Carbon-coated TiNb2O7 microspheres with partial nitridation for high-performance lithium storage

TiNb 2 O 7 has been applied to lithium-ion batteries owing to its large capacity and inherent safety, but suffers from its poor rate capability. Here, TiNb 2 O 7 is modified through a combination of crystal-structure modification and conductive-phase coating, and C–NH 3 –TiNb 2 O 7 with Ti 2 Nb[Formula: see text]O[Formula: see text]-type TiNb 2 O 7 and Ti[Formula: see text][Formula: see text]Nb[Formula: see text]N/carbon double coatings is successfully synthesized. The unique Ti 2 Nb[Formula: see text]O[Formula: see text]-type structure of TiNb 2 O 7 owns a large interlayer spacing, leading to fast Li[Formula: see text] diffusivity and remarkable intercalation-pseudocapacitive behavior. The conductive Ti[Formula: see text][Formula: see text]Nb[Formula: see text]N/carbon coatings result in good electrical conduction among the TiNb 2 O 7 microspheres. Consequently, C–NH 3 –TiNb 2 O 7 exhibits excellent rate capability of TiNb 2 O 7 (large capacity percentage of 73.9% at 5C versus 0.5C). Besides the fast electrochemical kinetics, C–NH 3 –TiNb 2 O 7 further exhibits large reversible capacities (237 mAh g[Formula: see text]at 0.1C and 146 mAh g[Formula: see text]at 5C) and outstanding cyclability (93.1% capacity retention after 500 cycles at 5C). These desirable electrochemical properties fully demonstrate that the C–NH 3 –TiNb 2 O 7 anode material can be suitable for high-performance Li[Formula: see text]-storage.