A Multi-Phase Niobium Oxide Electrode for High-Power Lithium-Ion Batteries

Niobium oxide-based materials are promising anodes for high-power lithium-ion batteries. The electrochemical performance of these oxides depends sensitively on the crystal and the defect structures. For example, a recent study revealed that the planar defects introduced to the H-phase of Nb2O5 shear structure greatly enhanced the rate capability and structural durability. Our recent study indicates that the M-phase with a tetragonal crystal structure displayed the highest electrochemical performance among all crystalline phases of Nb2O5 studied, due likely to its fast transport of lithium ions and electrons through the ‘block structures’. In this presentation, we will report our findings in the development of a composite electrode composed of a tetragonal and a monoclinic phase of niobium pentoxide with desired defect structures (denoted as d-H,M-Nb2O5), synthesized using a solvothermal process followed by annealing under controlled conditions. Microscopic analysis reveals that the d-H,M-Nb2O5 has NbO6 and NbO4 block structures of both the M-Nb2O5 and the H-Nb2O5. The electrode based on the d-H,M-Nb2O5 exhibits the highest rate capability (142 mAh g-1 at 20 A g-1) and excellent cycling stability (86% capacity retention after 2000 cycles at 6 A g-1) among recently reported niobium pentoxides. Further, detailed crystallographic and defect structures, the physicochemical characteristics, and the long-term cycling behavior will be discussed.