Hollow mesoporous frameworks without the annealing process for high-performance lithium-ion batteries: A case for anatase TiO2

Hierarchically porous hollow TiO2 microspheres composed of interconnect nanocrystals have been synthesized by a one-pot hydrothermal method without further thermal annealing. The as-prepared materials are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and electrochemical measurements. FESEM shows that the resultant hierarchical mesoporous TiO2 hollow microspheres (HTMs) comprised mesoporous shells with interconnected anatase nanocrystals. TEM reveals that the interconnected structure of hollow microspheres almost remained unchanged with increasing hydrothermal reaction time. The electrochemical measurements results showed that the initial Li insertion/extraction capacity of the electrodes obtained at 180 degrees C for 15 h is 158 mA h g(-1) and 151 mA h g(-1), at 5 C, respectively. Moreover, in the 100th cycle, the reversible capacity still remains about 131 mA h g(-1), indicating excellent cycling stability and good high-rate performance. The electrochemical impedance spectroscopy measurements indicated that the surface reaction kinetics of TiO2 nanocrystals were improved significantly, which may be attributed to fast charge transfer in the interconnected TiO2 nanocrystals structure. With the advantages of low cost and ease of processing, these HTMs are not only promising LIBs anode materials but also provide a conceptual route of fabricating oxides electrodes in high-performance LIBs in the future. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.