One-step synthesis of hexagonal TiOF2 as high rate electrode material for lithium-ion batteries: research on Li intercalation/de-intercalation mechanism

Abstract Two novel nanocrystalline materials, hexagonal TiOF 2 (hTiOF 2 , space group R 3 ¯ c hexagonal) nanocubes and LiTiOF 2 (space group R3c hexagonal), were prepared by a one-step solvothermal method and the lithiation of hTiOF 2 precursor, respectively. All the products have been characterized by means of X-ray diffraction, thermogravimetry, scanning electron microscopy, transmission electron microscope and high resolution transmission electron microscope. Furthermore, Rietveld analysis has been used to evaluate the structure of LiTiOF 2 . The electrochemical properties were evaluated using the products as cathode for half-cells in lithium-ion batteries (LIBs). It is confirmed that hTiOF 2 and LiTiOF 2 have the same frame and the Li intercalation/de-intercalation mechanism of hTiOF 2 is discussed. An electrochemical activation process is confirmed in the charge-discharge cycles of hTiOF 2 half-cells. The hTiOF 2 half-cell after activation delivered a high specific capacity of 200 mAh g −1 at 1C in the range of 3.0–0.8 V and maintained a specific capacity of 120 mAh g −1 at 20C over 1000 cycles, which is a very satisfying performance.