A facile nitridation method to improve the rate capability of TiO2 for lithium-ion batteries

It is demonstrated that the rate capacities of TiO2 anatase nanoparticles can be improved substantially by annealing in NH3 at 450-500 °C. At a high nominal rate of 25C, the average discharge capacity of specimens annealed in NH3 at 450 °C for 7 h is more than double of that of the controlled specimens annealed in dry air under the same heat treatment condition. A critical comparison with literature shows that this simple and cost-effective low-temperature nitridation process can achieve high-rate capacities that are better than those reported in prior comparable studies. The enhanced high-rate capacities are attributed to moderate surface nitridation with less-disordered nitridated regions, which may enhance the surface electronic conductivity without forming discrete, nanoscale, surface amorphous films to block the lithium transport. Surface nitridation was confirmed by XPS measurements.