Ta-doped Nb₂O₅ with enhanced performance for lithium-ion batteries

Micrometer-sized niobium pentoxides (Nb₂O₅), with inherent safety and capability for fast lithium insertion/deinsertion, have been regarded as promising anodes for high-volumetric-energy-density lithium-ion batteries (LIBs). However, they suffer from structural instability and capacity fading in practical applications. To address these issues, we adopt a Ta doping strategy to change the chemical composition of Nb₂O₅. When utilized as anodes for LIBs, the optimized Ta-doped niobium pentoxides (Ta_0.2Nb₂O_5.5) deliver a specific capacity of 86 mA h g^-1 at a high current density of 20 A g^-1 (251 mA h g^-1 at 0.1 A g^-1) and a remarkable capacity retention of 64% over 1000 cycles at 8 A g^-1, significantly exceeding those of the original Nb₂O₅. Moreover, when coupled with the LiCoO₂ (LCO) cathode, the full cell (LCO//Ta_0.2Nb₂O_5.5) delivers specific capacities of around 250 and 141 mA h g^-1 (56.4% retention) at 0.1 and 6 A g^-1, respectively, and exhibits a 67.5% capacity retention after 200 cycles at 1 A g^-1, both markedly higher than those of the undoped counterpart. Through structural and electrochemical characterization studies, we identify that Ta doping improves lattice stability, facilitates charge transfer and thus contributes to performance improvement at high current densities during long-term cycling tests. Our work exemplifies a new strategy for improving the performance of Nb-based anodes and can be widely extended to the design of other high-performance electrode materials.