Creating Submicron-Sized Titanium Niobium Oxides with Rich Oxygen Vacancies by an Oxygen Filtering Effect of a Precoated Carbon Layer for High-Rate Lithium-Ion Electrodes

Titanium niobium oxide (TNO) has emerged as a promising high-safety anode material for next-generation, high-rate lithium-ion batteries. However, its practical application faces significant challenges due to inherent limitations in electronic conductivity and substantial ion migration resistance, primarily caused by particle overgrowth during conventional solid-phase sintering processes. To address these issues, we developed an innovative two-step sintering strategy to synthesize submicron-sized carbon-coated Ti₂Nb₁₀O_29-<i>x</i> with abundant oxygen vacancies (Ov-TNO@C). This approach features a unique carbon precoating process at 400 °C followed by controlled co-sintering with TiO₂, achieving three critical modifications: 1) carbon layer-mediated particle size control during sintering, 2) oxygen filtration during atomic interdiffusion between nano-TiO₂ and micron-sized Nb₂O₅, and 3) in situ generation of oxygen vacancies through Ti⁴⁺ → Ti³⁺ reduction. The optimized Ov-TNO@C demonstrates remarkable improvements in both electronic (1.6 × 10^-5 S cm^-1) and ionic conductivity, delivering exceptional electrochemical performance: high specific capacity (306 mAh g^-1 at 0.1 C), outstanding rate capability (181 mAh g^-1 at 10 C and 71.4 mAh g^-1 at ultrahigh 100 C), and superior cyclability (92.5% capacity retention after 2000 cycles at 10 C). This work establishes a universal strategy for engineering high-performance metal oxide electrodes through synergistic microstructure control and defect engineering, paving the way for the development of next-generation fast-charging battery systems.