A single-source molten salt synthesis of rod-shaped Na2Ti6O13 crystals

As one of the most potential negative electrode materials, Na2Ti6O13 is expected to play an important role in the area of high-performance battery. In this work, we have developed an easy, efficient and controllable method to prepare rod-shaped Na2Ti6O13 crystals. This approach utilized a single-source molten salt strategy and only needed to sinter a special precursor synthesized from an aqueous solution containing H3BO3 and (NH4)2TiF6 in presence of sodium salts. The component and shape of precursor crystals can be tuned by adjusting the reagent concentration and reaction temperature. By sintering precursor crystals in air at 900 °C for 30 min, Na2Ti6O13 with high crystallinity and purity can be obtained. X-ray diffraction and scanning electron micrographs results of different sintering times show that the sintering process can be divided into two steps. Firstly, the precursor crystals are converted to TiO2 (anatase) nano-particles and amorphous sodium salts. Subsequently, molten salt reaction occurs between amorphous sodium salts and TiO2 and forms rod-shaped Na2Ti6O13 crystals.