Macroporous Nanostructured Nb₂O₅ with Surface Nb⁴⁺ for Enhanced Lithium Ion Storage Properties

Abstract Macroporous Nb₂O₅ (MP‐Nb₂O₅) has been synthesized using dispersed polystyrene microspheres (PS) as template followed by annealing in air. The structural characterization showed that the diameters of the macropores are around 200 nm and the average particle size of the composition is 20–50 nm. XPS revealed the presence of low valence Nb⁴⁺ and oxygen vacancies on the surface of the resulting product introduced during the pyrolysis of PS. Such a unique combination of macroporous nanostructure and tetravalent niobium ions enables the electrode with superior lithium ion insertion properties, such as high specific capacity (≈190 mA h g⁻¹ at 0.5C) and rate capability. Even at a current density of 1.6 A g⁻¹, an average capacity of 129.2 mA h g⁻¹ can still be obtained. These findings demonstrate MP‐Nb₂O₅ is a promising candidate for high‐rate lithium ion storage applications.