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

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AbstractUltrasmall 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 TiO2 particles simultaneously possessing both characteristics have not been reported, owing to the synthetic challenges. In this study, we report novel TiO2 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 TiO2 precursor in the nanosized pores in the carbon nanoparticles, which were annealed at a high temperature in argon to produce the TiO2 nanoparticles with ultrasmall size and rich oxygen vacancies and subsequently annealed in air to burn away the carbon nanoparticles to afford the so‐called TiOx nanoparticles in a quantitative yield. The obtained anatase TiOx 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 TiO2 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.