Ultrasmall TiOxNanoparticles Rich in Oxygen Vacancies Synthesized through a Simple Strategy for Ultrahigh-Rate Lithium-Ion Batteries

Ultrasmall particle size (<10 nm) and rich oxygen vacancies are two sought-after characteristics for titanium dioxide (TiO2) to achieve high performance, namely, high rate and high storage capacity, when being used as an anode in lithium-ion batteries (LIBs). However, free TiO(2)particles simultaneously possessing both characteristics have not been reported, owing to the synthetic challenges. In this study, we report novel TiO(2)nanoparticles with ultrasmall size (ca. 5-8 nm) as well as rich oxygen vacancies synthesized through a simple strategy. Specifically, porous carbon nanoparticles were used to confine the TiO(2)precursor in the nanosized pores in the carbon nanoparticles, which were annealed at a high temperature in argon to produce the TiO(2)nanoparticles with ultrasmall size and rich oxygen vacancies and subsequently annealed in air to burn away the carbon nanoparticles to afford the so-called TiO(x)nanoparticles in a quantitative yield. The obtained anatase 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)(ca. 59 C), it still delivered a specific capacity of 90 mAh g(-1), which is five times that of the electrode made with the commercial anatase 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.