Anatase titanium dioxide nanosheets with exposed (001) high-energy facets for high-performance lithium-ion batteries
Date of Issue2012
School of Chemical and Biomedical Engineering
Lithium-ion batteries have become the dominate power sources for portable electronic devices, because of their unmatched energy density. However, the low power density hinders their practical application in electric vehicles. The major challenge lies in the significant deterioration of battery performance at increased current rates. The research work presented in this thesis is focused on the synthesis of novel anatase titanium dioxide (TiO2) nanosheets with exposed (001) high-energy facets and their application as the anode material for high-power lithium-ion batteries. A facile hydrothermal method is first developed to synthesize free-standing TiO2 nanosheets with approximately 60% exposed (001) facets, using titanium isopropoxide as the TiO2 precursor and hydrofluoric acid as the F donor to stabilize the high-energy facets. These as-prepared unique nanosheets demonstrate excellent lithium storage properties with superior high-rate performance, because of the exposed (001) facets granting highly efficient diffusion of Li+ in the anatase framework. Secondly, a simple F-free solvothermal method is proposed to synthesize hierarchical structure assembled from large ultrathin TiO2 nanosheets bound by (001) facets on the top and bottom, where diethylenetriamine (DETA) serves as the capping agent to stabilize the high-energy facets. Due to the ultrathin feature of these nanosheet constituents, the percentage of the exposed (001) facets is close to 100%. Such hierarchical structure also renders the material with high thermal stability, as no morphological change is observed when the sample is calcined at 600 oC for the removal of the organic compound. Moreover, by adding different nanotemplates into this solvothermal system, various types of hollow structures with shells constructed by these TiO2 nanosheets are produced. When applied in LIBs, the samples demonstrate greatly enhanced lithium storage properties, owning to the ultrathin TiO2 nanosheets with highly efficient lithium diffusion and short diffusion path.