A novel pineapple-structured Si/TiO2 composite as anode material for lithium ion batteries

Nanoscaled Si is successfully wrapped with different contents of nano-TiO2 (the molar ratios of Si/TiO2 composites are 1:1, 1:2, 1:3, 1:4 and 1:5, respectively) to form a novel pineapple structure. X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) are utilized to characterize the structure, component, chemical environment and morphology of the composite. The investigation in cycling performances demonstrates that Si/TiO2 with molar ratio of 1:4 exhibits the best cycling stability, with specific capacity of 593 mA h g−1 after 50 cycles at 0.1 C, much higher than those of the other composites and the pristine material. Cyclic voltammetry (CV) profiles are also measured and compared. It is believed that the outside TiO2 particles act as buffer against the huge volume change of Si during repeated alloying and de-alloying, which explains the improved electrochemical performances.