Size-Tunable Single-Crystalline Anatase TiO2 Cubes as Anode Materials for Lithium Ion Batteries

Single-crystalline anatase TiO2 cubes enclosed by {100} and {001} facets with tunable size, as designed based on the special three zigzag lithium diffusion paths along [100], [010], and [001] directions, were obtained through hydrothermal crystallization of TiO2 in a quaternary solution consisting of tetrabutyl titanate, acetic acid, water, and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmin][BF4]). The crystalline type and shape of as-prepared samples were confirmed by X-ray diffraction and scanning and transmission electron microscopes (XRD, SEM, and TEM). Particularly, selected area electron diffraction (SAED) patterns, high-resolution TEM images, and fast Fourier transformation (FFT) patterns of the plane and side view are given to determine the exposed {100} and {001} facets. Significantly prolonged plateaus that are very practical for power management and constant voltage output were achieved by the anatase TiO2 cubes in comparison with TiO2 nanoparticles. Besides, excellent cycle stability was presented through a long loop of discharge/charge processes with both shape and crystallinity well preserved, as ex situ SEM and XRD characterization manifested.