Nano-TiNb2O7/carbon nanotubes composite anode for enhanced lithium-ion storage

Abstract Although with a large capacity, TiNb2O7 as an anode material of lithium-ion batteries suffers from a poor rate capability. To solve this challenge, nano-TiNb2O7 and its carbon nanotube (CNT) nanocomposites were prepared by direct hydrolysis of TiNb2O7/CNTs suspension followed by calcination in air and N2, respectively. The TiNb2O7 nanoparticles in the composites have a Ti2Nb10O29-type crystal structure with O2− vacancies and lower-valence cations, leading to improved Li+-ion diffusion coefficient and increased electronic conductivity in TiNb2O7. The evenly distributed CNTs have good contact with the TiNb2O7 particles, thereby reducing their particle sizes and improving the electrical conduction. As a result of these improvements, the nanocomposites present outstanding electrochemical performances. For example, it delivers a large reversible capacity (346 mAh g−1 at 0.1 C) and a prominent rate capability (still 163 mAh g−1 at the ultra-large current rate of 30 C). Exceptional cyclic stability is also demonstrated with over 100 cycles at 10 C with large capacity retention of 97.6%. These results reveal that the nano-TiNb2O7/CNTs composites can be a promising anode material for lithium-ion batteries of electric vehicles.