Ultrathin Carbon-Coated Porous TiNb2O7 Nanosheets as Anode Materials for Enhanced Lithium Storage

TiNb2O7 has been considered as a promising anode material for next-generation high power lithium ion batteries for its relatively high theoretical capacity, excellent safety and long cycle life. However, the unsatisfactory electrochemical kinetics resulting from the intrinsic sluggish electron transport and lithium ion diffusion of TiNb2O7 limit its wide application. Morphology controlling and carbon coating are two effective methods for improving the electrochemical performance of electrode materials. Herein, an ultrathin carbon-coated porous TiNb2O7 nanosheet (TNO@C) is successfully fabricated by a simple and effective approach. The distinctive sheet-like porous structure can shorten the transport path of ions/electrons and provide more active sites for electrochemical reaction. The introduction of nanolayer carbon can improve electronic conductivity and increase the specific surface area of the porous TiNb2O7 nanosheets. Based on the above synergistic effect, TiNb2O7@C delivers an initial discharge capacity of 250.6 mAh g−1 under current density of 5C and can be maintained at 206.9 mAh g−1 after 1000 cycles with a capacity retention of 82.6%, both of which are superior to that of pure TiNb2O7. These results well demonstrate that TiNb2O7@C is a promising anode material for lithium ion batteries.