Porosity-Controlled TiNb2O7 Microspheres with Partial Nitridation as A Practical Negative Electrode for High-Power Lithium-Ion Batteries

Titanium niobium oxide (TiNb2O7) has been recognized as a promising anode material for lithium-ion batteries (LIBs) in view of its potential to operate at high rates with improved safety and high theoretical capacity of 387 mAh g(-1). However, it suffers from poor Li+ ion diffusivity and low electronic conductivity originated from its wide band gap energy (E-g > 2 eV). Here, porous TiNb2O7 microspheres (PTNO MSs) are prepared via a facile solvothermal reaction. PTNO MSs have a particle size of approximate to 1.2 mu m and controllable pore sizes in the range of 5-35 nm. Ammonia gas nitridation treatment is conducted on PTNO MSs to introduce conducting Ti1-xNbxN layer on the surface and form nitridated PTNO (NPTNO) MSs. The porous structure and conducting Ti1-xNbxN layer enhance the transport kinetics associated with Li+ ions and electrons, which leads to significant improvement in electrochemical performance. As a result, the NPTNO electrode shows a high discharge capacity of approximate to 265 mAh g(-1), remarkable rate capability (approximate to 143 mAh g(-1) at 100 C) and durable long-term cyclability (approximate to 91% capacity retention over 1000 cycles at 5 C). These results demonstrate the great potential of TiNb2O7 as a practical high-rate anode material for LIBs.