Oxygen-Deficient Tunnel-Structured TiNb ₂ O ₇ for High-Rate, Long-Cycle Lithium Storage, and Subzero-Temperature Performance

TiNb2O7 (TNO) exhibits remarkable suitability for power batteries, attributed to its high safety profile, substantial theoretical specific capacity, and outstanding structural stability. However, its practical adoption is hindered by poor electronic conductivity and slow lithium-ion transport kinetics. Herein, the micron-scale anoxic electrode materials with a uniform morphological tunnel structure (T-TNO-x) were successfully prepared by a “Fluorine Chemistry-Assisted Homogeneous Coprecipitation–Hydrothermal Method”. Benefiting from the synergistic effect of the tunnel structure and oxygen vacancies, T-TNO-x efficiently facilitates Li+ diffusion paths and enhances the electronic conductivity, thereby achieving a significant boost in the pseudocapacitive effect. As a result, T-TNO-x exhibits outstanding electrochemical performance. Specifically, at a high current density of 10 C, it delivers a capacity of 182.2 mA h g–1 with an impressive retention rate of 88.2% after 2000 cycles. Even under extreme conditions (−30 °C and 1 C), the battery still delivers an initial specific capacity of 121 mA h g–1 and shows nearly no degradation over 1000 cycles. Remarkably, the LiFePO4//T-TNO- full cell achieves a specific capacity of 217.39 mA h g–1 at 25 °C and 90.03 mA h g–1 at −30 °C under 0.5 C. This research provides a new perspective for micrometer-sized metal oxide electrode materials development.