Identification of Phase Control of Carbon-Confined Nb2O5 Nanoparticles toward High-Performance Lithium Storage

Niobium pentoxides (Nb2O5) have attracted extensive interest for ultrafast lithium-ion batteries due to their impressive rate/capacity performance and high safety as intercalation anodes. However, the intrinsic insulating properties and unrevealed mechanisms of complex phases limit their further applications. Here, a facile and efficient method is developed to construct three typical carbon-confined Nb2O5 (TT-Nb2O5@C, T-Nb2O5@C, and H-Nb2O5@C) nanoparticles via a mismatched coordination reaction during the solvothermal process and subsequent controlled heat treatment, and different phase effects are investigated on their lithium storage properties on the basis of both experimental and computational approaches. The thin carbon coating and nanoscale size can endow Nb2O5 with a high surface area, high conductivity, and short diffusion length. As a proof-of-concept application, when employed as LIB anode materials, the resulting T-Nb2O5@C nanoparticles display higher rate capability and better cycling stability as compared with TT-Nb2O5@C and H-Nb2O5@C nanoparticles. Furthermore, a synergistic effect is investigated and demonstrated between fast diffusion pathways and stable hosts in T-Nb2O5 for ultrafast and stable lithium storage, based on crystal structure analysis, in situ X-ray diffraction analysis, and density functional theoretical calculations. Therefore, the proposed synthetic strategy and obtained deep insights will stimulate the development of Nb2O5 for ultrafast and long-life LIBs.