Ordered-mesoporous Nb₂O₅/carbon composite as a sodium insertion material

The present work introduces a new intercalation host for the Na ions, Nb₂O₅, and proposes that a mesoporous Nb₂O₅/carbon composite can function as a promising sodium insertion material. The highly ordered mesoporous Nb₂O₅/carbon electrode, synthesized using a block copolymer-assisted one-pot method, demonstrated not only a stable cycle life, but also outstanding rate capability. The excellent Na storage properties of the Nb₂O₅/carbon electrode were due to the uniquely ordered mesoporous nanostructure and in situ carbon formation whose configuration provided a large electrode-electrolyte interface area and enhanced Na ion and electron transport. Ex situ analyses revealed that Nb₂O₅ stores Na ions through Na de/intercalation reactions combined with surface capacitive reactions, after the activation process during the first sodiation.