity, initial Coulombic efficiency (ICE), rate capability, and cycling performance. Such an improvement can be ascribed to the enhanced electronic conductivity and boosted lithium-ion diffusion kinetics of S-TiO₂(A). Furthermore, the electrochemical mechanism is examined with ex situ electrochemical impedance spectrometry (EIS) and X-ray diffraction (XRD). This study demonstrates polysulfide anions as effective sulfur sources for the preparation of S-TiO₂(A) as a high-performance lithium-ion battery anode material.