January 2025
Journal of Materials Science
This study examines the continuous phase transition of NaBr-doped Li4Ti5O12 during calcination, focusing on the migration and evolution of Li⁺, Na⁺, and Br⁻ and their impact on the transition. Results from high-temperature in situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations indicate that NaBr incorporation increased the TiO2–Li2TiO3 transition temperature and reduced the Li2TiO3–Li4Ti5O12 transition temperature. An appropriate amount of Li⁺ was doped into TiO2 at low temperatures. Notably, with increasing temperature, Na⁺ was doped into the TiO2 cell through the gap, while Br⁻ was adsorbed on the surface of TiO2 without entering the TiO2 cell. With the continuous increase in the temperature and doping of Li⁺, TiO2 transforms into Li2TiO3. Na⁺ and Br⁻ gain more energy, Na⁺ enters the Li2TiO3 unit cell for gap doping, and Br⁻ enters the Li2TiO3 unit cell to replace O²⁻, promoting the transformation of Li2TiO3 to Li4Ti5O12. Overall, this research provides an intrinsic connection between the microscopic properties of anions and cations during NaBr-doped Li4Ti5O12 phase transition, clarifies the states of Li⁺, Na⁺, and Br⁻ in this transition, and offers a theoretical basis for the states of anions and cations during continuous Li4Ti5O12 phase transition.