Ultrasmall TiOx Nanoparticles Rich in Oxygen Vacancies Synthesized by a Simple Strategy for Ultrahigh-Rate Lithium Ion Batteries

Ultrasmall particle size and rich oxygen vacancies are two sought-after characteristics for TiO 2 to achieve high performance. However, TiO 2 particles  possessing both characteristics have not been reported due to the synthetic challenges. Here, we report novel TiO 2 nanoparticles with ultrasmall size (5-8 nm) as well as rich oxygen vacancies synthesized through a simple strategy. Specifically, porous carbon nanoparticles were used to confine a TiO 2 precursor in the nanosized pores in the carbon nanoparticles, which were annealed in argon to produce the TiO 2 nanoparticles with utrasmall size and rich oxygen vacancies and subsequently annealed in air to burn away the carbon nanoparticles to afford the TiO x nanoparticles. The obtained TiO x nanoparticles showed an exceptional ultrahigh-rate lithium storage capability. A record reversible specific capacity of 235 mAh g -1 was achieved at the current density of 0.1 A g -1 . Even at an ultrahigh rate of 10 A g -1 it still delivered a specific capacity of 90 mAh g -1 , which is 5 times that of the electrode made with the commercial TiO 2 nanoparticles. Furthermore, this electrode also showed an excellent cycling performance with capacity retentions of 87% and 90% at high rates of 1 A g -1 and 5 A g -1 , respectively, after 1000 cycles. The strategy reported in this work can potentially be a universal method for synthesis of other metal oxides with ultrasmall particle size and rich oxygen vacancies.