Niobium pentoxide based materials for high rate rechargeable electrochemical energy storage

The demand for high rate energy storage systems is continuously increasing driven by portable electronics, hybrid/electric vehicles and the need for balancing the smart grid. Accordingly, Nb₂O₅ based materials have gained great attention because of their fast cation intercalation faradaic charge storage that endows them with high rate energy storage performance. In this review, we describe the crystalline features of the five main phases of Nb₂O₅ and analyze their specific electrochemical characteristics with an emphasis on the intrinsic ion intercalation pseudocapacitive behavior of T-Nb₂O₅. The charge storage mechanisms, electrochemical performance and state-of-the-art characterization techniques for Nb₂O₅ anodes are summarized. Next, we review recent progress in developing various types of Nb₂O₅ based fast charging electrode materials, including Nb₂O₅ based mixed metal oxides and composites. Finally, we highlight the major challenges for Nb₂O₅ based materials in the realm of high rate rechargeable energy storage and provide perspectives for future research.