Synthesis of Monodisperse Mesoporous TiO2 Nanospheres from a Simple Double-Surfactant Assembly-Directed Method for Lithium Storage.

Exploring facile and reproducible methods to prepare mesoporous TiO2 nanospheres is crucial for improving the performance of TiO2 materials for energy conversion and storage. Herein, we report a simple and reproducible double-surfactant assembly-directed method to prepare monodisperse mesoporous TiO2 nanospheres. A double-surfactant system of n-dodecylamine (DDA) and Pluronic F127 was adopted to control the hydrolysis and condensation rates of tetrabutyl titanate in a mixture of water and alcohol at room temperature. In this process, the diameter size of mesoporous TiO2 nanospheres can be simply tuned from ∼50 to 250 nm by varying the concentration of H2O and surfactants. The double-surfactant system of DDA and F127 plays an effective role in determining the size, morphology, and monodispersity of mesoporous TiO2 nanospheres to reduce agglomeration during the sol-gel process. The resultant mesoporous anatase TiO2 nanospheres after solvothermal treatment at 160 °C are built of interpenetrating nanocrystals with a size of ∼10 nm, which are arranged to obtain a large number of connecting mesopores. Mesoporous TiO2 nanospheres with a small diameter size of around 50 nm possess a high surface area (∼160 m(2)/g) and mesopores with sizes of 4-30 nm. The small diameter size, high crystallinity, and mesoporous structure of TiO2 nanospheres lead to excellent performance in cycling stability and rate capability for lithium-ion batteries. After 500 cycles, the monodisperse mesoporous TiO2 nanospheres exhibit a charge capacity as high as 156 mAhg(-1) without obvious fade, and the Coulombic efficiency can reach up to 100%.