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.