Template-free synthesis of homogeneous yolk-shell TiO sub(2) hierarchical microspheres for high performance lithium ion batteries

• Published in: Journal of power sources 2014-09, Vol.262, p.72-78
• Main Authors: Wang, Xiaobing, Wang, Yuanyuan, Yang, Lin, Wang, Kui, Lou, Xiangdong, Cai, Bibo
• Format: Article
• Language: English
• Subjects: Lithium batteries; Lithium-ion batteries; Microspheres; Nanoparticles; Ostwald ripening; Scanning electron microscopy; Shells; Specific surface; Titanium dioxide
• ISSN: 0378-7753
• DOI: 10.1016/j.jpowsour.2014.03.081

The homogeneous yolk-shell TiO sub(2) hierarchical microspheres (TiO sub(2) HYSHMs) consisting of small nanoparticles have been fabricated through a facile template-free solvothermal reaction followed by calcination. The obtained samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption/desorption analysis and Fourier transform infrared spectroscopy. It was found that the microspheres have porous shell (~ 100 nm in thickness) composed of small nanoparticles with an average diameter of 10 nm. The interspace between the yolk and shell is ~150 nm. The BET specific surface area and pore volume of the sample are 151.1 m super(2) g super(-1) and 0.23 cm super(3) g super(-1), respectively. Ostwald ripening processes are proposed to explain the growth mechanism of the TiO sub(2) HYSHMs based on a series of time-dependent experiments. As the anode materials for the lithium ion batteries, TiO sub(2) HYSHMs exhibit a high initial discharge capacity of 267.6 mAh g super(-1) at 0.25 C and retain 191 mAh g super(-1) even after 40 cycles, indicating good electrochemical performance. These good electrochemical performances could be attributed to the short Li-ion and electron pathways, and enough elastic buffer space to accommodate large volume variation of the special yolk-shell hierarchical structure.