Controlled synthesis of dual-phase carbon-coated Nb2O5/TiNb2O7 porous spheres and their Li-ion storage properties

Dual-phase Nb2O5/TiNb2O7 and carbon-coated Nb2O5/TiNb2O7 porous spheres were synthesized using a simple solvothermal method followed by post-heat treatment. The Nb2O5/TiNb2O7 materials comprised porous spheres with 3-dimensional interconnected microsphere architectures, with a homogeneous dispersion of carbon coating the Nb2O5/TiNb2O7 spheres. As the anode for a Li-ion battery, the dual-phase carbon-coated Nb2O5/TiNb2O7 porous spheres delivered a high gravimetric capacity of >247 mA h g−1 with good cycling performance, as well as a high rate capability. The unique and advantageous characteristics of the dual-phase carbon-coated Nb2O5/TiNb2O7 porous spheres for high performance Li-ion batteries are attributed to the synergistic effects of the porous, two-phase structure of the material. Furthermore, the conductive carbon matrix on the spheres provided facile electron transport and an effective alleviation of mechanical strain during cycling. The high electrochemical performance of the dual-phase carbon-coated Nb2O5/TiNb2O7 porous spheres recommends them as a promising anode material for future Li-ion batteries.