Intercalating Ti2Nb14O39 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, Ti 2 Nb 14 O 39 , as an advanced anode material. Ti 2 Nb 14 O 39 porous spheres (Ti 2 Nb 14 O 39 -S) exhibit a defective shear ReO 3 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 Ti 2 Nb 14 O 39 -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 Ti 2 Nb 14 O 39 -S can be a promising anode material for fast-charging, high capacity, safe and stable lithium-ion batteries.