Cu0.02Ti0.94Nb2.04O7: An advanced anode material for lithium-ion batteries of electric vehicles

To explore advanced anode materials for lithium-ion batteries of electric vehicles, Cu2+/Nb5+ co-doped TiNb2O7 is studied. Cu0.02Ti0.94Nb2.04O7 is successfully fabricated using a facile solid-state reaction. X-ray diffraction analyses combined with Rietveld refinements demonstrate that the trace Cu2+/Nb5+ co-doping does not destroy the shear ReO3 crystal structure of TiNb2O7 but increases the lattice parameters and unit cell volume. Specific surface area tests and scanning electron microscopy images reveal a smaller average particle size in Cu0.02Ti0.94Nb2.04O7. Due to the increased unit cell volume and free 3d electrons in Cu2+ ions, the Li+-ion diffusion coefficient and electronic conductivity of Cu0.02Ti0.94Nb2.04O7 are respectively enhanced by 14.8 times and at least 220 times. Consequently, Cu0.02Ti0.94Nb2.04O7 exhibits advanced electrochemical properties in terms of specific capacity, rate capability and cyclic stability. At 0.1 C, it delivers a large first-cycle discharge/charge capacity of 346/315 mAh g(-1). At 10 C, it still provides a large capacity of 182 mAh g(-1) with tiny loss of only 1.2% over 1000 cycles. In sharp contrast, TiNb2O7 shows a small capacity of only 90 mAh g(-1) and large loss of 59.8%. Therefore, Cu0.02Ti0.94Nb2.04O7 possesses great potential for the application in lithium-ion batteries for electric vehicles. (C) 2016 Elsevier B.V. All rights reserved.