Ultraviolet-Induced Interfacial Crystallization of Uniform Nanoporous Biphasic TiO2 Spheres for Durable Lithium-Ion Battery

Porous TiO2 has been widely studied as an anode material of lithium-ion battery, most of which, however, are crystalline with a limited surface area (e.g., 50-120 m(2)/g) and a large pore size of 10-20 nm greatly exceeding the ion radium of Li+ ion and its complexes. Herein a facile UV-induced interfacial crystallization method is developed for the sol-gel-derived amorphous hydrous TiO2 spheres (HTS) at ambient condition. Tuning the dispersant (e.g., ethanol, H2O, methanol, or their mixture) and the wavelength of the light source allows for selective control over the crystal phase of anatase, rutile, or their biphase formed at the spherical surface, although the total crystallinity remains poor. The optimal nanoporous biphasic TiO2 spheres of anatase and rutile upon 254 nm UVC irradiation of HTS in H2O and methanol mixed solution for 4 h exhibit an ultralarge surface area of 358.1 m(2)/g and comprise numerous micropores and small mesopores (similar to 3.31 nm), rendering the fabricated LIB with high current density, rate capacity, cycle performance, and Li+ transfer rate. A superior electrochemical reversible specific capacity of 128.6 mAh/g can be attained over 1000 cycles of charge/discharge processes at 1C rate. Our simple and general synthesis strategy is promising for the rational design of various photostable materials with improved crystallinity, tunable crystal phases, large surface area, and applicable pore size.