Effect of molten salt synthesis temperature on TiO2 and Li cycling properties

In this project, we synthesized TiO 2 compounds through the molten salt method (MSM) using Ti(IV) oxysulfate, as the Ti source. Molten salts in the ratio of 0.375 M LiNO 3 :0.180 M NaNO 3 :0.445 M KNO 3 were added and heated at temperatures of 145, 280, 380, and 480 °C for 2 h in air, respectively. A part of the sample prepared at 145 °C was further reheated to 850 °C for 2 h in air. X-ray diffraction studies showed that the amorphous phase was obtained when the sample was prepared at 145 °C, and polycrystalline to crystalline anatase phase was formed when heated from 280 to 850 °C, which is complementary to the results of selected area electron diffraction studies. Electrochemical properties were studied using galvanostatic cycling, cyclic voltammetry, and electrochemical impedance spectroscopy at a current density of 33 mA g −1 (0.1 C rate) and a scan rate of 0.058 mV s −1 , in the voltage range 1.0–2.8 V vs. Li. Electrochemical cycling profiles for the amorphous TiO 2 samples prepared at 145 °C showed single-phase reaction with a low reversible capacity of 65 mAh g −1 , whereas compounds prepared at 280 °C and above showed a two-phase reaction of Li-poor and Li-rich regions with a reversible capacity of 200 mAh g −1 . TiO 2 produced at 280 °C showed the lowest capacity fading and the lowest impedance value among the investigated samples.