Controllable synthesis of mesostructures from TiO2hollow to porous nanospheres with superior rate performance for lithium ion batteries

Uniform TiO₂ nanospheres from hollow, core-shell and mesoporous structures have been synthesized using quasi-nano-sized carbonaceous spheres as templates. The TiO₂ nanospheres formed after calcination at 400 °C are composed of ∼7 nm nanoparticles and the shells of the hollow TiO₂ nanospheres are as thin as a single layer of nanoparticles. The ultrafine nanoparticles endow the hollow and mesoporous TiO₂ nanospheres with short lithium ion diffusion paths leading to high discharge specific capacities of 211.9 and 196.0 mA h g^-1 at a current rate of 1 C (167.5 mA g^-1) after 100 cycles, and especially superior discharge specific capacities of 125.9 and 113.4 mA h g^-1 at a high current rate of up to 20 C. The hollow and mesoporous TiO₂ nanospheres also show superior cycling stability with long-term discharge capacities of 103.0 and 110.2 mA h g^-1, respectively, even after 3000 cycles at a current rate of 20 C.