Intercalating Ti₂ Nb₁₄ O₃₉ Anode Materials for Fast-Charging, High-Capacity and Safe Lithium-Ion Batteries

Ti-Nb-O binary oxide materials represent a family of promising intercalating anode materials for lithium-ion batteries. In additional to their excellent capacities (388-402 mAh g^-1 ), these materials show excellent safety characteristics, such as an operating potential above the lithium plating voltage and minimal volume change. Herein, this study reports a new member in the Ti-Nb-O family, Ti₂ Nb₁₄ O₃₉ , as an advanced anode material. Ti₂ Nb₁₄ O₃₉ porous spheres (Ti₂ Nb₁₄ O₃₉ -S) exhibit a defective shear ReO₃ crystal structure with a large unit cell volume and a large amount of cation vacancies (0.85% vs all cation sites). These morphological and structural characteristics allow for short electron/Li⁺ -ion transport length and fast Li⁺ -ion diffusivity. Consequently, the Ti₂ Nb₁₄ O₃₉ -S material delivers significant pseudocapacitive behavior and excellent electrochemical performances, including high reversible capacity (326 mAh g^-1 at 0.1 C), high first-cycle Coulombic efficiency (87.5%), safe working potential (1.67 V vs Li/Li⁺ ), outstanding rate capability (223 mAh g^-1 at 40 C) and durable cycling stability (only 0.032% capacity loss per cycle over 200 cycles at 10 C). These impressive results clearly demonstrate that Ti₂ Nb₁₄ O₃₉ -S can be a promising anode material for fast-charging, high capacity, safe and stable lithium-ion batteries.