Studies on electrochemical lithium insertion in isostructural titanium niobate and tantalate phases with shear ReO3 structure

TiNb2O7 and TiTa2O7 phases are synthesized by solid-state reaction method and are investigated for electrochemical Li insertion/extraction. The electrochemical insertion of Li in these phases is characterized by both solid solution and two-phase regimes. The structure is stable toward Li insertion/extraction. The first cycle discharge capacity values are 307 mAh g−1 and 215 mAh g−1 in the voltage range of 3.0–1.0 V for TiNb2O7 and TiTa2O7 phases, respectively. The discharge capacities of TiNb2O7 and TiTa2O7 are 212 mAh g−1 and 100 mAh g−1, respectively, after 20 cycles.